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Cover design by Nancy Polend, 1991 
Field Studies of Radon in Rocks, 

Soils, and Water 

LINDA C.S. GUNDERSEN and RICHARD B. WANTY, 

Editors 

U.S. Geological Survey research on the geology, geophysics, 

and geochemistry of radon in rocks, soils, and water 

U.S. GEOLOGICAL SURVEY BULLETIN 1971 
U.S. DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, Jr., Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

Any use of trade, product, or firm names in this publication is for descriptive purposes 

only and does not imply endorsement by the U.S. Government 

UNITED STATES GOVERNMENT PRINTING OFFICE: 1991 

For sale by the Superintendent of Documents 

U.S. Government Printing Office 

Washington, DC 20402 

Library of Congress Cataloging in Publication Data 

Field studies of radon in rocks, soils, and water I Linda C.S. Gundersen and 

Richard B. Wanty, editors. 

p. em. - (U.S. Geological Survey bulletin ; 1971) 

Includes bibliographical references. 

Supt. of Docs. no.: I 19.3:1971 

1. Radon-Measurement. 2. Radon-Environmental aspects-Measurement. 3. Rocks-Analysis. 4. Soils, Radioactive substances in-Measurement. 5. Radioactive pollution of water-Measurement. 6. Water, 

Underground-Analysis. I. Gundersen, L.C.S. II. Wanty, Richard B. 

Ill. Series. 

QC796.R6F54 1991 

553'.97-dc20 91-13712 

CIP 
PREFACE 

This volume contains 24 papers of geologic and hydrogeologic research on 

radon-222, a naturally occurring radioactive gas (hereafter referred to as radon). In 

1984, R.C. Smith II and co-workers documented the most severe indoor radon problem to date, which was in Colebrookdale Township near Boyertown, Pa. (Pennsylvania Geology, 1987, v. 18, p. 1-7). A residence was found to contain 2,500 pCi/L 

(picocuries per liter) of radon. The Environmental Protection Agency's current action 

level for radon mitigation of a home is 4 pCi/L. At 4 pCi/L, the chance of lung cancer 

from a lifetime exposure, for populations of smokers and nonsmokers, is 1 to 3 persons out of 100. The discovery of high indoor radon levels near Boyertown and in 

several other parts of the United States prompted nationwide concern and the initiation 

of federal programs to assess and understand the problem. Despite the obvious geologic controls on concentrations of radon in soil gases, relatively little research has 

focused on geologic aspects of the radon problem. These factors are important for our 

understanding of the natural occurrence of radon in soil gases and for the eventual prediction of areas likely to have high radon concentrations. Radon, in addition to being 

found in soil gas, can also be present in ground water. A ground-water supply 

enriched in radon is possibly a significant source of radon in indoor air. Inside a 

home, when water is agitated, such as when a faucet is turned on, radon can be 

released from the water into the air. Uranium and radium may also be present in 

ground waters in concentrations that may prove harmful for human consumption. High 

amounts of radium and radon have been known for several years to exist in ground 

waters in New England, but their occurrence in domestic well supplies in other parts 

of the country had not been tested extensively or understood. Research in the past 5 

years by the U.S. Geological Survey on these geological and hydrogeological issues 

has significantly increased our understanding of radon and its occurrence. Compiled 

in this volume are field studies relating ways to measure, assess, and understand radon 

in homes and in water. The papers are of a technical nature and are written for the 

scientific audience. 

Radon-222 is generated from the decay of uranium-238, which is present naturally in varying concentrations in all rocks and soils. Radon-222 is the longest lived 

isotope of radon; it is odorless and colorless in the concentrations observed in homes 

and so is not an obvious problem in the air in homes. Radium-226 is the immediate 

parent isotope of radon-222. Figure 73 on page 184 illustrates the uranium-238 decay 

chain. The formation of radon-222 and its daughter products, polonium-218 and 

polonium-214, is shown. Radon in air can be inhaled into the lungs, and the polonium 

isotopes can be deposited in lung tissue as the radon decays. Polonium atoms adhere 

to particulates in air, which when breathed in, may also deposit them in the lungs. The 

polonium isotopes emit alpha particles, which cause lung damage and may be responsible for lung-cancer deaths of 5,000 to 20,000 U.S. citizens a year (A Citizen's 

Guide to Radon, Environmental Protection Agency, 1986, OPA-86-004, 14 p.). 

The first half of this volume focuses on rocks and soils, the principle sources of 

indoor radon. This half is divided into three sections, the first of which addresses ways 

of measuring radon in the ground and also the problems associated with measurement. 

Tanner describes "Methods of Characterization of Ground for Assessment of Indoor 

Radon Potential at a Site." In this report, soil characteristics and their effect on radon 

mobility and measurement are discussed in detail. Recommendations for avoiding inacPreface Ill 
IV Preface 

curate measurements and suggestions for the best type of measurement instruments are 

made. "Simple Techniques for Soil-Gas and Water Sampling for Radon Analyses," by 

Reimer, illustrates a simple sampling technique for soil air and for radon in ground 

water that is accessible to most scientists interested in reconnaissance and field techniques of measuring radon. In a paper at the end of this section, Reimer discusses 

"Derivation of Radon Migration Rates in the Surficial Environment by Use of Helium 

Injection Experiments." In this study he uses helium injection into the ground to determine radon migration rates and direction within deformed bedrock. A long-term study 

on the effects of climate on soil radon is presented in "A Preliminary Evaluation of 

Environmental Factors Influencing Day-to-Day and Seasonal Soil-Gas Radon Concentrations," by Asher-Bolinder, Owen, and Schumann. They found that pedologic and 

meteorologic conditions interact to cause both day-to-day and seasonal variations in 

soil radon. 

The second section, which concerns geologic field studies of radon, presents 

specific case histories. "Radon in Sheared Metamorphic and Igneous Rocks," by 

Gundersen, describes four areas of the Appalachians, including the well known Boyertown site, where severely elevated levels of indoor radon are found associated with 

sheared bedrock. The paper analyzes the geologic processes that contribute to some of 

the highest indoor radon levels found in the United States. Agard and Gundersen focus 

on "The Geology and Geochemistry of Soils in Boyertown and Easton, Pennsylvania." 

Soil characteristics are examined in two areas having very high indoor radon levels to 

understand which soil parameters control radon migration and concentration. Henry, 

Kaeding, and Monteverde present "Radon in Soil Gas and Gamma-Ray Activity of 

Rocks and Soils at the Mulligan Quarry, Clinton, New Jersey." Soil radon measurements and gamma measurements are compared for an area of carbonate rocks that are 

sheared and mineralized with uranium. A practical demonstration of radon use in predicting another geologic hazard is given in "Radon in Soil Gas Along Active Faults in 

Central California," by King, Walkingstick, and Basler. Soil radon was monitored 

from 1975 to 1985 along a 380-km segment of the San Andreas fault, and correlations 

with large local earthquakes are shown. "Radon Emanation from Uranium Mill Tailings," by Landa, examines the radon emanation of mine tailings with reference to the 

original ore. He finds that, although 90 percent of the uranium is generally extracted 

during the milling processes, most of the daughter-product activity remains with the 

tailings. 

The third section highlights different techniques for assessment of radon potential. Duval describes the "Use of Aerial Gamma-Ray Data to Estimate Relative 

Amounts of Radon in Soil Gas." He shows how aerial gamma-ray data can be used to 

assess regions for radon potential and the importance of geology in utilizing the geophysical data. "Regional Radon Characterizations," by Peake and Schumann, demonstrates how indoor radon screening data can be combined predictively with soils, geologic, and radiometric data to indicate areas of high radon potential. Kentucky is used 

as an example of a State assessment. The final paper of the first half, by Reimer, 

Gundersen, Szarzi, and Been, describes a "Reconnaissance Approach to Using Geology and Soil-Gas Radon Concentrations for Making Rapid and Preliminary Estimates 

of Indoor Radon Potential." Simple field techniques for assessment of radon potential 

are evaluated by use of soil radon collected along a transect perpendicular to strike in 

the Maryland coastal plain. 

The second half of the Bulletin, "Studies of Radon in Water," features geochemical and hydrologic studies of ground waters. The first paper in the introductory section, "A Review of the Chemical Processes Affecting the Mobility of Radionuclides in 

Natural Waters, with Applications," by Wanty and Schoen, provides a primer on the 

aqueous geochemistry of radionuclides in the context of geology and the radon problem. This paper also gives a review of the health effects of radionuclides in water. In 

the second introductory paper, Paulsen presents an extensive overview in "Radio-
nuclides in Ground Water, Rock, Soil, and Indoor Air of the Northeastern United 

States and Southeastern Canada-A Literature Review and Summary of Data." The 

report briefly summarizes major investigations of the occurrence of radionuclides in 

the New England States, New York, and southern Ontario since the 1950's. 

The second section addresses techniques for measuring radon in ground waters. 

Yang describes "Sampling and Analyses of Dissolved Radon-222 in Water by the 

De-Emanation Method." In this paper he discusses the advantages and disadvantages 

of the direct de-emanation and alpha-scintillation counting method and finds it to have 

better precision in the lower concentration ranges than any other method currently 

available. "A Comparison of Two Techniques for Radon-222 Measurement in Water 

Samples" is given by Mullin and Wanty. In testing the reproducibility and values of 

radon concentration measured by liquid scintillation and by a technique developed by 

Reimer (this volume), the authors found the results to be in moderately good agreement. Although it has the advantage of producing results within a matter of minutes, 

the Reimer technique shows poor consistence in comparison with the liquid scintillation method because in the Reimer technique radon is lost if samples are stored for a 

prolonged period. 

The third section contains eight papers featuring specific field studies of radon in 

surface and ground waters throughout the United States. Lee and Hollyday present 

"Use of Radon Measurements in Carters Creek, Maury County, Tennessee, To Determine Location and Magnitude of Ground-Water Seepage." By measuring the activity 

of radon-222 in streamflow, the authors found the location and calculated the contribution of ground-water seepage to the total flow in the creek. Szabo and Zapecza examine "Geologic and Geochemical Factors Controlling Uranium, Radium-226, and 

Radon-222 in Ground Water, Newark Basin, New Jersey." They found that groundwater radionuclide levels in the Newark basin are highest in the Passaic, Lockatong, 

and Stockton Formations. A number of samples collected exceed the Environmental 

Protection Agency's maximum contaminant levels and are associated with uranium 

enrichment in the bedrock. In the report "Radium-226, Radium-228, and Radon-222 in 

Ground Water in the Chickies Quartzite, Southeastern Pennsylvania," by Cecil, 

Senior, and Vogel, an anomalously elevated occurrence of radium in domestic well 

water is investigated. They found that pH may be used to predict elevated radium concentrations and that all samples with pH below 4. 7 contained concentrations of total 

radium that exceeded the Environmental Protection Agency's maximum contaminant 

level. Their paper also documents the importance of measuring all isotopes of radium 

as opposed to the more common practice of ignoring radium-228 unless radium-226 is 

above certain threshold levels. "Radon in Ground Water of the Carson Valley, WestCentral Nevada" is the subject of the study by Lico and Rowe. The authors have 

determined both the sedimentologic and geochemical controls on the highly variable 

distribution of radon-222 within the valley. However, they believe the principle source 

of the radon is derived from the Carson Range. High levels of radon in domestic wells 

in Boyertown and eastern Pennsylvania is the subject of the paper "Geochemistry of 

Ground Water and Radionuclide Mobility in Two Areas of the Reading Prong, Eastern 

Pennsylvania," by Wanty, Briggs, and Gundersen. The authors found that aquifer rock 

type appears to be the dominant factor determining the radon-222 potential of ground 

water in the two sites examined. Gray and Webb describe "Radionuclides in the 

Puerco and Lower Little Colorado River Basins, New Mexico and Arizona, Before 

1987." Both naturally occurring radionuclides and radionuclides from uranium mine 

tailings contribute to excessive levels of radioactivity in surface and ground waters in 

the river basins examined. In "Uranium, Radium, and Radon in Deeply Buried Sediments of the U.S. Gulf Coast," Kraemer describes the geochemistry and secular equilibrium of uranium, radium, and radon in water, rock, and gases of buried coastal 

plain sediments. The final paper of the Bulletin is "Radium, Helium, and Other Gases 

in Shallow Ground Waters of Uraniferous Holocene Alluvium, Flodelle Creek, Stevens 

Preface V 
VI Preface 

County, Northeast Washington," by Otton and Reimer. The authors use various gas 

species including radon, helium, oxygen, carbon dioxide, and methane to examine 

radionuclide source, ground-water flow, and geochemistry in a drainage basin. 

The editors would like to especially thank John Watson for his diligence, humor, 

patience, and excellent technical editing during the compilation of this Bulletin. 

Linda C. S. Gundersen 

Richard B. W anty 
CONTENTS 

Preface III 

Part 1: Studies of Radon in Rocks and Soil 

Section 1: Techniques for Measuring Radon in Soil 

Methods of Characterization of Ground for Assessment of Indoor Radon Potential at a 

Site, by Allan B. Tanner 1 

Abstract 1 

Introduction 1 

The Emanation Process 2 

Permeability 2 

Diffusion 4 

Models of the Soil Regime Near a House 4 

Radon Measurement Methods 7 

Short-Term Meteorological Effects 9 

Seasonal Effects 9 

Acknowledgments 10 

References Cited 11 

Appendix A. Derivation of the Radon Availability Number (RAN) 14 

Appendix B. Derivation of the Relations among Permeability, Flow Rate, and 

Pressures in the Hemispherical Geometry of the Sampling Hole 15 

Appendix C. Derivation of Relations among Permeability, Flow Rate, and Pressures 

for Radial Flow into a Cylindrical Sampling Hole 17 

Simple Techniques for Soil-Gas and Water Sampling for Radon Analysis, 

by G.M. Reimer 19 

Abstract 19 

Introduction 19 

Soil-Gas Sampling Technique 19 

Water Sample Collecting Technique 21 

References Cited 22 

A Preliminary Evaluation of Environmental Factors Influencing Day-to-Day and 

Seasonal Soil-Gas Radon Concentrations, by Sigrid Asher-Bolinder, Douglass E. 

Owen, and R. Randall Schumann 23 

Abstract 23 

Introduction 23 

The Importance of Time Scales 23 

Previous Studies 24 

Site Description 25 

Methods 26 

Discussion 26 

Summary 30 

References Cited 30 

Contents VII 
VIII Contents 

Derivation of Radon Migration Rates in the Surficial Environment by Use of Helium 

Injection Experiments, by G.M. Reimer 33 

Abstract 33 

Introduction 33 

Study Setting 33 

Results 34 

Discussion 34 

Conclusions 37 

Acknowledgments 38 

References Cited 38 

Section 2: Geologic Field Studies 

Radon in Sheared Metamorphic and Igneous Rocks, by Linda C.S. Gundersen 39 

Abstract 39 

Introduction 39 

Methods 40 

Boyertown, Pennsylvania 40 

Brookneal Zone, Virginia 42 

Glen Gardner, New Jersey 44 

Montgomery County, Maryland 45 

Discussion and Conclusions 48 

Acknowledgments 49 

References Cited 49 

The Geology and Geochemistry of Soils in Boyertown and Easton, Pennsylvania, 

by Sherry S. Agard and Linda C.S. Gundersen, 51 

Abstract 51 

Introduction 51 

Geology of Boyertown and Easton 51 

Definition and General Properties of Soils 52 

Soils of Boyertown and Easton 55 

Radon Emanation of Soils 57 

Discussion 58 

Summary and Conclusions 61 

References Cited 62 

Radon in Soil Gas and Gamma-Ray Activity of Rocks and Soils at the Mulligan 

Quarry, Clinton, New Jersey, by Mitchell E. Henry, Margret E. Kaeding, and 

Donald Monteverde 65 

Abstract 65 

Introduction 65 

Geologic Setting 65 

General Uranium Distribution 66 

Methods of Study 67 

Results and Discussion 67 

Summary 69 

References Cited 7 5 
Radon in Soil Gas Along Active Faults in Central California, by Chi-Yu King, 

Calvin Walkingstick, and David Basler 77 

Abstract 77 

Introduction 77 

Monitoring Sites 77 

Monitoring Technique 77 

Discussion 77 

Acknowledgments 78 

References Cited 78 

Radon Emanation from Uranium Mill Tailings, by Edward R. Landa 145 

Abstract 145 

Introduction 145 

Radium-226 Contents and Radon Emanation Coefficients of Particle-Size Fractions of 

Alkaline, Acid, and Mixed Uranium Mill Tailings 145 

Influence of Ore Type and Milling Process on Radon-222 Emanation Coefficients of 

Uranium Mill Tailings 150 

References Cited 153 

Section 3: Estimating Radon Potential 

Use of Aerial Gamma-Ray Data to Estimate Relative Amounts of Radon in Soil Gas, 

by Joseph S. Duval 155 

Abstract 155 

Introduction 155 

Aerial Gamma-Ray Surveys and Radon 155 

Distribution of Radium in New Jersey 156 

Indoor Radon in New Jersey 157 

Discussion 157 

Radon Hazard Assessment 159 

Conclusions 161 

References Cited 161 

Regional Radon Characterizations, by R. Thomas Peake and R. Randall 

Schumann 163 

Abstract 163 

Introduction 163 

Factors Controlling Radon Concentrations in Soils 163 

Driving Forces and Basement Versus Nonbasement Homes 164 

Assessment Scales 164 

Assessment Techniques 165 

Correlations between Equivalent Uranium and Indoor Radon Data 167 

A Case Study 168 

Discussion 171 

Summary and Conclusions 174 

References Cited 17 4 

Contents IX 
X Contents 

Reconnaissance Approach to Using Geology and Soil-Gas Radon Concentrations for 

Making Rapid and Preliminary Estimates of Indoor Radon Potential, 

by G.M. Reimer, Linda C.S. Gundersen, S.L. Szarzi, and J.M. Been 177 

Abstract 177 

Introduction 177 

Geologic Setting 177 

Analytical Technique 177 

Data and Discussion 178 

Conclusions 179 

Acknowledgments 179 

References Cited 181 

Part 2: Studies of Radon in Water 

Section 1: Introduction 

A Review of the Chemical Processes Affecting the Mobility of Radionuclides in 

Natural Waters, with Applications, by Richard B. Wanty and Robert Schoen 183 

Abstract 183 

Introduction 183 

Effects of Natural Radionuclides on Health 185 

Inorganic Chemistry of Radon and its Parent Elements 186 

Summary of Selected Studies 189 

Summary and Conclusions 191 

References Cited 192 

Radionuclides in Ground Water, Rock and Soil, and Indoor Air of the Northeastern 

United States and Southeastern Canada-A Literature Review and Summary of 

Data, by Robert T. Paulsen 195 

Abstract 195 

Introduction 195 

Historical Perspective 195 

Maine 200 

New Hampshire 203 

Vermont 206 

Massachusetts 208 

Rhode Island 208 

Connecticut 211 

New York 213 

Canada-Southern Ontario 217 

Acknowledgments 219 

References Cited 220 

Section 2: Techniques for Measuring Radon in Water 

Sampling and Analysis of Dissolved Radon-222 in Water by the De-emanation 

Method, by In Che Yang 227 

Abstract 227 

Introduction 227 
Experimental Methods 227 

Results and Discussion 229 

Summary 230 

References Cited 230 

A Comparison of Two Techniques for Radon-222 Measurement in Water Samples, 

by Ann Mullin and Richard B. Wanty 231 

Abstract 231 

Introduction 231 

Methods 231 

Results and Discussion 232 

Conclusions 234 

References 235 

Section 3: Field Studies of Radon in Surface and Ground Waters 

Use of Radon Measurements in Carters Creek, Maury County, Tennessee, 

to Determine Location and Magnitude of Ground-Water Seepage, 

by Roger W. Lee and Este F. Hollyday 237 

Abstract 237 

Introduction 237 

Radon Cycling in Ground-Water and Surface-Water Systems 237 

Characterization of Base Flow 240 

Application to Carters Creek, Tennessee 240 

Methods 240 

Results and Discussion 241 

References Cited 242 

Geologic and Geochemical Factors Controlling Uranium, Radium-226, and 

Radon-222 in Ground Water, Newark Basin, New Jersey, 

by Zoltan Szabo and Otto S. Zapecza 243 

Abstract 243 

Introduction 243 

Sources of Uranium 247 

Sampling and Analysis 247 

Radionuclide Activities and Distribution in Ground Water 249 

Determination of Sources of Radioactivity by Borehole Geophysics and Test-Core 

Analysis 251 

Ground-Water Geochemistry of Uranium and Radium in the Newark Basin 256 

Controls on Dissolved Radon-222 Concentration in the Newark Basin 262 

Conclusions 263 

Acknowledgments 264 

References Cited 264 

Radium-226, Radium-228, and Radon-222 in Ground Water of the Chickies Quartzite, 

Southeastern Pennsylvania, by L. DeWayne Cecil, Lisa A. Senior, and 

Karen L. Vogel 267 

Abstract 267 

Introduction 267 

Contents XI 
XII Contents 

Geohydrologic Setting 268 

Data Collection and Analysis 269 

Radium and Radon in Ground Water 273 

Conclusions 276 

References Cited 276 

Radon in Ground Water of Carson Valley, West-Central Nevada, by MichaelS. Lico 

and Timothy G. Rowe 279 

Abstract 279 

Introduction 279 

Geohydrologic Setting 280 

Distribution of Radon in the Ground Water 283 

Geologic and Geochemical Controls on Radon in the Ground Water 285 

Summary 287 

References Cited 288 

Geochemistry of Ground Water and Radionuclide Mobility in Two Areas of the 

Reading Prong, Eastern Pennsylvania, by Richard B. Wanty, Paul H. Briggs, and 

Linda C. S. Gundersen 289 

Abstract 289 

Introduction 289 

Geology and Ground-Water Chemistry of the Study Areas 289 

Methods of Sampling, Analysis, and Data Treatment 290 

Results and Discussion 291 

Conclusions 293 

Acknowledgment 295 

References Cited 296 

Radionuclides in the Puerco and Lower Little Colorado River Basins, New Mexico 

and Arizona, Before 1987, by John R. Gray and Robert H. Webb 297 

Abstract 297 

Introduction 297 

Background 297 

Radionuclide Activities at U.S. Geological Survey Gaging Stations 303 

Characterization of Quality of Ground Water 305 

Areal and Temporal Variations in Water Quality 307 

Processes Controlling the Movement of Radionuclides 307 

Discussion 309 

References Cited 310 

Uranium, Radium, and Radon in Deeply Buried Sediments of the U.S. Gulf Coast, 

by Thomas F. Kraemer 313 

Abstract 313 

Introduction 313 

Geologic Setting 313 

Uranium 313 

Radium 315 

Radon 316 

Conclusions 317 

References Cited 318 
Radon, Helium, and Other Gases in Shallow Ground Waters of Uraniferous Holocene 

Alluvium, Flodelle Creek, Stevens County, Northeast Washington, 

by James K. Otton and G.M. Reimer 319 

Abstract 319 

Introduction 319 

Chemistry of Radon and Helium 320 

Site Description 321 

Methods 325 

Results and Discussion 326 

Conclusions 332 

Appendix A. Calculation of Expected Radon Yield 333 

References Cited 333 

FIGURES 

1. Schematic diagrams showing modes of operation of the three-packer soil 

probe 3 

2. Scheme of the model used to define radon availability 5 

3. Schematic diagram of the apparatus for extracting and measuring radon 

concentration of soil gas and measuring flow rate and driving pressures for 

permeability calculation 6 

4. Graphs showing comparisons of reported indoor radon concentrations with 

concentrations of radon in soil gas from boreholes near 10 houses and with 

radon availability numbers 7 

5. Curves showing the error in estimation of radon concentration by passive 

detectors 9 

6. Curves showing the calculated ratio of the radon concentration in the gas 

phase of the pore space in soil to the average radon concentration in the pore 

space as a function of pore water fraction for 273 K, 283 K, and 293 K 10 

7. Schematic drawing of soil-gas probe 20 

8. Drawing of water sampling container 21 

9. Photograph showing the study site at the Denver Federal Center 25 

10. Graphs of weather parameters and radon in soil gas at the Denver Federal 

Center study site 27 

11. Sketch map showing location of injection probe and the monitoring probes for 

the helium migration study 34 

12-19. Graphs showing variation in soil-gas helium at: 

12. Station 2 35 

13. Station 3 35 

14. Station 4 35 

15. Station 5 35 

16. Station 6 35 

17. Station 7 35 

18. Station 8 36 

19. Station 9 36 

20. Plot of the probability function used for equation 1 36 

21. Plot of probable migration distance with time for helium and radon in the 

soils at the Boyertown site 36 

22. Schematic diagram showing the physical and mineralogical difference 

between undeformed and deformed granodiorite 40 

23-25. Sketch maps showing: 

23. Location of shear zones in the Appalachian region 40 

24. Radon measured in soil gas for the Boyertown, Pa., area 41 

25. Indoor radon for the Boyertown, Pa., area 42 

26. Summary map of data for the Brookneal mylonite zone 43 

Contents XIII 
XIV Contents 

27, 28. Plots of: 

27. A, Uranium versus thorium for samples taken from outcrop along the 

railroad track; B, Uranium versus the angle between the C and S 

bands, as measured in the same samples; C, Uranitl'm measured in 

outcrop samples versus radon measured in the overlying soils 44 

28. Radon in soil along the railroad track and radon in soil measured 

along the road on top of the ridge versus the angle between the C and 

S bands 45 

29-31. Sketch maps showing: 

29. Radon in soil gas in the Glen Gardner area 46 

30. Indoor radon for the Glen Gardner area 47 

31. Radon potential for Montgomery County, Md. 48 

32. Plot of the average indoor radon versus average soil-radon concentrations 

for the shear zones described in this paper and for Easton, Pa. 49 

33-35. Maps showing: 

33. Locations of study areas in the Reading Prong 52 

34. Geology of the Boyertown study area, located in the northeast portion 

of the Boyertown 71fz-minute quadrangle 53 

35. Geology of the Easton study area, located in the northeast portion of 

the Easton 7th-minute quadrangle 54 

36. Graph showing typical soil permeabilities 55 

37. Sketch showing representative soil profiles from Boyertown and Easton, 

Pa. 56 

38. Diagram showing the distribution of soil textures forB and C horizons 

from selected soils (SCS classification system) 58 

39-42. Graphs showing: 

39. The relationship between uranium and radium for soils from 

Boyertown and Easton, Pa. 60 

40. The relationship between radium and in situ radon activity measured 

at 7 5 em in depth in selected soils 60 

41. The relationship between radium and radon, as measured from soil 

emanation experiments 61 

42. Radon in soil and total activity versus indoor radon 62 

43-48. Maps showing: 

43. Location of study area, Mulligan Quarry, Clinton, N.J. 66 

44. Locations of stations along traverses from a survey made with a 

gamma-ray scintillometer, Mulligan Quarry, Clinton, N.J. 68 

45. Gamma-ray scintillometer data, Mulligan Quarry, Clinton, N.J. 70 

46. Locations of stations along traverses from a survey made with a 

gamma-ray spectrometer and soil-gas measuring equipment, 

Mulligan Quarry, Clinton, N.J. 71 

47. Equivalent uranium concentrations, calculated from gamma-ray 

spectrometer data, Mulligan Quarry, Clinton, N.J. 73 

48. Radon-222 activity from soil-gas samples, Mulligan Quarry, Clinton, 

N.J. 74 

49. Cross plot of soil-gas radon-222 activities versus equivalent uranium 

values, Mulligan Quarry, Clinton, N.J. 75 

50. Map showing locations of soil-gas radon monitoring stations in central 

California 80 

51. Time series graphs of radon concentration recorded at 60 stations along 

several active faults in central California 81 

52. Time series plots of (A) atmospheric temperature and (B) daily rainfall 

recorded at Gilroy, near the center of the radon-monitoring network 141 
53. Plots of average radon concentrations recorded from 1975 to 1978 at stations 

1 to 30 versus (A) uranium contents of local soil and (B) emanating part of 

the uranium content 143 

54. Sketch of part of the radioactive decay series of uranium-238 showing 

radium-226 and daughter nuclides including radon-222 155 

55. Index map showing the NURE aerial gamma-ray surveys used to compile the 

data for New Jersey 156 

56. Contour map showing the near-surface concentrations of radium in New 

Jersey 157 

57. Map showing summary of average indoor radon levels and surface radium 

concentrations for physiographic provinces in New Jersey 158 

58. Frequency histogram of radium concentrations within the Valley and Ridge 

province 159 

59, 60. Charts showing: 

59. Average radium concentration versus the average indoor concentrations in 

New Jersey 159 

60. Average radon concentrations in soil gas versus average surface radium 

concentrations for various geologic materials in Montgomery County, 

Md. 159 

61. Radon assessment map based upon the Swedish criteria 160 

62. Map showing the percentage of homes having basements in the United States, 

by State 165 

63. Graph of average equivalent uranium concentrations versus basement and nonbasement indoor radon averages for nine areas sampled during the 1986-87 

EPA/State Indoor Radon Survey 168 

64-68. Generalized maps of Kentucky showing: 

64. Geology 169 

65. Major physiographic provinces 170 

66. Soil permeability 170 

67. Areas of anomalous surface radioactivity 171 

68. Average basement screening indoor radon levels by county 173 

69. Diagram of geologic radon potential 173 

70. Map showing location of radon soil-gas samples in Prince Georges County, 

Md. 179 

71, 72. Frequency histograms of: 

71. The radon distribution plotted by stratigraphic unit 180 

72. Radon concentrations for units of Cretaceous, Tertiary, and Quaternary 

ages sampled during the study 181 

73. Sketch of the uranium-238 decay series showing the half-lives of the 

radionuclidic elements and their modes of decay 184 

74-76. Graphs showing: 

74. The distribution of inorganic aqueous species of uranium as a function of 

pH 187 

75. The distribution of inorganic uranium species in Eh-pH space for the system U-0-C-H at 25 °C and 10-2

·

5 atm C02 188 

76. The distribution of inorganic aqueous radium species as a function of pH 

for three different conditions 189 

77. Map showing location of areas represented in the Northeastern United States 

and southern Ontario 196 

78-85. Maps showing locations referred to in text: 

78. Maine 202 

79. New Hampshire 204 

80. Vermont 207 

81. Massachusetts 209 

Contents XV 
XVI Contents 

82. Rhode Island 210 

83. Connecticut 212 

84. New York 215 

85. Canada-southern Ontario 219 

86-88. Sketches of: 

86. An all-glass de-emanation bubbler used for collecting water samples 

for analysis of radon-222 228 

87. The radon de-emanation system 228 

88. An alpha-scintillation cell and light-proof housing 229 

89. Histogram of radon-222 concentrations found in samples collected from 19 

wells and springs in Colorado 233 

90. Scatter plot of analyses for radon-222 by the liquid scintillation and 

degassing Lucas cell methods 233 

91. Plots showing the effect of lag time on the measurement of radon-222 in 

replicate samples from sites 88C0-7 (A) and 88C0-4 (B), collected and 

analyzed by the degassing Lucas cell method 234 

92. Plot showing the effect of lag time on the measurement of radon-222 in 

replicate samples from sites 88C0-13 and 88C0-14, collected and 

analyzed by the liquid scintillation method 234 

93, 94. Maps showing: 

93. Locations of measurements of surface-water discharge and radon-222 

activities for September 16-17, 1986, in Carters Creek 238 

94. Locations of measurements of surface-water discharge and radon-222 

activities for February 12, 1987, in Carters Creek 239 

95. Graph of stream temperatures and radon-222 activities in a 0.75-mile reach 

of Carters Creek for September 16-17, 1986 241 

96. Map showing location of study area, Newark basin, New Jersey 245 

97. Generalized geologic map of the Newark basin, New Jersey, and location 

of coreholes 246 

98. Map of well-sampling sites and gross alpha-particle activities in ground 

water from the Newark basin, New Jersey 248 

99, 100. Scatter plots of: 

99. Radium-226 concentration as a function of uranium concentration in 

ground water in the Newark basin, New Jersey 251 

100. Radon-222 concentration as a function of (A) uranium concentration 

and (B) radium-226 activity in ground water in the Newark basin, 

New Jersey 252 

101. Gamma-ray log, lithologic description, and environment of deposition of 

corehole A, and gamma-spectral log of radioactive zone in the 42- to 

43-foot depth interval 253 

102. Rock samples and autoradiographs of radiation development from corehole 

A at depth intervals of (A) 42.3 to 42.4 feet and (B) 42.6 to 42.8 feet 255 

103-107. Scatter plots of: 

103. (A) Uranium concentration and (B) radium-226 concentration as a 

function of dissolved-oxygen content in ground water in the Newark 

basin, New Jersey 257 

104. (A) Uranium concentration and (B) radium-226 concentration as a 

function of Eh in the ground water in the Newark basin, 

New Jersey 258 

105. (A) Uranium concentration and (B) radium-226 concentration as a 

function of dissolved-iron concentration in the ground water in the 

Newark basin, New Jersey 259 
106. (A) Uranium concentration and (B) radium-226 concentration as a 

function of pH in ground water in the Newark basin, 

New Jersey 259 

107. (A) Uranium concentration and (B) radium-226 concentration as a 

function of sulfate concentration in ground water in the Newark basin, 

New Jersey 260 

108. Map showing location of the Chickies Quartzite in southeastern 

Pennsylvania 268 

109-114. Graphs showing: 

109. Activity ratios of radium-228 to radium-226 for 70 ground-water 

samples from the Chickies Quartzite 272 

110. Relation between total radium concentration and pH for 106 wells in 

the Chickies Quartzite 274 

111. Relation between total radium and manganese concentrations for 92 

wells in the Chickies Quartzite 275 

112. Relation between total radium and barium concentrations for 92 wells 

in the Chickies Quartzite 275 

113. Relation between total radium and dissolved organic carbon 

concentrations for 89 wells in the Chickies Quartzite 275 

114. Relation between radon-222 and radium-226 concentrations for 103 

wells in the Chickies Quartzite 276 

115, 116. Maps showing: 

115. Location of Carson Valley, Nevada, and sampling sites 281 

116. Generalized geology of the Carson Valley study area 284 

117. Schematic cross section showing hydrogeologic relations in Carson 

Valley 285 

118, 119. Graphs showing: 

118. Distribution of radon-222 activities in sampled ground water 285 

119. Relation between radon-222 and specific conductance in sampled 

ground water 287 

120-122. Geologic sketches showing: 

120. The Boyertown study area 290 

121. The Easton study area 291 

122. Radon-222 concentrations in ground water of the Boyertown study 

area 292 

123. Histogram of dissolved-radon-222 concentrations in ground water from 

three aquifers in the Boyertown study area 292 

124-126. Geologic sketches showing: 

124. Dissolved-oxygen concentration in the Boyertown ground water 293 

125. Dissolved-uranium concentration in the Boyertown ground 

water 293 

126. Uraninite saturation indexes for the Boyertown ground-water 

samples 295 

127, 128. Maps showing: 

127. The Little Colorado River basin 298 

128. The Puerco River basin 299 

129. Aerial photograph of the Puerco River basin 300 

130. Photograph of the Church Rock tailings pond 301 

131, 132. Graphs showing: 

131. Temporal variations of selected chemical constituents in the Puerco 

River at Chambers, Ariz. 305 

132. Temporal variations of selected chemical constituents in the Little 

Colorado River at Cameron, Ariz. 306 

Contents XVII 
XVIII Contents 

133. Plotted radium and salinity relation in formation water from the U.S. Gulf 

Coast 315 

134. Location map for the study area in the upper part of the drainage basin of 

the north fork of Flodelle Creek 320 

135. Plan maps of the study area in the upper part of the drainage of the north 

fork of Flodelle Creek 322 

136-139. Plots of: 

TABLES 

136. Radon and helium data for shallow ground waters and spring waters 

from the 1985 and 1986 sampling in the study area 328 

137. Radon and helium data for shallow ground waters from the 1985 and 

1986 sampling in the study area, shown with an expanded scale for 

comparison with calculated radon and helium yields for the shallow 

sediment 330 

138. Ratio of observed to calculated radon levels for the shallow ground 

waters in the 1985 sampling 331 

139. Oxygen, carbon dioxide, and methane data for the 1985 

samples 332 

1. Calculated interstitial mean migration distances for radon-222 7 

2. Characterization of soil at 1.2 m in depth at a site in Fairfax County, Va. 11 

3. Linear correlation coefficient matrix of weather and radon parameters at the 

Denver Federal Center study site 29 

4. Summary of factors influencing soil-gas radon concentrations 29 

5. Textural analysis of selected soils 57 

6. Lab data for uranium, radium, and radon for Pennsylvania soils 59 

7. Gamma-ray spectrometer data and calculated concentrations of potassium, 

uranium, ant thorium, Mulligan Quarry, Clinton, N.J. 72 

8. Soil-gas radon monitoring sites, central California 79 

9. Particle-size analysis (dry sieving) of uranium mill tailings 147 

10. Quantity of fine particles (-325 mesh) in dry-sieved fraction as determined by 

subsequent wet dispersion and sieving 147 

11. Properties of wet-dispersed and wet-sieved uranium mill tailings 148 

12. Analysis of filtered water collected following aqueous dispersion and sieving of 

uranium mill tailings 149 

13. Distribution of radium-226 in uranium mill tailings as a function of particle size 

(dry sieving) 149 

14. Radon emanation coefficient of particle-size fractions (dry sieving) of uranium 

mill tailings 149 

15. Characteristics of ore samples and leaching conditions used 151 

16. Radium-226 content and the radon-222 emanation coefficient of ore and tailings, 

and the. yield and uranium content of tailings 152 

17. Particle-size distribution of ore and tailings samples as determined by wet 

sieving 152 

18. Percentage of radium-226 (initially in ore) found in tailings solids 152 

19. Average indoor radon levels for counties in New Jersey 159 

20. Equivalent uranium, soil permeability, housing construction, and indoor radon 

data for nine areas sampled during the 1986-87 EPA/State Indoor Radon 

Survey 168 

21. Average screening indoor radon levels, number of homes tested, and percent 

greater than 4 picocuries per liter for 40 counties in Kentucky 172 
22. Soil-gas radon concentrations for the traverse in Prince Georges County, 

Md. 178 

23. The solubility of radon in water from 0 to 100 oc 189 

24. Natural radioactivity in public water supplies in the United States 199 

25. Radionuclide concentrations in public ground-water supplies in New England and 

New York 200 

26. Total uranium and radon-222 concentrations in water supplies in New England 

and New York 200 

27. Geohydrologic data and concentrations of radium and uranium in water samples 

from wells in Maine 203 

28. Radon-222 concentrations in Maine ground water, by aquifer type 203 

29. Geohydrologic data and concentrations of radium and uranium in water samples 

from wells and springs in New Hampshire 205 

30. Radon-222 concentrations in New Hampshire ground water, by formation 205 

31. Concentrations of radon-222 and gross-alpha radiation in drinking-water systems 

in Vermont 206 

32. Geohydrologic data and concentrations of radium and uranium in water samples 

from wells and springs in Massachusetts 209 

33. Geohydrologic data and concentrations of radium and uranium in water samples 

from wells and springs in Rhode Island 211 

34. Geohydrologic data and concentrations of radium and uranium in water samples 

from wells and a spring in Connecticut 213 

35. Results of the 1985-87 well-water survey of 202 homes in Connecticut for 

radon-222 214 

36. Summary of radon-222 in indoor air in Connecticut during the winter of 

1986-87 214 

37. Geohydrologic data and concentrations of radium and uranium in water samples 

from wells and a spring in New York 217 

38. Concentrations of radon-222 in indoor air in New York, by region and 

stratigraphic units 218 

39. Transportation and storage loss of radon-222 230 

40. Precision of radon-222 in water analysis 230 

41. Comparison of liquid scintillation and Lucas cell methods by the EPA, with the 

cooperation of 28 privately owned laboratories 232 

42. The results of this study comparing the liquid scintillation and degassing Lucas 

cell methods 232 

43. Effect of increasing lag time on the measurement of radon-222 in water samples 

by the degassing Lucas cell method 234 

44. Effect of increasing lag time on the measurement of radon-222 in paired water 

samples by the liquid scintillation method 235 

45. Range and median values of radionuclide concentrations in ground water in the 

Newark basin, New Jersey 250 

46. Range and median values of selected water-quality characteristics and 

constituents in ground water from the Newark basin, New Jersey 256 

47. Field measurements of temperature, pH, specific conductance, alkalinity, and 

dissolved oxygen for ground water from the Chickies Quartzite 271 

48. Laboratory determinations for dissolved concentrations of radium-226, 

radium-228, total uranium, and radon-222, and gross alpha-particle and gross 

beta-particle radioactivity 271 

49. Distribution by county of total radium and radon-222 in samples of ground water 

in the Chickies Quartzite 271 

50. Determinations of inorganic constituents and dissolved organic carbon in ground 

water in the Chickies Quartzite 273 

Contents XIX 
XX Contents 

51. Spearman rank correlation for chemical constituents and well yield with total 

radium and radon-222 significant at the 95-percent confidence level 274 

52. Data on sampled wells, Carson Valley, Nev. 282 

53. Generalized stratigraphy of the Carson Valley study area 283 

54. Analyses of water from sampled wells in the Carson Valley 286 

55. Field methods used during ground-water sampling in the Reading Prong, 

Pa. 291 

56. Chemical analyses of the Boyertown study area well waters 294 

57. Chemical analyses of the Easton study area well waters 295 

58. Radionuclide activities and associated data of selected samples from U.S. 

Geological Survey gaging stations on the Puerco and lower Little Colorado 

Rivers, Arizona and New Mexico 304 

59. Average and median concentrations or activities of selected constituents measured 

in 15 ground-water samples from the Puerco River basin, December 1-6, 

1986 306 

60. Values of saturation indices for minerals of uranium and lead in an average 

sample of ground water from the Puerco River basin with uranium concentrations 

of 0.019, 0.100, and 0.360 milligrams per liter 309 

61. Uranium content of geopressured-geothermal formation-water samples from the 

U.S. Gulf Coast 314 

62. Comparison of radium-228/radium-226 activity ratios of formation water with 

thorium/uranium activity ratios of the host matrix 315 

63. Radon activity in conventional gas at well head in the U.S. Gulf Coast 316 

64. Radon activity in geopressured solution gas at well head in the U.S. Gulf 

Coast 317 

65. Radon and radium activity in formation water produced from geopressuredgeothermal test wells 317 

66. Multiple measurements of radon taken at the same site in northeast 

Washington 326 

67. Measurements of radon and helium in shallow ground waters in northeast 

Washington 327 

68. Radon measurements of selected spring and surface-water sample sites in 

northeast Washington 328 

69. Oxygen, carbon dioxide, and methane data for selected sample sites and springs 

in northeast Washington, 1985 331 
METRIC CONVERSION FACTORS 

For readers who wish to convert measurements from the inch-pound system of units to the metric system of units, the conversion factors are listed below: 

Multiply 

micrometer (!J.m) 

millimeter (mm) 

centimeter (em) 

meter (m) 

kilometer (km) 

centimeter2 (cm2

) 

meter (m2

) 

hectometer2 (hm2

) 

kilometer2 (km2

) 

centimeter3 (cm3

) 

milliliter (mL) 

liter (L) 

kilometer3 (km3

) 

By 

Length 

0.000 039 37 

0.039 37 

0.393 7 

3.281 

1.094 

0.621 4 

Area 

0.155 0 

10.76 

1.196 

0.000 247 1 

2.471 

0.386 1 

Volume 

0.061 02 

0.061 02 

61.02 

0.035 31 

33.82 

2.113 

1.057 

0.264 2 

35.31 

1.308 

264.2 

0.000 810 7 

0.239 9 

To obtain 

inch (in) 

inch (in) 

inch (in) 

foot (ft) 

yard (yd) 

mile (mi) 

inch2 (in2

) 

foot2 (ft2

) 

yard2 (yd2

) 

acre 

acre 

mile2 (mi2

) 

inch3 (in3

) 

inch3 (in3

) 

inch3 (in3

) 

fooe cfe) 

ounce, fluid (oz) 

pint (pt) 

quart (qt) 

gallon (gal) 

fooe cfe) 

yard3 (yd3

) 

gallon (gal) 

acre-foot (acre-ft) 

mile3 (mi3

) 

Volume per unit time (includes flow) 

gram per minute 0.035 27 ounce (avoirdupois) 

(g/min) per minute ( oz/min) 

milliliter per minute 0.033 82 ounce (fluid) per 

(mL/min) minute (oz/min) 

0.035 31 fooe per second (fe/s) 

liter per second (Lis) 15.85 gallon per minute 

(gal/min) 

meter per second (m/s) 3.281 foot per second (ft/s) 

meter per day (mid) 3.281 foot per day (ft/d) 

meter2 per day (m2

/d) 10.76 foot2 per day (ft2

/d) 

ALTITUDE DATUM 

Multiply By To obtain 

Volume per unit time (includes flow)-Continued 

meter3 per second 

(m3/s) 

microgram (!J.g) 

gram (g) 

kilogram (kg) 

microgram per liter 

(!J.g/L) 

milligram per liter 

(mg/L) 

35.31 

15 850 

Mass 

0.000 015 43 

0.035 27 

0.002 205 

fooe per second (fe/s) 

gallon per minute (gal/min) 

grain (gr) 

ounce, avoirdupois 

(oz avdp) 

pound, avoirdupois 

(lb avdp) 

Mass per unit volume 

0.000 058 41 grain per gallon (gr/gal) 

0.058 41 grain per gallon (gr/gal) 

Temperature 

degree Kelvin=degree Celcius+273.15 

degree Celsius (

0

C) Temp °F=l.8 temp °C+32 degree Fahrenheit eF) 

microsiemens per 

centimeter at 25 

degrees Celsius 

(!J.S/cm at 25 °C) 

rnillisiemens per 

meter at 25 

degrees Celsius 

(mS/m at 25 °C) 

Specific conductance 

1.000 

1.000 

Activity 

micrornho per centimeter 

at 25 degrees Celsius 

(!J.rnho/cm at 25 °C) 

millirnho per meter at 

25 degrees Celsius 

(mrnho/m at 25 °C) 

1 becquerel (Bq)= 1 disintegration per second 

1 Curie (Ci)=3.7X 1010 Bq 

1 picocurie (pCi)=0.037 Bq 

Radon concentration 

1 Bq/m3=2. 7X 10- 2 pCi/L 

1 pCi/L=37 Bq/m3 

Radon progeny concentration 

Working level (WL)=7.4X 103 Bq/m3 

=2X 102 pCi/L 

National Geodetic Vertical Datum of 1929 (NGVD of 1929): A geodetic datum derived from a general adjustment of the first-order level nets of 

both the United States and Canada, formerly called Sea Level Datum of 1929. 

Contents XXI 

PART 1: STUDIES OF RADON IN ROCKS AND SOIL 

SECTION 1: TECHNIQUES FOR MEASURING RADON IN SOIL 

METHODS OF CHARACTERIZATION OF GROUND FOR ASSESSMENT OF 

INDOOR RADON POTENTIAL AT A SITE 

Allan B. Tanner 

Abstract 

The co.1centration and mobility of radon-222 in soil 

interstices control the potential of ground to supply radon 

to a structure. Radon mobility depends on its diffusivity 

and on the permeability of the ground to flow of soil gas. 

Several soil-probe methods currently under development 

can be used to measure the radon concentration in soil 

gas and to obtain gas-flow characteristics from which the 

gas permeability of the ground can be inferred. The radon 

diffusion coefficient can be inferred from measurements 

of the porosity and pore water fraction of samples of soil 

removed for emplacement of the soil probe. General 

principles of soil development and tests made with a 

special soil probe indicate that layered soils are more 

permeable to gas flow in the horizontal than in the vertical 

direction, although cracking in soils can cause high 

vertical permeability along the cracks. Soil cracks and rock 

fracture systems pose problems of test-probe spacing and 

modeling that have not been resolved. Changes in the 

degree of pore water saturation can affect the radon 

concentration in the gas phase by as much as a factor of 4 

and radon mobility by as much as 3 orders of magnitude. 

In order to lessen the effects of short-term meteorological 

and seasonal changes on characterization of the ground, 

soil-probe measurements should be made as deeply as is 

feasible, ideally to the depth of the slab of a building to be 

constructed at the site. For slab-on-grade and crawl-space 

house sites, the soil may be best characterized by means 

of soil-gas accumulators operated with a degree of suction 

comparable with that exerted by a house during the 

season in which the house is heated. 

INTRODUCTION 

Testing of the ground in order to determine its indoor 

radon potential for an existing structure is more expensive 

than a straightforward test of the radon concentration in the 

structure. Ground tests may not be economical in the 

preconstruction phase for single structures of typical design 

if the ground has normal or moderately elevated indoor 

radon potential, because the cost of testing may approach 

that of incorporating aids to radon mitigation into the 

structure. The cost of constructing a new house so as to 

Manuscripts approved for publication February 22, 1991. 

facilitate mitigation may range from $231 to $1,381 (John 

Spears, National Association of Home Builders, written 

commun., 1988). For structures of designs incompatible 

with the usual mitigation techniques, for large or extended 

structures, and for developments containing large numbers 

of homes, preconstruction testing may allow the builder to 

avoid unnecessary provision for radon mitigation or may 

indicate that extraordinary measures must be taken to avoid 

indoor radon problems. Although developers and home 

builders frequently ask consultants and site engineers to 

determine the indoor radon potential of sites, no such test 

has yet been proven reliable. Problems in developing a 

standard test include accounting for spatial variations of 

radon's soil-gas concentration and mobility on a meterto-meter scale and temporal variations of the same factors 

caused by freezing or variable water content of the soil. 

Also, no agreement has been reached on the suitability of 

measurement techniques. 

The emanation of radon from rock and soil minerals 

and migration of radon in the ground have been reviewed by 

Tanner (1964, 1980); references more specific to the ground 

as a source of indoor radon were given by Akerblom and 

others (1984), Nero and Nazaroff (1984), Eaton and Scott 

(1984), Nero (1985), Tanner (1986), and Nazaroff and 

others (1988). Research on site-specific measurements to 

assess indoor radon potential is active in Scandinavia, in the 

United States, and probably in several other countries, but 

little has appeared in the literature about quantitative 

approaches. Akerblom (1986) gave Swedish criteria for 

classifying radon risk based on radon concentrations in soil 

gas: less than 10 kBq/m3 (kilobecquerels per cubic meter) 

(270 pCi/L, picocuries per liter) is classed as "low risk"; 

greater than 50 kBq/m3 (1 ,350 pCi/L) is classed as "high 

risk"; and between 10 and 50 kBq/m3 is classed as "normal 

risk." He noted, however, that low permeability of the soil 

(high resistance to flow of the soil gas) works to shift the 

risk classification to the next lower level; conversely, high 

permeability works to shift the risk classification to the next 

higher level. Measurements of radon in soil gas are used in 

many countries; see, for example, Hesselbom (1985), 

Lindmark and Rosen (1985), Reimer (1988), and other 

papers in this Bulletin. In Finland, a procedure involving 

laboratory measurements of radon production and diffusion 

Methods of Characterization of Ground for Assessment of Indoor Radon Potential at a Site 
and permeability to air flow in soil samples is under 

development for ground classification (Slunga and Holkko, 

1987). The flux of radon obtained by suction at the ground 

surface is the basis of an investigatory method in Denmark 

(Kaare Ulbak, Statens Institut for Stralehygiene, Bnz~nsh!Z)j, 

oral commun., 1986). In New York State, Kothari and 

others (1985) have made extensive use of a soil probe to 

extract soil gas for radon analysis and to determine simultaneously the permeability of the ground at the sampling 

depth, following a scheme devised by Scott (DSMA Atcon, 

Ltd., 1983). Similar apparatus are used by the Lawrence 

Berkeley Laboratory (R.G. Sextro, oral communication, 

1987), by the Environmental Protection Agency (R.T. 

Peake, written communication, 1988), and by the U.S. 

Geological Survey (Tanner, 1988), but the data are used 

differently. Kunz (1988) used an equation relating a "radon 

index number" to radon concentration in the soil gas, depth 

to the water table or bedrock, and soil permeability. The 

Environmental Protection Agency approach (Peake, 1988) 

is similar to that of Akerblom (1986). Nazaroff (1988) 

modeled radon entry into a basement structure on the basis 

of the permeability of the ground outside the foundation and 

radon entry at the level of the basement slab. Tanner (1988) 

proposed a protocol, described below, that applies values of 

molecular diffusivity and permeability obtained from in situ 

sampling to a model of one-dimensional radon migration. 

All these approaches assume that the ground is homogeneous and isotropic (that is, that radon diffusion or soil-gas 

flow proceeds with equal ease in all directions), although 

inhomogeneity and anisotropy of permeability are known to 

be common, as discussed below. It is also assumed that 

measurements made at a particular time are either representative of the site or may be corrected to be representative, 

although significant variation is to be expected because of 

precipitation, seasonal temperature changes, and barometric 

pressure fluctuations. This report is intended to examine 

these variables as they affect in situ measurements in 

general and the soil-probe methods in particular. 

THE EMANATION PROCESS 

Only a fraction of the radon that is generated by decay 

of radium-226 e26Ra) in rock and soil escapes from solid 

material and into the rock or soil pores. This fraction was 

termed "emanating power" about 1900 (Rutherford, 1901), 

but in the past two decades different names have proliferated, the most common name being "emanation coefficient." The emanation process was discussed by Tanner 

(1964, 1980) from concepts and evidence of many investigators. In packed aggregates of mineral grains, emanating 

power is usually of the order of 1 percent unless water or 

other liquid is present in the smaller interstices, fractures, 

and capillaries to absorb the kinetic energy of radon ions 

2 Field Studies of Radon in Rocks, Soils, and Water 

recoiling from the radium alpha-particle decay. The water 

content of most soils is sufficient to make the emanating 

power much greater than 1 percent; Rogers and Nielson 

( 1988) reported a mean value of 22 percent for 56 western 

soils. The siting of the radium atoms in rock and soil is also 

very important in determining how readily the radon atoms 

can escape upon radium decay. The emanating powers 

typically reported for soils are consistent with the siting of 

significant fractions of the radium on grain surfaces and 

within secondary coatings on the grains. Both the development of external and internal surface areas of the mineral 

grains and the deposition of radium on surfaces and within 

surface coatings proceed with biological and chemical 

activity that attacks the grains; the fraction of radium 

exposed to the pores may correlate to some degree with the 

age of a soil. 

Most of the site-specific methods of assessing indoor 

radon potential measure the radon concentration of soil gas 

rather than the total radium content of the rock or soil; 

emanating power determinations are then unnecessary. 

However, for assessments that use gamma radiation or 

chemical uranium measurements to gauge the inherent 

radioactivity of the ground, emanating power needs to be 

evaluated. 

PERMEABILITY 

Soil particles tend to be oriented with their longest 

dimensions in the horizontal plane. Nazaroff and others 

( 1988) cited works by Rice and others ( 1970) and by 

Bowles (1979) that report markedly greater permeability in 

the horizontal than in the vertical direction, particularly for 

fine-grained soils having significant fractions of clay minerals. Bowles (1979, p. 212-213) stated that the horizontal 

permeability is commonly on the order of 10 to 1,000 times 

greater than the vertical permeability. This anisotropic 

permeability can be evaluated to some extent from measurements made with the soil probe shown in figure 1. The three 

inflated rubber packers create three isolated annular spaces 

in the borehole. If suction is applied to the middle space 

only, soil gas in an uncracked soil flows into the middle 

space along the radii of a sphere. If suction is applied to the 

upper and middle spaces, flow is along radii of a hemisphere that has its convex surface extending downward. If 

suction is applied to the middle and lower spaces, flow is 

along radii of a hemisphere that has its convex surface 

extending upward. If suction is applied to all three spaces, 

the flow into the middle space is along radii of a cylinder of 

height equal to the spacing of the packers. These flow 

patterns are, of course, only approximate because of the 

interference of the probe itself and because the soil-gas 

pressures ultimately are asymmetrically referred to the 

ground surface rather than to a spherical surface at distance 

from the sampling probe. However, the flow paths near the 
A 

SUCTION 

TUBES 

8 

Figure 1. Modes of operation of three-packer soil probe. 

(Tubes for inflation of the packers and for pressure monitoring are not shown.) Atmospheric absolute pressure Pa 

of approximately 101 kPa (kilopascals) is assumed to 

prevail initially in the soil. The flow patterns can be 

controlled by reducing the absolute pressures by small 

amounts (less than 5 kPa) in the annular spaces created by 

the inflated rubber packers. A, No suction is exerted on 

spaces 1 and 3. The flow into space 2 is approximately 

spherical (along radii of a sphere centered at space 2). B, 

Suction is exerted on spaces 1 and 2. The flow into space 

2 is from the hemisphere whose convex surface is downward. C, Suction is exerted on spaces 2 and 3. The flow 

probe have been calculated by Nazaroff (1988, fig. 2) to 

satisfy the spherical flow pattern approximately. In many 

soils of high clay content, I found changing from the 

downward-hemispherical mode of operation to the spherical 

mode resulted in a small to unmeasurable increase of flow 

into the middle space. The implication is that vertical flow 

from above was negligible and that the flow was predominantly horizontal or from the downward hemisphere. It has 

not been determined whether the apparent permeability 

derived from measurements in spherical or hemispherical 

geometry or the permeability derived from measurements 

with a controlled cylindrical geometry gives a more appropriate value of permeability to be used in a test to evaluate 

the total soil-gas movement to a structure's foundation (see 

appendixes B and C). 

c 0 

into space 2 is from the hemisphere whose convex surface 

is upward. D, Suction is exerted on spaces 1, 2, and 3. The 

flow into space 2 is along radii of an annular cylinder 

coaxial with the borehole. Near the sampling probe, the 

flow lines deviate from radial because of the interference 

width of the probe. After prolonged suction, the flow lines 

must be distorted toward the ground surface, because the 

ultimate source of air is the atmosphere; however, the 

indicated flow paths should obtain for a typical measurement period of several minutes. Anisotropic permeability 

affects both the flow lines and the proportions of soil gas 

entering space 2 from different horizons. 

Constructing a building that has a full or partial 

basement usually involves excavating, laying down coarse 

aggregate to break capillary action between the ground and 

the basement slab and to promote drainage under the slab, 

and backfilling the gap, typically about 0.5 m (meter) wide, 

between the sides of the excavation and the basement walls. 

The coarse aggregate is much more permeable, and the 

backfill material may be significantly more permeable than 

the undisturbed ground. The voids in this backfill-subslab 

aggregate zone may constitute a reservoir, or plenum, for 

radon that emanates from the material in the zone and for 

radon that can migrate into the zone from the undisturbed 

ground beyond it. Once in the zone, radon-bearing soil gas 

may move through available entry points in response to 

reduced pressure in the building. Various investigators have 

Methods of Characterization of Ground for Assessment of Indoor Radon Potential at a Site 3 
noted increased radon entry with a decrease in indoor 

atmospheric pressure. The decrease may be that accompanying a decrease of outdoor barometric pressure and may 

cause the greater soil-gas pressure under a house to be 

relieved by flow into the house (Schmid, 1932), or indoor 

pressure may by various means be reduced relative to the 

outdoors, with the same result (Akerblom and others, 1984; 

Eaton and Scott, 1984; Nero and Nazaroff, 1984; Nazaroff 

and Doyle, 1985; Nazaroff and others, 1985; Nero, 1985; 

and Sextro and others, 1987). High permeability in the 

backfill-subslab aggregate zone may account for radon 

entry that is due to pressure-driven flow. Whether the radon 

entering a house originates mainly within this zone or in the 

undisturbed ground beyond is considered next. 

DIFFUSION 

A concentration of radon in soil gas, resulting from 

the continual decay of radium in the soil, causes movement 

of radon in the direction of lessening concentration, without 

any necessary flow of the soil gas, by the process of 

diffusion. Radon migration in soil proceeds both by diffusion and by transport with moving soil gas. The ease of 

migration by diffusion is measured by the effective bulk 

diffusion coefficient, De, of the soil, and the ease of soil-gas 

flow is measured by its permeability. Nazaroff and others 

(1988, p. 91) have shown that diffusive migration is 

dominant if D/e is larger than k ~Pof~. where e is the 

porosity of the soil, k is its permeability, ~P0 is a pressure 

difference driving soil-gas flow, and ~ is the absolute 

viscosity of the soil gas. Pressure-driven flow is dominant if 

the reverse is true. In general, radon migration by advection 

(horizontal flow) or convection (vertical flow) predominates 

in soils composed of well-sorted sand or gravel, and 

diffusion predominates in poorly sorted and fine-grained 

uncracked soils. Because the average upward and downward pressure gradients in the soil tend to balance over 

several days' time, the depletion of radon from the soil to 

the atmosphere tends to be little more than that which would 

result from diffusion alone (Schery and others, 1984). The 

distance that radon moves by diffusion through the soil 

interstices during one mean life is called its diffusion 

length, equal to VTD/e, where 'Tis the mean life of radon 

atoms (5.52 days). S~gaard-Hansen and Damkjaer (1987) 

measured radon diffusion lengths from 1. 6 to 1. 9 m for dry 

silt, sand, and gravel samples, and 0.01 m for wet clay. 

Water in soil pores has long been known to reduce the 

diffusion coefficient markedly, the inferred mechanism 

being the blocking of interpore openings by the water. 

Diffusion is little affected by pore and grain size in most 

sediments, but permeability is a function of pore and grain 

size. Both radon diffusion and gas permeability are strongly 

decreased by water in the pores. No substantial set of data 

is known to indicate whether an increasing pore water 

4 Field Studies of Radon in Rocks, Soils, and Water 

fraction can reduce radon movement by diffusion to a 

greater extent than by soil-gas flow. Both diffusion and 

soil-gas flow are retarded by solid soil grains, which 

increase the path length actually followed by gas molecules 

to achieve movement in a given direction. The ratio of the 

actual path length to the distance traversed in the given 

direction is called tortuosity (Levorsen, 1958, p. 94); Bear 

(1969, p. 164) treated tortuosity as a dimensionless secondrank tensor. 

MODELS OF THE SOIL REGIME NEAR A 

HOUSE 

Slab-on-grade buildings and buildings that have crawl 

spaces usually are constructed near ground level. For such 

buildings, the upward flux density of radon through the 

ground surface is the logical basis for evaluation of the 

indoor radon potential of the ground. Israel (1962) showed 

that, under steady diffusion from homogeneous ground to 

the atmosphere, the amount of radon that can be sustained 

in a column of the atmosphere of unit ground area is the 

amount generated in the ground per unit area to a depth 

equal to the diffusion length discussed previously. An 

analogous "interstitial mean migration distance" can be 

obtained by including the effect of steady-state convection 

due to the pressure difference between the air in the soil and 

the air in a hypothetical building resting on the soil. 

Clements (1974) derived an. equation (see appendix A) 

incorporating both diffusion and convection for the steadystate radon flux density from the soil. Multiplication of this 

flux density by the mean life of radon yields the maximum 

amount of radon per unit area that can be sustained 

externally to the soil. Methods of measuring the flux density 

of radon are called "accumulator methods" and have been 

reviewed by Colle and others (1981). An accumulator 

method that includes a provision for suction to measure the 

convective response of the ground seems to be the most 

logical approach to evaluate indoor radon potential for 

slab-on-grade and crawl-space buildings. 

For buildings that are to be extended well below 

grade, where the soil characteristics may differ significantly 

from those at the surface, flux-density measurements at the 

surface are less appropriate than measurements of soil 

characteristics at depth. Several investigators, mentioned in 

the introduction, are currently making such measurements. 

Nazaroff (1988) and Tanner (1988) have developed models 

for using the soil characteristics to predict radon entry into 

or availability to houses that have basements. 

Nazaroff's (1988) model considered a homogeneous 

ground outside the foundation of a house that has a 

basement and air flow from the atmosphere down through 

the soil to an entry zone at the level of the basement slab. 

The model was applied to a house in ground sufficiently 

permeable that diffusion could be neglected. 
Figure 2. The model used to define radon availability 

(Tanner, 1988). The upper part of the figure shows a house 

with a basement and the assumed paths of radon movement to the backfill zones next to the foundation walls and 

As part of a proposed protocol, Tanner (1988) also 

modeled a house having a basement in homogeneous 

ground but considered both diffusive and convectiveadvective migration of radon to the foundation and recognized the backfill-subslab aggregate zone only as a conduit 

for easy transport of radon to entry points. In order to 

facilitate computation in the protocol, a crude transformation is made by unfolding the basement walls to the plane of 

projection of the slab, and the migration is modeled as one 

dimensional (fig. 2) and comparable with the situation for 

slab-on-grade structures. The protocol obtains a "mean 

migration distance," which is the interstitial mean migration 

distance discussed previously, multiplied by the soil porosity. The mean migration distance is the net interstitial 

volume of radon-bearing soil gas available per unit area, 

instead of a soil volume per unit area. The apparatus used in 

the protocol is shown in figure 3. A hole 3.5 em (centimeters) in diameter is drilled or augered into the ground to a 

depth of at least 1 m, if possible, and preferably to the depth 

of the basement slab of the structure proposed for the site. 

A sample of the soil from the bottom of the hole, packed as 

nearly as possible to its original density into a canister of 

known volume, is taken to the laboratory for weighing and 

determination of its porosity and pore water fraction. The 

coefficient of molecular diffusion for radon in the porous 

ground is calculated from the porosity and pore water 

fraction by means of an empirical relation found by Rogers 

and others ( 1984). The sampling probe is inserted into the 

} MEAN MIGRATION DISTANCE 

POROSITY 

to the subslab aggregate. The lower part is a crude 

transformation of the upper part to a one-dimensional 

flow regime and is equal in height to the mean migration 

distance divided by the porosity. 

hole, the rubber packers are inflated by means of a bicycle 

pump, and soil air is continuously pumped from the 

sampling space through a flow chamber that responds to the 

alpha-particle radioactivity of radon and its first decay 

product by scintillations in a phosphor coating inside the 

chamber. The scintillations are detected and counted by a 

photomultiplier tube and its associated electronics to obtain 

the radon concentration in the soil gas. The rate of flow of 

the soil gas is measured by a rotameter, and the pressure 

difference between the sample space and the atmosphere is 

measured by the sample pressure gauge; these two quantities enable calculation of the permeability of the ground at 

the sampling point (see appendix B). A "radon availability 

number" (RAN) is then calculated by inserting the values of 

radon concentration, diffusion coefficient, and permeability 

into an equation that is based on a model of onedimensional upward migration under the influence of a 

standard pressure difference (see appendix A). The small 

number of radon availability determinations made so far 

have correlated roughly with indoor radon values at the 

respective sites (fig. 4). Because of inhomogeneity of the 

ground, a yet-undetermined number of measurements must 

be taken at a site to assure that representative radon 

availability numbers are obtained. Short- and long-term 

variability of the soil characteristics also causes significant 

uncertainties in the method. 

Certain soils of moderate to high clay content tend to 

crack when dry, and as a result permeability is greater along 

Methods of Characterization of Ground for Assessment of Indoor Radon Potential at a Site 5 
INFLATION AIR -+ 

FOR PACKERS 

~ PACKERS~ 

DIFFERENTIAL 

PRESSURE 

(WASTE SAMPLE) 

/ 

WASTE 

(GUARD) 

SPACE 

VALVE 

DUST 

FILTER SAMPLE 

PRESSURE 

ALPHA 

SCINTILLATION 

FLOW 

CELL 

WASTE 

PUMP 

~ NO FLOW 

----·ACROSS THIS 

SURFACE 

SAMPLE 

SPACE 

Figure 3. Apparatus for extracting and measuring radon 

concentration of soil gas and measuring flow rate and 

driving pressures for permeability calculation. The hole 

diameter is about 3.5 em but is not critical. The absolute 

the cracks than in the uncracked parts of the soils. Because 

of their discontinuous nature, cracked soils and rock fractures are difficult to incorporate into models of radon 

migration into structures. Unless the cracks are closely 

spaced, test probes are likely to underestimate permeability 

to an indeterminate degree. Neither the sampling nor the 

modeling problems associated with cracks and fractures 

have apparently been resolved at present. However, Schery 

and Siegel (1986) stated that radon moving through the 

cracks in soils tends to diffuse transversely into the 

uncracked parts of the soil and thereby reduce the increase 

of radon availability due to the cracks. 

The maximum amount of interstitial radon originating 

within the backfill and subslab aggregate zones per unit area 

can be calculated by multiplying the zones' measured or 

estimated interstitial radon concentrations by their porosities and thicknesses. Because the stone used under the slab 

is usually of types that emanate little radon, and because the 

subslab aggregate layer is normally much thinner than the 

6 Field Studies of Radon in Rocks, Soils, and Water 

ELECTRONICS SAMPLE 

PUMP 

pressure maintained in the waste space is slightly less than 

that in the sample space, in order to ensure that 

atmospheric air does not dilute the soil gas sample taken 

from the sample space. 

backfilled gap, the backfill provides most of the radon. If 

one assumes that the backfilling is done with the native soil, 

an estimate of the relative importance of the backfillsubslab aggregate zone and of the undisturbed ground as 

sources of radon may be made by comparing the width of 

the backfill with the interstitial mean migration distance. 

Table 1 lists the interstitial mean migration distances of 

radon calculated for different soil types from representative 

values of permeability and the interstitial effective diffusion 

coefficient. 

If the undisturbed ground typically is moist or wet 

clay, the interstitial mean migration distance is much less 

than the width of the backfilled zone, and the radon 

available to a structure should be determined by the backfill. It follows that use of backfill of low radium content 

should minimize radon availability to a structure in finegrained or typically very moist ground. If the undisturbed 

ground is fine grained and not normally very moist, both the 

undisturbed ground and the backfill should contribute sig-
_J 

u ' 

Q. 

z 

4 

g 3 <{ 

0:: 

~ 

g 2 

~ 

Q 

X I 

(.!) X • o ttl. 0 

_J 

LOG10 SOIL-GAS RADON {pCi/L} 

6 

;) 

E 

' tT 

5 Ill 

z 

0 

~ 0:: 

0:: 

0 

0 

0 

~ 

Figure 4. Comparisons of reported indoor radon 

concentrations with concentrations of radon in soil gas 

from boreholes near 10 houses (left graph) and with radon 

availability numbers calculated from data from the same 

_J 

' u 

Q. 

4 

z 

0 3 0 

<{ 

0:: 

0:: 

0 

g 2 

~ 

Q 

(.!) 

g 

X I 

• 0 t ••• 

2~----~3~====~4==~--~5~----~6------~7__J 

LOG10 RADON AVAILABILITY NUMBER (Bq/m3) 

6 

r<l 

E 

' tT 

5 Ill 

z 

0 

0 

<{ 

0:: 

4 0:: 

0 

0 

0 

~ 

Q 3 (.!) 

g 

2 

boreholes (right graph). like symbols joined by lines 

denote data from multiple boreholes at a given site. pCi/l, 

picocuries per liter; Bq/m3

, becquerels per cubic meter. 

Table 1. Calculated interstitial mean migration distances for radon-222 

[Unless otherwise noted, porosity, permeability, and diffusion coefficient values have been selected by the author as representative of the soil types 

indicated. An arbitrary driving pressure difference of 5 Pa (pascals) is assumed. The mean migration distances have been calculated by the method given 

by Tanner (1988) and divided by porosity to yield the interstitial mean migration distances] 

Permeability Diffusion Interstitial 

coefficient Porosity mean migration Soil type (k, in square (0*, in square meters (e) distance meters) per second) (in meters) 

Clay, wet ............................................ . 1 x 10-'6 2X 10-10 0.45 0.01 

Silty clay, moist ....................................... . 1 x 10_'5 7x 10-s .45 .18 

Silty sand ............................................ . 1 x 10-' 3 3x 10-7 .40 .39 

Silt ................................................. . 2X 10-13 2x 10-7 .40 .33 

Well-graded silty sand and gravel ......................... . 2X 10-12 4x 10-7 .35 .59 

Gravelly sandy loam, 4 weight percent water' .............. . 1.1 x 10_' 2 2. 7X 10-6 .35 1.2 

Uniform fine sand: 

17 weight percent water2 •••••.•••••.•..•••••••.•.•••••• 1 x 10-11 sx 10-7 .30 1.1 

8.1 weight percent water .............................. . 2x 10-11 5X 10-6 .30 2.1 

Well-graded sand and gravel ............................. . 1 x 10-10 4.5x 10-6 .20 4.0 

Uniform medium sand .................................. . 1 x 10-10 6x 10-6 .25 3.8 

Uniform coarse sand ................................... . 2X 10-9 6X 10-6 .25 15 

Clean gravel ........................................... . 10-9-10-7 7X 10-6 .20 101-102 

1 Data from Schery and others (1984). 2

Diffusion coefficients from Grammakov ( 1936). 

nificantly to radon availability. If the undisturbed ground is 

well-sorted sand or coarse material and is well drained, the 

backfill should be a minor source of radon. 

RADON MEASUREMENT METHODS 

The soil-probe methods discussed thus far use 

"active" methods of radon detection and counting, in that 

they extract the soil gas and measure its radon content. 

Another method that should be classified as active is the 

prompt counting of the gamma rays from bismuth-214 

e14Bi), a radon decay product, in hermetically sealed soil 

samples (Stieff and others, 1987); the method permits 

determination of both concentration and mobility of radon 

in the sampled soil. The active methods have the disadvantages of being expensive, requiring equipment costing 

Methods of Characterization of Ground for Assessment of Indoor Radon Potential at a Site 7 
$4,000 or more, and (except for the method of Stieff and 

others, 1987) of indicating the radon concentration and 

mobility in soil at the measurement time only. The equipment cost may be an acceptable capital cost to State and 

local government agencies, consultants, and engineering 

firms; moreover, having immediate answers is preferable to 

having to wait weeks to months for long-term measurements. However, many investigations of radon in soil are 

made with inexpensive "passive" methods, which include 

the etched-track (Alter, 1980), charcoal-adsorption 

(George, 1984; Hesselbom, 1985), and electret detectors 

(Kotrappa and others, 1988); methods of absorbing radon 

from soil gas into a liquid scintillation counting medium 

(Taipale and Winqvist, 1985; Fukui, 1987); and continuous 

gamma-ray monitoring of the space in a cylindrical cavity 1 

m in diameter by 1 m high filled with coarse rock of low 

radium activity (Rudakov, 1985a,b). 

Users of the passive methods have assumed that 

radon concentrations at the detectors are equal to the 

interstitial radon concentrations in undisturbed soil, but 

decay of radon during its movement to the detector cavity 

can reduce the concentration at the detector significantly 

(Tanner, 1991). The concentration of radon available to a 

passive detector can be estimated by considering diffusion 

of radon into an air-filled cavity from an infinite homogeneous ground. If diffusion in the ground is isotropic, the 

diffusion is as efficient as possible and proceeds along radii 

of an approximately spherical cavity. It can be shown that 

the ratio of the radon concentration at the center of the 

cavity to the undepleted radon concentration at infinite 

radius into the medium is the following function of the 

cavity radius, r, the porosity, e, the pore water fraction, m, 

the reciprocal of the radon diffusion length in air, a(0.42 

m- 1), and the reciprocal of the interstitial effective radon 

diffusion length in the medium, b: 

C0 e(1-m)a3r(br+ 1) 

Coo = b2ar cosh(ar)+ [e(l-m)a2(br+ 1)-b2

] sinh(ar) 

where cosh and sinh are the hyperbolic cosine and hyperbolic sine, respectively. A lower limit to the diffusion, as 

might prevail in an uncracked, highly anisotropic layered 

soil, can be estimated by diffusion along the radii of a 

vertical cylinder of the same radius. It can be shown that the 

ratio of the concentration in the cavity to that where it is 

undepleted follows the relation 

C0 = e(l-m)yV,: 

Coo e(l-m)VDm/0(ar)+yDJ1(ar)[K0(br)IK1(br)] 

where D is the interstitial effective diffusion coefficient, the 

subscript m referring to the medium and the subscript c 

referring to the cavity; I and K refer to modified Bessel 

functions of the first and second kinds, respectively; and the 

subscripts 0 and 1 refer to the orders of the Bessel functions. 

8 Field Studies of Radon in Rocks, Soils, and Water 

Figure 5 shows graphs of these relations for several different cavity radii and for interstitial effective diffusion lengths 

corresponding to the indicated degrees of pore water saturation. The graphs show that passive detectors in small 

cavities do not yield significant errors until the surrounding 

ground is nearly saturated but that meter-sized cavities yield 

errors even in moderately dry ground. Because of the rapid 

diffusion of radon in a continuous air medium, the concentration ratios for cavities of the radii shown differ by no 

more than 2 percent between the cavity centers and the 

cavity walls. The position of the detector in the cavity is 

therefore not important. 

Although the radon concentration in the soil gas in a 

cavity must be less than that in the soil itself, an increase in 

the pore water fraction can cause an increase in the radon 

concentration in the cavity, because radon is concentrated in 

the gas phase of a gas-water system. It is reasonable to 

assume that the rate of radon emanation into the pores of the 

medium is not reduced as the water fraction in the pores is 

increased. Reduction of the rate of emanation of radon from 

samples with increasing moisture content, as observed by 

Lindmark and Rosen ( 1985) and by Damkjaer and Korsbech 

( 1985), is likely due to the diminished rate of diffusion from 

the sample; Bates ( 1980) showed by computation that a 

period of 10 hours is needed to reach a steady-state flux 

of radon from a cylindrical sample of 9.2-cm length, 

3.843-cm radius, 0.2 porosity, 1X10-7

-cm2 permeability, 

and 10-2

-cm2/s diffusion coefficient (equivalent to about 90 

percent saturation) at 300 K. Because radon follows Henry's Law (Boyle, 1911), the concentration of radon in the 

water phase of the pore fluid is in temperature-dependent 

proportion to the partial pressure (or concentration) of radon 

in the gas phase. If it is assumed that equilibrium is quickly 

established between the phases and that there is no gain or 

loss of radon from the pores, the ratio of the concentration 

of radon in the gas phase to the (constant) average concentration of radon in the pores can be shown to be 

Cga/Cpores= 1/[m(R-1)+ 1], 

where m is the pore water fraction, and R is the ratio of the 

radon concentration in the water phase to that in the gas 

phase. R is dependent only on temperature in dilute solutions (Kofler, 1913). A composite curve showing determinations of R by several authors was presented by Rogers 

(1958, fig. 44); slightly different values can be derived 

from Harley and Terilli ( 1986). Figure 6 shows the radon 

concentration in the gas phase, normalized to unit average 

concentration in the pores, as the pore water fraction 

increases. 

The combination of enrichment of radon in the gas 

phase and increased decay of the radon along its path to a 

passive detector can result in apparent radon concentrations 

that are higher than, equal to, or lower than the actual 

average radon concentration in the pores, depending on the 

cavity size, the soil temperature, the pore water fraction, 
2.0 2.0 

RELATIVE TO RELATIVE TO 

RELATIVE TO 

AVERAGE PORE 

AVERAGE PORE AVERAGE PORE 

CONCENTRATION 

CONCENTRATION 

1.5 1.5 

RELATIVE TO 

SOIL GAS TO SOIL GAS 

0.5 0.5 0.5 

CAVITY RADIUS= 3cm 

POROSITY = 0.4 

TEMPERATURE= 283 K 

CAVITY RADIUS= 10 em 

POROSITY= 0.4 

TEMPERATURE= 283 K 

CAVITY RADIUS 

=50 em 

POROSITY= 0.4 

TEMPERATURE= 283 K 

o ~~~~~~~~~~~~ a~~~~--~~~~~~~~ 

0 0.5 1.0 0 0.5 1.0 

QL..-..-'--~--'----'----'~~......__.___._.::::-1 

0 0.5 1.0 

PORE WATER FRACTION PORE WATER FRACTION PORE WATER FRACTION 

Figure 5. Curves showing the error in estimation of radon 

concentration by passive detectors. The curves are based 

on diffusion models. All curves relate the radon concentration at the center of the passive-detector cavity to the 

radon concentration at a sufficient distance from the 

cavity (typically less than a few meters) to be unaffected by 

radon diffusion toward the cavity. The lower pair of curves 

in each frame relates the radon concentration at the cavity 

center to the undepleted radon concentration in the soil 

and the range and anisotropy of the diffusion coefficient. 

The active methods are affected by the enrichment of radon 

in the gas phase, but decay is negligible in transit to the 

sampling device; in principle the measurements can be 

corrected if the temperature and pore water fraction in the 

volume of ground sampled are known. 

SHORT-TERM METEOROLOGICAL EFFECTS 

Meteorological effects on radon concentrations in soil 

gas are discussed at length by Asher-Bolinder and others in 

another paper of this Bulletin, entitled "A Preliminary 

Evaluation of Environmental Factors Influencing Day-toDay and Seasonal Soil-Gas Radon Concentrations." Rainfall and snowmelt have several effects on the concentration 

of radon in soil pores and on the ease of radon migration. 

The short-term effects are greatest near the surface in most 

soils: if the ground surface is sealed, exhalation of radon to 

the atmosphere is nearly halted, the near-surface radon 

concentration builds up, and the ability of radon to migrate 

gas. The upper pair of curves in each frame relates the 

radon concentration at the cavity center to the amount of 

radon in both gas and water phases per unit pore volume. 

For each pair of curves, the upper curve was computed 

from a spherical diffusion model, and the lower curve was 

computed from a cylindrical diffusion model. The regions 

between the curves of each pair indicate the range of 

uncertainty due to variability of diffusion anisotropy. 

is drastically reduced. At depths greater than.1 m in most 

fine-grained soils, the immediate effects are that exhalation 

to the atmosphere is reduced but mobility is not reduced 

significantly. As the water percolates downward, the effects 

of enrichment of the gas phase and shortening of the mean 

migration distance should take place. Harley and Terilli 

( 1986) have noted radon "events" taking place in a house 

that are due to changing water vapor pressure in soil, as 

caused by temperature pulses, which can be induced by 

infiltration of rainfall that is warmer than the soil. These 

factors indicate that radon assessment procedures should not 

be conducted at depths much less than 1 m. 

SEASONAL EFFECTS 

Rudakov (1985b) reported a quasi-sinusoidal variation of mean monthly radon concentrations in 1-m-diameter 

cylinders filled with low-activity coarse rock in cavities 

between 1 and 2 m below the ground surface at two 

locations in central Asia, Soviet Union, over faults. The 

Methods of Characterization of Ground for Assessment of Indoor Radon Potential at a Site 9 
w 4 

a:: 

w 0 

en (l. 

<( 

z J: 

(l. 

z 

en 0 <( 

(!) .... 

<( z 0:: 3 

z .... 0 z 

L&J .... (.) 

<( z 

0:: 0 .... (.) 

z 

w z 

(.) 0 

z 0 2 0 <( 

(.) a:: 

z w 

0 (!) 

0 <( 

<( a:: 

0:: w 

> <( 

~~~~~~~~--~~--~--~~--~ 0 0.2 0.4 0.6 0.8 1.0 

PORE WATER FRACTION 

Figure 6. Curves showing the calculated ratio of the radon concentration in the gas phase of the pore space in soil to the 

average radon concentration in the pore space as a function of pore water fraction for 273 K (0 °C), 283 K (10 °C), and 

293 K (20 °C). 

maximum and minimum values occurred in January and 

July, respectively, and differed by a factor of four. The 

radon concentrations were inversely related to surface 

temperature and thermoplastic deformations and directly 

related to barometric pressure; they were inferred from 

gamma radiations from a radon decay product measured by 

detectors at the centers of the cylinders and were influenced 

by the in-transit radon decay shown in figure 5. 

Rose and others ( 1988) observed seasonal changes of 

radon concentration of a similar fourfold range, but of 

opposite phase, in a well-drained silt loam soil in central 

Pennsylvania. The measurements were made with passive 

etched-track detectors bu\r appear to have been verified by 

soil-gas extraction and counting in an alpha scintillation 

cell. 

Using the soil-probe instrumentation of figure 3, I 

measured the radon concentration in soil gas from a hole 1.2 

m deep in a moderately drained silt loam in Fairfax County, 

Va. Table 2 shows the variation of soil characteristics 

measured during different seasons. The fact that the radon 

concentration in the soil gas did not vary significantly may 

be a recommendation for the use of active measurement 

methods. At this site radon migration was dominated by 

diffusion, which is strongly affected by the pore water 

fraction. The pore water fraction and porosity were deter1 0 Field Studies of Radon in Rocks, Soils, and Water 

mined by packing a sample of the soil from the hole bottom 

in a canister and measuring the bulk density of the soil as 

collected and after desiccation. An indeterminate error is 

caused by failure to achieve the same bulk density in the 

canister as in the ground. The high porosity calculated for 

the measurements of October 31, 1988, may have res.ulted 

from insufficient pressure in packing the canister, which 

could have led to an underestimate of the pore water 

fraction and an overestimate of the diffusion coefficient, 

mean migration distance, and radon availability number. 

The ranges and qualitatively different results of measurements reviewed in this paper and by Asher-Bolinder 

and others in this Bulletin indicate that we cannot yet 

closely characterize soils for their indoor radon potential 

from measurements made at a single time. The principal 

difficulty is estimating the average pore water fraction of 

the soil over a few years' time. Alternatives to instantaneous, in situ measurements would be desirable. 

ACKNOWLEDGMENTS 

Development of a radon availability protocol was 

initially supported by the Office of Radiation Programs of 

the Environmental Protection Agency under Interagency 
Table 2. Characterization of soil at 1.2 m in depth at a site in Fairfax County, Va. 

[Data were obtained by means of procedures and calculations given in the protocol proposed by Tanner (1988); n.d., not determined] 

Soil characteristic 

Radon concentration (in nanocuries per liter) ................ . 

Pore water fraction ...................................... . 

Porosity .............................................. . 

Diffusion coefficient (10- 2 m2

/s) .......................... . 

Permeability (10- 13 m2

) •••••••••••••••••••••••••••••••••• 

Mean migration distance (in meters) ...................... . 

Radon availability number (in kilobecquerels per square meter) . 

Agreement No. DW14931927--0l--O. Investigation of gas 

transport in soils and its relation to radon availability was 

partly supported by the Office of Health and Environmental 

Research of the U.S. Department of Energy under grant 

DE-AI05-87ER60578. 

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Methods of Characterization of Ground for Assessment of Indoor Radon Potential at a Site 13 
APPENDIX A. DERIVATION OF THE RADON AVAILABILITY NUMBER (RAN) 

1. Quantities, symbols, units, and dimensions 

Quantity 

Activity concentration in interstitial fluid 

Diffusion coefficient (effective diffusion coefficient in 

interstitial fluid), D*=De/e. 

Diffusion coefficient (effective diffusion coefficient for 

geometrical area), De=e.D* 

Flux density 

Porosity 

Decay constant, Rn-220 (thoron) 

Decay constant, Rn-222 (radon) 

Mean life, Rn-222 (5.52 days) 

Depth (positive upward) 

Velocity of convection across geometrical area (Darcy 

velocity) 

Rate of radon generation into interstitial fluid 

Viscosity of air (absolute or dynamic) at 290 K 

Permeability 

Mean migration distance in geometrical volume 

2. Assumptions 

a. The ground can be modeled as a homogeneous, 

isotropic permeable medium. 

b. The interstitial (pore) spaces are large compared 

with the mean free path of the radon isotope. 

c. Absorption of radon into liquids in the pores and 

adsorption of radon by surfaces of the pores can be ignored. 

d. The gravitational term in Darcy's Law may be 

neglected; v is proportional to the pressure gradient in the 

interstitial gas and inversely proportional to the dynamic 

viscosity of the gas, the permeability being defined as the 

proportionality constant. 

e. Prior to the calculation of mean migration distance, 

the porosity, diffusion coefficient, and permeability have 

been determined. Procedures for obtaining these data were 

given by Tanner (1988). 

3. Calculation of mean migration distance 

W.E. Clements' dissertation (1974) introduced the 

parameters Nr and "', defined as follows: 

Nr=v/(2(e'A. De)¥2) (1) 

and 

(2) 

Clements' equation 2-24 gave the steady-state flux density 

of radon at the Earth's surface as 

(3) 

We multiply the left side of equation 3 by the mean 

life of radon, T, and divide the right side by its reciprocal, 

'A, to obtain the amount of radon exhaled during one mean 

life: 

(4) 

The left side corresponds to the radon availability number 

14 Field Studies of Radon in Rocks, Soils, and Water 

Symbol Value Units Dimensions 

c variable Bq/m3 L -3T-t 

D* variable m2

/s L2T-1 

De variable m2

/s L2T-1 

J variable Bq/m2 · s L -2T-2 

E. variable none none 

ATn 1.25x w- 2 /s T-1 

ARn 2.10Xl0-6 /s T-t 

,. 4.77X 105 s T 

z variable m L 

v variable m/s LT- 1 

G variable Bq/s · m3 L -3T-2 

J.1 1.s2x w- 5 Pa · s ML- 1T-1 

k variable m2 L2 

M variable m L 

(RAN). The expression G/'A. is the concentration of radon 

in the interstitial fluid at infinite depth (that is, where there 

is insignificant depletion by exhalation), and the remaining 

factor is the mean migration distance averaged over the 

geometrical volume (that is, the mean interstitial migration 

distance multiplied by the porosity). Then 

M="/(EDe!>...)¥2 (5) 

and 

RAN=C_"" M, (6) 

where C_oc is the radon concentration in soil gas at 

sufficient depth to be undepleted by loss to the atmosphere 

and M must be computed from equation 5. M cannot be 

calculated directly from the observed or estimated quantities, however, because the value of v, the Darcy velocity, is 

not directly known. It could be calculated from the Darcy 

relation 

v= -(k/JJ-)(dpldz) (7) 

if the pressure gradient were known, but the known quantity 

is the overall pressure difference, 5 Pa, to some distance 

from which migration is inconsequential (assumed to be 4.6 

times the interstitial mean migration distance, or the distance over which hundredfold diminution of a radon flux 

takes place); this depth is dependent on M, the quantity 

sought. The approach used is to assume that the pressure 

gradient, dpldz, is numerically equal to the pressure difference, to compute M, to compute the quantity 

(dpldz)(4.6 M /e) (8) 

and to recompute M using a larger or smaller value of 

pressure gradient until the above quantity approaches the 

value of -5 Pa to within 1 percent. 
APPENDIX B. DERIVATION OF RELATIONS AMONG PERMEABILITY, FLOW RATE, AND 

PRESSURES IN THE HEMISPHERICAL GEOMETRY OF THE SAMPLING HOLE 

1. Quantities, symbols, units, and dimensions 

Quantity 

Pressure 

Atmospheric pressure 

Pressure in sampling hole 

Volume 

Viscosity of air (absolute or dynamic) at 290 K 

Permeability 

Flow rate, volume basis 

Velocity of fluid flow across geometrical area (Darcy 

velocity) 

2. Assumptions 

a. The ideal gas law is sufficiently accurate to 

describe soil gas (air) in the absolute pressure range from 

near zero to atmospheric. 

b. Soil gas moves into the sampling hole isothermally; contact with soil grains is sufficient to furnish heat to 

the soil gas during the 10-minute sampling period to 

minimize cooling of the soil gas. 

c. Gravitational effects over the vertical range of a 

few meters are negligible. 

d. The ground is isotropic and of uniform porosity. 

e. The equation of continuity applies to the square of 

the pressure (or density); that is, the Laplacian of pressure 

squared (or gas density squared) equals zero. See, for 

example, Greenkom (1983, eq. 119 and 120), Bird and 

others (1960, eq. 4.1-7), or Muskat (1937, sec. 11.2, eq. 

1). 

f. The flow of soil gas into the waste and sampling 

cavities is separated by a horizontal plane passing through 

the midpoint of the lower packer; the flow is approximately 

hemispherical. 

g. The flow of soil gas is adequately represented by 

Darcy's Law. In very fine material, Darcy's Law becomes 

inaccurate, but the permeability is then negligibly small. 

h. Except for the disturbance of the pressure field 

created by the sampling, pressure in the ground is equilibrated with that in the near-surface atmosphere. Propagation of atmospheric pressure ·changes is slow in very fine 

materials, but their permeabilities are negligibly small. 

3. Derivation of the pressure function. 

Under the above assumptions, 

(1) 

For spherical flow in the radial direction in spherical 

coordinates the above equation may be reduced (see 

Muskat, 1937, sec. 5.2, eq. 2) to 

Symbols Value Units 

p variable Pa 

Pa Pa 

Pw Pa 

v variable m3 

~ 1.s2x w-s Pa · s 

k variable mz 

Qv variable m3

/s 

v variable rn!s 

which implies that 

d(p2) 

~=constant=c1 

( c 1) 

1

12 p= c2- r . 

Dimensions 

L3 

ML - 1T- 1 

L2 

L3T-1 

LT- 1 

(2) 

(3) 

(4) 

(5) 

(6) 

At r = infinity, the pressure is assumed to be that of 

the atmosphere; hence, 

(7) 

At r = radius of sampling hole, r w• 

(8) 

whence 

cl =r w(p;-p!) . (9) 

Let the difference of the squared pressures be represented by f. Then 

( 

2 r wY) 1

12 

p= Pa--r- · (10) 

In order to obtain the velocity of radial flow into the 

sampling hole we must obtain the pressure gradient, dp/dr, 

and evaluate it at the spherical surface of the hole: 

Methods of Characterization of Ground for Assessment of Indoor Radon Potential at a Site 15 
dp =!!:__( 2_rwY )¥2 

dr dr Pa r 

From equations 6 and 12, 

or 

(11) 

(12) 

(13) 

(14) 

4. Calculation of permeability from flow into the sampling 

hole 

Note that Darcy's Law applies to flow across a 

geometrical surface. The radial flow velocity is then proportional to the pressure gradient, 

-kdp v=-- J.l. dr · 

From equations 14 and 15, 

v= k rw(p~-p~) 

JJ. 2 p r2 

(15) 

(16) 

The volumetric flow into the sampling hole is the product of 

the radial flow velocity and the spherical surface area of the 

sampling hole: 

(17) 

Combining equations 16 and 17 and evaluating v at r= r w• 

16 Field Studies of Radon in Rocks, Soils, and Water 

(18) 

or 

-2 1T k rw (p~-p~) 

Qv J.l.Pw 

(19) 

For hemispherical flow, Qv is reduced by a factor of two, 

yielding 

-7r k rw (p~-p~) 

Qv J.l.Pw 

(20) 

where the minus sign indicates flow in the direction of 

decreasing radius (that is, inward to the sampling cavity). 

The permeability is then 

k Qv ~ Pw2 • 

1Trw(pa -pw) 

(21) 

Equation 21 may be modified by expanding the difference 

of squared pressures, 

(22) 

and observing that (pa-p"'.) is the pressure difference 

between the atmosphere and the sample space and that for 

small pressure differences (pa +pw) is approximately equal 

to 2pw: 

(23) 

which simplifies to 

(24) 

for hemispherical geometry or to 

k Qv J.l. 

4 1T rw(pa -pw) 

(25) 

for spherical geometry. 
APPENDIX C. DERIVATION OF RELATIONS AMONG PERMEABILITY, FLOW RATE, AND 

PRESSURES FOR RADIAL FLOW INTO A CYLINDRICAL SAMPLING HOLE 

1. Quantities, symbols, units, and dimensions 

Quantity 

Pressure 

Atmospheric pressure 

Pressure in sampling hole 

Volume 

Viscosity of air (absolute or dynamic) at 290 K 

Permeability 

Flow rate, volume basis 

Velocity of fluid flow across geometrical area (Darcy 

velocity) 

Radius of sampling cavity 

Height of sampling cavity 

2. Assumptions 

a. The ideal gas law is sufficiently accurate to 

describe soil gas (air) in the absolute pressure range from 

near zero to atmospheric. 

b. Soil gas moves into the sampling hole isothermally; contact with soil grains is sufficient to furnish heat to 

the soil gas during the 10-minute sampling period to 

minimize cooling of the soil gas. 

c. Gravitational effects over the vertical range of a 

few meters are negligible. 

d. The ground is isotropic and of uniform porosity. 

e. The equation of continuity applies to the square of 

the pressure (or density); that is, the Laplacian of pressure 

squared (or gas density squared) equals zero. See, for 

example, Greenkom (1983, eq. 119 and 120), Bird and 

others (1960, eq. 4.J-7), or Muskat (1937, sec. 11.2, eq. 

1 ). 

f. The flow of soil gas into the sampling cavity is 

bounded by horizontal planes passing through the midpoints 

of the packers above and below the sampling cavity; the 

flow is along radii of the cylindrical cavity. 

g. The flow of soil gas is adequately represented by 

Darcy's Law. In very fine material, Darcy's law becomes 

inaccurate, but the permeability is then negligibly small. 

h. Except for the disturbance of the pressure field 

created by the sampling, pressure in the ground is equilibrated with that in the near-surface atmosphere. Propagation of atmospheric pressure changes is slow in very fine 

materials, but their permeabilities are negligibly small. 

3. Derivation of the pressure function 

Under the above assumptions, 

(1) 

For flow in the radial direction in cylindrical coordinates the 

above equation may be reduced (see Muskat, 1937, sec. 

4.2, eq. 3) to 

Symbol 

p 

Pa 

Pw 

v 

J.1 

k 

Qv 

v 

rw 

h 

Value Units 

variable Pa 

variable m3 

1.82X 10-5 Pa · s 

variable mz 

variable m3/s 

variable m/s 

variable m 

variable m 

! ~(/ (pz))=o r dr dr ' 

which implies that 

J d(p2)=c1 J~dr 

p

2

=c1ln(r)+c2 . 

Dimensions 

ML - 1T- 2 

L3 

ML - 1T- 1 

Lz 

L3T-1 

LT- 1 

L 

L 

(2) 

(3) 

(4) 

(5) 

Equation 5 may be evaluated at the boundary conditions r=rw, p=pw at the surface of the cylindrical cavity 

and p=pe at some radius re into the ground: 

p;=c 1 ln(re)+c2 

p!=cl ln(r w)+c2 . 

Subtraction of equation 7 from equation 6 yields 

(6) 

(7) 

(8) 

and substitution of the right side of equation 8 for c 1 in 

equation 7 yields 

p!ln(re)-p;ln(r w) 

ln(r )rw) (9) 

By taking the square root of equation 5, we obtain the 

pressure distribution as a function of radius, 

1 

p=[c 1 ln(r)+c2]t2 (10) 

from which the pressure gradient is 

or 

1 

dpldr=c 112r [c1 ln(r)+c2 ]12 (11) 

Methods of Characterization of Ground for Assessment of Indoor Radon Potential at a Site 17 
If equation 12 is evaluated at the boundary of the sample 

cavity (r=r w), 

d /d (p;-p:,) 

P r 2r wOn(r/r w)[p;(ln(r Jr w))-p~(ln(relr w))]) 112 (13) 

(14) 

2r wPw0n(r/r w) . (15) 

4. Calculation of permeability from flow into the sampling 

hole 

Note that Darcy's Law applies to flow across a 

geometrical surface. The radial flow velocity is then 

proportional to the pressure gradient, 

v = -(kiJL)(dp/dr) . (16) 

From equations 15 and 16, 

v= 

k (p=-p~) 

JJ-2r wPwln(r /r w) · (17) 

To obtain the total volumetric flow rate across the 

boundary, we multiply the flow velocity by the cylindrical 

surface area, 21Tr wh, obtaining 

Q = k'lTh(p;-p:,) 

v JJ.Pwln(r /r w) ' (18) 

where the minus sign indicates flow in the direction of 

decreasing radius (that is, inward to the sampling cavity). 

The permeability is then 

18 Field Studies of Radon in Rocks, Soils, and Water 

QvJJ.Pwln(r/r w) k 2 2 • 'lTh(pe -pw) (19) 

Equation 19 may be simplified by expanding the 

difference of squared pressures, 

(20) 

and observing that (pe -pw) is approximately equal to the 

pressure difference between the atmosphere and the sampling space and that for small pressure differences (p e + Pw) 

is approximately equal to 2 Pw: 

(21) 

which simplifies to 

(22) 

Equation 22 corresponds to the expression for flow of 

an incompressible fluid. In either case, the radius re is not 

easily established. It cannot be extended to infinity, because 

ln(r/r w) also becomes infinite. However, because re is not 

dependent on soil type, and because the effect of the 

sampling becomes inconsequential at a distance of the order 

of 10 m or less, an arbitrary selection of re= 10 m is 

reasonable. At such distance, Pe is very close to atmospheric pressure under assumption h, above, and (pe -pw) 

may be referred to atmospheric pressure, as is the practice. 

The factor ln(re/r w) is not sensitive to variation of r w in a 

practical range. 
SIMPLE TECHNIQUES FOR SOIL-GAS AND WATER SAMPLING FOR RADON ANALYSIS 

G.M. Reimer 

Abstract 

Various devices and techniques are available for 

sampling soil air and ground water for analysis of their gas 

content. A simple approach to collection is presented 

here and can be useful as a screening technique for radon 

when analyses are desired at the field location. For soil-gas 

samples, a small-diameter probe is pounded into the 

ground to a depth of at least 0.75 meter. For water, a 

plastic bottle containing the sample is shaken so headspace air purges the gases from the water. Once the gas 

samples are extracted from the soil or water, they can be 

analyzed with whatever field technique is desired. 

INTRODUCTION 

Measured soil-gas and ground water concentrations 

of radon (Rn) are important parameters needed to evaluate 

the radon potential in any location. Preliminary field measurements often are important when designing a larger 

program to assess the radon potential. Simple techniques 

and materials for soil-gas sampling and water sampling that 

can be used for screening are described. Although these 

techniques are not part of any protocol for sampling, they 

are in general use by different programs within the U.S. 

Geological Survey. These methods can be used for some 

aspects of research to understand the distribution and 

migration of radon. They also can be easily modified to suit 

a variety of analytical schemes and instruments. 

SOIL-GAS SAMPLING TECHNIQUE 

Soil-gas sampling is an integral part of the scientific 

methodology used to understand the distribution, migration, 

and availability of radon gas. Many factors affect the 

concentration of radon in soil, such as the radium concentration, the emanation characteristics of the soil materials, 

the soil porosity, permeability, and moisture content, and, 

of course, meteorological conditions. Similarly, many factors come into play when collecting a sample of the soil gas 

for analysis. Samples typically are collected by augering a 

hole or driving a probe into the soil. A detector is set in the 

hole for a time-integrated analysis to measure radon concentrations emanated from the soil, or pumping is performed in some fashion to obtain a sample for a more 

instantaneous analysis of pore-space radon. By their very 

nature, all these methods disturb the soil environment to 

some degree, and they sample different regimes of the soil 

air. Therefore, the selection of a specific soil-gas sampling 

method is based upon some compromises such as requirements for a special sample size, the need for unique 

pumping or pressure differential requirements, or the need 

for sampling at a particular soil horizon or depth. 

The sampling method described here has many 

advantages for a typical sampling program where the 

relative distribution of radon concentrations is sought for 

the surficial environment. This method has evolved, like so 

many others, from the uranium exploration programs of the 

past. It has advantages and limitations, but both can be 

defined. The technique involves pounding a small-diameter 

hollow steel probe into the ground and using a hypodermic 

syringe for collecting the sample. This approach is very 

accommodating for samples to be analyzed on an electronic 

alpha-particle scintillometer. The advantages of this method 

are that it provides for fast sampling, only a small quantity 

of sample needs to be collected, and there is minimal 

disturbance to the soil environment. The same collection 

system can be used for determining the soil permeability of 

the sample site. It also measures the actual in situ porespace concentration of radon that can then be used more 

directly for radon availability measurements. The primary 

disadvantage is that it is a "grab sample," which defines the 

concentration only for the environmental and meteorologic 

conditions that exist at the time of collection. 

Description of Soil-Gas Sampling Equipment and 

Technique 

The basic equipment is of simple design made from 

easily obtainable supplies. Size and grade of the materials 

used are not critical, but some guidelines are offered. 

Considerations concerning the type of sampling to be 

performed contribute to the specific design of the sampling 

equipment. In this case, for example, there are criteria for 

minimum disturbance to the sampling environment. The 

probe should be durable and should not clog easily when 

used in a variety of soil types; the sampling system should 

be portable to permit fairly rapid sampling at remote areas. 

In such a system, as shown in figure 7, the probe is 

small-diameter, thick-walled carbon steel tubing. The outside diameter can range from 6 to 9 mm (millimeters) and 

the inside diameter from 2 to 3 mm. Sizes in this range give 

the best strength and ease of emplacement. The length of 

the probe can also vary, but typically 0. 75 to 1.0 m (meter) 

is chosen for the depth from which samples are taken. This 

depth is one below which major influences from meteorological variables are found and one that frequently encounters the upper B or lower C soil horizon (Reimer, 1980; 

Hesselbom, 1985). The carbon alloy used is somewhat 

limited because of availability in the thick-walled tubing; 

usually the available grades are 1015, 1018, or 1020. Other 

Soil-Gas and Water Sampling for Radon Analysis 19 
SPLIT HAMMER 

PROBE TIP 

Figure 7. Soil-gas sampling probe showing the tip and 

needle guide components. 

alloys would provide greater strength but are available only 

in quantities that make an acquisition expensive. Stainless 

steels are softer than the carbon alloys but are used for 

applications where a permanent probe for long-term 

monitoring is desired. 

The probe is emplaced into the ground by pounding. 

To accomplish this, two pounding collars 3 em 

(centimeters) in diameter and 5 em in length are soldered 

onto the probe. They are separated by a distance of about 60 

em to permit a split, barbell-shaped deadweight to be used 

as a sliding hammer. The hammer is made from machined 

steel about 18 em in length, 6 em in diameter' and weighing 

about 2 kg (kilograms). The split shape allows it to be fitted 

over the probe, and it is held together with machine screws. 

Many designs of the probe tip are possible, and two 

are described. In the first, a small machine screw is 

threaded into the lower end of the probe to prevent dirt from 

entering. There is no need to use a pointed end on 

small-diameter probes because several uses would quickly 

dull the end. About 2 em above the tip, the opposite sides 

of the probe are ground flat by removing 0. 5 mm of material 

for a 4-cm length to provide a zone of reduced diameter. 

20 Field Studies of Radon in Rocks, Soils, and Water 

Four or five sets of holes are drilled through this flat area; 

the diameter of the holes should be about equal to the inside 

diameter of the probe. A wire can be inserted into the probe 

to prevent dirt from entering the side holes. It serves to 

reduce the dead volume as well when collecting the sample 

but can be removed, if desired. A second probe tip design 

is one in which no flats or side holes are used. A rivet is put 

in the sampling end of the probe, and the probe is pounded 

into the ground. At the desired sampling depth, the probe is 

retracted a few centimeters by upward pounding. This 

action creates a cavity at the end of the probe. This 

particular design is sometimes useful for obtaining a sample 

when very high soil-moisture contents or fine silts are 

encountered. It also is a way to reutilize a side-hole probe 

on which the end has fatigued and broken. 

The sample is taken from the open end of the probe. 

Tubing can be slipped over the end and a sample pumped to 

a detector, or an 0-ring fitting containing a septum can be 

secured over the end to permit a discrete volume to be 

collected in a hypodermic syringe. Either extraction system 

should be able to purge the probe of air before the sample is 

collected. Because of the thick-walled steel, a 1-m probe 

has an internal volume of only 3 cm3 (cubic centimeters), so 

extracting 10 cm3 from it is sufficient for a thorough purge. 

Samples can be stored in the syringes as long as the needle 

is capped to prevent gas loss or exchange. Tests with helium 

have shown that the syringes are capable of retaining the gas 

for a period of several days before diffusion would cause 

dilution (Reimer and others, 1979). Fittings and tubes 

commonly are supplied in English dimensions. The tube 

size typically available is 5

116 in (inch) outside diameter, 

0.092 in inside diameter, and the 0-ring fitting is lf4 in. The 

top end of the probe must be machined to a 1/4-in diameter 

for the 0-ring fitting. 

Discussion 

The probe design described above had been developed in 1974 and was subsequently modified for testing the 

possibility of sampling soil gases as a means of detecting 

energy resources. It has proven to be durable and reliable in 

a variety of soil environments. The small diameter causes 

minimal disturbance to the soil environment and provides 

self-sealing without the need for a packer system. The depth 

to which soil gases are sampled to minimize atmospheric 

influences is a matter of debate. Strength of the steel limits 

the practical length of the probe that can be pounded into the 

ground, usually to 1.5 m. For greater depths, a pilot hole 

could be made or the probe could be drilled into the ground. 

This basic design can be adapted to permit a number of 

modifications or alternate uses. For example, the choosing 

of the tip design, as mentioned previously, is such a 

modification, and determining the permeability from differential flow and pressure rates is an additional use. It has also 
been used for injecting gases in the soil for gas migration 

studies (Reimer, this volume). 

WATER SAMPLE COLLECTING TECHNIQUE 

Because natural concentrations of radon in water 

extend over many orders of magnitude (Graves, 1987), 

precise analyses are not necessary to categorize the general 

distribution of radon. A method has been developed for the 

rapid extraction and determination of the radon concentration in water. This technique is an ideal screening method 

for field operations where the qualitative determination of 

the radon concentration is acceptable and the results are 

desired at the field sampling site. Obtaining a representative 

sample is not a trivial procedure, however. The method 

described here involves collecting a sample that has been 

exposed to the atmosphere, such as from a spring or from 

ground water that has been pumped from a well. Agitation 

or natural effervescence can strip gases from the water. 

When water is obtained from wells, the sample should be 

secured from the water line before it has entered a pressurized holding tank. Even with the greatest of care, some gas 

loss is probably inevitable, and the concentrations should be 

considered as minimum values. 

Description of Water Sample Collecting 

Equipment and Technique 

The equipment for gas extraction consists of a standard 1-L (liter) plastic bottle and a modified cap (fig. 8). 

The cap is constructed of a hard plastic and is machined and 

threaded to fit the top of the bottle. The only critical step in 

machining is to ensure that the cap creates a seal with the 

opening of the bottle and not the shoulder or neck of the 

bottle. The cap is also machined to accommodate a fitting 

that contains a septum through which a hypodermic needle 

can be inserted to extract a sample from the closed bottle. 

The bottle should be marked in the fashion of a 

graduated flask or beaker so that various quantities of water 

introduced can be measured. Typically, water samples of 

750 cm3 are collected in the bottle. The exact quantity is not 

critical, and volumes within 30 cm3 of this nominal amount 

are sufficient. Continuous addition or removal of water to 

achieve the desired volume should be avoided because 

turbulence causes degassing of the water. The ratio of the 

water to headspace can be determined later. The bottle is 

then capped and shaken vigorously for 30 seconds. The 

agitation strips the dissolved gases from the water into the 

heads pace air of the bottle. The bottle should then stand for 

2 minutes to allow most of the bubbles in the water to 

combine with the heads pace air. A hypodermic syringe is 

inserted through the septum on the cap, the bottle is 

squeezed to force some heads pace air into the syringe, and 

the syringe is then removed and the needle capped. The 

SEPTUM HOLDER 

LUCITE CAP 

• 1·LITER BOTTLE 

Figure 8. Water sampling container showing the cap and 

septum holder. 

quantity of gas introduced into the syringe can be selected to 

suit the type of analytical equipment used and the required 

accuracy of the measurement. Typically, sample sizes in the 

range of 10 to 50 cm3 are sufficient. The sample can be 

analyzed immediately after collection if a field-portable 

instrument is available. If, indeed, the analysis can be 

performed in the field, a short delay time, less than 1 or 2 

minutes, from collection to analysis, usually permits 220Rn 

(thoron) to be analyzed. 

Field analytical instruments are commonly alpha 

scintillometers that contain a phosphor-coated cell. The 

cells should be sealed and capable of holding a vacuum. 

Evacuating the cell to a fixed pressure before sample 

injection permits a small sample to be quantitatively introduced and, in tum, minimizes contamination of the cell 

with the radon daughters, especially when high concentrations of radon are encountered. Such a system has been 

described by Reimer (1977). It allows the repeated use of a 

single cell for an extended period before the cell background becomes significant. Each scintillometer should be 

calibrated, and the efficiency of the gas extraction system 

should also be compared to a standard such as can be 

prepared from a known amount of radium salts dissolved in 

water. The concentration of the radon in the sample is 

directly related to the quantity of water collected and the 

output of the analytical device. For first-order approximations of the concentration, even the temperature of the water 

can be ignored but should be considered for the final 

determinations. 

Soil-Gas and Water Sampling for Radon Analysis 21 
Summary 

The sampling system described here is a simple 

version and is based on the same principle of the bubbler 

technique commonly used to strip gases from liquids. The 

advantages of this system are its low cost, simplicity of use, 

rapid availability of the results, ease of modification for 

collecting waters from a variety of sources, and the capability to analyze for dissolved thoron. The primary disadvantage is the sacrifice of analytical precision and accuracy 

to limits of perhaps 20 percent. This disadvantage is usually 

not a restrictive factor as long as order-of-magnitude variations are considered sufficient resolution. 

22 Field Studies of Radon in Rocks, Soils, and Water 

REFERENCES CITED 

Graves, B., ed., 1987, Radon, radium, and other radioactivity in 

ground water: Chelsea, Mich., Lewis Publishers, 570 p. 

Hesselbom, A., 1985, Radon in soil-gas: A study of methods and 

instruments for determining radon concentrations in the 

ground: Sveriges Geologiska Undersokning Arsbok, ser. C, 

no. 803, p. 1-58. 

Reimer, G.M., 1977, Fixed-volume gas inlet system for an 

alpha-sensitive cell adapted for radon measurement: U.S. 

Geological Survey Open-File Report 77-409, 3 p. 

---1980, Use of soil-gas helium concentrations for earthquake 

prediction: Limitations imposed by diurnal variation: Journal 

of Geophysical Research, v. 85, p. 3107-3114. 

Reimer, G.M., Denton, E.H., Friedman, I., and Otton, J.K., 

1979, Recent developments in uranium exploration using the 

U.S. Geological Survey's mobile helium detector: Journal of 

Geochemical Exploration, v. 11, p. 1-12. 
A PRELIMINARY EVALUATION OF ENVIRONMENTAL FACTORS INFLUENCING 

DAY-TO-DAY AND SEASONAL SOIL-GAS RADON CONCENTRATIONS 

Sigrid Asher-Bolinder, Douglass E. Owen, and R. Randall Schumann 

Abstract 

A long-term study of radon concentrations in a 

smectitic soil of the semiarid Colorado Piedmont reveals 

that interaction of meteorologic, climatic, and pedologic 

factors affects radon concentrations on both a daily and 

seasonal time scale. Seasonal variations are generally of 

greater magnitude than day-to-day fluctuations. Day-today radon fluctuations in this soil are controlled largely by 

changes in barometric pressure and by shallow capping 

effects resulting from precipitation. Change in gas permeability due to variations in soil moisture is the major 

control on seasonal soil-gas radon variation. Radon concentrations correlate with wind speed, relative humidity, 

air and soil temperatures, and the difference between 

those temperatures. Because these factors are interrelated, it is difficult to determine the magnitudes of their 

individual influences. Therefore, the nature of a soil and 

its response to climate must be understood if short-term 

measurements are to be used to predict long-term ranges 

of soil-gas radon concentrations. 

INTRODUCTION 

Soil-gas radon concentrations at a given locale are 

controlled largely by the interaction of geologic, pedologic, 

climatic, and meteorologic factors through time. Field 

studies (Gundersen and others, 1988; Schumann and Owen, 

1988) have shown that a strong relation exists between 

geology and radon in soil gas. Field measurements for such 

studies are usually carried out within a few weeks or one 

season, so measurements are not affected by seasonal 

variations. From site to site, however, mineralogy, chemistry, structure, and moisture content of soil affect radon 

levels in soils developed on a single geologic unit. In 

addition, radon levels measured at a site in July are not 

necessarily predictive of radon levels in January. If prediction of the yearly range of soil-gas radon values from 

short-term sampling is to become possible, the soil and 

climatic factors controlling soil-gas radon must be understood adequately. 

This report provides a preliminary interpretation of 

climatic, soil moisture, and meteorologic controls on radon222 concentrations in soil gas in the semiarid environment 

of the Colorado Piedmont. We did not distinguish between 

the radon-generation and radon-transport processes that 

influence radon concentrations in the soil gas at the site, but 

we have attempted to identify the day-to-day (short-term) 

and seasonal (long-term) controls on those measured soilgas radon concentrations. To identify and describe these 

controls, climatic, moisture, and weather effects on soils 

developed in this geologic setting were measured and 

studied. 

THE IMPORTANCE OF TIME SCALES 

In assessing the effects of climatic and weatherrelated factors on soil-gas radon concentrations, it is 

important to note that different factors are dominant, 

depending on the time scale under consideration. In this 

discussion we will consider three time scales: geologic 

time, seasonal time, and daily time. 

Geologic time is here defined as the time period 

during which soil-forming processes take place. These 

processes commonly require hundreds to thousands of 

years. On this scale, climatic and geologic characteristics 

are of primary importance in determining the amount and 

distribution of radon source material (radium), particle size 

and distribution, emanating power, porosity, moisture 

retention characteristics, whether or not leached mineral 

horizons or soil-grain coatings are present, and other 

weathering characteristics that control soil-gas radon 

concentrations. Because our observations span a short 

period of geologic time, these factors can be assumed to be 

constant for the purposes of this study. 

Seasonal time refers to one complete cycle of 

seasonal changes, generally equivalent to 1 year. Shorter 

term (day-to-day) fluctuations may be superimposed on the 

larger scale seasonal variations that occur during the span of 

a year. Likewise, the daily time scale refers to changes that 

can take place over time periods of less than an hour to 

several days. This is the period of time during which 

weather phenomena including precipitation, barometric and 

temperature changes, and wind effects take place. Changes 

that occur during daily time may be referred to as dayto-day fluctuations. 

The concept of daily time scales, as used in this 

paper, must not be confused with the concept of diurnal 

vanatwn. Diurnal vartatwns in soil-gas radon 

concentrations have been noted by several researchers 

(Wilkening and Hand, 1960; Tanner, 1964; Schery and 

others, 1984) and are related to the regular variations in air 

and soil temperature, air pressure, and humidity caused by 

insolation during day-night cycles. However, because this 

phenomenon is relatively well known and well documented, 

we focused our investigation on identifying and describing 

those factors that cause day-to-day fluctuations and seasonal 

variations in soil-gas radon concentrations. 

Environmental Factors Influencing Soil-Gas Radon Concentrations 23 
PREVIOUS STUDIES 

Although geologic factors are primary controls of 

radon concentrations in soil gas, there are a number of 

climatic and meteorological controls as well. A survey of 

published literature indicates that the dominant nongeologic 

variables influencing radon soil-gas concentration are soil 

moisture, precipitation, barometric pressure, soil temperature, air temperature, wind, and capping effects. A summary of the historical findings on the effects of each of these 

factors follows. 

Soil Moisture and Precipitation 

Previous investigators observed that soil moisture has 

a major impact on observed soil-gas radon concentrations. 

Radon emanation rates increase with an increase in soil 

moisture of up to 15 to 17 percent by weight; at greater 

moistures, the observed emanation rate decreases (Damkjaer and Korsbeck, 1985; Lindmark and Rosen, 1985). 

Water is the most important agent in enabling radon to 

escape from solid material, because the water surrounding 

the soil particles absorbs the kinetic energy of the radon 

atom's recoil and prevents the radon atom from burying 

itself in an adjacent soil grain (Tanner, 1980). Further 

increases in soil moisture beyond 15 to 17 percent cause 

decreasing diffusion lengths of the radon atoms, because 

they must travel through thicker films of pore water 

(Damkjaer and Korsbeck, 1985; Lindmark and Rosen, 

1985). 

Lindmark and Rosen ( 1985) found that a twofold to 

fivefold increase in soil-gas radon concentration was common between dry and optimal ( ~ 15 percent) water content, 

but they observed an increase as great as 30 times in some 

soils. Baranov and Novitskaya (1960; cited by Mattsson, 

1970) observed an increase in emanation of radon from 

uranium minerals when the humidity of the air increased. 

Barometric Pressure 

Low barometric pressure causes an increase in soilgas radon concentration in the upper few meters of soil. 

Low pressure causes soil gas to rise toward the surface from 

greater depths, where the soil-gas radon concentrations are 

generally higher because of less dilution by atmospheric air. 

High pressure has the opposite effect and pushes atmospheric air into the ground, diluting the soil gas (Kovach, 

1945; Kraner and others, 1964; Miller and Ostle, 1973; 

Klusman and Webster, 1981; Jaacks, 1984; Schery and 

others, 1984; Hesselbom, 1985; Lindmark and Rosen, 

1985). 

Kraner and others (1964) noted barometric influences 

on soil-gas radon concentrations to a depth of 96 in (inches). 

Kovach (1945) observed variations caused by barometric 

24 Field Studies of Radon in Rocks, Soils, and Water 

pressure to a depth of 2m (meters). Jeter and others (1977) 

calculated that influences of barometric pressure would be 

noticeable at a depth of 20 m in highly permeable material 

and that these fluctuations would be smaller than, and lag 

behind, those at shallower depths. Holkko (1987) found that 

changes in barometric pressure can cause convective flow 

of soil gases. Barometrically induced soil-gas motion may 

be equally as effective as molecular diffusion in transporting radon in soil (Robertson, 1969). Bakulin (1971) found 

that a decrease in pressure increases radon exhalation 

"proportional to the square of the pressure drop rate, [and to 

the] square of the gas permeable soil layer depth, and [it] 

increases linearly with time." Clements and Wilkening 

(1974) found that pressure changes of 1 to 2 percent 

associated with the passage of weather fronts could produce 

changes of 20 to 60 percent in the radon flux, depending on 

the rate of change of pressure and its duration. 

Soil Temperature and Air Temperature 

Observations concerning the effect of soil temperature on radon concentrations conflict. Some authors suggest 

that soil temperature has little or no effect on soil-gas radon 

content (Kovach, 1945; Lindmark and Rosen, 1985). However, according to Ball and others ( 1983), "Radon concentration correlates with soil temperature and to a lesser extent 

with air temperature." Kovach (1945) observed higher 

radon emanation during temperature lows. Jaacks (1984) 

observed negative correlations between both soil and air 

temperature and radon concentrations and noted that temperature gradients within the soil, or between the soil and 

air, can induce convective soil-gas transport. 

The conflicting observations of temperature effects 

may be due in part to the complexity of the relationships 

between meteorologic factors. A particular temperature 

change may be accompanied by changes between dry and 

wet conditions, a stable or unstable pressure regime, or 

variable winds. Thus, the effects of temperature may be 

difficult to separate from the effects of other factors that 

exert a greater influence on the soil-gas radon concentration. 

Wind 

Gusting winds cause a decrease in soil-gas radon 

concentrations because soil gas is being diluted or removed 

at the surface (Smyth, 1912; Kovach, 1945; Kraner and 

others, 1964; Miller and Ostle, 1973; Jaacks, 1984; Hesselbom, 1985; Lindmark and Rosen, 1985). Kovach (1945) 

observed wind effects to a depth of 150 em (centimeters). 

Kraner and others ( 1964) noted wind effects at 70 in but 

none at 90 in. In addition to wind velocity, the following 

factors affect the magnitude and depth to which the wind 

can exert an influence: soil permeability, the amount of 
moisture in the soil, the type and amount of ground cover, 

extent of snow and ice cover, and water frozen in the 

ground. Holkko (1987) suggests that winds can cause 

soil-gas flow in coarse-grained soil. Hesselbom ( 1985) and 

Pearson and Jones (1966) attribute the pumping effect of the 

wind to its turbulence or to fluctuations in wind speed. 

Wind turbulence can be caused by updrafts and downdrafts 

produced by atmospheric convection or by wind shear 

(Neiburger and others, 1973). The turbulence and fluctuations cause pumping by alternating between pressurization 

and depressurization of the soil. This effect is similar to that 

caused by barometric pressure changes. Venturi effects may 

draw gases out of the soil when the wind blows across 

desiccation cracks or open pores. 

Capping 

High soil moisture can lead to the swelling of 

expandable lattice clays (smectites), and this swelling 

lowers the permeability of the soil in those zones. As pores 

fill with water, the gas permeability is progressively 

reduced. As the top layer of the soil becomes saturated, 

soil-gas flow is restricted, and a cap that prevents mixing of 

soil gas with the atmosphere forms. This capping may 

reduce or block the effects of barometric pressure or wind 

on soil-gas radon concentrations. Kraner and others (1964) 

found that heavy precipitation could produce a cap that 

caused radon concentrations to reach levels in the near 

surface equal to those found at greater depths. 

Also, water frozen within the soil can produce an 

effective cap that retards radon flux to the atmosphere; an 

increase in soil-gas radon concentrations results (Kovach, 

1946; Jaacks, 1984; Hesselbom, 1985; Lindmark and 

Rosen, 1985; Taipale and Winqvist, 1985). Kovach (1945), 

for instance, found that the highest soil-gas radon concentrations of the year occur when the ground is frozen, an 

example of the effectiveness of capping in the upper layers 

of the soil. 

SITE DESCRIPTION 

A long-term radon monitoring site was established on 

the grounds of the Denver Federal Center in Lakewood, 

Colo. (fig. 9). The site is located on flatlying, undisturbed, 

and unirrigated land subject only to the foot traffic of the 

investigators and a twice-yearly mowing of the sparse 

grasses that constitute the ground cover. The site is typical 

of many areas of the Western United States on which 

housing is constructed. The soil developed on a lower 

terrace or pediment deposit of the Verdos Alluvium (Lindvall, 1978). This Pleistocene alluvium is derived largely 

from the weathering and transport of material from the 

Denver and Arapahoe Formations, which, in tum, were 

derived from granitic and gneissic terrane. The soil, a 

Figure 9. Study site at the Denver Federal Center. Three 

soil-gas probes are in the center; the 100-cm probe is 

encased in PVC pipe. 

Denver-Urban land complex, "formed in calcareous clayey 

material derived from mudstone and shale" (Soil Conservation Service, 1983, p. 44) and is smectitic, hard, and 

pebbly; it contains calcium carbonate streaks and is subject 

to deep cracking when dry. "Permeability of this Denver 

soil is slow. The available water capacity is high. . .. The 

shrink-swell potential is high. Rock fragments make up 0 to 

15 percent of the volume" (SCS, 1983, p. 45). Denver 

series soils commonly have a "well developed argillic B 

horizon and commonly have secondary accumulations of 

calcium carbonate, which indicate relative stability in 

respect to erosion and to further deposition. This parent 

material was deposited primarily as transported mantle over 

older surfaces as alluvium, colluvium, and loess" (SCS, 

1983, p. 234). 

The site is 1, 715 m above sea level and is located in 

the semiarid, temperate, continental climatic zone (Hansen 

and others, 1978). The area of the study site has a mean low 

January temperature of -9 to -7 °C (degrees Celsius) and 

has a mean high July temperature of 23 to 27 °C. Mean 

dates of first and last frosts are October 4 and May 11. 

Mean annual precipitation is 36 to 41 em, including 125 to 

140 em of snowfall, and mean annual evaporation is 125 to 

150 em. About 70 percent of the annual precipitation falls 

between April and September. Mean annual relative humidity is 50 to 55 percent. Sixty to 62 percent of the days are 

defined as clear (less than 30 percent of the sky is cloud 

covered). Wind speeds of 3.5 to 5.5 meters per second 

occur more than 35 percent of the time in the Denver area, 

with highest velocities occurring in May and November. In 

summary, there are "strong seasonal variations for most 

weather elements" (Hansen and others, 1978, p. 58) in the 

area that includes this study site. 

Environmental Factors Influencing Soil-Gas Radon Concentrations 25 
METHODS 

Soil gas was generally collected once each weekday 

from stainless steel probes permanently installed at 50, 75, 

and 100 em below the study site's soil surface. The 

technique and equipment described by Schumann and Owen 

( 1988) were used. During the first 3 months of the study, 

only the 100-cm probe was installed. The 50- and 75-cm 

probes were later installed to provide a more complete 

radon-depth profile. Soil gas was usually collected within 

the time interval of 10 o'clock a.m. to 2 o'clock p.m. to 

limit diurnal effects on radon concentrations. Radon concentrations in the soil gas were measured by use of an EDA 

RDA-200 radon detector, and the counts recorded by the 

instrument were converted to picocuries per liter (pCi!L) by 

use of a calibration equation. Barometric pressure, soil 

temperature at 60 em, air temperature in the shade 5 to 10 

em above the soil surface, wind speed and direction, and 

soil-gas extraction times were measured also. The extraction times represent an approximation of gas permeability at 

each depth. Less quantifiable factors that were noted were 

cloud cover, recent rain, snow cover, snowmelt, standing 

water, and whether or not a frozen or water-saturated layer 

of soil was present at the surface. Width and depth of soil 

cracks were recorded also; the cracks add a significant 

amount of permeability to the soil and indicate the extent of 

soil drying. 

Our soil-gas radon and meteorological measurements 

were integrated with meteorological data collected by the 

U.S. Bureau of Reclamation's weather station about 0.4 km 

away. The radon measurements were inserted into the data 

base at the nearest whole hour for comparison with weather 

station data. However, all 24 daily weather measurements 

were used for interpretation of the radon data. 

DISCUSSION 

Soil-gas radon concentrations vary progressively and 

markedly with season. A progressive drop in soil-gas radon 

concentration at 100 em can be seen in a plot of radon 

concentration over time (fig. 10). Radon concentrations 

were highest from March through June. Spring was the 

wettest period of the year in the study area and was 

characterized by unstable weather, with large fluctuations in 

air temperature, barometric pressure, relative humidity, and 

wind. During early spring, much of the precipitation fell in 

the form of wet snows that melted quickly and thus 

saturated the shallow soil layers and maintained a relatively 

consistent moisture cap that kept soil-gas radon concentrations elevated (fig. 10). The moisture cap was commonly 

frozen when nighttime temperatures dropped below freezing for extended periods of time. The soil-gas radon 

concentrations reached a minimum in August, and, except 

where affected by short-term weather events, remained low 

26 Field Studies of Radon in Rocks, Soils, and Water 

through the remainder of the year as a result of the relatively 

dry, stable weather conditions that existed during this 

period. 

Almost 75 percent of the precipitation recorded during the study period fell between March and mid-July (fig. 

10). Because temperatures were cooler and precipitation 

events were relatively evenly spaced during this period, the 

soil surface remained damp much of the time, and a 

moisture cap was apparently maintained until about midJune. The importance of moisture in maintaining the cap, 

especially in the semiarid climate typical of much of the 

Western United States, is illustrated by the drop in radon 

concentrations that occurred during the first part of April, 

an approximately 2-week period of fair, windy weather 

during which there was little precipitation, and daytime 

temperatures were generally above freezing. The surface of 

the soil began to dry, and surficial desiccation cracks 

appeared. Soil-gas radon concentrations rose again immediately following the next precipitation event. In soils with 

smectitic (swelling) clays such as those at the study site, 

less moisture may be needed to create and maintain capping 

conditions. 

Between mid-June and mid-July, the warmer daytime 

temperatures allowed the soil to dry between rains. As a 

result, the moisture cap was depleted, and exchange of soil 

gas with atmospheric air occurred. During summer and fall, 

more complete drying occurred, and desiccation cracks up 

to 1 em wide and 45 em deep appeared in the soil 

surrounding the study site. From August through September, a relatively free exchange between atmospheric air and 

soil gas in the near-surface layers was possible, and soil-gas 

radon concentrations at both 50 and 100 em were at their 

lowest. A slight increase in soil-gas radon concentrations at 

50 and 100 em at the beginning of November coincided 

with a drop in daily air and soil temperatures and greater 

fluctuations in barometric pressure. These higher radon 

levels were maintained through the remainder of the study 

period. 

In general, the highest radon concentrations occurred 

during wetter seasons. In the Denver area, this period, late 

winter through spring, is typically one of unsettled, highly 

variable weather in which snowfall and freezing temperatures may be followed the next day by warm, sunny 

weather, which tends to maximize percolation of snowmelt 

into the soil. In areas that have distinct wet and dry seasons, 

soil-gas radon values may vary by an order of magnitude or 

more. In areas that have wetter climates, radon values may 

be generally higher most of the year, except during periods 

of complete soil saturation. 

Whereas the major long-term trends in soil-gas radon 

concentrations are related to seasonal climatic variation, the 

shorter term, usually lower magnitude, fluctuations are 

related to changes in weather-storms, frontal passages, 

and movements of air masses. The dominant weather 

factors influencing day-to-day radon concentrations are 
40 640 Cl 

J: 

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E 

~ ~ 630 :;, 20 :;, 

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til 

CD ~ 0. 0. E 10 g .g 620 ~ Gi 

0 E 

e 

<II 

Ill 

30 ~ 

610 

g E 0 30 CD 20 E 

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~ 0 3000 

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E 0 

CD 0 ll) 

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~ 1000 

-10 ~ 

20 3000 

s .c 15 ~ ~ g 2000 

~ 10 

le CD 1ii > c: "C 

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c: ....I 

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e 80 ~ CD 

g 2000 0. 

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:;, 'ni 

40 .c c: CD 

~ 1000 ·! 

~ 20 a: ~ 

0 MAY JUN JUL AUG SEP OCT NOV 0 MAY JUN JUL AUG SEP OCT NOV 

1987 1987 

Figure 10. Weather parameters and radon in soil gas, Denver Federal Center study site . .:lTemp, delta temperature-a 

positive value when the air temperature is greater than the soil temperature and a negative value when the soil is warmer 

than the air; oc, degrees Celsius; mph, miles per hour; mm Hg, millimeters of mercury; pCi/L, picocuries per liter. 

barometric pressure changes and precipitation. An increase 

in barometric pressure is usually accompanied by, or 

followed by, a decrease in radon concentrations. It appears 

that the actual value of the barometric pressure is less 

important than whether a change has occurred. The magnitude and direction of the change determine the extent of the 

effect on soil-gas radon concentrations. It is important to 

note that effects of barometric pressure are stronger and 

more pronounced in highly permeable soils. The soils in the 

study area have a relatively low gas permeability (between 

10-8 and 10-9 cm2 , measured at 100 em; R.T. Peake, oral 

commun., 1987), so that the effect of barometric pressure is 

probably somewhat inhibited; nevertheless, the data suggest 

that barometric pressure is one of the two primary influences on daily radon fluctuations. Much of this effect may 

be due to the periodic, and sometimes prolonged, presence 

of numerous desiccation cracks in the soil that considerably 

enhanced the effective permeability of the: soil. A lag of 

from several hours to over a day between changes in 

barometric pressure and corresponding changes in soil-gas 

radon concentrations was noted (fig. 10). 

Precipitation, and its effect on soil moisture, is the 

second major cause of day-to-day fluctuations in soil-gas 

radon concentrations. A comparison of precipitation and 

radon concentration at 100 em (fig. 10) shows that the 

elevated soil-gas radon concentrations encountered during 

Environmental Factors Influencing Soil-Gas Radon Concentrations 27 
the spring and early summer continued as long as precipitation was sufficient to maintain a surface capping layer in 

the soil. When a prolonged dry period was encountered at 

the beginning of July, soil-gas radon concentrations 

dropped (fig. 10). Two of the three precipitation events in 

the latter part of the study period, the one near the end of 

August and the one in mid-November, correspond to 

increases in radon concentrations in the soil at both 50 and 

100 em. The precipitation in mid-October does not appear 

to have had a noticeable effect on the soil radon level at 100 

em, and just a slight increase in the radon level at 50 em 

followed the event. Perhaps the total amount of rainfall 

from that storm, about 20 mm, was insufficient to completely saturate the surface soil layers; this is a likely 

explanation in light of the almost 2 months of dry weather 

that preceded it. In contrast, the order-of-magnitude 

increase in radon concentration at 100 em that followed the 

rainfall in early May suggests that the amount of soil 

moisture in the near-surface layers was just below a 

threshold level for forming a moisture cap during late April, 

and this threshold was exceeded with the additional input of 

precipitation in early May (fig. 10). These examples point 

out the importance of antecedent conditions in determining 

the magnitude of the effects of weather on soil-gas concentrations. 

Changes in relative humidity appear to correlate fairly 

well with changes in soil-gas radon concentrations, but this 

correlation is because nearly every large peak on the relative 

humidity plot (fig. 10) corresponds to a precipitation event. 

Therefore, although a positive correlation exists between 

relative humidity and soil-gas radon concentrations, it is of 

a secondary nature, as the relative humidity values are 

generally indicators of precipitation when examined in the 

context of day-to-day fluctuations. 

Wind may have a less pronounced effect on the 

concentration and movement of soil-gas radon at the study 

site. A correlation between winds and soil-gas radon concentrations could not be positively identified. There are 

three possible explanations for this lack of correlation: ( 1) 

as discussed previously, the soil may not have been permeable enough to allow free exchange of atmospheric and soil 

air, (2) high winds usually preceded or accompanied 

storms, and the concurrent changes in barometric pressure, 

temperature, and soil moisture may have masked any wind 

effects, or (3) no identifiable correlation exists between 

winds and radon movement in soils. 

Air- and soil-temperature data show a seasonal negative correlation with soil-gas radon values. Radon values 

in the soil at the study site were highest during winter and 

spring, when temperatures were cooler (fig. 10). Dayto-day fluctuations in air temperature also show a negative 

correlation, because cooler-than-normal air temperatures 

usually result from storms. Note that all unseasonably low 

daily air temperatures correspond to low barometric pressures and precipitation. 

28 Field Studies of Radon in Rocks, Soils, and Water 

Temperature may exert an influence on soil-gas radon 

concentrations at the study site. However, the effect of 

temperature appears to be masked by pressure changes and 

precipitation that accompany storms. For example, a drop 

in soil or air temperature may accompany rainfall that 

effects a cap responsible for higher soil-gas radon levels. 

Although temperature would have a negative correlation 

with radon concentration, it would be difficult to determine 

a cause-and-effect relationship. In contrast, radon concentration could correlate positively with temperature when a 

high pressure system with attendant lower temperatures 

moves into an area, and the higher barometric pressure 

forces atmospheric air into the ground, where it dilutes the 

soil gas and reduces soil-gas radon concentrations near the 

surface. This positive correlation of radon with temperature 

could be misleading, because it may be coincident with 

another event. 

Because soil acts as a heat sink, fluctuations in soil 

temperature are small and gradual; thus, no identifiable 

correlation exists between soil temperature (at 60 em) and 

soil-gas radon concentrations in the context of daily time. 

However, in highly permeable soils, temperature-induced 

convection could enhance radon transport to a considerable 

degree (Kraner and others, 1964; Mogro-Campero and 

Fleischer, 1976; Jaacks, 1984). A plot showing the difference between air temperature at the surface and soil 

temperature at 60 em indicates those periods when conditions are favorable for temperature-induced convective 

transport (fig. 10). This difference, which we refer to as 

"delta temperature," or "dTemp," has a positive value 

when the air temperature is greater than the soil temperature 

and a negative value when the soil is warmer than the air. 

The sign (+or-) of ..1Temp indicates the direction of 

temperature gradients between soil air and atmospheric 

air-upward when dTemp is positive, downward when it is 

negative. Although a correlation exists between ..1Temp and 

changes in soil-gas radon concentrations, this may be 

because ..1 Temp is a derivative of the more basic factors of 

soil and air temperature. 

In an attempt to quantify the relationships between 

weather factors and soil-gas radon concentrations, linear 

correlation coefficients were calculated for each of the 

parameters in the data set (table 3). These correlations are 

defined as significant at the 95-percent confidence level. As 

shown in table 3, the radon concentrations at 100 em show 

significant negative correlations with "month/day" (indicating that the highest radon values occur seasonally) and with 

"barometric pressure" and "soil temperature." The lack of 

significant correlations between radon at 50 and 75 em and 

barometric pressure may be explained by the fact that fewer 

measurements were made of radon concentrations at these 

depths, so the data are not sufficient to establish significant 

correlations. 

Significant positive correlations between radon concentrations at 100 em and both dTemp and relative humid-
Table 3. Linear correlation coefficient matrix of weather and radon parameters at the Denver Federal Center study site 

[Values in boldface are significant at a 95-percent confidence level; number of pairs for each correlation is equal to the smaller number of sample factors 

in each pair; ~Temp, difference between air temperature at the surface and soil temperature at 60 em] 

Number Month/ Barometric Air Soil 

of samples day pressure temper- temperature ature 

Month/day 156 1.000 0.358 0.076 0.293 

Barometric pressure 152 1.000 .162 .306 

Air temperature 152 1.000 .746 

Soil temperature 150 1.000 

.1.Temp 149 

Relative humidity 152 

Wind speed 152 

Precipitation 156 

Radon at 50 em 109 

Radon at 75 em 50 

Radon at 100 em 153 

ity exist. Both of these correlations appear to illustrate a 

common problem in the interpretation of correlation data: 

"Frequently, two variables may appear to be highly correlated when, in fact, they are not directly associated with 

each other but are both highly correlated with a third 

variable" (Huntsberger and Billingsley, 1981, p. 396) . 

.:lTemp is calculated from air and soil temperatures, as 

discussed previously. Relative humidity acts as an indicator 

of precipitation and is statistically more significant than 

precipitation itself, because relative humidity generally 

increases to a level in the range of 80 to 100 percent during 

and after rains, whereas precipitation can occur as one large 

magnitude event or as a number of closely spaced smaller 

events, both having a similar effect on soil moisture but not 

on statistical correlations. 

Radon concentrations at 100 em also correlate positively with radon concentrations at 75 em but not with radon 

at 50 em. Radon at 75 em correlates with radon at both 50 

and 100 em. These correlations indicate that radon concentrations at 50 em and 100 em vary in a dissimilar manner (at 

least statistically) and that conditions at 75 em are transitional between those at shallower and greater depths. Radon 

concentrations at 50 em also correlate significantly with 

precipitation; however, the lack of any other significant 

correlations with radon at either 50 or 75 em is disturbing, 

because the soil gas nearest the surface is expected to be 

most sensitive to meteorologic effects. A possible explanation for this disparity is that the variability in radon 

concentrations at depths shallower than 100 em is due to the 

complex interaction of a number of factors that cannot be 

separated statistically, at least by the method of statistical 

analysis employed here. 

Table 4 summarizes what we consider to be the 

fundamental factors influencing radon concentrations in soil 

gas, considered in the context of different time scales. The 

table was developed from our analysis of this study's data 

and from our interpretations of previous researchers' work. 

These relationships should be generally applicable in any 

Relative Wind Precipi- Radon Radon Radon llTemp humidity speed tation at 50 em at 75 em at 100 em 

-0.329 -0.162 -0.340 -0.104 -0.092 -0.109 -0.642 

-.084 -.067 -.492 -.025 .078 -.018 -.342 

.779 -.561 -.161 -.166 -.001 .106 -.126 

.235 -.015 -.246 .021 .061 .121 -.231 

1.000 -.610 -.019 -.169 -.080 -.055 .177 

1.000 .019 .388 .151 .011 .257 

1.000 -.003 -.047 -.151 .130 

1.000 .230 -.123 .134 

1.000 .297 .121 

1.000 .418 

1.000 

Table 4. Summary of factors influencing soil-gas radon 

concentrations 

[ +, generally positive influence (that is, an increase in the factor generally 

causes an increase in soil-gas radon concentration); -, generally negative 

influence; ±, may have either positive or negative influence, because 

influence is interrelated with or dependent on other factors; blank indicates 

that the influence of that factor is not significant during that time scale] 

Factor 

Radium content of soil 

Soil permeability1 

Precipitation/soil moisture2 

Barometric pressure 

Wind speed 

Air temperature 

Soil temperature 

Time scale of influence 

Geologic Seasonal Daily 

+ 

+ + 

± 

+ 

± 

± 

± 

1

Effective permeability is influenced by variations in soil-moisture 

content. 2 At the Denver Federal Center site, increasing soil moisture caused 

capping effects that increased soil-gas radon concentrations; in more 

permeable soils or soils with lower clay contents, however, high soilmoisture contents would generally cause soil-gas radon contents to 

decrease as soil pores become occluded with water. 

geologic, pedologic, or climatic setting. A positive influence (signified by a +) indicates that an increase in the 

factor correlates with an increase in soil-gas radon concentrations. In contrast, a negative influence (indicated by a-) 

means that an increase in that factor correlates with a 

decrease in soil-gas radon concentrations. 

Note that we do not imply an implicit cause-andeffect relationship for each factor; the seemingly complex 

interaction of weather factors makes a definitive determination of cause and effect difficult. Theoretical discussions 

of the physical processes associated with weather and 

soil-gas radon generation and migration provide a foundation for understanding these relationships. However, empirical data as yet are not sufficient to definitively confirm and 

quantitatively describe those relationships. 

Environmental Factors Influencing Soil-Gas Radon Concentrations 29 
SUMMARY 

Statistical analysis and visual inspection of quantitative data from our study site suggest that no single factor 

controls radon concentrations on either a daily or a seasonal 

basis. However, precipitation, because it increases soil 

moisture, appears to be the most important control of 

seasonal soil-gas radon content and variation. On a dayto-day basis, however, weather factors such as barometric 

pressure, precipitation's capping effects, temperature, and 

winds interact to control radon fluctuations. 

We have shown that radon concentrations in soil at a 

single site are variable through time and that these variations are due primarily to the effects of changes in meteorological variables. An understanding of the interactions of 

meteorologic variables with soil gases is necessary if 

short-term soil-gas sampling is to be used to predict 

long-term ranges of radon concentrations. In addition, 

because radon sampling programs typically consist of measurements taken at multiple sample sites, often covering 

several soil and rock units, an understanding of geologic 

and pedologic processes and parameters, as they relate to 

radon generation, concentration, and transport, is also 

necessary. Although geologic and meteorologic controls on 

soil-gas radon have often been studied separately, it is only 

by integration of these data that effective site or area 

evaluations can be made. 

REFERENCES CITED 

Bakulin, V .N., 1971, Dependence of radon exhalation and its 

concentration in the soil on meteorological conditions [abs.]: 

Chemical Abstracts, v. 74, no. 33637u. 

Ball, T.K., Nicholson, R.A., and Peachey, D., 1983, Effects of 

meteorological variables on certain soil gases used to detect 

buried ore deposits: Transactions of the Institution of Mining 

and Metallurgy, v. 92, p. B183-B190. 

Baranov, V.I., and Novitskaya, A.P, 1960, Humidity effects on 

emanation [in Russian]: Radiokhimiya, v. 2, p. 485--490. 

Clements, W.E., and Wilkening, M.H., 1974, Atmospheric 

pressure effects on Rn-222 transport across the earth-air 

interface: Journal of Geophysical Research, v. 79, p. 

5025-5029. 

Damkjaer, A., and Korsbech, U., 1985, Measurement of the 

emanation of radon-222 from Danish soils: The Science of 

the Total Environment, v. 45, p. 343-350. 

Gundersen, L.C.S., Reimer, G.M., and Agard, S.S., 1988, 

Correlation between geology, radon in soil gas, and indoor 

radon in the Reading Prong, in Marikos, M., ed., Proceedings of GEORAD, Geology in Causes of Radionuclide 

Anomalies: Missouri Department of Natural Resources Special Publication No. 4, p. 99-111. 

Hansen, W.R., Chronic, J., and Matelock, J., 1978, Climatography of the Front Range Urban Corridor and vicinity, Colorado: U.S. Geological Survey Professional Paper 1019, 59 p. 

Hesselbom, A., 1985, Radon in soil gas: A study of methods and 

instruments for determining radon concentrations in the 

30 Field Studies of Radon in Rocks, Soils, and Water 

ground: Uppsala, Sweden, Sveriges Geologiska Undersokning, ser. C, no. 803, p. 1-58. 

Holkko, J., 1987, Radon in the ground in Finland: Soil Mechanics 

Laboratory, Department of Structural Engineering, Helsinki 

University of Technology, Espoo, Finland, 33 p. 

Huntsberger, D.V., and Billingsley, P., 1981, Elements of statistical inference, 5th ed.: Boston, Allyn and Bacon, Inc., 505 

p. 

Jaacks, J.A., 1984, Meteorological influence upon mercury, 

radon and helium soil gas emissions: Golden, Colo., Colorado School of Mines, unpublished Ph.D. thesis, 170 p. 

Jeter, H.W., Martin, J.D., and Schutz, D.F., 1977, The migration 

of gaseous radionuclides through soil overlying a uranium ore 

deposit: A modeling study: U.S. Department of Energy 

Report GJBX-67(77), 57 p. 

Klusman, R.W., and Webster, J.D., 1981, Preliminary analysis of 

meteorological and seasonal influences on crustal gas emission relevant to earthquake prediction: Bulletin of the Seismological Society of America, v. 71, p. 211-222. 

Kovach, E.M., 1945, Meteorological influences upon the radon 

content of soil gas: Transactions, American Geophysical 

Union, v. 26, p. 241-248. 

---1946, Diurnal variations of the radon content of soil gas: 

Terrestrial Magnetism and Atmospheric Electricity, v. 51, p. 

45-55. 

Kraner, H.W., Schroeder, G.L., and Evans, R.D., 1964, Measurements of the effects of atmospheric variables on radon222 flux and soil gas concentrations, in Adams, J.A.S., and 

Lowder, W .M., eds., The natural radiation environment: 

Chicago, Ill., University of Chicago Press, p. 191-215. 

Lindmark, A. and Rosen, B., 1985, Radon in soil gas-Exhalation tests and in situ measurements: The Science of the Total 

Environment, v. 45, p. 397--404. 

Lindvall, R.M., 1978, Geologic map of the Fort Logan quadrangle, Jefferson, Denver, and Arapahoe Counties, Colorado: 

U.S. Geological Survey Geologic Quadrangle Map 

GQ-1427, 1:24,000. 

Mattsson, R., 1970, Seasonal variation in short-lived radon 

progeny, Pb-210 and Po-210, in the ground level air in 

Finland: Journal of Geophysical Research, v. 75, p. 

1741-1744. 

Miller, J.M., and Ostle, D., 1973, Radon measurement in 

uranium prospecting, in Uranium exploration methods: Proceedings of a panel: Vienna, Austria, International Atomic 

Energy Agency, p. 237-247. 

Mogro-Campero, A., and Fleischer, R .L., 1976, Subterrestrial 

fluid convection-A hypothesis for long distance migration 

of radon within the earth: Schenectady, N.Y., General 

Electric Company Technical Information Series, No. 

76CRD133, 4 p. 

Neiburger, M., Edinger, J.G., and Bonner, W.D., 1973, Understanding our atmospheric environment: San Francisco, Calif., 

W.H. Freeman and Company, 293 p. 

Pearson, J. E. , and Jones, G. E. , 1966, Soil concentrations of 

"emanating radium-226" and the emanation of radon-222 

from soils and plants: Tellus, v. 18, p. 655-661. 

Robertson, J.B., 1969, Diffusion from a gaseous source in a 

porous medium- A field and theoretical comparison: U.S. 

Geological Survey Professional Paper 650-D, p. 

D265-D273. 
Schery, S.D., Gaeddert, D.H., and Wilkening, M.H., 1984, 

Factors affecting exhalation of radon from a gravelly sandy 

loam: Journal of Geophysical Research, v. 89, p. 7299-7309. 

Schumann, R.R., and Owen, D.E., 1988, Relationships between 

geology, equivalent uranium concentration, and radon in soil 

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soil to the atmosphere: Philosophical Magazine and Journal 

of Science, October 1912, p. 63 2-63 7. 

Soil Conservation Service, 1983, Soil survey of Golden area, 

Colorado; Parts of Denver, Douglas, Jefferson, and Park 

Counties: U.S. Department of Agriculture, 407 p., 15 pls. 

Taipale, T.T., and Winqvist, K., 1985, Seasonal variations in soil 

gas radon concentration: The Science of the Total 

Environment: v. 45, p. 121-126. 

Tanner, A.B., 1964, Radon migration in the ground: A review, in 

Adams, J.A.S., and Lowder, W.M., eds., The natural 

radiation environment: Chicago, Ill., University of Chicago 

Press, p. 161-190. 

---1980, Radon migration in the ground: A supplementary 

review, in Gesell, T.F., and Lowder, W.M., eds., Natural 

radiation environment III, Symposium proceedings: 

Springfield Va., National Technical Information Service, 

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Environmental Factors Influencing Soil-Gas Radon Concentrations 31 

DERIVATION OF RADON MIGRATION RATES IN THE SURFICIAL ENVIRONMENT 

BY USE OF HELIUM INJECTION EXPERIMENTS 

G.M. Reimer 

Abstract 

Helium injection into the subsurface provides a 

means of determining the rate of radon migration in a 

particular area. The passage of a concentration front is 

monitored at outlying stations, and an effective diffusion 

coefficient can be determined. From experiments in a 

portion of the Reading Prong near Boyertown, Pa., it is 

possible to explain the observations with a model in which 

diffusion is the primary transport mechanism, and convective mass tranport is influential. This technique permits 

determination of both horizontal and vertical migration 

components. The rate of migration is highly variable from 

area to area, but measurements can set realistic limits on 

models being developed for assessing the potential for 

radon accumulation in dwellings. 

INTRODUCTION 

The rate of radon migration in the surficial environment can greatly influence the indoor radon concentration. 

The movement of radon through soils has been the subject 

of numerous theoretical and empirical evaluations (Tanner, 

1964; Jeter, 1980; Wilkening, 1980; Kristiansson and 

Malmqvist, 1982; Nazaroff and others, 1985); yet, study 

continues in order to determine a value or develop a unified 

model to predict the rate. A major difficulty in designing a 

model is the highly complex environment that is being 

investigated and the interrelationship of all the variables that 

can affect the movement of gases. A general consensus has 

been reached, however, on the major influences, which are 

meteorologic, those pertaining to soil chemistry and physics, concentration and nature of the source, and hydrologic 

intervention. In any one fixed location, the rate of radon 

migration is variable with time because it depends on the 

relative "strengths" of the influences, which are themselves 

variable. 

A technique that can be used to measure the migration 

of gases is the direct injection of gas into the subsurface and 

the monitoring of the passage of the gas at various distances 

from the injection site. This approach was used in a number 

of studies to trace underground migration pathways (Turk 

and others, 1968; Robertson, 1969a,b; Herring and others, 

1985; Reimer and Been, 1985). This technique was used 

with radon by Bulashevich and Kartashov (1967) to determine the radon diffusion coefficient in different natural 

surroundings. They demonstrated that the radon diffusion 

coefficient could be estimated from the helium diffusion 

data. In this paper, diffusion refers to dynamic molecular 

diffusion, which does not require that equilibrium conditions be achieved. Convective transport refers to movement 

due to bulk flow that has been induced by other driving 

mechanisms such as changes in barometric pressure or 

temperature gradients active in the near-surface soils. 

Injection methods have the unequaled advantage of 

being the most realistic for the in situ determinations but 

have the disadvantage of being time consuming if large 

areas are being evaluated. Helium has several advantages 

for determining diffusion coefficients in surficial settings. It 

is safe to handle, has the fastest rate of diffusion of the 

noble gases, and, with mobile equipment, can be detected at 

part-per-billion concentrations. A demonstration study was 

performed in an area near Boyertown, Pa., where indoor 

and soil-gas radon concentrations in adjacent homes differed by more than an order of magnitude. Helium was 

injected through probes pounded into the ground (Reimer 

and Bowles, 1979), and the mobile helium analyzer developed by the U.S. Geological Survey was used for analysis 

(Reimer and others, 1979). The helium analyzer has a 

sensitivity of 10 ppb (parts per billion) for helium. 

STUDY SETTING 

The site for injection in the Boyertown area was 

within soil overlying a localized mylonitic zone in a 

quartz-feldspar and biotite gneiss that had been identified by 

Gunderson and others ( 1987) as being the host rock for 

locally higher uranium concentrations. Homes built within 

this geologic unit had indoor radon concentrations in excess 

of the Environmental Protection Agency guideline of 4 

pCi/L (picocuries per liter) (Environmental Protection 

Agency, 1986). Soil-gas radon concentrations in this zone 

were 5,000 to 10,000 pCi/L. At the sampling site, the 

mylonitic zone trends N. 70° E. and is about 40 m (meters) 

wide. A series of probes was set within the zone to sample 

both parallel and perpendicular to this trend. The injection 

probe was at a 2-m depth, and monitoring probes were at a 

1-m depth. The measured rate would be a combination of 

horizontal and vertical migration components. The monitoring probes were 2, 4, and 6 m in distance from the 

injection probe (fig. 11). The soil was saprolitic, and the 

upper surface was reworked to an average depth of 0.2 m 

from the construction of the nearby residence. Some free 

moisture was present in the soil from moderate precipitation 

that had occurred 2 days earlier. The study ran for a period 

of 4 hours on August 19, 1986. At the beginning of the 

study, the sky was overcast, the air temperature was 25 °C 

(degrees Celsius), the barometric pressure was 94.0034 kPa 

(kilopascals) (705.202 mm Hg, millimeters of mercury), 

Derivation of Radon Migration Rates 33 
radon vent 

/ 

/ 

/ 

/ 

/ 

/ 

/ 

/ 

/ 

3 

• 2 4 

• • 

RESIDENCE 

5 

• 

vent 

Figure 11. The location of the injection probe (1) and the 

monitoring probes (2-9) for the helium migration study. 

All probes are within the soils above the mylonitic zone. 

Even-numbered stations are 2 m distant and oddnumbered stations 4 m distant from the injection site. The 

zone trends N. 70° E., and the northern limit is approximately located by the dashed line. 

and the wind was from the northwest at 8 to 15 km/h 

(kilometers per hour). Barometric pressure decreased by 

0.0207 kPa (0.155 mm Hg), temperature increased to 27 oc 

during this period, and the wind remained the same 

throughout the study period. 

A total of 14,000 cm3 (cubic centimeters) STP 

(standard temperature and pressure) high-purity helium was 

injected during a 7-min (minute) period (a rate of 35 cm3

/s, 

cubic centimeters per second). A pressure monitor, having 

a maximum pressure limit of 175 kPa, was set on one of the 

monitoring probes 2 m distant. During the injection, the 

monitor showed no increase in pressure at the sensitivity 

limit of the pressure transducer, 2 parts in a million. 

Initially, samples were collected from every outlying probe. 

The sampling interval increased from a few minutes to 15 

min after a response to the injected helium was observed at 

the closest monitoring probes. 

34 Field Studies of Radon in Rocks, Soils, and Water 

RESULTS 

Figures 12 to 19 show the results of the helium 

analyses. Even-numbered stations were 2 m distant and 

odd-numbered stations were 4 m distant from the injection 

site. All inner stations showed a response in about 30 to 45 

min, and the outer stations responded in about 90 to 150 

min, with the exception of stations 4 and 5. These 2 probes 

were located parallel to the mylonitic trend but topographically lower than the other probes. This area also contained 

the most soil moisture. In fact, probe 4 was relocated a few 

centimeters along the sampling pattern radius before injection because free water was drawn from it with the syringe 

when a pre-injection sample was collected. Gas was easily 

drawn from the remaining probes. Probe group 2 and 3 and 

group 8 and 9 showed a response slightly later than probe 

group 6 and 7. This delayed response may result from the 

lamination of the mylonitic zone that permits gas to migrate 

more freely in the N. 70° E. direction. In addition, stations 

4 and 6 showed a decrease in helium after about 200 min 

that probably represents the passage of the maximum 

concentration available. The open circle on figures 12, 13, 

18, and 19 is the helium soil-gas concentration 18 hours 

after injection. The inner stations showed a decrease, but 

the outer stations had higher values than they had the 

previous day. 

DISCUSSION 

Although the migration of gases in the soil is controlled by a number of complex and interrelated factors, it is 

possible to explain a large amount of the migration observed 

in this study by use of a simplified diffusion model. This 

approach is based on studies of environmental hazards 

presented by Thibodeaux ( 1979). It is a plausible model 

because the near-surface environment has high permeability 

and porosity. Because we are dealing with a dynamic 

system, diffusion in this model does not mean equilibrium 

conditions must be achieved. While diffusion can explain 

most of the observed migration rate, the remainder is 

probably from convective transport. 

The helium injection represented a point source in 

both time and space. The sensitive analytical capabilities 

permit the advancing gradient to be detected. A helium 

background concentration for the area was determined by 

analyzing the soil gas for helium at each monitoring probe 

site. After injection, helium was detected at the 2-m 

monitoring stations in approximately 40 min and at the 4-m 

stations in approximately 160 min. In the presence of a 

concentration difference, there appears to be an r

2 function, 

or mean square displacement, for the time-distance relationship, where r is the radius of the system being evaluated. 

From the helium data, it is possible to develop a mathematical model using Pick's second law to describe the rate of 

molecular diffusion or penetration in a stagnant air mass and 
Gl 7 

iii 

u 

Ill 

til 

g 0 

.t:l 

Q. 

Q. 

.E 

c' 

0 

~ c 

B 

c 

0 

u 

E 

.2 

.. :r:: 0 

0 100 200 

Time (minutes after injection) 

Figure 12. Variation in soil-gas helium concentration at 

station 2 as a function of time after injection at probe site 

1. Open circle is the helium soil-gas concentration 18 

hours after injection. ppb, parts per billion (figs. 12 

through 19). 

Gl 

iii 

u 

Ill 

til 

g 

.t:l 

Q. 

Q. 

·= 4 c" 

~ 

I! 3 

c 

Gl 

u 

c 

0 

u 

E 

.2 

.. :r:: 0 

0 100 200 

Time (minutes after injection) 

Figure 14. Variation in soil-gas helium concentration at 

station 4 as a function of time after injection at probe 

site 1. 

Gl 7 

iii 

u 

Ill 

til 

g 

.t:l 

Q. 

Q. 

·= c" 

~ 

I! 

c 

Gl 

u 

c 

0 

u 

E 

.2 

'ii 

:r:: 0 

0 100 200 

Time (minutes after injection) 

Figure 16. Variation in soil-gas helium concentration at 

station 6 as a function of time after injection at probe 

site 1. 

Gl 7 

iii 

u 

Ill 

til 

g 

.t:l 0 Q. 

Q. 

·= c' 

0 

-~ 3 

c 

B 

c 

0 

u 

E 

.2 

.. :r:: 0 

0 100 200 

Time (minutes after Injection) 

Figure 13. Variation in soil-gas helium concentration at 

station 3 as a function of time after injection at probe site 

1. Open circle is the helium soil-gas concentration 18 

hours after injection. 

Gl I 

iii 

u 

Ill 

til 

g 

.t:l 5 Q. 

Q. 

·= 4 

c 

.5! 

~ 3 

c 

Gl 

u 

c 

0 

u 

E 

.2 

.. :r:: 0 

0 100 200 

Time (minutes after injection) 

Figure 15. Variation in soil-gas helium concentration at 

station 5 as a function of time after injection at probe 

site 1. 

Gl 

iii 

u 

Ill 

til 

g 

.t:l 

Q. 

Q. 

·= c" 

0 

~ c 

Gl 

u 

c 

0 

u 

E 

.2 

'ii 

:r:: 0 

0 100 200 

Time (minutes after Injection) 

Figure 17. Variation in soil-gas helium concentration at 

station 7 as a function of time after injection at probe 

site 1. 

Derivation of Radon Migration Rates 35 
'i' 

'i 

u 

II) 

Cl 0 g 

.a 5 Q. 

Q. 

.: 4 

c 

0 

~ 3 

E 

CD 

u 

c 

0 

u 

E 

.2 

'ii 

J: 0 

0 100 200 

Time (minutes after injection) 

Figure 18. Variation in soil-gas helium concentration at 

station 8 as a function of time after injection at probe site 

1. Open circle is the helium soil-gas concentration 18 

hours after injection. 

0.8 

0.6 

-e-

-G; 

0.4 

0.2 

Figure 20. Plot of the probability function used for equation 1. erf is the gauss error integral, or probability 

function, which is obtained from a calculated value, represented by phi (<!>), of parameters in equation 1. 

then apply this finding to the more complex and varied soil 

system. The relationship among concentration, distance, 

and time can be expressed with the following formula: 

(1) 

where Cz = mole fraction of helium to be determined, 

C s = mole fraction of helium at the source, 

C b = background mole fraction of helium, 

z = distance, 

36 Field Studies of Radon in Rocks, Soils, and Water 

7 G) 

'i 

u 

II) 

Cl 

g 

.a 5 0 Q. 

Q. 

·= c 

0 

·~ 

.2 

'ii 

J: 

E 

3 

0 

E 

u 

c 

0 

0 

~ 

100 200 

Time (minutes after injection) 

Figure 19. Variation in soil-gas helium concentration at 

station 9 as a function of time after injection at probe site 

1. Open circle is the helium soil-gas concentration 18 

hours after injection. 

~ 

! 

E 

c ; .. u 

c 

s 

Ill 

i5 

so.------------.-,----------,~,-----------, 

40 fI 

I 

I 

I 

/ 

/ 

/ 

/ / / 

/ / 

/ / / 

0~1 0 10 

/ / ,...,... / / / / / 

I 

20 

TIME, in days 

,....- / 

_..,.,..,HELIUM / 

-

RADON 

I 

30 

Figure 21. Plot of a probable migration distance with time 

for helium and radon in soils at the Boyertown site. The 

distances are the advancing front or penetration distances 

of gas from a source and are not expressing an equilibrium 

condition. 

D = diffusivity of helium in air, 

t =time, and 

erf = the gauss error integral, or probability 

function. 

Figure 20 is a plot of the error function. The equation 

is valid where the concentration gradients are within a few 

orders of magnitude of each other and the range of time and 

distance are within about 5 orders of magnitude. 

The absolute helium concentration in the soil at the 

injection site after injection is not known, because the 
concentration exceeded the upper limit of analytical resolution. A controlled process to dilute the sample before 

analysis was not available in the field. 

An alternate method is to select 2 monitoring probes 

as the points of evaluation for the equation. If the probe pair 

6-7 is selected, the concentration of helium after 40 min is 

35,240 ppb at station 6 and 5,270 ppb (which is considered 

background) at station 7. A diffusion coefficient of 0.6 

cm2/s for helium in air is used (Pogorski and Pogorski, 

1982). Other values to determine Cz are Cs=35,240 ppb, 

Cb=5,270, z =200 em, D =0.6 cm2/s, and t =7,200 s. The 

calculated value of helium at station 7 is 6,220 ppb for 2 

hours after the station 6 concentration was measured. After 

background concentrations (5,270 ppb) are subtracted, the 

measured concentration for station 7 is 7,340 ppb, only 

about twice what would be expected from diffusion alone. 

Several conditions exist that should be applied to the 

derivation to make the transition from an air system to a soil 

system. The first is that the source concentration at station 

6 is continually increasing. This continual increase would 

have the effect of increasing the concentration at station 7 

during the time period of 2 hours. A second condition is that 

the hindrance factor for gases diffusing through the soil 

must be considered. Typical hindrance factors are 2 to 7, if 

tortuosity, particle shape, and the soil void fraction are 

combined (Thibodeaux, 1979). The effective diffusion 

coefficient would be lower by a proportional amount. A 

third consideration is that convective mass transport is also 

acting in the near-surface environment. Because the measured concentration was greater than calculated, mass 

transport and increasing helium concentration at the source 

had a greater influence than the hindrance. Other station 

pairs show different responses. For example, the station 

pair 4-5 was known to be in a zone of higher moisture 

content. Station 4 showed an increase in helium 75 min 

after injection, but station 5 showed no response after 200 

min. Diffusion coefficients for water (Boerboom and 

Kleyn, 1969) are on the order of 10-4 to 10-5 cm2/s; thus, 

even if the zone is not saturated, the decrease in permeability caused by water in the pore spaces reduces the migration 

rate. 

From these measurements for helium, a general 

migration rate can be derived. The detectable helium front 

migrates at a rate where time is related approximately to the 

square of the distance from the source. Figure 21 shows this 

function for helium as determined from the empirical data. 

At the end of a 28-day period, the helium would be capable 

of migrating 64 m. If it is assumed that the helium 

measurement is an indication of permeability and the 

approximation that diffusion of gases is proportional to the 

square root of the masses is used, radon would migrate 7 

times more slowly and would traverse only about 9 m in the 

same time. That time period is a practical limit for radon 

because of the 3.8-day half-life. Interestingly, this distance 

is one that has been determined theoretically for radon in 

systems involving other types of overburden (Tanner, 

1964). Naturally, when convective transport is involved 

because of atmospheric pumping or ground-water movement, radon and other gases can move more rapidly. 

Convective transport probably is always working in the 

near-surface environment. For example, the measured elevated radon content of soil-gas extends 20 m from the 

contact with the mylonite in this area (Reimer and Gundersen, 1989). 

As a check on the practicality of the diffusion model, 

the diffusion coefficient for helium was calculated following the method of Bulashevich and Kartashov (1967), 

whereby the passage of the concentration maximum at a 

monitoring site is used. If the values for station 4 are used, 

where the maximum helium concentration was encountered 

at 200 min, a gross diffusion coefficient of 0.69 cm2/s was 

determined. This compares favorably with the value of 0.6 

cm2/s used for the calculations in this study and indicates a 

close balance between hindrance factors and the opposing 

influences of mass transport. 

CONCLUSIONS 

Gaseous migration in the soil is a very difficult 

parameter to measure empirically or to determine theoretically. The soil is not a homogeneous medium; permeability, 

porosity, grain shape and size, composition, moisture 

content, and abundance of cracks and fractures are all 

variables. If the meteorologically induced effects that contribute to mass transport in the near-surface soil environment are included, the range of the variables becomes too 

large to define a universal, simplified model adequately. 

Even the rudimentary injection experiment performed in 

this study shows large variations over a distance of only 4 

m. The results, however, set realistic constraints on the 

distance of gas migration in the Boyertown area and 

demonstrate that diffusion can contribute significantly to the 

migration. Rates of gaseous migration in the soil then can 

be explained by applying hindrance factors to a model 

characterizing diffusion in stagnant air. Rates of gaseous 

migration in the surficial environment are probably in the 

transition area between definitions of diffusion and convective mass transport, and the dominant mode will be controlled by the variable external influences. 

Specific geologic units are responsible for the higher 

radon content in homes in the Boyertown area. Houses 

constructed on or near those units are more likely to have 

elevated indoor radon concentrations than those built 10 to 

50 m away. The radon soil-gas measurements confirm the 

limited dispersion from the surface (or near-surface) contacts of the geologic units and suggest that the vertical and 

horizontal migration of radon is constrained. Where no 

unique geologic source of higher radon supply is found for 

dwellings having a radon buildup, there is the implication 

Derivation of Radon Migration Rates 37 
that overall gross permeability may be sufficiently large to 

allow a larger volume of rock or soil to contribute radon. It 

may be possible to establish criteria based on soil-gas radon 

measurements and permeability that would identify zones of 

high radon availability that contribute to indoor accumulation. Similarly, if the measurements were below a certain 

limit, lower concentrations would be anticipated. The limits 

would have a substantial and perhaps variable area of 

uncertainty between them, the size of which would depend 

on other external parameters such as construction techniques. 

ACKNOWLEDGMENTS 

The fieldwork was conducted with the assistance of 

Josh M.Been, Linda C.S. Gundersen, Mitchell E. Henry, 

and James Shannon. This work was supported in part by the 

Department of Energy, Office of Health and Environmental 

Research, under agreement DE-AI05-87-ER60578. 

REFERENCES CITED 

Boerboom, A.J., and Kleyn, G., 1969, Diffusion coefficients of 

noble gases in water: Journal of Chemical Physics, v. 50, p. 

1086-1088. 

Bulashevich, Yu.P., and Kartashov, N.P., 1967, Determination 

of the diffusion coefficient of radon in rocks by the 

instantaneous-source method: Izvestia (Earth Physics), no. 

10, p. 71-76. 

Environmental Protection Agency, 1986, A citizen's guide to 

radon: OPA-86-004, Washington, D.C., U.S. Government 

Printing Office, 14 p. 

Gundersen, L.C.S., Reimer, G.M., and Agard, S.S., 1987, 

Geologic control of radon in Boyertown and Easton, Pa. 

[abs.]: Geological Society of America Abstracts with Programs, v. 19, no. 2. 

Herring, J.R., Reimer, G.M., and Been, J.M., 1985, Helium and 

sulfur hexafluoride gases as stable tracers of geological 

processes [abs.]: Eos, Transactions of the American Geophysical Union, v. 66, p. 1116. 

Jeter, H.W., 1980, A modeling study of gaseous Rn-222, Xe-133, 

and He-4 for uranium exploration: U.S. Department of 

Energy Report GJBX-140(80), 111 p. 

38 Field Studies of Radon in Rocks, Soils, and Water 

Kristiansson, K., and Malmqvist, L., 1982, Evidence for nondiffusive transport of 222Rn86 in the ground and a new 

physical model for the transport: Geophysics, v. 47, p. 

1444-1452. . 

Nazaroff, W.W., Feustel, H., Nero, A.V., Revzan, K.L., Grimsrud, D.T., Essling, M.A., and Toohey, R.E., 1985, Radon 

transport into a detached one-story house with a basement: 

Atmospheric Environment, v. 19, no. 1, p. 31-46. 

Pogorski, L.A., and Pogorski, S.R., 1982, The effect of the 

physical properties of the overburden on helium emanometry: 

Department of Energy Report Number GJBX-114(82), 191 

p. 

Reimer, G.M., and Been, J.M., 1985, Helium as a tracer gas for 

locating gas flow pathways in an abandoned coal mine [abs.]: 

Eos, Transactions of the American Geophysical Union, v. 

66, p. 1115-1116. 

Reimer, G.M., and Bowles, C.G.,1979, Soil-gas helium concentrations in the vicinity of a uranium deposit, Red Desert, 

Wyoming: U.S. Geological Survey Open-File Report 

79-975, 9 p. 

Reimer, G.M., Denton, E.H., Friedman, 1., and Otton, J.K., 

1979, Recent developments in uranium exploration using the 

U.S. Geological Surevey's mobile helium detector: Journal 

of Geochemical Exploration, v. 11 , p. 1-12. 

Reimer, G. M. , and Gundersen, L. C. S. , 1989, A direct correlation 

among indoor Rn, soil-gas Rn and geology in the Reading 

Prong near Boyertown, Pennsylvania: Health Physics, v. 57, 

p. 155-160. 

Robertson, J .B., 1969a, Behavior of xenon-133 gas after injection 

underground: U.S. Geological Survey Open-File Report, 

69-226, 37 p. 

---1969b, Diffusion from a gaseous source in a porous 

medium-A field and theoretical comparison: U.S. Geological Survey Professional Paper 650-D, p. D265-D273. 

Tanner, A.B., 1964, Radon migration in the ground: A review, in 

Adams, J.A.S., and Lowder, W.M., eds., The natural 

radiation environment: Chicago, Ill., University of Chicago 

Press, p. 161-190. 

Thibodeaux, L.J., 1979, Chemodynamics: Environmental movement of chemicals in air, water and soil: New York, N.Y., 

John Wiley and Sons, 501 p. 

Turk, A., Edmonds, S.M., Mark, H.C., and Collins, G.F., 1968, 

Sulfur hexafluoride as a gas tracer: Environmental Science 

and Technology, v. 2, p. 44-48. 

Wilkening, M.H., 1980, Radon transport in soil and its relation to 

indoor radioactivity: The Science of the Total Environment, 

v. 45, p. 219-226. 
PART 1: STUDIES OF RADON IN ROCKS AND SOIL 

SECTION 2: GEOLOGIC FIELD STUDIES 

RADON IN SHEARED METAMORPHIC AND IGNEOUS ROCKS 

Linda C.S. Gundersen 

Abstract 

Sheared fault zones in the Appalachian region of the 

Eastern United States have the potential for creating 

anomalously high amounts of indoor radon. These fault 

zones, many of which have known uranium occurrences, 

are usually characterized by high aerial radioactivity. Factors controlling the radon concentrations at these locations are bedrock uranium concentration, high permeability, and high radon emanation. These factors may be 

directly attributed to the deformation process of ductile 

shear, known as mylonitization of the rock. During 

mylonitization, the uranium concentration is increased by 

(1) the introduction of uraniferous fluids into the shear 

zone or (2) volume loss, which leaves the rock relatively 

enriched in uranium. Grain-size reduction of uraniferous 

accessory minerals common to metamorphic and igneous 

rocks such as titanite, zircon, monazite, and apatite makes 

uranium available for redistribution into the foliation. This 

process increases the emanation of radon from the rock 

dramatically. The texture imparted to the rock during 

shear also increases its permeability. Oxidation of iron 

during deformation and subsequent weathering results in 

the distinctive iron "staining" characteristic of many shear 

zones. Iron oxides and other metal oxides scavenge uranium and radium available through the weathering processes, increase the radon emanation from the rocks and 

soils, and make radon readily available to local ground 

waters. Shear zones in Pennsylvania, Virginia, New Jersey, 

and Maryland show anomalously high radioactivity and 

uranium, indoor radon, and soil radon concentrations that 

set them apart statistically from their unsheared host 

rocks. 

INTRODUCTION 

Many of the major shear zones in the Eastern United 

States have aerial radioactivity anomalies or have published 

uranium occurrences (Grauch and Zarinski, 1976; Carpenter, 1981; Baillieul and Daddazio, 1982; Baillieul and 

Dexter, 1982; Sargent and others, 1982; Madson and 

others, 1983). Shear zones have been identified as the cause 

of some of the highest indoor radon concentrations ever 

recorded in the United States. Two of the most notable of 

these occur at Boyertown, Pa.(Gundersen and others, 1987, 

1988a; Smith and others, 1987), and Clinton, N.J. (Henry 

and others, this volume). This paper documents the Boyertown radon occurrence, as well as three other case studies, 

to illustrate the geologic processes responsible for making 

shear zones a source of high radon concentrations. 

An introduction to the geologic processes that form 

mylonites and the resulting textural and mineralogical 

characteristics is essential to understanding the radionuclidic and geologic data presented in this paper. Mylonite is 

a rock type that develops as a result of ductile shear in 

which temperatures are generally above 250 °C. During 

ductile shear, the rock behaves plastically, rather than by 

fracturing, which is considered brittle shear. The development of a mylonite involves changes in the microstructure, 

porosity, permeability, and chemical composition of the 

parent rock. These changes can influence the mobility and 

concentration of uranium and may promote the emanation 

of radon (radon available to pore space). Grain-size reduction of minerals is characteristic of mylonites and is 

achieved by plastic processes (the crystals undergo ductile 

deformation, breaking down and becoming smaller in size). 

Granulation and fracturing play a minor role, especially 

with more resistant minerals such as uraniferous titanite and 

zircon. The grain-size reduction of these minerals may free 

uranium and make it available for chemical reaction and 

redistribution. Mylonitic rocks have a strong anisotropy, or 

foliation, due to the stretching and alignment of minerals 

during progressive deformation. This anisotropy may channelize fluids, which dissolve or replace minerals and thus 

change both the volume and composition of the deformed 

rock. Fluids also may interact with elements freed during 

grain-size reduction. As a result, the bulk composition of a 

mylonite often differs from that of its parent rock. Figure 22 

shows a homogeneous granite before and after deformation, 

the foliation that develops, and the mineral changes that 

take place. The change in chemistry and mineralogy of a 

rock through mylonitization is documented by Beach and 

Fyfe (1976), Beach (1980), Sinha and others (1986), and 

Sinha and Glover (1986). In the mylonite zones described 

below, there is evidence of redistribution of uranium during 

deformation by oxidizing fluids into the developing foliation of the deforming rock. This redistribution and the 

development of foliation increase the radon emanation from 

the rock, its uranium concentration, and its permeability. 

Figure 23 is a general locality map for the mylonite zones 

described here. 

Radon in Sheared Metamorphic and Igneous Rocks 39 
Undeformed 

Composed of quartz, sodium 

feldspar, potassium feldspar, biotite, 

titanite, and zircon. 

Deformed 

Composed of quartz, potassium feldspar, 

muscovite, epidote, hematite, and rutile. 

Biotite, titanite, and zircon breaking 

down and reacting. Sodium feldspar gone. 

Figure 22. Physical and mineralogical difference between undeformed and deformed granodiorite. 

N 

T 

Scale 

0 Miles 

I I 

0 200 

Kilometers 

Glen Gardner, N.J. 

Boyertown, Pa. 

Montgomery County, Md. 

Brookneal, Va. 

Figure 23. Location of shear zones in the Appalachian 

region. 

METHODS 

In each study area, techniques to assess the radionuclidic content of the soil and rocks, as well as their physical 

and chemical geologic characteristics, were used. Radon in 

soil gas was measured by use of a technique developed by 

Reimer (this volume). A carbon steel probe is inserted into 

the soil to a depth of 75 to 100 em and 10 to 20 cm3 of gas 

is withdrawn with a syringe. Samples are then measured in 

an alpha-sensitive scintillometer adapted with a Lucas cell 

and counted for 2 minutes. Three to five counts are made 

and then averaged. In the Eastern United States, this 

sampling depth corresponds approximately to the lowermost B and uppermost C soil horizons. All soils sampled in 

this study are residual, or saprolitic, soils derived from the 

underlying bedrock. Sampling was conducted in the summer during periods of dry, stable weather. In general, soils 

40 Field Studies of Radon in Rocks, Soils, and Water 

were dry to moderately moist. Radon concentrations are 

expressed in picocuries per liter (pCi/L). 

Permeability measurements are from the Soil Conservation Service County Reports and indicate water permeability. Slow permeability is defined as less than 0.6 in/h 

(inches per hour), moderate permeability is 0.6 to 2 in/h, 

and moderately rapid permeability is 2 to 6 in/h. 

Indoor radon measurements were supplied by State 

agencies and homeowners. Data from Boyertown, Pa., are 

3-month alpha-track, winter measurements. The remaining 

data are 2- to 3-day charcoal cannister, winter measurements. All data are from homes that have basements and are 

proprietary information. 

Uranium concentration was determined by fluorimetry. Thorium and radium concentrations were determined 

by gamma spectroscopy. Equivalent uranium was measured 

at the soil surface by use of a portable gamma spectrometer. 

BOYERTOWN, PENNSYLVANIA 

Radon concentrations in soil gas and their relation to 

geology were studied in Colebrookdale Township on the 

west side of Boyertown, Pa. The Boyertown occurrence 

was one of the first well-publicized discoveries of severe 

levels of indoor radon in the United States. The Proterozoic 

geology of Boyertown is described in detail by Gundersen 

and others (1987) and is only summarized here. Three 

major rock types underlie the area of interest shown on the 

map in figures 24 and 25. In the rock descriptions below, 

minerals are listed in order of decreasing abundance. 
Hornblende 

D -

\ I Qtz/Bio 

D Mylonite 

Soil radon (pCi/L) 

0 < 1000 

<> 1000-2000 

• > 2000 

N 

i Meters 

I I 

0 800 

.................................. Lim it of mapping 

Figure 24. Radon measured in soil gas for the Boyertown, Pa., area. The shaded area is underlain by hornblende gneiss. 

The stippled area is underlain by interlayered quartz-feldspar and biotite gneiss. pCi/L, picocuries per liter. 

Hornblende Gneiss 

This rock is composed of quartz, plagioclase feldspar, and at least 20 percent hornblende. Pyroxene, biotite, 

and iron-sulfides occur in variable amounts. The maximum 

uranium concentration analyzed in this rock was 5 ppm 

(parts per million). Soil-gas and indoor radon values 

are low. Soils derived from this rock type are slowly 

permeable. 

lnterlayered Quartz-Feldspar and Biotite Gneiss 

(QFB) 

Quartz-feldspar gneiss is composed of quartz, potassium feldspar, and sodium plagioclase. Biotite, titanite, 

magnetite, allanite, monazite, and rare garnet are accessories. Uranium concentrations as high as 25 ppm were 

measured. Biotite gneiss contains quartz, sodium plagioclase, and biotite and has potassium feldspar, titanite, 

magnetite, and monazite as common accessories. Uranium 

concentrations can be as high as 10 ppm. In both units, 

uranium-bearing titanite, allanite, monazite, and uraninite 

are sometimes concentrated in migmatite. These anatectic 

zones are marked by very large crystals of quartz and 

feldspar and locally produce high soil radon concentrations. 

In general, radon levels in soil and indoor radon levels are 

low to moderate for this rock unit. Soils derived from this 

rock type are moderately permeable. 

Mylonite 

Part of the QFB has been mylonitized near its contact 

with the hornblende gneiss. The mylonite differs mineralogically from the unsheared QFB by its abundant garnet. 

The mylonite's texture, defined by two foliation bands, is 

characterized by hematite and dark, fine-grained, highly 

uraniferous material. Late brittle shear or cataclasis is 

Radon in Sheared Metamorphic and Igneous Rocks 41 
I~ \ ~~ J\1~/, II 

-#fll''-1-.1' I'.,; -,'-1.,...1'' ,,,- ,,, ,,,-

Hornblende ,,,. _,, ,,,. _,, - ,, ,-,• .... - ,, ,-, ''/ ,-1'\'~''-1''/ ,-1'\'~''-1''/ 'I , __ ~,, __ /,,_ 

D -,, .. ~I,,-- ,, .. ~I,,--\ 

' Qtz/Bio 

'-/ '-, .: ' ... ' , ,'-, '-, .: ' ... ' , ,'- I \ ', ' _:: , ~ - I \ ', ' _:: ' 

~/,I, 1 1 111 <:)1, I, I I 

D Mylonite 

.._ I I' I ' .,., ~ .._ I 

, .; ,~ \ - I I \ , , -

,. - , ' , ' - , ._ I 

Indoor radon (pCi/L) 

0 <4 

0 4-200 

• > 200 

N 

i Meters 

I I 

0 800 

....... ------.................... . Limit of mapping Route 73 

Figure 25. Indoor radon for the Boyertown, Pa., area. Geology is the same as in figure 24. pCi/L, picocuries per liter. 

evident. Uranium concentrations as high as 50 ppm have 

been measured. Soils derived from this rock type are rapidly 

permeable. 

The highest indoor radon and soil radon measurements are found over the mylonite developed in the QFB. 

Uranium in the QFB is located in titanite, monazite, zircon, 

and allanite. These minerals have low radon emanation; 

much of the radon produced does not escape the mineral or 

surrounding grains. When the QFB was mylonitized, the 

uraniferous minerals were broken down, and uranium was 

made available for reaction with hot, oxidizing fluids 

present in the shear zone. During deformation, the uranium 

was redistributed into the developing foliation along with 

hematite. Uranium is a much more effective producer of 

mobile radon when it is in the foliation. The mylonite 

weathers primarily along the foliation, exposing the uraniferous surfaces. Chemical analyses of the Boyertown rocks 

show uranium and radium to be in equilibrium (Agard and 

Gundersen, this volume), which is due in part to radium 

being scavenged by iron oxides as it is produced by uranium 

42 field Studies of Radon in Rocks, Soils, and Water 

in the foliation. Radon emanation also is increased by this 

process. The Boyertown mylonite zone is structurally complex, and the source of the uranium enrichment in the zone 

is equivocal. The uranium/thorium ratio is highly variable 

in fresh rock samples of the Boyertown mylonite, and 

because veinlets of quartz are common in small, sheared 

fractures throughout the zone, it is suggested that fluid has 

been introduced into the zone, perhaps bearing uranium. 

BROOKNEAL ZONE, VIRGINIA 

The Brookneal mylonite zone near Brookneal, Va., 

bounds the western edge of the Danville basin in the 

southern Virginia Piedmont (Gates and others, 1986). The 

mylonite has developed in a homogeneous, Cambrian 

granodiorite composed of quartz, sodic plagioclase, minor 

hornblende, biotite, and titanite. Soil-radon concentrations 

show a positive correlation with the amount of shear 

measured in the underlying mylonitic outcrop (Gates and 
Brookneal Mylonite Zone 

GR: 70 to 90 cps 

CIS Angle: 42°to 1~ 

Radon In Soil Gas (pCI/U 

scale • <500 

0 1

1 mile • 500-1000 

I I 0 1001-2000 

0 1 km * >2000 

->-- Road 

Railroad Track 

Figure 26. Summary of data for the Brookneal mylonite zone. Surface gamma radiation (GR) was measured in counts per 

second (cps) with a scintillometer, and the angle between the C and S bands was measured in degrees. Uranium and 

radon both increase as the CIS angle becomes smaller. pCi/L, picocuries per liter. 

Gundersen, 1988). In the Brookneal zone, the amount of 

shear was measured by determining the angle between the 

two foliation bands developed during deformation. These 

are known as C and S foliation bands (Berthe and others, 

1979; Simpson and Schmid, 1983; Simpson, 1984). The 

smaller the angle between the C and S bands, the greater the 

amount of shear strain. The C band forms initially at an 

angle of 45° to the S band. This angle becomes increasingly 

smaller with progressive shearing. Therefore, the smaller 

the CIS angle the greater the shear strain. Figure 26 is a 

summary map of the area showing the geology, the angle 

between C and S bands, and soil-radon concentrations. The 

angle between the C and S bands was measured on the 

outcrop exposed along the railroad track. Radon in soil was 

measured in the moderately permeable soil directly overlying the outcrop and along a road on top of the ridge that is 

above the outcrop. Uranium was measured in 10 of the 

rocks for which the C and S angles were measured. The 

correlation among uranium, soil radon, and the CIS angle is 

shown in figures 27 and 28. These results clearly show that 

soil-radon and uranium concentration in the rock increases 

with increasing shear. Uranium and radon both increase as 

the CIS angle becomes smaller. The progressive breakdown 

of the rock is directly linked to changes in chemical and 

physical composition with increasing shear. 

The Brookneal zone is a good example of the relative 

enrichment of uranium by volume loss. Figure 27 A shows 

that the uranium-thorium ratios change little with increasing 

shear. Thorium is considered an immobile element; thus, it 

appears that new uranium has not moved into the system to 

Radon in Sheared Metamorphic and Igneous Rocks 43 
y = 5.3 + 1.9x R = 0.95 

24 

20 

-

E 16 

c. 

c. 12 -.c a 

1-

4 

0 

0 2 4 6 a 1 0 

u (ppm) 

10 . B 

a-. • - • E 6-

c. . • 

c. 4- - •• 

:::> • • 2-. • • 0 I I I I . I . I I 

0 1 0 20 30 40 50 

C/S angle 

10 . c 

a- • - . 

E • 6-

c. • 

c. 4- -

:::> 2-

. • 

-

• • • 0 . I . I I I I I 

0 400 aoo 1200 

Soil radon (pCi/L) 

Figure 27. A, Uranium versus thorium for samples taken 

from outcrop along the railroad track. 8, Uranium versus 

the angle between the C and S bands, as measured in the 

same samples. C, Uranium measured in outcrop samples 

versus radon measured in the overlying soils (along the 

railroad track). pCi/L, picocuries per liter; ppm, parts per 

million. 

44 Field Studies of Radon in Rocks, Soils, and Water 

cause the increase in uranium concentration. Instead, other 

elements have moved out, especially silica and sodium, 

creating a relative enrichment of uranium in the mylonite as 

a result of volume loss. 

GLEN GARDNER, NEW JERSEY 

The Glen Gardner area was originally mapped by 

Markowitz (1975) and shows a number of mylonite zones 

occurring at the contacts between different rock types or 

crossing several different rock types. Indoor radon and soilradon concentrations are high within the mylonite zone 

shown in figures 29 and 30. Four major lithologies are 

associated with the mylonite. 

Hornblende Granite 

Most of the Proterozoic gneiss in the area has been 

mapped as hornblende granite. This slightly variable rock 

type is commonly composed of quartz, potassium feldspar, 

sodium feldspar, and hornblende. Accessories include titanite, monazite, zircon, epidote, magnetite, allanite, and 

biotite. Permeability in the amphibolite is moderate. In the 

unsheared gneiss, soil radon concentration is moderate to 

low as is the indoor radon concentration. Uranium concentration in the rock varies between 2 and 8 ppm. 

Amphibolite 

A small body of hornblende amphibolite flanks the 

mylonite zone to the northeast. Hornblende, biotite, quartz, 

and sodic plagioclase are the principal minerals present. 

Abundant titanite, zircon, and magnetite occur as accessories. Permeability is slow in soil derived from the amphibolite. Soil radon is low to moderate, and indoor radon is 

low. Uranium concentration in the rocks varies between 1 to 

3 ppm. 

Magnetite Ore 

Three abandoned magnetite pits are located along the 

northern edge of the mylonite zone. The magnetite ore is 

made up of magnetite and pyrrhotite interlayered with 

sillimanite and quartz gangue. Uranium concentration varies from 2 to 5 ppm in the magnetite ore, and radon 

concentrations over the ore were low to moderate. The 

immediate host of the ore body is a more amphibolitic facies 

of the hornblende granite and a biotite-sillimanite gneiss 

containing local layers of monazite. The biotite-sillimanite 

gneiss yields moderate to high radon concentrations and has 

uranium concentrations as high as 28 ppm where it has been 
10,000 . 

. ..-... . ...J • -- • • 0 • • c. 

~ e 0 

•• .,. c::: 1,000-

0 O(X) 0 01 0 "'C ~0 0 0 

0 as I I.. • 

0 

en 

100 . I . I -.- I . I 

0 1 0 20 30 40 50 

CIS angle in degrees 

0 Soil radon (pCi/L) (RR) • Soil radon (pCi/L) (road) 

Figure 28. Radon in soil along the railroad track (RR) and radon in soil measured along the road on top 

of the ridge versus the angle between the C and S bands. pCi/L, picocuries per liter. 

sheared. Soil derived from the magnetite varies in permeability from slow to moderate. 

Mylonite 

Deformed hornblende granite, minor hornblende 

gneiss, and minor magnetite ore are found in the main 

mylonite zone. Where mylonite is developed in the hornblende granite, iron oxides are common on the surface of 

the rock, and the mylonite is composed of quartz and 

sericitized feldspar. Foliations are composed of minor 

biotite, epidote, hematite, and muscovite. Soil derived from 

the mylonite is moderately permeable. Uranium appears to 

be amorphous in association with hematite in the foliation 

and varies in concentration from 5 to 20 ppm. Processes 

similar to those that occurred in the Boyertown mylonite are 

the reason that uranium and radon concentrations in the 

mylonite are high here. 

MONTGOMERY COUNTY, MARYLAND 

In a recent study of Montgomery County, the radon 

potential of Piedmont metamorphic rocks was found to be 

substantially lower than their sheared counterparts. Figure 

31 shows a generalized version of the radon potential map 

developed for the county (Gundersen and others, 1988b). 

The map units are rated 1, 2, and 3 in order of increasing 

radon potential. A map unit rated 1 indicates that less than 

40 percent of the homes in this rating area will have indoor 

radon screening levels greater than 4 pCi/L. All indoor 

radon screening levels will be in the range of 1 to 20 pCi/L. 

A map unit rated 2 indicates that about 50 percent of the 

homes will have indoor radon screening levels greater than 

4 pCi/L, and as many as 10 percent of these will be over 20 

pCi/L. A radon potential rating of 3 indicates that 60 

percent or more of the homes in this area will be greater 

than 4 pCi/L and as many as 30 percent of the homes will 

be greater than 20 pCi/L. These ratings are based on 567 

measurements of soil radon, 278 measurements of surface 

equivalent uranium, and 319 charcoal cannister measurements of indoor radon. These data were then compared with 

available geologic maps by Cloos ( 1964) and Froelich 

(1975) and permeability data from the Soil Conservation 

Service for Montgomery County. 

The high-potential area in the western part of the 

county (3p) is underlain by phyllite that is characterized by 

high uranium concentrations not caused by shearing of the 

rock. Uranium in the phyllite is associated with graphite and 

is probably of depositional origin. However, the remaining 

Radon in Sheared Metamorphic and Igneous Rocks 45 
0 < 500 

500-2000 

• >2000 

Meters 

0 

·::·······.\ 

·· .... ,. ..... 

I 

500 

Road 

Contact 

' , I 

Figure 29. Radon in soil gas in the Glen Gardner area. Am, amphibolite; Gh, hornblende granite; and Myl, mylonite. 

areas rated 3 have high indoor radon and soil radon levels 

caused by mylonitic shear zones. The shear zones in 

Montgomery County yielded the highest average soil radon 

(2,300 pCi/L) and the highest average indoor radon (24 

pCi/L) when compared with the unsheared rocks. The three 

rock types in which shears are developed are described 

below. 

Schist, Map Units 2s, 3s, and 3p/s 

This rock unit underlies a significant portion of the 

central and eastern part of the county. It is composed of 

quartz, feldspar, and biotite with varying amounts of 

muscovite, chlorite, magnetite, staurolite, and garnet. 

Allanite, apatite, titanite, monazite, and zircon commonly 

occur as accessories and are the source of uranium in the 

rock. Interlayers of quartzite, metagraywacke, and phyllite 

46 Field Studies of Radon in Rocks, Soils, and Water 

are common. Equivalent uranium measurements average 

2. 7 ppm and have a maximum of 6. 7 ppm where the schist 

is sheared. Permeability of soils developed from this rock 

type is moderate. Most of the schist is rated 2, but where it 

is sheared it is rated 3. In general, soil radon ranges between 

500 and 1 ,500 pCi/L in unsheared schist. Where the schist 

is sheared, the range is between 2,000 and 3,000 pCi/L. 

Indoor radon ranges between 5 and 30 pCi/L in the sheared 

schist and between 1 and 10 pCi/L in the unsheared schist. 

Gneiss, Map Units 2g and 3g 

Numerous bodies of gneiss occur within the schist. 

They are composed of quartz, potassium feldspar, sodium 

feldspar, and variable amounts of hornblende and biotite. 

Granodiorite and pegmatite are common. Equivalent uranium measurements average 2.4 ppm and have a maximum 

of 3. 7 ppm in sheared gneiss. Permeability of soils is 
Indoor radon 

(pCi/L) 

0 

0 

<> 

• 

4 

> 4-20 

>20 

Meters 

I 

500 

Road 

·:::··"' ····= Contact ·· ....... · 

Figure 30. Indoor radon for the Glen Gardner area. Am, amphibolite; Gh, hornblende granite; and Myl, mylonite. 

moderate. In the southern part of the county, the gneiss is 

characterized by a well-defined mylonitic texture. The 

northern outcrops of gneiss have a few scattered, narrow 

(1-10m) mylonite zones. High indoor radon and soil-radon 

concentrations are found in all mylonite developed in 

gneiss. In general, soil-radon concentrations range between 

2,000 and 3,000 pCi/L in the sheared gneiss and in the 

unsheared gneiss range between 250 to 1 ,500 pCi/L. Indoor 

radon concentrations range between 5 and 30 pCi/L in 

sheared gneiss and in the unsheared gneiss range between 1 

and 10 pCi/L. 

Mafic and Ultramafic Rocks, Map Units 1m, 2m, 

and 3m/s 

Mafic and ultramafic bodies commonly occur within 

the schist and are typically bordered by shear zones. The 

rocks vary and include greenschist, quartz diorite, tonolite, 

amphibolite, metagabbro, serpentine, and chloriteactinolite-talc schist. Permeability is slow in soils developed on this rock type. The igneous mafic rocks typically 

have a low uranium concentration, with equivalent uranium 

averaging 2.1 ppm and having a maximum of 4 ppm in the 

sheared mafic rocks. The source of uranium is probably 

from the adjacent sheared schist, and in a few rare cases, 

gneiss. In general, soil-radon concentrations in the 

unsheared mafic rocks range between 200 and 1 ,000 pCi/L 

and in the deformed mafic rocks range between 2,000 and 

3,000 pCi/L. Indoor radon measurements of 4,000 pCi/L 

have been found in the map unit 3m/s, and, in general, 

indoor radon measurements range between 10 and 30 pCi/L 

in the sheared mafic rocks. 

Radon in Sheared Metamorphic and Igneous Rocks 47 
Radon Potential of Rocks and Soils in 

Montgomery County, Maryland 

scale 

0 Smiles 

0 Skm 

Figure 31. Radon potential for Montgomery County, Md. 

The numbers in each map unit label indicate low (1), 

moderate (2), and high (3) radon potential. The letter in 

each map unit label indicates the rock type: phyllite (p), 

schist (s), gneiss (g), sandstone (ss), diabase (d), siltstone 

DISCUSSION AND CONCLUSIONS 

The results of this study indicate that mylonites create 

anomalously high indoor radon and soil radon concentrations. From the rock descriptions and data presented, it is 

evident that each rock type has a distinctive radionuclidic 

signature. A plot of the average indoor radon versus the 

average soil-radon concentrations for the mylonite zones 

and associated rock types discussed in this paper is shown in 

figure 32. Data from studies in Easton, Pa., have also been 

included (Gundersen and others, 1988a). Note that the 

rocks cluster in three catagories. These catagories are 

controlled by the rock composition, the radionuclidic concentration, and the permeability. Rocks composed chiefly 

48 Field Studies of Radon in Rocks, Soils, and Water 

N 

I 

(st),mafic (m), mylonite along the phyllite schist contact 

(p/s), mylonite along the mafic schist contact (m/s), quartzite (qt), or terrace gravel (tg). The following areas also have 

mylonite zones: 3g, 3s, and 2m. Modified from Gundersen and others, 1988b. 

of dark-colored minerals such as hornblende, pyroxene, and 

biotite (commonly called mafic rocks) seldom have uranium 

concentrations of more than 5 ppm. Permeability is slow in 

mafic rocks because the dark minerals often weather to 

clay. The mafic rocks in all of the case studies generally 

have soil radon values less than 500 pCi/L and indoor radon 

values less than or equal to 4 pCi/L, except where they are 

sheared. 

Uranium concentrations are higher in rocks of granitic composition, such as the QFB, schist, gneiss, and 

hornblende granite, because of the occurrence of minerals 

such as allanite, monazite, zircon, and titanite. These 

uraniferous minerals are common in metamorphosed sedi-
~ 

0 

1poo~-----------------------------------, 

Bmyl• Egh 

• 

S: 100 Gmyl 

• c 

0 

, 

~ 

... 

0 

0 

, 

c 

10 

p 

QFB e 

• Mafic fl' s 

.~ G 

MCmyl 

• 

1+-~--~~--.-~--~~~~--~-r--~~ 

0 1,0 0 0 2,0 0 0 3,0 0 0 4,0 0 0 5,0 0 0 6,0 0 0 

Soil radon (pCi/L) 

Figure 32. Average indoor radon versus average soil-radon 

concentrations for the areas described in this paper and 

for Easton, Pa. The correlation coefficient, or R factor, is 

0.82. The four points labeled "Mafic" are two biotite 

schists from Easton and Boyertown, ultramafic rocks from 

Montgomery County, and an amphibolite from Glen 

Gardner. 5, quartz-feldspar-biotite schist from Montgomery County; G, quartz-feldspar gneiss from Montgomery County; QFB, interlayered quartz feldspar and 

biotite gneiss from Boyertown; P, phyllite from 

Montgomery County; Gmyl, mylonite from Glen Gardner; MCmyl, mylonite from Montgomery County; Bmyl, 

mylonite from Boyertown; and Egh, sheared granite 

gneiss from Easton. pCi/L, picocuries per liter. 

mentary rocks and granites. Soils derived from them are 

sandier and more permeable because of the abundance of 

quartz. Most of the rocks have moderate amounts of 

uranium (5 to 25 ppm) and moderate amounts of soil radon 

(500 to 2,000 pCi/L). 

Mylonites formed in the various rock types are 

consistently moderate to high in radon and uranium 

concentrations. Several factors contribute to the high radon 

values in mylonites. First, uranium increases in 

concentration relative to the parent rock. Uranium is 

removed from its crystalline source in minerals such as 

titanite and reacts with oxidizing fluids present in the 

developing mylonite. As shear strain increases, grain-size 

reduction (the breaking down of the minerals) increases, 

and more uranium is mobilized and concentrated in the 

foliation. Concentrations increase by two processes: (1) 

new uranium is brought into the zone by fluids and (2) 

uranium is left in the zone as other elements leave the 

system and thus cause volume loss and relative enrichment 

of uranium. 

Second, emanation of radon from uranium increases 

in the foliation. Uranium is removed from a site of low 

radon emanation (the crystal) to a site of high radon 

emanation (the foliation). Weathering of mylonites occurs 

mostly along foliations and exposes the source of uranium 

even further. 

Third, the foliation developed during mylonitization 

increases the permeability of the rock dramatically. This 

pervasive foliation is also mimicked in the soil profile and 

provides paths for water and air movement. 

In conclusion, shear zones can be local as well as 

regional areas of high radon concentrations, especially in 

mountain belts such as the Appalachians. Shear zones are 

not the only cause of high indoor radon levels, and some 

shear zones will not create radon problems. Shears 

developed in rocks having less than 1 ppm uranium may not 

produce sufficient radon to cause a problem unless uranium 

is introduced from another source during deformation. 

However, shear zones developed in rocks having higher 

uranium concentration, such as granitic rocks, have a high 

probability of causing an indoor radon problem. 

High radon levels in water accompany high soil radon 

in Boyertown, Pa. (Wanty and Gundersen, 1988). 

Preliminary water data from two other shear zones, the 

Hylas fault in Virginia and a brittle shear fault in the Silver 

Plume Quartz Monzanite near Conifer, Colo. , indicate that 

many domestic wells have radon concentrations greater than 

10,000 pCi/L. High radon emanation, especially along 

fracture surfaces, contributes significantly to radon 

concentrations in water. Mylonites tend to be aquifers 

because of the increased permeability caused by the shear 

bands formed during deformation, whereas the same rock, 

when not sheared, may not be an aquifer. 

ACKNOWLEDGMENTS 

This study was funded by the U.S. Geological Survey 

and the Department of Energy. The author would like to 

thank C.R. Wiggs, C.A. Rice, and L.M. Hauser for their 

assistance in the field; A.E. Gates, J.M. Crespi, R.R. 

Schumann, and R.B. Wanty for helpful discussion; and 

R.T. Peake and J.P. Smoot for editorial comments. 

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Sinha, A.K., and Glover, L., III, 1986, U-Pb systematics of 

zircons during dynamic metamorphism-A study from the 

Brevard zone: Contributions to Mineralogy and Petrology, v. 

66, p. 305-310. 

Sinha, A.K., Hewitt, D.A., and Rimstidt, J.D., 1986, Fluid 

interaction and element mobility in the development of 

ultramylonites: Geology, v. 14, p. 883-886. 

Smith, R.C., II, Reilly, M.A., Rose, A.W., Barnes, J.H., and 

Berkheiser, S. W., Jr, 1987, Radon: A profound case: 

Pennsylvania Geology, v. 18, p. 1-7. 

Wanty, R.B., and Gundersen, L.C.S., 1988, Groundwater geochemistry and radon-222 distribution in two sites on the 

Reading Prong, Pennsylvania, in Marikos, M., ed., 

Proceedings of the GEORAD Conference: Geologic Causes 

of Radionuclide Anomalies: Missouri Department of Natural 

Resources Special Publication No. 4 , p. 147-156. 
THE GEOLOGY AND GEOCHEMISTRY OF SOILS IN BOYERTOWN AND EASTON, 

PENNSYLVANIA 

Sherry S. Agard and Linda C.S. Gundersen 

Abstract 

Soils derived from a wide variety of metamorphic 

rocks in the Reading Prong, Pennsylvania, exhibit secular 

equilibrium between uranium and radium. Direct 

correlations between uranium, radium, radon in soil gas, 

and indoor radon indicate that radon in soil gas is 

attributable to the uranium content of the soils and can be 

used predictively to estimate levels of indoor radon. 

Permeability of the soils does not vary enough to affect the 

radon availability except where fractured and jointed 

bedrock is close to the surface, in which case convective 

flow, rather than diffusion, becomes the dominant radon 

transport mechanism. Radon emanation of soils, as measured in the laboratory, correlates well with radium, radon 

in soil gas, and indoor radon. Careful examination of the 

physical and chemical properties of the soil must be made 

in order for radon in soil gas to be used as an effective 

predictor of indoor radon levels. In addition, predictions 

of indoor radon levels based on radon in soil gas and 

geology are limited to ranges of values because of the 

inherent variability in soil makeup. 

INTRODUCTION 

The Reading Prong in the Northeastern United States 

is underlain by a complex sequence of Proterozoic metasedimentary and metaigneous rocks, many of which contain 

abundant uranium. As uranium-238 decays, it produces 

radium, which in tum decays to radon. Radon migrates into 

buildings under the influence of negative pressure 

differentials between the structure and the underlying 

bedrock or soil. When radon concentrates in indoor air, it 

can become a health problem (Environmental Protection 

Agency, 1986). Although the uranium and radium content 

of the bedrock is ultimately responsible for the presence of 

radon, it is often the porous and permeable nature of the 

overlying "soil" that allows the radon to migrate. As the 

uranium-bearing bedrock weathers both physically and 

chemically, it produces residuum and soils that differ, often 

significantly, from their parent material. 

Two areas in the Reading Prong, Boyertown and 

Easton, Pa. (fig. 33), were selected for detailed study to 

examine the relation of geology, radon in soil gas, and 

indoor radon (see Gundersen, this volume, for a more 

detailed discussion of the geology). This paper discusses 

some preliminary data on the physical properties of surface 

soils as they may influence radon availability and 

migration. Radon in soil gas was measured by use of the 

methods of Reimer (this volume) at a depth of 75 em, which 

corresponds to the lowermost B horizon or the upper C 

horizon in these soils. Indoor radon measurements were 

volunteered by the homeowners and are proprietary 

information. In general, the indoor radon measuremen.ts 

were made in basements during a 3-month period during the 

winter of 1984-85 by use of alpha-track devices. All the 

houses used in this study have basements. 

GEOLOGY OF BOYERTOWN AND EASTON 

Studies of radon in soil gas and geology were done in 

Colebrookdale Township on the west side of Boyertown, 

Pa., where one of the first cases of severe indoor radon in 

the United States was discovered (Smith and others, 1987). 

The following is a brief description of the three major rock 

types shown on the map in figure 34, which was derived 

from original mapping by Gundersen. 

Hornblende gneiss.-This rock is composed of 

quartz-plagioclase feldspar and hornblende (>20% ). Pyroxene, biotite, and iron sulfides occur in variable amounts. 

The rock is moderately foliated and jointed, but folds are 

not evident on the scale of outcrops. In general, both the 

soil-gas and indoor radon values are low for this unit 

( < 1 ,000 pCi/ L (picocuries per liter) and <4 pCi/L, 

respectively). 

Interlayered quartz-feldspar and biotite gneiss 

( QFB). -The quartz-feldspar gneiss comprises quartz, 

potassium feldspar, and sodium plagioclase. Biotite, titanite, magnetite, allanite, monazite, and rare garnet are 

accessories. The biotite gneiss contains quartz, sodium 

plagioclase, and biotite, with potassium feldspar, titanite, 

magnetite, and monazite as common accessories. This unit 

is weakly to moderately foliated and well jointed. Folds are 

not evident on the scale of outcrops. In both units, uraniumbearing titanite, allanite, monazite, and uraninite are 

sometimes concentrated in local anatectic zones. These 

zones of local melting are marked by very coarse crystals of 

quartz and feldspar and can produce local radon anomalies. 

In general, soil-gas radon and indoor radon for this unit is in 

the low to moderate range (200-2,000 pCi!L and 1-20 

pCi/L, respectively). 

Mylonite.- Near its contact with the hornblende 

gneiss, part of the QFB has been mylonitized. The mylonite 

is composed of deformed quartz-feldspar gneiss interlayered with minor biotite gneiss. It differs mineralogically 

from the undeformed QFB because it contains abundant 

garnet. The mylonitic texture, defined by C and S foliation 

bands, is characterized by dark, fine-grained, highly uraniferous material. The unit is highly foliated, and folds are 

Soils in Boyertown and Easton, Pennsylvania 51 
80° 

Pennsylvania 

400 

0 Miles 50 I I I I - Reading Prong 0 Kilometers so 

Figure 33. Locations of study areas in the Reading Prong. 

abundant on the scale of outcrops. The strong anisotropy of 

the rock gives it a distinct weathering profile. In general, 

soil-gas radon and indoor radon measurements in this unit 

are high (1,000-12,000 pCi/L and >20 pCi/L, 

respectively). 

Chestnut Hill in Easton, Pa., is underlain by Proterozoic metasediments that possibly represent an ancient reef 

assemblage. It is fault bounded on either side by the 

Cambrian Leithsville Formation. The sequence is tightly to 

isoclinally folded at map scale. The geology of this area was 

compiled from Drake (1969), and additional fieldwork was 

done by the authors. A geologic map of the area is shown in 

figure 35. The following is a description of the three main 

rock types. 

Marble.- This unit is composed of dolomite, calcite, 

serpentine, tremolite, phlogopite, and talc. Pyroxene gneiss 

is interlayered with the marble along its northern contact. 

Uraninite and exotic uranium- and thorium-bearing 

minerals are concentrated where the marble is locally 

intruded by albitic pegmatite. In general, radon in soil gas 

is moderate to high (1 ,000 to 5,000 pCi/L). 

Sillimanite gneiss. -This unit is composed of quartz, 

potassium feldspar, sodium plagioclase, and sillimanite. 

Uranium content is low in the sillimanite gneiss, except 

where it is intruded by tourmaline-bearing pegmatite near 

its contact with the quartz-feldspar gneiss. Soil-gas radon 

52 Field Studies of Radon in Rocks, Soils, and Water 

levels vary from low to moderate; some high values 

(>2,000 pCi/L) were recorded along contacts with other 

units. 

Quartz-feldspar gneiss. -Potassium feldspar, quartz, 

biotite, and magnetite are the major constituents of this unit. 

Accessories include uranium-bearing titanite, monazite, 

and zircon. Uraninite occurs in quartz-filled shears, as 

much as 0. 7 m long, in a discontinuous zone subparallel to 

strike. In the eastern part of Chestnut Hill, biotite gneiss 

forms a mappable layer within the quartz-feldspar gneiss. It 

is composed of quartz, potassium feldspar, sodium plagioclase, biotite, and rare magnetite layers. Local anatexis has 

produced coarse-grained quartz-feldspar knots with 

abundant uranium-bearing titanite and monazite similar to 

those observed in Boyertown. In general, the biotite gneiss 

has low radon levels in soil gas ( < 1,000 pCi/L). The 

quartz-feldspar gneiss generally has moderate to high radon 

levels in soil gas and indoors (1,000 to 5,000 pCi/L and 20 

to 100 pCi/L, respectively.) 

DEFINITION AND GENERAL PROPERTIES OF 

SOILS 

The term "soil" has many definitions, depending on 

its usage. To the engineering geologist, soils include all 

unconsolidated surficial materials above the bedrock. To 
Hornblende 

D ' I Qtz/Bio 

D Mylonite 

N 

i Meters 

I 

0 

I 

800 

---···-------~---· Limit of mapping 

Route 73 

Figure 34. Geology of the Boyertown study area, located in the northeast portion of the Boyertown 7 1/2-minute 

quadrangle. Labels indicate approximate locations of soil profiles (some of which are listed in table 6). Qtz/Bio, 

interlayered quartz-feldspar and biotite gneiss. 

the soil scientist, a soil is a collection of natural earthy 

materials containing living matter and capable of supporting 

plants. A definition by Birkeland (1984, p. 3) will serve to 

define soil as used in this study: " ... a natural body consisting of layers or horizons of mineral and/or organic constituents of variable thickness, which differ from the parent 

material in their morphological, physical, chemical, and 

mineralogical properties and their biological characteristics .... " 

Soils are formed by an interaction of geomorphologic 

and pedologic processes that result in a distinct vertical 

arrangement of horizons, called the soil profile. A distinction can be made between a soil profile and a weathering 

profile in that the soil profile is generally limited to the 

upper, layered horizons within a much thicker weathering 

profile. The physical characteristics of the entire weathering 

profile, including the upper soil horizons, are significant in 

controlling the availability and migration of radon. This 

study focused on the upper horizons because ( 1) most 

houses are built on or in this zone, in some cases without 

much disturbance of the profile but in many cases with great 

disruption; (2) the layered nature of the soil profile produces 

a marked anisotropy in the physical properties; (3) in much 

of the previous work on soils and radon, a certain amount of 

homogeneity for "soil" has been assumed by treating all 

weathered and unconsolidated material above solid bedrock 

as a single unit; and (4) many of the in situ tests for radon 

in soil gas are conducted in these upper soil horizons, and 

some differences attributed to inherent differences in soils 

between areas may instead be due to differences between 

horizons. 

The soil profile consists of several master horizons, 

the properties of which are related to the vertical movement 

and accumulation of certain materials, such as organic 

matter, clay, or iron. The A horizon forms at the surface as 

organic matter accumulates and clays and soluble salts are 

Soils in Boyertown and Easton, Pennsylvania 53 
N 

i 

D 

I 

I 

D 

Quaternary 

Lower Cambrian 

carbonates 

Quartz-feldspar 

gneiss 

Sillimanite 

gneiss 

Marble 

I Biotite gneiss 

J Fault 

J Contact 

Figure 35. Geology of the Easton study area, located in the northeast portion of the Easton 7 1/2-minute quadrangle. 

Labels indicate approximate locations of soil profiles (some of which are listed in table 6). 

transported to lower horizons. The underlying B horizon is 

characterized by clay accumulation, red color due to the 

oxidation of iron, accumulation of iron compounds, and 

continued leaching of soluble materials. The B horizon 

develops characteristic structures as individual soil particles 

become aggregated into peds. The C horizon consists of 

weathered parent material~ clays and iron oxides accumulate 

here to a much lesser extent than in the B horizon, and 

structures are less distinct. 

Nazaroff and others (1988) summarized some of the 

major physical properties of soil that control radon availability and migration, specifically grain size, permeability, 

porosity, and moisture content. The permeability of a soil is 

a measure of how easily air or water will flow through it and 

is often cited as one of the most significant factors controlling indoor radon accumulation. Permeability is not a 

fundamental soil property but is instead controlled by grain 

size, shape, and distribution; porosity (void ratio)~ mineralogy; degree of saturation; soil fabric; nature and temperature of fluid; and type of flow. The soil fabric is particularly important because it relates to the natural state of a soil 

in situ and includes porosity and permeability, which are 

due to soil structure and root pores that are generally 

destroyed during most sampling and testing procedures. 

54 Field Studies of Radon in Rocks, Soils, and Water 

Figure 36 shows that the range of permeabilities of 

common soil types is more than 10 orders of magnitude 

(Nazaroff and others, 1988). The permeability within a 

given soil profile can vary by 2 orders of magnitude or more 

because the textural and structural properties of different 

horizons vary. Permeability can also vary horizontally and 

vertically within a particular horizon by up to 2 orders of 

magnitude. This natural variability increases the problems 

of understanding and predicting radon migration; construction activities that disturb the natural soils add to these 

problems. The clayey B horizon, especially when saturated, 

may act as a cap that inhibits the vertical migration of radon 

gas. However, once drained, even very clayey B horizons 

will have enough permeability, because of texture and soil 

structures, to allow radon migration. Nazaroff and others 

( 1988) noted that the value of the air permeability remains 

roughly constant and equal to that for dry soil until moisture 

content exceeds field capacity. (Field capacity is the amount 

of water that is held on soil particle surfaces against 

gravitational pull.) For the textures of the soils derived from 

crystalline bedrock, the associated permeabilities are 

around 10- 12 m2 , which is adequate to allow radon to 

migrate. Therefore, the soil texture and its associated 

permeability are only limiting factors when the moisture 

content is well above field capacity. 
Representative Soil Permeabilities (m2) 

1 o-7 1 o-a 

Clean 

gravel 

_"2 

E ns ... Ul 

g~ c ... :::>CU 8 

I ' 

1 o-9 

"C 

c - ns E cn 

o -"2 ~:::::J E E ns 

C·- .gcn =>i ·- Q) c c: E :::> ·--

10-10 ' I 

10-11 ' 

Clean sand and 

gravel mixtures 

~ >. ·en ns >. 0 E ns ... >. 0 0 "C ~ 

c 

c 

ns ~ :::> en Ci) 

' ' ' I 

1 o-12 1 o-13 10-14 1 o-1s 

Very fine sands and mixtures 

of sand, silt, and clay 

~ 

0 

' I 

1 o-1s 

Clay 

Figure 36. Typical soil permeabilities (modified from Nazaroff and others, 1988, p. 62). Permeability is 

expressed as specific (or intrinsic) permeability, usually in units of centimeters squared, which is based on the 

physical properties of the soil medium without regard to the characteristics of the fluid. 

SOILS OF BOYERTOWN AND EASTON 

Natural and manmade vertical exposures provide the 

best sites for describing and sampling soils, but in the 

developed areas of Boyertown and Easton, these were 

generally not available. In most areas, augering provided 

adequate general information, although horizon depths, 

boundaries, and some structural features could not be 

described accurately. The gravelly nature of some of the 

soils precluded augering more than 30 to 40 em, so the 

nature of the lower B and C horizons could not always be 

determined. In a few key areas, small pits were excavated 

by hand to a depth of 7 5 to 150 em. After each soil was 

described, 2 to 5 kg of soil material (the fraction less than 

about 1 em) were collected from each horizon for laboratory 

analysis. 

Soils in the Chestnut Hill-Easton area are part of the 

Conestoga silt loam and Conestoga-Hollinger extremely 

stony silt loam (Soil Conservation Service, 1974). The 

sampled soils developed on the quartz-feldspar gneiss, 

sillimanite gneiss, and pegmatites are generally thinner and 

sandier than the Soil Conservation Service (SCS) type 

profile. The generalized composite description that follows 

is shown schematically in figure 3 7. 

Easton quartz-feldspar gneiss and sillimanite gneiss: 

Ap-0 to 15 em; silt loam to sandy loam; moist color 10YR 

3/2 (very dark gray brown); single grain to weak, 

fine, subangular blocky structure; loose, nonsticky, 

nonplastic consistence. 

BA-15 to 20 em; sandy loam; moist color 10YR 3/4 (dark 

brown); weak, fine, subangular blocky structure; very 

friable, nonsticky, nonplastic consistence. 

Bt-20 to 50 em; sandy clay loam to loamy sand; moist 

color 7 .5YR 5/6 (strong brown); weak to moderate, 

fine to medium, subangular blocky structure; friable, 

slightly sticky, slightly plastic consistence; abundant 

thin clay films. 

BC-50 to 70 em; loamy sand to sand; moist color 1 OYR 

4/4 (dark yellowish brown); weak, fine, subangular 

blocky structure; very friable, nonsticky, nonplastic 

consistence. 

C-70 to llO+cm; loamy sand to sand; moist color 10YR 

4/6 (dark yellowish brown); single grain structure; 

loose, nonsticky, nonplastic consistence. 

Soils in the Gablesville-Boyertown area are part of 

the Chester channery silt loam (SCS, 1970). The soils 

developed on the biotite gneiss and hornblende gneiss are 

sandier but similar to the SCS type profile. The soils 

developed on the quartz-feldspar gneiss, particularly in the 

mylonitic zone, are much thinner and coarser (50 to 80% 

coarse fragments). The composite descriptions that follow 

are shown schematically in figure 37. 

Boyertown quartz-feldspar gneiss: 

Ap-0 to 15 em; very gravelly silt loam to sandy loam; 

moist color 10YR 3/3 (dark brown); single grain to 

weak, fine, subangular blocky structure; very friable, 

nonsticky, nonplastic consistence. 

Bt-15 to 45 em; very gravelly sandy loam to loamy sand; 

moist color 7 .5YR 6/6 (reddish yellow) to 10YR 5/6 

Soils in Boyertown and Easton, Pennsylvania 55 
Depth 

(em) 

0 

60 

100 

160 

1ml 

Easton 

quartz-feldspar 

gneiss and 

sillimanite gneiss 

Boyertown 

quartz-feldspar 

gneiss 

Boyertown 

biotite gneiss and 

horneblende 

gneiss 

Figure 37. Representative soil profiles from Boyertown and Easton, Pa. See text for detailed discussion. 

(yellowish brown); weak to moderate, fine to 

medium, subangular blocky structure; friable, 

slightly sticky, slightly plastic consistence; abundant 

thin clay films. 

BC -45 to 60 em; very gravelly sandy loam to loamy sand; 

moist color 7 .5YR 617 (reddish yellow) to 10YR 6/6 

(brownish yellow); weak, fine, subangular blocky 

structure; very friable, slightly sticky to nonsticky, 

slightly plastic to nonplastic consistence. 

C-60 to 95 + em; very gravelly loamy sand to sandy loam; 

moist color 7 .5YR 5/6 (strong brown); single grain to 

weak, fine, subangular blocky structure; loose, nonsticky, nonplastic consistence. 

Boyertown biotite gneiss and hornblende gneiss: 

Ap-0 to 15 em; channery silt loam to sandy loam; moist 

color 10YR 3/3 (dark brown) to 7 .5YR 3/4 (dark 

brown); single grain to weak, fine, subangu1ar blocky 

structure; loose to very friable, slightly sticky to 

nonsticky, slightly plastic to nonplastic consistence. 

BA-15 to 25 em; channery to gravelly, loam to sandy clay 

loam; moist color 10YR 4/3 (dark brown); weak to 

56 Field Studies of Radon in Rocks, Soils, and Water 

moderate, very fine to fine, subangular blocky structure; very friable, sticky, plastic consistence; many 

thin clay films. 

Btl-25 to 50 em; channery to gravelly, sandy loam to 

sandy clay loam; moist color 7 .5YR 4/6 (strong 

brown) to 5YR 3/4 (dark reddish brown); moderate to 

strong, fine to medium, subangular blocky structure; 

very friable, sticky, plastic consistence; abundant thin 

to thick clay films. 

Bt2-50 to 75 em; channery to gravelly, sandy loam to 

sandy clay loam; moist color 7 .5YR 5/6 (strong 

brown) to 5YR 4/6 (yellowish red); moderate to 

strong, fine to medium, subangular blocky structure; 

friable, sticky, plastic consistence; abundant thick 

clay films. 

Bt3-75 to 95 em; channery to gravelly sandy loam; moist 

color 7 .5YR 6/6 (reddish yellow) to 7 .5YR 5/8 

(strong brown); weak to moderate, fine to medium, 

subangular blocky structure; friable, slightly sticky to 

sticky, slightly plastic to plastic consistence; abundant thin to thick clay films. 
Table 5. Textural analysis of selected soils 

[In weight percent; clay fraction determined by X-ray particle-size analysis; sand and silt fractions determined by both wet and dry sieve analysis] 

Sample number/location 

Boyertown biotite gneiss 

G-6B(B1) ........................................ . 

G-6B(B21t) ...................................... . 

G-6B(B22t) ...................................... . 

G-6B(B23t) ...................................... . 

G-6B(B3) ........................................ . 

Boyertown quartz-feldspar gneiss 

G-8D(Ap) ........................................ . 

G-8D(Bt) ........................................ . 

G-8D(75) ........................................ . 

G-8DC .......................................... . 

Easton quartz-feldspar gneiss 

CH-9B(B1) ...................................... . 

CH-9B(B21t) ..................................... . 

CH-9B(B22t) ..................................... . 

CH-9B(B3) ...................................... . 

CH-9B(C1) ...................................... . 

CH-9B(C2) ...................................... . 

CH-9B(C3) ...................................... . 

BC-95 to 140 em; channery to gravelly sandy loam; moist 

color 7 .5YR 6/6 (reddish yellow); weak to moderate, 

fine to medium, subangular blocky structure; very 

friable, slightly sticky to nonsticky, slightly plastic to 

nonplastic; many thin clay films. 

C-140 to 180 + em; channery to gravelly, loamy sand to 

sandy loam; moist color 7 .5YR 5/7 (strong brown); 

weak, fine, subangular blocky to weak platy; very 

friable, nonsticky, nonplastic consistence. 

Particle-size analyses of the less-than-2-mm fraction 

have been completed on three representative soils, one from 

each major rock type. The sand and silt fractions were 

determined by both wet and dry sieve analysis; the clay 

fraction was determined by use of an X-ray particle-size 

analyzer (table 5). The analyses allow the soil texture to be 

classified, as shown on figure 38. All the soils tested from 

Boyertown and Easton fall into the range of loam to loamy 

sand. Clay contents range from 4 to 14 weight percent, with 

the highest amounts in the B horizons. 

The Boyertown biotite and hornblende gneisses produce the finest textured soils of those sampled. They 

weather to fine sand, silt, and clay; small, angular rock 

fragments occur mainly at depth. These soils are also the 

thickest and have more recognizable horizons, but these 

observations may be biased by the better exposures available for the biotite gneiss (natural cuts and pits instead of 

auger holes). The Boyertown quartz-feldspar gneiss weathers to coarse sand and larger, angular, platy rock fragments 

that are present throughout the profile (although more 

concentrated at depth). The Easton quartz-feldspar gneiss 

and pegmatite weather by granular disintegration to coarse 

Clay Silt Sand Soil texture 

4.0 28.5 67.5 sandy loam. 

12.2 37.0 50.8 loam. 

13.3 33.8 52.9 sandy loam. 

12.8 31.4 55.9 sandy loam. 

9.5 27.7 62.7 sandy loam. 

5.3 35.5 59.1 sandy loam. 

4.2 42.1 53.8 sandy loam. 

12.7 29.2 58.1 sandy loam. 

9.0 27.3 63.7 sandy loam. 

8.8 21.8 69.4 sandy loam. 

8.0 27.0 65.0 sandy loam. 

14.0 24.5 61.5 sandy loam. 

6.1 10.8 83.1 loamy sand. 

4.3 10.6 85.1 loamy sand. 

14.1 28.1 57.8 sandy loam. 

5.2 19.3 75.6 loamy sand. 

sand and small, equidimensional rock fragments (present 

mainly in the lower horizons). 

The Easton soils are generally more permeable than 

the Boyertown soils because the Easton soils are sandier. 

Soils on the Boyertown mylonitic gneiss are also relatively 

permeable because the bedrock is highly fractured and the 

soil is coarse overall. The finer textured soils on the biotite 

gneiss are slightly less permeable. All these soils, however, 

are well-graded (poorly sorted), gravelly, sandy loams or 

loamy sands, the permeabilities of which probably vary no 

more than 1 order of magnitude (fig. 36). 

RADON EMANATION OF SOILS 

As a check on in situ soil-gas measurements, an 

experiment to measure the radon emanation of soil samples 

was conducted. The samples collected in the field represent 

a bulk sample of the finer (generally the less-than-1-cm) 

fraction of the soil (although larger fragments were 

excluded from the sample, these would contribute 

proportionally less radon than the finer fraction because 

these larger fragments have smaller surface area to volume 

ratios). For the emanation experiment, a sample of about 

100 g (grams) of soil was split from the bulk sample by use 

of a coarse sample splitter; a second sample of about 250 g 

was sent to an outside laboratory for analysis of uranium 

and radium content. Because the initial sampling and 

subsequent splitting disaggregated the soil peds, the 

experiment does not represent field conditions. It does, 

however, give an indication of radon availability as related 

to soil texture (particle sizes). 

Soils in Boyertown and Easton, Pennsylvania 57 
clay 

clay 

• B horizons Boyertown biotite gneiss 

6 C horizons] 

• B horizons Easton quartz-feldspar ° C horizons] gneiss B horizons Boyertown quartz-feldspar 

gneiss 

clay loam 

sandy clay 

loam 

loams 

• 6 silt loam • • 

• • c~ 

75% 50% 25% silt 

Figure 38. The distribution of soil textures for B and C horizons from selected soils (SCS classification system). 

The soil samples were weighed, air dried in the lab 

for 24 to 36 hours, and weighed again. The dried soil 

samples were placed in 250-mL (milliliter) Erlenmeyer 

flasks and sealed with rubber stoppers fitted with septa. The 

volume of each stoppered flask was estimated by comparing 

the level of the stopper in the flask with an identical flask 

whose volume had been measured and marked. The volume 

of the soil was calculated from the weight of the dry soil by 

assuming a specific gravity of 2.65 for the mineral solids. It 

was assumed in this calculation that all the voids in the soil 

were filled with air and that all the voids were connected to 

the air in the flask (and could therefore contribute radon to 

the air in the flask). The samples were allowed to sit for at 

least 28 days so that the radon and radon daughters in each 

flask could come to equilibrium with the radium in the soil. 

The flask was then injected with 50 cm3 (cubic 

centimeters of room air, which was mixed by pumping the 

syringe 5 to 10 times. A 50-cm3 sample was extracted from 

the flask and immediately injected into the detector. The 

sample was measured for 5 minutes and recorded as the raw 

58 Field Studies of Radon in Rocks, Soils, and Water 

count, from which the background count was subtracted. 

Total and specific activities calculated from these values are 

shown in table 6, along with laboratory data for uranium 

and radium contents. 

Possible sources of error in the experiment include ( 1) 

leakage from the flask through the septa or around the 

rubber stoppers and (2) inaccurate estimates of flask 

volume, air volume, and soil volume. When measurements 

were repeated after another 30 days, 75 percent of the 

samples produced values within 20 percent of the first 

measurement. 

DISCUSSION 

Gundersen and others (1988) noted a strong 

correlation between soil-gas radon, indoor radon, and the 

concentration of uranium in the underlying bedrock. In the 

Boyertown area, radon activities were highest in the mylonite zone and lowest over the hornblende gneiss. In the 

Easton area, even higher radon activities were found in the 
Table 6. Lab data for uranium (U), radium (Ra), and radon (Rn) for Pennsylvania soils 

[G prefix, Gablesville-Boyertown soil; Ch prefix, Chestnut Hill-Easton soil; em, centimeters; ppm, parts per million; pCi/g, picocuries per gram; pCi/L, 

picocuries per liter;%, percent; chem U, chemically determined uranium; eU, equivalent uranium; eTh, equivalent thorium; K%, weight percent potassium; 

-,no data] 

Soil Depth Chern U u eU eTh 

sample (em) (ppm) (pCi/g} (ppm) (ppm) 

CH-2(8) 8 210 70.1 120 210 

CH-2(60) 60 230 76.8 130 

CH-3B(40) 40 35 11.7 30 

CH-3B(75) 75 26 8.7 27 

CH-3B(180) 180 20 6.7 22 

CH-7(20) 20 31 10.4 28 

CH-7(35) 35 32 10.7 30 

CH-7(50) 50 30 10.0 27 

CH-7(65) 65 25 8.4 24 

CH-7(85) 85 27 9.0 25 

CH-9A(Ap) 10 44 14.7 47 

CH-9A(B2lt) 30 39 13.0 35 

CH-9A(B22t) 50 40 13.4 45 

CH-9B(B1) 8 22 7.3 21 

CH-9B(B2lt) 25 29 9.7 31 

CH-9B(B22t) 40 19 6.3 22 

CH-9B(B3) 55 19 6.3 17 

CH-9B(C1) 68 16 5.3 16 

CH-9B(C2) 78 25 8.4 34 

CH-9B(C3) 88 57 19.0 53 

CH-10A(B3) 33 48 16.0 52 

CH-10A(C) 45 46 15.4 54 

CH-10C(20) 20 60 20.0 61 

CH-11 5 18 6.0 29 

G-4B(Ap) 14 6 2.0 5 

G-4B(B21t) 33 9 3.0 8 

G-4B(B22t) 50 12 4.0 5 

G-4B(B3) 75 13 4.3 10 

G-6B(A) 8 9 3.0 8 

G-68(B1) 20 9 3.0 9 

G-6B(B21t) 34 7 2.3 6 

G-6B(B22t) 56 5 1.7 3 

G-6B(B23t) 88 5 1.7 4 

G-6B(B3) 125 3 1.0 2 

G-8D(Ap) 24 12 4.0 11 

G-8D(Bt) 43 10 3.3 10 

G-80(75) 75 25 8.4 26 

G-8D(C) 80 16 5.3 18 

G-8D(Cr) 95 13 4.3 12 

G-9A(B1) 33 1 .3 2 

G-9A(B22t) 85 2 .7 2 

G-9A(B32) 165 2 .7 5 

G-9A(C) 250 10 3.3 9 

G-10(B) 5 35 11.7 42 

quartz-feldspar gneiss. The results from the radon emanation experiment and laboratory analysis support these general conclusions. 

Figure 39 shows the relation between uranium and 

radium. Except for the outlier values, uranium and radium 

340 

44 

22 

45 

28 

39 

19 

12 

15 

75 

60 

64 

23 

20 

17 

36 

22 

34 

66 

41 

19 

52 

31 

20 

21 

19 

19 

22 

27 

12 

10 

4 

7 

56 

57 

81 

77 

39 

5 

9 

2 

2 

89 

K Ra-226 Ra-228 Total Specific In situ 

% (pCi/g} (pCi!g) activity activity soil Rn 

(pCi/L) (pCi/g} (pCi/L) 

2.3 40.0 23.0 23,378 205 

5.7 43.0 37.0 31,823 287 

4.7 10.0 4.8 3,228 35 

4.0 9.1 2.4 2,838 31 8,000 

4.0 7.4 5.0 2,569 29 

3.1 9.3 3.0 5,471 49 

3.5 9.9 4.3 5,446 48 

2.2 8.9 2.1 4,825 47 

1.3 8.0 1.4 5,336 49 

1.3 8.4 1.7 9,165 87 

4.2 16.0 8.3 2,355 25 

4.1 12.0 6.6 5,193 54 

3.6 15.0 7.0 4,162 44 22,750 

5.0 6.9 2.5 5,231 48 

4.7 10.0 2.2 3,639 35 

4.6 7.3 1.9 4,890 46 

4.5 5.5 4.0 3,629 33 

5.3 5.4 2.4 2,539 23 

3.5 11.0 3.7 5,813 58 

4.2 18.0 7.2 8,194 78 

5.7 17.0 4.5 6,702 68 

5.9 18.0 2.1 5,730 57 11,000 

4.5 20.0 5.7 9,768 103 12,000 

1.4 9.8 3.4 2,009 22 8,500 

3.9 1.8 2.2 1,486 15 

4.5 2.6 2.3 1,878 19 

4.6 1.8 2.1 2,004 19 

4.7 3.2 2.1 2,912 27 2,400 

4.1 2.7 2.4 1,331 14 

3.9 3.1 3.0 157 2 

2.8 2.0 1.3 847 9 

1.9 .9 1.1 639 7 

1.3 1.5 .5 836 10 

.7 .8 .8 598 7 500 

4.7 3.8 6.2 2,162 24 

4.7 3.4 6.3 2,073 22 

5.2 8.6 8.9 4,516 46 5,000 

5.5 6.0 8.5 1,080 11 

5.4 3.9 4.3 3,088 28 

1.2 .8 .6 250 3 

1.4 .6 1.0 373 4 

3.5 1.6 .2 307 3 

2.9 3.1 .3 2,421 29 1,250 

5.4 14.0 9.8 7,479 '78 7,250 

in the soils are near secular equilibrium, as suggested by the 

high degree of correlation shown by the regression line on 

figure 39. This correlation indicates that no geochemical 

enrichment or depletion of uranium and radium has 

occurred in these soils. The two outlier values come from a 

Soils in Boyertown and Easton, Pennsylvania 59 
50 

.-. • 

C) 40 • :::: 

0 

a. 

......... 30 

co 

N 

N 

I 

E 20 

:l 

·-"'C 

as 

a: 10 m Boyertown soils 

• Easton soils 

0 

0 10 20 30 40 50 60 70 80 

Uranium (pCi/g) 

Figure 39. The relationship between uranium and radium for soils from Boyertown and Easton, Pa. The regression line for this set of data, excluding the 

anomalous outliers, shows that uranium and radium are in or near secular 

equilibrium. If, the correlation coefficient, is 0.953. pCi/g, picocuries per gram. 

25 

.-. 

C) 

20- • :::: 

0 

a. • . ......... 

co 15- • N m 

N . I 

E 10- •• :l 

·- m 

"'C . as 

a: 5- a Boyertown soi Is 

a a . • Easton soils 

m 

0 . I I . I I 

0 5,000 10,000 15,000 20,000 25,000 

In situ soil radon (pCi/L) 

Figure 40. The relationship between radium and in situ radon activity measured at 75 

em in depth in selected soils. pCi/g, picocuries per gram. 

60 Field Studies of Radon in Rocks, Soils, and Water 
50~------~~----------------------------------------~ 

Ideal emanation 

El 

40 El 

......... 

C) 

........ 

·-0 

S: 30 

co 

C\1 

C\1 I 

E 

::s 20 

·- a El 

-c El 

as a 

a: 

10 

a m Boyertown soils 

• Easton soils 

0~--------~--------~--------P---------------------------~ 

0 100 200 300 

Radon (pCi/g) 

Figure 41. The relationship between radium and radon, as measured from soil emanation experiments. The ideal 

emanation line assumes that all radon produced is available to the soil air. If, the correlation coefficient, is 0.863. pCi/g, 

picocuries per gram. 

site that had been scraped down to very permeable weathered bedrock; apparently some of the radium has been 

leached from this site. Note that the soils from Easton 

generally have more uranium and radium than those from 

Boyertown. 

Figure 40 shows a positive correlation between 

radium concentrations and in situ radon activity measured at 

75 em in depth in the soils. The overall positive correlation 

reflects the fact that only the soils are producing radon and 

that transient radon from other sources is not a factor. The 

anomalous point can be accounted for readily by higher 

permeability, probably related to the extensive joint system 

present in the Easton rocks. Figure 41 shows the relationship between radium concentrations and radon as measured 

in the emanation experiment. Although the soils differ 

texturally, the emanation of the dry soils was similar. 

Again, the values were higher for Easton than for Boyertown. These results indicate that, in saprolitic metamorphic 

terrains exposed below the glacial limit, radon in soil gas 

directly reflects the uranium content of the rocks. Permeability does not differ by more than an order of magnitude, 

so emanation experiments, such as the one discussed here, 

can be used to measure radon production of a soil in lieu of 

field measurements of radon. These measurements of radon 

in soil, both in situ and laboratory, can be compared 

favorably to the indoor radon values and thus used predictively. Figure 42 shows radon in soil gas and total activity 

of radon measured in the emanation experiment plotted 

against indoor radon for seven of the home sites. The 

anomalous data point at 22,750 pCi/L should theoretically 

have an indoor radon value much higher than that measured. Here, housing construction has probably played an 

important role. 

SUMMARY AND CONCLUSIONS 

The most significant overall controlling factor of the 

availability of radon is the uranium and radium content of 

Soils in Boyertown and Easton, Pennsylvania 61 
25,000 . 

• • In situ soil radon (pCi/L) ,....... . ..J 

::::: 2~000 0 - m Lab radon total (pCi/L) 

Q. 

.......... 

c 

0 15po0 .. "0 

ftS 

... • ·- 10,000 0 - CJ) • liiJ 

El 

5,000 - I . m 

:II 

•• 

0 . I . 0 1,000 

Indoor radon (pCi/L) 

Figure 42. Radon in soil and total activity versus indoor radon. pCi/L, picocuries 

per liter. 

the bedrock and soil materials. Radon migration is 

controlled by many factors but mainly by permeability. In 

this study, the permeabilities of the subsurface materials 

appear to be more than sufficient to allow radon to migrate 

freely. The soil environment into which a house is built is 

highly variable and therefore difficult to characterize. As 

stated previously, many of the in situ tests for radon in soil 

gas are drawn from the B and C horizons, and differences 

attributed to inherent differences in soils between areas may 

in some cases be due to differences between horizons. This 

observation could account for the variability seen within 

geologic units and some of the variability between geologic 

units. However, the geology and geochemistry of the soils 

generally provide a stronger overprint than the difference 

between soil horizons within rock units, so the prediction of 

ranges of soil-gas and indoor radon for a particular geologic 

unit is possible (similar results were found by Schumann 

and Owen, 1988). Distinctions can be made only where 

magnitude differences in geochemistry exist. For example, 

in Boyertown, the difference in radon concentrations, both 

indoors and in soils, is striking between the hornblende 

gneiss and the mylonite. The two rock types within the 

QFB, however, are not statistically distinguishable. In 

Easton, the difference between the highest readings in the 

biotite gneiss and the quartz-feldspar gneiss is an order of 

magnitude~ however, the sillimanite gneiss and the marble 

are statistically indistinguishable because of the geological 

variability within each unit. Careful examination of the 

62 Field Studies of Radon in Rocks, Soils, and Water 

physical and chemical properties of the soil must be made in 

order for values of radon in soil gas to be used effectively. 

REFERENCES CITED 

Birkeland, P.W., 1984, Soils and geomorphology: New York, 

Oxford University Press, 372 p. 

Drake, A.A., Jr., 1969, Geology of the Easton quadrangle, New 

Jersey-Pennsylvania: U.S. Geological Survey Geologic 

Quadrangle Map GQ-594, 1:24,000. 

Environmental Protection Agency, 1986, A citizens guide to 

radon-What it is and what to do about it: OPA-86-004, 

U.S. Government Printing Office, Washington D.C., 12 p. 

Gundersen, L.C.S., Reimer, G.M., and Agard, S.S., 1988, The 

correlation between geology, radon in soil gas, and indoor 

radon in the Reading Prong, in Marikos, M., ed., 

Proceedings of the GEORAD Conference, Geological Causes 

of Radionuclide Anomalies: Missouri Department of Natural 

Resources Special Publication No. 4, p. 99-111. 

Nazaroff, W.W., Moed, B.A., and Sextro, R.G., 1988, Soil as a 

source of indoor radon-Generation, migration, and entry, in 

Nazaroff, W.W., and Nero, A.V., Jr., eds., Radon and its 

decay products in indoor air: New York, John Wiley and 

Sons, Inc., p. 57-112. 

Schumann, R.R., and Owen, D.E., 1988, Relationships between 

geology, equivalent uranium concentration, and radon in soil 

gas, Fairfax County, Virginia: U.S. Geological Survey OpenFile Report 88-18, 27 p. 
Smith, R.C., II, Reilly, M.A., Rose, A.W., Barnes, J.H., and 

Berkheiser, S. W., Jr, 1987, Radon: A profound case: 

Pennsylvania Geology, v. 18, p. 1-7. 

Soil Conservation Service, 1970, Soil survey, Berks County, 

Pennsylvania: 125 p. 

---1974, Soil survey of Northampton County, Pennsylvania: 

120 p. 

Soils in Boyertown and Easton, Pennsylvania 63 

RADON IN SOIL GAS AND GAMMA-RAY ACTIVITY OF ROCKS AND SOILS AT THE 

MULLIGAN QUARRY, CLINTON, NEW JERSEY 

Mitchell E. Henry,1 Margret E. Kaeding/ and Donald Monteverde2 

Abstract 

Total-count gamma-ray data, gamma-ray spectrometer data, and soil-gas radon measurements were made at 

the Mulligan Quarry, Clinton, N.J. Although the entire 

area shows relatively high values of radioactivity, some 

areas within the quarry show radioactivity levels that are 

greater than twice background with all three measuring 

techniques used. Radon in soil-gas measurements generally shows high values in locations where gamma-ray 

activity is high, but this is not always the case. One area 

shows a high radon soil-gas value that corresponds to a 

relatively low equivalent uranium value, and another area 

shows a high equivalent uranium value that corresponds 

to a relatively low radon value. 

High gamma activity and high radon in soil-gas 

concentrations appear to be related to mineralization that 

occurs in a shear zone at the southern end of the quarry 

and may be related to fracture-filling material throughout 

the entire quarry. Soil development on top of the quarry 

prevents direct tracing of the fractures seen on the working face and may broaden any radon and (or) gamma-ray 

highs associated with these concealed fractures. 

INTRODUCTION 

Recognition of the health hazards that may result 

from inhalation of radon or its daughter products has 

prompted many recent studies of factors related to the 

concentration of radon inside homes and other buildings. 

The Environmental Protection Agency (EPA) has established 4 pCi/L (picocuries per liter) as the maximum 

acceptable level for indoor radon (EPA, 1986). 

Details of the formation of radon from the decay of 

uranium and the health hazards associated with breathing it 

and its particulate decay products may be found elsewhere 

in this volume and are not repeated here. It is sufficient, for 

the purpose of this paper, to state that radon-222 is a 

naturally occurring, radioactive, noble gas formed in the 

uranium-238-radium-226 decay series and that inhalation of 

radon-222 may cause thousands of deaths from lung cancer 

each year (EPA, 1986). 

Several areas in the United States are known where 

the radon concentration in homes is many times this 

maximum level. One such area is in Clinton, N.J. 

Mulligan Quarry in Clinton, N.J., offers a unique 

opportunity to study radon concentrations in both soil and 

bedrock in a region where private homes have elevated 

1

U.S. Geological Survey. 2

New Jersey Geological Survey, Newark, N.J. 

levels of radon. Located just east of the homes, the inactive 

quarry has a face of exposed rock, and at the upper level of 

the quarry the same type of soil exists as is found in the 

housing development (Patrick, 1920). 

The purpose of this study was to investigate the 

distribution of radioactive material in the rock and soil and 

of radon in the soil gas in this area. Information from this 

study should add to the general knowledge of indoor radon 

problems and their relation to geology. These data should 

have application in the evaluation of future building sites in 

similar areas or in the formulation of predictive models to 

identify potential problem areas. 

GEOLOGIC SETTING 

The Reading Prong province lies between the Valley 

and Ridge and the Piedmont provinces (fig. 43). Ridges of 

Middle Proterozoic mixed gneisses and granitoid bodies 

separated by intermontane belts of Cambrian and Ordovician sedimentary rocks compose the Reading Prong province of New Jersey (Drake, 1970). 

Cambrian and Ordovician carbonates of the Kittatinny Supergroup contain a basal arkose unit that unconformably overlies the Middle Proterozoic rocks. The arkose 

grades upward into a sequence of platform carbonates 

containing predominantly dolomite with lesser amounts of 

limestone and chert. Dolomite of the upper part of the 

Kittatinny Supergroup was the rock worked at the quarry. 

Here the dolomite is thin to medium bedded, fine to 

medium crystalline, with minor discontinous quartz sand 

lenses, bedded chert, and black dolomitic shale. 

Stratigraphically and structurally above these carbonates is a Middle Ordovician sequence that contains coarse 

granular sandstone, black, red, and green shales, and minor 

interbedded limestone (Markewicz, 1967). This sequence 

has been described as both autochthonous flysch deposits 

(Kummel, 1940; Markewicz, 1967) and far-traveled Jutland 

klippe related to the Taconic deformational period (Drake, 

1969; Rogers, 1971; Zen, 1972; Perissoratis and others, 

1979). 

Unconformably overlying all older rocks is the Newark Supergroup of Late Triassic and Early Jurassic age (Van 

Houten, 1969). Locally, only the Passaic Formation of Late 

Triassic age is present. This formation consists of fanglomerate and red shale that blanketed the entire study area but 

were eroded to their present location south of Mulligan 

Quarry (fig. 43). 

Three major deformation periods juxtaposed the geologic units into their present positions. Generally, the 

Radon in Soil Gas and Gamma-Ray Activity, Mulligan Quarry, Clinton, New Jersey 65 
0 Mi 

I I I I : I I I 

0 Km. 

Explanation 

~~~;~~1 Glacial Cover ~ Mulligan Quarry 

Upper Triassic Fanglomerate and Shale 

Middle Ordovician Sandstones and Shales 

of the Jutland Klippe 

Cambrian and Ordovician Dolomites and Limestones 

Proterozoic Igneous and Metamorphic Rocks 

,- , ~~ 

__, Contacts _ _, Faults A-. Thrust faults 

Figure 43. location of study area, Mulligan Quarry, Clinton, N.j. 

Proterozoic and Paleozoic units were folded and thrust 

faulted during the Taconic and Alleghenian orogenies. In 

the study area, the thrusts and beds generally strike northwest and dip to the southwest. Regionally, northeast to 

east-northeast thrust faults occur, which separate the Proterozoic and Paleozoic rocks. 

In the Mesozoic rifting, initiation of the breakup of 

Gondwanaland reactivated some east-northeast-striking 

regional thrust faults as listric normal faults (Ratcliffe, 

1980; Ratcliffe and others, 1986). Associated with this 

extensional period, east-west-striking, high-angle normal 

and reverse faults formed, further complicating the structure. Mesozoic rocks strike east-northeast and dip moderately northwest. Structurally, all three deformational periods affected the rocks of Mulligan Quarry, but high-angle 

normal and reverse faults predominate. 

GENERAL URANIUM DISTRIBUTION 

Uranium concentrations are of primary concern for 

this study because it is this element that generally deter66 Field Studies of Radon in Rocks, Soils, and Water 

mines the maximum amount of radon-222 that can be 

produced from a given material. The average crustal abundances of uranium and thorium in continental sialic rocks 

are 3 and 10 ppm (parts per million), respectively (Polanski, 

1965). Uranium occurs naturally in a variety of minerals 

and rock types. It tends to occur in those igneous rocks that 

are richest in silica and alkaline components. A primary ore 

of uranium is pitchblend, and it is often concentrated in 

minerals such as monazite, zircon, and apatite (Polanski, 

1965). Uranium also occurs in a wide variety of secondary 

minerals such as carnotite, autunite, tyuyamunite, and 

uranophane. Areas that contain uranium-bearing rocks or 

minerals in the shallow subsurface, or are covered by 

natural soils derived from these materials, have the potential 

to be radon problem areas. 

Carbonate rocks, particularly limestone and dolomite, normally contain low concentrations of uranium. 

Very pure calcium carbonate minerals normally contain 

about 1 ppm uranium; however, some carbonate rocks may 

contain greater than 10 ppm uranium that is associated with 
noncarbonate (heavy-metal resistates, sedimentary or 

marine apatite, fluorite, or some types of organic matter) 

constituents (Bell, 1963). 

Carbonate rocks exposed at the Mulligan Quarry, 

near homes that have elevated indoor radon values, were 

studied by McKeown and Klemic (1953). These writers 

described a 15-ft-wide shear zone near the southern end of 

the quarry which, according to their report, consisted of a 

cemented limestone breccia. Within the major shear zone 

they noted a structurally younger, 2- to 3-ft-wide shear zone 

that consisted of crushed and fractured limestone. The shear 

zone displayed elevated radioactivity (no specific values 

were given) as far as it could be traced, but the radioactivity 

decreased to the southwest. They also reported analyses that 

showed uranium values from material presumably within 

the shear zone and from a black limestone about 500 ft north 

of the shear zone of 680 and 460 ppm, respectively. 

Uranium-bearing apatite was identified in this area by the 

authors. 

Bell (1963) also briefly discussed the Mulligan 

Quarry. He described the rock exposed at the quarry as 

dolomite, or at least of the same chemical composition as 

dolomite, of the Kittatinny Limestone, now named the 

Kittatinny Supergroup. He also noted the presence of an 

unidentified yellow powdery uranium mineral, apatite, and 

phosphatic rocks at the quarry. Bell reported data from two 

samples taken from unspecified locations at the quarry that 

show uranium concentrations of 6 to 20 ppm. 

Popper and Blauvelt ( 1980) determined that the 

radioactive minerals present at Mulligan Quarry were apatite and hydroxyapatite and that their distribution appeared 

to be controlled by bedding surfaces and fractures. C. Bell 

(unpub. data, 1987) also suggested that uranium mineralization is structurally controlled. 

METHODS OF STUDY 

Three methods were used to measure radioactivity 

from rock and soil and the concentration of radon from 

soil-gas samples. Each method is briefly described below. 

Total-count gamma-ray measurements were made 

with a Geometries Gamma Ray Scintillometer, Model 

GR101A. Data from this instrument are given in counts per 

second (CPS) and show relative variations in total gammaray intensity only. Total-count scintillometer data contain 

information from several radionuclides collected simultaneously and do not distinguish among the individual elements. Because of the reports in the literature (McKeown 

and Klemic, 1953; Bell, 1963) of the association between 

elevated radioactivity values and uranium concentration, we 

used the scintillometer to make a preliminary survey of the 

area. 

The gamma-ray spectrometer partitions counts, based 

upon gamma-ray energy, and allows one to determine the 

energy and the amounts of potassium-40, bismuth-214, and 

thallium-208 present at each location. The concentrations of 

the two latter nuclides are proportional, respectively, to the 

concentrations of uranium-238 and thorium-232 present if 

secular equilibrium is assumed. During each measurement, 

the instrument was placed on the ground and counts were 

collected for 300 seconds. The counts that were recorded 

from the three channels were converted to a percentage of 

potassium-40 and an equivalent parts per million value for 

uranium-238 (eU) and thorium-232 (eTh). 

Soil-gas samples were collected by driving a pencilsized hollow steel probe into the soil to a depth of about 75 

em (Reimer and Bowles, 1979) and withdrawing a 10 cm3 

(cubic centimeter) sample of the soil gas into a syringe for 

radon analysis. The soil gas was then injected into a 

portable scintillometer that measured the decay events of 

the sample resulting from radon-222. A minimum of 10 

minutes was allowed before analysis of each sample, to 

eliminate the contribution by other short-lived radon isotopes. The maximum time between collection and analysis 

of each sample was about 5 hours. Radon-222, with a 

half-life of about 3.8 days, would suffer a decay loss of less 

than 5 percent of the original number of atoms collected 

during this time. Radioactivity of these samples was measured for a period of 1 minute and is given in picocuries per 

liter (pCi/L). Two instruments were used for these measurements, one manufactured by Bonder Kleg, the other by 

EDA (EDA RDA-200). Duplicate samples measured on 

each instrument agreed to within 10 percent of one another. 

A small area near the southern end of the quarry 

between the creek and the base of the cliff was used to 

establish an arbitrary background level for the measuring 

techniques used. Background for the total-count scintillometer was determined to be about 60 CPS, background for the 

gamma-ray spectrometer was determined to be about 24 

ppm eU, and the background value used for radon in soil 

gas was 2,600 pCi/L. It is acknowledged that this entire 

area is high in terms of radioactivity and could be considered one large anomaly; however, in order to study the 

distribution of uranium in soil and rock, the distribution of 

radon in soil gas, the relation between the two, and their 

relation to the geology, we adopted the term "anomaly" to 

represent an area that was at least twice the background 

value for that particular variable. 

RESULTS AND DISCUSSION 

Gamma-Ray Scintillometer Survey 

The location of each traverse of this survey is shown 

in figure 44. Traverse 1 (stations 10 to 28) was made near 

the creek bank, traverse 2 (stations 29 to 49) was made near 

the base of the quarry face, and traverse 3 (stations 50 to 70) 

Radon in Soil Gas and Gamma-Ray Activity, Mulligan Quarry, Clinton, New Jersey 67 
~ 

\ 

\ 

\ 

58 

. 

-" 

; 59 <. • 

a> 

~ 60 

• 

z.s 

. 

29 

Figure 44. Locations of stations along traverses from a survey made with a gamma-ray scintillometer, Mulligan Quarry, 

Clinton, N.J. 

68 Field Studies of Radon in Rocks, Soils, and Water 
and traverse 4 (stations 71 to 95) were made on top of the 

quarry, which stands 15 m or more above the creek. 

Total-count gamma-ray scintillometer data collected 

on traverse 1 show values (mean value= 77 CPS) generally 

the same as background (background= 60 CPS) and show 

little variability (range = 40-110 CPS). This result may be 

related to relatively homogeneous alluvial deposits blanketing the bedrock near the creek bank. 

Traverse 2, made along the base of the quarry face, 

shows a greater range in gamma-ray intensity (25-180 CPS) 

but similar average of all measurements (mean value = 72 

CPS) as compared to traverse 1. Low gamma-ray readings 

here are probably related to the contribution of dolomite in 

the quarry face (which is generally not highly radioactive 

except where fractured) to the total signal. Zones of 

elevated gamma-ray intensities are associated with open 

fractures or what appear to be recemented breccia zones. 

Traverse 3 was made on top of the quarry. Gammaray intensity along this traverse shows the greatest range of 

the four traverses (40-350 CPS), with the highest value 

measured, and a mean value (131 CPS) of about twice the 

background value. 

Traverse 4 of the survey also was made on top of the 

quarry along the western property boundary of the Clinton 

Historical Museum. These gamma-ray measurements have 

a mean value of 148 CPS, greater than two times background, and a range in values of 50-250 CPS, intermediate 

between the ranges for traverses 2 and 3. 

Four areas of elevated gamma-ray intensities (greater 

than two times background) are shown in figure 45 The two 

areas at the southern end of the quarry (A and B) are near 

the large radioactive shear zone mentioned previously. 

Area C is located along the projected strike of two 

prominent fracture sets, neither of which shows elevated 

gamma-ray intensity at the quarry face. This area may be 

related to the non-uniform distribution of uranium along 

fractures projected into the quarry face. Area D is located 

near the north end of the quarry and lies along the projected 

trace of a prominent fracture set that displays elevated 

gamma-ray intensity at the quarry face. 

Gamma-Ray Spectrometer Survey 

Data were collected with a gamma-ray spectrometer 

along two traverses (5 and 6) on top of the quarry (fig. 46). 

Traverse 5 was made between traverses 3 and 4, and 

traverse 6 was made along traverse 4. 

The calculated uranium concentration (eU) along the 

two traverses is shown in figure 4 7. These values range 

from about 5 to over 70 ppm eU and have a mean value of 

about 28 ppm eU. If the same criterion for "anomalous 

values" is used with this data set as that used for the 

total-count gamma-ray data set (readings two times background), three such areas are identified in figure 47 (areas 

E, F, and G). All are located within the areas defined as 

anomalous by total gamma-ray scintillometer data but are 

smaller. 

Radon Soil-Gas Survey 

Results of the radon soil-gas measurements and the 

gamma-ray spectrometer data are listed in table 7 and are 

shown in figure 48. Radon values range from 300 to 20,700 

pCi/L and have a mean value of about 5,600 pCi/L. The 

background radon value was about 2,600 pCi/L. Areas 

where radon activities were greater than two times background are also shown in figure 48. Three of the four 

anomalous areas (areas H, I, and J) overlap the anomalous 

areas identified from gamma-ray spectrometer data (eU) 

and total-count gamma-ray data. 

A crude correlation between soil-gas radon values 

and equivalent uranium exists (fig. 49); however, some 

sample locations show high equivalent uranium values and 

low radon values. Also, some locations show low equivalent uranium values and high radon values. The lack of a 

better correlation between these two parameters may be due 

to variables that affect gamma-ray measurements, the particle size of the uranium-bearing minerals, or physical 

properties of the soil. 

Two possibilities can explain the lack of correlation 

between equivalent uranium and radon values measured 

near the surface. Thicker soil over a localized uranium 

source would result in lower equivalent uranium values 

caused by gamma-ray attenuation and could cause lower 

radon values because of the increased migration path 

length. More moisture in the soil results in lower equivalent 

uranium values and lower radon values because wetter soil 

attenuates gamma-rays and retards radon mobility. 

Data regarding soil thickness and moisture content 

were not collected, and effects from these variables cannot 

be determined. However, variability in gamma-ray data 

taken from exposed bedrock along the base of the quarry 

face indicates a non-uniform distribution of radioactive 

material in the host rock. This fact, plus the proximity of the 

gamma-ray and radon anomalies at the southern end of the 

quarry to the shear zone, suggests that the distribution of 

these anomalies is controlled, in large part, by the distribution of radioactive materials in the host rock. 

SUMMARY 

Results of this study show that generalizations resulting from averages of large classes of rock types (carbonates) 

can be misleading when details of specific locations are 

considered. With regard to radon, the evaluation of an area 

for future development does not appear to be a simple 

matter. These data show that significant variations of radon 

in soil gas can occur over relatively short distances and that 

Radon in Soil Gas and Gamma-Ray Activity, Mulligan Quarry, Clinton, New Jersey 69 
\ 

\ 

\ 

Explanation 

Scale 

0 15 meters 

• 60 

•so 

• 70 

• 50 

• 60 

• 40 

N 

•80 

• 80 

•60 ~ 

• 

40

• 100 \ 

• 70 

•80 

• 70 

• 70 

• 80 

Figure 45. Gamma-ray scintillometer data, Mulligan Quarry, Clinton, N.J. Numbers shown indicate total gamma-ray 

intensity at that locality in counts per second. Stippled areas (A-D) indicate areas that are at least twice background level. 

70 Field Studies of Radon in Rocks, Soils, and Water 
124 

125 

• 

\ 

129 . 

132 

\ 

• 

133 

• 

\~9 

\168 

~ 

134 

• 

135 

• 

136 

• 

\ .)>. 

167 ~ 

'& 

66~$ • 6\ 

\:165 

~. 

137 

• 

138 

• 

Explanation 

'\4 ~~3 

\ 

Sample locality 

Property line 

Scale 

0 15 meters 

\ 

141 

0 

""' 

142 

61 

• \ 

\160 

143 

144 

. 

~9 \158 

\-

. 

145 146 

. 147 . 

7 

152\ 

{56 I 

\ 153 '\5 ~;7 

Vs4 

Figure 46. Locations of stations along traverses from a survey made with a gamma-ray spectrometer and soil-gas 

measuring equipment, Mulligan Quarry, Clinton, N.j. 

Radon in Soil Gas and Gamma-Ray Activity, Mulligan Quarry, Clinton, New Jersey 71 
Table 7. Gamma-ray spectrometer data and calculated concentrations of potassium, uranium, and thorium, Mulligan 

Quarry, Clinton, N.j. 

[pCi!L, picocuries per liter; CPS, counts per second; %, percent; ppm, parts per million] 

Sample 

124 .......... . 

125 .......... . 

126 .......... . 

127 .......... . 

128 .......... . 

129 .......... . 

130 .......... . 

131 .......... . 

132 .......... . 

133 .......... . 

135 .......... . 

137 .......... . 

139 .......... . 

141 .......... . 

142 .......... . 

143 .......... . 

144 .......... . 

145 .......... . 

146 .......... . 

147 .......... . 

149 .......... . 

150 .......... . 

151 .......... . 

152 .......... . 

154 .......... . 

156 .......... . 

157 .......... . 

158 .......... . 

159 .......... . 

160 .......... . 

161 .......... . 

162 .......... . 

163 .......... . 

164 .......... . 

165 .......... . 

166 .......... . 

167 .......... . 

168 .......... . 

169 .......... . 

Radon 

(pCi/L} 

8,850 

4,200 

2,500 

1,800 

2,350 

1,550 

2,150 

2,300 

1,400 

2,500 

4,050 

5,100 

5,250 

16,850 

2,500 

2,250 

7,250 

5,300 

4,000 

2,200 

12,100 

850 

8,450 

8,800 

12,900 

4,100 

8,000 

1,750 

4,350 

8,500 

20,700 

6,900 

4,750 

900 

11,900 

350 

650 

1,700 

300 

Potassium 

(CPS) 

3,177 

2,727 

3,127 

4,101 

3,825 

6,273 

4,321 

3,201 

3,199 

4,066 

3,957 

2,613 

2,660 

5,563 

3,741 

3,520 

5,983 

3,091 

2,972 

1,807 

3,356 

2,676 

7,530 

4,387 

3,504 

3,019 

3,893 

2,912 

2,976 

4,888 

8,573 

7,198 

6,247 

7,506 

4,665 

3,227 

2,246 

3,370 

2,912 

Uranium 

(CPS) 

1,687 

902 

2,704 

3,315 

2,740 

5,246 

877 

1,011 

1,270 

3,104 

2,227 

1,525 

1,854 

4,194 

2,671 

2,531 

5,598 

2,270 

1,912 

1,228 

2,601 

1,767 

7,096 

3,849 

3,058 

2,566 

3,380 

2,568 

2,579 

4,555 

8,214 

7,127 

5,959 

7,092 

3,942 

2,264 

884 

717 

1,089 

they do not always occur in a predictable manner. A simple 

hand-held scintillometer might be used as a first-order 

survey tool if it is understood that excavation into the earth 

might expose problems not detected at the surface. Gammaray spectrometer data would serve to distinguish between 

72 Field Studies of Radon in Rocks, Soils, and Water 

Thorium 

(CPS) 

726 

336 

550 

698 

772 

1,298 

495 

442 

471 

921 

732 

537 

537 

1,104 

640 

684 

1,606 

815 

882 

559 

698 

675 

1,139 

809 

813 

922 

1,042 

862 

705 

1,196 

2,342 

2,189 

1,301 

1,449 

997 

739 

446 

344 

429 

Potassium 

(%) 

1.8 

2.1 

.7 

1.2 

1.4 

1.6 

4.0 

2.6 

2.3 

1.3 

2.2 

1.3 

1.0 

1.9 

1.4 

1.3 

.9 

1.1 

1.3 

.7 

1.1 

1.2 

1.1 

.9 

.7 

.7 

.8 

.6 

.6 

.7 

1.1 

.7 

.8 

1.1 

1.1 

1.3 

1.6 

3.1 

2.2 

Equivalent 

uranium 

(ppm) 

13.6 

7.6 

26.9 

32.8 

25.5 

50.5 

5.9 

7.9 

10.7 

28.5 

19.8 

13.2 

17.0 

39.8 

25.8 

23.8 

52.1 

19.6 

14.9 

9.5 

24.5 

14.9 

73.5 

38.2 

28.9 

22.2 

30.8 

22.7 

24.1 

43.3 

76.7 

65.2 

58.9 

70.9 

37.7 

20.2 

6.4 

5.3 

8.9 

Equivalent 

thorium 

(ppm) 

20.3 

9.0 

15.2 

19.5 

21.6 

36.9 

13.6 

12.1 

12.9 

26.0 

20.5 

14.8 

14.8 

31.3 

17.8 

19.1 

45.8 

22.9 

24.8 

15.4 

19.5 

18.8 

32.3 

22.7 

22.8 

26.0 

29.5 

24.2 

19.7 

33.9 

67.2 

62.8 

37.0 

41.3 

28.2 

20.7 

12.2 

9.2 

11.7 

areas of high uranium or high potassium concentrations. 

Soil-gas radon measurements are the most direct of the 

techniques used in this study to evaluate potential radon 

problems arising from construction of buildings in areas 

having elevated amounts of uranium in the soil or bedrock. 
\ 

\.6 \ 

\ • 25 

\a ' G \ 

\ 

. .,:·51 

• 11 

Explanation 

Sample locality 

Property line 

Scale 

0 15 meters 

E 

Figure 47. Equivalent uranium concentrations (eU) in parts per million, calculated from gamma-ray spectometer data, 

Mulligan Quarry, Clinton, N.j. Stippled areas (E-G) indicate areas that are at least twice background level. 

Radon in Soil Gas and Gamma-Ray Activity, Mulligan Quarry, Clinton, New Jersey 73 
\ 

\ 

K 

• 4200 

\• 2150 

\ 

"2300 

\ 

\ •1550 

•1400 

•2500 

Scale 

0 15 meters 

J 

'~ 16850 

H 

Figure 48. Radon-222 activity from soil-gas samples given in picocuries per liter, Mulligan Quarry, 

Clinton, N.j. Stippled areas (H-J) indicate areas that are at least twice background level. 

74 Field Studies of Radon in Rocks, Soils, and Water 
21-

20-

19-

18-

17- 0 16-

15-

0 14- 0 

~ 13- 0 

12-

~ 11-

10- C3 9- ..9-

c: 8-

0 7- 'tl 

ttl 6- a: 5-

4 - 3-

2-

1 -

o- I 

0 60 

Equivalent Uranium (ppm) 

Figure 49. Cross plot of soil-gas radon-222 activities versus 

equivalent uranium values, Mulligan Quarry, Clinton, N.j. 

ppm, parts per million; pCi/L, picocuries per liter. 

REFERENCES CITED 

Bell, K.G., 1963, Uranium in carbonate rocks: U.S. Geological 

Survey Professional Paper 474-A, p. Al-A29. 

Drake, A.A., Jr., 1969, Precambrian and Paleozoic geology of the 

Delaware Valley, New Jersey-Pennsylvania, in Subitzky, S., 

ed., Geology of selected areas in New Jersey and eastern 

Pennsylvania and guidebook excursions: New Brunswick, 

N.J., Rutgers University Press, p. 52-130. 

---1970, Structural geology of the Reading Prong, in Fisher, 

G.W., Pettijohn, F.J., and Reed, R.C., Jr., eds., Studies of 

Appalachin geology-Central and southern: lnterscience 

Publishers, p. 271-291. 

Environmental Protection Agency, 1986, A citizen's guide to 

radon: Environmental Protection Agency Preliminary Draft 

Report, 23 p. 

Kummel, H.K., 1940, The geology of New Jersey: Department of 

Conservation and Development, State of New Jersey, Geological Series, Bulletin 50, 203 p. 

Markewicz, F., 1967, Geology of the High Bridge quadrangle: 

New Jersey Geological Survey, unpublished report, 139 p. 

McKeown, F.A., and Klemic, H., 1953, Reconnaissance for 

radioactive materials in Northeastern United States during 

1952: U.S. Geological Survey Trace Element Investigations 

317-A, 68 p. 

Patrick, A.L., 1920, Soil survey of the Belvidere area, New 

Jersey: Report of the Department of Conservation and Development, State of New Jersey, Geological Series, Bulletin 20, 

72 p. 

Perissoratis, C., Brock, P.W.G., Brueckner, H.J., Drake, A.A., 

Jr., and Berry, W.B.N., 1979, Taconides of western New 

Jersey-New evidence from Jutland Klippe, summary: Geological Society of America Bulletin, v. 90, no. 1, p. 10-13. 

Polanski, A., 1965, Geochemistry of isotopes: The Scientific 

Publications Foreign Cooperation Center of the Central Institute for Scientific, Technical and Economic Information, 

Office of Technical Services, U.S. Department of Commerce, 473 p. 

Popper, G.H.P., and Blauvelt, R.P., 1980, Work plan, Newark 

quadrangle covering parts of Pennsylvania and New Jersey: 

Bendix Field Engineering Corporation (in conjunction with 

the National Uranium Resource Evaluation Program), 45 p. 

Ratcliffe, N.M., 1980, Brittle faults (Ramapo Fault) and phyllonitic ductile shear zones in the basement rocks of the Ramapo 

seismic zones, New York and New Jersey, and their relationship to current seismicity, in Manspeizer, W., ed., Field 

studies, New Jersey geology and guide to field trips (New 

York State Geological Association 52d Annual Meeting): 

New Brunswick, N.J., Rutgers University, p. 278-312. 

Ratcliffe, N.M., Burton, W.C., D'Angelo, R.M., and Constain, 

J .K., 1986, Low-angle extensional faulting, reactivated 

mylonites, and seismic reflection geometry of the Newark 

Basin margin in eastern Pennsylvania: Geology, v. 14, p. 

766-770. 

Reimer, G.M., and Bowles, C.G., 1979, Soil-gas helium concentrations in the vicinity of a uranium deposit, Red Desert, 

Wyoming: U.S. Geological Survey Open-File Report 

79-975, 9 p. 

Rogers, J., 1971, The Taconic orogeny: Geological Society of 

America Bulletin, v. 82, p. 1141-1178. 

Van Houten, F.B., 1969, Late Trassic Newark Group, north 

central New Jersey and adjacent Pennsylvania and New 

York, in Subitzky, S., ed., Geology of selected areas in New 

Jersey and eastern Pennsylvania and guidebook excursions: 

New Brunswick, N.J., Rutgers University Press, p. 314-347. 

Zen, E-an, 1972, Taconide zone and the Taconic orogeny in the 

western part of the northern Appalachian orogen: Geological 

Society of America Special Paper No. 135. 

Radon in Soil Gas and Gamma-Ray Activity, Mulligan Quarry, Clinton, New Jersey 75 

RADON IN SOIL GAS ALONG ACTIVE FAULTS IN CENTRAL CALIFORNIA 

Chi-Yu King, Calvin Walkingstick, and David Basler 

Abstract 

Radon concentration in subsurface soil gas was monitored by the Track-Etch method during the decade 1975 to 

1985 at 60 sites along a 380-kilometer segment of the San 

Andreas fault system between Santa Rosa and Cholame in 

central California. The recorded radon concentrations 

show large spatial differences not attributable to differences in uranium content of local soil. The radon data also 

show large temporal variations, part of which are seasonal 

in appearance. The nonseasonal components of the radon 

variations may be correlated with occurrences of larger 

local earthquakes. 

INTRODUCTION 

Radon content of soil gas was monitored from 1975 

to 1985 at a network of 60 stations along several active 

faults in central California in search of possible precursors 

to earthquakes. Some of the earlier results have been 

discussed by King (1978, 1980). In this section, we present 

the entire set of radon data and compare them with some 

local seismic and meteorological data but without detailed 

discussion on their correlation. This data set may be useful 

in helping to understand the variability of radon concentration in a near-surface environment, a problem pertinent to 

indoor radon pollution. 

MONITORING SITES 

The radon monitoring network consisted initially of 

20 stations along the Calaveras and the San Andreas faults 

between Hollister and San Benito (site 19, fig. 50). It was 

later expanded in stages to include 60 stations that covered 

several major traces of a 380-km (kilometer) segment of the 

San Andreas fault system between Santa Rosa and Cholame 

(site 30, fig. 50). The station location and installation dates 

are shown in table 8 and figure 50. A detailed description of 

the site conditions may be found in Gaman and King 

(1979). Stations were also installed in the Geysers geothermal area and in southern California; these data sets will be 

reported elsewhere. 

MONITORING TECHNIQUE 

Radon concentration was monitored by the TrackEtch method developed by the Terradex Corporation. A 

small chip of cellulose nitrate, which is sensitive to alpha 

radiation, was attached to the inside bottom of a plastic cup 

9 em (centimeters) high with a 7-cm aperture. The cup was 

put upside down at the bottom of a shallow hole about 10 

em in diameter and 70 em in depth to expose the chip to soil 

gas. The hole was supported by a capped plastic pipe about 

80 em long, which was also used to reduce the effect of 

rainfall, wind, and temperature variation on the radon 

measurement. After a period of a week to several weeks or 

longer, the cup was replaced by another, and the retrieved 

cup was sent to Terradex, where the chip was chemically 

etched and the alpha-particle tracks in the chip were counted 

under a microscope. The track density within an area of 

about 6 mm2 (square millimeters) was then used as a 

measure of the average concentration of radon isotopes in 

the soil gas during the period of exposure. 

The recorded radon time series at the 60 stations are 

shown in figure 51 in units of number of tracks per 100 

'fields of view' per week, each unit being equivalent to 2.7 

pCi/L (picocuries per liter). Longer exposure periods were 

used during latter years in order to cut cost. Three stations 

(Nos. 10, 11, and 31) changed locations, and only data 

recorded at the new locations are shown. Data gaps are 

caused by a variety of incidents such as vandalism. For a 

period of about 2 years beginning in mid-1982, chips of 

higher sensitivity (by a factor of 5) were used; the difference 

in sensitivity is corrected in the plotted time series. 

The radon data can be compared with earthquake data 

in various ways. Because earlier data appeared to show 

correlation with larger earthquakes (King, 1978, 1980), we 

show in figure 51 the occurrences of earthquakes of Richter 

magnitude 2:4.0 within 50 km of each station on the same 

time scale. 

To compare with meteorological data, we show in 

figure 52 the amounts of daily rainfall and maximum/minimum temperatures recorded at Gilroy (21 km northwest of 

Hollister), which is near the center of the radon-monitoring 

network. Most rainfall in the study area occurs in the winter 

months. 

As reported by King (1980), the long-term average 

radon concentrations do not appear to depend strongly on 

the amounts of uranium or its "emanating" part in the local 

soils, as determined by gamma-ray spectroscopy with soil 

samples collected from the bottom of some monitoring 

holes (fig. 53). 

DISCUSSION 

As shown in figure 53, the soil-gas radon concentrations recorded at different stations were greatly different, 

and the difference amounted to an order of magnitude for 

sites of equal uranium content in the local soil. This spatial 

variation suggests that radon generation and migration in 

Radon in Soil Gas Along Active Faults in Central California 77 
the ground are significantly affected by several other 

factors, such as permeability, porosity, water content, and 

topography. 

The radon concentrations recorded at many sites also 

show large temporal, especially seasonal, variations (fig. 

51). However, because the seasonal variations recorded at 

different sites are not always in phase with one another, it is 

suggested that variability of rain-water movement in the soil 

may be the main cause. Rain water may fill pores and 

reduce permeabiliy in a relatively thin layer at the surface 

above the measurement depth (0.7 meter) at some sites and 

thereby produce a cap that may increase radon content at the 

measurement level, or it may seep to a deeper-than-detector 

level and prevent radon generated below from reaching the 

detector at other sites (for example, site 46). Other meteorological parameters, such as barometric pressure and wind 

speed, probably have not significantly affected the radon 

data because of the integrated nature of our measurement 

over relatively long periods. 

Some temporal variations are not seasonal in nature. 

For example, the maximum radon values recorded at site 6 

occurred during winters of 1976-79 but during springs or 

summers subsequently. Because the episodic nonseasonal 

components of the temporal variations are commonly spatially coherent over long segments of the same fault but not 

necessarily along another fault nearby, it is suggested that 

they may be tectonic in nature. (For example, an episodic 

78 Field Studies of Radon in Rocks, Soils, and Water 

increase was recorded in the summer of 1978 at sites 1 and 

2 on the Calaveras fault, where the radon concentration was 

extremely low in the summers of 1975 and 1976. Contemporary increases were recorded at several other sites 

(36-40) farther north along the same fault but not at the 

nearby sites 4-7 on the San Andreas fault.) Larger earthquakes appear to have a tendency of occurring during 

episodes of higher radon concentrations at least at some 

sites. 

ACKNOWLEDGMENTS 

We thank W.A. Gaman and R. Husk for technical 

assistance and G.M. Reimer for helpful comments on the 

manuscript. 

REFERENCES CITED 

Gaman, W.A., and King, C.-Y., 1979, Catalog of soil-gas radon 

measurements in central California for May 1975 through 

December 1978: U.S.Geological Survey Open-File Report 

79-547, 143 p. 

King, C.-Y., 1978, Radon emanation on San Andreas fault: 

Nature, v. 271, p. 516-519. 

---1980, Episodic radon changes in subsurface soil gas along 

active faults and possible relation to earthquakes: Journal of 

Geophysical Research, v. 85, p. 3065-3078. 
Table 8. Soil-gas radon monitoring sites, central California 

Site Name latitude longitude Elevation Installation 

(oN) (oW) (in meters) date 

01 Bolsa Road, on Calaveras fault 36 53 121 25.4 70 517175 

02 Wright Road, on Calaveras fault 36 52 121 24.8 81 517175 

03 Nyland, on San Andreas fault 36 51 121 32.7 54 517175 

04 Artesian Well, on San Andreas fault 36 50 121 31.6 61 5/7/75 

05 San Juan Bautista, on San Andreas fault 36 50 121 31.2 65 517175 

06 St. Francis Retreat, 25 m northeast of San Andreas fault 36 49 121 29.9 131 517175 

07 Harris East, on San Andreas fault 36 46 121 25.8 320 517175 

08 Harris West, 300m southwest of San Andreas fault 36 46.6 121 26.0 274 517175 

09 Cienega Well, 70 m southwest of San Andreas fault 36 45.1 121 23.2 344 5/7/75 

10 Thompson Creek, a few meters southwest of San Andreas fault 36 42.1 121 19.1 244 1118/78 

11 Pescadero Creek, on San Andreas fault 36 41.4 121 18.1 232 1118/78 

12 Frank Lewis, near San Andreas fault 36 39.9 121 16.3 229 5/7/75 

13 Stone Canyon North, on San Andreas fault 36 38.2 121 14.3 247 517175 

14 Stone Canyon Hill, on San Andreas fault 36 38.1 121 14.1 287 5/7/75 

15 Willow Creek, on San Andreas fault 36 35.7 121 11.4 317 5/7/75 

16 Melendy Corral, on San Andreas fault 36 35.5 121 11.1 308 517175 

17 Melendy River, on San Andreas fault 36 35.3 121 10.9 311 5/7/75 

18 Melendy Ranch, on San Andreas fault 36 35.0 121 10.6 317 5/7/75 

19 San Benito, 30m southwest of San Andreas fault 36 30.6 121 05.9 476 517175 

20 Dry Lake, on San Andreas fault 36 29.5 121 04.7 486 517175 

21 Little Rabbit Valley, a few meters southwest of San Andreas fault 36 25.6 121 00.8 549 3/30/76 

22 Bitterwater Valley, on San Andreas fault 36 24.4 120 59.6 535 3/30/76 

23 Hwy. 198, Mustang Ridge, on San Andreas fault 36 11.6 120 46.2 771 3/30/76 

24 Parkfield Junction, 21 km northeast of San Andreas fault 36 04.9 120 28.6 363 3/30/76 

25 Little Cholame Creek, 1.6 km northwest of San Andreas fault 35 57.2 120 28.5 546 3/30/76 

26 Parkfield Bridge, on San Andreas fault 35 53.7 120 26.0 460 3/30/76 

27 Turkey Flat, on San Andreas fault 35 52.7 120 24.9 445 3/30/76 

28 Gold Hill, on San Andreas fault 35 49.4 120 21.0 381 3/30/76 

29 Water tank, on San Andreas fault 35 45.4 120 18.4 349 3/30/76 

30 Hwy. 46, 250m southwest of San Andreas fault 35 44.0 120 17.4 348 3/30/76. 

31 Soda Lake, on San Andreas fault 35 54.3 121 36.6 43 5/16/78 

32 Watsonville, on San Andreas fault 35 59.6 121 44.1 128 4/6/76 

33 Laurel, 180m northeast of San Andreas fault 37 06.3 121 54.0 567 416176 

34 Los Gatos, 400 m southwest of San Andreas fault 37 09.8 121 59.2 305 4/6/76 

35 San Jose, 1.9 km southwest of Calaveras fault 37 22.6 121 47.2 311 416176 

36 Coyote, 3 km southwest of Calaveras fault 37 14.1 121 40.9 253 4/6/76 

37 Anderson Lake, on Calaveras fault 37 09.1 121 34.9 213 4/6/76 

38 North of San Felipe Lake, on Calaveras fault 36 59.7 121 28.5 162 4/6/76 

39 Shore Road, on Calaveras fault 36 56.6 121 26.7 49 4/6/76 

40 Pacheco, 60 m southwest of Calaveras fault 36 55.6 121 26.3 53 4/6/76 

41 Spring Down Farm, on San Andreas fault 37 22.9 122 13.6 137 7/15/76 

42 Pulgas Water Temple, 250m northeast of San Andreas fault 37 29.0 122 18.9 98 10/19/76 

43 San Andreas, 240m southwest of San Andreas fault 37 34.6 122 24.5 114 10/19/76 

44 Daly City, 1 km southwest of San Andreas fault 37 40.9 122 29.5 146 7/15/76 

45 Richmond, on Hayward fault 37 59.4 122 22.3 6 12/15/76 

46 Holy Redeemer College, on Hayward fault 37 45.5 122 09.4 46 8/26/76 

47 Martinez, 3.6 km southwest of Concord fault 37 58.1 122 06.0 67 8/26/76 

48 Dublin, near Calaveras fault 37 41.2 121 55.7 127 919176 

49 Calaveras Reservoir, on Calaveras fault 37 30.2 121 49.9 280 10/19/76 

50 Fremont, on Hayward fault 37 32.2 121 57.4 18 919176 

51 Bolinas, on San Andreas fault 37 56.1 121 41.9 2 2/18/77' 6/8/77 

52 Mile 22, on San Andreas fault 37 59.3 122 44.8 108 3/2/77 

53 Pt. Reyes Ranger Station, on San Andreas fault 38 02.7 122 47.9 14 2/18/77 

54 Bodega Head, 1.1 km southwest of San Andreas fault 38 19.6 123 03.4 15 2/18/77 

55 Santa Rosa, 650 m northeast of Rodgers Creek-Healdsburg fault 38 28.2 122 41.0 107 2/18/77 

56 Jet. Crane Canyon and Grange Roads, near Rodgers Creek fault 38 22.5 122 38.3 222 4/13/77 

57 Willie Bird Turkey Farm, 300 m southwest of Rodgers Creek fault 38 14.2 122 30.7 88 4/13/77 

58 Sears Point, 200 m northeast of Rodgers Creek fault 38 10.6 122 27.0 12 2/22/77 

59 Cordelia, on Green Valley fault 38 12.2 122 09.2 34 3/2/77 

60 Bencia, on Green Valley fault 38 06.0 122 06.3 18 2/22/77 

Radon in Soil Gas Along Active Faults in Central California 79 
Son 

0 

123. 

55\ Santo Rosa 

.... ~6 

·~

58 a-Napa 

50 KM 

38' 

CALIFORNIA 

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the center of the radon-monitoring network. 

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Figure 53. Average radon concentrations recorded from 

1975 to 1978 at stations 1 to 30 versus (A) uranium content 

of local soil and (B) emanating part of the uranium content 

(after King, 1980). ppm, parts per million. 

Radon in Soil Gas Along Active Faults in Central California 143 

RADON EMANATION FROM URANIUM MILL TAILINGS 

Edward R. Landa 

Abstract 

Alkaline circuit and a mixture of acid and alkaline 

circuit uranium mill tailings sampled at an inactive millsite 

near Monticello, Utah, and tailings from an active, acidleach uranium mill were separated into particle-size fractions ranging from +10 mesh to -325 mesh by dry and wet 

separation techniques. The radium-226 contents and 

radon-222 emanation coefficients of these fractions were 

determined. Dry tailings show a high degree of aggregation that tends to mask the relationship of properties, 

such as radium content and radon-emanating power, to 

dispersed-particle size. Coarse-tailings fractions ( + 325 

mesh) had emanation coefficients that were from 25 to 45 

percent lower than those of their fine-fraction counterparts. Emanation coefficients measured for tailings 

derived from a salt-roast/carbonate-leach process suggest 

that such ore roasting does not lead to reductions in radon 

emanation in the tailings derived therefrom. 

Three ore samples of differing uranium mineralogies 

and rock types were leached with either sulfuric acid or 

sodium carbonate solutions under laboratory conditions 

to simulate acid or alkaline uranium milling practices. The 

radon emanation coefficients of the initial ore and of the 

tailings derived from them were compared. No consistent 

pattern enabling the prediction of radon emanation coefficients of tailings on the basis of ore type was evident. 

The similarities in the coefficients of the acid-leach tailings 

suggest that the lixiviant solution plays an important role 

in determining the form, and hence, the emanating power 

of the radium retained therein. 

INTRODUCTION 

Although greater than 90 percent of the uranium is 

generally extracted during the milling of uranium ores, most 

of the daughter product activity remains with the tailings 

(Moffett, 1976). Because of this, uranium mill tailings 

constitute a voluminous form of low-level radioactive 

waste. The quantity of these tailings in the United States is 

presently about 200 million tons (U.S. Department of 

Energy 1981 , 1986). Radon release to the atmosphere 

constitutes an important exposure pathway from these 

wastes, and studies have been undertaken to assess the roles 

of (1) particle size and (2) ore type and milling process on 

such release. 

RADIUM-226 CONTENTS AND RADON 

EMANATION COEFFICIENTS OF PARTICLE-SIZE 

FRACTIONS OF ALKALINE, ACID, AND MIXED 

URANIUM MILL TAILINGS 

For an unconsolidated earth material such as a soil, 

particle-size distribution can exert a strong influence on its 

geotechnical behavior and the relative susceptibility of its 

components to erosion by wind and water. Such relations 

also have been recognized in the management of uranium 

mill tailings (UMT). From the geotechnical perspective, 

"sand" and "slime" tailings have often been intentionally 

segregated prior to disposal by uranium mill operators to 

provide sand for tailings embankments (Merritt, 1971) and 

mine backfill (Markose and others, 1982) or to enable 

reprocessing of slimes at a later date for recovery of residual 

mineral values (Ford, Bacon and Davis Utah, Inc., 1978). 

From the geomorphological perspective, the preferential 

mobilization of fine particles by wind, raindrop impact, and 

flowing water is recognized as an important environmental 

transport phenomenon. As both operating practices at UMT 

disposal areas and natural forces tend to segregate tailings 

by particle size, it is important to understand how tailings' 

radiologic characteristics, such as the radium-226 e26Ra) 

content and radon-222 e22Rn) emanation coefficients, 1 

may vary as a function of particle size. A knowledge of how 

these properties vary with particle size can also aid in 

modeling environmental impacts (for example, establishing 

emission-source terms in radon-flux models) and in designing mitigation measures (for example, requisite cover thicknesses for radon-flux control on sand and slime areas). 

A longstanding truism of UMT management has been 

that the slimes (generally considered as the -200 mesh 

( <74 f.L) fraction) have elevated contents of uranium daughter products compared to the sands ( +200 mesh). However, 

studies by Guill (1978), summarized in the U.S. Nuclear 

Regulatory Commission's Final Generic Environmental 

Impact Statement on Uranium Milling (U.S. Nuclear Regulatory Commission, 1980) indicate that dry-sieved tailings 

may not show this pattern of increasing radionuclide content 

with decreasing particle size. The pattern observed by Guill 

is probably the result of aggregation of particles from either 

the cohesive properties of the slimes (Guill, 1978) or the 

cementing action of sulfate salts in acid-circuit UMT, 

carbonate salts in alkaline-circuit UMT, or a combination 

thereof in mixed or limed tailings. Methods of particle-size 

analysis that preserve such aggregates, and those that 

disrupt such aggregates, provide complementary 

approaches to evaluating particle-size relations in UMT. 

Dry-separation methods, including conventional sieving 

and air-elutriation techniques, enable one to examine 

mechanically stable aggregates that can persist under natural conditions and do not result in the loss of soluble 

constituents by leaching. Wet dispersion, followed by wet 

1

The fraction of the radon produced that escapes from the solid 

matrix and thereby has the potential to reach the unconfined atmosphere. 

Radon Emanation from Uranium Mill Tailings 145 
sieving, sedimentation, or elutriation, enables one to isolate 

the discrete particles of which UMT are composed. In the 

modeling of the environmental transport of tailings particles, wind transport may best be evaluated by use of 

dry-separation size distributions, while with waterborne 

transport, the wet-separation size distribution should be 

considered. 

The relation of the 226Ra content and radon emanation 

coefficient (REC) to UMT particle size has received relatively little systematic investigation. The purpose of this 

study was to examine these relations, by use of both dryand wet-separation techniques, in UMT derived from acid, 

alkaline, and mixed circuits. 

Materials 

Five uranium mill tailings samples were studied; four 

of these came from the Monticello, Utah, tailings site. 

Differences among these tailings reflect changes in milling 

practices and tailings disposal during the active life of that 

operation (1942-60). The following brief description of the 

Monticello operation is based largely on reports from the 

operating period, with extrapolation to the presently identified tailings area by the author. 

The Monticello mill, constructed in 1942 and operated through 1944, used a salt roast-sodium carbonate 

leaching process to extract vanadium from Colorado Plataeu 

ores (Anonymous, 1944; U.S. Atomic Energy Commission, 1963). Some uranium was produced as a by-product 

(Butler, 1951), probably by leaching the salt roast tailings 

with sulfuric acid to produce a uranium-rich "green sludge" 

(Colorado Metal Mining Fund Board, 1961; Merritt, 1971). 

After a 5-year inactive period, a largely rebuilt mill opened 

in 1949 and operated through 1955; a salt-roast carbonateleach circuit was used to recover uranium and vanadium 

(Butler, 1951; Merritt, 1971). The tailings from this period 

(1942-55) are designated the "carbonate" tailings at the site 

and by the acronym MCT in this report. In 1955, the salt 

roast and recovery of vanadium were abandoned and 

replaced by a direct carbonate-leach process for recovery of 

uranium only (Merritt, 1971). These mill tailings appear to 

be those called the "V 20 5" tailings at the Monticello site 

and are designated MVT in this report. 

Later in 1955, an acid-leach plant circuit (complementing the existing carbonate circuit) and new tailings 

pond were constructed (the "south" or "acid" tailings 

(MAT)). Despite the name, this pond apparently received 

both the alkaline- and acid-circuit tailings for a period of 

about a year (U.S. Atomic Energy Commission, 1963). 

Late in 1955, a new tailings pond (the "east" tailings 

(MET)) was built. Here, too, the tailings from the two 

circuits were combined, and additional lime was added to 

neutralize the waste stream (Whitman and Beverly, 1958). 

In 1958, the acid circuit was converted to a carbonate circuit, 

146 Field Studies of Radon in Rocks, Soils, and Water 

and discharge to the east tailings pond continued until the 

plant closed in 1960 (Merritt, 1971). During 1961-62, the 

900,000 tons of tailings in the four disposal areas were 

recontoured and covered with rock and soil (U.S. Atomic 

Energy Commission, 1963). 

In 1979, the U.S. Department of Energy did extensive drilling at the Monticello site and sampled each of the 

four tailings-disposal areas. Samples were dried at 110 oc 

and crushed with a cone and ring device set at -10 mesh, 

and then a composite sample from each tailings area was 

prepared (C. L. Bruner, Bendix Field Engineering Corp., 

personal commun. , 1981). Portions of these composite 

samples were obtained for use in this study through the 

courtesy of the U.S. Department of Energy and Bendix 

Field Engineering Corporation, Grand Junction, Colo. 

The fifth sample (CTl) was obtained from an active, 

acid-leach uranium mill in the Western United States. The 

tailings slurry was collected just prior to discharge to the 

pond, and the solids were collected by vacuum filtration in 

which Whatman no. 41 filter paper was used; the moist 

tailings were dried and crushed as described earlier. 

Methods 

For dry separations, 50-g (gram) aliquots of the bulk 

tailings samples were put through a nest of 20-cm (centimeter) in diameter stainless steel sieves that were mechanically shaken (500 excursions per minute, with intermittent 

tapping) for 30 minutes. The following size fractions were 

obtained (the numerical designations shown here are used in 

tables 9-14). 

Size Mesh1 Size limits 

fraction (in micrometers) 

0 ................... +10 >2,000 

1 ................... -10,+35 2,000->500 

2 ................... -35,+60 500->250 

3 ................... -60,+120 250->125 

4 ................... -120,+200 125->74 

5 ................... -200,+325 74->44 

6 ................... -325 <44 

1 U.S. Standard series sieve designation. 

Samples of dry fractions 0 through 5 were later 

dispersed in deionized water and wet sieved through a 325-

mesh screen to determine the size distribution (> 325 or 

<325 mesh) of the dispersed components of these dry 

fractions. 

For wet separation, 15-g aliquots of bulk tailings 

samples were shaken overnight ( 180 excursions per minute) 

in 100 mL (milliliters) of deionized water in order to disrupt 

aggregates. These slurries were decanted onto a 325-mesh 

sieve. An electric sieve vibrator was used, and the material 

on the screen was washed with a fine stream of deionized 

water (approximately 375 mL per aliquot). The coarse 
Table 9. Particle-size analysis (dry sieving) of uranium mill 

tailings 

[MAT, MCT, MET, and MVT are the Monticello, Utah, "acid," "carbonate," "east," and "vanadium" tailings, respectively. CT1 are tailings from 

an active acid-leach uranium mill. These designations are used in tables 

9-14] 

Tailings Dry-sieving size fraction (weight percent)1 

0 1 2 3 4 5 6 

MAT ....... 1.8 20.4 10.9 14.9 16.1 24.8 11.0 

MCT ....... 5.5 12.0 12.0 26.3 20.9 17.4 5.9 

MET ....... 7.7 27.5 12.3 13.6 11.9 17.8 9.2 

MVT ....... 2.1 18.4 12.0 21.1 15.8 21.6 9.0 

CT1 ........ 5.4 17.5 47.4 17.6 6.4 5.9 

1

Fractions 0 and 1 combined as the + 10 mesh quantity are 

negligible. 

material ( + 325 mesh) on the screen was oven dried at 30 

°C. The fine material ( -325 mesh) passing the screen was 

allowed to settle overnight. The supernatant was then 

siphoned off and the sediment concentrated by high speed 

(10,000 revolutions per minute) centrifugation. In the case 

of slurry samples that did not clarify on standing overnight 

(MCT, MVT), the -325 mesh particles were collected by 

centrifuging (10,000 revolutions per minute) the entire 

slurry volume. These fine tailings solids were allowed to air 

dry, and the clods were hand crushed to pass a 120-mesh 

screen. The air-dried samples from the wet and dry separations had a mean ( ± 1 standard deviation) moisture 

content (on 105 oc dry-weight basis) of 1.5 percent ± 1.0 

percent. 

Samples of the siphoned and centrifuged supernatant 

from each tailings type were filtered (0.2-JJ.m pore size); 

aliquots for 226Ra determination were acidified prior to 

analysis by the radon emanation method (Yang, 1980). 

Radium-226 contents (expressed on vacuum dry-weight 

basis) and REC' s of tailings were determined by Rogers and 

Associates Engineering Corporation (Salt Lake City, Utah) 

by use of a gamma-only assay (Thamer and others, 1981) 

on samples that were deemanated by evacuation at room 

temperatures. 

Results And Discussion 

Size Distribution 

Table 9 shows the particle-size distributions of the 

five UMT samples determined by dry sieving. The +325 

mesh fraction is about 90 percent of the total by weight. In 

contrast, table 10 shows that from about 10 to 90 percent of 

the particles in the + 325 mesh-component fractions will 

pass through the 44-JJ.m-diameter openings of the 325 mesh 

screen following wet dispersion and sieving. Thus, the 

+ 325 mesh dry-sieved fractions contain mechanically staTable 10. Quantity of fine particles (-325 mesh) in drysieved fraction as determined by subsequent wet dispersion and sieving 

Tailings Dry-sieving size fraction (weight percent) 1 

0 1 2 3 4 5 

MAT ....... 63 66 50 41 42 87 

MCT ....... 71 57 24 14 24 79 

MET ....... 69 65 46 35 36 82 

MVT ....... 69 70 53 29 32 80 

CT1 ........ 17 11 11 18 63 

1

Weight percent -325 mesh following wet dispersion and sieving. 

Includes water-soluble material ( <0.2 j..Lm); see table 12 for total dissolved 

solids in water used to disperse and wet sieve the sample. 

ble (persisting through 30 minutes of rapid oscillation) 

sand-sized (2,000 to >50 JJ.m) aggregates composed of silt 

and clay (50 to >2 JJ.m and ::::.;2 JJ.m, respectively) primary 

particles. In the Monticello UMT, the highest proportion of 

these -325 mesh (wet-dispersed and sieved) particles 

occurs in the coarsest (#0, 1 fractions) and finest (#5) dry 

aggregates (about 60-90%), while the intermediate-size dry 

aggregates contain a lower proportion of -325 mesh 

particles (about 10-50%). Such aU-shaped size distribution 

may offer a partial explanation for the 226Ra content 

distribution observed by Guill (1978) for dry-sieved acidleached tailings; Guill observed a broad minimum in 226Ra 

content around 500 JJ.m and maxima around 100 and 900 

JJ.m. 

The freshly produced tailings collected at the active, 

acid-leach uranium mill, CT1, show a differing pattern of 

aggregation (table 10), with only about 10 to 20 percent of 

the material in fractions # 1-4 being -325 mesh after wet 

dispersion and sieving. The relative lack of aggregation in 

the CT1 tailings may be the result of an insufficient quantity 

of fine particles to provide cohesion. Acid-leach mills 

typically do not grind ores as finely as alkaline leach mills 

do. At the mill that produced the CT 1 tailings, the ore was 

ground so that about 80 percent was -35 mesh. The exact 

grinding specifications used at the Monticello mills are not 

known and undoubtedly varied with ore type and leaching 

process. However, at a typical alkaline-leach mill, the ore is 

ground so that about 80 percent will be - 100 mesh 

(International Atomic Energy Agency, 1980). Other possible reasons for the difference in aggregation pattern 

between the CT1 and Monticello UMT may include 

cementing materials unique to the acid-circuit-only CT1 

tailings, differences in ores processed (for example, the 

presence of lignite particles in CT1), and possible diagenetic changes in the Monticello UMT during their 20 to 40 

years of impoundment. 

It is of interest to compare the known history of 

milling and tailings disposal at Monticello to the physical 

and chemical characteristics observed in the study. The 

Radon Emanation from Uranium Mill Tailings 147 
Table 11. Properties of wet-dispersed and wet-sieved 

uranium mill tailings 

[Bq/g, becquerels per gram] 

Wet- Radon 

Tailings sieved Weight z26Ra emanation 

fraction 1 percene (Bq/g) coefficient 

(percent)3 

MAT ............. +325 36.5 4.7 18(1) 

-325 55.6 41.9 24(1) 

MCT ............. +325 57.6 8.8 16(1) 

-325 40.7 56.6 25(1) 

MET ............. +325 41.1 3.6 13(2) 

-325 55.7 31.5 23(1) 

MVT ............. +325 43.7 6.3 21(1) 

-325 54.6 24.5 33(1) 

CT1 .............. +325 80.1 6.1 12(1) 

-325 15.2 39.4 22(1) 

1

Soluble materials largely removed during wet processing. 2

See table 12 for weight percent soluble material. 3

The calculated uncertainty in the radon emanation coefficient based 

on 1 standard deviation counting statistic for counts before and after 

vacuum deemanation (Thamer and others, 1981) is shown in parentheses. 

higher proportion, following wet sieving, of + 325 mesh 

particles in the MCT tailings as compared to the other 

Monticello UMT (table 11) is a reflection of the finer 

grinding introduced in 1955 (U.S. Atomic Energy Commission, 1963) following conversion from the saltroast/carbonate-leach circuit (MCT) to the direct carbonate 

leach circuit. The mixed nature (acid- and alkaline-circuit 

UMT) of the MAT and MET tailings is reflected in the pH 

and sulfate concentrations in the water used for dispersal 

and sieving, as is the alkaline character of the MCT and 

MVT tailings (table 12). Mixed tailings are not unique to 

the Monticello site but occur at several of the sites2 being 

decommissioned under the Uranium Mill Tailings Remedial 

Action Project (UMTRAP) of the U.S. Department of 

Energy (Matthews, 1982). 

Comparison of the 226Ra distributions seen in tables 

11 and 13 clearly shows the effects of aggregation of 

low-radium-content coarse particles with high-radium- content fine particles in the dry separates. It is also of interest 

to note that while about 1 to 6 percent by weight of the 

tailings are water-soluble materials removed during the wet 

2 At Riverton, Wyo., a high-priority UMTRAP site (Matthews, 

1982), both acid- and alkaline-circuit UMT were contemporaneously 

discharged to a common tailings pond (Ford, Bacon and Davis Utah, Inc., 

1977); such UMT disposal also occurs in at least one presently licensed 

mill in the United States (U.S. Nuclear Regulatory Commission, 1979). At 

the Naturita and Durango, Colo., UMTRAP sites, sequential alkaline and 

acid treatments were used (Merritt, 1971), and liming of acid-circuit UMT, 

such as has been, or is, practiced at some mills in the United States (U.S. 

Department of the Interior, 1976; Ford, Bacon and Davis Utah, Inc., 1978) 

and elsewhere (LaRocque, 1978; Markose and others, 1982), creates still 

another form of this often-overlooked UMT class. 

148 Field Studies of Radon in Rocks, Soils, and Water 

dispersion and sieving process, only about 0.1 to 2 percent 

of the 226Ra is thus removed (table 12). At much lower 

tailings-to-water ratios, wet separation can lead to major 

soluble losses of 226Ra; studies by Skeaff (1977) involving 

cyclosizing of freshly collected acid-leach tailings showed 

the solubilization of about 30 percent of the 226Ra at a 

tailings-to-water ratio of 0.21 giL (grams per liter) (in 

contrast to the 31 giL ratio used here). 

Radon Emanation 

With wet dispersion and sieving, it is apparent that 

for all of the UMT studied here, the fine fractions (-325 

mesh) have higher radon emanation coefficients (REC's) 

than the coarse fractions (table 11). For dry-sieved samples 

(table 14), aggregation appears to mask any particle-size 

relation. The apparent lack of particle-size dependence of 

REC's noted in earlier studies (Macbeth and others, 1978) 

may, in part, result from such aggregation. 

Previous studies have focused on UMT selectively 

collected from visually discernible sand and slime areas at 

tailings impoundments. Silker and Heasler (1979) examined dry beaches and dry berms at acid-circuit and alkalinecircuit mills in the vicinity of Grants, N. Mex., and made in 

situ, borehole measurements of REC's. The average REC 

for the beach and berm UMT at the alkaline-leach site were 

43 and 40 percent, respectively, while for the acid-leach site 

they were 19 and 12 percent, respectively. The berms, by 

virtue of UMT disposal methods, are expected to contain 

the coarsest tailings. At the alkaline-leach site, a hydrocyclone separator was used to collect the coarse material for 

the berms while discharging the fines to the center of the 

tailings pond (beach). This method probably provided a 

relatively clean separation; thus, if it is assumed that any 

differences in the REC observed between the beach and 

berm are a function only of particle size, particle size 

evidently does not exert a major influence on REC's in 

these alkaline tailings. At the acid-circuit UMT site studied 

by Silker and Heasler (1979), the methods of berm construction (gravity flow of tailings from a discharge point at 

the outer edge of the impoundment and subsequent bulldozing of tailings from inside the pile to raise the berm height) 

would appear to result in a less well-defined particle size 

split between the beach and berm areas; hence, while the 

REC' s of the materials from the two zones at this site are 

considerably different, it is difficult to unambiguously 

ascribe this effect to particle size. Using data of Rogers and 

others (1980) in 14 UMT samples, one obtains a linear 

correlation coefficient of +0.38 between the bulk sample 

REC (ranging from 6 to 31% ) and the weight fraction of the 

sample passing a 200 mesh screen on wet sieving (ranging 

from 5 to 99%). While not statistically significant at the 0. 1 

level (Assaf and Assaf, 1974), it does suggest a weak 

association in which the REC increases as the proportion of 

fine particles in the UMT increases. Investigators at the Los 

Alamos Scientific Laboratory (Dreesen and others, 1981) 
Table 12. Analysis of filtered water collected following aqueous dispersion and sieving of uranium mill tailings 

[mg/L, milligrams per liter; Bq/L, becquerels per liter] 

Water-soluble material Water-soluble 226Ra 

Tailings pH Sulfate Total dissolved in tailings based on 226Ra as fraction of total 

(mg/L) solids (mg/L) total dissolved solids (Bq/L) 226Ra in bulk tailings 

(weight percent) sample (percent) 

MAT ......... 7.0 1,300 1,880 6.0 1.63 0.19 

MCT ......... 9.2 91 193 .61 .78 .08 

MET ......... 7.8 540 875 2.8 3.26 .51 

MVT ········· 9.7 61 218 .69 .59 .11 

CTl .......... 4.0 920 1,370 4.3 5.92 1.6 

Table 13. Distribution of radium-226 in uranium mill tailings as a function of particle size (dry sieving) 

[The relative 1 standard deviation counting statistic for the values shown was 2 percent or less; all measurements are in becquerels per gram] 

Dry-sieving size fraction Whole sample 

Tailings 0 2 3 4 5 6 By analysis By summation of 

size fractions 

MAT ......... 19.0 22.1 22.6 20.2 20.3 31.1 40.0 26.6 23.6 

MCT ......... 10.7 25.3 22.7 17.9 27.0 54.4 67.0 31.1 30.1 

MET ......... 15.4 19.5 15.7 14.0 15.1 24.3 34.2 20.4 19.7 

MVT ......... 4.1 9.8 12.7 12.0 15.4 25.4 34.7 17.4 17.3 

CT1 .......... 9.0 8.5 7.7 10.9 25.5 32.7 11.5 11.0 

'Fractions 0 and 1 combined, as the + 10 mesh quantity are negligible. 

Table 14. Radon emanation coefficient of particle-size fractions (dry sieving) of uranium mill tailings 

[Values in percent; the calculated uncertainty in the radon emanation coefficient based on 1 standard deviation counting statistic for counts before and after 

vacuum deemanation (Thamer and others, 1981) is shown in parentheses] 

Dry sieving size fraction Whole sample 

Tailings 0 2 3 4 5 6 By analysis By summation of 

size fractions 

MAT ......... 4(2) 11(1) 20(1) 21(1) 19(1) 18(1) 19(1) 21(1) 17 

MCT ......... 22(1) 21(1) 21(1) 20(1) 19(1) 20(1) 20(1) 21(1) 18 

MET ......... 12(1) 15(1) 14(1) 16(1) 11(1) 13(1) 14(1) 14(1) 14 

MVT ......... 4(3) 29(1) 27(1) 27(1) 25(1) 26(1) 23(1) 27(1) 27 

CT1 - 1 .......... 7(1) 7(1) 9(1) 11(1) 12(1) 10(1) 9.4(0.7) 9.1 

'Fractions 0 and 1 combined, as the + 10 mesh quantity are negligible. 

have studied "sands" (about 80 percent sand-sized particles) 

and "fines" (about 80 percent silt-sized particles) collected 

from select areas of the inactive UMT piles at Shiprock, 

N. Mex. (acid-leach site), and Durango, Colo. (mixed 

UMT). The Shiprock sands and fines have nearly identical 

RECs (10 and 11% , respectively), while the REC of the 

Durango sand was less than that of the fines (19 and 26, 

respectively). Ryon and others (1977) have investigated 

nitric acid leaching of uranium ores and mill tailings as a 

radium removal technique and have determined REC' s on 

the + 140 mesh (105 J.l.m) and -140 mesh wet-sieved 

fractions of these nonconventional UMT (in which about 

95 % of the radium, as opposed to about 1% for conventional UMT, is removed). In all cases, the REC of the+ 140 

mesh fraction (5 to 36%, average 15%) was less than that 

for the -140 mesh fraction (17 to 57% , average 37%). 

Taken together, these studies suggest that where wet segregation of UMT has occurred, fines tend to have somewhat 

higher REC's than coarse tailings, a finding that is in 

general agreement with the findings of the present study. 

The reason for the observed particle size to REC 

relationship is probably more than just a surface area effect. 

In some sedimentary rock samples, the REC has been 

shown (Andrews and Wood, 1972) to be proportional to the 

square root of the particle diameter. However, as demonstrated in several investigations with soils and rocks (BarRadon Emanation from Uranium Mill Tailings 149 
retto, 1971; Andrews and Wood 1972; Megumi and 

Marumo, 1974), a direct correlation between radon emanating power and particle size (over a large range of particle 

sizes) can be expected only where the radium isotope 

precursors are uniformly distributed in the soil or rock. 

Such a distribution is not the norm in soils and rocks 

(Tanner, 1980), and certainly not in UMT, where redistribution of 226Ra during both acid-circuit milling (Whitman 

and Beverly, 1958; Skeaff, 1981) and alkaline-circuit milling (Lakshmanan and Ashbrook, 1978), and inherited 

226R . h fi patterns from ore, tends to concentrate a m t e me 

fraction of the UMT. Thus, the tacit assumptions that the 

higher REC of the fines is purely a function of their smaller 

particle dimensions and that the higher emanation coefficients generally observed for alkaline-circuit, as compared 

to acid-circuit, UMT are due only to their finer grinding, 

should be examined. Other factors, perhaps related to the 

chemical or mineralogical form of 226Ra in the fine UMT 

(and in alkaline-circuit UMT), may also enhance their 

emanating power. 

Dreesen and others ( 1981) have demonstrated reductions of 80 to 90 percent in the REC upon annealing UMT 

at temperatures around 900 oc. The mean REC determined 

by Austin and Droullard (1978) for the Colorado Plateau 

ores that were exploited during the operating era of the 

Monticello mill (Fischer, 1956) is about 20 percent. With 

these facts in mind, let us consider the REC's of the MCT 

tailings, whose production at the Monticello mill included 

an 840 to 910 oc (terminal temperature) salt roast (Anonymous, 1944; Philippone, 1955); these UMT have a bulk 

REC of 21 percent (table 14). Similar REC's are also 

observed for the salt-roast UMT at the Durango, Colo., 

mill, which also processed these Colorado Plateau ores 

(Dreesen and others, 1981). Thus, it would appear that for 

ore roasting conditions that include the presence of salt, 

followed by quenching and leaching, marked reductions in 

the REC of the tailings relative to the ore do not occur or do 

riot persist. Studies by the U.S. Bureau of Mines (Austin 

and Droullard, 1979) on the effects of heating (without salt) 

on radon emanation from uranium ores (not subsequently 

put through a mill circuit) indicate that decreases in the REC 

induced by heat treatments may be partially restored upon 

aging at room temperature. Also, the redistribution of 

radium during milling noted above probably mitigates any 

initial reduction in the REC of the ore. 

INFLUENCE OF ORE TYPE AND MILLING 

PROCESS ON RADON-222 EMANATION 

COEFFICIENTS OF URANIUM MILL TAILINGS 

The chemical form of 226Ra in precipitates (Hahn, 

1936; Wahl1951) and in natural geologic materials (Austin 

and Droullard, 1978) can influence the emanation of 222Rn 

produced in such materials. Radon-222 emanation from 

150 Field Studies of Radon in Rocks, Soils, and Water 

uranium ores (Leach and others, 1982} and from UMT 

(U.S. Nuclear Regulatory Commission, 1980) is a radiological health concern. In making prospective radiological 

impact assessments of uranium milling operations, a fundamental question is how does the milling process influence 

the environmental mobility of radionuclides associated with 

the uranium ores being treated? Although the 226Ra inventory in UMT solids generally accounts for about 98 percent 

of that in the parent ore, extensive solubilization and 

redistribution between particle-size fractions have been 

demonstrated to occur in both acid (Whitman and Beverly, 

1958; Skeaff, 1981) and alkaline (Lakshmanan and Ashbrook, 1978) milling circuits. Such redistribution undoubtedly involves changes in the geochemical hosts of the 226Ra 

in the ores versus the tailings (Landa, 1982); hence, 

changes in radon emanation characteristics may be anticipated. In the only previous study known to the author 

relating to this problem, workers at Oak Ridge National 

Laboratory (Ryon and others, 1977) sampled ore and 

tailings at three acid-leach and two alkaline-leach uranium 

mills in New Mexico, Utah, and Wyoming. In all cases, the 

REC's of the tailings at the acid-leach mills were less than 

those of the corresponding ore, while at the alkaline-leach 

mills, the REC' s of the tailings were higher than those of 

the corresponding ore. 

This section describes a laboratory study in which 

uranium ore samples of distinct mineralogies, rather than 

composite mill feeds, were subjected to acid and alkaline 

leaching for uranium extraction. In this way, both the ore 

type and extraction process serve as experimental variables, 

and the problems (Landa, 1982) in obtaining a matched set 

of ore and its resultant tailings at mills processing blended 

ores at rates of several hundred to several thousand tons per 

day are avoided. 

Materials and Methods 

The following mineral samples were obtained3

: ( 1) 

autunite/meta-autunite in pegmatite, Ruggles Mines, near 

Grafton Center, N.H., (2) carnotite in sandstone, San 

Rafael Swell, Utah, and (3) uraninite in a matrix of iron and 

manganese carbonates, and quartz, Northwest Territory, 

Canada. 

Samples were crushed and initially reduced to a 

nominal -28 mesh (590 JJ-m) by ceramic plate grinder. A 

split of this material was ground to -100 mesh (149 JJ-m), 

the finer particle size being required for effective alkaline 

leaching of uranium. Aliquots of about 300 g each were 

prepared by splitting the -28 mesh and -100 mesh 

materials. Two such aliquots of each grind size of each ore 

type were analyzed for 226Ra content (expressed on 

vacuum-dry-weight basis) and the REC by Rogers and 

3

Ward's Natural Science Establishment, Rochester, NY 14692. 
Table 15. Characteristics of ore samples and leaching 

conditions used 

[Values for uranium and vanadium in parts per million; all other values in 

percent] 

Ore type 

Autunite Carnotite Uraninite 

Uranium .......... 18,200 857 27,000 

Carbonate carbon ... <.01 <.01 3.12 

Aluminum ......... 8.6 1.4 1.5 

Iron .............. .66 .91 8.5 

Manganese ........ .23 .0032 >10 

Calcium .... 0 ••• ••• 2.3 .02 .84 

Phosphorus ........ 2.0 .18 <.01 

Vanadium ......... <4 170 <4 

acid alkaline acid alkaline acid alkaline 

Leaching conditions . 

(see footnotes I 4 I 3 2 4 

for descriptions) 

I 0.5 M H2S04; 2 hours in autoclave (122 °C). 2 1.25 M H2S04 ; 4 hours at room temperature to initiate carbonate 

digestion, then overnight (16 hours) in 80 °C oven, and finally 2 hours in 

autoclave. 3 0.5 MNa2C03 + 4.2 g NaHC03 per 100 mL; 4 hours in autoclave. 

4 0.5 MNa2C03 + 4.2 g NaHC03 per 100 mL; 9 days in 80 oc oven; 

deionized water added to bottles every 2-3 days to adjust to initial volume. 

Associates Engineering Corporation (Salt Lake City, Utah) 

by use of a gamma-only assay on dry samples that were 

de-emanated by evacuation at room temperature (Thamer 

and others, 1981). These same aliquots were then leached 

as described here. 

Simple laboratory-scale uranium extraction procedures using only air oxidation were developed to approximate commercial practices (Merritt, 1971). Acid leaching 

was done on the -28 mesh ground material, while alkaline 

leaching was done on the - 100 mesh ground material. 

Leaching was done in loosely capped polypropylene bottles 

containing 30 g of ore, 100 mL of either sulfuric acid 

(H2S04) or sodium carbonate (Na2C03) solution, and, in 

the case of the alkaline leaching, 4.2 g of sodium bicarbonate (NaHC03). Bottles were placed in either an autoclave 

operated at 122 °C and 1.27 kg/cm2 (kilograms per square 

centimeter) or a conventional oven operated at 80 °C. 

Solution concentrations and leaching conditions are given in 

table 15. For acid leaching of the autunite and carnotite 

samples, 0.5 M H2S04 was used. For the uraninite sample, 

a modified procedure was necessary to compensate for acid 

consumption by carbonates. In the alkaline leaching case, 

the carnotite ore was amendable to a 4-hour autoclave 

procedure, but uranium extraction from the other two ores 

was only about 60 percent under these conditions. Experimentation showed that the extraction could be increased to 

about 80 percent by treatment for about a week at 80 °C in 

a conventional oven, and such a procedure was adopted. 

Immediately following the heating/leaching period, the 

warm slurries were vacuum filtered by use of a Buchner 

funnel and highly retentive, hardened filter paper (Whatman 

no. 50). The collected tailings (1 bottle per filter) were filter 

washed with about 75 mL of deionized water, allowed to air 

dry, and lightly crushed by hand. These samples (mean 

moisture content = 0.09% ±0.04% (1 standard deviation)) 

were then analyzed for uranium and 226Ra content and for 

the REC. 

Uranium content of ore and tailings was detemined by 

the delayed neutron method (Millard and Keaton, 1982), 

and carbonate content of ore was determined by the acidneutralization method (Allison and Moodie, 1965). Other 

constituents were determined by induction-coupled argon 

plasma spectrometric analysis (Taggart and others, 1982). 

Particle-size distribution (±325 mesh (44 J.Lm)) of ground 

ore and tailings samples was determined by wet dispersion 

and sieving. 

Results and Discussion 

A comparison of the uranium contents of the ores 

(table 15) and the tailings (table 16) shows removal of from 

78 to 99 percent of the uranium by the milling treatments 

used. The agreement between the REC's measured (table 

16) for the -28 mesh and the -100 mesh grind-size 

samples of each ore type (for example, -28 mesh autunite 

versus - 100 mesh autunite) suggests that finer grinding of 

ores (table 17) is not necessarily associated with higher 

REC' s. These findings are in general agreement with those 

of Austin and Droullard (1978), who compared emanation 

coefficients of whole rock versus disaggregated samples, 

although they did observe significant increases (34 to 227 

percent) in the REC's of some samples after going from 

whole rocks to -100 mesh (nominal) pulps. In the case of 

UMT, the finer grinding of alkaline-leach tailings has been 

suggested as the reason for the higher REC's reported, 

compared to the coarser ground, acid-leach tailings (U.S. 

Nuclear Regulatory Commission, 1980). While such a 

relationship may be an indirect result of the greater available surface area on which redistributed 226Ra can take up 

residence, it appears unlikely that the effect is purely 

physical and due to comminution of the ore. 

In the case of acid leaching, the REC of the autunitederived tailings is about the same as that of the ore, whereas 

for the carnotite- and uraninite-derived tailings, the REC's 

are considerably lower than those of the respective ores. In 

the case of alkaline leaching, the REC of the autunite· 

derived tailings increased, while that of the carnotitederived tailings decreased considerably with respect to the 

ores. The REC's of the alkaline-leach, uraninite-derived 

tailings are about the same as those of the ore. Tailings from 

the acid treatment of the uraninite ore showed a decrease in 

REC despite an increase in the -325 mesh size fraction 

from about 13 weight percent in the ore to 22 weight percent 

in the tailings (table 17). This shift toward finer grained 

material was associated with the digestion of carbonate and 

Radon Emanation from Uranium Mill Tailings 151 
Table 16. Radium-226 content and the radon-222 emanation coefficient (REC) of ore and tailings, and the yield and 

uranium content of tailings 

[Bq/g, becquerels per gram; %, percent; ppm, parts per million] 

Sample Ore 

Ore type mesh/split 226Ra 1 REC Yield2 no. (Bq/g) (%) 

Autunite -28/1 214±0.3 4±1 94.6 

-28/2 216±0.1 2±1 94.1 

-100/3 212±0.1 4±1 

-100/4 209±0.1 4±1 

Carnotite -2811 9.4±0.04 12±1 99.0 

-28/2 10.2±0.04 17±1 99.1 

-100/3 9.8±0.04 18±1 

-100/4 9.8±0.04 19±1 

Uraninite -28/1 302±0.2 12±1 63.1 

-28/2 322±0.3 14±1 63.2 

-100/3 309±0.2 13± 1 

-100/4 311±0.2 15± 1 

'Uncertainty shown based on 1 standard deviation counting statistic. 

~ g tailings solids 

-Percent yield = X 100. 

gore 

other acid-soluble phases in the ore. For the other oretailings pairs, the acid or alkaline leaching did not influence 

the -325 mesh size distribution. 

No consistent pattern enabling the prediction of the 

REC' s of tailings on the basis of ore type emerges from the 

analysis of the data presented in table 16. It is apparent that 

the REC of the tailings cannot be assumed, a priori, to be 

the same as that of the ore from which it is derived. In the 

acid-leach case, there is a clustering of tailings' REC's 

around a value of about 5 percent, despite starting ores of 

differing uranium mineralogies and rock types. Such behavior might possibly be expected if all the 226Ra present in the 

ore were released to solution and subsequently precipitated 

or retained by some other mechanism in a specific chemical/mineralogical form in the tailings dictated largely by the 

lixiviant solution. Nirdosh and others (1984) have discussed 

in detail the various mechanisms by which 226Ra can be 

retained in UMT (for example, coprecipitation, surface 

adsorption on amorphous silica and hydrated metal oxides, 

ion exchange on clay minerals). The emanating power of 

these retained forms can vary widely at room temperature; 

for example, while 226Ra coprecipitated with barium sulfate 

generally emanates less than 1 percent of the 222Rn generated, that coprecipitated with or sorbed on hydrous iron 

oxide can emanate nearly 100 percent of the 222Rn produced 

(Hahn, 1936). While REC's of dry samples are reported 

here, increasing moisture content can be expected to 

enhance radon emanation from both ores and tailings 

(Thamer and others, 1981). 

152 Field Studies of Radon in Rocks, Soils, and Water 

Acid-leach tailings Alkaline leach tailings 

Uranium 226Ra REC Yiefd1 Uranium 226Ra REC 

(ppm) (Bq/g) (%) (ppm) (Bqt!g) (%) 

2,840 183±1.1 5±1 

3,990 184± 1.1 2±1 

96.9 3,450 176±1.1 12±1 

96.8 3,130 173± 1.1 12±1 

10.5 9.9±.1 4±2 

7.9 10.0±.2 7±3 

99.0 15.4 8.9±.1 6±2 

99.3 13.5 8.3±.1 4±3 

1,160 310±1.5 7±1 

1,310 329±1.8 5±1 

96.6 6,290 229±1.5 12±1 

96.7 5,990 221 ± 1.1 11±1 

Removals of 226Ra from the ore by the leaching 

processes (table 18) are generally higher than the 1 to 2 

percent commonly reported on the basis of in-mill sampling 

Table 17. Particle-size distribution of ore and tailings samples as determined by wet sieving 

Sample Weight percent -325 mesh 

Ore Tailings 

28-mesh ground, acid-leach tailings 

Autunite . . . . . . . . . 4.9 

Carnotite . . . . . . . . . 6.5 

Uraninite . . . . . . . . . 12.8 

100-mesh ground, alkaline-leach tailings 

Autunite . . . . . . . . . 12.9 

Carnotite . . . . . . . . . 13.8 

Uraninite ........ . 27.6 

5.4 

6.3 

22.2 

14.4 

13.5 

25.9 

Table 18. Percentage of radium-226 (initially in ore) found 

in tailings solids (adjusted for tailings yield) 

[Value shown is mean of duplicate samples] 

Ore type 

Autunite ......... . 

Carnotite ......... . 

Uraninite ......... . 

Acid-leach tailings 

(percent) 

80.5 

100.9 

64.6 

Alkaline-leach tailings 

(percent) 

80.3 

87.1 

70.2 
(Moffett, 1976). One can only speculate on the reasons for 

this difference (for example, variance from actual mill 

leaching practices); however, it is interesting to note that 

under certain milling conditions, considerable quantities of 226Ra can enter the liquid effluent waste stream. 4 

4

Skeaff (1981) presents an excellent discussion showing that the 

quantity of 226Ra measured in solution at various stages of an acid-leach 

uranium mill circuit was orders of magnitude lower than the limits imposed 

by the solubility of RaS04 in sulfuric acid (75 °C). Recently, Torma and 

others (1985) have reported extraction of about 40 percent of the 226Ra 

from uranium ore leached with sodium carbonate-bicarbonate in laboratory 

tests. 

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Radon Emanation from Uranium Mill Tailings 153 
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154 Field Studies of Radon in Rocks, Soils, and Water 

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waste water: Health Physics, v. 30, p. 1059. 
PART 1: STUDIES OF RADON IN ROCKS AND SOIL 

SECTION 3: ESTIMATING RADON POTENTIAL 

USE OF AERIAL GAMMA-RAY DATA TO ESTIMATE RELATIVE AMOUNTS OF RADON 

IN SOIL GAS 

joseph S. Duval 

Abstract 

Because aerial gamma-ray measurements of equivalent uranium are an indirect measure of radium-226 and a 

direct measure of bismuth-214, which is a daughter isotope separated from radon-222 by short-lived isotopes of 

polonium and lead, gamma-ray data can be used to 

estimate the relative amounts of radon in soil gas. Theoretical calculations are available that enable an interpreter 

to define the limitations on the coverage provided by an 

aerial survey. Aerial survey data for the State of New Jersey 

are compared to indoor radon measurements. The results 

of this comparison support the use of aerial gamma-ray 

data to estimate the relative concentrations of radon in 

soil gas, and published data comparing radon concentrations in soil gas to surface gamma-ray measurements 

provide corroborating evidence. The application of Swedish criteria for assessing radon hazards to the data for New 

jersey suggests that hazard-assessment criteria from one 

area may not be correct for other, geologically different 

areas. 

INTRODUCTION 

In 1985, a house located within the geological province known as the Reading Prong was discovered to have 

indoor radon-222 e22Rn) concentrations exceeding 2,000 

pCi/L (picocuries per liter), and other houses having elevated indoor radon concentrations were quickly identified in 

the same neighborhood (Gaertner, 1987). The State of 

Pennsylvania immediately began a large program to determine the extent of the problem by distributing radon 

detection kits to homeowners located within the Reading 

Prong (Gerusky, 1987). The results of this program showed 

that more than 50 percent of the houses measured had 

indoor radon concentrations exceeding the 4. 0 pCi/L guideline set by the Environmental Protection Agency. Data from 

other parts of the Nation soon made it obvious that the 

Reading Prong is not the only place that has an indoor radon 

hazard. The possibly widespread nature of the indoor radon 

hazard made efficient identification of those parts of the 

nation that have the greatest potential for indoor radon 

problems a primary concern. Because aerial gamma-ray 

measurements provide an estimate of the surface concentrations of radium-226 e26Ra), which is a precursor of 

222Rn 

. 3.823 days 

214p 0 

0.00164 sec 

Figure 54. Part of the radioactive decay series of uranium238 showing radium-226 e26Ra) and daughter nuclides 

including radon-222 e22Rn); 218Po, polonium-218; 214Pb, 

lead-214; 214Bi, bismuth-214; 214Po, polonium-214. 

radon, the aerial gamma-ray surveys conducted as part of 

the U.S. Department of Energy National Uranium Resource 

Evaluation (NURE) Program can be used to make maps 

showing the distribution of 226Ra. These maps can be used 

to estimate relative concentrations of radon in soil gas. This 

report presents an example for the State of New Jersey that 

illustrates the utility of such maps. 

AERIAL GAMMA-RAY SURVEYS AND RADON 

Aerial gamma-ray surveys are generally used to 

estimate the apparent surface concentration of uranium by 

measuring the flux of 1. 76-MeV (million electron volt) 

gamma rays produced by the decay of bismuth-214 e14Bi). 

The survey data can also be expressed as apparent 

concentrations of 226Ra, which is the last long-lived (1 ,602 

yr) member of the uranium-238 e38U) radioactive decay 

series. Because 214Bi is directly linked to 222Rn (hereafter 

designated simply as radon) by short-lived isotopes and 

because 222Rn is the direct daughter of 226Ra (fig. 54), the 

gamma-ray data provide an estimate of the near-surface 

concentration of radon. Because the radium is located inside 

Use of Aerial Gamma-Ray Data to Estimate Radon in Soil Gas 155 
mineral grains as well as in soil pore spaces and on grain 

surfaces, some fraction of the total radon is locked inside 

the soil materials and is unable to diffuse into the soil gas. 

The emanation power is defined as the fraction of the total 

radon produced that escapes into the soil gas and is largely 

controlled by the distribution of radium within the rocks and 

soils (Tanner, 1964). The relative concentrations of radon 

in the near -surface materials can, however, be used as a firstorder estimate of the relative radon concentrations in the 

soil gas. Other factors that affect the radon concentrations in 

the soil gas are the soil moisture content and the soil 

permeability. Soil moisture can, to some extent, increase 

the emanation power of a material (Hahn, 1936; Starik and 

Melikova, 1957), but high soil moisture causes the effective 

emanation power (radon availability) to approach zero 

because the water fills the soil pores, replaces the soil gas, 

and inhibits diffusion of the radon (Morozova and 

Mukhraneli, 1971). Soils or rocks having high gas permeability are affected by convective processes that reduce the 

radon concentrations in the top 1 to 2m (meters) and allow 

the radon to move distances of 5 m or more (Tanner, 1964, 

1980; Schery and others, 1984). 

The NURE aerial gamma-ray surveys were flown at a 

nominal altitude of 122m above the ground, a height that 

provides a measurement path approximately 250 m wide 

beneath the flight line (Pitkin and Duval, 1980). The 

gamma-ray signals from the ground are attenuated by the 

ground itself and the air. The effective thickness of material 

measured is about 30 em (Duval and others, 1971). The 

flight-line spacings of the NURE surveys range from 1.6 to 

10 km, with most of them having either 5- or 10-km 

intervals. These flight-line spacings (5-10 km) result in a 

total ground coverage of less than 10 percent (Pitkin and 

Duval, 1980); thus, maps made from these data are generally not suitable for site-specific studies. The data along the 

flight lines could, however, be used to provide site-specific 

information. 

DISTRIBUTION OF RADIUM IN NEW JERSEY 

Figure 55 shows the NURE aerial gamma-ray surveys 

that were computer processed and compiled to make the 

map of the distribution of radium in New Jersey shown in 

figure 56. The NURE flight-line data were first inspected, 

and all data measured at ground clearances greater than 200 

m were rejected as invalid because of the low signalto-noise ratio caused by air attenuation of the gamma-ray 

flux. The data were then filtered by use of a 3-point median 

filter as a spike rejection technique followed by a 17-point 

Gaussian filter to smooth out statistical fluctuations in the 

data. The data were then gridded by use of a minimum 

curvature algorithm (Briggs, 1974; Webring, 1981) and a 

grid interval of 3.2 km. The gridded data were examined as 

a gray-scale image by use of image processing techniques, 

156 Field Studies of Radon in Rocks, Soils, and Water 

SCRANTON 

DOE, 

41 ° 

DOE, 

SALISBURY 

DOE, 1980a 

Figure 55. Index map showing the NURE aerial gamma-ray 

surveys used to compile the data for New Jersey. DOE, 

U.S. Department of Energy. 

and some of the data sets were found to have relative level 

errors. The term "relative level error" is used here to 

describe the fact that data sets from different NURE 

contractors frequently exhibit obvious disagreements when 

the data are merged and portrayed in an image format. 
RADIUM CONCENTRATION 

( pCi /g) 

1. 6 

1.4 

1. 2 

1.0 

O.B 

0. 6 

0.4 

0.2 

o.o 

0 15 30 KM 

0 10 20 MILES 

Figure 56. Contour map of the near-surface concentrations of radium in New jersey. pCi/g, picocuries per 

gram. 

Because these data had been corrected for background by 

use of on-board measurement techniques, the level differences were treated as scaling errors caused by calibration 

errors or soil moisture differences, and the data were 

multiplied by a constant. 

Because the NURE data sets do frequently show 

disagreements, multiple data sets should be processed 

simultaneously; for this example, data outside the quadrangles shown in figure 55 were included in the data compilation. The resulting image was used to determine that all of 

the data sets covering New Jersey needed to be multiplied 

by a factor of 0.9 to achieve agreement with the adjacent 

data sets. The determination of this value was based upon a 

subjective examination of the gray-scale image. Experience 

with this approach has shown that relative level differences 

on the order of 5 percent can be seen in the image. 

INDOOR RADON IN NEW JERSEY 

In trying to utilize the aerial gamma-ray data, one 

must determine the appropriate scale at which to make 

comparisons and predictions. Because of convenience and 

ease of representation, one is tempted to use broad regional 

categories such as geologic provinces or physiographic 

regions. Political boundaries are also viewed as convenient 

for summarizing data. To some extent the use of physiographic provinces, county boundaries, and localized sites 

has been dictated by the availability of radon data. 

In September of 1987, the New Jersey Department of 

Environmental Protection (NJDEP) released data showing 

the regional distribution of indoor radon concentrations in 

New Jersey (NJDEP, 1987). The data consisted of more 

than 5,000 measurements of indoor radon concentrations. 

The sample locations are distributed nonuniformly across 

the State, and the data are summarized by physiographic 

provinces in figure 57. The average radon values were taken 

from the NJDEP press release, and the average radium 

values were calculated from the data of figure 56. The 

boundaries of the physiographic provinces were taken from 

the "Geologic Map of New Jersey" (Lewis and Kummel, 

1912) and were defined as follows: "outer Coastal Plain" 

corresponds to the Tertiary rocks, "inner Coastal Plain" 

contains the Cretaceous rocks, "Triassic basins" includes 

the Triassic rocks, "Reading Prong" includes the Precambrian crystalline terrane, and the "Valley and Ridge" 

province includes the Devonian, Silurian, and Ordovician 

rocks. An examination of the information presented in 

figure 57 shows that the average indoor radon level does 

tend to increase as the average surface radium concentration 

increases, but the relationship is not consistent. Part of the 

reason for this apparent inconsistency is the fact that the 

radium concentrations within the physiographic provinces 

are not uniform. Figure 58 presents the frequency histogram 

of radium concentrations within the Valley and Ridge 

province and shows a bimodal distribution. Although the 

distribution functions of the other provinces are not obviously bimodal, they are similarly skewed to a greater or 

lesser extent. This skewing suggests that the comparison 

should be made by using smaller geographical areas. 

Because the NJDEP press release included a summary by 

counties (table 19), average radium values were calculated 

for the counties with available data. Figure 59 shows the 

average radium concentrations versus the average indoor 

radon concentrations for all of the counties in New Jersey 

except Hudson County, for which the aerial gamma-ray 

data are not available. These data exhibit an approximately 

linear trend up to radium concentrations on the order of 1 

pCi/g (picocurie per gram). 

DISCUSSION 

Although the comparisons presented above support 

the use of aerial gamma-ray data to estimate relative indoor ~ 

Use of Aerial Gamma-Ray Data to Estimate Radon in Soil Gas 157 
NEW JERSEY PHYSIOGRAPHIC PROVINCES 

AVERAGE INDOOR RADON AND SURFACE RADIUM 

VALLEY AND RIDGE 

AVG. RADON = 8.2 pCi/L 

AVG. RADIUM = 0.87 pCilg 

READING PRONG 

AVG. RADON = 8.1 pCi/L 

AVG. RADIUM = 1.03 pCi lg 

TRIASSIC BASINS 

AVG. RADON = 4.2 pCi/L 

AVG. RADIUM = 0.83 pCilg 

INNER COASTAL PLAIN 

AVG. RADON = 2.5 pCi/L 

AVG. RADIUM = 0.67 pCilg 

OUTER COASTAL PLAIN 

AVG. RADON = 0.8 pCi/L 

AVG. RADIUM = 0.27 pCilg 

Figure 57. Summary of average indoor radon and surface radium concentrations for physiographic provinces in New 

Jersey. The labels correlate with the map patterns from north to south. pCi/L, picocuries per liter; pCi/g, picocuries per 

gram. 

radon potential of large areas such as geologic provinces or 

counties, the data are subject to the following criticism: ( 1) 

the use of areas defined by political or other arbitrary 

boundaries results in the lumping of diverse geologic 

materials with significantly different radium concentrations 

and reduces the validity of the comparison and (2) indoor 

radon measurements include variance that is a function of 

158 Field Studies of Radon in Rocks, Soils, and Water 

the building construction, which is largely independent of 

the geologic environment. The use of indoor radon data can 

be eliminated by making comparisons with measurements 

of radon concentrations in soil gas. Gunderson and others 

(1988) have made measurements of radon concentrations in 

soil gas as well as surface radium concentrations for 

different geologic materials in Montgomery County, Md., 
RADIUM CONCENTRATION (pCi/g) 

Figure 58. Frequency histogram of radium concentrations 

within the Valley and Ridge province. pCi/g, picocuries 

per gram. 

Table 19. Average indoor radon levels for counties in New 

jersey 

[pCi/L, picocuries per liter] 

Average indoor Average indoor County County radon (pCi/L) radon (pCi/L) 

Atlantic ....... 0.75 Middlesex ..... 2.16 

Bergen ........ 1.85 Monmouth .... 2.68 

Burlington ..... 1.80 Morris ........ 5.13 

Camden ....... 2.27 Ocean ........ .95 

Cape May . . ... 1.43 Passaic ....... 3.67 

Cumberland .. . 1.79 Salem ........ 2.49 

Essex ......... 1.23 Somerset ...... 5.20 

Gloucester ..... 3.12 Sussex ........ 6.47 

Hudson ....... 2.47 Union .. . . . ... 2.32 

Hunterdon ... . . 6.88 Warren ....... 11.83 

Mercer . . .... .. 4.46 

and figure 60 presents those data with a calculated linear fit. 

The linear fit results in the equation 

Rn= -654.2+2367.5 Ra. (1) 

The use of a linear equation to fit the data was 

predicated by the following: (1) the available data are few in 

number and do not cover a large range of values and (2) a 

linear dependency is the simplest case. Because radium is 

the direct parent of radon, it is possible to calculate the total 

amount of radon produced by the decay of radium, but not 

all of that radon escapes into the soil gas. For that reason an 

equation of the general form given by equation 1 should 

apply to any geologic material. There is, however, no 

reason to expect that the same equation will apply to various 

geologic materials unless the radon emanation powers of the 

different materials are approximately the same. The fact 

that the linear equation reasonably represents the data 

suggests that the general geologic and geochemical conditions of the measured geologic units have resulted in 

1.0 

<>O 

0.5 

8 <> 

<> 

<> 

0. 0 l........o......A-....___j'--'--'--............ __._...._.......J,._._.........,--~.........__ ............ ......L.. ............. ___._......__ .......... 

0 2 4 6 8 10 12 

AVERAGE INDOOR RADON IN NEW JERSEY COUNTIES (pCi/L) 

Figure 59. Average radium concentration versus the average indoor concentrations in counties in New jersey. 

pCi/L, picocuries per liter; pCi/g, picocuries per gram. 

-

~ 

' u 

a. ........, 

(/) 

< C) 

~ 

0 

(/) 

~ 

z 

0 

c 

< 0::: 

1500 

1000 

GNEISS 

TRIASSIC SEDit.iENTS <> 

<> t.iAF'IC 

<>TERTIARY GRAVELS 

soo~~___._~~...._-L~--~~~--~_.__~--~ 

0.0 0.5 1.0 

RADIUM CONCENTRATION IN SOIL (pCi/g) 

Figure 60. Average radon concentrations in soil gas versus 

average surface radium concentrations for various geologic materials in Montgomery County, Md. (adapted 

from Gunderson and others, 1988). The straight line is a 

linear least-squares fit to the data. pCi/L, picocuries per 

liter; pCi/g, picocuries per gram. 

near-surface radium distributions that produce approximately equal radon emanation powers. Because the equation provides a predictive capability, these data provide 

corroboration and additional support for the use of surface 

gamma-ray measurements to predict relative amounts of 

radon in soil gas. 

RADON HAZARD ASSESSMENT 

Radon hazard assessment in the United States is not 

yet well developed. Recent efforts by Gunderson and others 

( 1988) and Otton and others ( 1988) combine radon soil-gas 

Use of Aerial Gamma-Ray Data to Estimate Radon -in Soil Gas 159 
Figure 61. Radon assessment map based upon the Swedish criteria, the data of figure 60, and figure 

56. 

160 Field Studies of Radon in Rocks, Soils, and Water 
data, surface gamma-ray measurements, and geologic data 

to define a relative ranking within the areas studied. These 

studies do not provide any specific rules for assessing radon 

hazards. Sweden has established criteria for radon hazard 

assessment. These criteria consider that concentrations of 

radon in soil gas less than 270 pCi/L are "low" and require 

no special construction, the range 270-1,350 pCi/L is 

classified as "normal" and requires "radon protective" 

construction, and values greater than 1,350 pCi/L are 

"high" and require "radon safe" construction (Akerblom, 

1986; Wilson, 1987). The natural tendency is to try to apply 

these same criteria to other geologic environments. The 

validity of applying the Swedish criteria to New Jersey can 

be tested if we make some assumptions about the radon in 

the soil gas. 

If the soil-gas data from Montgomery County, Md., 

are assumed to apply to New Jersey, the radium data of 

figure 56 and the Swedish criteria can be used to define a 

radon assessment map as shown in figure 61. The validity 

of this map can be tested by comparing it to the data for the 

New Jersey counties listed in table 19. In figure 61, Atlantic 

and Cape May Counties are largely classified as "normal," 

and application of the Swedish criteria would not require 

any special new home construction methods. The indoor 

radon data of table 19 suggest that this classification is 

correct. Salem, Gloucester, Monmouth, and Middlesex 

Counties are largely classified as "normal" to "high," and 

application of these criteria would require most new home 

construction in these counties to be either "radon protective" or "radon safe." The data in table 19 do not support 

this classification. Burlington and Ocean Counties have 

over half of their area classified as "low" with the remainder 

being mostly "normal." The data in table 19 suggest that 

much more than half of these counties should be classified 

as "low." Warren, Hunterdon, Morris, Sussex, Passaic, and 

Somerset Counties are largely classified as "high," and the 

Swedish criteria would require that most new home construction be "radon safe." The data in table 19 suggest that 

a significant fraction of the areas classified as "high" 

probably should be so classified, but it is not clear how 

much of the "high" area is correctly classified. 

The radon assessment presented in figure 61 is not 

consistent with the available indoor radon data. This inconsistency must be at least partly caused by the use of criteria 

that are based upon only one of the factors that control 

radon availability. This exercise in radon hazard assessment 

is useful because it points out that the use of inadequate 

criteria can result in requirements for potentially expensive 

construction techniques in areas where they may not be 

needed. The Swedish scientists did include geologic data in 

their work and stated that permeability and rock type must 

be considered, but the criteria given herein are based solely 

upon the radon concentrations in the soil gas. 

Tanner (1988) discusses a technique that provides a 

measure of the amount of radon available for entry into a 

building. This measurement of "radon availability" includes 

the emanation power, soil permeability, and soil moisture 

effects in a single measurement and would be a better basis 

for hazard assessments. 

CONCLUSIONS 

The data and comparisons presented in this paper 

support the following conclusions: (1) although absolute 

estimates of radon in soil gas may not be possible, aerial 

gamma-ray measurements of near-surface concentrations ?f 

radium can be used to estimate relative levels of radon m 

soil gas, (2) aerial gamma-ray data are positively correlated 

with indoor radon levels, but the use of political or 

physiographic boundaries for data summaries may result in 

significant errors because of geologic variations within 

those boundaries, (3) the application of radon hazard 

assessment criteria from one area to another will not be 

valid unless both areas have similar climatic, geologic, and 

geochemical histories that produce similar radium distributions, emanation powers, soil moisture, and soil permeability, ( 4) simplistic radon hazard criteria should not be used, 

and any criteria that are developed should include the radon 

concentration in the soil gas, soil permeability, and soil 

moisture, and (5) aerial or ground gamma-ray data should 

be used only to estimate the relative amounts of radon in 

soil gas until more data are available to better test the 

calculation of actual radon concentrations. The data needed 

to establish whether surface gamma-ray measurements can 

be used to estimate absolute amounts of radon in soil gas are 

similar to the data collected by Gunderson and others 

(1988). Because the emanation power of geologic materials 

depends upon the geologic history of the lithologic units, 

data need to be gathered for a variety of geologic and 

climatic environments. In the collection of these data it is 

critical that the surface gamma-ray and soil gas measurements be made simultaneously and that various soil gas 

measurements be made at a single site so as to reduce the 

variance of the measurements. 

REFERENCES CITED 

Akerblom, G., 1986, Investigation and mapping of radon risk 

areas: Lulea, Sweden, Swedish Geological Company, Report 

IRAP 86036, 15 p. 

Briggs, I.C., 1974, Machine contouring using minimum curvature: Geophysics, v. 39, no. 1, p. 39-48. 

Duval, J.S., Cook, B.G., and Adams, J.A.S., 1971, Circle of 

investigation of an airborne gamma-ray spectrometer: Journal 

of Geophysical Research, v. 76, p. 8466-8470. 

Gaertner, J., 1987, Commonwealth of Pennsylvania radon monitoring program, in Radon and the Environment Conference, 

1986, Proceedings: Mahwah, Ramapo College of New Jersey, p. 367-373. 

Use of Aerial Gamma-Ray Data to Estimate Radon in Soil Gas 161 
Gerusky, T., 1987, The Pennsylvania radon story: Journal of 

Environmental Health, v. 49, p. 197-200. 

Gunderson, L.C.S., Reimer, G.M., Wiggs, C.R., and Rice, 

C.A., 1988, Map showing radon potential of rocks and soils 

in Montgomery County, Maryland: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-2043, scale 1:62,500. 

Hahn. 0., 1936, Applied radiochemistry: Ithaca, N.Y., Cornell 

University Press, 278 p. 

Lewis, J.V., and Kummel, H.B., 1912, Geologic map of New 

Jersey [revised by H.B. Kummel, 1931, and M.E. Johnson, 

1950]: New Jersey Department of Conservation and Economic Development, Atlas Sheet No. 40, scale 1:250,000. 

Morozova, N.G., and Mukhraneli, I.A., 1971, Soil emanation as 

a function of the moisture content: Soviet Soil Science, v. 3, 

p. 583-588. 

New Jersey Department of Environmental Protection, 1987, Overview of initial results of statewide scientific study of radon: 

New Jersey Department of Environmental Protection Press 

Release, September 10, 1987. 

Otton, J.K., Schumann, R.R., Owen, D.E., Thurman, N., and 

Duval, J. S., 1988, Map showing radon potential of rocks and 

soils in Fairfax County, Virginia: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-2047, scale 1:48,000. 

Pitkin, J.A., and Duval, J.S., 1980, Design parameters for aerial 

gamma-ray surveys: Geophysics, v. 45, no. 9, p. 1427-1439. 

Schery, S.D., Gaeddert, D.H., and Wilkening, M.H., 1984, 

Factors affecting exhalation of radon from a gravelly sandy 

loam: Journal of Geophysical Research, v. 89, p. 7299-7309. 

Starik, I.Ye., and Melikova, O.S., 1957, Emanating power of 

minerals: Radiyevyy Institut imeni V. G. Khlopina Trudy, v. 

5, p. 184-202 (English translation, U.S. Atomic Energy 

Commission Report AEC-tr-4498, p. 206-226). 

Tanner, A.B., 1964, Radon migration in the ground: A review, in 

Adams, J.A.S., and Lowder, W.M., eds., The natural 

162 Field Studies of Radon in Rocks, Soils, and Water 

radiation environment: University of Chicago Press, p. 

161-190. 

---1980, Radon migration in the ground: A supplementary 

review, in Gesell, T.F., and Lowder, W.M., eds., Natural 

radiation environment III: Springfield, Va., National Technical Information Service, U.S. Department of Energy 

Report CONF-780422, v. 1, p. 5-56. 

---1988, Measurement of radon availability from soil, in 

Marikos, M.A., and Hansman, R.H., eds., Geologic Causes 

of Natural Radionuclide Anomalies, Proceedings of the 

GEORAD Conference, St. Louis, Mo., April 21-22, 1987: 

Missouri Department of Natural Resources Special Publication 4, p. 139-146. 

U.S. Department of Energy, 1978a, NURE aerial gamma-ray and 

magnetic reconnaissance survey Thorpe area, Scranton 

NK18-8 Quadrangle: U.S. Department of Energy Open-File 

Report GJBX-32(78), 2 v. 

---1978b, NURE aerial gamma-ray and magnetic reconnaissance survey Thorpe area, Newark NK18-11 Quadrangle: 

U.S. Department of Energy Open-File Report GJBX-16(78), 

2 v. 

---1980a, Aerial radiometric and magnetic survey, Salisbury 

national topographic map, New Jersey, Delaware, Maryland: 

U.S. Department of Energy Open-File Report GJBX-37(80), 

91 p. 

---1980b, Aerial radiometric and magnetic survey, Salisbury 

national topographic map, Delaware, Maryland, New Jersey, 

Pennsylvania: U.S. Department of Energy Open-File Report 

GJBX-68(80), 115 p. 

Webring, M., 1981, MINC: A gridding program based on 

minimum curvature: U.S. Geological Survey Open-File 

Report 81-1224, 41 p. 

Wilson, C., 1987, Radon -Geological aspects of an environmental problem: The Amateur Geologist, v. 11, no. 2, p. 17-33. 
REGIONAL RADON CHARACTERIZATIONS 

R. Thomas Peake1 and R. Randall Schumann2 

Abstract 

Indoor radon is a potential health threat in a significant number of homes across the United States. Twentyone percent of the homes tested in the 1986-87 Environmental Protection Agency/State Indoor Radon Survey of 10 

States contained screening indoor radon levels greater 

than the Environmental Protection Agency's recommended action level of 4 picocuries per liter. However, 

the distribution of indoor radon screening levels, and, 

therefore, the potential health risk, is not uniform everywhere. These differences are related to geology and 

house construction. 

Characterizations of radon potential can be made by 

use of geologic, soil, and radiometric data. National Uranium Resource Evaluation equivalent uranium concentrations of 2.0 parts per million or greater indicate areas that 

have the potential to produce a substantial number of 

elevated indoor radon levels. Equivalent uranium concentrations less than 1 part per million may indicate low radon 

potential. Soil permeability greater than 6.0 inches per 

hour may increase the radon potential of an area, except 

in cases where soil radium concentrations are very low. 

INTRODUCTION 

Almost every State has some homes that contain 

radon levels greater than 4 pCi/L (picocuries per liter) (Alter 

and Oswald, 1987). Nero and others (1986) estimated that 

an annual indoor radon average for the United States is 1.5 

pCi/L and that 7 percent of the homes in the United States, 

or approximately 5 million single family homes, may have 

annual averages above 4 pCi/L. These may be underestimates because the Nero distribution did not account for the 

large number of radon concentrations that have been found 

above 20 pCi/L (Napolitano and others, 1988). Twenty-one 

percent of the homes sampled in 10 States during the 

1986-87 Environmental Protection Agency (EPA)/State 

Indoor Radon Survey were found to contain screening 

levels above 4 pCi/L (Ronca-Battista and others, 1988). A 

screening measurement is defined as a short-term (2-3 day) 

radon measurement made in the lowest livable area in the 

the house (EPA, 1986). By definition, therefore, screening 

measurements are made in basements or on the first floor of 

homes that do not have basements. 

The distribution of indoor radon levels is not uniform 

across the country. On a regional scale, the percentage of 

homes having screening levels above 4 pCi/L is an indicator 

of the differing radon potential. In the 1986-87 EP NState 

1

Environmental Protection Agency, Washington, D.C. 2

U.S. Geological Survey. 

Indoor Radon Survey, fewer than 10 percent of the homes 

sampled in Alabama and Michigan were found to contain 

screening radon levels above 4 pCi/L. In contrast, 26 

percent of the homes sampled in Wyoming were found to 

have screening indoor radon concentrations greater than 4 

pCi/L. These differences may be related to regional geology 

and differences in house construction characteristics. 

Preliminary radon characterizations can aid in the 

planning of regional indoor radon testing programs or in 

allocating resources to those areas that have the most severe 

radon problem. This paper describes the concepts and 

methods used for preliminary regional radon characterizations and discusses the results of comparisons between 

geologic and indoor radon data. The views presented in this 

paper do not necessarily reflect formal EPA policy. 

FACTORS CONTROLLING RADON 

CONCENTRATIONS IN SOILS 

Radon-222 e22Rn) is produced from the radioactive 

decay of radium-226 e26Ra). Other isotopes of radon occur 

naturally, but they are of lesser importance in terms of 

indoor radon risk because of their short half-lives and 

uncommon occurrence. In general, the concentration and 

mobility of radon in a soil are dependent on several factors, 

the most important of which are the concentration of radium 

in the soil and the soil's permeability. Soil moisture 

conditions, presence and types of soil structures, and 

weathering profile characteristics also influence radon 

availability. 

Although there are few data on background levels of 

soil radium in the United States, a reasonable estimate for 

surface soils is less than 1 pCi/g (picocurie per gram) 

(Myrick and others, 1983; Sextro and others, 1987), which 

corresponds to 3 ppm (parts per million) uranium when 

uranium and radium are in secular equilibrium. Various 

equations (Bruno, 1983; Sextro and others, 1987) and 

empirical data (Peake, unpub. data, 1988) indicate that at 1 

m (meter) below the soil surface, 1 pCi/g radium in natural 

soils can produce 700-1 ,400 pCi/L radon in soil gas. 

Typical concentrations of radon in natural soils may average 

approximately 900 pCi/L. 

High radium concentrations have been closely associated with high indoor radon levels in the United States. 

Examples include the "index" home in Boyertown, Pa. 

(indoor radon concentration of 2,600 pCi/L), and the 

"discovery" house in Clinton, N.J., where the radon concentration reached similar levels (2,200 pCi/L) before 

mitigation. The Boyertown home is situated on a shear zone 

containing as much as 50 ppm uranium (Gundersen and 

Regional Radon Characterizations 163 
others, 1988a). One soil sample collected near the "discovery" house contained 85 pCi/g radium, and a soil-gas radon 

sample at the same site had a concentration of 120,000 

pCi/L. Soil samples collected around 12 homes with elevated indoor radon levels in the Reading Prong in eastern 

Pennsylvania had a median radium concentration of 2.4 

pCi/g (Peake, 1988). The median radium concentration for 

soil samples collected by Gundersen and others (1988a) 

around other homes with elevated radon levels in the 

Reading Prong is also greater than 2 pCi/g. 

Radon transport in soils occurs by two processes, 

diffusion and convective flow (Tanner, 1964). Diffusion is 

the dominant radon transport process in soils of low 

permeability (generally less than 10-7 cm2 (square centimeters), or approximately 14.0 in/hr (inches per hour)), 

whereas convective transport processes tend to dominate in 

highly permeable soils (generally greater than 10-7 cm2

; 

Sextro and others, 1987). Highly permeable soils, such as 

those derived from glacial outwash and on eskers, have 

been associated with high indoor radon levels in Europe and 

in the United States (Akerblom and others, 1984; Sextro 

and others, 1987; Kunz and others, 1989). In areas of karst 

topography, high secondary porosity is postulated to 

increase soil permeability at depth to the extent that Soil 

Conservation Service (SCS) soil permeability data for the 

regolith may provide an incorrect estimate of radon availability. Solution cavities and caverns may provide routes for 

free movement of soil gas, especially when a building 

exerts pressure on the openings. In low-permeability soils, 

much of the radon decays before it is able to enter a 

structure because the radon's transport distance is limited. 

DRIVING FORCES AND BASEMENT VERSUS 

NONBASEMENT HOMES 

A driving force (negative pressure in the house 

relative to the soil) and entry points must exist for radon to 

enter a home from the soil. The negative pressure caused by 

furnace depressurization and the stack effect during cold 

winter months are common driving forces. Sump-pump 

holes and slab to foundation wall joints are common entry 

points. 

EP NState Indoor Radon Survey data indicate that 

homes with basements are more likely to have elevated 

indoor radon measurements than nonbasement homes 

(Ronca-Battista and others, 1988). The term "nonbasement" applies to slab-on-grade or crawl space construction. 

Two areas having the same geologic radon potential, one 

primarily with basement homes and the other primarily with 

nonbasement homes, would likely be characterized by two 

different radon frequency distributions because the measurements would be made on different floors. Basement 

homes generally have higher average indoor radon levels 

because basement homes provide more entry points for 

164 Field Studies of Radon in Rocks, Soils, and Water 

radon, commonly have a more pronounced stack effect, and 

typically exert more negative pressure on their foundations 

than nonbasement homes. Another important point, however, is that basement homes may tend to . have higher 

indoor radon levels simply because the measurement is 

made in the basement rather than on the main floor. In many 

cases, the main floors of homes with basements have radon 

levels similar to those on the main floors of nonbasement 

homes; the implication in those cases is that occupants of 

basement homes are at greater risk from radon exposure 

only if they spend a significant amount of time in their 

basements. Information on foundation types (fig. 62), 

organized by State, can be obtained from Sterling and 

others (1985) or from major builders or Realtor associations. 

ASSESSMENT SCALES 

The types of data used for assessments of radon 

potential are dependent in large part on the scale of the area 

being evaluated. Larger areas require less detail and provide 

more general estimates, because the resulting maps show 

areas in which homes are more or less likely to have 

elevated indoor radon levels, but such maps cannot be used 

to predict the radon levels accurately in individual homes. 

The main purpose of such a map is to serve as a planning 

guide for radon testing programs, but these maps have also 

been used as preliminary maps of hazard potential because 

they can often be compiled from existing geologic data. To 

predict an individual home site's indoor radon level 

accurately, on-site field testing must be done to provide 

information on the physical and chemical characteristics of 

the soil. In addition, data on the variability of each soil 

property must be collected. 

Understanding the variability of properties within 

units is more important when relatively small areas are 

evaluated. For example, although relatively minor variations in permeability within a soil unit may have little effect 

on the ranking of an area in a statewide or countywide 

evaluation, they may be critical to determining an individual home site's radon availability. State-sized areas and 

individual home sites are representative of the extremes of 

radon assessment scales; the intermediate scales may then 

be added to produce a list of typical assessment scales, as 

follows (Schumann, unpub. data, 1988): 

1. State 

2. County 

3. Bedrock/soil units 

4. Individual building sites (house construction characteristics) 

5. Macroscopic soil properties (permeability, soil profiles, 

meteorologic effects, radon transport processes) 

6. Molecular-scale properties of radon and soil particles 

(radon emanation processes) 
•• ·~ D 

No Data 80 100 

Figure 62. The percentage of homes having basements in the United States, by State (after Sterling and others, 1985). 

Homes that do not have basements are categorized as slab-on-grade or crawl space construction. 

As a general rule of thumb, it is necessary to 

understand processes and provide detail at two scales larger 

than the scale of the area to be assessed. To evaluate a 

State-sized area (category 1), one would need to evaluate 

the radon potential of individual bedrock and soil units 

within that area (category 3), whereas an evaluation of 

radon potential within a single rock or soil unit (category 3) 

would require additional information on the variability of 

physical and chemical properties of the bedrock and soil 

within the unit (category 5), as well as on house construction characteristics (category 4). In this report we discuss 

the methods and results of large-scale (State) characterizations of radon potential, such as those compiled for the 

EP NState Indoor Radon Survey, so the following discussions will focus on elements of evaluations at this scale. 

ASSESSMENT TECHNIQUES 

An assessment of geologic radon potential can be 

made from four main types of data: geologic (lithologic), 

radiometric, soil permeability, and available indoor radon 

data. These elements can be integrated to produce an 

estimate of radon potential. 

Indoor radon data are an important element of geologically based assessments of radon potential. Existing 

indoor radon data for an area of interest can give clues to the 

overall distribution of indoor radon concentrations and 

provide a basis for preliminary comparisons with geologic 

data. Possible sources of indoor radon data include local, 

State, and Federal agencies, power companies, private 

contractors, and the homeowners themselves. One example 

of a readily available summary of regional indoor radon 

information is a series of reports released quarterly by the 

Bonneville Power Administration for the Northwestern 

United States (U.S. Department of Energy, Bonneville 

Power Administration, 1988). When using data of this type, 

however, it is important to remember that the data set may 

not necessarily be statistically representative of the actual 

distribution of indoor radon levels in an area. Volunteers are 

often motivated to test their homes when they are aware of 

other homes in the area that have elevated radon levels 

(Ronca-Battista and others, 1988). Another problem with 

many indoor radon data sets is that the data points may be 

only generally located (by Zip Code, for example), so that 

direct comparisons of indoor radon values of homes with 

their underlying geology may be difficult. 

Regional Radon Characterizations 165 
Information on the type and distribution of lithologic 

units and other geologic features in an assessment area is of 

primary importance. The most common radon source rocks 

include many granitic and metamorphic rocks, black shales, 

phosphatic rocks, and some carbonate rocks. Granitic rocks 

commonly concentrate uranium in specific minerals during 

initial crystallization; uranium in metamorphic rocks has 

typically been remobilized and concentrated by heat, pressure, and fluid migration during metamorphism. The 

organic compounds in black shales are natural concentrators 

of uranium and other metals; phosphates also provide 

favorable chemical conditions for concentrating uranium 

and radium. Although carbonate bedrock is generally low in 

radium, areas underlain by carbonates can generate elevated 

indoor radon concentrations. One reason may be that soils 

formed from carbonate bedrock tend to be enriched in 

uranium during weathering (Kukoc, 1980; Rose and others, 

1988). Some continental sandstones contain localized 

deposits of uranium ("roll front" deposits, for example) that 

may generate locally elevated concentrations of radon in 

soil gas. Although many cases of elevated indoor radon 

levels can be traced to high radium and (or) uranium 

concentrations in parent rocks, some structural features, 

most notably faults and shear zones, have been identified as 

sites of localized uranium concentrations and have been 

associated with some of the highest known indoor radon 

levels (Deffeyes and MacGregor, 1980; Gundersen and 

others, 1988a,b; Gundersen, this volume). Investigating 

faults and shear zones is an important, but often overlooked, part of the preliminary characterization process, 

because in favorable geochemical settings, they can be 

likely sources of radon "hot spots." 

Aerial radiometric data are used to describe the 

radioactivity of rocks and soils. Although radiometric data 

usually comprise spectral as well as total-count gamma-ray 

data, equivalent uranium (eU) data are typically used for 

radon characterizations because they provide an estimate of 

the surficial concentrations of radon parent materials (uranium, radium) in rocks and soils. Equivalent uranium is 

calculated from the counts received by the gamma-ray 

detector in the wavelength corresponding to bismuth-214 

e14Bi), with the assumption that uranium and its daughters 

are in secular equilibrium. The primary source of aerial 

radiometric data in the United States is reports of the 

National Uranium Resource Evaluation (NURE) program of 

the 1970's and early 1980's. The purpose of the NURE 

program was to identify and describe areas in the United 

States having potential uranium resources (U.S. Department of Energy, 1976). Hill ( 1986) lists aerial radioactivity 

and aerial magnetic data available for the United States. 

Ground-based radiometric data have also been used for 

preliminary assessments in some areas (Cannia and Case, 

1986; Pennsylvania Topographic and Geological Survey, 

1985). In this discussion we will focus primarily on the use 

of NURE aerial radiometric data for area characterizations. 

166 Field Studies of Radon in Rocks, Soils, and Water 

Use of NURE Data for Radon Characterizations 

Although radon is highly mobile in soil, and its 

concentration is affected by meteorologic conditions 

(Kovach, 1945; Jaacks, 1984; Schery and others, 1984; 

Schumann and others, 1989), a relatively good correlation 

between average soil-gas radon concentrations and average 

eU values for some soils has been noted (Gundersen and 

others, 1988b; Schumann and Owen, 1988). Aerial radiometric data can provide an estimate of radon source strength 

over a region, but the amount of radon that is able to enter 

a home from the soil is dependent on several additional 

factors, including soil structure, grain size distribution, 

moisture content, and permeability, as well as type of house 

construction and structural condition, and these factors must 

also be considered when using radioactivity data for radon 

characterizations. 

The types of data in, and the presentation format of, 

NURE reports are variable, depending on the contractor that 

performed the survey. The data are presented in 1 ox 2° 

format and include graphs of the flight-line data, uranium 

anomaly maps, standard deviation maps, and histograms of 

the radiometric data grouped by lithology. In addition, 

many NURE quadrangle reports also include pseudocontour 

maps of the spectral gamma-ray data; some reports include 

maps of known uranium occurrences and rocks having 

favorable uranium potential. 

NURE aerial radiometric data are best used for 

characterizing large areas such as a State or region (Peake, 

1988) because of the relatively wide spacing between 

adjacent flight lines. The primary NURE flight lines are 

oriented east-west and are generally spaced 3 mi (miles) 

apart in the Western United States and 6 mi apart in the 

Eastern United States. With this flight-line spacing, a large 

unmeasured area exists between flight lines. This may be 

less important when data from several flight lines, covering 

a large area of relatively uniform geology, are integrated; 

however, localized anomalies may be overlooked. For 

example, the uranium anomaly underlying homes that have 

the highest indoor radon values in the Boyertown, Pa., area 

was not shown in the NURE reports because it is relatively 

small and located between flight lines; however, the entire 

Reading Prong displays an elevated 214Bi signature. 

The shallow (20-25 em) depth of investigation of 

gamma-ray spectrometers, either ground-based or airborne 

(Duval and others, 1971; Durrance, 1986), suggests that 

gamma-ray data may sometimes provide an underestimate 

of radon source strength, especially in soils with deep 

weathering profiles or where the surficial materials are 

derived from a different source than the underlying bedrock 

(for example, transported soils). As a soil weathers, some 

minerals in the near-surface soil layers are leached and 

moved downward in the soil profile, where they may be 

concentrated in the B horizon, whereas the concentration of 

radionuclides in the C horizon and below may be relatively 
unaffected. In these cases the surface gamma-ray signal 

indicates a lower radon source concentration than actually 

exists in the deeper soil layers. Therefore, soil profile data 

should be considered and correlated with radioactivity data 

whenever possible. Schumann and Owen (1988) describe 

an example of relatively high soil-gas radon concentrations 

generated by a soil derived from a weathered granite with 

low surface radioactivity in Fairfax County, Va. 

The initial phase of a regional evaluation begins by 

selecting the type of NURE data to be used-flight -line 

data, anomaly maps, standard deviation maps, or pseudocontour maps-and comparing them with geologic maps. 

NURE aerial radiometric data are typically presented in the 

1°X2° format reduced to a scale of 1:500,000, which 

corresponds to, or is easily converted to, the scale of many 

State geologic maps. Correlations between eU signatures 

and outcrop patterns of geologic units should be noted, as 

well as any anomalies corresponding to structural features 

such as faults or shear zones. Areas with less than 1.0 ppm 

eU are delineated and assigned a low radon potential, those 

with 1.0 to 2.0 ppm eU are assigned a moderate potential, 

and areas with greater than 2.0 ppm eU are designated areas 

of high radon potential. These rankings may be modified 

later as soil permeability data are integrated and compared; 

low soil permeability generally reduces the radon risk, 

whereas high permeability increases the radon risk. Pseudocontour maps of eU may often be used without modification, except for adjustments between adjacent or nearby 

quadrangles for contractor differences or other inconsistencies. These maps provide a quick and easy preliminary 

method for determining the radon potential of an area or 

region but are less detailed than maps interpreted from 

flight-line anomaly maps, standard deviation maps, or 

flight-line data because of the data smoothing that is 

performed as part of the contouring process. An alternate 

method involves calculating a weighted mean eU value for 

a 1° x 2° quadrangle by using the median eU values from the 

histogram data and weighting them by the number of 

adequate samples for each lithologic unit. This method 

provides an average eU value for the quadrangle that can be 

used for comparison with eU values in other quadrangles. 

Use of SCS Soil Survey Data 

Soil surveys prepared by the Soil Conservation Service (SCS) provide data on soil characteristics, including 

soil cover thickness, grain size distributions, permeability, 

shrink-swell potential, typical vegetative cover, generalized 

ground water characteristics, and land use. The reports are 

typically available in State and county formats and usually 

contain both generalized and relatively detailed maps of 

soils in the area. Quantitative soil characteristics are presented in tables following descriptions of the physiography, 

geology, climate, and soils of the area. 

For regional-scale radon characterizations, a generalized soil map should be compared to a geologic map of the 

area, and the soil descriptions, shrink-swell potential, and 

permeability of each soil group should be noted. The 

permeabilities listed in the SCS surveys are for water, but 

they are generally related to gas permeability. Permeabilities reported by the SCS as greater than 6.0 in/hr may be 

considered high and may increase the radon potential of 

areas with low to moderate radium concentrations (less than 

2.0 ppm eU). In contrast, permeabilities less than 0.6 in/hr 

may be considered low in terms of soil-gas transport. Soils 

with permeabilities in this range may have a lower radon 

potential than more permeable soils with similar eU concentrations. 

Soil permeability is generally highest near the surface 

and decreases with depth. Many well-developed soils contain a clay-rich B horizon that may impede vertical soil-gas 

transport. Radon generated below this horizon cannot 

readily escape to the surface, so it would instead tend to 

move laterally, especially under the influence of a negative 

pressure exerted by a structure. Soil permeability data and 

weathering profiles thus provide important information for 

regional radon assessments. Depth to water table can also 

be an important parameter to consider in some areas. 

Because water in soil pores inhibits gas transport, the 

amount of radon available to a home is effectively reduced 

by a high water table. Areas likely to experience effects of 

high water tables are river valleys, coastal areas, and some 

areas overlain by deposits of glacial origin (for example, 

loess). 

Shrink-swell potential is an indicator of the abundance of smectitic (swelling) clays in a soil. Soils with a 

high shrink-swell potential may cause building foundations 

to crack and thus create pathways for radon entry into the 

structure. In addition, swelling soils often crack as they dry; 

as a result, they provide additional pathways for soil-gas 

transport and effectively increase the gas permeability of the 

soil (Schumann and others, 1989). 

CORRELATIONS BETWEEN EQUIVALENT 

URANIUM AND INDOOR RADON DATA 

Nine 1 ox 2° quadrangles exhibiting high and low 

radioactivities in geologically and geographically diverse 

regions of the United States were selected to illustrate the 

relation between indoor radon measurement data and eU 

concentrations (table 20). The quadrangles were selected on 

the basis of available NURE, soil, and randomly collected 

indoor radon data. The EPA/State Indoor Radon Survey 

was the primary source of indoor radon data. Data from 

counties within each of the areas were combined and 

grouped by house type (basement versus nonbasement) for 

comparisons with geologic and soil data. Indoor radon data 

for Florida were obtained from the report of Florida's State 

Regional Radon Characterizations 167 
Table 20. Equivalent uranium (eU), soil permeability, housing construction, and indoor radon data for nine areas 

sampled during the 1986-87 EPNState Indoor Radon Survey. 

[ppm, parts per million; in/hr, inches per hour; pCi/L, picocuries per liter; N/A not applicable] 

Weighted Typical soil Percent of Area mean permeability homes with NURE eU 

(ppm) (in/hr) basements 

Southern Alabama ...... 1.5 0.2-2.0 1 

Eastern Kentucky ....... 1.8 2.0-5.0 N/A 

North-central Kentucky 2.5 .6-2.0 48 

Southeastern Colorado .. 2.8 .6-20.0 24 

Denver metro area ...... 3.2 .02-20.0 83 

Central Michigan ....... 1.2 .6-20.0 86 

Southern Michigan ...... 1.2 .6-20.0 100 

N.J. Outer Coastal Plain . 1.0 <.2 to >6.0 64 

Florida ................. 1.1 .6-6.0 N/A 

indoor radon survey (Geomet Technologies, Inc., 1987). 

The indoor radon data for New Jersey were obtained from a 

radon survey conducted by the State of New Jersey (Karl 

Muessig, personal commun., 1988). Each of the surveys 

used randomly collected charcoal-based screening measurements. 

Average eU values were determined for each area by 

calculating weighted means from the histogram data in the 

NURE folios for the appropriate 1 °X2° quadrangles. Equivalent uranium values for only those rock types actually 

exposed in the area were used to determine the average eU 

values. If the area was covered by more than one 1 oX 2° 

quadrangle, the eU data from all quadrangles covering the 

area were combined to determine the average eU value. The 

NURE data for the State of Florida were derived from a 

summary of average eU concentrations listed by county. 

The New Jersey NURE data were obtained from an unpublished compilation of NURE aerial radiometric data for the 

mid-Atlantic States (J.S. Duval, written commun., 1988). 

A plot of indoor radon and eU data from the nine 

study areas (fig. 63) shows a positive relation between eU 

concentrations and average screening indoor radon levels in 

basement and non basement homes. Each data point represents an average radon level for a group of counties and the 

corresponding NURE eU average. Given the same regional 

eU concentration, basement construction is associated with 

higher screening levels than nonbasement construction. The 

slope of the line for the basement population is steeper than 

that of the nonbasement population by a factor of approximately two. One part per million eU is associated with a 

screening measurement of about 1 pCi/L in living areas and 

about 2 pCi/L in basements. In areas where the surface eU 

concentration is below about 1 ppm, nonbasement homes 

should contain little radon. A similar correlation is seen in 

the Pacific Northwest (Duval and others, 1989). A corre168 Field Studies of Radon in Rocks, Soils, and Water 

Basement Nonbasement 

Radon Percent Number Radon Percent Number 

average >4 pCi/l of samples average >4 pCi/l of samples (pCi/l) (pCi/l) 

1.0 0 0.8 1 83 

N/A N/A N/A 1.3 3 100 

6.3 53 64 3.2 27 70 

6.5 62 21 2.5 15 65 

5.6 60 67 3.0 21 14 

1.5 8 12 N/A 0 2 

3.2 38 16 N/A N/A 0 

1.7 7 164 .9 1 90 

N/A N/A N/A .7 3 3,050 

7 

• Basements • 6 0 Nonbasements 

....1 • 

(3 - 5 

Y=-0.2+2.2x 

a. R=0.90 

c 

a: 4 ..... 

0 

0 

"C • c: 3 Q) 

0') 

cu 

..... 2 Q) 

~ 

0 

0 2 3 4 

eU, ppm 

Figure 63. Average equivalent uranium (eU) concentrations versus basement and nonbasement indoor radon 

averages for nine areas sampled during the 1986-87 

EPNState Indoor Radon Survey. Data from table 20. ppm, 

parts per million; pCi/L, picocuries per liter. 

sponding minimum level for basement homes may be even 

lower, but there are few natural soils with radium concentrations lower than 1 ppm. 

A CASE STUDY 

The EPA/State Indoor Radon Survey of Kentucky 

provides an illustrative example of characterization of 

geologic radon potential. Because the initial indoor radon 

survey in Kentucky has been completed, the geologic data 

can be compared with preliminary indoor radon data to 

illustrate the relation between geology and indoor radon 

concentrations. 
HOLOCENE ALLUVIUM 

QUATERNARY AND TERTIARY 

sand, silt, clay, loess 

A 

N 

CRETACEOUS 0 20 40 60 80 mi 

sandstone, siltstone, conglomerate 

PENNSYLVANIAN 

I I I ~ I 

I I I I 1 

0 20 40 60 80 1 00 km 

sandstone, siltstone, shale 

MISSISSIPPIAN 

marine shale, sandstone, limestone 

DEVONIAN and SILURIAN 

black shale, shale, dolomite, limestone 

ORDOVICIAN 

limestone, shale 

ORDOVICIAN 

Lexington Limestone 

Figure 64. Generalized geologic map of Kentucky (after Winsor and Bailey, 1963). 

The geology (fig. 64), physiography (fig. 65), soils 

(fig. 66), and surface radioactivity (fig. 67) of Kentucky are 

interrelated, with bedrock geology as the dominant controlling factor. A geologic map of Kentucky (McDowell and 

others, 1981; fig. 64 is a generalized version) was examined 

to identify rock types and geologic features suspected of 

producing elevated radon levels. Three primary areas were 

identified: ( 1) areas underlain by Devonian black shales in 

the Outer Bluegrass region (figs. 64, 65); (2) areas underlain by the Ordovician Lexington Limestone (some of 

which is phosphatic) in the Inner Bluegrass region (figs. 64, 

65); and (3) areas underlain by, or close to, major faults in 

the Western Coalfield and Inner Bluegrass regions (fig. 65; 

McDowell and others, 1981). The black shale and limestone areas have associated high surface radioactivity, and 

the Western Coalfield contains scattered radioactivity 

anomalies (fig. 67). In addition, generally elevated surface 

radioactivity is associated with Ordovician limestones and 

shales in the northern part of the Outer Bluegrass region 

(figs. 64, 65). The arcuate pattern of radioactivity anomalies along the southern edge of the Outer Bluegrass region 

(figs. 65, 67) corresponds closely to the outcrop pattern of 

the Devonian Chattanooga Shale (fig. 64). A large radiometric anomaly along the State's southern border (fig. 67) 

roughly follows the outcrop pattern of the Upper Mississippian Ste. Genevieve and St. Louis Limestones (McDowell 

and others, 1981). The clastic sedimentary rocks of the 

Cumberland Plateau region (figs. 64, 65) are generally 

characterized by relatively low surface radioactivity (fig. 

67). 

A generalized soil permeability map (fig. 66) was 

compiled from a soil association map (Winsor and Bailey, 

1963) and county soil surveys published by the SCS. The 

map shows that most soils in Kentucky are of low or 

moderate permeability. Some areas underlain by limestones 

may have increased permeability locally because solution 

cavities are present. Soils formed on the Lexington Limestone, in the Inner Bluegrass region, have a significantly 

higher permeability than soils in the surrounding Outer 

Bluegrass region (figs. 64-66). The Inner Bluegrass region 

has moderate to high radon potential because it has elevated 

surface radioactivity and moderate soil permeability. 

Although high surface radioactivity is also characteristic of 

the Outer Bluegrass region, it has a low to moderate radon 

potential because of the low permeability of the soils 

formed on the shales and limestones (figs. 64, 66, 67). The 

Cumberland Plateau and Jackson Purchase areas (fig. 65) 

Regional Radon Characterizations 169 
A 

N 

0 20 40 60 80 mi I I I ~ I I I I I I 

0 20 40 60 80 100 km 

Figure 65. Generalized map of major physiographic provinces of Kentucky (after McDowell and others, 1981). 

D LOW (<0.6 in/hr) A ~ LOWTOMODERATE N 

~~~ MODERATE (0.6-6.0 in/hr) 

0 20 40 60 80mi I I I I I I I I I I 

0 20 40 60 80 1 00 km 

Figure 66. Generalized soil permeability map of Kentucky (after Winsor and Bailey, 1963). "Low to moderate" indicates 

that the area contains mixed soils, some soils with low permeability and some with moderate permeability. 

generally have low radon potential. The Western Kentucky 

Coalfield (fig. 65) has low to moderate radon potential 

because few homes are situated directly on faults. In 

addition, soils in the Western Coalfield are of low to 

moderate permeability and only scattered radioactivity 

170 Field Studies of Radon in Rocks, Soils, and Water 

anomalies are found in this area. The western part of the 

Mississippian Plateau (fig. 65) has moderate radon potential, whereas the eastern part has generally low radon 

potential because of the distribution of gamma anomalies 

and the generally moderate soil permeability. 
A 

~~f~111[1[[[i[~~f~ AREA WITH > 3.0 ppm eU 

N 

0 20 40 60 80 mi 

I I I I I 

I I 1 I 1 

0 20 40 60 80 1 00 km 

Figure 67. Map showing areas of anomalous surface radioactivity (greater than 3.0 ppm equivalent uranium), compiled 

from NURE 1°X2° quadrangle reports for Kentucky and adjacent States. 

Table 21 presents a partial summary of results of the 

EPA/State Indoor Radon Survey of Kentucky conducted 

during the 1986-87 winter season. The areal distribution of 

these screening indoor radon levels is shown in figure 68. 

For the purposes of this discussion, only data from those 

counties in which five or more measurements were made for 

one floor are presented here. EPA's indoor radon measurement protocol (EPA, 1986) calls for screening measurements to be made in the lowest livable area in the home. 

Because of this, the data set contains measurements from 

both basements and main floors of homes that, although 

effective for estimating "worst-case" radon risk in individual homes, is not well suited for statistical analysis because 

data from different floors are not directly comparable. To 

compensate, ratios between average basement and main 

floor indoor radon levels were calculated for each county 

containing adequate numbers of measurements from both 

floors (table 21). Because basement radon levels average 

approximately twice as high as main-floor levels (table 21), 

main-floor indoor radon averages were multiplied by two to 

obtain estimates of average basement indoor radon levels in 

those counties that had an insufficient number (less than 

five) of basement measurements. These estimated average 

basement radon levels are shown in addition to actual 

measured basement radon averages on the indoor radon map 

of Kentucky (fig. 68). 

The distribution of indoor radon levels (fig. 68) 

correlates with the underlying geology in Kentucky. Elevated indoor radon levels occur in the Inner Bluegrass 

region (figs. 65, 68) and in those homes underlain by the 

Chattanooga Shale, although this conclusion is based only 

on data from homes in the western part of the black-shale 

outcrop area. Although some homes with elevated levels 

were found in the northern Outer Bluegrass region, the 

number is less than would be expected on the basis of eU 

(fig. 67), likely because the soil permeability is low (fig. 

66). Homes in the western part of the State have generally 

low indoor radon levels, although the eU data suggest that 

the indoor radon average should be about 2. 5 times the 0. 9 

pCi/L average for the area. The poor correspondence with 

surface radioactivity in western Kentucky appears to be due 

primarily to a combination of low soil permeability and high 

water tables. Western Kentucky was the only part of the 

State in which seasonal high water tables were consistently 

listed in the SCS soil surveys as less than 6 ft, and 

commonly less than 2 ft. The two counties in the southcentral part of the State having average indoor radon levels 

greater than 10 pCi/L (fig. 68) appear to correspond to the 

surface radiometric anomaly associated with the outcrop of 

the Ste. Genevieve and St. Louis Limestones (fig. 67; 

McDowell and others, 1981). Homes in the Cumberland 

Plateau region (fig. 65), which has a generally low radiometric signature (fig. 67), have correspondingly low average indoor radon levels (fig. 68). 

DISCUSSION 

These examples indicate that surface radioactivity 

and indoor radon levels correlate notably. Soil permeability 

and moisture conditions can enhance or reduce the radon 

Regional Radon Characterizations 171 
Table 21. Average screening indoor radon levels, number of homes tested, and percent greater than 4 picocuries per liter 

for 40 counties in Kentucky 

[Measurements were made during the 1986-87 EPA/State Indoor Radon Survey; only data from those counties in which five or more measurements were 

made on one floor are listed] 

Non basement Basement Ratio of 

basement! County Average Number of Percent Average Number Percent non basement 

radon homes > 4 pCi/L radon of homes > 4 pCi/L radon 

Ballard ............. 0.8 8 0 

Barren .............. 1.1 5 0 

Boone ·············· Bourbon ............ 

Boyd .... ··········· .6 5 0 

Bull itt .............. 

Butler ...... ········ .7 12 0 

Caldwell ............ 1.3 5 0 

Calloway ........... .9 6 0 

Campbell .... ······· Christian ............ 1.4 15 13 

Daviess ············· .8 14 0 

Fayette ............. 5.0 23 43 

Franklin . ··········· Graves .............. .8 9 0 

Grayson ... ······ ... Greenup ······ ...... 2.1 6 17 

Hardin .............. 1.5 14 7 

Harrison ............ .6 5 0 

Hart ................ 

Henderson .......... 1.3 6 0 

Hopkins ············ .4 6 0 

Jefferson ............ 1.5 33 9 

Jessamine ........... 2.0 8 13 

Kenton ............. 2.1 9 11 

Logan .............. 1.1 5 0 

McCracken .......... .8 13 0 

Marshall ............ .6 7 0 

Mason ········· ..... Morgan ............. .7 5 0 

Nelson .............. 2.2 7 14 

Pendleton ........... 

Pike ................ 1.6 8 0 

Pulaski ............. 

Simpson .... ········ 1.1 5 0 

Todd ............... 1.3 5 0 

Union ······· ....... .4 5 0 

Warren ............. 5.8 18 61 

Whitley ............. .9 5 0 

Woodford ........... 3.0 5 20 

Average .......... 1.5 9 7 

potential of an area. Because an estimate of geologic radon 

potential (GRP) is composed of two main components, the 

concepts discussed here may be summarized by a twodimensional diagram (fig. 69). Thus, to estimate the GRP 

of an area, eU should be compared with soil permeability, 

and the field encompassing the intersection of these values 

(low, moderate, or high; fig. 69) is the estimated GRP for 

172 Field Studies of Radon in Rocks, Soils, and Water 

1.4 6 0 

10.1 7 71 

1.7 12 8 2.89 

12.6 10 60 

1.6 14 14 

1.6 6 0 1.92 

7.5 17 65 1.51 

5.0 11 55 

1.1 5 0 

2.0 5 20 .94 

2.1 12 8 1.38 

11.6 5 100 

3.7 65 31 2.43 

6.2 3 33 3.20 

1.1 23 0 .54 

1.4 5 0 

6.0 6 67 2.68 

5.4 5 60 

4.1 5 60 

16.1 5 80 2.78 

5.1 11 37 2.03 

the area. As was previously discussed, other soil and 

geologic features such as faults, high water tables, and 

weathering profiles should also be considered to estimate 

additional effects on soil-gas radon concentrations. 

The GRP yields an estimate of radon source strength 

based on radiometric, geologic, and soil permeability data, 

but it will not necessarily provide an estimate of the 
D NODATA 

I::::It,I] 0-4 pCi/L 

~ 4-lOpCi/L 

• > lOpCi/L 

0 20 40 60 80 m i 

I I I I I 

I I 1 I 1 

0 20 40 60 80 100 km 

A 

N 

Figure 68. Average basement screening indoor radon levels by county. Data are from the 1986-87 EPNState indoor 

Radon Survey of Kentucky. Only those counties in which 

five or more indoor radon measurements were taken on 

one floor (basement or main floor) are shown. Where 

GEOLOGIC RADON POTENTIAL 

~ 6.0 

~ :E 

t1:S 

§ 

<1.) 

0.. 0.6 -·a 

(/.) 

0 2 3+ 

eU,ppm 

Figure 69. Diagram of geologic radon potential. eU, equivalent uranium; ppm, parts per million; in/hr, inches per 

hour. 

percentage of screening measurements above 4 pCi/L in an 

area, because the radon concentration in a house is controlled by both geologic and house construction factors: 

geology indicates the potential for a problem to exist, 

basement averages were not available, main-floor averages were multiplied by two to provide estimated basement values (see table 21 for a list of county data included 

on this map). 

whereas the house construction determines in part how the 

geologic potential will be realized in terms of indoor radon 

levels. As an estimate of expected indoor radon levels 

(rather than a direct estimate of radon risk), the integrated 

radon potential (IRP) concept takes the geologic radon 

potential estimate one step further by incorporating the GRP 

with house construction characteristics to better estimate the 

percentage of homes having indoor radon concentrations 

greater than 4 pCi/L in an area. Because the population of 

nonbasement homes has an average indoor radon concentration lower than that of the population of basement homes, 

the IRP for nonbasement homes would necessarily be less 

than for basement homes in an area that had the same 

geologic radon potential. An IRP diagram would look 

similar to the GRP diagram but would plot the previously 

estimated GRP against the percentage of homes with 

basements in the area. Although the IRP provides a useful 

conceptual framework for estimating indoor radon levels, 

there are currently insufficient data for determining cutoff 

points for such a diagram. The GRP and IRP concepts are 

best applied to large areas such as a State or region and may 

also be applicable to county-sized areas. Many additional 

details and data are required for radon potential estimates of 

smaller areas. 

Regional Radon Characterizations 1 73 
SUMMARY AND CONCLUSIONS 

The purpose of a regional radon characterization is to 

identify areas of high radon potential. Existing information 

can be used to characterize areas quickly and can provide 

direction to more specific follow-up studies that may be 

able to identify localized "hot spots." A regional radon 

characterization serves as the first estimate of potential 

indoor radon risk within a State or other large region. Once 

high-risk areas are identified, health officials can allocate 

resources in areas where the radon risk is the greatest. 

Regional geologic, soil, and house construction 

characteristics appear to strongly influence screening indoor 

radon frequency distributions. NURE eU concentrations of 

more than 2.0 ppm indicate high radon potential; however, 

whether or not a home has a basement has a significant 

effect on screening indoor radon levels and should be 

incorporated in analyses of indoor radon and geologic data. 

In addition, soil permeability and other properties can alter 

the relationship between eU and indoor radon levels by a 

factor of two or more; this may be especially significant in 

areas underlain by glacial soils. Because eU data correlate 

relatively well with average indoor radon concentrations, 

and indoor radon averages are correlated with the 

percentage of homes that have radon levels greater than 4 

pCi/L, eU can be used to estimate the percentage of homes 

expected to contain greater than 4 pCi/L radon. 

The concepts of geologic radon potential and 

integrated radon potential may provide a useful approach to 

separating and comparing geologic and house construction 

effects for indoor radon predictions and data analyses. The 

suggested guidelines are preliminary, but they may improve 

radon prediction capability as well as understanding of the 

distribution of indoor radon levels in the United States. 

REFERENCES CITED 

Akerblom, G., Anderson, P., and Clavensjo, B., 1984, Soil gas 

radon-A source for indoor radon daughters: Radiation 

Protection Dosimetry, v. 7, no. 1--4, p. 49-54. 

Alter, H. W., and Oswald, R.A., 1987, Nationwide distribution of 

indoor radon measurements: A preliminary data base: Journal 

of the Air Pollution Control Association, v. 37, p. 227-231. 

Bruno, R.C., 1983, Sources of indoor radon in houses: A review: 

Journal of the Air Pollution Control Association, v. 33, p. 

105-109. 

Cannia, J.C., and Case, J.C., 1986, Planning-guide map for radon 

studies in Wyoming: Wyoming Geological Survey Open-File 

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174 Field Studies of Radon in Rocks, Soils, and Water 

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Environmental Protection Agency, 1986, Interim protocols for 

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measurements: EPA Report 520/1-86-014, Office of 

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Gundersen, L.C.S., Reimer, G.M., and Agard, S.S., 1988a, 

Correlation between geology, radon in soil gas, and indoor 

radon in the Reading Prong, in Marikos, M. , Geologic 

Causes of Natural Radionuclide Anomalies: Missouri 

Department of Natural Resources Special Publication 4, p. 

91-102. 

Gundersen, L.C.S, Reimer, G.M., Wiggs, C.R., and Rice, C.A., 

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Montgomery County, Maryland: U.S. Geological Survey 

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Jaacks, J.A., 1984, Meteorological influence upon mercury, 

radon and helium soil gas emissions: Golden, Colo., 

Colorado School of Mines, unpublished Ph.D. thesis, 170 p. 

Kovach, E.M., 1945, Meteorological influences upon the radon 

content of soil gas: EOS, Transactions of the American 

Geophysical Union, v. 26, p. 241-248. 

Kukoc, A. H., 1980, Natural gamma-ray spectra of terra rossa soil 

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385-387. 

Kunz, C., Laymon, C.A., and Parker, C., 1989, Gravelly soils 

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Radon Reduction Technology, v. 1, Oral Presentations: 

Environmental Protection Agency Publication 600/9-89-

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1:250,000, 4 sheets. 

Myrick, T.E., Berven, B.A., and Haywood, F.F., 1983, 

Determination of concentration of selected radionuclides in 

surface soil in the U.S.: Health Physics, v. 45, p. 631-642. 

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the Reading Prong, eastern Pennsylvania, showing the 

locations of generalized gamma-ray anomalies detected by 

carborne survey: scale 1 :50,000. 

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Radiation Protection Dosimetry, v. 24, p. 307-312. 

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Variability of radon with depth and season in a central 

Pennsylvania soil developed on limestone: Northeastern 

Environmental Science, v. 7, no. 1, p. 35-39. 

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Factors affecting exhalation of radon from a gravelly sandy 

loam: Journal of Geophysical Research, v. 89, p. 7299-7309. 

Schumann, R.R., and Owen, D.E., 1988, Relationships between 

geology, equivalent uranium concentration, and radon in soil 

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American Chemical Society Symposium Series 331, p. 

10-29. 

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84-0024/ 1 . 

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Adams, J.A.S., and Lowder, W.M., eds., The Natural 

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U.S. Department of Energy, Bonneville Power Administration, 

1988, Radon monitoring results from BPA's residential 

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1988, 23 p. 

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Lexington, Ky., University of Kentucky, Agricultural 

Experimental Station Miscellaneous Report 204, 35 p. 

Regional Radon Characterizations 175 

RECONNAISSANCE APPROACH TO USING GEOLOGY AND SOIL-GAS RADON 

CONCENTRATIONS FOR MAKING RAPID AND PRELIMINARY ESTIMATES 

OF INDOOR RADON POTENTIAL 

G.M. Reimer, Linda C.S. Gundersen, S.L. Szarzi, and J.M. Been 

Abstract 

Soil-gas samples collected along a traverse in Prince 

Georges County, Md., were analyzed for radon. The 

traverse included principal lithologies and areas for which 

total count aeroradiometric measurements showed various intensities. Although this region in the Atlantic 

Coastal Plain might be considered to possess the type of 

geologic setting or aeroradiometric signature that would 

not contribute to significant radon potential, the measured soil-gas concentrations of up to 2,500 picocuries per 

liter indicate that the potential exists for indoor accumulations in excess of the level of 4 picocuries per liter 

established by the Environmental Protection Agency for 

remedial action. The higher levels of soil-gas radon were 

found in some of the Tertiary sediments, and lower 

concentrations occurred in Cretaceous and Quaternary 

sediments. Geologic relationships are thought to be the 

controlling factors for the radon soil-gas concentrations. 

The few data available from this survey suggest that a 

reconnaissance approach can be an effective screening 

method in the evaluation of areas for high radon potential. 

INTRODUCTION 

Radon, a radioactive gas that is a product of the decay 

of radium, has been found to accumulate in some homes at 

concentrations that are considered to pose a concern to 

public health (Environmental Protection Agency, 1986). 

Factors causing the gas to accumulate are numerous and 

include the manner of house construction and the concentration of radium in the soil or bedrock upon which the 

house is built. Radon, as a mobile gas, does not migrate 

very far from its radium parent because of its short half-life. 

Radium itself is derived from the radioactive decay of 

uranium or thorium, the concentration and distribution of 

which are strongly controlled by petrologic conditions 

during rock- and mineral-forming processes. Geology and 

soil chemistry are then dominant in controlling the surficial, 

natural distribution of uranium, thorium, and radium 

(Gabelman, 1977). Estimates of potential indoor radon 

accumulations would be very useful for assessment purposes in planned or existing residential areas. Preliminary 

surveys from areas known to have high indoor radon 

concentrations are providing a data base that can be used to 

derive the radon potential for an area. This study demonstrates how geology and soil-gas radon measurements can 

be combined in a reconnaissance survey to establish a data 

base for estimating the radon potential. 

GEOLOGIC SETTING 

Prince Georges County, Md., lies in the Atlantic 

Coastal Plain. In the region of this study, the underlying 

sediments are deltaic and marine in origin and consist of 

clay, sand, and gravel of Cretaceous, Tertiary, and Quaternary age. The sediments dip gently to the southeast, and the 

present-day drainage is toward the south-southeast. In 

general, the age of the exposed sediments increases toward 

the west. Figure 70 shows the location of samples on a 

geologic map for the county. No known faults intercept the 

surface, but Jacobeen (1972) has interpreted seismic evidence for high-angle reverse faulting at depth. 

Clean, silicious, non-organic marine sedimentary 

rocks have not been considered to be a source for high radon 

emanation, and, indeed, the natural radioactivity for this 

area is fairly low and without great contrast (Neuschel, 

1965) when compared to areas containing crystalline rocks, 

such as Montgomery County, located immediately to the 

west. Very few homes in Prince Georges County have been 

tested for indoor radon, and some exceed the level of 4 

pCi/L (picocuries per liter) established as a guideline for 

follow-up action by the Environmental Protection Agency 

(EPA). No indoor concentrations reported by the date of 

this study exceeded 40 pCi/L. 

ANALYTICAL TECHNIQUE 

The soil-gas collecting and analytical techniques were 

as described by Reimer and Bowles (1979) and Reimer (this 

volume) for making a rapid field assessment of soil-gas 

radon concentrations. Basically, the method consists of 

pounding a hollow steel probe into the ground to a depth of 

0.75 m (meter) and withdrawing a 10-cm3 (cubic centimeter) sample with a hypodermic syringe. The sample is then 

injected into an evacuated, phosphor-coated cell and 

counted with a portable alpha-particle scintillometer 

(Reimer, 1977). The analytical unit had been calibrated by 

using the U.S. Bureau of Mines radon test facility in 

Denver, Colo. The short-lived radon isotopes were allowed 

to decay before the sample was introduced to the cell, and 

only radon-222 e22Rn) concentrations were measured. The 

accuracy of the radon concentrations are ±50 pCi/L. 

Indoor radon concentrations from 21 homes were 

measured by charcoal canisters exposed in basements for a 

few days. These data were provided on a voluntary basis by 

the individual homeowners. The exact locations are not 

known, only the geologic formations in which the homes 

Using Geology and Soil-Gas Concentrations for Preliminary Estimates of Radon Potential 177 
Table 22. Soil-gas radon concentrations for the traverse in 

Prince Georges County, Md. 

[The sample locations are shown in figure 70, and the values are in 

sequence from west to east with reference to that figure. pCi/L, picocuries 

per liter] 

Sequence number Radon concentration 

(pCi/l} 

1 ................................. . 

2 

3 

4 ................................. . 

5 

6 

7 ................................. . 

8 

9 

10 ................................. . 

11 ................................. . 

12 ................................. . 

13 

14 ................................. . 

15 

16 ................................. . 

17 ................................. . 

18 

19 ................................. . 

20 ................................ .. 

21 ................................. . 

22 ................................. . 

23 

24 ................................ .. 

25 

26 ................................. . 

27 ................................. . 

28 ................................. . 

29 

30 

31 ................................. . 

32 

33 ................................. . 

34 ................................. . 

35 ................................. . 

36 

37 

38 ................................. . 

39 ................................. . 

40 ................................ .. 

41 ................................. . 

42 ................................. . 

43 ................................. . 

44 

45 ................................. . 

46 

47 ................................. . 

48 ................................. . 

1,250 

150 

1,100 

100 

900 

500 

700 

1,050 

1,000 

700 

1,000 

500 

450 

500 

1,050 

950 

100 

350 

850 

100 

100 

500 

700 

450 

400 

550 

200 

650 

900 

950 

150 

1,700 

700 

1,600 

2,700 

800 

1,050 

2,050 

250 

750 

650 

100 

1,300 

1,450 

950 

950 

150 

800 

were built. No indoor radon concentrations are available 

from locations along the traverse, so direct correlations 

between indoor radon and soil-gas radon are not possible. 

178 Field Studies of Radon in Rocks, Soils, and Water 

DATA AND DISCUSSION 

Forty-eight soil-gas samples were collected on the 

approximate 20-km (kilometer) traverse (fig. 70). The 

soil-gas radon concentrations range from 100 to 2,700 

pCi/L, with an arithmetic mean of 750 pCi/L. Table 22 

gives the radon concentrations for the individual samples, 

which are sequenced from west to east. Figure 71 shows 

frequency histograms of the soil-gas and indoor radon 

distribution for the individual geologic formations from 

which the samples were collected. The Tertiary formations 

show the greatest range in concentrations, although the data 

are too few to truly characterize the distribution. Figure 72 

shows a summary distribution of the radon concentrations 

for the specific formations, Quaternary, Tertiary, and Cre 

taceous, but, again, many have few data points. The highest 

concentrations are associated with the Chesapeake Group 

(Tc) and the Aquia Formation (Ta). The Chesapeake Group 

consists of light-colored, fine to very fine marine sand, silt, 

clay, and thin layers of diatomaceous earth, although these 

layers have been described as principally occurring south of 

the traverse location. The Aquia Formation is a greenishgray clayey sand composed mostly of quartz and glauconite. It is crossbedded and contains layers cemented by iron 

and shell layers cemented by carbonate. The Upper Member 

of the Nanjemoy Formation also contains glauconite but 

was not sampled during this survey. The Marlboro Clay 

Member of the Nanjemoy Formation (Tmb) is reported to 

contain glauconite sand also but only in the upper 1-m 

portion, and there the sand is restricted to filling in tubes or 

burrows. Higher concentrations of radioactive elements can 

be concentrated in glauconite and diatomaceous earth (Sverdrup and others, 1942). That this is the case with these 

particular sediments in Prince Georges County is suggested 

by the soil-gas radon data. Specific chemical analyses for 

radium and uranium would reveal if this association is 

correct. 

The soil-gas radon traverse crossed several zones of 

different radiation intensities revealed in the gamma aeroradioactivity map of Neuschel (1965). The highest gamma 

radiation along the traverse is associated geologically with a 

portion of the Tertiary Brightseat Formation and Monmouth 

Group (TKb), a marine sand and clay also containing 

glauconite. The mean radon concentration for the four 

soil-gas samples from this formation is 800 pCi/L, only 

slightly higher than the mean of 7 50 pCi/L for the entire 

data set. No observable correlation existed between the 

soil-gas radon and the higher gamma-aeroradioactivity 

signature, but more sampling would have to be performed 

for a sufficient comparison to be made. 

The upper limit of radon soil-gas concentrations 

observed in this study corresponds to some concentrations 

found in regions of the Reading Prong in Pennsylvania and 

New Jersey (Gundersen, unpub. data, 1987; Gundersen and 

others, 1988a), in Montgomery County, Md. (Gundersen 
0 • 76 55 

+ 0. 

38 55 

Stratigraphic Sequence 

Qal River Alluvium 

Qt River Terrace DepoSits 

Tc Chesapeake Group 

Tmb Nanjemoy Formation, Marlboro Clay Member 

Ta Aquia Formation 

N EXPLANATION 

2 km e sample location 0 

TKb Brightseat Formation 

Kpc Potomac Group, clay 

Kps Potomac Group, sand _ _ _ _ traverse route 

(geology after Hack, t 977) highest aeroradioactivlty 

Figure 70. Location of radon soil-gas samples on part of a geologic map of Prince Georges County, Md. 

and others, 1988b), and Fairfax County, Va. (Schumann 

and Owen, 1988), where houses with high indoor radon 

concentrations are located. Those previous studies indicate 

a relationship between high indoor radon levels where the 

soil-gas radon concentration exceeded about 2,000 pCi/L at 

a depth of0.75 em. Those studies also suggest that geology 

and soil gas were useful indicators of predictability for 

indoor radon. This appears to be the case with Prince 

Georges County as well. The radon soil-gas survey shows 

that soils derived from certain lithologies have the potential 

of supplying sufficient radon that could create an indoor 

radon accumulation in excess of the EPA guideline. 

CONCLUSIONS 

The use of a reconnaissance survey to estimate 

soil-gas radon potential has been tested in Prince Georges 

County, Md. It has revealed several Tertiary formations that 

have radon concentrations in excess of 2,000 pCi/L. Most 

of Prince Georges County, on the basis of projection from 

the areal distribution of the various geologic formations, 

appears to have low concentrations of soil-gas radon. Most 

tentatively, it appears that when the soil gas exceeds 2,000 

pCi/L, the probability is high that the indoor radon 

concentrations will exceed the EPA guideline; when soilgas concentrations are less than 300 pCi/L, the probability 

is low that the indoor concentrations will exceed the 

guideline. These levels of significance for soil-gas radon are 

also suggested from measurements in other areas of the 

United States. For example, when the data from this study, 

where average soil-gas and indoor radon concentrations are 

low, are compared to those with higher averages obtained in 

the Reading Prong of Pennsylvania (Gundersen and others, 

1988a), a trend evolves that suggests a correlation between 

soil gas and indoor concentrations. The variation in home 

construction methods and soil permeability will probably 

preclude rigorous values from ever being established, but as 

more data are collected the limits will be refined. 

ACKNOWLEDGMENTS 

The field work was conducted with the careful 

assistance of Mitch Henry. Information on indoor radon 

concentrations was provided by the Maryland Geological 

Survey. This work was supported in part by the Department 

of Energy, Office of Health and Environmental Research, 

under agreement DE-AI05-87-ER60579. 

Using Geology and Soil-Gas Concentrations for Preliminary Estimates of Radon Potential 179 
SOIL-GAS RADON 

;~ ........... ~.......,.__.....,.__...... I I I 

4i 1 001!1 21!11111!1 311101!1 

;i. •• ~ I I 

;~-----1-0~00----2-0~00 __ --3~000 I I I 

;~ .. ----1·0~00~--2-0~:~~----3~000 1,1 I t 

4i 11110111 211100 31!101!1 

;i I I 

I I :t_ 2000 1111111111 

~--~ I .. I 

I 

3000 

I 

I 

3000 

;~ 11.0 2111:111 I 

;i~--~1 ... 0~00----2-0~00----3-000 1 II I I I 

4i 100111 21110111 301110 

~-II I 

., I I 

;~-----1-0~00----2-0~00----3~000 I I I 

1000 2000 3000 

INDOOR RADON 

Oal 

Tu 

Tc 

Tmb 

Ta 

TKb 

Kpc 

Kps 

gn 

Figure 71. Frequency histograms of the radon distribution plotted by individual stratigraphic unit. The radon 

concentrations are in picocuries per liter (pCi/L). Tu, upland ancient river deposits; gn, gneiss and schist. No soil-gas 

samples were collected in those 2 units. See figure 70 for definitions of other rock symbols. 

180 Field Studies of Radon in Rocks, Soils, and Water 
SOIL-GAS RADON 

101210 

1000 

;t .... 

112100 

I 

2000 

2000 

I 

2000 

I 

3000 

3000 

I 

3000 

Q 

T 

K 

INDOOR RADON 

;~ I 

I I I I 

10 20 30 40 

;~ ~~~II~ I I 

I I 

10 20 30 4il 

;~ ... 

I I I I 

10 20 3il 40 

Figure 72. Frequency histograms of radon concentrations for units of Cretaceous (K), Tertiary (T), and Quaternary 

(Q) ages sampled during this study. The radon concentrations are in picocuries per liter. 

REFERENCES CITED 

Environmental Protection Agency, 1986, A citizen's guide to 

radon: What it is and what to do about it: Booklet 

OPA-8fHl04, Washington, D.C., U.S. Government Printing 

Office, 14 p. 

Gabelman, J.W., 1977, Migration of uranium and thorium-Exploration science: Tulsa, Okla., Studies in Geology No. 3, 

American Association of Petroleum Geologists, 168 p. 

Gundersen, L.C.S., Reimer, G.M., and Agard, S.S., 1988a, 

Correlation between geology, radon soil-gas and indoor 

radon in the Reading Prong, in Marikos,M., ed., Proceedings 

of the GEORAD Conference: Causes of Radionuclide 

Anomalies: Missouri Department of Natural Resources, 

Special Publication, no. 4, p. 91-102. 

Gundersen, L.C.S., Reimer, G.M., Wiggs, C.R., and Rice, 

C.A., 1988b, Map showing radon potential of rocks and soils 

in Montgomery County, Maryland: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-2043, scale 1:62,500. 

Hack, J.T., 1977, Geologic map for land-use planning, Prince 

Georges County, Maryland: U.S. Geological Survey 

Miscellaneous Investigations Series Map 1-1004, scale 

1:62,500. 

Jacobeen, F.H., Jr., 1972, Seismic evidence for high angle 

reverse faulting in the Coastal Plain of Prince Georges and 

Charles County, Maryland: Maryland Geological Survey 

Information Circular 13, 21 p. 

Neuschel, S.K., 1965, Natural gamma aeroradioactivity of the 

District of Columbia and parts of Maryland, Virginia, and 

West Virginia: U.S. Geological Survey Geophysical 

Investigations Map GP-475, scale 1:250,000. 

Reimer, G.M., 1977, Fixed-volume gas inlet system for an 

alpha-sensitive cell adapted for radon measurement: U.S. 

Geological Survey Open-File Report 77-409, 3 p. 

Reimer, G.M., and Bowles, C.G., 1979, Soil-gas helium 

concentrations in the vicinity of a uranium deposit, Red 

Desert, Wyoming: U.S. Geological Survey Open-File Report 

79-975, 9 p. 

Schumann, R.R., and Owen, D.E., 1988, Relationships between 

geology, equivalent uranium concentration, and radon in soil 

gas, Fairfax County, Virginia: U.S. Geological Survey OpenFile Report 88-18, 27 p. 

Sverdrup, H., Johnson, M. W., and Fleming, R.H., 1942, The 

Oceans: New York, N.Y., John Wiley and Sons, 379 p. 

Using Geology and Soil-Gas Concentrations for Preliminary Estimates of Radon Potential 181 

PART 2: STUDIES OF RADON IN WATER 

SECTION 1: INTRODUCTION 

A REVIEW OF THE CHEMICAL PROCESSES AFFECTING THE MOBILITY OF 

RADIONUCLIDES IN NATURAL WATERS, WITH APPLICATIONS 

Richard B. Wanty and Robert Schoen 

Abstract 

Increased awareness of possible health problems 

associated with radon-222 in indoor air in homes has 

prompted U.S. Geological Survey researchers to turn their 

attention toward understanding the natural processes that 

cause radon-222 concentrations in water to be anomalous 

in certain areas. As part of this effort, the mobility of radon 

and its parent elements in ground- and surface-water 

systems is being studied. Many of these studies, represented by papers in this volume, have found that in 

addition to radon-222 in water, other radionuclides such 

as uranium, thorium, and radium may be present in 

amounts that could lead to health risks. For this reason, it 

is important to understand the mobility of these elements 

in natural systems as well. This paper is intended to 

provide a background for understanding the results of the 

studies presented in this half of the volume by providing a 

review of the health effects associated with the radioelements, by summarizing the chemistry of the major radioelements, and by discussing the occurrence of radionuclides in various natural environments. 

INTRODUCTION 

Radon-222 e22Rn) is derived from the radioactive 

decay of uranium-238 e38U), which occurs to some extent 

in all rocks. The 238U decay series can be summarized as 

follows (fig. 73): 238U decays to thorium-234 e34Th), and 

in tum to protactinium-234 e34Pa), uranium-234 e34U), 

thorium-230 e30Th), radium-226 e26Ra), and 222Rn. 

Radon-222 decays by several successive steps, ultimately 

becoming nonradioactive lead-206 e06Pb). The bulk of the 

discussion in this paper will be limited to 222Rn and its more 

abundant precursors, uranium, thorium, and radium. The 

aqueous chemistry of each of these elements is different, so 

an understanding of the chemical behavior of each of the 

elements is prerequisite to an understanding of radon 

sources in ground-water systems. A discussion of the 

precursors of radon is important also because of possible 

negative health effects of uranium and radium in drinkingwater supplies. This paper provides brief reviews of the 

health effects and chemistry of radon and its parent elements and summarizes the results of a few of the studies that 

have been performed to date. In choosing the studies to be 

summarized, we have tried to represent several different 

geologic environments and to contrast those environments 

with one another. Many more studies that have been 

performed are not listed here. While this paper is not 

intended to be an exhaustive review of the current literature, 

this and the other papers in this volume will provide a 

suitable introduction to the current literature. 

Uranium, thorium, and radium all occur as dissolved 

ionic species in solution. Uranium has several possible 

oxidation states, so its mobility in natural environments is 

directly affected by changes in oxidation potential in addition to pH and other factors such as solution composition, 

concentration of certain complexing agents, and so forth. 

Thorium and radium each have only one oxidation state and 

thus are less affected by oxidation-reduction processes, but 

both are very sensitive to pH changes and other solution 

properties. Radon-222, on the other hand, is a noble gas and 

is not ionized in solution. The aqueous concentration of 222Rn is therefore most strongly affected by temperature and 

the presence of certain solid surfaces that may adsorb it. 

Important distinctions need to be made between 

secular equilibrium and chemical equilibrium. Discussion 

in this paper concerning the aqueous geochemistry of 

radionuclides will focus on chemical equilibria in natural 

waters. Chemical equilibria are established among aqueous 

species and solid phases according to the laws of thermodynamics. Chemical reactions occur in response to favorable energy changes between reactant and product species 

that drive the reaction toward the lower energy state. The 

tendency for a system to attain chemical equilibrium is a 

driving force in natural systems. On the other hand, secular 

equilibrium is a condition that is attained when the rates of 

radioactive decay of all nuclides in a decay series are equal. 

The attainment of secular equilibrium in a system (or lack 

thereof) is merely a condition that is or is not met and 

depends largely on the definition of the system and whether 

the defined system is open or closed. For instance, the 

system could include the ground water only, the rocks only, 

or both. Once a system is defined, secular equilibrium is 

attained as a function of time and may be aided, hindered, 

or prevented by chemical processes. If secular equilibrium 

is attained in a system, the radioactivity of each element in 

The Mobility of Radionudides in Natural Waters, with Applications 183 
214Pb 

~ 26.8 min 

206pb 

stable 

214Bi 

~214p0 

21og; 

~21op0 

saRa 90Th 

238U 

234Th 

234U 

Figure 73. The uranium-238 decay series, showing the half-lives of the radionuclide elements and their modes of decay. 

Pb, lead; Bi, bismuth; Po, polonium; Rn, radon; Th, thorium; Pa, protactinium; U, uranium; yr, years; min, minutes; 

IJ-S, microseconds; a denotes alpha decay, J3 denotes beta decay. 

the system is said to be supported by its parents. The 

radioactivity of an element is unsupported if that of its 

parents is less. In many cases, secular equilibrium is 

attained between two or more successive radionuclides in a 

184 Field Studies of Radon in Rocks, Soils, and Water 

decay series and not among the entire decay series. Thus, a 

common comparison is drawn between 226Ra and 222Rn 

without regard to the other elements in the decay series 

(fig. 73). 
EFFECTS OF NATURAL RADIONUCLIDES ON 

HEALTH 

Although the U.S. Geological Survey does not perform research on the health implications of the natural 

radionuclides, the subject is appropriate for a brief review 

here for several reasons. First is the obvious concern of 

society to control those substances that may provide the 

most serious threats to human health. A full understanding 

of the occurrence, transport, and fate of such substances is 

a necessary first step in their control. Second, a knowledge 

of the status of toxicological and epidemiological studies 

permits geoscientists to focus their investigations on those 

occurrences, pathways, and reactions that appear to be most 

relevant to the health scientists' needs. Finally, in conducting investigations of elements whose health implications are 

still being determined, a knowledge of these studies permits 

geoscientists to exercise a reasonable degree of caution in 

their studies of these elements. 

A highly readable compilation of articles on the 

health effects of uranium, radium, and radon in water can 

be found in the American Water Works Association Journal 

(April1987). For more information than is contained in this 

review, readers should consult those articles and their cited 

references. A more detailed treatment of these questions can 

be found in the many papers included in the May 1985 

volume of the journal Health Physics. Two recent publications, one by the National Research Council (1988) and the 

other by Nazaroff and Nero (1988), provide summaries of 

the more recent literature. 

Uranium 

Natural uranium consists of the three isotopes 238U, 235U, and 234U in the proportion 99.28 percent, 0.72 

percent, and 0.005 percent, respectively. Both 238U and 235U have half-lives of billions to hundreds of millions of 

years. The half-life of 234U is only 2.5 x 105 years, 

however, so the radioactivities from both 238U and 234U in 

natural uranium are equivalent (Aieta and others, 1987, p. 

145). A concentration of 100 j.Lg/L (micrograms per liter) of 

natural uranium yields a radioactivity of 67 pCi/L (picocuries per liter) if the 238U and 234U isotopes are in 

radioactive equilibrium (Wrenn and others, 1985, p. 609). 

It is known that uranium, when ingested, is a bone seeker 

similar to radium. There are, however, no unequivocal 

reports of ingested natural uranium causing cancer as 

radium has (National Research Council, 1988, p. 298). The 

health aspects of natural uranium appear to be entirely 

related to its chemical toxicity as a heavy metal and 

specifically to its nephrotoxicity (ability to cause kidney 

damage). The difficulty in demonstrating that natural uranium is radiotoxic is probably related to the fact that the 

levels of natural uranium that would cause nephrotoxicity 

provide very low doses of alpha radiation to the bone and 

bone marrow. Wrenn and others (1985, p. 611) call for 

further research on the levels of natural uranium in water 

and in the diet, in different geographic regions, to determine 

the amounts of uranium normally held in the human body. 

Radium 

On the basis of the experience of the radium-dial 

painters, the principal health aspect of ingested radium has 

long been known to be its induction of bone cancer 

(National Research Council, 1988, p. 177). Radium, an 

alkaline-earth cation, readily proxies for calcium in bone 

structure. As a bone seeker, it might be expected that 

radium would induce leukemia through its radiation effects 

on bone marrow; however, this effect appears to be insignificant compared to the number of bone sarcomas radium 

has caused (Mays and others, 1985, p. 637). Interestingly, 226Ra, unlike 228Ra or 224Ra, seems to cause carcinomas of 

the paranasal sinuses and the mastoid air cells. It has been 

suggested that these head carcinomas are related to the 

decay of 226Ra to 222Rn and the accumulation within the 

head cavities of 222Rn gas and its progeny (Mays and 

others, 1985, p. 636), and the National Research Council 

(1988, p. 238) concurs with this suggestion. Radium-228 

decays to 224Ra, but 220Rn, the daughter of 224Ra, has a 

half-life of only 54.5 seconds. This short half-life may 

prevent 220Rn from reaching and accumulating in head 

cavities. On the basis of the ingestion of the current 

Environmental Protection Agency Maximum Contaminant 

Level of 5 pCi/L of 226Ra plus 228Ra, the number of excess 

induced cancers in the lifetimes of 1 million persons would 

be 9 bone sarcomas and 12 head carcinomas from 5 pCi/L 

of 226Ra, 22 bone sarcomas and 0 head carcinomas from 5 

pCi/L of 228Ra, and 1.6 bone sarcomas and 0 head 

carcinomas from 5 pCi/L of 224Ra (Mays and others, 1985, 

p. 644). The National Research Council (1988, p. 238) calls 

for further research to elucidate the relation between sinus 

and mastoid carcinomas and the radon released during 

decay of radium in bone. 

Radon 

Undoubtedly, radon has been present in the atmospheres of homes since the first humans constructed shelters. This naturally occurring radioactive gas, found in 

enriched quantities in ground water, natural gas, and soil 

gas, can enter a house through use of ground water, burning 

of natural gas, leaks of soil gas into the substructure, and 

from the building materials themselves. 

Although naturally occurring radon has been present 

in building structures for as long as structures have been 

built, it is only in the last decade that relatively high values 

have been discovered in homes not otherwise associated 

with mining and milling activities. Before this, it was 

The Mobility of Radionudides in Natural Waters, with Applications 185 
believed that only structures built on or with uranium mill 

tailings would experience abnormally high levels of radon. 

It is now known that the normal low levels of uranium 

radium, and radon in rocks and soils can, under suitabl~ conditions, cause anomalous levels of radon in a home's 

atmosphere (Tanner, 1986, p. 5). 

On the basis of extrapolation from the experiences of 

uranium miners who were exposed to high levels of radon 

for several years, and who subsequently developed lung 

cancer, the Environmental Protection Agency has estimated 

the risk of an individual's developing lung cancer from 

living in a home that has low to moderate levels of radon. 

These studies have resulted in the Environmental Protection 

Agency's establishing an annual-average living-space concentration of 4 pCi/L of radon in the living quarters of a 

house as a guideline above which the risks increase and 

below which reducing the radon levels may be excessively 

expensive or impossible (Nazaroff and Nero, 1988, p. 

35-36). Radon levels are greatest generally in the winter, 

when windows and doors are shut and often tightly sealed 

with weatherstripping. As more outside air leaks into a 

house, the radon concentration decreases, because ordinary 

outdoor air has a very low concentration of radon (0.1 to 

0.15 pCi/L; National Council on Radiation Protection 

1984, p. 25). ' 

It is often assumed that radon causes lung cancer 

because, as a gas, it is inhaled into the lungs and while 

there, undergoes radioactive emission of an alpha particle 

and a gamma ray that cause carcinogenic damage to lung 

cells. In fact, most of the radon gas that one inhales is 

exhaled again within a few breaths. Because radon's halflife is 3.82 days, and because only small numbers of radon 

atoms are present in natural atmospheres, few if any 

radioactive disintegrations occur while the radon is in the 

lungs (Cothern, 1987, p. 154). At very high concentrations 

of radon, beyond naturally occurring levels, sufficient 

decay could occur during radon's brief residence in the 

lungs to make it a health concern. 

Radon's deleterious health effects are caused by its 

continued presence in a confined space, such as a home or 

an individual room, where the products of its relatively 

slow, infrequent disintegrations can accumulate (fig. 73). 

Radon-222 decays into a series of solid daughter radioisotopes. The first four, 218Po, 214Pb, 214Bi, and 214Po, have 

combined half-lives of less than 50 minutes. As solid, 

charged particles, these metal ions adsorb almost instantly 

to any surfaces or dust particles in the atmosphere of the 

home, although a significant fraction can remain unattached. When these dust particles and unattached ions are 

inhaled, they tend to lodge in the lungs, whose tissues are 

then subjected to the relatively rapid delivery of radioactive 

disintegrations during the combined short half-lives. 

Because of the accepted relation between lung cancer 

and radon exposure in the Colorado Plateau uranium miners, the focus of radon research has been on the inhalation 

186 Field Studies of Radon in Rocks, Soils, and Water 

route of radon and its progeny. Relatively little work has 

been done on the ingestion of radon in drinking water, 

where its concentration can be high. It is generally assumed 

that the primary health effect of radon-rich water is through 

its contribution to the atmosphere of the home by degassing. 

Studies of the degassing of radon from water into the 

atmosphere of a home have produced values of the mean 

transfer factor, f, ranging from 1.0 to 2.5 x 10-\ in the 

equation 

Ca= fCw, 

where C a is the radon concentration in air and C is the 

radon concentration in water (Nazaroff and Nero, t988, p. 

132). 

This equation demonstrates that the concentration of 

radon in a home attributable to degassing of radon from the 

water will be only about 1110,000 of the water concentration. The few studies that have evaluated this transfer 

coefficient have found that the major sources of uncertainty 

lie in the amount of house volume to ascribe to each 

occupant and in the average air-exchange rate to use. It is 

also implicitly assumed that the degassed radon and its 

progeny are distributed uniformly throughout the house 

volume and not concentrated at the point of degassing. 

Thus, it can be expected that such wide variations to the "1 

in 10,000 rule" may be found in individual homes as to 

make it impractical for the individual to rely on its accuracy. 

With respect to water-borne radon, the National 

Research Council (1988, p. 80) recommends further 

research on the possible long-term health effects of ingesting radon-rich water. Nazaroff and Nero (1988, p. 143) 

note the need to improve the estimate of the parameters that 

determine the transfer factor, f. Finally, in determining the 

concentration of radon and its progeny in homes using 

radon-rich water, it will be useful to measure the spatial 

distribution with time in order to test the assumption of 

uniform distribution throughout the house volume. 

INORGANIC CHEMISTRY OF RADON AND ITS 

PARENT ELEMENTS 

The geochemical processes that affect the mobility 

and fixation of the parent elements of 222Rn in the natural 

environment are summarized in this section. Natural processes that limit the mobility of these elements include 

precipitation, coprecipitation, adsorption, and ion 

exchange. In this section, we review the chemistry of 

uranium, thorium, radium, and radon in the context of these 

processes. 

Uranium 

Uranium may be present in natural waters in three 

formal oxidation states, namely IV, V, and VI. In general, 
U) 

Cl) 

"(3 

Cl) 

c. 

en 

~ 

> 

-:::» 

"C 

Cl) 

> 0 

U) 

U) 

c 

0 ~ 

Cl) 

0 

:E 

100 

80 

60 

40 

20 

0 

2 4 6 

pH 

8 

2- U0 (C~) 2 

) 

10 

Figure 74. The distribution of inorganic aqueous species of uranium as a function of pH (modified from Langmuir, 1978). 

In the calculation of the diagram, the following aqueous concentrations were used: PC02 = 10-2·

5 atm; IF= 1.6 x 10-5 

m; ICI = 2.8 x 10-4 m; !.504 = 1.0 x 10-3 m; IP04 = 1.1 x 10-6 m; ISi02 = 5.0 x 10-4 m. 

uranium is most soluble in oxidizing water. Uranium(VI) 

occurs in solution as the uranyl ion, U02

2 +, or some 

complex thereof. The uranyl ion is the most soluble form of 

uranium and forms strong complexes with carbonate and 

biphosphate at pH values greater than approximately 4 

(Hostetler and Garrels, 1962; Langmuir, 1978; Dongarra 

and Langmuir, 1980). Complexes with fluoride or sulfate 

may be important below pH 5 (fig. 74). There is also 

evidence that uranyl may be effectively complexed by 

humic acids at pH values between 3.5 and 7 (Kribek and 

Podlaha, 1980), although Shanbag and Choppin (1981) 

present other evidence that the uranyl-humic acid complex 

may be relatively insoluble and that humic acid in the solid 

state would effectively scavenge uranyl from solution. 

Uranyl minerals are seldom precipitated from aqueous solutions in natural environments. Uranyl hydroxide 

(schoepite; U02[0Hlz· H20) is quite soluble in natural 

waters, but uranyl vanadate minerals such as carnotite 

(K2 [U02]z[V04]z) or tyuyamunite (Ca[U02]z[V04 ]z) may 

precipitate if the vanadate and potassium or calcium concentrations are high enough (see Langmuir, 1978). 

In oxidizing waters, uranyl ions may be adsorbed to 

varying extents onto solid substrates such as iron oxides 

(Hsi, 1981; Ames and others, 1983a; Hsi and Langmuir, 

1985), organic material (Moore, 1954; Breger and others, 

1955; Schmidt-Collerus, 1967; Leventhal and others, 

1986), clay minerals (Ames and others, 1983b), and micaceous minerals (Ames and others, 1983c). The adsorption 

of the uranyl ion onto these substrates is strongest at 

near-neutral pH and weaker at much higher and lower 

values. At low pH, hydrogen ions effectively compete for 

surface sites, while at higher pH, carbonate complexing of 

uranyl leads to desorption. 

The uranyl ion is stable only in oxidizing systems and 

is reduced to U(V) or U(IV) under progressively reducing 

conditions. The reduction of U(VI) occurs readily in the 

presence of H2S (Mohagheghi, 1985), and the reaction is 

strongly catalyzed by mineral surfaces. The end product of 

this reaction is the reduced uranium oxide mineral, uraninite 

(U02), or some amorphous form with a similar stoichiometry (fig. 75). In natural waters that have significant silica 

concentrations, coffinite (U[Si04] 4 _x(OH] 4J may precipiThe Mobility of Radionuclides in Natural Waters, with Applications 187 
0.8 

~ 

uo2+ OC") 

2 2.. 

C\1 

0 cl..~ ::> 

-tn 0.4 cS ... 2.. 0 C\1 

> 0 - ::> .c 

w 

0 

-0.4 

0 2 4 6 8 10 

pH 

Figure 75. Distribution of inorganic uranium species in 

Eh-pH space for the system U-0-C-H at 25 oc and 10-2 ·

5 

atm C02 • The stippled area represents the stability field 

for uraninite at a total uranium concentration of 10-6 M 

(modified from Langmuir, 1978). 

tate instead ( Goldhaber and others, 1987). Reduction and 

precipitation of uranium may lead to a significant accumulation of uranium if there is a sharp transition from 

oxidizing to reducing conditions in an aquifer. In order to 

get a significant accumulation, this transition zone must be 

stable for geologically significant periods of time. Conditions such as these are met in many instances in the Western 

United States, particularly on the Colorado Plateau, the 

Wyoming intermontane basins, and the south Texas coastal 

plain. In many of these cases, uranium may have accumulated to levels of several percent of the rock. These uranium 

deposits are of particular interest because uranium accumulations in rocks are known to produce anomalous radon 

concentrations in ground waters (Chatham and others, 

1981; Wanty and Gundersen, 1987). Nash and others 

(1981) summarize many known types of uranium deposits 

and give descriptions of their origins. 

Thorium 

Thorium has only one formal oxidation state in 

nature, namely thorium[IV] (Zebroski and others, 1951). 

188 Field Studies of Radon in Rocks, Soils, and Water 

Aqueous thorium(IV) is strongly hydrolyzed in the series 

Th(OH)n 4 -n, where n=0-4 (Langmuir and Herman, 

1980); the species Th(OH)/ dominates above pH of 

approximately 4.5. Strong complexes are known to exist 

between thorium and biphosphate, oxalate, and EDTA at 

pH values commonly found in nature (Zebroski and others, 

1951; Waggener and Stoughton, 1952; and Langmuir and 

Herman, 1980). 

Thorium is generally considered to be insoluble in 

most natural waters. It occurs in the solid form most 

commonly as a minor constituent in solid solution in 

phosphate, oxide, or silicate minerals. It is the major 

component in the relatively rare minerals thorianite (Th02) 

and thorite (ThSi04 ). The most important commercial 

source of thorium is from monazite ([Ce, La, Nd, Th] P04 ), 

which is concentrated in stream sediments and reworked 

beach sands (Rankama and Sahama, 1950). All these 

minerals are quite insoluble; even in solutions that have 

very high concentrations of complexing agents, calculated 

solubilities for thorianite rarely exceed 1 ppb Th above pH 

5 (Langmuir and Herman, 1980). 

Studies indicate that thorium is adsorbed strongly 

onto kaolinite (Riese, 1982) and a-quartz (James and 

Healy, 1972; Riese, 1982) at pH values above about 4. 

Riese ( 1982) found that thorium adsorption was inhibited by 

increasing the sulfate concentration, but even then adsorption was virtually complete at pH values higher than 5.5. 

Thus, if thorium is not present within the crystal structure of 

some mineral, it probably is adsorbed onto an oxide or 

silicate surface; only vanishingly small amounts are present 

ordinarily in aqueous solution. For more details about the 

geochemical behavior of thorium, the reader is referred to 

Langmuir and Herman ( 1980). 

Radium 

Like thorium, radium has only one oxidation state in 

natural systems, in this case, radium(II). But here the 

similarities end; the chemistry of radium is much different 

than that of thorium in natural systems because radium has 

much less of a tendency to hydrolyze. Radium behaves in 

many respects like other alkaline earth elements (Group 

Ila). It forms strong complexes with sulfate and carbonate 

(fig. 76) and weaker complexes with nitrate and chloride 

(Langmuir and Riese, 1985). Complexing of radium by 

organic materials is not well characterized, although weak 

1: 1 complexes with several organic acid species have been 

detected by Schubert and others (1950). 

Radium mobility is limited in natural systems by 

several processes, chiefly coprecipitation, adsorption, and 

ion exchange. Although the solids RaS04 and RaC03 are 

sparingly soluble (pKsp values of 8.30 and 10.26, respectively, according to Langmuir and Riese, 1985), they rarely 

form because radium concentrations are so restricted by 
100 

Ra2+ 

0 

CD 80 

·c:; 

CD 

a. 

en 

-

s 60 

as 

a: 

"C 

CD 

> 

0 40 tn 

0 

Q 

-;R, 0 

CD 20 

0 

:E RaSo4o 

0 

2 4 6 8 10 

pH 

Figure 76. The distribution of inorganic aqueous radium 

species as a function of pH for the following conditions: ~C03 = 1.0 X 10-2 m; :£504 = 1.0 X 10-4 m; ~CI = 1.0 X 

10-4 m. No chloride complexes are sufficiently significant 

to plot on the diagram. 

other processes that natural waters are seldom oversaturated 

with respect to these phases. If radium precipitates in a solid 

phase, it usually does so in solid solution in barite (Doerner 

and Hoskins, 1925), where it substitutes for barium. 

Radium may coprecipitate in calcite as well (Tanner, 

1964a). 

Radium is strongly adsorbed by mineral surfaces, 

including quartz, kaolinite, and other clay minerals (Riese, 

1982; Ames and others, 1983c,d). It is also strongly 

adsorbed on iron(III) oxyhydroxides (Ames and others, 

1983a), and Levinson (1980) argues that radium that is 

adsorbed on a precipitating ferric oxyhydroxide may be 

absorbed as the ferric oxyhydroxide continues to grow. For 

a detailed review of the chemistry of radium, the reader is 

referred to Weigel ( 1977). 

Radon 

Radon mobility in natural waters is affected principally by physical, rather than chemical, processes. Being a 

noble gas, radon is not ionized in solution, nor does it 

precipitate in solid phases. It may be adsorbed to a limited 

extent by organic material, especially charcoal (Lowry and 

Brandow, 1985), but there is little evidence available to 

suggest that it is adsorbed to any great degree by other 

surfaces. 

Radon is soluble in water; the solubility is sensitive to 

temperature. Solubilities for the temperature range 0 to 100 

Table 23. The solubility of radon in water from 0 to 100 oc 

[The data shown are from Weigel (1978). Units are moles of radon per liter 

with a radon partial pressure of 1 atm] 

Temperature Radon 

(Celsius) solubility 

0 ··············· 0.510 

5 ··············· .42o 

10 ............... .350 

20 ............... .255 

30 ··············· .200 

40 ··············· .160 

50 ............... .140 

60 ··············· .127 

70 ............... .llg 

80 ............... .112 

90 ............... .109 

100 ............... .107 

°C are given in table 23. At 10 °C, the solubility of radon is 

approximately 61 times that of oxygen on a mass basis 

(Lowry and Brandow, 1985). Because the partial pressure 

of radon in air is ordinarily very low, radon is readily 

degassed from water that is exposed to air. Thus, radon 

concentrations found in surface waters are in general several 

orders of magnitude lower than those in ground waters. In 

addition, domestic ground-water supplies that are high in 

radon may contribute significantly to indoor airborne radon. 

A thorough review of radon chemistry is provided by 

Weigel (1978). 

SUMMARY OF SELECTED STUDIES 

The mobility, distribution, and chemical form of U, 

Th, Ra, and Rn in natural surface- and ground-water 

systems will be determined by chemical processes as 

described previously and by physical properties of the 

natural system (for instance, temperature, pressure, flow 

rate, porosity, permeability). In this section we will 

describe some previous studies on radionuclides in ground 

waters in sandstone and crystalline aquifer systems. Despite 

the differences in application of these studies, the chemical 

processes that must be considered remain the same. Thus, 

the studies of broadest interest will be those that examined 

the overall water chemistry as well as the abundances of the 

radionuclides. 

As seen in the previous section, the mobility of each 

of the radioactive parent elements of radon is affected to 

different degrees by different chemical processes. It is 

through an understanding of the chemical behavior of the 

radionuclides that the natural systems can be better understood. In the ensuing discussion, radionuclide mobility in 

specific natural systems will be discussed, and one system 

will be compared and contrasted to the other. This discussion will be separated according to aquifer rock type, so 

sedimentary aquifer systems will be divided from fracturedThe Mobility of Radionuclides in Natural Waters, with Applications 189 
rock aquifer systems. These two types of systems have 

profoundly different hydrologic regimes. The differences in 

hydrology are manifested in differences in radionuclide 

mobility, particularly in the differential mobilities between 226Ra and 222Rn. 

Sedimentary Aquifer Systems 

Many studies have been performed on radionuclide 

migration in sedimentary aquifer systems, some related to 

health aspects, others related to exploration for subsurface 

uranium deposits. We give here a brief summary of selected 

studies, stressing the dependence of radionuclide mobility 

on natural chemical processes active in these aquifer systems. 

Many studies have focused on radon distribution in 

ground waters. The results of these studies have been 

applied to the investigation of geologic structure, as in the 

study of Mazor (1962), or to ground water geochemistry, as 

by Tanner (1964a). Radium-226 and 222Rn distributions in 

ground waters near Great Salt Lake, Utah, were studied by 

Tanner (1964a). He found that the waters were for the most 

part out of secular equilibrium and that 222Rn concentrations 

were much higher than would be expected, given the 

aqueous 226Ra concentrations. He proposed that the 226Ra 

was for the most part locally derived and that it was likely 

adsorbed on iron-oxide surfaces. In contrast, Rama and 

Moore (1984) proposed that radon in water could be derived 

from radium within grains in the rocks and that an extensive 

network of minuscule pores serves as a migration pathway 

for the radon thus produced. 

Uranium is immobile in reducing systems; thus, 

organic-rich black shales tend to be more enriched in 

uranium than do coarse-grained rocks (see Krauskopf, 

1967). Uranium may be immobile in reduced systems, but 

its daughters often are mobile. In a study of radionuclide 

geochemistry in the Newark basin of New Jersey, Zapecza 

and Szabo (1987) found high gross alpha-particle activities 

in ground waters near organic-rich black shales and determined from borehole geophysical tests that the black shales 

were anomalously radioactive. In a companion study, 

Szabo and Zapecza ( 1987) showed that dissolved uranium 

concentrations were low in the reducing waters associated 

with the black shales, but dissolved 226Ra concentrations 

were higher, accounting for most of the gross alpha-particle 

activity. Further, they found low 226Ra concentrations in 

sulfate-rich waters, as would be expected if radium sulfate 

solids formed. In agreement with the findings of Tanner 

(1964a), the Newark basin studies found that aqueous radon 

activities were much higher than those of radium, again 

leading to the conclusion that aqueous radon is derived from 

radium in the solid phase. 

In many cases, 226Ra concentration is low (less than 

1 pCi/L) because of adsorption or precipitation processes. 

190 Field Studies of Radon in Rocks, Soils, and Water 

An exceptional area was reported by Cecil and others 

(1987) for the Chickies Formation (Late Proterozoic) in 

southeastern Pennsylvania. Here, the 222Rn activities are 

not particularly high (usually less than 10,000 pCi/L), 

although they are always greater than the 226Ra levels. The 

exceptional aspect of the Chickies Formation ground waters 

is the high 226Ra activities and, in most wells, the even 

higher 228Ra activities. Cecil and others attributed the high 

total radium levels to low pH values in the ground water and 

the concomitantly lesser degrees of adsorption of radium 

onto the aquifer materials. Their research is continuing to 

determine the source of this radium, and the reason for the 

anomalously high 228Ra/226Ra ratios (Cecil and others, this 

volume). 

Chatham and others ( 1981) and W anty and others 

(1987) studied ground-water geochemistry in a sandstone 

aquifer that hosted several uranium deposits in south Texas. 

They found that dissolved uranium was highest in updip, 

oxidizing waters near the recharge zone and that it 

decreased abruptly downdip as dissolved oxygen was 

depleted in the ground water. This abrupt decrease in 

dissolved uranium corresponded to the location of the 

uranium deposits in the area. Ground waters in contact with 

the uranium deposits were low in sulfate and high in 226Ra 

and 222Rn, but other ground-water samples from the area 

contained significantly lower 226Ra and 222Rn activities. 

Thus, in the south Texas study area, very high uranium 

levels in rocks (tenths of a percent uranium by weight) were 

required to produce significant levels of 222Rn (thousands of 

picocuries per liter) in the associated ground water. 

In summarizing the sedimentary aquifer systems that 

have been studied, we must note that ground-water concentrations of uranium are highest in oxidized waters, usually 

near the recharge zone. In reduced waters, uranium concentrations are much lower. Thorium in ground water is 

rarely measured but has been found to be low. Radium-226 

activities may be high (several picocuries per liter) in some 

waters, particularly in the absence of sulfate. Radon-222 

activities usually are much higher than would be predicted 

from the aqueous 226Ra activities, and 222Rn highs in the 

ground water usually correspond to nearby enrichments of 

its parent elements in the rocks. 

Fractured-Rock Aquifer Systems 

There have been many studies of radionuclide concentrations in crystalline rocks, particularly in the New 

England States, where extremely high 222Rn activities have 

been found in some ground waters. A summary of natural 

radioactivity in New England by Hall and others (1987) 

shows a wide range of uranium contents in the rocks and a 

complex distribution of that uranium within the rock fabric. 

Nevertheless, Hall and others (1987) show a map of 

lithologic groups that have the potential to produce large 
quantities of radon that could be released to the ground 

water. In Maine, Brutsaert and others (1981) showed that 

very high 222Rn concentrations are present in ground waters 

from granitic rocks and from some high-grade metamorphic 

rocks. Hall and others ( 1985) found similar relationships in 

New Hampshire, where glacial deposits, low-grade metamorphics, and basic intrusive rocks had low ground-water 222Rn activities, and high-grade metamorphics and granites 

had very high ground-water 222Rn activities. 

In a study of ground waters from two-mica granites in 

Maine and New Hampshire, Wathen (1986) found very 

high 222Rn concentrations, up to 145,000 pCi/L. Through 

the use of autoradiographs, he showed that uranium was 

most strongly concentrated along boundaries of weathered 

biotite grains, and in sericitized plagioclase grains, the 

indication being that uranium was adsorbed on these surfaces. Thus, as 238U in these rocks decayed, the daughter 

elements would be close to the solution-solid interface, and 222Rn would be available to the water. Asikainen and 

Kahlos (1979) provided isotopic evidence from well waters 

collected near Helsinki, Finland, that showed that the 

dissolved 222Rn was derived from parent elements localized 

along fracture walls, substantiating Wathen's conclusions. 

The previous two studies showed a common result in 

that the ground-water 222Rn levels were unsupported by the 

parent elements. A study in two different areas of the 

Reading Prong in eastern Pennsylvania by Wanty and 

Gundersen (1987; 1988) agrees with these results. In 

virtually every water sample, the 222Rn activity was almost 

completely unsupported by the parent elements. In this 

case, autoradiographs of the rocks showed a concentration 

of radioactivity near grain margins and fracture boundaries. 

In addition, analyses of the aquifer rocks (Gundersen and 

others, 1988) show that the 238U and 226Ra contents of the 

rocks are high enough to support the 222Rn activity in the 

water. Thus, although the water itself is not in secular 

equilibrium, the entire water-rock system is. 

Two studies have recently been published from North 

Carolina (King and others, 1982) and South Carolina 

(Loomis, 1987). Both of these studies extended across the 

boundary between crystalline rocks of the Appalachian 

Piedmont and sediments of the Atlantic Coastal Plain and 

arrived at substantially similar conclusions. In both States, 

the metamorphic and igneous rocks of the Appalachian 

Piedmont had significantly higher ground-water radon (one 

to three orders of magnitude difference) than did the coastal 

plain sediments. Similarly in both States, the dissolved 222Rn concentrations were unsupported by dissolved 226Ra, 

regardless of rock type. 

Hydrologic factors probably are of importance in 

explaining the significant differences found between 

fractured-rock aquifers and sedimentary aquifers. Significant hydrologic differences exist between these two classifications of aquifers, especially in ground-water flow rates, 

residence times, the volumetric ratios between water and 

rock, and the surface area of rock per volume of water. 

These hydrologic properties define and constrain the physical characteristics of the aquifers. These physical properties may in tum affect the mobility of 222Rn or its parent 

radionuclides. For instance, Hall and others (1985) found 

an inverse correlation between dissolved radon activity and 

well yield. Rumbaugh (1983) noted the same relationship in 

ground waters of the Reading Prong, Pa., and ascribed this 

relationship to a simple theoretical model involving aquifer 

transmissivity and fracture aperture. He found that 

increased average fracture aperture, and attendant higher 

well yields, led to lower aqueous 222Rn concentrations. 

Conversely, smaller average fracture apertures associated 

with lower well yields had consistently higher dissolved 222Rn levels. Perhaps the best direct comparison between 

sedimentary and fracture-flow aquifers comes from the 

results of King and others (1982) and Loomis (1987). Both 

of these studies showed that average dissolved 222Rn 

activities were lower in the sedimentary aquifers. The 

relatively higher water/rock ratio of the porous sedimentary 

aquifers relative to fractured crystalline ones may be the 

reason that sedimentary aquifers have generally lower 222Rn 

concentrations (Wanty and Gundersen, 1987). 

SUMMARY AND CONCLUSIONS 

The mobility of radionuclides in ground waters is 

controlled primarily by chemical and physical processes as 

constrained by the aquifer rock type. In general, dissolved 

uranium is likely to be found in greater quantity in oxidized 

ground waters hosted by granitic rocks, or in some cases in 

high-grade metamorphic rocks. Uranium accumulations in 

sedimentary rocks are relatively rare but occur at the 

transition between oxidizing and reducing conditions along 

a ground-water flow path. In the sedimentary aquifer 

systems, highest dissolved uranium concentrations usually 

are found near the outcrop, where oxidizing recharge waters 

are percolating into the ground. Thorium is strongly hydrolyzed and nearly insoluble in all waters. Radium may be 

quite soluble in ground waters, particularly in the absence 

of sulfate. Nevertheless, the mobility of radium is impeded 

by its relatively strong adsorption onto mineral surfaces 

such as ferric oxyhydroxides and clays. Radon-222 is 

extremely soluble in water and not easily adsorbed on most 

mineral surfaces, so its concentration in ground water is 

commonly higher than that of its parents, and secular 

equilibrium between 222Rn and its parents in water is rarely 

realized. On the other hand, the overall water-rock system 

may attain secular equilibrium. 

A brief review of previous studies of radionuclide 

migration in a variety of aquifer rock types indicates that 

ground waters in high-grade metamorphic rocks and granitic igneous rocks generally have the highest dissolved 222Rn activities. Ground waters in low-grade metamorphics 

The Mobility of Radionuclides in Natural Waters, with Applications 191 
and sedimentary rocks are generally lower in 222Rn. One 

notable exception is the case where uranium has 

accumulated in sediments at the interface between oxidizing 

and reducing conditions. 

Development of a more complete understanding of 

the movement of radionuclides in ground water requires 

more comprehensive studies. Integrated geologic, 

hydrologic, and geochemical approaches are required to 

characterize the major variables of the natural system under 

study. Such studies would be able to answer the greatest 

range of questions concerning sources and sinks of radionuclides and mechanisms for their mobility in ground-water 

systems. 

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194 Field Studies of Radon in Rocks, Soils, and Water 
RADIONUCLIDES IN GROUND WATER, ROCK AND SOIL, AND INDOOR AIR OF THE 

NORTHEASTERN UNITED STATES AND SOUTHEASTERN CANADA-A LITERATURE 

REVIEW AND SUMMARY OF DATA 

Robert T. Paulsen 1 

Abstract 

This report briefly summarizes major investigations 

ofthe occurrence and concentrations of uranium, radium226, and radon-222 in ground water, rock and soil, and 

indoor air in the six New England States, New York, and 

southern Ontario since the 1950's. It includes tables of 

concentration data for each State and describes the major 

results of the 155 studies cited. 

The first studies of radionuclides in the Northeast 

began in the 1950's and 1960's as uranium exploration. 

Through the 1970's and 1980's, the focus of research 

changed from uranium exploration to the occurrence and 

concentration of uranium, radium-226, and radon-222 in 

the ground water, rock and soil, and indoor air. This 

change in focus was prompted by the discovery that 

exposure to alpha-radiation-emitting daughter products 

from the radioactive decay of uranium was possibly a 

serious threat to human health. Radon-222 in ground 

water has been measured in concentrations greater than 

1,000,000 picocuries per liter in Maine; the national average is 350 picocuries per liter. Uranium content of bedrock in the Northeast ranges from 0.001 to 0.400 percent 

by weight. Radium-226, the radioactive parent of radon222, has been measured in various soils in New York and 

Ontario; concentrations ranged from 0.2 to 7.0 picocuries 

per gram. Radon-222 in indoor air has been measured in 

concentrations greater than 1,200 picocuries per liter in 

Maine. The Environmental Protection Agency suggests 

precautionary action be taken at an indoor air concentration of 4.0 picocuries per liter. 

INTRODUCTION 

The occurrence and distribution of the radionuclides 

uranium, radium, and radon-222 e22Rn) in the environment 

have become prominent research topics in the Northeastern 

United States as well as nationally. Research on 222Rn in the 

environment has roots in the exploration for uranium, and 

some of the earliest exploration for, and are research on, the 

distribution of radionuclides in the ground water and air was 

done in New England during the early 1960's. The deleterious health effects of inhalation or ingestion of radionuclides, especially 222Rn daughter products, are receiving 

national attention in the media and arousing concern. 

Recently, radon has been noted as the most widespread 

naturally occurring contaminant measured in drinking 

water, and the health risks from exposure to radon daughter 

1

The Paulsen Group, Huntington, N.Y. 

products may be far in excess of any posed by manmade 

organic compounds that are currently regulated (C.R. 

Cothern, Office of Drinking Water, Environmental Protection Agency, oral commun. , 1987). In response to the 

estimated 5,000 to 20,000 annual cancer fatalities attributed 

to exposure to radon daughter products (Environmental 

Protection Agency, 1986), the public, legislators, and the 

scientific community are asking ( 1) which radionuclides 

they should be concerned with, (2) where they come from 

and where are they most prevalent, and (3) how they can be 

removed to lessen the health risks associated with them. 

This report addresses the source and prevalence of 

radionuclides and summarizes the research into their occurrence and distribution in ground water, rocks and soil, and 

indoor air in New England, New York, and southeastern 

Ontario (fig. 77). The research summaries are grouped by 

State, and the section for each State contains tables of 

reported radionuclide concentrations in ground-water samples and 222Rn concentrations in indoor air. This report 

summarizes the available research but does not provide 

interpretations of the cited data. 

HISTORICAL PERSPECTIVE 

Although research into the occurrence and distribution of 222Rn and other radionuclides in the environment 

may appear to be a relatively new topic, research on the 

occurrence and distribution of uranium-238 e38U) that was 

done in the 1950's included the measurment of 222Rn. The 

petroleum industry recognized a strong correlation between 222Rn emanations from overburden and petroleum resources 

in the underlying rocks and has measured for 222Rn as an 

oil-exploration tool. The U.S. Department of Energy's 

National Uranium Resource Evaluation program, which ran 

from 1974 through 1984, was designed to explore the 

Nation for uranium deposits. The resulting data are now 

being reevaluated to outline probable 222Rn problem areas. 

Some researchers in 222Rn investigations are reanalyzing 

the data they collected decades ago. 

National Research Before 1961 

The role of 222Rn in the lung cancer of miners in 

central Europe, although first suspected in 1932, was not 

generally accepted until the 1960's. In 1949, the U.S. 

Atomic Energy Commission and the Colorado State DepartRadionudides in the Northeastern United States and Southeastern Canada 195 
PENNSYLVANIA 

OHIO 

Figure 77. Location of areas represented in this review. 

ment of Health, aware of the European experience, obtained 

data on 222Rn in several mines in the United States. During 

1950-52, health physicists suggested that a health hazard 

existed as a result of the alpha-radiation dose delivered 

through lung deposition of the short-lived alpha-emitting 

daughters of 222Rn rather than from 222Rn itself (D.C. 

Hoxie, Maine Division of Health Engineering, written 

commun., 1988). 

From 1947 through 1957, the U.S. Atomic Energy 

Commission worked with the U.S. Geological Survey in a 

nationwide exploration for uranium (Warren Finch, U.S. 

Geological Survey, oral commun., 1988). Much of the 

information collected was published in U.S. Geological 

Survey trace-element reports, including those by McKeown 

(1951), Nelson and Narten (1951), and Johnson (1951), 

who determined from Geiger-counter surveys by automobile and studies of radioactivity in rocks that the total 

uranium content of rocks in Vermont, Massachusetts, 

Rhode Island, Connecticut, and New York ranged from 

0.002 to 0.400 percent by weight. 

The U.S. Geological Survey published several 

reports during the middle to late 1950's on the occurrence of 

uranium throughout the United States. Gott and others 

(1952) described total uranium occurrences in black shales, 

lignites, and limestones across the United States, including 

196 Field Studies of Radon in Rocks, Soils, and Water 

QUEBEC 

50 100 150 MILES 

0 100 200KILOMETERS 

sites in Vermont and New York. Their findings suggest that 

uranium was associated with carbonaceous material or 

occurred as secondary infillings such as vugs. In 1955, the 

International Commission on Radiological Protection set an 

occupational exposure limit for uranium miners of 10 

pCi/L (picocuries per liter) for 222Rn, and the U.S. Atomic 

Energy Commission set a limit of 100 pCi/L for 222Rn 

(D.C. Hoxie, Maine Division of Health Engineering, written commun., 1988). McKelvey (1955) described uranium 

in secondary veins in igneous and metamorphic rocks of 

New York and distributed throughout Precambrian dolomites in Vermont. McKeown and Klemic (1956) measured 

uranium and thorium contents of 0.032 and 0.150 percent 

by weight, respectively, in apatite in the Adirondack 

Mountains of New York. Chew ( 1956) described a field 

study of radioactivity in stream gravels and how the 

locations of ore deposits could be determined through such 

field surveys. 

Cooper (1958) summarized research prior to 1958 on 

the occurrence of radionuclides in Connecticut, Delaware, 

Illinois, Indiana, Maine, Maryland, Massachusetts, Michigan, New Hampshire, New Jersey, New York, Ohio, 

Pennsylvania, Rhode Island, Vermont, and Wisconsin. The 

publication includes cross-referenced bibliographic information that relates mostly to radioactivity in rocks. 
In 1958, The State of Maine Department of Human 

Services was notified of the presence of a high concentration of radioactivity in water from a private well in western 

Maine (Smith and others, 1961) and sent an engineer to 

investigate. Results confirmed high concentrations of 

radium-226 CZ26Ra) and 222Rn (D.C. Hoxie, Maine Division of Health Engineering, written commun., 1988). In 

1959, the U.S. Public Health Service funded the Georgia 

Institute of Technology to check 250 wells, drilled in 

various terranes in Maine and New Hampshire (D.C. 

Hoxie, Maine Division of Health Engineering, written 

commun., 1988); results indicated that 99.2 percent of the 

drilled wells tested contained more than 2,000 pCi/L 222Rn 

and 222Rn daughters (Grune and others, 1960; Smith and 

others, 1961). 

1961-70 

When the U.S. Atomic Energy Commission stopped 

purchases of uranium in the late 1950's, the focus of 

research shifted from uranium exploration to radioactivity 

in surface water and ground water. Scott and Barker (1962) 

published data on the uranium and radium content of the 

ground waters of Maine, New Hampshire, Massachusetts, 

Rhode Island, Connecticut, and New York. Barker and 

Robinson (1963) described methods of determining beta 

activity in water, including procedures for sample collection, preservation, and analysis with a Geiger-Muller 

counter. Bell (1963) found uranium by weight percent 

in marine limestones in Massachusetts, New York, and 

Vermont (0.0002, 0.0001, and 0.003 to 0.0014 percent by 

weight, respectively). Lucas (1964) developed and refined 

analytical techniques for measuring 222Rn content with 

alpha-counting cells. Barker and Johnson (1964) described 

the methods of determining 222Rn in water, including 

procedures for sample collection, preservation, and analysis 

with a Geiger-Muller counter. Barker and others (1965) 

described the methods of measuring total uranium in water, 

including procedures for sample collection, preservation, 

and analysis by fluorimetry. 

Tanner (1964a) described an investigation of 222Rn in 

the ground water near the Great Salt Lake in Utah and 

concluded that the 222Rn concentration was dependent 

mainly on the 226Ra content of the rock or soil near the well. 

The author suggests that 226Ra coprecipitated with ferric 

hydroxides near the well but also could be transported 

through subsurface fractures. Tanner (1964b) produced the 

first review of 222Rn migration in the ground. He concluded 

that the principal mechanism by which 222Rn was transported was by radioactive recoil during alpha decay, where 222Rn is ejected from the 226Ra parent into the fluid within 

the pore space in the rock or soil matrix. 

In 1964, the U.S. Public Health Service investigated 

the wells sampled previously by Grune and others (1960) in 

Maine. Results confirmed the high 222Rn concentrations but 

rejected the findings of high 226Ra and concluded that 222Rn, rather than 226Ra , was the major problem in Maine 

(D.C. Hoxie, Maine Division of Health Engineering, written commun., 1988). Hoxie (1966) reviewed methods for 

analyzing 222Rn in drinking water and developed a technique for analysis by gamma spectrometry. This method 

called for a 3.5-L (liter) sample, however, which proved to 

be bulky and difficult to transport. In 1966, the Maine 

Department of Human Services used an interim drinkingwater standard for 222Rn of 3,000 pCi/L in public supplies 

and 30,000 pCi/L for private water supplies in accordance 

with results of a literature survey that indicated ingestion to 

be the critical exposure pathway (D.C. Hoxie, Maine 

Division of Health Engineering, written commun., 1988). 

The U.S. Atomic Energy Commission (1969) 

described the findings of a preliminary reconnaissance for 

uranium in Connecticut, Maine, Massachusetts, New 

Hampshire, New Jersey, New York, and Vermont, for the 

period 1950-59. This document contains hundreds of data 

sheets that describe field locations, rock descriptions, radioactive content, and references to many outcrops across the 

Northeast. 

1971-79 

During the 1970's, several areas of radionuclide 

research were delineated-uranium-resource evaluation, 

radioactive-waste disposal, 222Rn as an earthquake predictor, and analytical techniques for measuring radionuclides 

in the environment. 

Uranium-Resource Exploration 

In 1974, the National Uranium Resource Evaluation 

program was started to make a comprehensive assesment of 

the uranium resources of the United States, in response to 

concern over the availability of uranium for nuclear-power 

generation. The evaluation included aeroradioactivity surveys, drilling and gamma-ray spectra logging, and hydrogeochemical surveys (U.S. Department of Energy, 1980). 

Tanner (1978), in a supplement to his earlier 222Rnmigration review (Tanner, 1964b), concluded that effective 

migration of 222Rn was directly related to the water content 

of the emanating solid and that meteorologic variables 

affect 222Rn transport in soil gases, where increased barometric pressure and precipitation decrease the exhalation of 222Rn in soil gas. This review also provided detailed 

references on 222Rn in mines, 222Rn from mill tailings, 222Rn emanation from lunar material, 222Rn in natural gas 

and petroleum, and geophysical applications of 222Rn 

measurements in the location of buried geologic structures. 

Gesell (1975), after reviewing 70 years of measurements, 

concluded that even though individual 222Rn measurements 

Radionuclides in the Northeastern United States and Southeastern Canada 197 
as high as 1 ,450 pCi/L have been found, the concentrations 

in natural gas in the United States average less than 100 

pCi/L. 

Radioactive-Waste Disposal 

Concern about methods of disposal of radioactive 

waste prompted a large research effort. Ferruccio (1975) 

proposed that the disposal of radioactive waste by mixing 

waste with tailings from salt-mine operations and storing 

them back in salt domes was practical. The topic of 

radioactive-waste disposal is too broad to address here, 

however, and is mentioned only for its historical context. 

Radon-222 as an Earthquake Indicator 

Radon-222 concentrations in ground water and soil 

gas near seismic zones have been studied to determine 

whether 222Rn is a reliable predictor of earthquakes. Teng 

and others (1975) conducted an extensive ground-water 

survey in California that included weekly measurements of 222Rn in well water near seismic zones and identified a 

relation between seismic activity and increased 222Rn concentrations in ground water before earthquakes. King 

(1977) set Track-Etch detectors in shallow-soil auger holes 

along active faults in California and noted increases in 222Rn concentrations in soil gas several weeks before 

earthquakes of magnitude 4 to 4. 6. 

Analytical Techniques 

Techniques for measuring radionuclides in water and 

air interested many scientists and health physicists in the 

1970's. Johnson (1971) described methods for measuring 

radium-228 e28Ra) in water that included procedures for 

sample collection, preservation, and analysis with a betaactivity counter and found 228Ra concentrations in natural 

stream water to range from 0.3 to 1. 7 pCi/L. Prichard and 

Gesell ( 1977) discussed the development of analytical 

techniques in liquid scintillation that led to relatively easy 

measurement of 222Rn and gross-alpha radiation in water 

samples. Hess and others (1973, 1978, 1979) researched 222Rn in the ground water in Maine through liquid scintillation techniques. 

Radionuclides in Water 

Radionuclides in water and the effects upon human 

health were studied in the 1970's. Suomela and Kahlos 

(1972) did one of the few investigations of human elimination of radioactivity after ingestion of 222Rn-rich water. 

Subjects were given a total dose of 222Rn equal to 60,000 

pCi/d (picocuries per day) in two or three portions, and, 

from this study a 222Rn dose equivalent of 240 to 440 mrem 

(millirems) per 1,000,000 pCi was derived. From this 

work, Suomela and Kahlos (1972) suggest that the maximum daily intake of 222Rn in drinking water should be 

198 Field Studies of Radon in Rocks, Soils, and Water 

100,000 pCi/d. Duncan and others (1976), in a paper 

describing 222Rn in potable water, concluded that the lungs 

are the critical exposure pathway for 222Rn and suggested 

that, from the increased lung cancer observed in uranium 

miners, the 222Rn standard for drinking water should be 

approximately 500 pCi/L. Partridge and others (1979) 

began to study the 222Rn release from water and concluded 

that between 5 and 99 percent of the 222Rn in water could be 

released during normal household activities. In 1978, the 

Environmental Protection Agency began to sample water 

from public supply systems across the Nation and used 

liquid scintilation techniques developed by Prichard and 

Gesell (1977) to identify the extent of 222Rn in public 

drinking-water supplies. 

In 1978 the Maine Department of Human Services, 

with grants made available by the Safe Drinking Water Act, 

funded the University of Maine to study 222Rn in ground 

water of Maine (D.C. Hoxie, Maine Division of Health 

Engineering, written commun., 1988). In 1979, the Maine 

Department of Human Services designed and built a prototype 222Rn removal unit for drinking water. The unit was 

based on the concept of spraying water several times to 

allow the release of 222Rn gas, which was vented outdoors 

(D.C. Hoxie, Maine Division of Health Engineering, written commun., 1988). 

Radon-222 in Indoor Air 

During this time, the occurrence of 222Rn in air began 

to interest many researchers, and in 1971 , preliminary 

results of studies of lung cancer in underground miners 

prompted the Federal Radiological Council to reduce the 

occupational exposure limit for 222Rn to 4 WL (working 

levels) per year with a maximum airborne concentration not 

to exceed 1 WL, where 1 WL= 200 pCi/L 222Rn (D.C. 

Hoxie, Maine Division of Health Engineering, written 

commun., 1988). The Environmental Protection Agency 

(1975) released preliminary results on 222Rn in homes built 

over phosphate mine tailings. Archer and others (1976) 

showed a relation between 222Rn exposure and lung cancer. 

1980 to Present 

Uranium-Resource Exploration 

In the 1980's the price of uranium decreased sharply, 

and as a result exploration for uranium declined. Duval 

(1983, 1987) analyzed the National Uranium Resource 

Evaluation data from the Middle Atlantic States and produced a color-enhanced map of uranium equivalence 

through a geographic information system. The map outlines 

some potential 222Rn problem areas, such as those in the 

Reading Prong in Pennsylvania and the coastal-plain sediments of New Jersey, which typically are low in radioactive 

content. Otton and others (1985) have continued to study 
uranium deposits in the surficial environment, including 

work on the 222Rn hazard associated with uranium deposits. 

Radioactive-Waste Disposal 

Interest in the disposal of radioactive waste has led to 

many avenues of research. Dinwiddie and Trask ( 1987) 

compiled several papers on all aspects of radioactive-waste 

disposal. Weeks (1987) investigated field tests for flow and 

transport in unsaturated media and concluded that gaseous 

diffusion from depth may be an important process relating 

to the transport of stored radioactive waste. Cleveland 

( 1987) investigated transuranic elements in ground water 

and found that ground water from basalt in Washington and 

alluvial deposits in Arizona could leach plutonium from 

borosilicate glass. Kipp ( 1987) modeled radionuclide transport in ground water and concluded that a heat-andtransport model could accurately simulate the transport of 

radionuclides in ground water. 

Radon-222 as an Earthquake Indicator 

Research into the use of 222Rn in ground water as a 

predictor of earthquake activity has continued. Thomas and 

Koyanagi ( 1986) investigated the relation between the 

concentration of 222Rn in soil gas and seismic and volcanic 

activity of Kilauea Volcano, Hawaii, and found that 

changes in 222Rn in the ground were related to the monthly 

eruptive cycle of Kilauea. Fleischer and Mogro-Campero 

( 1985) compared the concentration of 222Rn in soil gas in 

Albany, N.Y. , with 222Rn in soil gas in Alaska during 

periods of seismic activity and concluded that the concentration of 222Rn sometimes increased before activity and 

sometimes decreased. King and Wakita (1981) investigated 222Rn concentrations in ground water from an artesian well 

and related changes in concentration to seismic activity. 

Analytical Techniques 

Advances into analytical techniques for measuring 

radioactivity in water and air have continued during the 

1980's. Yang (1984, 1987) developed a technique that 

bubbles helium through a water sample to collect 222Rn in 

a Lucas or alpha-scintillation counting cell. Cothern and 

others ( 1984) investigated the measurement of calibration 

standards, quality assurance, and data analysis for radionuclides in environmental samples performed by the Environmental Protection Agency and contract laboratories. They 

concluded that 80 to 90 percent of the laboratories doing 

water analyses produced results that were within control 

limits, although they noted some difficulties in determination of 228Ra. Participating laboratories also had difficulty 

in determining beta radiation in air samples. 

Table 24. Natural radioactivity in public water supplies in 

the United States 

Radionuclide 

Number of public M t t' ( C"fl) supplies sampled ean concen ra 10n p 1 

Arithmetic Geometric 

Public water supplies, both surface water and ground water1 

Gross alpha radioactivity . . 2,535 1.8 0.6 

Gross beta radioactivity... 2,515 3.4 2.1 

Total uranium........... 344 5.1 1.9 

Radium-226 . . . . . . . . . . . . 386 1.6 .6 

Radium-228 . . . . . . . . . . . . 100 3.5 2.3 

Total radium............ 91 

Radon-222 . . . . . . . . . . . . . 2,520 

Ground-water supplies2 

Gross alpha radioactivity.. 2,510 

Gross beta radioactivity. . . 2,510 

Uranium-234. . . . . . . . . . . . 362 

Uranium-238............ 362 

Total uranium. . . . . . . . . . . 362 

Radium-226 . . . . . . . . . . . . 403 

Radium-228 . . . . . . . . . . . . 107 

Total radium . . . . . . . . . . . . 97 

Radon-222 . . . . . . . . . . . . . 2,457 

1

Data from Horton, 1983. 2

Data from Horton, 1985. 

Radionuclides in Water 

8.5 

340 

1.9 

3.4 

3.3 

1.7 

5.1 

1.7 

3.6 

8.5 

352.8 

7.6 

100 

.5 

2.0 

1.1 

.4 

1.5 

.6 

2.1 

7.6 

86.6 

Research during the 1980's expanded to address the 

environmental sources of radionuclides, especially 222Rn, 

and the health effects of both ingestion and inhalation of 

radionuclides. In 1980, the Maine Department of Human 

Services, in conjuction with other New England States, 

reviewed current literature and calculated the exposures that 

result from ingesting 222Rn with drinking water and suggested a drinking-water standard of about 50,000 pCi/L 

(D.C. Hoxie, Maine Division of Health Engineering, written commun., 1988). Horton (1983), through an Environmental Protection Agency study begun in 1980, measured 

1 h d b d. . l . 226 22sR gross-a p a an - eta ra mtwn, tota uramum, · a, 

and 222Rn in public water systems across the Nation that 

serve 1 ,000 people or more; results are summarized in table 

24. This work prompted researchers to make a closer 

examination of radionuclides in private homes and private 

water supplies. Horton (1985) presented an update of the 

data collected from the 1980 study that focused on groundwater supplies serving 1 ,000 people or more; these results 

also are given in table 24. 

A summary of Horton's ( 1985) data on radionuclides 

in ground water in New England and New York is presented 

in table 25. Horton ( 1983, 1985) showed that ground water 

from these States generally has lower-than-average concentrations of gross-alpha and gross-beta radiation, total uranium, and 226Ra. Although Horton (1985) gives no data for 

228Ra for public ground-water supplies in the Northeast, the 

national arithmetic means for total radium and 228Ra are 8. 5 

and 3.6 pCi/L, respectively. Concentrations of 222Rn in 

Radionuclides in the Northeastern United States and Southeastern Canada 199 
Table 25. Radionuclide concentrations in public ground-water supplies in New England and New York 

[Values are in picocuries per liter; -, no data; data from Horton, 1985] 

Gross alpha Gross beta Radium-226 Radon-222 

State Arithmetic Geometric No. of Arithmetic Geometric No. of Arithmetic Geometric No. of Arithmetic Geometric No. of 

mean mean sites mean mean sites mean mean sites mean mean sites 

Maine ................. 1.3 0.4 25 2.2 1.7 25 0.6 0.3 2 0 

New Hampshire ......... .4 .2 26 2.0 1.6 26 .4 .4 1,388 944 26 

Vermont ............... .7 .3 11 1.3 1.2 11 1.0 1.0 618 556 11 

Massachusetts ........... .3 .1 100 1.9 1.3 100 .2 .2 790 507 100 

Rhode Island ............ .4 .2 30* 1.6 1.2 30* .1 .1 1 1,376 1,140 30* 

Connecticut ............. 0 0 0 0 

New York .............. .3 .2 132 1.7 1.3 132 .I .1 171 43 130 

United States total ..... 1.9 .5 2,510 3.4 2.0 2,510 1.7 .6 403 353 87 2,457 

* Represents 30 individual wells but only 11 public water supplies. 

Table 26. Total uranium and radon-222 concentrations in water supplies in New England and New York 

[Values are in picocuries per liter; -, no data; data from Hess and others, 1985b] 

Total uranium Radon-222 

Private well Public supply1 Public ground water Public surface water State Surface water Ground water Domestic water1 Geometric No. of Geometric No. of Geometric No. of Geometric No. of 

Maine ................. 0.010 0.035 0.035 

New Hampshire ......... .010 .035 .035 

Vermont ............... .010 .010 .010 

Massachusetts . . . . . . . . . . . .010 .010 .010 

Rhode Island ............ .075 .075 .075 

Connecticut ............. .010 .075 .035 

New York .............. .010 .035 .035 

United States total ..... 

1 May be a blend of surface and ground waters. 

ground water are well above the national average except in 

New York. Hess and others (1985b) compiled nationwide 

data for total uranium and 222Rn in public surface-water and 

ground-water supplies and private supplies; table 26 presents their data for New England and New York. Hess and 

others (1985b) show that, in general, private well water in 

these States has higher concentrations of total uranium and 222Rn than public ground-water or surface-water supplies. 

Radon-222 in Indoor Air 

The 1980's were a period of intensive research into 

the occurrence of 222Rn in outdoor and indoor air. Gesell 

(1983) concluded that the average outdoor 222Rn concentration across the United States ranged from 0.1 to 0.4 

pCi/L and noted that the maximum soil gas concentration 

occurs at sunrise and the minimum in the afternoon. George 

and others (1983) compared indoor 222Rn concentrations in 

solar-energy-efficient homes with those in conventional 

homes. The indoor 222Rn concentrations in the solar homes 

in New Hampshire, Connecticut, and New York ranged 

from 5. 0 to 0. 3 pCi/L, and the associated 226Ra in the soils 

ranged from 2.5 to 0.15 pCi/g (picocuries per gram). Their 

200 Field Studies of Radon in Rocks, Soils, and Water 

mean sites mean sites 

7,000 24 990 71 

1,400 18 9 12 

210 23 840 4 

1,000 8 7 2 

6,500 69 5,200 6 

0 0 

1,500 4 34 20 

920 434 68 224 

mean 

940 

660 

500 

2,400 

52 

130 

sites 

0 

52 

71 

212 

575 

0 

292 

6,298 

mean sites 

0 

6 

13 16 

38 2 

10 

0 

1 

131 

main conclusion, however, was that indoor 222Rn concentrations in solar-energy-efficient homes did not differ from 

those in conventional homes. Nero and others (1986) 

concluded from a study of the distribution of 222Rn (ranging 

from grab samples to 1-year samples) in 1,377 homes 

across the United States that the arithmetic mean was 1.5 

pCi/L, and the mean values for central Maine and New 

York were 2. 97 and 1.57 pCi/L, respectively, both of which 

are above the national average. 

MAINE 

Previous Work 

The first studies of natural radioactivity in Maine 

began during the late 1950's and early 1960's as part of a 

regional uranium-exploration program; results indicated 

several areas of higher-than-expected background radiation 

throughout the State. Ground measurements of gross radioactivity by Geiger-counter surveys across Maine and New 

Hampshire by Nelson and Narten (1951) indicated that the 
granites in Maine contain 0.002 to 0.003 percent uranium 

by weight. Grune and others (1960) and Smith and others 

(1961) began the first study of radioactivity in the ground 

water and surface water of Maine and found high levels of 222Rn gas in a tank of well water near Raymond (fig. 78). 

This study involved 500 measurements near Raymond (fig. 

78). Lowder and others (1963) made an environmental 

radiation study in northern New England, including Maine 

(reported by Brutsaert and others, 1981), and Hoxie (1966) 

followed up with more specific measurements of 222Rn in 

Maine's ground water. Hess and others (1973) made a 

radioisotope investigation near Wiscasset (fig. 78), and 

Duncan and others (1976) stated that some of the highest 222Rn concentrations in water in the United States were in 

Maine. Hess and others (1979, p. 4) note that one purpose 

of their research was to determine whether the high cancer 

rates in Maine could be correlated with high concentrations 

of 222Rn. Their research included measurements of 222Rn in 

water and air, correlation of 222Rn with differing geologic 

terranes, collection of data on cancers, and statistical testing 

of the data to determine whether the correlation between 222Rn and cancer was significant. Otton and others (1980) 

investigated anomalous total uranium and thorium concentrations in the rocks of the Tomah Mountain area in eastern 

Maine (fig. 78). 

Brutsaert and others ( 1981) measured the concentration of 222Rn in ground water from granites, calcareous 

rocks, pelitic rocks, and quartz-rich rocks in Maine and 

attempted to correlate 222Rn concentrations in ground water 

with more easily measurable characteristics and chemical 

constituents. Samples from wells completed in granite had 

the highest 222Rn concentrations, and the concentrations 

varied inversely with well yield. The concentrations indicated an inverse correlation with sodium, but road salting 

may have been a factor. Hess and others (1981) investigated 222Rn, 226Ra, and total uranium in the air and the waters of 

Maine expanding on the work by Hess and others ( 1979). 

Weiffenbach (1982) followed up with a report on 222Rn in 

water and air with emphasis on health risk and control. 

Lowry ( 1983) and Lowry and Brandow ( 1985) began 

research into the removal of 222Rn from water by granularactivated carbon filters. Lowry and others (1987) have been 

applying the technological developments to Maine homes 

whose private water supplies have extremely high 222Rn 

concentrations (1.1 million pCi/L). Granular-activated carbon was effective in removing 99 percent of the 222Rn, and 

uranium was removed with an ion-exchange resin. The 

removal of 222Rn and uranium from the water led to an 

almost total removal of 222Rn in indoor air at the home that 

had a ground-water concentration of 1.1 million pCi/L of 222Rn. Recent investigations (Ground Water Monitor 

Review, 1988; D.C. Hoxie, Maine Division of Health 

Engineering, written commun., 1988) suggest that a 

buildup of radioactive lead-210 e10Pb) in granularactivated carbon filters may be of environmental concern as 

well as the disposal of the filters, which could be considered 

low-level radioactive waste. 

Hess and others (1985a) investigated the concentration of 222Rn in indoor air with alpha Track-Etch detectors 

as a function of the energy efficiency or "tightness" of 

homes in Maine. Hess and others (1986) made a detailed 

d f h 'b . f 2 stu y o t e contn ut10n o ""R 

~~ n m . water """R . to --~ n m 

indoor air and concluded that the 222Rn level due to water 

use could range from 0 to 36 percent of the total 222Rn in 

indoor air. Lanctot ( 1985) made a preliminary analysis of 

data from a cooperative epidemiological study of 222Rn and 

its relation to cancer in Maine. Lanctot and others ( 1985) 

combined the work of Hess and others ( 1979) with that of 

Lanctot (1985) and determined that 222Rn concentrations in 

ground water varied as a function of aquifer hydraulics and 

uranium geochemistry within the aquifer. 

The Cooperative Extension Service of the University 

of Maine at Orono (U.S. Department of Agriculture, 1986) 

published a summary of health risks and control measures 

for radon-222 in water and air that describes the occurrence, 

distribution, and remediation of 222Rn in Maine. 

Distribution and Concentration of Radionudides 

in Ground Water 

Most of the data from the publications just referred to 

relate to 222Rn in ground water. Data on 222Rn and other 

radionuclides in samples collected in Maine during national 

studies by Hess and others ( 1985b) and Horton ( 1983, 

1985) are included in tables 25 and 26, which also give 

national averages for comparison. Michel and Jordana 

(1987) list a range of 500 to more than 10,000 pCi/L for 222Rn and 1 to 5 pCi/L for 226Ra and total uranium in the 

drinking water from selected counties of Maine. Table 27 

includes concentrations of gross-beta radioactivity, total 

radium, and uranium in water from selected wells in Maine. 

It is evident from work done in Maine (Hess and others, 

1979, 1981) and reported by Lanctot and others ( 1985) that 

ground water from most, if not all, of the rock formations in 

Maine have been sampled at least once. Radon-222 concentrations in water from several types of aquifers are given 

in table 28. 

Ground-Water Availability and Rate of 

Withdrawal 

Data on ground-water withdrawals (Maloney and 

Cowing, 1985) indicate the percentage of the population 

that is exposed to potential health risk from radionuclides in 

the water supply of Maine. The crystalline-bedrock aquifers 

of Maine are the most widely used for water supply and also 

have the highest concentrations of 222Rn. Well yields from 

stratified drift aquifers generally range from less than 1 to 

Radionuclides in the Northeastern United States and Southeastern Canada 201 
/l _.,--r-'' ,I ~-- \ 

I AROOSTOOK I 

:~---l- QUEBEC NEW 

BRUNSWICK 

/ i I -l 

5 ~ ! ll 

! JPISCATAQUI~ 

(\;OMERSET? I - ~, .-'-{''-" \ 1 \ PENOBSCOT ·T.?mah 

I 1 ~ \ _ _f ~ lt

ANKLIN L w-r ( ~WASHINGTON\ 

I I ,.. \ \ 

~I \ \_ S~'-- ~ 0 X F 0 R ::----. s:.. .--;; E BE cj W A L 0 0 

:1 - rl t •vassalboro 

4 IAUgus '~ fl ~I ANOROSCOGf. 1 1- " V J:i I GIN --1- I d' 1-0 \J ;~, J # \ + ~ ~Q 

~ ~ Wiscaaset -v l) e 0 (\ 

w ~~· oc Z 1} eRaymon~ SAGADAHOC ·C 

"~1-o~lf'iJO o(\'' 

I ' S. Windham r>-'' l YORK 

50 

Mt. 

0 50 100 150 Kilometers 

Figure 78. Locations of Maine sites mentioned in text. (Scale 1 :3,168,000; base from 

Adamik, 1984.) 

1 ,000 gal/min (gallons per minute); yields from bedrock 

aquifers range from 2 to 30 gal/min. The 642,000 residents 

of Maine that rely on ground water as a drinking supply, 45 

percent of which are on small or private systems, withdraw 

46 Mgal/d (million gallons per day). 

Radon in Indoor Air 

Hess and others (1979, p. 80) made a series of 

24-hour tests of 222Rn in indoor air in 10 living rooms and 

202 Field Studies of Radon in Rocks, Soils, and Water 

1 school with a Wrenn-Spitz radon detector and obtained an 

average value of2.67 pCi/L. Hess and others (1985b) report 

an average of 3.0 pCi/L for indoor air in Maine. Work by 

Hess and others (1985a) indicates that measurements need 

to be made for 1 year to account for seasonal variations in 222Rn concentration in indoor air. Hess and others ( 1986) 

note that degassing of 222Rn from tap water resulted in 

spikes in indoor air concentrations during peak water-use 

periods. 
Table 27. Geohydrologic data and concentrations of radium and uranium in water samples from wells in Maine 

[Data from Scott and Barker (1962); locations shown in fig. 78; pCi/L, picocuries per liter; gal/min, gallons per minute] 

Location Geohydrologic data Concentration (pCi/L) 

Water- Well yield Date of Gross-beta Town County bearing Radium Uranium1 

unit (gal/min) collection activity 

Vassalboro ......... Kennebec Schist 8 03-27-57 <5 0.01 0.07 

Augusta ............ Kennebec Sand and gravel 1,000 03-27-57 <5 .1 .54 

South Windham .... Cumberland Granite 10 03-27-57 7 3.3 7.48 

1 Converted from micrograms per liter (~giL) by multiplying by 0.68 and assuming that all activity is due to uranium and that uranium is in secular 

equilibrium. 

Table 28. Radon-222 concentrations in Maine ground 

water, by aquifer type 

[Dashes indicate no data; concentrations are in picocuries per liter] 

Bedrock 

Igneous 1 

Aquifer 

material 

granite ................. . 

volcanics ............... . 

Metamorphic 1 

low-grade .............. . 

medium-grade .......... . 

high-grade .............. . 

Sedimentary 1 

calcareous mixed 

sandstone .............. . 

pelites .................. . 

sulfidic carbonaceous 

pelites ................. . 

limestone ............... . 

Interbedded 

sandstone and shale ..... . 

limestone and shale ..... . 

All granites2 ............. . 

Metamorphics2 

low-grade .............. . 

high-grade .............. . 

Granites3 ••••••••••••••••• 

Metamorphics3 •••••••••••• 

Unconsolidated sediments4 

dug wells ............... . 

Springs ................... . 

1

Lanctot (1985). 

Number Ra~on-2~ concentration 

Anthmet1c . of samples mean Max1mum 

114 15,008 151,182 

21 7,395 46,103 

95 2,111 18,115 

76 4,093 46,103 

102 7,059 65,656 

99 3,803 36,782 

10 6,372 40,069 

24 4,431 18,115 

13 8,504 37,424 

65 4,998 65,656 

30 1,908 14,243 

136 22,100 

56 1,100 

35 13,630 

84 93,300 

44 58,200 

46 1,432 

22 3,705 

2

Hess and others (1979), as reported by Hall and others (1985, p. 

90). 3

Smith and others (1961), as reported by Hall and others (1985, p. 

90). 4

Bogdan and others (1987). 

A recent study of indoor air in 1 ,500 homes in Maine 

by alpha Track-Etch detectors (D.C. Hoxie, Maine Division 

of Health Engeering, written commun., 1988) obtained an 

arithmetic mean of 4.87 pCi/L and a geometric mean of 

1.80 pCi/L for 222Rn. The highest value recorded was 

1,212.46 pCi/L. 

NEW HAMPSHIRE 

Previous Work 

The first studies of natural radioactivity in New 

Hampshire were begun in the early 1950's as ground 

measurements of gross radioactivity by McKeown (1951), 

who found that the uranium content of rocks in the State 

ranged from 0.002 to 0.003 percent by weight. Smith and 

others (1961) reported on natural radioactivity in water from 

selected wells in New Hampshire. Lyons (1964) studied the 

distribution of uranium and thorium in the Lower Devonian 

plutonic rocks in New Hampshire and reported content 

ranging from 0.6 to 39 ppm (parts per million) uranium and 

2.8 to 57 ppm thorium. He also reported that, in these 

rocks, most of the uranium was concentrated on grain 

boundaries and in interstitial spaces, and not necessarily 

within accessory minerals. Butler (1975) made a geochemical study of uranium and thorium in rocks of the White 

Mountain plutonic series (now designated White Mountain 

Plutonic-Volcanic Suite) through chemical and spectrographic techniques. Boudette ( 1977) investigated the uranium potential of a two-mica granite. Hoisington (1977) 

studied the uranium and thorium distribution in the Conway 

Granite. Bothner (1978) described selected uranium and 

thorium occurrences in New Hampshire. Page (1980) published a guide to prospecting for uranium and thorium in 

New Hampshire. 

Donahue ( 1984) investigated the hydrogeologic factors that influence 222Rn in the ground water of southeastern 

New Hampshire. Hall and others (1985) made a general 

investigation of 222Rn in the ground waters of New Hampshire from 1982 to 1985; results show that ground water 

from a two-mica granite has the highest mean concentration 

of 222Rn in the State (45,000 pCi/L). Observations by 

Brutsaert and others ( 1981) that 222Rn concentrations are 

Radionuclides in the Northeastern United States and Southeastern Canada 203 
~-~ 

' ' \; 

'~ I 

coos \ 

' ' -L_\::_ur-1 I I 

G RA F TON ( Nor~h Conway 

\ \ 

_ _..1 \ 

\ CARROLL 

. ,, ' Plymouth ,---J , l 

J ", 

-L,:f'-<,;:KNAP\~ (MERRIMACK '-....... \ 

SULLIVAN/, ""'-..,J e Rochester 

=--~ ~ 

\ ConcordEpso: 

~\__ (!) I 

f'.--• 'L_ ~ STRAFFORO 

1 ~-~ Deerfield 

I HILLSBOROUGH(' .Hampton 

\ ROCKINGHAM 

CHESHIRE \ , 

\ . \. Greenville ----- -..l..--·--

MASS. 

0 25 50Miles 

0 25 50 Kilometers 

Figure 79. Locations of New Hampshire sites mentioned in text. (Scale 1 :2,112,000; base 

from Cotton and Hammond, 1985a.) 

inversely related to sodium, chloride, and iron content were 

generally upheld by Hall and others (1985), who present 

data indicating that the inverse proportionality between 222Rn concentration and well yield is not absolute (Hall and 

others,1985, p. 96). 

Campisano and Hall (1986), Campisano (1987), 

Wathen (1986), and Wathen and Hall (1986) present 

additional results of studies of 222Rn in ground water near 

Deerfield, in southeastern New Hampshire (fig. 79), and 

204 Field Studies of Radon in Rocks, Soils, and Water 

the two-mica granite. Hall and others (1987) summarize the 

geologic controls on 222Rn occurrence in New England. A 

map compiled for the Environmental Protection Agency by 

Olszewski and Boudette (1986), based on a generalized 

bedrock geologic map of New England, emphasizes uranium distribution in major rock units as an indicator of 222Rn occurrence. Cameron and others (1986) studied 

geochemical controls on uranium in selected peat deposits 

in New Hampshire and Vermont. 
Table 29. Geohydrologic data and concentrations of radium and uranium in water samples from wells and springs in New 

Hampshire 

[Data from Scott and Barker (1962); locations shown in fig. 79; <, less then; pCi/L, picocuries per liter; gal/min, gallons per minute] 

Location Geohydrologic data Concentration (pCi/L) 

Water- Well yield Date of Gross-beta Town County bearing Radium Uranium1 

unit (gal/min) collection activity 

North Conway ...... Carroll Sand and gravel 300 04--02-57 <5 0.1 0.1 

Plymouth ........... Grafton Alluvium 350 10-10-55 <5 .1 .07 

Epsom ............. Merrimack Littleton Formation 15 09-28-54 <5 .1 .2 

Rochester .......... Strafford Littleton Formation 7.5 10-20-55 <5 .5 .3 

Greenville .......... Hillsborough Littleton Formation 2-15 04--03-57 <10 .1 .2 

Hampton ........... Rockingham Sand and gravel 460 09-28-54 <5 .1 .4 

1

Converted from micrograms per liter (f,Lg/L) by multiplying by 0.68 and assuming that all activity is due to uranium and that uranium is in secular 

equilibrium. 

Wathen (1987) studied the siting of uranium and 222Rn activity in ground water from a two-mica granite 

through autoradiographic techniques and whole-rock analyses for uranium and demonstrated that uranium and 226Ra 

are found as grain coatings, as suggested by Lyons (1964). 

Wathen (1987) also found that, although uranium in solution was measured at concentrations as high as 100 J.,Lg/L 

(micrograms per liter), it was not proportional to 222Rn 

concentration. Wathen (1987, p. 41) suggests that high 222Rn concentrations in water can be correlated with uranium localized on grain borders in the rock near the well. 

Distribution and Concentration of Radionuclides 

in Ground Water 

Data on 222Rn and other radionuclides in samples 

collected in New Hampshire during national studies by Hess 

and others ( 1985b) and Horton ( 1983, 1985) are included in 

tables 25 and 26, which also give national averages for 

comparison. Michel and Jordana (1987) list a range of 0 to 

3 pCi/L for gross-alpha radiation, 1,000 to more than 

10,000 pCi/L for 222Rn, and 1 to 5 pCi/L for 226Ra and total 

uranium in the drinking water from selected counties of 

New Hampshire. Table 29 includes concentrations of grossbeta radioactivity, total radium, and uranium in water from 

selected wells in New Hampshire. Hall and others (1985) 

report that ground water from most, if not all, of the rock 

formations in New Hampshire have been sampled at least 

once. Radon-222 concentrations in water from several types 

of aquifers are given in table 30. 

Ground-Water Availability and Rate of 

Withdrawal 

Data on ground water withdrawals (Cotton and Hammond, 1985a) indicate the percentage of the population that 

is exposed to potential health risk from radionuclides in the 

Table 30. Radon-222 concentrations in New Hampshire 

ground water, by formation 

[-, no data; concentrations are in picocuries per liter] 

Formation 

Number Radon-222 concentration 

Arithmetic of samples 

Kittery1 •••••••••••••• 

Eliot 1 •••••••••••••••• 

Berwick1 •••...••.... 

Littleton 1 ••••..•••... 

Exeter Diorite 1 ••••... 

Quartz diorite 1 ••••••• 

Quartz monzonite 1 •..• 

Two-mica granite 1 •••. 

Conway Granite 1 ••••• 

Conway Granite2 ••••• 

Fitchburg Granite3 ...• 

1

Hall and others (1985). 2

Hess and others (1979). 3

Smith and others (1961). 

10 

12 

20 

11 

10 

3 

14 

11 

13 

2 

8 

mean 

1,900 

2,520 

11,900 

10,600 

1,800 

3,570 

34,000 

45,100 

12,200 

32,540 

284,000 

Range 

652-3,880 

784-5,470 

1 '360-29 ,500 

913-44,500 

744-2,800 

1' 140-8,300 

4,110-105,000 

613-258,000 

342-70,300 

water supply of New Hampshire. The major aquifers in 

New Hampshire are stratified-drift deposits, which have 

well yields ranging from 100 to 500 gal/min. The 

crystalline-bedrock aquifers of New Hampshire are widely 

used for water supply and also have the highest concentrations of 222Rn. Well yields from bedrock aquifers generally 

range from 2 to 30 gal/min. The 550,000 residents of New 

Hampshire who rely on ground water as a drinking supply, 

17 percent of which are on small or private systems, 

withdraw 52 Mgal/d. 

Radon in Indoor Air 

The focus of radionuclide studies in New Hampshire 

has been on 222Rn in ground water; research on 222Rn in air 

has been less extensive. Results from 635 nonrandom, 

short-term screening tests that used charcoal-canister-type 

Radionuclides in the Northeastern United States and Southeastern Canada 205 
Table 31. Concentrations of radon-222 and gross-alpha radiation in drinking-water systems in Vermont 

[Data from Manning and Ladue (1986); concentrations are in picocuries per liter] 

Source 

(formation) 

Precambrian core of Green Mountains 

Granites, gneiss, andesites, quartzite .................... . 

Metamorphic 

Ottaquechee-greenstone and serpentine ................. . 

Metasedimentary rocks 

Waits River, Gile Mountain, Missisquoi ................. . 

Cambrian sedimentary rocks 

Pinnacle, Underhill, Hazen Notch ....................... . 

Cambrian clastic rocks 

Dalton, Dunham, Monkton, Winooski, Saxe Brook ....... . 

Ordovician black shales 

Stony Point, Iberville, Hathaway ........................ . 

Carbonate rocks 

Beekmantown Group, Chazy Group ..................... . 

Unconsolidated sediment .................................... . 

Unspecified springs ......................................... . 

detectors indicated an average concentration of 6. 7 pCi/L of 222Rn in indoor air of basements (Chris Pirie, New Hampshire Division of Public Health Service, oral commun., 

1988). This is not a value from a statistical analysis of the 

data; rather, it is used to represent an overall "worst-case" 

value for the State. The New Hampshire Division of Public 

Health Services began a study of 2,200 randomly selected 

homes during the winter of 1988 and intends to use the 

results to establish an average level for 222Rn in indoor air. 

VERMONT 

Previous Work 

The first study of natural radioactivity in Vermont 

was a series of ground measurements of gross radioactivity 

by McKeown (1951). Additional research did not begin 

until the late 1970's, when McHone and Wagner (1980) 

began general uranium exploration research. Dorsey and 

Vanecek (1983) and Vanecek and Dorsey (1983a,b), in a 

series of geologic and radiometric surveys in Vermont, 

focused primarily on general measurements of radioactivity 

rather than 222Rn in air or water. 

Manning and Ladue (1986) of the Vermont Department of Health measured 222Rn concentrations in 689 

samples of drinking water from 366 sites. All samples were 

analyzed for 222Rn through liquid-scintillation techniques, 

and data for gross-alpha activity also were collected. 

The University of Vermont's Department of Natural 

Resources has been developing a geographic information 

system for analyzing radionuclide data. The system entails 

the digitizing of geographic, geologic, and radionuclide 

206 Field Studies of Radon in Rocks, Soils, and Water 

Number Radon-222 

of homes Range Arithmetic Gross alpha mean 

18 107-3,662 825 4.0 

13 26-2,282 931 1.1 

86 0-5,597 1,196 1.7 

54 48-6,159 1,127 1.1 

27 216-2,265 814 4.2 

2 111-2,332 1,221 3.5 

19 115-1,893 635 1.7 

45 31-2,038 611 .8 

25 50-1,824 733 .7 

data, which can then be manipulated by computer techniques and graphically displayed. 

Distribution and Concentration of Radionuclides 

in Ground Water 

Data on 222Rn and other radionuclides in samples 

collected in Vermont during national studies by Hess and 

others ( 1985b) and Horton ( 1983, 1985) are included in 

tables 25 and 26, which also give national averages for 

comparison. Michel and Jordana (1987) list a range of 100 

to 1 ,000 pCi/L for 222Rn and 1 to 5 pCi/L for 226Ra and total 

uranium in the drinking water from selected counties of 

Vermont. Manning and Ladue (1986) sampled ground 

water from most, if not all, of the water-bearing formations 

in Vermont; results are summarized in table 31. The higest 

concentration of 222Rn in drinking water was 14,400 pCi/L 

in a well completed in the Precambrian core rocks of the 

Green Mountains near Ludlow (fig. 80). 

Ground-Water Availability and Rate of 

Withdrawal 

Data on ground-water withdrawals (Cotton and Hammond, 1985b) indicate the percentage of the population that 

is exposed to potential health risk from radionuclides in the 

water supply of Vermont. The major aquifers in Vermont 

are stratified-drift deposits, which generally have well 

yields of 30 to 400 gal/min. The crystalline-bedrock aquifers of Vermont are widely used for water supply and may 

have the highest concentrations of 222Rn. The 275,000 
QUEBEC 

GRANot)f ISLE- FRANKLIN \ I ORLEANS --~-I 

-~ }ESSEX 

B i'"- r { ?' < 

\ 

..... -<:AMOILLE.... I I 

c HITTENDENS fi:.L E DON I A> 

< ... · ..../"-.....,' ') \ 

I I + 

\ _..1\ r c:,~...0 t:\Montpelie-r - \ + <!I 

\ / r-I'-- ~ I --r ORANGE 

- (y ~ - _r- \/' -.... --- - { WIN 0 SORRUTLANO) 

I 

NEW YORK ~ 1 ,. Ludlow 

z -r--- I 

~r 

J

: ~ [_

1

WIND HAM 

ID I 

\. _ __j_ --

MASS. 

NEW HAMPSHIRE 

0 25 50Miles 

0 25 50Kilometers 

Figure 80. Locations of Vermont sites mentioned in text. (Scale 1:1 ,900,800; base from 

Cotton and Hammond, 1985b.) 

residents of Vermont that rely on ground water as a drinking 

supply, 32 percent of which use small or private systems, 

withdraw 34 Mgal/d. 

Radon in Indoor Air 

The focus of radionuclide research in Vermont has 

been on 222Rn in ground water; research on 222Rn in air has 

been less extensive. The home that had the highest 222Rn 

concentration in drinking water (14,400 pCi/L) had indoorair concentrations of 0.6 to 2.5 pCi/L (Manning and Ladue, 

1986). Further information on 222Rn in indoor air in 

Vermont can be obtained through direct inquiry from the 

Vermont Department of Health, Division of Occupational 

and Radiological Health. 

Radionuclides in the Northeastern United States and Southeastern Canada 207 
MASSACHUSETTS 

Previous Work 

The first studies of natural radioactivity in Massachusetts began in the early 1950's with ground measurements 

of gross radioactivity by Johnson (1951), who described a 

region of central Massachusetts as part of the "Central New 

England Radioactive Province." Popenoe ( 1966) compared 

aeroradioactivity surveys with the geology of southwestern 

Massachusetts. Fisenne and others ( 1984) reported on 

abundances of 234'

238U, 226Ra, and 210Pb in sandy soils of 

North Eastham (fig. 81). These works focused primarily on 

general measurements of radioactivity rather than 222Rn in 

water or air. 

Davis and others (1987) measured the bulk 222Rn 

emanation rates of several granites in Massachusetts 

through high resolution, gamma-ray spectroscopy. They 

collected and analyzed samples of Andover, Cape Ann, 

Chelmsford, Milford, Peabody Granite, Sharpners Pond 

Diorite, the Concord Granite from New Hampshire, and the 

Rockville Granite from Minnesota. Samples were either cut 

into slabs of variable thickness or ground into distinct 

particle-size fractions ranging from less than 0.5 to 20 em 

(centimeters) in diameter. The gamma-ray spectrum of each 

sample was measured and used to calculate both uranium 

concentration and percent loss of 222Rn for each sample. 

Results indicate that 222Rn emanation increases with 

decreasing particle size. Davis and Hon (1988) have 

expanded that work by applying empirical data on 222Rn 

emanation to predictive models for unsupported 222Rn in the 

environment. 

Distribution and Concentration of Radionuclides 

in Ground Water 

Data on 222Rn and other radionuclides in samples 

collected in Massachusetts during national studies by Hess 

and others (1985b) and Horton (1983, 1985) are included in 

tables 25 and 26, which also give national averages for 

comparison. Michel and Jordana (1987) list a range of 100 

to 10,000 pCi/L for 222Rn and 1 to 5 pCi/L for 226Ra and 

total uranium in the drinking water from selected counties 

of Massachusetts. Table 32 includes concentrations of 

gross-beta radiation, total radium, and uranium in water 

from selected wells in Massachusetts. 

Although recent data on 222Rn and other radionuclides in ground water are scant, 222Rn concentrations in 

water sampled from five wells in the Ayer Granite range 

from 2,000 to 5,400 pCi/L, and three other samples from 

wells in the Ayer Granite, tested by homeowners, had 222Rn 

concentrations of93,000, 67,000, and 61,000 pCi/L (James 

Persky, U.S. Geological Survey, written commun., 1988). 

208 Field Studies of Radon in Rocks, Soils, and Water 

Ground-Water Availability and Rate of 

Withdrawal 

Data on ground water withdrawals (Frimpter, 1985) 

indicate the percentage of the population that is exposed to 

potential health risk from radionuclides in the water supply. 

The major aquifers in Massachusetts are stratified-drift 

deposits that have well yields generally ranging from 100 to 

1 ,000 gal/min. The crystalline-bedrock aquifers of Massachusetts are widely used for water supply and may have the 

highest concentrations of 222Rn. Well yields from bedrock 

aquifers range from 1 to 100 gal/min. The 1,900,000 

residents of Massachusetts who rely on ground water as a 

drinking supply, 7 percent of which rely on small or private 

systems, withdraw 190 Mgal/d. 

Radon in Indoor Air 

Information on 222Rn in indoor air in Massachusetts is 

limited and can be obtained through direct inquiry to the 

Massachusetts Department of Public Health. Nero (1983) 

investigated 222Rn in seven single family residences in 

Boston (fig. 81), and found the average for grab samples in 

the living area to be 0.07 pCi/L. Although many indoor-air 

measurements have been made in Massachusetts (William 

Bell, Massachusetts Department of Public Health, oral 

commun., 1988), the sites generally have been selected on 

the basis of socioeconomic factors and do not represent the 

State in general. 

RHODE ISLAND 

Previous Work 

The first studies of natural radioactivity in Rhode 

Island began in the early 1950's with ground measurements 

of gross radioactivity by McKeown (1951). Johnson (1951) 

described a region of soutwestern Rhode Island as part of 

the "Central New England Radioactive Province." Popenoe 

(1966) compared aeroradioactivity surveys with the geology 

of Rhode Island. Goldsmith and others (1977) correlated 

aeroradioactivity and geology of the southwestern portion 

of Rhode Island and found trends similar to those of 

Popenoe (1966). The references cited here focus primarily 

on general measurements of radioactivity rather than 222Rn 

in water or air. 

Ryan and Kipp (1985) and Kipp and others (1986) 

investigated contamination of ground water by radioactive 

waste near Wood River Junction (fig. 82). The two major 

radionuclides that they detected were strontium-90 and 
I 

,J 

VERMONT c. NEW HAMPSHIRE 

{.-'i, Deerf~e~:----cf, ')0_~ Lowell ''--' 

0: hi • I MIDDLESEX I'" I~ I I....,J'-""\ 

1 Cl.) FRANKLIN ! 1 ""'' 

/.

: Jl ~ WORCESTER ~~Winches,er 11.1 L----"'--

0 c·.,HAMPSHIRE '~ SUFFOi:...K.C®Boston 

•s t 1l • Southampton ';J )~ "l,~NORFOLK I Egremont o u h '-'""'\. ~ I '-

- ' ---w .-::.# ~ 'I ., NORFOLK 

I r' •chicopee 1 , A"" eAblngton L__ \ HAMPDEN \ ,.- \ 

--~-- -...,___l...,__,../ \ 

Taunton e \PLYMOUTH 

tql~ ' 

New Bedford• 

CONN. 

0 

? 

0 

0 

? 

0 25 50Miles 

~.P'~ ~~ D ~ 

0 25 50 Kilometers o NANTUCKE~..s::::::J 

Figure 81. Locations of Massachusetts sites mentioned in text. (Scale 1:1 ,810,286; base from Delaney and Maevsky, 1980.) 

Table 32. Geohydrologic data and concentrations of radium and uranium in water samples from wells and springs in 

Massachusetts 

[Data from Scott and Barker (1962); locations shown in fig. 81; <, less than; pCi/L, picocuries per liter; gal/min, gallons per minute] 

location Geohydrologic data Concentration (pCi/l} 

Water- Well yield Date of Gross-beta Town County bearing Radium Uranium1 

unit (gal/min) collection activity 

Deerfield ........... Franklin Sugarloaf Formation 2 12-09-54 3 <0.1 0.5 

Lowell ............. Middlesex Ayer Granite 85 03-27-57 <5 <.1 2.3 

Winchester ......... Middlesex Newburyport Complex 5 06-16-54 <10 <.1 .3 

South Egremont .... Berkshire Stockbridge Formation 22 12-08-54 <20 .1 1.9 

Southampton ....... Hampshire Sugarloaf Formation 1.5 06-16-54 <5 .1 .2 

Chicopee ........... Hampden Chicopee Shale2 70 12-08-54 <25 .7 1.0 

Abington ........... Plymouth Wamsutta Formation 75 03-27-57 <5 .4 <.1 

Taunton ............ Bristol Rhode Island Formation 55 10-28-55 <10 .5 <.1 

New Bedford ....... Bristol Dedham Granite 100 10-31-55 <10 .3 1.1 

1 Converted from micrograms per liter (f.Lg/L) by multiplying by 0.68 and assuming that all activity is due to uranium and that uranium is in secular 

equilibrium. 2 A former usage. 

Radionuclides in the Northeastern United States and Southeastern Canada 209 
4~00' r-- ---·--,--l 

I ~~ I ·o I 

I ~~~ 

1 

PROVIDENCE • -r 

I I MASS. 

I 

I • I 

\ ' I 

E. Providence 

~-01----·-------- (.) 

j W .. :~:wick• 

I 

t------------

1 

I 

' WASHINGTON 

I Alton 

• I 

' ~,) e Wood River 

Junction I 

I 

D _{) BLOI-0-CK __ I_. __ -p __ _.._~--------~ 10 20Milts 

0 10 2 0 Kilometers 

Figure 82. Locations of Rhode Island sites mentioned in text. (Scale 1 :633,600; base from 

Lang, 1961.) 

technetium-99, whose combined gross-beta activity ranged 

from 5 to 500 pCi/L. They also found that both radionuclides were readily transported in the ground water in a sand 

and gravel aquifer. 

The Rhode Island Department of Environmental 

Management sampled 450 private drinking-water wells for 222Rn in 1986; preliminary results of 260 of those samples 

suggest an average concentration of 222Rn of 5,220 pCi/L 

210 Field Studies of Radon in Rocks, Soils, and Water 

(Margaret Bradley, Rhode Island Department of Environmental Management, written commun., 1988). 

Distribution and Concentration of Radionuclides 

in Ground Water 

Data on 222Rn and other radionuclides in samples 

collected in Rhode Island during national studies by Hess 
Table 33. Geohydrologic data and concentrations of radium and uranium in water samples from wells and springs in 

Rhode Island 

[Data from Scott and Barker (1962); locations shown in fig. 82; -,no data;<, less than; pCi/L, picocuries per liter; gal/min, gallons per minute] 

Location Geohydrologic data Concentration (pCi/L) 

Water- Well yield Date of Gross-beta Town County bearing Radium Uranium1 

unit (gal/min) collection activity 

East Providence ..... Providence Rhode Island Formation 27 06-21-54 <10 0.4 0.6 

East Providence ..... Providence Outwash 1,200 04--08-54 <5 <.1 .07 

West Warwick ...... Kent Cowesset Granite 3 06-26-55 15 .4 .9 

Alton .............. Washington Outwash 11-07-55 <10 1.2 <.07 

1

Converted from micrograms per liter (!J.giL) by multiplying by 0.68 and assuming that all activity is due to uranium and that uranium is in secular 

equilibrium. 

and others ( 1985b) and Horton ( 1983, 1985) are included in 

tables 25 and 26, which also give national averages for 

comparison. Michel and Jordana (1987) list a range of 100 

to 10,000 pCi/L for 222Rn and 1 to 5 pCi/L for 226Ra and 

total uranium in the drinking water from selected counties 

of Rhode Island. Table 33 includes concentrations of 

gross-beta radiation, total radium, and uranium in water 

from selected wells in Rhode Island. 

Preliminary results of 260 analyses of drinking water 

from private wells for 222Rn by the Rhode Island Department of Environmental Management show that 13 percent 

had concentrations greater than 10,000 pCi/L. The concentrations ranged from 140 to 49,080 pCi/L and averaged 

5,220 pCi/L (Margaret Bradley, Rhode Island Department 

of Environmental Management, written commun., 1988). 

Ground-Water Availability and Rate of 

Withdrawal 

Data on ground water withdrawals (Johnston, 1985) 

indicate the percentage of the population that is exposed to 

potential health risk from radionuclides in the water supply. 

The major aquifers in Rhode Island consist of stratified-drift 

deposits that have well yields ranging from 100 to 700 

gal/min. The crystalline-bedrock aquifers of Rhode Island 

are widely used for water supply and may have the highest 

concentrations of 222Rn; well yields from bedrock aquifers 

range from 1 to 20 gal/min. The 224,000 residents of Rhode 

Island that rely on ground water as a drinking supply, 9 

percent of which rely on small or private systems, withdraw 

24 Mgal/d. 

Radon in Indoor Air 

Information on 222Rn in indoor air in Rhode Island 

can be obtained through direct inquiry to the Rhode Island 

Department of Public Health, Division of Occupational 

Health. Although some indoor-air measurements have been 

made in Rhode Island, they are insufficient for statistical 

analysis. 

CONNECTICUT 

Previous Work 

Research on radioactivity in the environment in 

Connecticut dates back to the early 1900's, when Bumstead 

and Wheeler (1903, 1904) investigated radioactive gas in 

the soil and ground water near New Haven (fig. 83). They 

concluded that the concentration of 222Rn was not in 

equilibrium with the concentration of the radioactive parent 226Ra. Systematic studies of natural radioactivity in Connecticut began in the early 1950's as ground measurements 

of gross radioactivity by McKeown (1951). Johnson (1951) 

delineated a region of radioactive rocks he called the 

"Central New England Radioactive Province," which 

included part of central and eastern Connecticut. Popenoe 

( 1966) compiled a generalized map correlating aeroradioactivity with geology in Connecticut as well as New York, 

Rhode Island, and Maine. 

Goldsmith and others ( 1977) further investigated 

radioactivity in the rocks of Connecticut and correlated 

aeroradioactivity data with geologic data from southeastern 

Connecticut. They found that the Sterling Plutonic Group, 

the Narragansett Pier Granite, and the Westerly Granite all 

have fields of relatively high natural radioactivity. In 

contrast, the Tatnic Hill and Hebron Formations, as well as 

the Scotland Schist and Canterbury Gneiss, have fields of 

relatively moderate natural radioactivity, and the Quinebaug Formation and the Preston Gabbro had relatively low 

natural radioactivity. Jones (1979) analyzed National Uranium Resource Evaluation data for Connecticut with 

emphasis on results from the hydrogeochemical and streamsediment surveys. Krishanaswami and others ( 1982) investigated radium, thorium, and radioactive lead isotopes in 

Radionuclides in the Northeastern United States and Southeastern Canada 211 
73~0' 

MASS. 

~------r7 -1_;---,._,-Tr, ---r_j ___ l 

I 

( 

HARTFORD L, I LITCHFIELD l, TOLLAND I 

\ 

WINDHAM I ~~ Man~heste; )' \ 

~ I \ Hartford 

0 1 ~~illimantlc I R.I. 

;;: h )._, •Pial~v~--\ J" -----l ~ I \ _.f.-' LuV-( \ ' I 

\ __ U ___ J Meriden • \ -~ NEw LONDON I 

I ~ ~ MIDDLESEX J 

I -.. N • w " • v • N L--- _ _j r 

I "' Haven'\ l 

)FAIRFIELD 

' l ~ \ 

~/ 

' Long Island Sound 

\ 

0 10 20Miles 

0 10 20Kilometers 

Figure 83. Locations of Connecticut sites mentioned in text. (Scale 1 :1,050,000; base from Meade, 1978.) 

ground water of Connecticut and concluded that some 

process was removing 226Ra from the ground water. 

In the mid-1980's, the Connecticut Department of 

Health Services began a study to investigate 222Rn in water 

and air in Connecticut. In 1985, they sampled 63 domestic 

bedrock wells for 222Rn by liquid-scintillation techniques 

(Thomas, 1987) and made winter indoor-air measurements 

with alpha Track-Etch detectors in homes that had wellwater concentrations of 222Rn exceeding 10,000 pCi/L 

(approximately 25 percent of the original 63 homes). Of the 

homes tested, 15 percent had 222Rn concentrations exceeding 4.0 pCi/L (Thomas, 1987). 

The results of the work done in 1985 indicated that 

additional investigations were needed. In 1986 the Connecticut Department of Health Services began an expanded 

survey that included the sampling of 199 domestic wells 

from 26 different geologic formations totaling 45 rock units 

(Rothney, 1987 a; Thomas, 1987). Additionally, 202 

indoor-air measurements for 222Rn were made during three 

212 Field Studies of Radon in Rocks, Soils, and Water 

winter months by alpha Track-Etch detectors at each of the 

homes at which ground water was being tested. 

In late 1986 the Connecticut Department of Environmental Protection's Natural Resource Center began a 

project to measure the background levels of gamma radiation in a ground survey (Thomas, 1987, p. 354) that 

covered 1,367 mi (miles) across all major geologic terranes 

in Connecticut. The results correlated well with the groundwater testing program- areas that had high natural gammaradiation fields tended to have ground water with higher 222Rn concentrations, and areas that had low natural 

gamma-radiation fields tended to have lower ground water 222Rn concentrations (Thomas, 1987). 

Rothney ( 1987b) summarized the occurrence of 222Rn 

in domestic wells in Connecticut in relation to geologic and 

selected hydrologic characteristics and expanded her previous work (Rothney, 1987a) to include the results of the 

indoor-air survey. In 1988, an expanded indoor-air survey 

sponsored by the Environmental Protection Agency used 

charcoal-canister-type detectors in an additional 1 ,570 
Table 34. Geohydrologic data and concentrations of radium and uranium in water samples from wells and a spring in 

Connecticut 

[Data from Scott and Barker (1962); locations shown in fig. 83; <, less than; pCi/L, picocuries per liter; gaUmin, gallons per minute] 

Location Geohydrologic data Concentration (pCi/L) 

Water- Well yield Date of Gross-beta Town County bearing Radium Uranium1 

unit (gal/min) collection activity 

Stratton Brook ...... Hartford Glacial outwash 300 10-26-55 <5 <0.1 0.07 

Manchester ......... Hartford Continental arkose 457 11--04-54 <10 .1 .4 

Willimantic ......... Windham Willimantic Gneiss 10 10-25-54 <10 <.1 .3 

Plainville ........... Hartford Glacial sand and gravel 500 03--06-57 <5 .1 .3 

Meriden ............ New Haven Newark Supergroup 1.5 (spring) 06-24-54 <10 <.1 .5 

1 Converted from micrograms per liter (f-1-g/L) by multiplying by 0.68 and assuming that all activity is due to uranium and that uranium is in secular 

equilibrium. 

homes (Margaret Thomas, Connecticut Department of 

Environemntal Protection, Natural Resource Center, written commun., 1988). The Connecticut Department of Environmental Protection's Natural Resource Center used the 

department's geographic information system to analyze 

radionuclide data and develop area 222Rn assessments for 

the Connecticut Department of Health Services (Thomas, 

1988). 

Distribution and Concentration of Radionudides 

in Ground Water 

Data on 222Rn and other radionuclides in samples 

collected in Connecticut during national studies by Hess and 

others ( 1985b) and Horton ( 1983, 1985) are included in 

tables 25 and 26, which also give national averages for 

comparison. Michel and Jordana (1987) list a range of 100 

to 1 ,000 pCi/L for 222Rn, 1 to 5 pCi/L for 226Ra, and less 

than 1 to 5 pCi/L for total uranium in the drinking water 

from selected counties of Connecticut. Table 34 includes 

concentrations of gross-beta radiation, total radium, and 

uranium in water from selected wells in Connecticut. 

Hess and others ( 1985b) note that three public water 

supplies in Connecticut had total radium concentrations that 

exceeded 5 pCi/L. During a 1979 sampling of 115 public 

water-supply wells by the U.S. Geological Survey, 17 

samples had gross-alpha concentrations exceeding 15 

pCi/L, and 5 had dissolved radium concentrations exceeding 5 pCi/L (Robert Melvin, U.S. Geological Survey, 

written commun., 1988). Table 35 presents the results of 

the 222Rn in water survey of 202 domestic wells sampled 

from 1985 to 1987. 

Ground-Water Availability and Rate of 

Withdrawal 

Data on ground water withdrawals (Melvin, 1985) 

indicate the percentage of the population that is exposed to 

potential health risk from radionuclides in the water supply 

in Connecticut. The major aquifers in Connecticut consist 

of stratified-drift deposits that have well yields ranging from 

50 to 500 gal/min. The crystalline-bedrock aquifers of 

Connecticut are widely used for water supply and also have 

the highest concentrations of 222Rn. Well yields from 

bedrock aquifers range from 1 to 50 gal/min. The 984,000 

residents of Connecticut that rely on ground water as a 

drinking supply, 18 percent of which rely on small or 

private systems, withdraw 118 Mgalld. 

Radon in Indoor Air 

Data on 222Rn in indoor air in Connecticut are 

extensive. During the 1985 pilot study, the concentrations 

in homes above granitic areas in which 222Rn in ground 

water exceeded 10,000 pCi/L (Thomas, 1987) ranged from 

0.61 to 7.80 pCi/L, with a median of 2.06 pCi/L. In the 

1986 study, where 202 alpha Track-Etch detectors were 

placed in homes across the State, a mean of 1. 97 pCi/L was 

calculated, and concentrations ranged from 0.1 to 24.6 

pCi/L, with 12 percent exceeding 4 pCi/L. Table 36 

summarizes preliminary results of the 1987 indoor-air 

survey of 1,570 homes where 222Rn was measured with 

2-day exposure charcoal-canister-type detectors. 

NEW YORK 

Previous Work 

The first studies of natural radioactivity in New York 

were begun in the early 1950's as ground measurements of 

gross radioactivity by McKeown (1951), Narten and 

McKeown (1952), and McKeown and Klemic (1953a,b). 

Klemic and others ( 1959) have investigated in some detail 

the Phillips uranium mine in the Camp Smith area in 

southeastern New York (fig. 84). Swanson (1960) meaRadionudides in the Northeastern United States and Southeastern Canada 213 
Table 35. Results of the 1985-87 well-water survey of 202 homes in Connecticut for radon-222 

[Data from Rothney (1987b); pCi/L, picocuries per liter] 

Geologic terrane1 

Sedimentary basins ...................................... . 

Extrusive igneous within sedimentary basins ............... . 

Two-mica granites ....................................... . 

General gneiss .......................................... . 

Granitic gneiss .......................................... . 

Intermediate to mafic gneiss .............................. . 

Stratified metamorphics .................................. . 

Carbonate within stratified metamorphics .................. . 

Quartzite within statified metamorphics ................... . 

General mixture ......................................... . 

1

Based on classification scheme of Olszewski and Boudette (1986). 

Number 

of homes 

44 

5 

12 

37 

63 

11 

61 

9 

3 

16 

Range (pCi!L) 

Minimum Maximum Geometric 

mean 

230 11,620 1,335 

470 2,980 950 

10,720 130,240 28,254 

180 48,820 3,160 

420 87,450 7,495 

870 22,300 4,638 

370 36,560 2,937 

200 4,130 746 

100 14,780 4,234 

230 14,470 1,393 

Table 36. Summary of radon-222 in indoor air in Connecticut during the winter of 1986-87 

[Data from Rothney (1987b, p. 27); pCi/L, picocuries per liter] 

Geologic terrane1 

Merrimack synclinorium ................................. . 

Connecticut Valley synclinorium .......................... . 

Bronson Hill anticlinorium ............................... . 

Avalonian .............................................. . 

Carbonate shelf ......................................... . 

Taconic allochthons ..................................... . 

Hartford and Pomperaug basins (Newark terranes) ......... . 

Proterozic massifs ....................................... . 

Total ............................................ . 

1 From Rodgers (1985). 

sured the uranium content of black shales (probably the 

Dunkirk member) in southwestern New York. These three 

measurements show a range of 0. 001 to 0. 006 percent 

uranium by weight. Popenoe (1966) compared areoradioactivity surveys with the geology of southeastern New York 

and noted relatively high background radioactivity in the 

Hudson Highlands near West Point (fig. 84) and noted 

above-background radioactivity in the till that forms the 

terminal moraines on Long Island. 

Campbell and others ( 1979) updated some basic 

geologic data on the Phillips mine in the Camp Smith area 

through geophysical techniques including radiometric, 

magnetic, and very-low-frequency resistivity surveys. Van 

Tyne and others ( 1980a-f) mapped the thickness of the 

radioactive black shales in the Hamilton, Genesee, Sonyea, 

West Falls, and Java Groups and the Perrysburg Formation 

of western New York from gamma-ray logs. Nutt (1982) 

produced a comprehensive review of uranium occurrence in 

the Precambrian rocks of the Adirondack region in northern 

New York. Fleischer and others (1982) investigated 222Rn 

214 Field Studies of Radon in Rocks, Soils, and Water 

Number 

of tests 

271 

410 

107 

207 

51 

46 

295 

36 

1,423 

Percentage of total exceeding 

4 pCi/L 10 pCi/L 20 pCi/L 

26.2 

22.9 

21.5 

19.3 

21.6 

8.7 

9.4 

13.9 

8.1 

4.6 

2.8 

4.4 

5.9 

4.3 

1.7 

0 

2.2 

1.2 

1.9 

.5 

0 

0 

0 

0 

in energy-efficient homes in New York with 6-month, alpha 

Track-Etch measurements during both winter and summer 

periods. 

Kothari (1983) noted that the National Uranium 

Resource Evaluation data for Lewiston (fig. 84) suggest a 

1.5-ppm uranium equivalence at land surface and that the 

measured 222Rn in homes in that area ranged from 0. 34 to 

0. 79 pCi/L. Fleischer and Turner (1984a) surveyed an area 

in Albany and Schenectady Counties with radiometric 222Rn, isotopic, and chemical techniques to investigate a 

part of the Eastern Overthrust Belt as a possible hydrocarbon source area. Fleischer and Turner ( 1984b) investigated 

indoor-air levels of 222Rn in energy-efficient homes in the 

Albany area for 1 year with alpha Track-Etch detectors. The 

New York State Department of Health (1985) published a 

generalized fact sheet on 222Rn in ground water. 

The Hudson Highlands of New York (fig. 84) have 

mineral assemblages and geologic structure that are similar 

to the rock of the Reading Prong in Pennsylvania 

(Gundersen, 1986). The U.S. Geological Survey has developed a geologic and metallogenic model for uranium 
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Figure 84. locations of New York sites mentioned in text. (Scale 1 :3,727,059; base from Heath, 1964.) 
mineralization in the Hudson Highlands and Reading Prong 

in New Jersey and Pennsylvania (L.C.S. Gundersen, U.S. 

Geological Survey, oral commun., 1986). 

The New York State Energy Research and Development Authority (1981, 1983, 1984) investigated lowtemperature geothermal potentials near Albany, Saratoga 

Springs, and Auburn (fig. 84). The source of the higherthan-expected geothermal gradient of 22.96 °C per kilometer is not clearly defined, but these geothermal wells are 

finished in the Precambrian-age igneous and metamorphic 

basement rock of New York, and heating due to radioactive 

decay has not been ruled out. The New York State Energy 

Research and Development Authority (1983, p. 3-3) 

reports anomalously high helium concentrations in samples 

from many of these wells and a 222Rn concentration of 350 

pCi/L in a sample of spring water from Saratoga Springs. 

The New York State Department of Health (Kunz and 

Kothari, 1986; Lilley and others, 1987) and the New York 

State Energy Research and Development Authority (American Geological Institute, 1987a) show that the 222Rn 

concentration in the air in private homes in several counties 

exceed the recommended 4 pCi/L guideline. Kunz and 

Kothari ( 1986) measured 222Rn concentrations in soil gas at 

a depth of 3 to 4 ft across the State; the values ranged from 

100 to 50,000 pCi/L. They also measured the 226Ra content 

of soils across the State and found average concentrations 

ranging from 0.46 pCi/ g in sandy soils on Long Island to 

2.2 pCi/g in soils overlying the Marcellus Shale in western 

New York. Preliminary results of measurements of 222Rn in 

drinking water from 132 large public supplies suggest that 

the concentrations in all sources were lower than 800 pCi/L, 

although the range of the measurements in wells samples 

across New York State was 100 to 350,000 pCi/L. 

Banikowski and Hand (1987) completed a preliminary study of 222Rn in indoor air in the basements of 210 

homes in Onondaga County during a 4-day test with 

charcoal-canister-type detectors. Results suggest that the 

Marcellus Shale, a black shale of the Middle Devonian 

Hamilton Group, is a source rock for 222Rn in indoor air. 

None of the 100 homes tested that were underlain by the 

Marcellus Shale had indoor-air levels of 222Rn below 4 

pCi/L, and the average indoor-air concentration was 8.8 

pCi/L. The New York State Department of Health measured 

air in basements of 15 homes underlain by Marcellus Shale 

and found that 4 had levels less than 4 pCi/L (Charles Kunz, 

New York State Department of Health, written commun., 

1988). The U.S. Military Academy at West Point (fig. 84), 

in the Hudson Highlands near the Phillips mine, began a 

10-week indoor-air testing program for buildings in the 

Academy with charcoal-canister-type detectors (American 

Geological Institute, 1987b; Frieland and Cherry, 1987). 

Data for gross-alpha radiation and 222Rn in ground water 

from the Academy were collected but are unavailable at 

present. 

216 Field Studies of Radon in Rocks, Soils, and Water 

Bergeron and others ( 1987) and Yager ( 1987) report 

on geohydrologic conditions and ground-water-flow modeling at the nuclear-fuels-reprocessing plant and wastemanagement facility at the western New York Nuclear 

Service Center in Cattaraugus County. Chemical analyses 

for some less common radionuclides were completed, but 

no analyses were made for 238 '

234U, 226'228Ra, or 222Rn in 

ground water. 

Nero (1983) found that the average range of 222Rn in 

18 single-family residences in New York was 1.0 to 6.4 

pCi/L. Results of a national study of 222Rn in indoor air that 

included some data for New York indicated concentrations 

of0.52 to 1.57 pCi/L (Nero and others, 1986). Fisenne and 

others (1987) reviewed the daily intake of 234•

235 •238U, 228 230 23 ~h, and 226•

228Ra by New York City residents and 

found that neither the ingestion of food or water nor the 

inhalation of air constituted a health threat because the 

levels did not exceed present standards. 

Distribution and Concentration of Radionuclides 

in Ground Water 

Data on 222Rn and other radionuclides in samples 

collected in New York during national studies by Hess and 

others ( 1985b) and Horton ( 1983, 1985) are included in 

tables 25 and 26, which also give national averages for 

comparison. Michel and Jordana (1987) list a range of less 

than 100 to 1,000 pCi/L for 222Rn, less than 1 to 5 pCi/L for 226Ra, and less than 1 pCi/L for total uranium in the 

drinking water from selected counties of New York. Table 

37 includes concentrations of gross-beta radiation, total 

radium, and uranium in water from selected wells in New 

York. The New York State Department of Health (1985) 

fact sheet on 222Rn in drinking water notes that 222Rn 

concentrations in drinking water from 132 large public 

supplies were lower than 800 pCi/L, although one well in 

Orange County in the Hudson Highlands had a 222Rn 

concentration of 350,000 pCi/L (Charles Kunz, New York 

State Department of Health, written commun., 1988). 

Ground-Water Availability and Rate of 

Withdrawal 

Data on ground water withdrawals (Waller and others, 1985) indicate what percentage of the population is 

exposed to potential health risk from radionuclides in the 

water supply. The 6,133,000 residents of New York that 

rely on ground water as a drinking supply, 13 percent of 

which rely on small or private systems, withdraw 670 

Mgal/d. About 486 Mgal/d are withdrawn from the aquifers 

on Long Island, whose aquifers are unconsolidated coastal-
Table 37. Geohydrologic data and concentrations of radium and uranium in water samples from wells and a spring in New 

York 

[Data from Scott and Barker (1962); locations shown in fig. 84; -. no data; <, less than; pCi/L, picocuries per liter; gal/min, gallons per minute] 

Location Geohydrologic data Concentration (pCi/L} 

Water- Well yield Date of Gross-beta Town County bearing Radium Uranium1 

unit (gal/min) collection activity 

Bloomingdale ............. Essex Grenville Complex 06-07-54 <10 <0.1 0.7 

Lake Pleasant Village ..... Hamilton Syenite 10 10-05-54 <5 .1 .4 

Lyons .................... Wayne Salina Group 150 05-03-56 <1,000 11 4.1 

Syracuse ................. Onondaga Camillus Shale, 75 05-03-56 <50 <.1 1.4 

Vernon Shale 

Victor .................... Ontario Kame deposit 200+ 05-03-56 <20 <.1 .4 

(spring) 

Canandaigua .............. Ontario Ludlowville Formation 15 07-12-54 <50 1.0 .7 

Sand Lake ................ Rensselaer Rensselaer Graywacke 1 09-20-54 <25 .1 3.4 

Lebanon Springs Village .. Columbia Stockbridge Limestone 75 09-20-54 <10 .1 .9 

Carmel ................... Putnam Granitic gneiss .4 05-12-54 <25 1.8 1.0 

Greenwood Lake .......... Orange Granitic gneiss 3 09-15-54 <5 .1 .3 

Westbury ................. Nassau Magothy Formation 1,050 03-26-57 <5 <.1 .2 

Westbury ................. Nassau Llyod Sand Member 1,000 03-26-57 <5 <.1 .7 

of Raritan Formation 

1 Converted from micrograms per liter (j.Lg/L) by multiplying by 0.68 and assuming that all activity is due to uranium and that uranium is in secular 

equilibrium. 

plain deposits. Well yields there range from 50 to 1,200 

gal/min and are considered to be free of radionuclides. The 

major upstate aquifers consist of stratified-drift deposits that 

have well yields ranging from 10 to 1,000 gal/min. The 

sedimentary and carbonate bedrock aquifers of New York 

are also widely used for water supply and may have high 

concentrations of 222Rn. Well yields from crystallinebedrock aquifers range from 50 to 150 gal/min. 

Radon in Indoor Air 

The New York State Department of Health and the 

New York State Energy Research and Development 

Authority investigated 222Rn in indoor air in 2,400 homes in 

1986 (table 38). The statewide mean for 222Rn in indoor air 

was 1.39 pCi/L, and the range was from 0.06 to 39.8 pCi/L. 

Soil-gas measurements of 222Rn have also been made 

across the State (Charles Kunz, New York Department of 

Health, oral commun., 1988); the average concentration in 

samples taken at a depth of between 3 and 4 ft was about 

700 pCi/L, and the range was from 100 to 50,000 pCi/L. 

Data for 226Ra in soil yielded a statewide average of 1.0 

pCi/ g and a range of 0. 2 to 20 pCi/ g. Some homes in upstate 

New York that have high concentrations of 222Rn in indoor 

air have average 226Ra concentrations in the underlying 

soils. 

Banikowski and Hand (1987) reported that the geometric mean concentration of 222Rn in indoor air in basements in 100 homes over the Marcellus Shale in central 

New York was 8.8 pCi/L. The mean for homes overlying 

the Upper Silurian shales and dolostones was 2.5 pCi/L. 

The mean for homes overlying the upper Middle Devonian 

sandstones and shales was 1.2 pCi/L. 

CANADA-SOUTHERN ONTARIO 

Radionuclides in the southern part of the Province of 

Ontario, Canada (fig. 77), are included in this report for two 

reasons. First, some of the most detailed data for uranium, 226Ra, and 222Rn in ground water from Cambrian through 

Devonian marine sedimentary rocks are from Canadian 

research; these rocks occur in New York State and parts of 

New England. Canadian researchers also have investigated 

the Precambrian crystalline rocks of the Canadian Shield for 

radionuclide content. These sedimentary and crystalline 

rocks are commonly found in the stratified drift and other 

glacial deposits that form the most productive aquifers in 

New England. In addition, many investigators extend their 

work only to the borders of the United States, so "blank" 

zones appear on geologic maps in areas just beyond the 

United States border. Because the geologic terranes continue across national boundaries, information from both 

sides should be included where possible. This section 

provides some general information. 

Previous Work 

The Joint Federal-Provincial working group on drinking water proposes drinking-water standards, as does the 

Radionudides in the Northeastern United States and Southeastern Canada 217 
Table 38. Concentrations of radon-222 in indoor air in New York by region and stratigraphic units 

[Data from the New York State Department of Health (1985); locations shown in inset map (from U.S. Geological Survey, 1985); physiographic diagram 

from Raisz (1954); divisions from Fenneman (1946); pCi/L, picocuries per liter] 

Region and geologic units Number Concentrations, in pCi/L 

of samples Mean Range 

Appalachian Plateaus (Devonian shales and sandstones) ...................... . 346 3.34 0.09-39.8 

Central Lowland (Devonian shale, Silurian shale and dolomite, 

Ordovician limestone) ................................................... . 767 1.58 .07-28.4 

Valley and Ridge Province (Cambrian and Ordovician shales, limestones, 

and sandstones of the Catskill Delta Sequence) ............................ . 545 1.09 .06-21.6 

Adirondack Province (Precambrian igneous and metamorphic rocks) ........... . 276 1.82 .08-20.9 

Piedmont Province-Staten Island (Precambrian igneous and metamorphic 

rocks) .................................................................. . 51 .75 .19-2.4 

Piedmont Province-New York City (Precambrian igneous and 

metamorphic rocks) ..................................................... . 81 .81 .08-2.4 

Coastal Plain (Quaternary glacial surficial deposits) .......................... . 335 0.87 .07-3.4 

EXPLANATION 

A. ST. LAWERENCE VALLEY 

B. ADIRONDACK PROVINCE 

C. MOHAWK SECTION 

D.CENTRALLOWLAND 

E. APPALACHIAN PLATEAUS 

F. TACONIC AND GREEN 

MOUNTAIN SECTIONS 

G. CATSKILL SECTION 

H. VALLEY AND RIDGE PROVINCE 

I. NEW ENGLAND PROVINCE 

J. PIEDMONT PROVINCE 

K. COASTAL PLAIN 

Environmental Protection Agency in the United States, and 

the Ontario Ministry of the Environment investigates the 

occurrence and distribution of radionuclides in drinking 

water (Beck and Brown, 1987, p. 450). Although some 

detailed investigations of radionuclides in the Canadian 

Shield and sedimentary rock environments have been made, 

no drinking-water standard for 222Rn has been set. Drinking 

water standards for total uranium and 226Ra have been set at 

20 j..Lg/L and 27 pCi/L, respectively (Beck and Brown, 

1987, p. 450-451). 

McGregor and others (1980) measured 222Rn in 

indoor air in about 10,000 homes from 14 Canadian cities 

from June through August of 1977 and 1978. Indoor air was 

drawn through a Lucas-type cell (alpha-scintillation counting cell) for 5 min at a constant rate of 0.3 L/s (liters per 

second). Results indicated that generally fewer than 10 

percent of the homes tested had indoor air concentrations of 222Rn exceeding 4.0 pCi/L. Work prepared for the Atomic 

Energy Control Board of Canda ( 1983) showed that 226Ra in 

the unconsolidated materials in Canada ranged from 7.0 

pCi/g for clays to 0.2 pCi/g for sand at Bancroft (fig. 85). 

Till from Niagara Falls had a 226Ra concentration of 0. 7 

pCi/g. 

218 Field Studies of Radon in Rocks, Soils, and Water 

Lemire and Gascoyne ( 1987) reported on the occurrence and distribution of uranium, 226Ra, and 222Rn in 

surface waters and ground waters at five nuclear-research 

laboratories across Canada. These surveys were undertaken 

to document the natural background levels of radioactivity 

at the laboratories. Beck and Brown (1987) analyzed 166 

ground-water samples (29 from municipal sources and 137 

from private supplies) for total uranium, 226Ra, and 222Rn. 

Two regions were sampled extensively. One, which is near 

Bancroft, is underlain by the rocks of the Precambrian 

Canadian Shield, and the other, which is near the eastern 

shore of Lake Huron, is underlain by limestones and 

dolomites of the Middle Devonian Detroit River Group. 

Distribution and Concentration of Radionuclides 

in Water 

The international system (SI) unit for radiation is the 

Becquerel (Bq). One Curie is equal to 3.7 x 1010 Bq; 1 pCi 

is equal to 3.7 x 10-2 Bq (Durrance, 1987, p. 69.). For 

consistency, all reported concentrations have been converted to picocuries per liter for 226Ra and 222Rn and 

micrograms per liter for uranium. 
80° 71°30' 

46°00';-----~--------------------------------------------------------4 

.......__ -- ...,...-. 

ONTARIO 

Ban croft 

• 

QUEBEC 

NEW YORK 

Sherbrooke 

• 

• I 

' ' '(ERMONT( 

' \ 

Albany 

• 

\ 

Figure 85. Locations of southern Ontario sites mentioned in text. 

Lemire and Gascoyne (1987, p. 108) present ranges 

of concentrations of uranium, 226Ra, and 222Rn in surface 

water and ground water. The values for uranium in surface 

water were generally less than 0. 2 tJ.g/L and in ground water 

less than 0.1 to 10.2 tJ.giL; 226Ra in surface water ranged 

from less than 0. 5 to 18.9 pCi/L and in ground water less 

than 0. 5 to 1.1 pCi/L; 222Rn in surface water ranged from 

less than 2. 7 to 8.1 pCi/L and in ground water from less 

than 2.7 to 13,100 pCi/L. 

Beck and Brown ( 1987) reported that uranium concentrations in samples from wells finished in the Canadian 

Shield rocks near Bancroft ranged from less than 2 to 74.8 

pCi/L, 226Ra concentrations ranged from less than 1 to 25 

pCi/L, and 222Rn concentrations ranged from 1 to 44,600 

pCi/L. They also reported that, for wells finished in the 

rocks of the Detroit River Group, uranium concentrations 

ranged from less than 2 to 26.5 pCi/L, 226Ra concentrations 

from less than 1 to 18.4 pCi/L, and 222Rn concentrations 

from 140 to 11,000 pCi/L. 

Radon in Indoor Air in Toronto, Montreal, 

Sherbrooke, and Quebec 

McGregor and others (1980) presented data on 

indoor-air concentrations of 222Rn for 14 cities. Four of 

these-Toronto, Montreal, Sherbrooke, and Quebec-are 

discussed here because they are close to the U.S. border. 

The geometric means of 222Rn in indoor air were 0. 31 pCi/L 

in Toronto, 0.29 pCi/L in Montreal, 0.36 pCi/L in Sherbrooke, and 0.28 pCi/L in Quebec. Of the homes measured, 

99.9, 98.2, 90.6, and 95.9 percent of the homes in Toronto, 

Montreal, Sherbrooke, and Quebec, respectively, had 

indoor-air levels of 222Rn below 4.0 pCi/L. Information on 222Rn in indoor air in Canada can be obtained through direct 

inquiry to the Department of National Health and Welfare, 

Ottawa, Ontario. 

ACKNOWLEDGMENTS 

The author gratefully acknowledges the reviews and 

references provided for individual State sections by the 

following people, listed by State: Maine, Charles T. Hess, 

Department of Physics, University of Maine at Orono, 

Donald C. Hoxie, Director of the Division of Health 

Engineering, Maine Department of Human Services, and 

Melanie Lanctot of the Environmental Health Unit, Maine 

Department of Human Services; New Hampshire, Francis 

Hall of the Department of the Earth Sciences, University of 

New Hampshire, and Eugene Baudette, New Hampshire 

State Geologist, Department of the Earth Sciences, UniverRadionuclides in the Northeastern United States and Southeastern Canada 219 
sity of New Hampshire~ Vermont, Paul Clemmons of the 

Vermont Department of Health, Division of Occupational 

and Radiological Health, and Winslow Ladue of the Vermont Department of Health, Division of Environmental 

Health; Massachusetts, William Bell of the Massachusetts 

Department of Public Health~ Rhode Island, J. Allan Cain, 

State Geologist of Rhode Island, James E. Hickey, Director, Rhode Island Division of Occupational Health, and 

Margaret Bradley of the Rhode Island Department of 

Environmental Management; Connecticut, Margaret Thomas of the Connecticut Department of Environmental Protection, Natural Resources Center~ and New York, Charles 

Kunz of the New York State Department of Health. 

REFERENCES CITED 

Adamik, J.T., 1984, Present and proposed ground-water-level 

program in Maine: U.S. Geological Survey Water-Resources 

Investigations Report 84-4235, 43 p. 

American Geological Institute, 1987a, New York looks for radon: 

Geotimes, March 1987, p. 21. 

---1987b, Test for radon: Geotimes, May 1987, p. 21. 

Archer, V.E., Gillam, J.D., and Wagoner, J.K., 1976, Respiratory disease mortality among uranium miners: Annals of New 

York Academy of Science, v. 271, p. 280. 

Atomic Energy Control Board of Canada, 1983, Review of 

existing instrumentation and evaluation of possibilities for 

research and development of instrumentation to determine 

future levels of radon at a proposed building site: Ottawa, 

Canada, Atomic Energy Control Board, INF0-0096, 50 p. 

Banikowski, J.E., and Hand, B., 1987, Radon in Onondaga 

County: Preliminary report: Syracuse, N.Y., Onondaga 

County Department of Health-Division of Environmental 

Health, 9 p. 

Barker, F.B., and Johnson, J.O., 1964, Determination of radium 

in water: U.S. Geological Survey Water-Supply Paper 

1696-B, p. B1-B29. 

Barker, F.B., Johnson, J.O., Edwards, K.W., and Robinson, 

B.P., 1965, Determination of uranium in natural waters: U.S. 

Geological Survey Water-Supply Paper 1696-C, p. 1-25. 

Barker, F.B., and Robinson, B.P., 1963, Determination of beta 

activity in water: U.S. Geological Survey Water-Supply 

Paper 1696-A, p. A1-A32. 

Beck, P.J., and Brown, D.R., 1987, Controls on the occurrence of 

radionuclides in ground water of southern Ontario, in Graves, 

B., ed., 1987, Radon in ground water: Chelsea, Mich., 

Lewis Publishers, p. 449--476. 

Bell, K.G., 1963, Uranium in carbonate rocks: U.S. Geological 

Survey Professional Paper 474-A, p. A1-A29. 

Bergeron, M.P., Kappel, W.K., and Yager, R.M., 1987, Geohydrologic conditions at the nuclear-fuels reprocessing plant 

and waste-management facilities at the Western New York 

Nuclear Service Center, Cattaraugus County, New York: 

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Thomas, M., 1987, A Connecticut radon study-Using limited 

water sampling and a statewide ground-based gamma survey 

to help guide an indoor air testing program. A progress 

report, in Graves, B., ed., 1987, Radon in ground water: 

Chelsea, Mich., Lewis Publishers, p. 347-362. 

---1988, A geographic information system approach to managing Connecticut's radon program [abs.]: Geological Society of America Abstracts with Programs, 23d annual meeting, Northeastern section, v. 20, no. 1, p. 26. 

U.S. Atomic Energy Commission, 1969, Preliminary reconnaissance for uranium in Connecticut, Maine, Massachusetts, 

New Jersey, New York and Vermont: U.S. Atomic Energy 

Commission, RME-4106, TID UC -51, 115 p. 

U.S. Department of Agriculture, 1986, Radon in water and air 

health risks and control measures: Orono, University of 

Maine, Cooperative Extension Service, 8 p. 

U.S. Department of Energy, 1980, An assessment report on 

uranium in the United States of America: Grand Junction, 

Colo., U.S. Department of Energy, GJ0-111(80), 150 p. 

U.S. Geological Survey, 1985, National Water Summary 1984; 

Hydrologic events, selected water-quality trends, and 

ground-water resources: U.S. Geological Survey WaterSupply Paper 2275, p. 325. 

Vanecek, J.D., and Dorsey, R.J., 1983a, Geologic and radiometric survey of the Sweney farm: Montpelier, Vt., Division of 

Geology and Earth Resources, Agency of Environmental 

Conservation, No. 1983-2, 15 p. 

---1983b, Geologic and radiometric survey of part of the 

Monkton-Starkboro area: Montpelier, Vt., Division of Geology and Earth Resources, Agency of Environmental Conservation, No. 1983-3, 16 p. 

Van Tyne, A.M., Kamakaris, D.G., and Carbo, S., 1980a: 

Isopach of radioactive shale in the Hamilton group: Albany, 

N.Y., New York State Museum and Science Services, 2 pl., 

scale 1:250,000. 

---1980b, Isopach of radioactive shale in the Genesse group: 

Albany, N.Y., New York State Museum and Science Services, 2 pl., scale 1:250,000. 

---1980c, Isopach of radioactive shale in the Sonyea group: 

Albany, N.Y., New York State Museum and Science Services, 2 pl., scale 1:250,000. 

---1980d, Isopach of radioactive shale in the West Falls 

formation: Albany, N.Y., New York State Museum and 

Science Services, 2 pl., scale 1:250,000. 

---1980e, Isopach of radioactive shale in the Java formation: 

Albany, N.Y., New York State Museum and Science Services, 2 pl., scale 1:250,000. 

---1980f, Isopach of radioactive shale in the Perrysburg 

formation: Albany, N.Y., New York State Museum and 

Science Services, 2 pl., scale 1:250,000. 
Waller, R.M., Koszalka, E.J., and Snavely, D.S., 1985 New 

York ground water resources, in U.S. Geological Survey, 

National water summary 1984; Hydrologic events, selected 

water-quality trends, and ground-water resources: U.S. 

Geological Survey Water-Supply Paper 2275, p. 323-328. 

Wathen, J.B., 1986, Factors affecting levels of Rn-222 in wells 

drilled into two-mica granites in Maine and New Hampshire: 

Unpublished M.Sc. thesis, University of New Hampshire, 

97 p. 

---1987, The effects of uranium siting in two-mica granites on 

uranium concentrations and radon activity in ground water, in 

Graves, B., ed., 1987, Radon in ground water: Chelsea, 

Mich., Lewis Publishers, p. 31-46. 

Wathen, J.B., and Hall, P.R., 1986, Factors affecting levels of 

Rn-222 in wells drilled into two-mica granites in Maine and 

New Hampshire, in Proceedings of Association of Ground 

Water Scientists and Engineers, Third Annual Eastern 

Regional Ground Water Conference: Dublin, Ohio, National 

Water Well Association, p. 650-681. 

Weeks, E.P., 1987, Field tests of flow and transport in unsaturated 

media, in Dinwiddie, G.A., and Trask, N.J., eds., 1986, 

U.S. Geological Survey research in radioactive waste disposal-Fiscal years 1983, 1984, and 1985: U.S. Geological 

Survey Water-Resources Investigations Report 87-4009, p. 

62-64. 

Weiffenbach, C. V., 1982, Radon in water and air pollution: Risks 

and control: Orono, University of Maine, Land and Water 

Resources Center, 4 p. 

Yager, R.M., 1987, Simulation of ground-water flow near the 

nuclear-fuel reprocessing facility at the western New York 

Nuclear Service Center, Cattaraugus County, New York: 

U.S. Geological Survey Water-Resources Investigations 

Report 85-4308, 58 p. 

Yang, I.C., 1984, Improved method for the determination of 

dissolved 226Ra, in Vogt, J.R., ed., Proceedings of the 5th 

International Conference on Nuclear Methods in 

Environmental and Energy Research: U.S. Department of 

Energy ONF-840408, p. 191-201. 

---1987, Sampling and analysis of dissolved radon-222 in 

surface and ground water, in Graves, B., ed., Radon in 

ground water: Chelsea, Mich., Lewis Publishers, p. 

193-203. 

Radionudides in the Northeastern United States and Southeastern Canada 225 

PART 2: STUDIES OF RADON IN WATER 

SECTION 2: TECHNIQUES FOR MEASURING RADON IN WATER 

SAMPLING AND ANALYSIS OF DISSOLVED RADON-222 IN WATER BY THE 

DE-EMANATION METHOD 

In Che Yang 

Abstract 

Collection of surface- or ground-water samples for 

determining the concentration of dissolved radon gas is 

best performed by minimizing aeration of water to be 

sampled. Radon loss during transportation from the sampling site to the laboratory (within 1 week) was negligible 

for low-activity samples and was 4 percent for high-activity 

samples. Radon loss during storage for 1 week is negligible. The direct de-emanation and alpha-scintillation 

counting method is sensitive (0.2 picocurie per liter for a 

60-milliliter sample) and has a better precision than other 

methods for analysis of most environmental samples. 

INTRODUCTION 

Radon-222 e22Rn) is a radioactive gas known to 

occur in ground water. The gas diffuses throughout a 

ground-water aquifer, and its concentration can be many 

orders of magnitude larger than the concentration of radium 

or uranium. Radon-222 is a daughter product of radium-226 

e26Ra) and has a short half-life (3.8 days); however, 

long-lived components of the decay products (those of 

environmental concern) are lead-210 e10Pb, half-life of 22 

years and a weak beta emitter) and Polonium-210 e10Po, 

half-life of 138.4 days and an alpha emitter). The method 

by which 222Rn enters the body tissue of a person is not well 

understood. A maximum contaminant level for 222Rn in 

drinking water is under consideration by the Environmental 

Protection Agency (Environmental Protection Agency, 

1983). 

Sampling and measurement of 222Rn are complicated 

by the volatility of the gaseous element. For example, 222Rn 

in water appears to be removed effectively by aeration. 

Therefore, when water is sampled for 222Rn analysis, 

aeration of the water needs to be minimized, and transfer of 

samples through the open air needs to be avoided. Loss of 222R d . n unng . d "f transportatiOn an storage may occur 1 

sampling vessels are permeable to gas, or if they have leaky 

stopcocks and caps. This paper describes the direct deemanation and alpha-scintillation count method used for 

accurate analysis of dissolved radon gas in surface and 

ground water. In addition, sampling techniques and possible loss of radon during the sample transport are also 

discussed. 

EXPERIMENTAL METHODS 

Water Sampling 

An all-glass de-emanation bubbler (fig. 86) is used 

for collecting water samples for analysis of 222Rn. Before 

sampling, evacuate the bubbler (assembled as shown in fig. 

86) to less than 10 mtorr (millitorr) in the laboratory or 

laboratory trailer through stopcock 1 (stopcock 2 is closed). 

Then, close stopcock 1. Gently place the evacuated sample 

bubbler into the surface water until the space between 

stopcock 1 and the inlet port is filled with water. Open 

stopcock 1 to draw sample water directly into the main 

chamber of the bubbler, until the chamber is 60 percent full. 

Close stopcock 1. Label bubbler with sample number, place 

of collection, and collection time (day, hour, and minute). 

Use masking tape to secure stopcocks 1 and 2 in the closed 

position. Place bubbler inside a foam-packed cardboard box 

and send by airmail to the laboratory as soon as possible. 

For ground-water samples, use a peristaltic pump or a 

submersible pump to supply an uncontaminated, fullcolumn flow of sample water through a short, flexible 

tubing to the stopcock-1 end of the evacuated bubbler. 

When the main chamber is about 60 percent full (as shown 

in fig. 86), close stopcock 1. Label and transport samples to 

the laboratory in the same manner described for the surfacewater samples. 

Transportation and Storage 

Collect two sets of source waters (one set from a 

low-activity source, less than 1,000 pCi/L (picocuries per 

liter), and the other set from a high-activity source, 

6,000-7,000 pCi/L) by using three replicates of similar 

bubblers for this investigation. Analyze one replicate soon 

after sampling; send a second replicate to University of 

Texas Health Science Center at Houston, Tex., for return 

immediately after receipt (about 1 week for a round trip), 

and keep a third in the laboratory until the shipped replicate 

is returned. Analyze at the same time the samples that were 

sent away and the samples that were stored. 

Sampling and Analysis of Dissolved Radon-222 in Water by the De-emanation Method 227 
INLET PORT 

SCREW 

CLAMP """ 

FRITTED-GLASS 

DISK 

I 

STOPCOCK 2 

Figure 86. An all-glass de-emanation bubbler used for 

collecting water samples for analysis of radon-222. 

Analytical Method 

Radon-222 in surface water or lake water derives 

from two sources: one source is the in situ decay of 226Ra 

already in water; the other source is external, such as 226Ra 

in rocks and sediments or inflow of other water containing 

mainly dissolved 222Rn with little parent 226Ra (commonly 

called excess or nonsupported 222Rn). To measure the 

excess or nonsupported 222Rn, the quantity of 222Rn in 

equilibrium with the 226Ra has to be determined after the 

total 222Rn measurement (Yang, 1984). The relation among 

various components of 222Rn can be expressed in the 

following equation: 

222Rn (total)- 222Rn (supported, in equilibrium with 226Ra) 

= 222Rn (nonsupported). 

Here the supported 222Rn is assumed to be in equilibrium 

with the 226Ra; the assumption is reasonable because of the 

short half-life of 222Rn. 

De-emanation 

When 222Rn samples are received in the laboratory, 

they should be analyzed immediately. Clamp the bubbler to 

the de-emanation system (fig. 87). This de-emanation 

228 Field Studies of Radon in Rocks, Soils, and Water 

MANOMETER 

ALPHASCINTILLATION 

CELL 

Figure 87. The radon de-emanation system. 

system consists of the following parts: (1) a bubbler, (2) a 

glass drying tube packed with drierite (anhydrous magnesium perchlorate) to remove moisture and with ascarite 

(NaOH on asbestos plus soda lime) to remove C02 , (3) a 

helium tank to purge dissolved 222Rn into the cell, (4) an 

alpha-scintillation cell, (5) a manometer to indicate the 

pressure inside the system during transfer of 222Rn from the 

bubbler to the alpha-scintillation cell and also to detect any 

leak in the system, and (6) a vacuum pump. With the 

bubbler stopcocks closed, evacuate the system and the 

alpha-scintillation cell to a vacuum of 10 mtorr. Close the 

stopcock to the vacuum pump and allow the system to 

equilibrate for about 2 min. If the manometer meniscus 

remains stable, connect the helium line (20.68-34.48 kilopascals) to the other side of the bubbler. Purge trapped air 

in the line between the helium tank and bubbler with helium 

gas by momentarily opening the 0-ring connection on the 

helium-line inlet a few times. Record the time (day, hour, 

and minute), then carefully open the bubbler-outlet stopcock to purge 222Rn directly into the alpha-scintillation cell. 

Allow the vacuum to equilibrate slowly; otherwise, an 

excessive risk exists of blowing the liquid sample from the 

bubbler into the drying tube. Continue the 222Rn purging by 

slowly opening the bubbler-inlet stopcock; check the frittedglass disk carefully for rising bubbles. Allow the pressure to 

increase slowly, control the manometer decrease rate, and 

complete purging in 10 to 15 min. Fill the cell to· 4 

millimeters of mercury less than the atmospheric pressure 

and close the cell stopcock. Close all other stopcocks in the 
QUARTZ WINDOW CEMENTED 

TO SCINTILLATOR BELL 

POLYURETHANE CENTERING 

RING AND SUPPORT 

HIGH -VOLTAGE AND SIGNAL 

CONNECTION TO AMPLIFIER 

AND COUNTER/TIMER 

LIGHT- PROOF METAL HOUSING 

ALPHA- SCINTILLATION CELL 

SURROUNDED WITH ELASTIC 

LIGHT- PROOF FELT 

SCINTILLATION -PHOTOMULTIPLIER 

TUBE 

TUBE BASE WITH PREAMPLIFIER 

Figure 88. An alpha-scintillation cell and light-proof housing. 

de-emanation system. Record the time (day, hour, minute). 

Quickly remove the bubbler from the assembly and open the 

outlet stopcock momentarily to release helium pressure. 

Tum off the room light; remove the alpha-scintillation cell 

for 222Rn-activity measurement. Measure the water volume 

inside the bubbler by using a graduated cylinder. 

Counting System for Radon-222 Activity 

The 222Rn-activity counting system consists of (1) an 

alpha-scintillation cell internally coated with silveractivated ZnS and having a quartz window 2 inches in 

diameter, (2) a scintillation-photomultiplier tube 3 inches in 

diameter, (3) a preamplifier connected to the scintillationphotomultiplier base, (4) an amplifier, (5) a scaler, counter, 

and timer, and (6) a high-voltage power supply. 

Before counting, tum off the room lights; remove the 

light shield from the alpha-scintillation cell, and place the 

cell in the light-proof counting chamber (fig. 88). Allow 

about 20 min for the 222Rn daughters to ingrow, then count 

the sample until 1 ,000 counts have been obtained. Flush out 

the 222Rn from the cell after obtaining the data. The 

detection limit is about 0.2 pCi/L for a 60-mL (milliliter) 

sample. 

Calibration of Alpha-Scintillation Cell and Equipment 

The counting efficiency of each alpha-scintillation 

cell varies between cells and between counting instruments. 

Consequently, counting efficiency of each alphascintillation cell was determined in each instrument in 

which it was used by counting 222Rn transferred from a 

bubbler containing a measured volume of 226Ra standard 

solution. A minimum of four or five bubblers containing the 

same standard enables four or five cells to be calibrated 

simultaneously. Use the following procedures. Pipet 10 mL 

of 10 pCi/mL 226Ra standard solution directly into each of 

four to five bubbler tubes and dilute with distilled water to 

60 percent full. De-emanate the bubbler to expel all 222Rn; 

after 1 month, de-emanate the standard again to determine 

the amount of 222Rn growth, and calculate the instrument 

and cell efficiency. Barring any spillage or breakage, the 

standards will last indefinitely and can be de-emanated to 

provide 222Rn calibration. The counting efficiency of the 

system used at the U.S. Geological Survey laboratory was 

in the range of 4. 9 to 5. 6 counts per minute per 1 pCi of 222Rn, with a background-count rate of 0.03 to 0.09 count 

per minute. 

RESULTS AND DISCUSSION 

The method is specific for 222Rn; no direct interferences occur. Radon-220 and 219Rn, if present, will have 

decayed completely by the time of the analysis because of 

their short half-lives, which are about 4 s for 219Rn and 

56 s for 220Rn. Normally, these constituents will not be 

supported by any substantial concentration of the parent 224Ra and 223Ra in the sample; thus, they usually are 

insignificant. 

Contamination of the alpha-scintillation cell can be a 

major problem. Ground water may contain large concentrations of dissolved 222Rn, which, if de-emanated into the 

alpha-scintillation cells and allowed to remain in them for 

several hours, will result in considerably increased background count rates. Increased background count rates of 

more than several tenths of 1 count per minute preclude the 

reuse of cells for the analysis of most environmental 

Sampling and Analysis of Dissolved Radon-222 in Water by the De-emanation Method 229 
Table 39. Transportation and storage loss of radon-222 

Sample type 

Original, low activity ................. . 

Original, high activity ................. . 

Transported, low activity .............. . 

Transported, high activity ............. . 

Stored, low activity .................. .. 

Stored, high activity .................. . 

1

Counting error is two standard deviations. 

Collected 

and shipped 

or stored 

1-10-79 

1-11-79 

1-10-79 

1-11-79 

1-10-79 

1-11-79 

Table 40. Precision of radon-222 in water analysis 

Measured mean Relative 

Sample1 Number concentration deviation 

of runs (picocuries 

per liter) (percent) 

1 ••••••• 0 ••••• 2 3.12 19 

2 ............. 3 48 5 

3 ............. 2 105 4 

4 ............. 3 756 3 

5 ............. 3 4,600 2 

6 ............. 3 8,160 1.5 

7 ............. 2 24,690 1.0 

1 Samples were prepared by precipitating 226Ra with barium sulfate 

twice, with minimal stirring, from 226Ra stock solutions stored for 2 

months after preparation. The clear solution was decanted as 222Rn water 

samples. 

samples. Therefore, 222Rn in the cells needs to be counted 

and flushed out immediately after the data are obtained. The 

contaminated cells can be disassembled, cleaned, and 

refabricated by using fresh phosphor and a new quartz 

window if necessary. 

Loss of Radon-222 

Analytical results for loss of 222Rn during transportation and storage for low- and high-activity samples are 

listed in table 39. The loss of 222Rn during transportation 

and storage, after 1 week, is negligible for a low-activity 

sample (within three standard deviations of counting 

errors); the loss of 222Rn during transportation and storage, 

for a high-activity sample after 1 week, indicates a loss of 

4 percent during transportation and no loss during storage. 

The 226Ra concentrations in both high- and low-activity 

samples also were measured and determined to be less than 

1 pCi/L for a low-activity sample and about 5 pCi/L for a 

high-activity sample. Therefore, contribution of 222Rn from 

230 Field Studies of Radon in Rocks, Soils, and Water 

Date 

Returned 

1-15-79 

1-17-79 

Analyzed 

1-10-79 

1-11-79 

1-16-79 

1-18-79 

1-16-79 

1-18-79 

222Rn 1 

(picocuries 

per liter) 

47.0±2.6 

8, 180±78 

54.5± 1.1 

7,850±77 

52.0± 1.1 

8,450±84 

226Ra 1 

(picocu ries 

per liter) 

<1 

5.41±0.21 

<1 

5.41 ±0.21 

<1 

5.41 ±0.21 

a 226Ra source can be neglected. The data presented here are 

limited; general conclusions are limited to the same degree. 

Precision 

Precision of the method may be expressed in terms of 

the relative deviation at different concentrations, as listed in 

table 40. The percentage deviation ranges from 19 percent 

for a sample concentration of less than 5 pCi/L to 1 percent 

for a 25 ,000-pCi/L sample concentration. 

SUMMARY 

Sample collection for determining the concentration 

of dissolved 222Rn in surface water is performed best by 

placing one end of an evacuated bubbler into the water and 

then drawing a water sample directly into the main chamber 

of the bubbler until the bubbler is about 60 percent full. For 

collection of ground-water samples, a peristaltic or submersible pump is needed to supply an unaerated water 

sample through a short, flexible tubing connected to one 

end of the evacuated bubbler until the main chamber is 

about 60 percent full. Loss of 222Rn during transportation 

from the sampling site to the laboratory (within 1 week) was 

negligible for low-activity samples and was 4 percent for 

high-activity samples. The direct de-emanation and alphascintillation counting method described in this report is 

sensitive (0.2 pCi/L for a 60-mL sample) and has a better 

precision than other methods for analysis of most environmental samples. 

REFERENCES CITED 

Environmental Protection Agency, 1983, Radionuclides in the 

interim regulation, and other radionuclides under consideration: Federal Register, v. 48, no. 194, p. 45520. 

Yang, I. C. , 1984, Improved method for the determination of 

dissolved 226Ra, in Vogt, J.R., ed., Proceedings of the 5th 

International Conference on Nuclear Methods in Environmental and Energy Research, Puerto Rico: U.S. Department 

of Energy ONF-840408, p. 191-201. 
A COMPARISON OF TWO TECHNIQUES FOR RADON-222 MEASUREMENT 

IN WATER SAMPLES 

Ann Mullin and Richard B. Wanty 

Abstract 

As the level of concern over radon-222 in water 

supplies rises, it will become increasingly important to 

have established a set of reliable techniques for the 

measurement of radon-222 in water. Several different 

techniques are available currently, but for the most part 

these have not been compared against one another in the 

field. Rather, most validation techniques involve laboratory calibration against synthetic standards. Although 

interlaboratory studies are certainly necessary, a field 

intercomparison is equally important, as it tests all aspects 

of the measurement, including sample collection, storage, 

and analysis, as well as correction for the lag time between 

sampling and analysis. We report here on a field test of 

two different techniques: liquid scintillation and a technique in which the sample is degassed in the field and 

then measured in a Lucas cell. 

The purpose of this field test was to compare the 

direct results from the two methods and to test the 

reproducibility or consistency of the two methods over a 

period of time after sampling. In the first part of the study, 

the results were in moderately good agreement, although 

large relative deviations existed between some samples. A 

comparison of the samples measured at various lag times 

between sampling and analysis showed very good consistency for the liquid scintillation method and poor consistency for the degassing Lucas cell method. 

INTRODUCTION 

Much emphasis is now being placed on radon-222 

e22Rn) both in air and water. One reason for this emphasis 

is the fact that the Environmental Protection Agency (EPA) 

is expected to issue a maximum contaminant level (MCL) 

for 222Rn in drinking water soon. Unofficial guideline levels 

now being used range as high as 10,000 pCi/L (picocuries 

per liter) in water, but it is likely that the EPA will set the 

MCL at a lower level. The "action level" (level at which 

remedial action should be taken) for 222Rn in air is 4 pCi/L. 

For 222Rn, most of the danger comes from inhalation, 

but it is well known that high levels of 222Rn in a water 

supply can contribute to indoor airborne 222Rn (Nazaroff 

and others, 1988; Hess and others, 1986, 1990; Lawrence 

and others, in press). Studies have shown that virtually all 

of the 222Rn in the air of a home may come from the water 

supply (Lawrence and others, in press). In natural environments, 222Rn concentrations have been measured as low as 

< 10 pCi/L in surface water supplies to as high as 2 x 106 

pCi/L in a private well in Maine (Aieta and others, 1987). 

Cothern ( 1987) stated "The average concentration of radon 

in these [U.S. public] water supplies generates a lifetime 

risk of about 1 in 10,000, the highest level of risk allowed 

for any contaminant currently regulated under the Safe 

Drinking Water Act." 

Along with considering the health risks, the extent of 

occurrence, and methods and costs for removal of the 

contaminant, the EPA must take into consideration the 

methods and costs for detection of the contaminant before 

setting an MCL. 

Several different analytical techniques are currently 

in use. The three most common are the bubbler Lucas cell 

(LC), liquid scintillation (LS), and degassing Lucas cell 

(DLC) methods. Each has advantages and drawbacks, in 

terms of accuracy, precision, sample throughput, and cost. 

The EPA conducted a study with 28 participating laboratories to compare the LC and LS methods (Whittaker and 

Akridge, 1986). This study was limited to a test of 

laboratory techniques and did not consider any variability 

that may arise as a result of sampling techniques in the field. 

The results of the study are summarized in table 41. Both 

methods, being considered valid and equivalent, have been 

approved by the EPA. 

Thus far, little attention has been directed at comparing field sampling and analytical techniques. In this study, 

samples were collected from 17 private domestic wells and 

two springs in the Colorado Front Range and analyzed by 

the LS and DLC methods. In addition, a systematic study of 

the effects of the lag time between sample collection and 

analysis was performed. These results and a comparison of 

the two methods are presented in this paper. 

METHODS 

The LS technique is described in detail here. For a 

description of the DLC technique, see Reimer (this volume). The two techniques differ greatly in the sampling 

method as well as in the analytical approach. The LS 

technique requires a liquid sample that is agitated with a 

scintillation cocktail and therefore measures the radioactivity of the water sample directly. In the case of the DLC 

method, the sample is agitated in a closed vessel to extract 

the 222Rn, and the radioactivity of the gas is measured. 

In the LS method, energy from the radioactivity of 

the sample excites the fluor, which in turn gives off photons 

that can be measured by a photomultiplier tube. A mineraloil-based cocktail is used that contains PPO (2,5-

Diphenyloxazole) as the primary fluor and bis-MSB (pbis-lo-Methylstyrylbenzene) as the secondary fluor (New 

England Nuclear Corp., oral commun., 1988). 

A Comparison of Two Techniques for Radon-222 Measurement in Water Samples 231 
Table 41. Comparison of liquid scintillation (LS) and Lucas cell (LC) methods by the EPA, with the cooperation of 28 

privately owned laboratories (Whittaker and Akridge, 1986) 

[All values are given in picocuries per liter; accuracy and precision comparisons are given at the 95-percent confidence level] 

Known value ........................................ . 

LS method .......................................... . 

LC method .......................................... . 

Average accuracy .................................... . 

Average repeatability (within laboratory precision) ..... . 

Average reproducibility (combined within and 

between laboratory precision) ....................... . 

Five mL (milliliters) of cocktail and 10 mL of sample 

are placed in a 20-mL scintillation vial and capped with a 

poly seal. Samples are taken in duplicate to check the 

sampling and counting precision as well as to give an 

average instead of a single result. Details of the sampling 

procedure are given in U.S. Geological Survey technical 

memorandum 88.02 from the Office of Water Quality (L.D. 

Cecil and I.C. Yang, written commun., 1988) as well as in 

EPA/EERF Manual 78-1. Samples are held for 3 h (hours) 

before counting takes place so the 222Rn can equilibrate 

with its short-lived progeny e18Po, 214Pb, 214Bi, and 

214Po). 

Radium-226, NBS-traceable, is used to prepare the 

standards. The EPA has shown in their studies (Horton, 

cited in Environmental Protection Agency, 1983) that 226Ra 

remains in the aqueous layer and does not contribute 

significantly to the count rate. The only counts from 226Ra 

will occur at the interface between the aqueous solution and 

the mineral-oil cocktail. 

A series of standards ranging from 100 pCi/L to 

200,000 pCi/L is prepared and held for 21 days to allow for 

ingrowth of 222Rn. At this time, the 226Ra and 222Rn are 

considered to be in secular equilibrium. Blanks are prepared 

with distilled water and, along with the standards, are 

counted at intervals with the samples collected in the field. 

A blank or standard is counted after every tenth field 

sample. Counting time is 50 min (minutes) or more. The 

three alpha particles and two beta particles emitted from 

222Rn and its progeny are all counted. However, this effect 

is offset because the standards that are counted and used in 

the calculations all contain the same emitters. 

The 222Rn concentration in the sample is expressed in 

picocuries per liter by the following equation 

(Environmental Protection Agency, 1983 ): 

222 Net cpm of samples x 1 ,000 

where Rn Conversion factor x decay factor x 10 

Net cpm (counts per minute) of sample = gross cpm -

background cpm; 1,000 converts milliliters to liters; 

conversion factor in cpm/pCi = (net cpm of standard)/ 

e22Rn activity of standard); 

232 Field Studies of Radon in Rocks, Soils, and Water 

Sample A Sample B 

1,616±49 16,321±501 

1,519±170 15,746±1,100 

1,647±261 16,769±2,485 

LS Method 

95.2±2.0% 

3.6±3.0% 

10.2±4.2% 

Sample C 

66,426 ± 2,034 

62,945±6,600 

64,516± 12,017 

LC Method 

100.7±4.6% 

6.4±3.8% 

17.6±4.2% 

decay factor= e -x.r where X. equals 7.54X 10-3 h- 1, 

and t is the lag time between sample collection and 

analysis in hours; and 

10 is the volume of sample in milliliters. 

RESULTS AND DISCUSSION 

For this comparison, 17 wells and 2 springs were 

sampled from crystalline aquifers along the Front Range 

west of Denver, Colo. Concentrations of 222Rn ranged from 

1,080 pCi/L to 45,000 pCi/L (table 42). The distribution of 

samples is shown in figure 89. As seen in the figure, most 

of the samples are less than 5,000 pCi/L; the average of all 

the samples was approximately 9,000 pCi/L. Figure 90 

Table 42. The results of this study comparing the liquid 

scintillation (LS) and degassing Lucas cell (DLC) methods 

[The column labeled "Average" contains the arithmetic average of the 

values obtained by the two methods; all values are given in picocuries per 

liter; the percent deviation is calculated from the formula ((DLC-LS)/ 

DLC)xlOO] 

Sample no. DLC LS Average Percent 

deviation 

88C0-1 3,100 2,200 2,600 30 

88C0-2 3,500 2,300 2,900 34 

88C0-3 1,700 1,200 1,400 27 

88C0-4 2,100 1,200 1,600 43 

88C0-5 4,400 2,400 3,400 44 

88C0-6 1,100 1,100 1,100 6.3 

88C0-7 16,000 19,000 18,000 -16 

88C0-8 20,000 16,000 18,000 21 

88C0-9 43,000 47,000 45,000 -8.1 

88C0-10 ....... 13,000 6,600 9,600 47 

88C0-11 ....... 13,000 14,000 14,000 -6.3 

88C0-12 ....... 12,000 10,000 11,000 20 

88C0-13 ....... 3,400 2,300 2,900 32 

88C0-14 ....... 2,200 2,300 2,200 -2.3 

88C0-15 ....... 4,200 3,300 3,800 22 

88C0-16 ....... 4,500 4,200 4,400 7.1 

88C0-17 ....... 3,600 3,800 3,700 -3.6 

88C0-18 ....... 19,000 20,000 20,000 -5.2 

88C0-19 ....... 8,400 6,800 7,600 19 
1/) 

(I) 

Q. 

E 

m 

(/) 

0 

Q; 

..0 

E 

::I 

z 

12 

10 

5,000 10,000 15,000 20POO 25,000 3o,OOO 35,000 40,000 45,000 SQOOO 

Average 222Rn Value 

Figure 89. Distribution of radon-222 concentrations found 

in samples collected from 19 wells and springs in Colorado. The values shown are the average between the 

liquid scintillation (LS) and degassing Lucas cell (DLC) 

methods. Values are in picocuries per liter. 

shows a comparison of the results of the two methods. In 

some cases, the agreement is very good, but a few samples 

have significant relative deviations. In 13 of the 19 samples, 

the DLC method measured higher values than the LS 

method. For the LS method, all 19 samples were collected 

and analyzed in duplicate and, except for the first sample, 

showed very good precision. For the DLC method, 

duplicates were collected and promptly analyzed at 3 of the 

19 sites. 

The stability over time of the DLC method was tested 

by collecting several samples at each of two sites. These 

two sites were chosen because they represented a wide 

range of dissolved 222Rn values. For each site, the analysis 

was repeated after the time intervals specified in table 43. 

The lag time between sampling and analysis was 

compensated for by using the exponential formula given 

earlier in this paper. The results are displayed graphically in 

figure 91. In both cases, increased lag time led to greater 

uncertainty and usually lower values, both of which indicate 

that variable amounts of loss of 222Rn took place from the 

syringes in which the samples were stored. 

The stability over time of the LS method also was 

tested but in a different way. Unlike the DLC method, in 

which the sample is lost once it is counted, the samples in 

the LS method can be recounted over a period of time, 

provided that adjustments are made for the lag time between 

sample collection and analysis. These results are shown in 

table 44 and figure 92. As is indicated, increased lag time 

50,000 

40,000 

't:J 30,000 0 

..c 

-(I) 

:E 

en 20,000 ...I 

10,000 

10,000 20,000 30,000 40,000 50,000 

DLC Method 

Figure 90. Comparison of analyses for radon-222 by the 

liquid scintillation (LS, vertical axis) and degassing Lucas 

cell (DLC, horizontal axis) methods. The line represents 

the ideal 1:1 correspondence. All values shown are in 

picocu ries per liter. 

from sampling to analysis for periods of up to 7 days shows 

no loss of 222Rn. This appears to be true for samples that 

have 222Rn concentrations as low as 1 ,000 pCi/L. For this 

study, counting was not extended beyond 7 days. 

The LS method is well established, but the DLC 

method has been used less widely. The principal advantage 

of the DLC method is that results can be obtained in the 

field, at each site. Thus, the DLC technique provides for 

easy, rapid reconnaissance, although it has a larger relative 

error. The LS method, on the other hand, is probably more 

reliable but presents logistical problems because the instrumentation cannot be taken into the field. 

When the two techniques are examined side by side, 

several differences are evident. A close look at these 

procedural differences may point out sources of relative 

error between the two techniques. In the DLC method, a 

known volume of water sample is degassed in the field in a 

closed vessel. The air in the head space of that vessel is 

collected in a syringe, where it is stored until measurement. 

Radon-222 in the air sample is measured after the sample is 

injected into a calibrated Lucas cell. In the LS method, a 

known volume of water sample is introduced to a scintillation vial that contains the scintillating cocktail. The vial is 

tightly sealed until it is counted. In either case, excessive 

degassing of the sample during collection would lead to an 

erroneously low value. In the DLC method, the syringes 

used are probably not tight enough to prevent the slow 

escape of 222Rn, which would lead to a low value. In this 

A Comparison of Two Techniques for Radon-222 Measurement in Water Samples 233 
3000 

A 

~ 

= k 2000~ II 

1 II II 

II 

·a 1000 

.a 

I m 

0 I 

0 ro 100 1.50 200 

'lime, in hours 

20000~------~~--------~~------~~------~ 

B 

~ • 18000 ~ 

= k • • 1 16000 

•• • 

14000 

·a 

.a • 

I 12000 

• 

10000 I I 

0 ro 100 1.50 200 

'lime, in hours 

Figure 91. The effect of lag time on the measurement of 

radon-222 in replicate samples from sites 88C0-7 (A) and 

BBC0-4 (B), collected and analyzed by the degassing 

Lucas cell (DLC) method. The values shown are in picacuries per liter after being corrected for the lag time 

between sampling and analysis. 

sense, the LS method provides for greater sample stability 

over time because of the fewer number of sample transfers 

between containers (two for DLC, one for LS). In both 

techniques, standards are used to calibrate the counting 

equipment so that a conversion factor from counts per 

minute to picocuries per liter can be obtained. Nevertheless, 

the DLC technique leaves more room for error in the 

calibration phase because the short-lived daughters of 222Rn 

may not be adequately accounted for. If this is the case, 

erroneously high values may result from use of the DLC 

method. 

CONCLUSIONS 

This study provided a field intercomparison of two 

methods for measurement of 222Rn in water samples. 

Although there are significant differences in the sample 

234 Field Studies of Radon in Rocks, Soils, and Water 

... 

G) 

= ... 

G) 

a. 

(/) 

G) 

'i: 

:I 

u 

0 

u 

·a 

.5 

c 

a: 

3000 ....----.,----.,----.----· 

2500 

2000 

1500 

1000 ~ 

88C0-13 

500 

o~~_.~~~._~~_.~~~._~~_.~ 

0 50 100 150 200 

Time, in hours 

Figure 92. The effect of lag time on the measurement of 

radon-222 in replicate samples from sites BBC0-13 and 

BBC0-14, collected and analyzed by the liquid scintillation 

(LS) method. The values shown are in picocuries per liter 

after being corrected for the lag time between sampling 

and analysis. 

collection and analytical methods, moderately good agreement was obtained between the two methods when the DLC 

samples were analyzed after short lag times (<8-12 h). 

Table 43. Effect of increasing lag time on the measurement of radon-222 in water samples by the degassing 

Lucas cell (DLC) method 

[For each sample, the first measurement is taken to be the most reliable by 

this method] 

Lag time 

(in hours) 

Sample 88C0-4 

4 .......................... . 

21.5 ......................... . 

45.5 ......................... . 

93 .......................... . 

93 .......................... . 

144 ......................... . 

Sample 88C0-7 

8.3 ......................... . 

21.7 ......................... . 

29 .......................... . 

45.8 ......................... . 

69.8 ......................... . 

71 .......................... . 

94 .......................... . 

94.8 ......................... . 

222Rn 

(in picocuries per liter) 

2,100 

2,100 

1,600 

1,200 

1,600 

590 

16,000 

15,000 

16,000 

15,000 

16,000 

18,000 

13,000 

11,000 
Table 44. Effect of increasing lag time on the measurement of radon-222 in paired water samples by the liquid 

scintillation (LS) method 

Lag time 

(in hours) 

Sample SSC0-14 

3.5, 4.5 ......................... . 

22.5, 23.5 ........................ . 

47.75, 48.75 ...................... . 

73.0, 74.0 ........................ . 

98.25, 99.25 ...................... . 

123, 124. . ........................ . 

142.75, 143.75 ..................... . 

171.5, 172.5 ....................... . 

Sample SSC0-13 

13.75, 15.0 ....................... . 

24.0, 25.0 ........................ . 

45.0, 46.0 ........................ . 

76.5, 77.5 ........................ . 

97.5, 98.5 ........................ . 

222Rn 

(in picocuries per liter) 

2,600, 2,700 

2,500, 2,500 

2,500, 2,600 

2,600, 2,600 

2,400, 2,500 

2,400, 2,400 

2,400, 2,600 

2,700, 2,700 

970, 900 

1,000, 1,000 

1,100, 960 

970, 930 

950, 930 

Large relative deviations were encountered when the lag 

time for the DLC method was greater than 12 h. 

The principle advantage of the DLC method is that 

results can be obtained in the field at each site. On the other 

hand, the DLC method is seen as a reconnaissance 

technique. If, for instance, the samples are not immediately 

analyzed in the field, problems develop. First, the syringes 

may not be tight enough to prevent the slow escape of 222Rn 

from the gas sample. Second, the short-lived progeny of 222Rn, specifically 218Po, closely approaches secular 

equilibrium with 222Rn in about 10 min. The activity of this 

daughter may not be accounted for adequately in the 

calibration scheme. Further, because the DLC analysis is 

performed at a time when the net alpha activity of 218Po is 

rapidly building, large random errors may result. 

Although the LS method does not give immediate 

onsite results, the results of this study indicate that the LS 

method is more accurate. First, there are fewer sample 

transfers between containers (two for DLC, one for LS), 

and the vials are more tightly sealed between collection and 

analysis. Second, the standards used in the calibration phase 

of the LS method contain 222Rn in equilibrium with its 

progeny; the same is true for the samples. Thus, the activity 

of these daughters is adequately accounted for. 

Experiments in which large lag times between sample 

collection and analysis were used showed that the LS 

method is much more stable than the DLC method. This 

observation further supports the conclusion that the syringes 

used to hold the samples in the DLC method are not 

completely impervious to 222Rn escape. The most effective 

use of the two techniques is as follows: the DLC method is 

useful for reconnaissance sampling, where interim results 

may help to design a sampling grid, but the LS method is 

preferred for providing more reliable results. 

REFERENCES 

Aieta, E.M., Singley, J .E., Trussell, A.R., Thorbjamarson, 

K.W., and McGuire, M.J., 1987, Radionuclides in drinking 

water: An overview: Journal of the American Water Works 

Association, v. 79, p. 144-152. 

Cecil, L.D., and Yang, I.C., 1988, Report on guidelines for 

sampling and analysis for dissolved radon-222 in ground 

water and surface water: U.S. Geological Survey Office of 

Water Quality Technical Memorandum 88.02. 

Cothern, C.R., 1987, Estimating the health risks of radon in 

drinking water: Journal of the American Water Works 

Association, v. 79, p. 153-158. 

Cross, F.T., Harley, N.H., and Hoffman, W., 1985, Health 

effects from 222Rn in drinking water: Health Physics, v. 48, 

p. 649. 

Environmental Protection Agency, 1983, Methods and results of 

EPA's study of radon in drinking water: EPA 520/5-83-027. 

Hess, C.T., Korsah, J.K., and Einloh, C.J., 1986, Radon in 

houses due to radon in potable water, in Hopke, P.K., ed., 

Radon and its decay products-Occurrence, properties, and 

health effects: American Chemical Society Symposium 331, 

New York, N.Y., April 13-18, 1986. 

Hess, C.T., Michel, J., Horton, T.R., Prichard, H.M., and 

Coniglio, W .A., 1985, The occurrence of radioactivity in 

public water supplies in the United States: Health Physics, v. 

48, no. 5, p. 553-586. 

Hess, C.T., Vietti, M.A., Lachapelle, E.B., and Guillemette, 

J.F., 1990, Radon transferred from drinking water into house 

air, in Cothern, C.R., and Rebers, P.A., Radon, radium, and 

uranium in drinking water: Chelsea, Mich., Lewis 

Publishers, Inc., p. 51-68. 

Lawrence, E.P., Wanty, R.B., and Nyberg, P.A., in press, 

Contribution of 222Rn in domestic water supplies to 222Rn in 

indoor air in homes in Colorado: Health Physics. 

Nazaroff, W.W., Doyle, S.M., Nero, A.V., Jr., and Sextro, 

R.G., 1988, Radon entry via potable water, in Nazaroff, 

W.W., and Nero, A.V., Jr., Radon and its decay products in 

indoor air: New York, N.Y., John Wiley and Sons, p. 

131-160. 

Whittaker, E.L., and Akridge, J.D., 1986, Methods validation 

report (radiation): Environmental Protection Agency Annual 

Report, Fiscal Year 1986. 

A Comparison of Two Techniques for Radon-222 Measurement in Water Samples 235 

PART 2: STUDIES OF RADON IN WATER 

SECTION 3: FIELD STUDIES OF RADON IN SURFACE AND GROUND WATERS 

USE OF RADON MEASUREMENTS IN CARTERS CREEK, MAURY COUNTY, TENNESSEE, 

TO DETERMINE LOCATION AND MAGNITUDE OF GROUND-WATER SEEPAGE 

Roger W. Lee and Este F. Hollyday 

Abstract 

The location and magnitude of ground-water seepage to streams can be determined by measuring the 

activity of radon-222 in streamflow. Radon activity in 

ground water may be 2 to 4 orders of magnitude greater 

than in surface water. Thus, ground-water seepage to a 

stream usually results in increases in localized radon-222 

activity in the streamflow. Downstream of ground-water 

seepage, radon-222 activity decreases in the stream as 

radon escapes to the atmosphere, particularly in turbulent 

reaches of the stream. The relation between ground-water 

and surface-water flows can be determined by mass balance if it is assumed that no other radon-222 sources exist 

and no significant gas loss from the mix of surface water 

and ground water takes place at the sampling point. 

Measurements of radon-222 activity in water from a 

0.75-mile reach of Carters Creek, a small bedrock-channel 

stream in Maury County, Tenn., ranged from 32 to 196 

disintegrations per minute per liter. A sample of ground 

water from an adjacent spring contained radon-222 activity 

of 489 disintegrations per minute per liter. On the basis of 

radon-222 activities down the sampled reach of the 

stream, during low base-flow conditions 36 percent of 

flow leaving the reach was ground-water seepage at a 

point 0.5 mile downstream from the upper sampling 

boundary. Measurements of temperature in the water of 

the stream verified the point location of ground-water 

seepage. Subsequent measurements of radon-222 activities and streamflow in Carters Creek at higher base-flow 

conditions indicated two gaining sections of stream, 

which were receiving about 0.3 cubic foot per second 

ground-water seepage in the upper reach and about 0.2 

cubic foot per second ground-water seepage in the lower 

reach. 

INTRODUCTION 

Measurements of radon-222 e22Rn) activity in water 

from stream-aquifer hydrologic systems have been successfully used to characterize ground-water seepage to rivers 

and streams (Rogers, 1958; Jacoby and others, 1979). If 

measurements of streamflow are combined with measurements of 222Rn activities in surface water and ground water, 

quantitative analysis of ground-water seepage to a stream is 

possible. Ellins and others (1985, 1990) have shown the 

applicability of this approach to stream-carbonate aquifer 

interactions in Jamaica and Puerto Rico. 

This report describes the results of a study to apply 

the method in the reconnaissance of small gaining streams 

in the Ordovician limestone areas of middle Tennessee. 

Determination of points of discharge and quantity of 

ground-water seepage could be useful for locating potential 

ground-water supplies as well as for quantifying base-flow 

components of streams. Two surface-water flow measurements and 11 measurements of 222Rn activities were taken 

in Carters Creek, Maury County, Tenn., during periods of 

base flow in the summer of 1986 (fig. 93). Additionally, six 

surface-water flow measurements and six 222Rn activities 

were measured in Carters Creek during a higher low-flow 

condition in February 1987 (fig. 94). 

RADON CYCLING IN GROUND-WATER AND 

SURFACE-WATER SYSTEMS 

Radon-222 occurs naturally in the Earth's crust as a 

daughter of the radioactive decay of radium-226 e26Ra). 

The concentration of 222Rn in ground water is primarily 

related to the amount of 226Ra present in the aquifer matrix, 

especially near grain boundaries or in coatings on grains or 

fractures, although hydrology and structural geology may 

exert some influences. Activities may range from 100 

dpm/L (disintegrations per minute per liter), typical of 

water in clastic sedimentary rocks, to greater than 10,000 

dpm/L, typical of water in igneous or metamorphic rocks. 

The activity of 222Rn in the atmosphere is almost nil. Thus, 

as ground water containing 222Rn seeps into surface-water 

bodies, 222Rn escapes to the atmosphere across the air-water 

interface, and the concentration of 222Rn in surface water 

decreases rapidly. Activities of 222Rn in water from an 

aquifer may be 2 to 4 orders of magnitude greater than 

activities in an adjacent surface-water body (King and 

others, 1982). Radon-222 is therefore suitable for determining the ground-water discharge to surface-water systems. 

Several factors that control 222Rn activity in water 

should be considered for this determination: 

1. The difference in activity of 222Rn between ground water 

and adjacent stream water. 

Radon Measurements in Carters Creek, Maury County, Tennessee 237 
. 

;· 

'-·· 

0 

0 

• 

.196 

. . 

-..... .. '\ . 

I 

I 

0.5 MILE 

0.5 KILOMETER 

EXPLANATION 

EFFECTIVE SUBBASIN 

BOUNDARY AT LOW 

FLOW 

SITE OF STREAMFLOW 

MEASUREMENT 

SITE OF 222Rn ACTIVITY 

MEASUREMENT --Number 

is disintegrations per 

minute per liter 

Figure 93. Locations of measurements of surface-water discharge and radon-222 activities 

for September 16-17, 1986, in Carters Creek. 

238 Field Studies of Radon in Rocks, Soils, and Water 
. 

"-·· .-...,. .. 

0 0.5 MILE 

0 0.5 KILOMETER 

EXPLANATION 

- • ·- EFFECTIVE SUBBASIN 

BOUNDARY AT LOW 

FLOW 

r 615 SITE OF SPRING 

MEASUREMENT--

Number is 222 Rn activity 

in disintegration per 

minute per liter 

... 83 .. 9•

91 SITE OF STREAMFLOW 

MEASUREMENT--

Top number is 222 Rn 

activity in disintegration 

per minute per liter; 

bottom number is 

discharge in cubic feet 

per second 

Figure 94. Locations of measurements of surface-water discharge and radon-222 activities for February 12, 

1987, in Carters Creek. 

Radon Measurements in Carters Creek, Maury County, Tennessee 239 
2. The magnitude of a ground-water seep in relation to total 

flow along a reach of stream. 

3. The rate of gas loss in the stream (gas-exchange rate) 

based on temperature, diffusion, turbulence, and surface 

area of air-water interface relative to stream volume 

(Eisinger and Moore, 1983). 

4. The length of the stream reach measured and the number 

of ground-water discharge points. 

5. The contribution of flow and 222Rn from tributaries to 

the main channel. 

6. The characteristics of ground-water seepage (discrete or 

dispersed discharge). Factors 1 and 2 are most significant in determining suitability of this method to groundwater and surface-water systems. Factors 3 through 6 are 

determined subsequently by application of the method to 

the specific system. 

CHARACTERIZATION OF BASE FLOW 

Ground-water seepage may occur as a dispersed 

discharge into the stream channel along a given length of 

channel. This type of seepage is typical of channels flowing 

on granular material. Seepage also may be discrete, which 

means it contributes flow at well-defined points along the 

stream. Discrete seepage is typical of channels that flow on 

soluble bedrock, fractured bedrock, or faulted and fractured 

rock. 

The relation between ground-water and surface-water 

flows for a reach of stream as determined by use of 222Rn 

activities is defined by the mass balance mixing equation 

(1) 

where 

Qs =the rate of streamflow, in cubic feet per second; 

As=the activity of 222Rn in streamflow at upstream 

point, in disintegrations per minute per liter; 

Qgw=the rate of ground-water seepage, in cubic feet per 

second; 

Agw=the activity of 222Rn in ground water, in disintegrations per minute per liter; 

Qm=the rate of mixed streamflow and ground-water 

flow downstream, in cubic feet per second; 

Am=the activity of 222Rn in mixed water downstream, 

in disintegrations per minute per liter; and 

Qs+Qgw=Qm. (2) 

Equation 1 assumes no other source of 222Rn other than that 

conveyed to the stream from ground water and also assumes 

no significant loss of 222Rn from the mix of surface and 

ground water at the sampling point. Thus, measurements of 

streamflow and 222Rn activity in the stream and in groundwater sources allow calculation of the magnitude of groundwater seepage. 

240 Field Studies of Radon in Rocks, Soils, and Water 

In the absence of streamflow measurements, a proportional value of ground-water seepage may be determined. Substitution of equation 2 into equation 1 for Qs 

yields 

Qgw Am-As 

Qm Agw-As. (3) 

This form of the equation permits use of 222Rn 

activities to determine the ratio of ground-water seepage to 

the total streamflow at the measured point. Equation 3 is 

subject to the same limitations discussed for equation 1. 

APPLICATION TO CARTERS CREEK, TENNESSEE 

Carters Creek is a small stream that has a low base 

flow of about 1.0 fe/s (cubic foot per second) and an 

average annual flow of about 17 fe/s. The stream is incised 

through regolith, and much of the streambed is on thinbedded, clay-rich limestone of Ordovician age. At low 

base-flow conditions, the streamflow is characterized by 

long, shallow pools and short riffles. The stream channel of 

the sampled reach is relatively straight, and, during higher 

flows (10 fets or greater), the riffles become submerged 

and flow is more uniform. 

A base-flow survey conducted June 26, 1986, in 

Maury County, Tenn., indicated that a substantial increase 

in flow in the uppermost reach of Carters Creek was from 

ground-water seepage (Lowery and others, 1987). Subsequently, a reconnaissance sampling of 222Rn activities along 

this reach of Carters Creek under low base-flow conditions 

(1 fe/s) was conducted on September 16, 1986 (fig. 93). No 

significant surface-water inflow from tributaries was 

observed along the sampled reach of stream. 

A second base-flow survey of 222Rn activities was 

conducted on February 12, 1987, during high base-flow 

conditions (10 fe/s) in order to compare the two base-flow 

extremes. Streamflow measurements also were made, along 

with the 222Rn measurements, to better quantify groundwater discharges under the prevailing hydrologic conditions. 

METHODS 

Water samples of approximately 200 mL (milliliters) 

were collected from surface-water sites in Carters Creek and 

one adjacent spring (fig. 93). The samples were drawn into 

evacuated samplers where radon gas was vacuum stripped 

from the water into calibrated Lucas cells. The activity of 222Rn was determined by alpha spectrometry by use of 

commercially available equipment. Sufficient length of 

counting period and repetition of counting events produced 

an analytical error of less than 3 percent for all samples. 

Samples were collected in midstream, about 6 to 12 in 

(inches) below the water surface, where there would be 
Vl 

z 

0 

..... 

<( 

a; 

C>a; 

LLILLJ 

.......... 

z-_ _. 

Vl 

-a; 

Cw 

za.. 

LLJ ....... 

C:::::> 

o:z 

NN~ 

N 

a; 

u_LLJ 

ca.. 

200 

160 

120 

80 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

Stream 

temperature 

14 

16 

18 

20 

V) 

::::> 

Vl 

_. 

LLJ 

u 

Vl 

LLJ 

LaJ 

a; 

C) 

LLJ 

c 

z 

.. LLJ 

a; 

::::> 

..... 

<( 

a; 

>-

..... 40 

I Activity of 

, r--222 Rn in 

'\ J stream 

LLJ 

a.. 

~ 

LLJ > ..... 22 

1-

u 

'-----

<( 

0 24 

0 1,000 2,000 3,000 4,000 

DOWNSTREAM DISTANCE, IN FEET 

Figure 95. Stream temperatures and radon-222 activities in a 0.75-mile reach of Carters Creek for September 

16-17, 1986. 

optimum mixing of ground and surface waters. Collection 

points were usually just upstream of riffles, at the end of a 

pool or flow channel, and just downstream of riffles, at the 

head of a pool or flow channel. Occasionally, samples were 

collected in the middle of a pool to determine intermediate 

222R . . . . h 1 n activities m t e poo . 

RESULTS AND DISCUSSION 

In the initial sampling of Carters Creek in September 

1986, the activities of 222Rn ranged from 32 to 196 dpm/L 

(fig. 93). An adjacent spring produced water that contained 

489 dpm/L, or, for the only reach of stream increasing in 

222Rn activity, 

As=34 dpm/L, 

Agw=489 dpm/L, 

Am= 196 dpm/L. 

Substitution into equation 3 yields 

~:=0.36, 

meaning that about 36 percent of the total flow downstream 

of the lowermost pool entered the stream at that pool. 

Stream temperatures and an intermediate 222Rn measurement were used to verify the seepage of ground water into 

the pool (fig. 95). Ground-water discharge to the pool was 

estimated to be about 0.6 ft 3

/s (Lee and Hollyday, 1987). 

The second sampling of Carters Creek, on February 12, 

1987 (fig. 94), produced lower 222Rn activities and a 

narrow range of values (72 to 90 dpm/L in the main 

channel). Streamflow measurements showed only one possible gaining section (0. 3 fe /s), which was in the middle of 

the reach of stream sampled. Radon activities from this 

sampling indicate two middle-reach gains from groundRadon Measurements in Carters Creek, Maury County, Tennessee 241 
water seepage and some seepage of ground water into the 

same lower pool that had seepage during the September 

1986 sampling. A second measurement of the adjacent 

spring indicated water with a 222Rn activity of 615 dpm/L, 

compared to the previous value of 489 dpm/L. This variance cannot be explained at present; 615 dpm/L will be used 

for Agw for the computations to follow. 

Solution of equation 3 for the middle reach shows that 

about 2.4 percent of the streamflow was from ground-water 

seepage along the middle reach. For Qm of 10.4 fe/s, 

Qgw=0.252 fe/s. 

This value is very close to the 0.3 ft3/s gain shown by 

streamflow measurements. 

Further refinement can be obtained by considering the 

input of tributary flow and its 222Rn activity in a modification of equation 1 to 

where 

Qt =the rate of tributary flow, in cubic feet per second, 

and 

At =the activity of 222Rn in tributary above confluence, 

in disintegrations per minute per liter. 

In solving for Qgw• 

Qgw = 0.256 fe/s, 

or a difference of0.004 fe/s, which is a negligible quantity, 

considering the errors of the streamflow measurements and 

the radon-measuring procedures as applied here. 

However, at the lower reach, 222Rn activity increased 

from 72 to 83 dpm/L, and this increase indicates groundwater seepage to the stream, although no significant gain in 

flow is apparent (9.90 to 9.91 fe/s). From equation 3, 2.07 

percent of total streamflow is gained in this reach, or about 

0.2 fe/s. This figure indicates that streamflow measurements are not sensitive enough to detect this small inflow or 

that streamflow also is lost to an aquifer as ground water is 

gained in the stream. 

242 Field Studies of Radon in Rocks, Soils, and Water 

These results are based on the premise that all data 

used are without error, although streamflow measurements 

may contain up to 5 percent error. Data collected on both 222Rn and streamflow can be refined statistically and with 

more sophisticated measuring techniques. The use of three 

significant figures for 222Rn activities measured in this 

investigation may be somewhat questionable. However, 

these data do demonstrate variabilities of 222Rn activities in 

the stream and how measurements of streamflow and 222Rn 

activity can be used to locate and quantify points of 

ground-water seepage to streams. 

REFERENCES CITED 

Ellins, K.K., Douglas, E., Simpson, H.J., and Mathieu, S., 1985, 

The relationship between the isotope composition of precipitation and hydrologic systems in Jamaica and the application 

of 222Rn in measuring ground-water discharge to the Martha 

Brae River, Jamaica: Caribbean Islands Water Resources 

Congress, 2d, Proceedings, p. 63. 

Ellins, K.K., Roman, A.R., and Lee, R.W., 1990, Using 222Rn to 

examine ground water/surface discharge interation in the Rio 

Grande de Manati, Puerto Rico: Journal of Hydrology, 115, 

p. 319-341. 

Eisinger, R. J. , and Moore, W. S. , 1983, Gas exchange in the Pee 

Dee River based on 222Rn evasion: Geophysical Research 

Letters, v. 10, no. 6, p. 443-446. 

Jacoby, G.C., Simpson, H.J., Mathieu, G., and Torgersen, T., 

1979, Analysis of ground-water and surface-water supply 

interrelationships in the Upper Colorado River basin using 

natural radon-222 as a tracer, in Report to the John Muir 

Institute, Inc.: 46 p. 

King, P.T., Michel, J., and Moore, W.S., 1982, Ground-water 

geochemistry of 228Ra, 226Ra, and 222Rn: Geochimica et 

Cosmochimica Acta, v. 46, p. 1173-1182. 

Lee, R.W., and Hollyday, E.F., 1987, Radon measurement in 

streams to determine location and magnitude of ground-water 

seepage, in Graves, B., ed., Radon, radium, and other 

radioactivity in ground water: Chelsea, Mich., Lewis Publishers, Inc., p. 241-249. 

Lowery, J.F., Counts, P.H., Edmiston, H.L., and Edwards, F.D., 

1987, Water resources data, Tennessee, water year 1986: 

U.S. Geological Survey Data Report TN-86-1, 411 p. 

Rogers, A.S., 1958, Physical behavior and geologic control of 

radon in mountain streams: U.S. Geological Survey Bulletin 

1052-E, 187 p. 
GEOLOGIC AND GEOCHEMICAL FACTORS CONTROLLING URANIUM, 

RADIUM-226, AND RADON-222 IN GROUND WATER, NEWARK BASIN, NEW JERSEY 

Zoltan Szabo and Otto S. Zapecza 

Prepared in cooperation with the New jersey Department of Environmental Protection 

Abstract 

Elevated concentrations of naturally occurring radionuclides are found in ground-water samples collected 

from the Newark basin in central New Jersey and are 

associated with uranium enrichment in the bedrock formations. Elevated radionuclide concentrations are present 

primarily in the lower part of the Passaic Formation but 

also are common in the underlying Lockatong Formation 

and, locally, in the Stockton Formation. These formations 

are exposed along the southern and eastern margins of 

the Newark basin and in the Flemington and Hopewell 

fault blocks, where the formations are stratigraphically 

repeated. Other formations in the Newark basin contain 

significantly lower concentrations of radionuclides. 

Borehole geophysical testing, analysis of lithologic 

cores, and autoradiographs were used to determine that 

the source of the natural radioactivity in the lower part of 

the Passaic Formation and the upper part of the Lockatong 

Formation is thin, laterally extensive, uranium-enriched 

black mudstones that locally contain carbonate-rich laminae. Radioactive zones are found dispersed along horizontal bedding planes throughout the matrix and in arcuate bands that crosscut bedding. Autoradiographs from 

the Stockton Formation show that the radioactive sources 

are dispersed but are not conclusive as to whether the 

source of the radioactivity is in the sandstone matrix or in 

the fracture-fill materials. 

Results of radiochemical analyses of ground-water 

samples show that gross alpha-particle activities range 

from less than 1 to 124 picocuries per liter, uranium 

concentrations range from less than 0.4 to 60 micrograms 

per liter, radium-226 concentrations range from less than 

0.6 to 22.5 picocuries per liter, radon-222 concentrations 

range from 71 to 15,900 picocuries per liter, and gross 

beta-particle activities range from less than 1 to 49.7 

picocuries per liter. 

The local ground-water chemistry determines the 

distribution of dissolved uranium and radium. Elevated 

uranium concentrations are associated with high gross 

alpha-particle activity in oxidizing ground water that is low 

in iron and manganese and commonly high in sulfate and 

bicarbonate. In contrast, elevated concentrations of 

radium-226 are associated with high gross alpha-particle 

activity in reducing ground water that is high in iron, 

manganese, and sometimes barium and low in sulfate. 

High concentrations of uranium and radium typically are 

not found concurrently in the same sample. Radon-222 

concentrations are weakly correlated with radium-226 

concentrations but not with uranium concentrations or 

the concentrations of any other dissolved chemical constituent. 

Chemical processes that may govern the distribution 

of the radionuclides in the ground water of the Newark 

basin are postulated on the basis of the chemical composition of the ground water and published laboratory 

experiments. Uranium concentrations are controlled by 

the solubility of the U +G ion and by carbonate complexing. Radium-226 concentrations are restricted by adsorption onto iron and manganese hydroxides, adsorption 

onto or ion-exchange with secondary clay minerals, and 

coprecipitation with sulfate minerals. These reactions, in 

turn, are limited by the Eh (oxidation-reduction potential) 

and the pH of the ground water. Radon-222 concentrations are governed by the abundance and distribution of 

radium-226 in the rock matrix, the emanation efficiency of 

radon-222 from the rock matrix, and the physical characteristics that determine ground-water flow in the rock. 

INTRODUCTION 

In 1984, the U.S. Geological Survey, in cooperation 

with the New Jersey Department of Environmental Protection (NJDEP), Division of Water Resources, began a study 

of naturally occurring radionuclides in ground water in the 

Newark basin, New Jersey. The principal objectives of the 

study are to ( 1) determine the occurrence and distribution of 

naturally occurring radionuclides in ground water and 

identify areas, aquifers, or parts of aquifers where elevated 

radioactivity may be expected; (2) identify nonradioactive 

constituents that might serve as indicators of radionuclides 

in ground water; and (3) define geological and geochemical 

factors that control radionuclide distribution and concentrations in ground water. The Newark basin (fig. 96) was 

chosen for this study because of previous evidence of 

uranium mineralization, known radioactive ground-water 

anomalies, locally high surficial radioactivity as mapped by 

aeroradioactivity studies, and zones of high gamma activity 

in the subsurface as recorded by borehole geophysical logs. 

Purpose and Scope 

This paper presents significant findings on the geological and geochemical factors controlling the distribution 

of naturally occurring radionuclides in ground water of the 

Newark basin, New Jersey. Two hundred and sixty groundwater samples were collected from the study area and 

analyzed for gross alpha- and beta-particle activity. Alkalinity, dissolved oxygen, Eh (oxidation-reduction potenFactors Controlling Uranium, Radium-226, and Radon-222 in Ground Water, Newark Basin, New Jersey 243 
tial), pH, specific conductance, and water temperature were 

measured on site. Selected samples also were analyzed for 

uranium, radium-226 e26Ra), radon-222 e22Rn), major 

ions, and trace metals. In conjunction with the groundwater sampling, borehole geophysics and rock coring were 

used to identify specific zones of radioactivity in subsurface 

rocks. 

Study Area 

The Newark basin in New Jersey (fig. 96) coincides 

with the Piedmont physiographic province and comprises a 

10-county area of approximately 2,000 mi2

• The basin is 

exposed at land surface in a band 16 to 32 mi wide that 

trends southwestward from the New York-New Jersey 

border to the Delaware River. On the northwest, it is 

bordered by the Border Fault, which separates it from the 

Precambrian and Paleozoic crystalline and sedimentary 

rocks of the New Jersey Highlands, also known as the 

Reading Prong. On the southeast it is bordered by the Fall 

Line, the unconformable contact with the overlying unconsolidated deposits of the Atlantic Coastal Plain. The Newark basin is a highly populated area in the northeastern 

corridor of the United States where significant quantities of 

ground-water are withdrawn from fractured-rock aquifers. 

In the New Jersey part of the Newark basin, an estimated 

143 million gallons of ground water per day is pumped, 78 

percent of which is used for public supply (U.S. Geological 

Survey, 1990). 

Geologic Setting 

The Newark basin is one of many fault-block basins 

in the Eastern United States that were formed in Triassic 

and Jurassic time during the initial rifting of the continents 

(Manspeizer and others, 1978). These basins were filled 

with thick sequences of continental sediments along with 

interbedded lava flows and intrusives. Newark basin formations are estimated to attain combined maximum thicknesses of 16,000 to 20,000 ft in New Jersey (Van Houten, 

1969). The source of sedimentation in the basin was erosion 

of Precambrian and Paleozoic highlands that surrounded the 

basin. Sediment dispersal was from all directions during 

basin filling (Abdel-Monem and Kulp, 1968)~ however, the 

principal source of sediment was the crystalline-rock highlands to the southeast (VanHouten, 1969). 

A generalized geologic map of the New Jersey part of 

the Newark basin is shown in figure 97. Progressively 

younger rocks are exposed toward the northwest because of 

the northwestward-tilting structure of the Newark basin. In 

the southwestern part of the study area, postdepositional 

faulting has caused part of the stratigraphic sequence to be 

repeated in outcrops northwest of the faults in the Hopewell 

and Flemington fault blocks (fig. 97). 

244 Field Studies of Radon in Rocks, Soils, and Water 

The three major sedimentary units in the Newark 

basin are the Stockton Formation, the Lockatong Formation, and the Passaic Formation of Olsen (1980a). In figure 

97, the Jurassic sedimentary units that are interbedded with, 

and overlie, the basalt flows in the northwestern part of the 

basin have been termed "undifferentiated rocks." The Passaic Formation and the undifferentiated rock units were 

formerly called the Brunswick Formation. 

The Triassic Stockton Formation crops out along the 

southeastern part of the study area and in the Hopewell and 

Flemington fault blocks. Its dominant lithology is gray- and 

buff-colored arkose and arkosic conglomerate, red arkosic 

sandstone, and red and gray siltstone. The Stockton Formation, which is the oldest and most widespread unit in the 

subsurface, unconformably overlies Precambrian and 

Paleozoic basement rocks. Along the southeastern edge of 

the study area, the coarse fraction of the formation was 

deposited by steep-gradient streams (Olsen, 1980b). Conglomerate and coarse sandstone generally grade into finer 

grained sandstone and siltstone toward the center of the 

basin and may represent a facies change to a marginal 

lacustrine deposit (Turner-Peterson, 1977). 

The Triassic Lockatong Formation conformably overlies and interfingers with the Stockton Formation over most 

of the Newark basin. The Lockatong Formation is composed primarily of alternating sedimentary cycles of gray, 

green, and black mudstones, siltstones, and minor carbonates that reflect the expansion and waning of an extensive 

lake, often referred to as Lockatong Lake (Van Houten, 

1969). In the northeastern end of the basin, where the unit 

is thinnest, the Lockatong Formation consists of darker 

colored mudstones that interfinger with beds of buff arkosic 

sandstone that are virtually indistinguishable from the 

sediments of the Stockton Formation (Olsen, 1980b). Wider 

fluctuations of the Lockatong Lake are noted in the upper 

part of the Lockatong Formation and continue upsection 

into the lower part of the Passaic Formation. In this part of 

the stratigraphic section, alternating deposits of nearshore 

red mudstones with offshore gray and black mudstones 

indicate extensive interfingering of both oxidizing and 

reducing environments. The interfingering of these oxidizing and reducing environments plays an important role in 

the formation of uranium-enriched zones. 

The boundary between the Passaic Formation and the 

Lockatong Formation is so gradual that it is defined both 

horizontally and vertically on the proportion of red mudstone beds to gray and black mudstone beds (Olsen, 1980b). 

The lower part of the Passaic Formation contains many 

black mudstone beds interbedded with the predominantly 

red mudstone beds. Overlying this transitional zone, the 

upper part of the Passaic Formation is composed predominantly of reddish-brown to maroon mudstone, siltstone, and 

sandstone. It is the most widespread unit cropping out in the 

basin. The depositional environment of the Passaic Forma-
PENNSYLVANIA 

c 

m 

r 

> I =E I 

I > I :IJ 

39° \ m 

\ 

I 

)-I ___ _ 

, ........... __ , 

I 

(I 

0 

I 

0 

LINE 

10 20 30 MILES 

10 20 30 KILOMETERS 

Figure 96. Location of study area (stippled), Newark basin, New Jersey. 

Factors Controlling Uranium, Radium-226, and Radon-222 in Ground Water, Newark Basin, New Jersey 245 
EXPLANATION 

JURASSIC 

~ Undifferentiated rocks 

j;jt)_' j Basalt 

j~j~ .~ Diabase 

JURASSIC AND TRIASSIC 

I JT!p j Passaic Formation 

TRIASSIC 

OOLZJ Lockatong Formation 

1:;\iii~J Stockton Formation 

A. COREHOLE 

CONTACT--Dashed where inferred 

FAULT--Dashed where inferred 

0 2 4 6 8 MILES 

I 1 11 1

1 1 1 

0 2 4 6 8 KILOMETERS 

Figure 97. Generalized geologic map of the Newark basin, New jersey, and location of coreholes. Scale 1:546,456. 

Geologic map modified from Lyttle and Epstein (1987). 

tion was originally lacustrine; subsequently, it gave way to 

broad, weakly drained mud flats and playas (Van Houten, 

1969). 

During Early Jurassic time, continued crustal extension was accompanied by emplacement of diabase intru246 Field Studies of Radon in Rocks, Soils, and Water 

sives along the eastern and southwestern part of the study 

area, and basaltic lava flows were extruded over the 

northwestern part (Manspeizer, 1980). Jurassic sedimentary 

deposits that are interbedded with and overlie the basalt 

flows record a return to cyclic lacustrine-nearshore depos-
its. Although these deposits are shown in figure 97 as being 

undifferentiated, Olsen (1980a,b) has divided these deposits 

into formal units based on lithology and biostratigraphy. 

SOURCES OF URANIUM 

The crystalline rocks that flank the Newark basin are 

rich in uranium and are the source of sediments delivered to 

the basin during Triassic and Jurassic time. According to 

Grauch (1976), the crystalline rocks adjacent to the Newark 

basin in the New Jersey Highlands Province (Reading 

Prong) and in eastern Pennsylvania form one of four 

uranium-rich provinces of crystalline rocks in the Eastern 

United States. Uranium from these source rocks was delivered along with clastic sediments to the Newark basin by 

sediment-laden streams and was redistributed by circulating 

ground water (Turner-Peterson, 1980). 

Numerous uranium-enriched zones have been 

reported in formations of the Newark basin (McKeown and 

others, 1954; Turner-Peterson, 1980; Popper and Martin, 

1982; Bell, 1983; Turner-Peterson and others, 1985). Most 

of the reported uranium-enriched zones are in outcrops of 

the Stockton and Lockatong Formations in the Flemington 

fault block. Turner-Peterson (1980) states that concentrations of 0.01 to 0.02 percent uranium oxide (reported as 

U30 8) are the usual grade for mineralized mudstones of the 

Lockatong Formation. Uranium concentrations as high as 

1.28 percent uranium oxide (reported as U30 8) have been 

measured for the Stockton Formation (Turner-Peterson, 

1977). 

Turner-Peterson (1977, 1980) has provided a 

lacustrine-humate model for uranium mineralization in the 

Newark basin for the offshore lacustrine black mudstone of 

the Lockatong Formation and the marginal lacustrine sandstone of the Stockton Formation. According to the model, 

uranium mineralization in the Lockatong Formation 

occurred during deposition. Humic matter and aqueous 

sulfide, capable of fixing uranium by reducing it from the 

u+6 to the u+4 valence state, were forming in offshore 

black muds at the time of deposition. Bacterial anaerobic 

respiration reduced sulfate from the lake water to bisulfide 

within the bottom sediments. Uranium, dissolved in river 

water entering the lake, precipitates from solution in reducing environments and therefore was fixed near the 

sediment-water interface. 

Mineralization in the sandstone beds of the Stockton 

Formation occurred shortly after deposition. Reducing 

agents (humic acids and aqueous sulfide) generated from 

the black lake-bottom muds are believed to have been 

expelled during compaction into adjacent marginal lacustrine sands. Solubilization of humic acids and aqueous 

sulfide was favored in the pore fluids of the muds because 

the environment was alkaline. Uranium-bearing ground 

water passed through the sands as it moved upward into the 

lake, and the reductants from the mud caused precipitation 

of uranium. In addition to uranium mineralization during 

deposition, or shortly thereafter, it is possible that some 

zones of uranium enrichment formed more recently along 

secondarily permeable zones during migration of intrastratal 

solutions. 

SAMPLING AND ANALYSIS 

Well Construction 

Water samples were collected by the U.S. Geological 

Survey (USGS) from 260 wells distributed throughout the 

Newark basin (fig. 98). Information about well construction 

for each site was obtained from the files of the USGS and 

the NJDEP. 

Wells finished in the rocks of the Newark basin 

usually are cased from the land surface, through the 

weathered regolith zone, into unweathered rock below. The 

remainder of the well is left uncased, commonly open to 

several hundred feet of fresh rock, so water from the 

fractures intersected by the borehole is allowed to drain 

freely into the well. Individual fracture zones within the 

same well may yield water of somewhat different chemical 

compositions (Edmunds and others, 1987). Therefore, these 

open-hole wells can be visualized as penetrating a thick 

aquifer in which water quality is vertically nonhomogeneous. Water from these wells has a gross chemistry that is 

a composite of the different water chemistries contributed to 

the well by the individual fracture zones. 

Sampling Methods 

All samples consisted of raw (untreated) water collected from a tap near the well head or at the base of a 

pressure tank or small holding tank that was drained before 

sampling. A minimum of one well-casing volume of water 

was pumped from the well, and three well-casing volumes 

of water were removed whenever possible (Claassen, 

1982). Alkalinity, dissolved oxygen, Eh, pH, specific 

conductance, and water temperature were measured on site 

according to the guidelines of Wood (1976). Dissolvedoxygen concentration and Eh were measured in water 

passing through a flow-through chamber. Stabilization of 

specific conductance, pH, and water temperature was necessary before a water sample was collected (Claassen, 

1982). Samples were filtered through a 0.45-f.Lm (micrometer) filter and preserved with nitric acid following USGS 

procedures (Thatcher and others, 1977; Fishman and Friedman, 1985). Dissolved 222Rn gas samples were collected 

into liquid-scintillation vials containing premeasured 

amounts of mineral-oil-based scintillation cocktail according to Environmental Protection Agency (EPA) approved 

methods (Environmental Protection Agency, 1978). 

Factors Controlling Uranium, Radium-226, and Radon-222 in Ground Water, Newark Basin, New Jersey 247 
EXPLANATION 

JU.RASSIC 

Q!J Undifferentiated rocks 

k jb · .J Basalt 

1.)~ ~ Diabase 

JURASSIC AND TRIASSIC 

I J ll p I Passaic Formation 

TRIASSIC 

~ Lockatong Formation 

1:·.\•fJ Stockton Formation 

WELL--Symbol indicates 

gross alpha concentration, 

.in picocuries per liter 

o Less than 8 

EB8to15 

• More than 15 

0 2 4 8 8 MILES 

I 1 '1 r' r ' ' 0 2 4 8 8 KILOMETERS 

8 i 

0 

0 

0 

0 0 0 

dB 

e 

0 0 

Figure 98. Well-sampling sites and gross alpha-particle activities in ground water from the Newark basin, New 

Jersey. Scale 1:546,456. Geologic map modified from Lytde and Epstein (1987). 

Analytical Methods 

Gross alpha-particle, gross beta-particle, and 226Ra 

activities were determined by the NJDEP Radiation Protection Laboratory, which used planchet-counting methods in a 

low-background alpha-beta counter following EPA procedures (Krieger and Whittaker, 1980). Radium-226 was 

removed from solution by coprecipitation with barium 

248 Field Studies 'of Radon in Rocks, Soils, and Water 

sulfate, and the alpha-particle activity due to the 226Ra was 

determined by a low-background alpha-beta counter 

(Krieger and Whittaker, 1980). Radon-222 activity was 

determined by liquid scintillation (Prichard and Gesell, 

1977). The radioactivity (or activity concentration) of these 

constituents of the water samples is reported in picocuries 

per liter (pCi/L), where 1 pCi represents 2.2 radioactive 

disintegrations per minute. If the radioactivity of a sample is 
so low that the measured activity cannot be clearly distinguished from normal background radiation, the activity of 

the sample is said to be below the minimum detection limit 

(MDL). The MDL for gross alpha- and beta-particle activities was 1 pCi/L and was 0.6 pCi/L for 226Ra activity. The 

measured activity of a sample was reported by the laboratory even if the activity was below the MDL. The measured 

activities reported by the laboratory are plotted, even if they 

are below the MDL, to enhance the clarity of the graphics. 

However, for the purpose of graphical representation, a 

minimum value of 0.1 pCi/L was set for all samples that had 

measured activities below this value so that logarithmic 

graphs could be made. 

Uranium concentration was determined by a contractor for the USGS National Water Quality Laboratory by the 

laser-induced phosphorescence method (Bushaw, 1983) and 

was reported in micrograms per liter (J.Lg/L). The MDL for 

uranium concentrations was 0.4 J.Lg/L. The laboratory 

reported no value for the uranium concentration if the 

uranium concentration was below the MDL. For the purpose of graphical representation, a value of 0.2 j.Lg/L was 

set for the uranium concentration for samples for which the 

uranium concentration was below the MDL. 

Concentrations of major cations, anions, and trace 

metals were determined by standard methods in the USGS 

National Water Quality Laboratory (Fishman and Friedman, 1985). Blanks, standards, and duplicate samples were 

submitted to each laboratory for each type of constituent 

analyzed so that analytical quality could be monitored 

(Thatcher and others, 1977). 

All water samples were analyzed for gross alphaparticle and gross beta-particle activity. If gross alpha 

radiation exceeded 5 pCi/L, concentrations of uranium, 226Ra, major ions, and trace metals were determined. In 

addition, concentrations of uranium and 226Ra were determined for selected samples collected from throughout the 

Newark basin to ensure representative areal coverage. 

Radon-222 concentrations were determined for selected 

samples from areas where uranium or 226Ra concentrations 

of the ground water were known to be elevated. 

Statistical Methods 

Radionuclide and inorganic chemical constituent concentrations for samples of ground water from the Newark 

basin do not fit a normal distribution; therefore, nonparametric statistical techniques were used to analyze the data. 

Descriptive statistical summaries, including the 5th, 25th, 

50th (median), 75th, and 95th percentiles were calculated 

for radionuclide and inorganic chemical constituent concentrations in the ground water. Radionuclide concentrations in 

excess of the 95th-percentile concentration value (approximately two standard deviations about the mean value) were 

considered, for the purposes of this report, to be anomalously elevated when compared to the rest of the sample 

population. An anomaly threshold that includes only the top 

5 percent of the data has been used for defining uranium 

anomalies in other regional studies (Hoffman, 1983). The 

use of the top 5 percent of the data (two standard deviations 

about the mean) as the definition of the anomaly threshold 

is a more stringent definition than the anomaly threshold of 

one standard· deviation about the mean used by Popper and 

Martin (1982) for uranium data in ground water of the 

Newark basin. 

The geographic distribution of the top 5 percent of the 

radionuclide data was used to demarcate areas in the 

Newark basin where concentrations of radionuclides in 

ground waters were considered anomalously "elevated." 

Median values for the concentrations of the radionuclides 

were considered to represent "background" concentrations. 

Chemical types of ground water in the Newark basin 

were delineated by use of a modified version of the 

classification scheme of Back (1966), based on the distribution of chemical constituents in 125 chemically analyzed 

samples. Some chemical types of ground water in the 

classification scheme of Back ( 1966) were represented by 

only one or two samples; these samples were grouped with 

other classes of similar composition, and the result was four 

broad chemical types of ground water. Median values of 

radionuclide concentrations were calculated for each of 

these broad chemical types of ground water and were 

compared by use of the nonparametric Kruskal-Wallis 

statistical test, which determines if the median values of 

ranked concentration values of populations are significantly 

different. 

The relations between concentrations of radionuclides 

and the concentration of other geochemical constituents 

were investigated by use of Spearman rank correlations, a 

nonparametric correlation technique. The magnitude of the 

correlation coefficient, r, was determined at the 95-percent 

confidence level. 

RADIONUCLIDE ACTIVITIES AND 

DISTRIBUTION IN GROUND WATER 

The range and median value of gross alpha- and gross 

b · l · · · 226R d 222R eta-partie e actiVIty, uranium, a, an n concentrations are listed in table 45. Because the concentrations of 

these radioactive constituents are skewed strongly toward 

lower values, low concentrations of these radionuclides are 

suggested to be the norm, or background, for most ground 

water in the Newark basin. 

Distribution of Gross Alpha-Particle Activity 

The gross alpha-particle activity of a sample measures the total number of alpha emissions derived from 

radionuclides in solution, including the activity of the 

isotopes of uranium, 226Ra, and other alpha-emitting 

Factors Controlling Uranium, Radium-226, and Radon-222 in Ground Water, Newark Basin, New Jersey 249 
Table 45. Range and median values of radionuclide concentrations in ground water in the Newark basin, New 

Jersey 

[ <, less than; values are reported in picocuries per liter, except for 

uranium, which is reported in micrograms per liter] 

Radionuclide No. of Maximum Minimum Median 

samples value value value 

Gross alpha particle .. 260 I24 <I 3.3 

Gross beta particle ... 260 49.7 <I 3.I 

Uranium ............ I34 60 <.4 3.I 

Radium-226 ......... I78 22.5 <.6 <.6 

Radon-222 .......... 30 I5,900 <7I I,390 

nuclides in the uranium and thorium radioactive-decay 

series. However, the activity of 222Rn is not measured, 

because it is a gas that escapes by outgassing as the sample 

is evaporated during preparation. 

The gross alpha-particle activity generally indicates 

the total amount of uranium and 226Ra present in the 

sample; this was true of ground waters in the Newark basin. 

The combined activities of uranium and 226Ra equaled, or 

nearly equaled, the gross alpha-particle activity in almost all 

samples. 

Gross alpha-particle activities ranged from less than 1 

to 124 pCi/L, with a median value of 3.3 pCi/L. Sixty-five 

percent of the ground-water samples had gross alphaparticle activities less than 5 pCi/L, and 80 percent had 

activities of less than 8 pCi/L. Thirteen percent of the 

samples had gross alpha-particle activities between 8 and 15 

pCi/L, 7 percent had activities greater than 15 pCi/L, and 5 

percent had activities greater than 19 pCi/L. 

Gross beta-particle activities ranged from less than 1 

to 49.7 pCi/L, with a median value of 3.1 pCi/L. Five 

percent of the ground-water samples had gross beta-particle 

activities greater than 11 pCi/L. Anomalously elevated 

gross beta-particle activity (greater than 11 pCi/L in this 

report) is found only in ground-water samples that also had 

anomalously elevated gross alpha-particle activity. The 

areal distribution of samples that had elevated gross betaparticle activity parallels the areal distribution of samples 

that had elevated gross alpha-particle activity. Radiochemical analyses to determine the activity of specific betaparticle-emitting radionuclides were not conducted, and 

gross beta-particle activity is not discussed further in this 

report. 

Anomalously elevated gross alpha-particle activities 

(defined in this report as greater than 19 pCi/L) were 

detected in ground waters from several of the rock formations in the Newark basin. Elevated gross alpha-particle 

activities are found predominantly in ground water along 

the south and eastern border of the study area in the lower 

part of the Passaic Formation and the upper part of the 

Lockatong Formation, and in the Hopewell and Flemington 

fault blocks, where these same geologic formations are 

repeated through faulting. Many of the elevated gross 

250 Field Studies of Radon in Rocks, Soils, and Water 

alpha-particle activities are in water from wells that are 

located very near to the mapped stratigraphic contact of the 

Passaic and Lockatong Formations. In addition, elevated 

gross alpha-particle activities are found locally in the lower 

part of the Lockatong Formation and in the Stockton 

Formation. Ground water from the upper part of the Passaic 

Formation, from the basalt units and diabase units, and 

from the area shown as Jurassic undifferentiated (fig. 98) is 

characteristically very low in gross alpha-particle activity . 

The distribution of anomalously elevated gross alphaparticle activities in ground water from predominantly the 

same stratigraphic interval basinwide suggests that conditions existed for uranium enrichment of these formations 

during a specific period of basin deposition. During early 

diagenesis, this deposited uranium was redistributed and 

became even more enriched in beds along reducing fronts in 

proximity with black organic-carbon-rich lake beds. 

Distribution of Uranium, Radium-226, and 

Radon-222 

The areas of anomalously elevated concentrations of 

uranium and 226Ra in ground water correspond to areas of 

anomalously elevated gross alpha-particle activity in ground 

water and uranium enrichment in the underlying rock. 

Therefore, anomalously elevated concentrations of gross 

alpha particles, uranium, and 226Ra in ground water of the 

study area are related spatially. However, a major conclusion of this study is that, in the Newark basin, anomalously 

elevated concentrations of both uranium and 226Ra are 

rarely found concurrently in the same ground-water sample 

(fig. 99). The lack of concurrence within a given water 

sample reflects differences in geochemical behavior 

between uranium and radium. 

Uranium concentrations ranged from less than 0.4 to 

60 f.Lg/L, with a median value of 3.1 f.Lg/L. Eleven percent 

of the ground-water samples had uranium concentrations 

greater than 10 f.Lg/L, 7 percent had concentrations greater 

than 15 J.Lg/L, and 5 percent had concentrations greater than 

21 f.Lg/L. Eighty-six percent of the samples had uranium 

concentrations greater than 0.4 f.Lg/L, the MDL. 

Radium-226 concentrations ranged from less than 0.6 

to 22.5 pCi/L, with a median value of less than the MDL of 

0.6 pCi/L; 75 percent of the ground-water samples had 226Ra concentrations less than 0.6 pCi/L. Sixteen percent of 

the samples had 226Ra concentrations greater than 1 pCi/L, 

and 5 percent had concentrations greater than 4 pCi/L. Four 

percent of the samples exceeded 5 pCi/L. 

Anomalously elevated concentrations of uranium 

(defined in this report as greater than 21 J.LgiL) and (or) 226Ra (defined in this report as greater than 4 pCi/L) are 

present predominantly in ground water from wells near or 

along the stratigraphic contact of the Passaic and Lockatong 

Formations, where gross alpha-particle activities are high. 
a: 

w 

~ 100 :::i 

a: 

w 

£L • 0 

!:!:! 10 I • a: 

::) 

0 • I I 0 • 0 

a: I • • ~ 

, 0.6 

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• 

U) 

(\1 • (\1 

I 

~ 0.1 • 2 

Q 0.05 

< 0.1 0.4 10 100 

a: 

URANIUM, IN MICROGRAMS PER LITER 

Figure 99. Scatter plot of radium-226 concentration as a 

function of uranium concentration in ground water in the 

Newark basin, New jersey. The solid vertical and horizontal lines represent the minimum detection limits for uranium and radium-226, respectively. 

Elevated activities of uranium and 226Ra also are present 

locally in other parts of the Lockatong Formation and in the 

Stockton Formation. In these areas, uranium enrichment in 

the rock has been demonstrated during the course of this 

study. In contrast, large areas of the upper parts of the 

Passaic Formation, the basalt and diabase units, and the 

area shown as undifferentiated rocks (fig. 98) have ground 

water with low gross alpha-particle uranium and 226Ra 

concentrations. 

In ground water in the lower part of the Passaic 

Formation, anomalously elevated concentrations of uranium and 226Ra are found with about equal frequency. 

However, moving up section in the Passaic Formation, 

away from the interbedded black and red beds characteristic 

of the lower part of the Passaic Formation and the upper part 

of the Lockatong Formation, the presence of anomalously 

elevated uranium concentrations becomes more frequent 

than the presence of anomalously elevated 226Ra concentrations in the ground water. Anomalously elevated uranium 

concentrations are present more often in the Stockton 

Formation, whereas, anomalously elevated 226Ra concentrations are present more often in the Lockatong Formation. 

A possible explanation for this is that ground-water chemistry is different within each of these formations, and the 

ability of 226Ra and uranium to go into solution depends 

upon the chemistry of the ground water. 

Radon-222 concentrations ranged from less than 71 to 

15,900 pCi/L, with a median value of 1,390 pCi/L. Thirteen percent of the ground-water samples had 222Rn concentrations greater than 10,000 pCi/L. Thirty-five percent 

of the ground-water samples has 222Rn concentrations 

greater than 2,000 pCi/L, and 87 percent had 222Rn concentrations greater than 200 pCi/L. Because of the relatively 

small number of 222Rn samples collected from the Newark 

basin, and because of uncertainty of the form of the 

population distribution (Kratochuil, 1985), significance was 

not attributed to the 95th percentile of 222Rn concentrations 

in ground water. This lack of strong correlation indicates 

that 222Rn concentrations in ground water are controlled by 

different factors than those controlling uranium or 226Ra. 

Concentrations of 222Rn greater than 10,000 pCi/L 

are present in all three of the formations where elevated 

gross alpha-particle activities are found (the lower part of 

the Passaic Formation, the Lockatong Formation, and the 

Stockton Formation). The highest concentrations of 222Rn 

are present in the lower part of the Passaic Formation, as are 

the highest concentrations of uranium and 22~a. However, 

samples having the highest concentrations of 222Rn do not 

necessarily coincide with samples having the highest concentrations of gross alpha particles, uranium, or 226Ra. 

Variation in 222Rn concentrations is considerable and can be 

an order of magnitude different in proximate wells. Samples 

that have the highest concentrations of 222Rn correlate better 

with the highest concentrations of 226Ra than with uranium 

(fig. 100). 

DETERMINATION OF SOURCES OF 

RADIOACTIVITY BY BOREHOLE GEOPHYSICS 

AND TEST-CORE ANALYSIS 

Borehole geophysics and rock coring were used to 

determine the subsurface source of radioactivity at specific 

sites within the Newark basin. Natural gamma-ray logging 

of wells and boreholes records the background rate of 

emission of gamma rays from the various formations that 

were penetrated as well as recording the anomalously high 

gamma activity of radioactive zones. Gamma-activity measurements vary, depending on the sensitivity of the instrument used for the measurement, changes in borehole 

diameter, and well-construction materials. Therefore, the 

data reported for gamma activity in counts per second (cps) 

are relative numbers. Gamma-spectral logging can be used 

to ascertain the presence of (and, with the appropriate 

calculations, to determine the concentration ot) uranium, 

thorium, and potassium in rock if the intensity of gamma 

emissions is measured at different energy levels. 

Background gamma levels for sedimentary rocks of 

the Newark basin measured in this study typically range 

from 100 to 160 cps. Natural gamma-ray logs of many wells 

in the upper part of the Passaic Formation and in the 

undifferentiated areas (fig. 97) show no significant gamma 

levels above background. Natural gamma-ray logs of wells 

in basalt and diabase recorded the lowest gamma counts of 

all the Newark basin units, with background gamma levels 

ranging from 20 to 40 cps. 

Factors Controlling Uranium, Radium-226, and Radon-222 in Ground Water, Newark Basin, New Jersey 251 
a: 

w !:: 50,000 

_, 

a: 

w 

a. [J • 

(/) 10,000 • • • 

!!:! 

a: 

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0 • • • •• 0 

0 13 • • • • a: 1,000 0 

~ 0 • • • 

t\i 

('I 

(\1 8 

I 

z 100 • • • ~ 

0 0 A 

c 50 <C 0.1 10 100 a: 

URANIUM, IN MICROGRAMS PER LITER 

Figure 100. Scatter plot of radon-222 concentration as a 

function of (A) uranium concentration and (B) radium-226 

concentration in ground water in the Newark basin, New 

Jersey. A vertical dashed line indicates a radium-226 concentration of 1 picocurie per liter (pCi/l), whereas a 

horizontal dashed line indicates a radon-222 concentraNumerous gamma anomalies of several thousand cps 

were recorded on well logs from the Lockatong Formation 

and the lower part of the Passaic Formation. These anomalies are associated with rock units that are characteristically 

thin (less than 1 ft thick). The anomalies are laterally 

extensive and can be traced in adjacent wells over a lateral 

distance of several thousand feet. High counts on natural 

gamma-ray logs of wells in the Stockton Formation also 

have been observed. These anomalies are also associated 

with rock units that are thin. However, these anomalies are 

more localized and cannot be traced in adjacent wells. The 

distribution of elevated activities of radionuclides in ground 

water of the Newark basin is consistent with the occurrence 

and extent of natural radioactive anomalies recorded in the 

subsurface rock formations. 

Three continuous cores were examined for this study 

(fig. 97). Two corehole sites (A and B) were located near 

the geologic contact of the Passaic and Lockatong Formations, and one site (corehole C) was located in the Stockton 

Formation. Sites A and B were cored adjacent to existing 

wells for which natural gamma-ray logging indicated several gamma anomalies ranging from 1 ,500 cps to more than 

7,000 cps. The depths of the anomalous rock zones were 

used to determine how deep to drill the coreholes. 

Continuous 2-in-diameter core was obtained to a 

depth of 68 ft in the lower part of the Passaic Formation at 

corehole site A. A natural gamma-ray log, a generalized 

lithologic description, and an interpreted environment of 

deposition are shown in figure 101. The cyclic sequence of 

252 Field Studies of Radon in Rocks, Soils, and Water 

a: 

~50,000 

:;j 

a: 

w I , 

0.10,000 

~· • (/) 

!!:! I 

I a: I • 

:l •• 

0 

0 -----------~-------------- 0 1£!JO(b I 2 1,000 I • a. ~ I 

~ 0 I 

I 

I 

N I 

N I • N 0 I • I 100 !- 0 I . z 0 I 8 0 I ,, c 50 

<C 0.05 0.1 10 50 

a: 

RADIUM-226, IN PICOCURIES PER LITER 

tion of 2,000 pCi/l. The open symbols represent uranium 

concentrations below the detection limit of 0.4 f..Lg/l, 

plotted as 0.2 f..Lg/l (A), and radium-226 concentrations 

below the detection limit of 0.6 pCi/l, plotted at the 

reported value measured below the detection limit, with a 

minimum plotting value set at 0.1 pCi/l (8). 

red, gray, and black mudstones shows the expansion and 

contraction of an extensive lake as suggested by Van 

Houten (1969). The red beds, deposited near the margin of 

the lake in a mudflat/playa environment, indicate oxidizing 

conditions prevailed at the time of their deposition. The 

progressively darker colored gray beds represent expansion 

and deepening of the lake. The black mudstones formed 

farthest offshore under anoxic conditions, and coupled with 

the presence of pyrite, are indicative of a highly reducing 

environment at the time of their deposition that is ideal for 

the precipitation of uranium. 

The natural gamma-ray log of corehole A (fig. 101) 

recorded a gamma anomaly at 42 to 43 ft below land 

surface. Gamma-spectrallogging of the zone containing the 

gamma anomaly in corehole A identified the radioactivity 

as uranium-series radionuclides (fig. 101). 

The spatial distribution of radionuclides within this 

anomalous rock zone was determined by autoradiography of 

core material. In autoradiography, radioactive emissions 

from the rock sample are allowed to strike a zinc-sulfidecoated scintillation plate. Flashes of light that are produced 

are recorded on photographic film. The zone in the rock 

containing the most radioactivity appears as the lightest 

(most developed) on the photographic film. 

Autoradiographs of vertical slices of rock core from 

the depth interval of 42 to 43 ft show abundant radionuclides finely disseminated throughout much of the interval. 

Radionuclides appear most concentrated in two thin zones 

on core pieces from depths of 42.3 to 42.4 ft and 42.6 to 
.., 

I» 

5 

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n 

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el 

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NATURAL 

GAMMA-RAY LOG 

10 

1- 20 LU 

LU 

u.. 

~ 

ui 

~ 30 

u.. 

a: 

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en 

Cl 

z 40 

::s 

106 

105 

-I 

~ 104 z 

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ffi 103 

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10 

0 

GAMMA-SPECTRAL LOG 

OF RADIOACTIVE ZONE 

200 400 600 

CHANNEL UNITS 

\"'\ . 

\~~}~~ft4:. •; 

~ ~ 50 >7,000CPS/ 

I 

1-

a.. 

LU 

Cl 

0 

"Typical background radiation 10Q-160 CPS 

(on this gamma tool) Newark basin, sedimentary formations 

INCREASING RADIATION----+ 

2,000 4,000 6,000 8,000 

COUNTS PER SECOND (CPS) 

COREHOLE A 

(location shown in fig. 97) 

FEET 

0 

--

-

--

-- 10 --

-

--

--

-- 20 --

--

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40 

LITHOLOGIC 

DESCRIPTION 

Reddish-brown mudstone/siltstone. 

Convoluted to laminar bedded. 

Locally abundant calcite. 

Burrow mottled. 

Massive gray mudstone. 

Abundant calcite scattered through matrix. 

Dark-gray to black mudstone. 

Abundant pyrite in matrix 

and in horizontal fractures. 

IIIII ...-. Black mudstone is radioactive zone. '/I II I . . 

. . .. Massive grayish-white to 

50 .. . gray mudstone/siltstone. . . . . . . Calcite scattered through matrix. 

lllLJ fj_ Alternating beds. Dark-gray LILli 

111/J/ and black mudstones. 

. . . . . ·.·: .. Massive gray to grayish-white mudstone/siltstone. 

-- Gray to dark-red mudstone/siltstone. - _ CQnvQI_ute<! bedding and b!Jrrow mottled. __ 

ENVIRONMENT 

OF DEPOSITION 

MUDFLAT/PLAYA 

NEARSHORE LACUSTRINE 

OFFSHORE LACUSTRINE 

NEARSHORE LACUSTRINE 

OFFSHORE LACUSTRINE 

NEARSHORE LACUSTRINE 

MUDFLAT/PLAYA 

Figure 101. Gamma-ray log, lithologic description, and environment of deposition of corehole A, and gamma-spectral log of radioactive zone in the 42- to 43-ft 

depth interval. 
42.8 ft. The autoradiograph of the core from a depth of 42.3 

to 42.4 ft shows elevated concentrations of radionuclides 

(light color) in association with interbedded carbonate and 

black mudstone laminae in a zone approximately 0. 5 in 

thick (fig. 102A). The autoradiograph of the core from a 

depth of 42.6 to 42.8 ft shows elevated concentrations of 

radionuclides partly in association with horizontal bedding 

planes. However, in the upper left-hand part of the autoradiograph, elevated concentrations of radionuclides crosscut 

the bedding planes (arcuate shape) and cannot be definitively associated with any lithologic feature on the hand 

specimen (fig. 102B). Within these arcuate radioactive 

anomalies, the greatest concentration of radionuclides 

appears along two thin, horizontal, wavy, carbonate-rich 

beds. 

Radiochemical analysis of ground water from the 

68-ft corehole (open interval 12 to 68 ft) shows concentrations of 66.4 pCi/L for gross alpha-particle activity, 25.2 

pCi/L for gross beta-particle activity, and 22.5 pCi/L for 226Ra. In comparison, an adjacent well that is 409-ft deep 

(open interval 30 to 409 ft) intersects the same radioactive 

zone and shows concentrations of 44.9 pCi/L for gross 

alpha-particle activity, 18.1 pCi/L for gross beta-particle 

activity, and 9.0 pCi/L for 226Ra. Uranium concentration 

was below the MDL. These radiochemical analyses indicate 

vertical changes in ground-water radioactivity at the site. 

Concentrations of radioactivity in ground water from the 

409-ft-deep well are less than those of the shallower 

corehole because radioactive water in the deeper well is 

diluted by the mixing of less radioactive water from deeper 

water-bearing zones within the well. 

At corehole B, approximately 20 mi to the southwest 

of corehole A (fig. 97), a continuous core of the upper part 

of the Lockatong Formation was collected to a depth of 187 

ft. The lithologic sequence encountered was similar to that 

of corehole A. In corehole B, two radioactive zones, each 

approximately 0.5 ft thick, were encountered. Both zones 

are black mudstones that have abundant pyrite mineralization in the matrix and locally along bedding planes. 

Although these zones are thin, they appear to have great 

lateral extent. Because these radioactive zones have been 

recorded on a natural-gamma log from another well more 

than 1,100 ft from the corehole, these zones can function as 

stratigraphic marker beds. Gamma-spectral logging of these 

radioactive zones indicates the radioactive elements present 

were uranium- and thorium-series radionuclides. 

Autoradiographs of core from these two radioactive 

zones show the radionuclides finely dispersed throughout 

the rock matrix, similar to the distribution of radionuclides 

at a depth of 42.3 to 42.4 ft in corehole A (fig. 102A). 

Arcuate bands of radionuclides crosscutting bedding were 

not observed in either radioactive zone from corehole B. 

Radionuclide activities of a ground-water sample 

from a nearby observation well, open to a depth of several 

254 Field Studies of Radon in Rocks, Soils, and Water 

hundred feet, were at the median values for the Newark 

basin (table 45). Because fracturing of the rock material was 

not observed in the proximity of the radioactive zones, it is 

possible that significant amounts of ground water do not 

come in contact with these zones or that ground water from 

other well-developed fracture zones is present in the observation well in large enough quantities to dilute any radioactivity contributed from the unfractured radioactive-rock 

zone. 

Uniform dispersion of radionuclides within black 

mudstones of the lower part of the Passaic Formation and 

the Lockatong Formation probably indicates uranium 

enrichment during, or soon after, deposition. This uniformity is consistent with syngenetic concentration of uranium 

in response to reducing conditions near the sediment-water 

interface of the lake bottom, as suggested by TurnerPeterson and others (1985). The origin of the thin, highly 

concentrated zones of radioactivity, found in association 

with horizontal carbonate-mudstone interbeds, and the 

radioactivity that crosscuts the bedding is probably due to 

secondary uranium migration and enrichment. 

At corehole C (fig. 97), continuous core of the 

Stockton Formation was collected to a depth of 120 ft 

(Lewis and Spitz, 1987). Subsequent natural gamma-ray 

logging indicated a gamma anomaly of 600 cps at a depth of 

104ft. A hand sample from the core of this radioactive zone 

is composed of fine- to medium-grained sandstone cut by 

two near-vertical fractures that are coated with a white clay 

mineral. In reference to uranium occurrences in outcrop of 

the Stockton Formation, Popper and Martin (1982) indicate 

that uraniferous sandstones have a higher clay content than 

adjacent rocks that exhibit only background levels of 

uranium. They also observe that the highest radioactivity is 

present in fracture zones or bedding contacts where high 

amounts of clay are present. 

Autoradiographs of the core from 104 ft show abundant radionuclides dispersed along the face of the fracture. 

Because the fracture face was a highly irregular surface, the 

autoradiograph was not clear enough to determine whether 

the radioactivity is associated with the fracture-fill material 

or the sandstone matrix. 

Ground water from a test well adjacent to the corehole and open to the aquifer between a depth of 90 to 110 

ft has concentrations of 30.4 pCi/L for gross alpha-particle 

activity, 15.5 pCi/L for gross beta-particle activity, and 

11.4 pCi/L for 226Ra. Uranium concentration was below the 

MDL. The abundant fracturing of the radioactive zone 

enabled ground water to come in contact with the minerals 

hosting the radionuclides in the rock strata or along the 

fracture. Dilution of radionuclide concentrations in water 

from the test well was not possible because the test well was 

only open to rock strata containing the radioactive zone. 
A 

B 

Figure 102. Rock samples (left) and autoradiographs (right) of radiation development 

(light color) from corehole A at depth intervals of (A) 42.3 to 42.4 ft and (B) 42.6 to 

42.8 ft. 

Factors Controlling Uranium, Radium-226, and Radon-222 in Ground Water, Newark Basin, New Jersey 255 
GROUND-WATER GEOCHEMISTRY OF 

URANIUM AND RADIUM IN THE NEWARK 

BASIN 

The observed distribution of uranium and 226Ra in the 

ground water is related to their different geochemical 

behavior, as predicted by thermodynamics and laboratory 

studies and verified by chemical analysis of ground-water 

samples from the field. By understanding the geochemistry 

of uranium and radium, we intend to identify other indicators of the presence of uranium and radium under given 

geochemical conditions. For this purpose, selected groundwater samples from all rock types in the Newark basin were 

analyzed chemically. (The range and median of selected 

constituents are given in table 46.) 

Water-Quality Characteristics of Ground Water 

in the Newark Basin 

Ground water in the Newark basin is primarily a 

calcium magnesium sodium bicarbonate sulfate type , 

although some calcium magnesium sodium sulfate bicarbonate, sodium bicarbonate, and calcium sodium magnesium chloride bicarbonate type of water also is present. 

Total dissolved solids range from 103 to 1,700 mg/L 

(milligrams per liter), with a median value of 260 mg/L 

(table 46). All the ground water contains abundant bicarbonate (median concentration is 163 mg/L). Calcium, 

bicarbonate, and sulfate have the greatest range of concentrations among major ions. All major cations and anions 

increase as dissolved-solids contents increase, except in 

samples of the sodium bicarbonate type ground water, 

where calcium, magnesium, and sulfate decrease as sodium 

and bicarbonate increase. Furthermore, bicarbonate concentrations decrease slightly with increasing dissolved-solids 

contents in ground-water samples of the calcium magnesium sodium sulfate bicarbonate type. However, bicarbonate, calcium, and sulfate concentrations increase most 

strongly with increasing dissolved-solids contents in 

ground-water samples. These results are generally consistent with previous findings in the Newark basin (Herpers 

and Barksdale, 1951; Longwill and Wood, 1965). 

The ground water in most cases is slightly alkaline 

and strongly oxidizing; however, some waters that are 

slightly acidic, or are reducing, are present. Values of pH 

range from 5.5 to 9.8 and have a median of 7.6 (table 46). 

Fifty percent of the pH values range from 7. 2 to 7. 8. 

Dissolved-oxygen values range from less than 0.1 mg/L to 

9.8 mg!L and have a median concentration of 2.8 mg/L. 

Approximately 30 percent of the wells sampled had 

dissolved-oxygen concentrations of less than 1 mg/L. 

Iron, strontium, and manganese have the greatest 

range of concentrations among trace metals. Iron and 

manganese concentrations increase most strongly with 

decreasing dissolved-oxygen content. Strontium concentra256 Field Studies of Radon in Rocks, Soils, and Water 

Table 46. Range and median values of selected waterquality characteristics and constituents in ground water 

from the Newark basin, New Jersey 

No. of Minimum Maximum Median samples 

pH (pH units) . .. . 

Eh (millivolts) . .. . 

Characteristic 

260 

256 

5.5 

24 

9.8 

827 

Major ions (in milligrams per liter) 

Dissolved oxygen . 248 <.1 9.8 

Bicarbonate . . . . . . 260 26 460 

Calcium . . . . . . . . . 121 2.5 360 

Sulfate . . . . . . . . . . . 121 1.6 1,100 

Total dissolved 121 103 1,700 solids ......... . . 

Trace metals (in micrograms per liter) 

Barium . . . . . . . . . . 116 <2.0 1,200 

Iron .. .. .. .. .. .. . 121 <3.0 11,000 

Manganese . . . . . . . 121 <1.0 1,600 

Strontium . . . . . . . . 116 50 11,000 

7.6 

382 

2.8 

163 

46 

40 

260 

110 

8.0 

7.0 

425 

tions increase strongly (correlation coefficient, r, = +0.63) 

and barium concentrations decrease strongly (r= -0.48) 

with increasing sulfate concentrations. 

Relation Between Concentrations of 

Radionuclides and Chemical Constituents in 

Ground Water 

Chemical and radiochemical analyses of ground 

water in the Newark basin indicate that several chemical 

constituents may serve as indicators of the presence of 

elevated concentrations of uranium or 226Ra. Anomalously 

elevated gross alpha-particle activity of the ground water 

coupled with dissolved-oxygen content, or the Eh, accurately predicts the presence of elevated uranium or 226Ra 

concentration (figs. 103 and 104). Anomalously elevated 

gross alpha-particle activity in oxi~izing waters is associated with anomalously elevated concentrations of uranium; 

however, anomalously elevated gross alpha-particle activity 

in reducing waters is associated with anomalously elevated 

concentrations of 226Ra. With few exceptions, anomalously 

elevated uranium and 226Ra concentrations were not present 

concurrently in ground-water samples (fig. 99). 

Specific chemical constituents of the ground water 

also relate to radioactivity (figs. 105-107). Although uranium concentration shows negative correlations with iron 

and manganese concentrations (r= -0.40 and -0.30, 

respectively; fig. 105A), positive correlations with strontium and sulfate concentrations are noted (r = +0.32 and 

+0.24, respectively; fig. 107A). Radium-226 shows positive correlations with concentrations of iron and manganese 

(r = +0.46 and +0.48, respectively; fig. 105B). These 

correlations are all significant at the 95-percent confidence 
a: 

w 100 

~ 

•• :J •I • a: 

~· w 

ll.. • • 

en • • • • t.- • :! • 

c( .. ·:r.:_ ·- a: 

0 

~ ~ •• • 1!1\. ~· a: .· ....... • • 

0 • ~ •• I --II-_.___ • •• ~ --- . . , ~ ~ • • 

2 0 0 

z A 

c( 

a: 0.1 

::) 0 10 

DISSOLVED OXYGEN, IN MILLIGRAMS PER LITER 

Figure 103. Scatter plots of (A) uranium concentration and 

(B) radium-226 concentration as a function of dissolvedoxygen content in ground water in the Newark basin, New 

Jersey. A vertical dashed line indicates dissolved-oxygen 

content of 1 mg/L (milligram per liter). A horizontal dashed 

line indicates uranium concentration of 1 1-Lg/L (microgram 

per liter) (A) and a radium-226 concentration of 1 pCi/L 

level when nonparametric statistics are used. In addition, 

ground water that has anomalously elevated uranium concentrations exceeds a pH of 7 (fig. 106A) and contains 

bicarbonate concentrations greater than 100 mg/L. Anomalously elevated 226Ra concentrations are present in ground 

waters where pH values are below 8 (fig. 106B). Ground 

water that has anomalously elevated 226Ra concentrations 

usually contains barium concentrations greater than 100 

J,Lg!L. Radium-226 concentrations greater than 4 pCi/L 

were not found in waters where the sulfate anion is present 

in concentrations above 100 mg/L (fig. 107B). 

Correlation between radionuclide activities and concentrations of other dissolved chemical constituents, even if 

statistically strong, does not by itself indicate cause-andeffect relations. Radionuclides and chemical constituents 

are discussed only in terms of possible geochemical reactions that may control the presence of elevated activities of 

these radionuclides in ground water of the Newark basin. 

These postulated geochemical controls on radionuclide 

activities are based upon published laboratory experiments 

and calculations using published thermodynamics constants 

(see the citations in the discussions on radionuclide chemistry that follow) and the correlations noted previously. 

The contrasting geochemical behavior of uranium and 

radium is evident in both the presence or absence of 

dissolved oxygen. Uranium concentrations above 20 J.Lg/L 

occur most often in ground water in which the dissolvedoxygen content is above 1 mg/L (fig. 103A). Conversely, in 

a: 

w 

!:: 100 

...1 

a: 

w 

ll.. 

en 

!:!:! 10 

a: 

::) • 

0 

0 

~ t· ll.. 

~ _ 

o o 

... ~ o 101 ·-·-

8 Jl COo o 

CD 

C\1 

C\1 6 :f.e 8 ~~ o 

I 0.1 

~ fD IIIB.I I~ tti.:i CIJ om:Dit:J ttw 8 ::) c 0.05 

c( 0 4 10 

a: 

DISSOLVED OXYGEN, IN MILLIGRAMS PER LITER 

(picocurie per liter) (8). The open symbols represent 

uranium concentrations below the detection limit of 0.4 

1-Lg/L, plotted as 0.2 ~J-g/L (A), and radium-226 concentrations below the detection limit of 0.6 pCi/L, plotted at the 

reported value measured below the detection limit, with a 

minimum plotting value set at 0.1 pCi/L (8). 

ground water that contains less than 1 mg/L of dissolved 

oxygen, more uranium concentrations are less than 1 J.Lg/L 

than are concentrations in ground water that contains more 

than 1 mg/L of dissolved oxygen. Radium-226 concentrations exceed 1 pCi/L predominantly in ground water that 

contains less than 1 mg/L dissolved oxygen (fig. 103B). 

The contrasting geochemical behavior of uranium and 

radium also is evident with respect to Eh (the redox 

potential) (fig. 104). Uranium concentrations increase in the 

ground water as Eh increases, whereas 226Ra concentrations 

increase in the ground water as Eh decreases. 

Uranium changes valence from the insoluble u+4 ion 

in reducing waters to the highly soluble u+6 ion in 

oxidizing waters (Langmuir, 1978). Where the amorphous 

uranium oxides contained in the rocks of the Newark basin 

(Turner-Peterson and others, 1985) come in contact with the 

typical oxygen-rich ground water, the uranium is easily 

oxidized and dissolved. Where the ground water is oxygen 

deficient, the uranium cannot be oxidized to the soluble 

valence state and does not appear in solution, even if it is 

abundantly present in the rock (as at corehole A, for 

example). 

Radium in the natural environment is present only as 

the Ra +Z ion. Because the valence state of the radium ion 

does not change, changing redox conditions (determined 

primarily, but not exclusively, by oxygen content) of the 

ground water do not directly influence the solubility of the 

radium ion. Yet, radium concentrations correlate inversely 

Factors Controlling Uranium, Radium-226, and Radon-222 in Ground Water, Newark Basin, New Jersey 257 
0: 

w 100 t- . . ::::i 

0: • ... 

w 

••• Q. 

0 

=•: :::E 10 to • < 

0: • • C!J 

0 •• • • 0: ... . . 

2 

2 1 • •• -= • •• • .. • • w:. • ~ • • ••• 2 

2 CDD DDI ODD [J 0 0 0 

z A 

< 0.1 I 

0: 0 100 200 300 400 500 600 

:J 

Eh-REDOX POTENTIAL, IN MILLIVOLTS 

Figure 104. Scatter plots of (A) uranium concentration and 

(B) radium-226 concentration as a function of Eh in the 

ground water in the Newark basin, New Jersey. The open 

symbols represent uranium concentrations below the 

detection limit of 0.4 1-1g/L (microgram per liter), plotted 

with Eh and thus suggest that a redox reaction may 

indirectly influence the solubility of the radium ion. Consequently, other chemical components of the ground water 

were investigated to determine their effect on dissolved 

radium concentrations. 

Geochemical Controls on Concentrations of 

Dissolved Uranium 

The negative correlation of uranium with iron (fig. 

105A) and manganese reflects that in reducing water, 

uranium is precipitated in the insoluble +4 valence state 

(Langmuir, 1978), whereas iron and manganese each are 

present in the soluble +2 valence state (Hem, 1985). 

Conversely, in oxidizing water, uranium goes into solution 

in the soluble +6 valence state, whereas iron and manganese, found in essentially insoluble + 3 and +4 valence 

states, respectively, form iron and manganese hydroxide 

precipitates. 

In oxidizing water, iron hydroxides are capable of 

adsorbing uranium from solution (Ames and others, 

1983b). However, uranium is strongly complexed by the 

carbonate ion in carbonate-rich, oxidizing, slightly alkaline 

waters (Langmuir, 1978). Uranium that is complexed in 

solution by carbonate is not adsorbed onto iron hydroxides 

(Hsi and Langmuir, 1985). Carbonate-rich, oxidizing, 

slightly alkaline ground waters are predominant in the 

Newark basin. We propose that uranium in solution in the 

oxidizing ground waters in the Newark basin is complexed 

258 Field Studies of Radon in Rocks, Soils, and Water 

0: 

w 100 t-

::::i 

0: 

w 

Q. • 

0 10 ... 

!:!! 

0: • • ,.. 

:J • 0 • •• • 

0 

0 • •• • . ... 

a: I :.· 41, ~ a• 

0 aa"Jaf~o tb o Do 

O~filloo C\1 

C\1 

I 0.1 ::E B 

2 0.05 

c 0 100 200 300 400 500 600 

< 

0: 

Eh-REDOX POTENTIAL, IN MILLIVOLTS 

as 0.2 1-1g/L (A), and radium-226 concentrations below the 

detection limit of 0.6 pCi/L (picocurie per liter), plotted at 

the reported value measured below the detection limit, 

with a minimum plotting value set at 0.1 pCi/L (8). 

by carbonate and, hence, is not efficiently adsorbed by iron 

hydroxides. The highest concentrations of uranium are 

found in moderately alkaline ground waters (pH values 

exceed 7, see fig. 106A) where carbonate complexing of the 

uranium ion occurs (Langmuir, 1978). 

Uranium concentrations show a positive correlation 

with strontium and sulfate concentrations in the ground 

waters of the Newark basin. Proportionately more groundwater samples that contain sulfate concentrations above 100 

mg/L also contain uranium concentrations above 3 J.LgiL 

(the median value) than do ground-water samples that 

contain sulfate concentrations below 100 mg/L (fig. 107A). 

The median uranium concentration (4.1 J.Lg/L) for ground 

water that contains more than 100 mg/L of sulfate is nearly 

double the median uranium concentration (2. 7 J.Lg/L) for 

ground water that contains less than 100 mg/L of sulfate, 

even though the highest dissolved-uranium concentrations 

are found in ground waters that contain less than 100 mg/L 

of dissolved sulfate. 

The sulfate-rich waters are mildly oxidizing and 

contain concentrations of dissolved oxygen and bicarbonate 

typical (near the medians) of ground water in the Newark 

basin. Both strontium and sulfate increase with increasing 

dissolved-solids content in the sulfate-rich waters, with the 

concentration of strontium correlating strongly with that of 

sulfate. The median concentration value of strontium in the 

sulfate-rich ground water (3.2 mg!L) is well above the 

median concentration value of strontium in ground-water 

samples from the entire data set (table 46). The correlation 

between concentrations of sulfate and strontium, a soluble 
a: 

~ 100~~~~--~~~~~~~~~~~~~~ 

:::; 

a: 

w 

a. 

en 

:1 

c( 

a: 

~ 

0 

a: 

5:2 

~ 

... 

• •• • 

10 i ~;:· I • :JJ 

•• I I 

OIID IIO aD 

• 

..... 

• I 

... . . . 

[J 0 0 IJilJI 0 

A 

~ 

~ 

2 

z 

c( a: 0.1 ...................... """"""_ ....................... __. ............... """'-_ _._. ...... ....,__._ ............... 

:::) 1 10 100 1,000 10,000 100,000 

IRON, DISSOLVED, MICROGRAMS PER LITER 

Figure 105. Scatter plot of (A) uranium concentration and 

(B) radium-226 concentration as a function of dissolvediron concentration in the ground water in the Newark 

basin, New Jersey. The open symbols represent uranium 

concentrations below the detection limit of 0.4 j.Lg/L 

a: 

w 

1- 100 

:::; 

·~··. a: 

w 

a. 

-.~-·- • --- en 

~ 10 c( 

a: •• ~ 

0 • a: 

5:2 

~ • • ! 

• • • ~ 

2 0 0 Oil D 0 0 

z A 

c( 0.1 

a: 5 7 10 :::) 

pH, IN pH UNITS 

Figure 106. Scatter plot of (A) uranium concentration and 

(B) radium-226 concentration as a function of pH in 

ground water in the Newark basin, New jersey. A vertical 

dashed line indicates a pH value of 7 (A) and 8 (B). A 

horizontal dashed line indicates uranium concentration of 

20 j.Lg/L (micrograms per liter) (A) and a radium-226 

concentration of 4 pCi/L (picocuries per liter) (B). The 

divalent cation, suggests these sulfate-rich waters have 

accumulated high amounts of dissolved mineral matter by 

a: 

w !:: 100 

..J 

a: 

w 

a. 

en 

w 

a: 

:::) 

0 

0 

0 

ii: 

~ 

CD 

C\1 

C\1 

10 

•• 

• • 

..... I ••• • I o roe [Jl o rl! 

•• 

. • • .. •• 

0 

0 

• 

•• 

• 

• 

•• 0 

0 00 

• • 

~ 0.1 ~ ~ 8 2 

c 

c( 

0.05 ...... _. ........ ~~.... .................... ~.....-.. .............. ,__ ...... __ ...w.ll''....._ ............... 1 10 100 1,000 10,000 50,000 

a: 

IRON, DISSOLVED, MICROGRAMS PER LITER 

(microgram per liter), plotted as 0.2 j.Lg/L (A), and radium226 concentrations below the detection limit of 0.6 pCi/L 

(picocurie per liter), plotted at the reported value measured below the detection limit, with a minimum plotting 

value set at 0.1 pCi/L (B). 

a: 

w 

!:: 100 

..J 

a: 

w • a. 

en 10 !:W 

a: 

:::) 

0 --- 0 

0 • 

0: 

~ • 

CD 

C\1 0 

C\1 

I 

~ 0.1 0 DO :::) 8 0 0.05 

c( 5 10 

a: 

pH, IN pH UNITS 

open symbols represent uranium concentrations below 

the detection limit of 0.4 j.Lg/L, plotted as 0.2 j.Lg/L (A), and 

radium-226 concentrations below the detection limit of 0.6 

pCi/L, plotted at the reported value measured below the 

detection limit, with a minimum plotting value set at 0.1 

pCi/L (B). 

leaching a large volume of rock or by residing a long time 

in the rock. Because these waters. are oxidizing, uranium 

Factors Controlling Uranium, Radium-226, and Radon-222 in Ground Water, Newark Basin, New Jersey 259 
a: 

w 100 

1-

:J 

a: 

w 

Q. 

UJ 

~ 10 

< 

a: 

~ 

0 

a: 

2 Is'-. ~ 

~ • .. • I ~ 

2 0 CDtDOI1DI 0 0 

z 

< 0.1 

A 

a: 

:;) 10 100 1,000 10,000 

SULFATE, IN MILLIGRAMS PER LITER 

Figure 107. Scatter plot of (A) uranium concentration and 

(B) radium-226 concentration as a function of sulfate 

concentration in ground water in the Newark basin, New 

Jersey. A vertical dashed line indicates sulfate concentration of 100 mg/L (milligrams per liter). A horizontal solid 

line indicates uranium concentration of 3 1-Lg/L (micrograms per liter) (A); a horizontal dashed line indicates 

uranium concentration of 10 f-lg/L (A), and a radium-226 

can accumulate (increase in concentration), as does the 

other dissolved mineral matter, such as sulfate, calcium, 

and strontium. In addition, both carbonate complexing of 

the uranium by the abundant dissolved bicarbonate and the 

increased competition for adsorption sites with the elevated 

amounts of dissolved calcium would inhibit uranium 

adsorption from these sulfate-rich waters and thus allow the 

accumulated uranium to stay in solution. Therefore, these 

waters often have moderately, but not anomalously, elevated uranium concentrations relative to the median uranium concentration of ground-water samples from the 

Newark basin. 

In the Newark basin, ground-water samples with 

relatively low dissolved solids contents that contain uranium concentrations above 20 !LgiL are generally found in 

areas of uranium-enriched rock strata. However, sulfaterich ground-water samples with relatively high dissolvedsolids contents that contain uranium concentrations above 3 

!Lg!L, the median uranium concentration, and occasionally 

exceed 10 !Lg!L, are generally found in areas where 

uranium-enriched rock strata are not known to be present. 

During this study, geophysical logs collected from areas in 

the Newark basin containing sulfate-rich ground waters 

have shown no anomalously radioactive rock zones. The 

implication is that uranium concentration may be relatively 

elevated in ground water in the Newark basin, even in the 

absence of uranium-enriched rock, provided that the ground 

260 Field Studies of Radon in Rocks, Soils, and Water 

a: 

w !::: 100 

_. 

a: 

w 

Q. 

UJ 10 

!!:! 

a: 

:;) 

0 

0 

0 

n: 

~ 

CD 

C\1 

C\1 

I 

~ 0.1 

:;) 0 0.05 

< 1 

a: 

10 100 1,000 10,000 

SULFATE, IN MILLIGRAMS PER LITER 

concentration of 0.6 pCi/L (picocurie per liter) (B). The 

open symbols represent uranium concentrations below 

the detection limit of 0.4 f-lg/L, plotted as 0.2 f..lg/L (A), and 

radium-226 concentrations below the detection limit of 0.6 

pCi/L, plotted at the reported value measured below the 

detection limit, with a minimum plotting value set at 0.1 

pCi/L (B). 

water has a residence time in the rock long enough to leach 

significant quantities of uranium (and other mineral matter) 

and that the uranium leached from the rock is not removed 

from solution by any geochemical process. 

Geochemical Controls on Concentrations of 

Dissolved Radium-226 

Radium-226 is present primarily in samples of the 

dilute calcium magnesium sodium bicarbonate sulfate type 

of ground waters that contain less than 1 mg/L dissolved 

oxygen and elevated concentrations of dissolved iron (as 

high as 11 mg/L). Elevated concentrations of iron and (or) 

manganese are present in almost all ground water in the 

Newark basin that has elevated 226Ra activities (fig. 105B). 

Ames and others (1983a,b) conducted laboratory 

experiments and concluded that radium was adsorbed onto 

the surface of all the secondary minerals they examined; 

however, iron hydroxide adsorbed far more radium (several 

orders of magnitude) than any of the other minerals. They 

also found that this adsorption process was most efficient in 

dilute waters that had low concentrations of divalent cations 

(like calcium) that could effectively compete with the 

radium for adsorption sites on the iron hydroxides. Komer 

and Rose (1977, p. 127) analyzed iron-hydroxide samples 

from uranium-ore-bearing sandstones in Pennsylvania and 

found 226Ra activities significantly higher than the uranium 
activity of the ore-bearing rock. This finding suggests that 

iron hydroxides incorporated 226Ra from the surrounding 

environment, presumably by an adsorption mechanism. 

Surface-adsorption mechanisms depend on the nature 

of the sorbent and sorbate, the concentration of sorbate in 

solution, the concentration of competing ions in solution, 

and the pH of the solution (Stumm and Morgan, 1981). At 

a specific pH for each sorbent, enough hydrogen ions are 

adsorbed to satisfy the negative charge of the sorbent 

surface; the affinity of positively charged ions in solution 

for the sorbent surface is thereby decreased or ended. This 

pH value is termed the "point of zero charge" (Stumm and 

Morgan, 1981). 

Anderson (1983) reported that radium is adsorbed 

most efficiently when solutions reach pH values of approximately 8 or above. The point of zero charge for iron 

hydroxides is reported to be just below this pH value 

(Stumm and Morgan, 1981). 

After reviewing this body of field and laboratory 

research and examining the data gathered in this study, we 

propose a conceptual model that relates increasing radium 

concentration in ground water of the Newark basin to 

increasing iron (and manganese) concentrations and 

decreasing Eh and pH values, as observed in this study. We 

conclude that iron (and manganese) hydroxides, which are 

abundant in the rocks of the Newark basin (TurnerPeterson, 1980), strongly adsorb radium from solution and 

thereby exert significant control on 226Ra concentration in 

the ground water. 

Radium-226 is continuously released to ground water 

contained in the pore or fracture space by several mechanisms, including the alpha-recoil mechanism detailed by 

Tanner (1964a). However, because radium is so strongly 

adsorbed by iron (and manganese) hydroxides, 226Ra 

ejected into a pore space (or fracture) would quickly be 

adsorbed onto the iron (or manganese) hydroxides coating 

fracture and grain surfaces. 

In reducing waters, iron (and manganese) hydroxide 

coatings are absent or are less abundant on mineral grains or 

along fractures. The coatings are unstable in reducing 

environments and tend to dissolve. When iron hydroxides 

dissolve, or are not present, fewer adsorption sites are 

available for radium; hence, radium concentration can 

increase in solution. Because radium-226 released to the 

ground water by alpha-recoil and other mechanisms has a 

lesser likelihood of being adsorbed onto iron (and manganese) hydroxides in reducing environments, it will have a 

greater likelihood of migrating along with the water in 

major fractures. 

An additional factor limiting radium adsorption is the 

pH of the ground water. As the pH decreases below a value 

of 8, proportionately more samples of the ground water in 

the Newark basin have higher radium concentrations. Concentrations of radium in excess of 4 pCi/L are found only in 

ground-water samples in which the pH is less than 8 (fig. 

1 06B). As the pH decreases, the point of zero charge for 

iron hydroxides is approached or reached, and radium is 

less likely to be adsorbed onto the iron hydroxides, even in 

oxidizing ground water where the iron hydroxides are 

stable. 

In summary, radium is strongly adsorbed from 

ground water in the Newark basin by iron hydroxides, 

especially above pH values of 8. As the pH decreases to a 

value below this, the efficiency with which radium is 

adsorbed decreases. Furthermore, in reducing waters, iron 

hydroxides become solubilized (or do not precipitate in the 

first place), so the number of adsorption sites available for 

dissolved radium is further reduced. 

Because the total amount of iron hydroxides in the 

rocks is relatively small compared to the abundance of other 

minerals, these hydroxides often are dismissed as unimportant. However, in fractured rocks, the fractures in the rock 

along which the water flows become coated with secondary 

minerals, including iron hydroxides. Therefore, even 

though the abundance of the iron hydroxides may be minor 

relative to other components in the bulk rock, the iron 

hydroxides are distributed in the rock in such a way (along 

the fractures) that their contact with the ground water is 

maximized. Ground-water flow in the Newark basin is 

along fractures in the rock (Herpers and Bardsdale, 1951); 

this flow pattern enables fracture-coating iron hydroxides to 

adsorb trace constituents (including 226Ra) from the ground 

water. 

Adsorption onto iron hydroxides is not the only 

control on 226Ra concentration in ground waters of the 

Newark basin. The data of Ames and others (1983a,b) 

illustrated that secondary clay minerals, and even quartz, 

can adsorb some quantities of radium. During this study, 

the collected core samples were found to contain many 

fractures coated with clay minerals; this finding indicates 

that these sorbents also are abundant in fractures in the 

rocks of the Newark basin. The point of zero charge for 

most secondary clay minerals is generally below pH values 

of 6 (Stumm and Morgan, 1981). Therefore, adsorption 

onto these secondary clay minerals may also limit 226Ra 

activities in the slightly alkaline ground water present in the 

Newark basin. 

The sodium bicarbonate type of water is found in 

some areas in the black mudstone beds in the lower part of 

the Passaic Formation and in the Lockatong Formation. 

These waters are low in divalent cations (divalent cations 

may account for less than 5 percent of the total positive 

charge). The chemistry of these waters is controlled by 

cation exchange, where divalent cations are removed from 

solution by clay minerals and are replaced by monovalent 

sodium. These waters generally have low radium concentrations (less than 1 pCi!L). The concentration of 226Ra, a 

divalent cation, also is limited in solution in these waters by 

the cation-exchange process. 

Factors Controlling Uranium, Radium-226, and Radon-222 in Ground Water, Newark Basin, New Jersey 261 
Investigators have reported that 226Ra activities 

increase with increasing dissolved-solids content in briny or 

brackish waters (Miller and Sutcliffe, 1985). However, we 

propose that 226Ra concentrations decrease when dissolved 

solids content increases in ground waters in the Newark 

basin because of the increasing sulfate concentrations associated with increasing dissolved-solids content. 

Radium-226 concentrations greater than 0.6 pCi/L 

are absent in ground water where sulfate concentration 

exceeds 100 mg/L, with the exception of one sample (fig. 

107B). Because the sulfate-rich ground water is oxidizing, 

it may be argued that the absence of detectable 226Ra is 

probably because iron hydroxides adsorb 226Ra from solution. However, the efficiency of this adsorption may be 

somewhat reduced by competition from the abundant divalent Ca+2 ion (Ames and others, 1983b). 

Radium is not abundant enough in nature to precipitate radium sulfate salts, even though radium sulfate is 

essentially insoluble (Langmuir and Riese, 1985). Saturation indices, calculated from the solubility-product constants given by Langmuir and Riese (1985), indicate that 

radium-sulfate precipitation cannot occur in ground waters 

in the Newark basin. The presence of any significant 226Ra 

concentrations in sulfate-rich water may be limited by the 

precipitation of other sulfate minerals. Langmuir and Riese 

(1985) determined that radium can coprecipitate with barium sulfate (barite) and calcium sulfate (gypsum). Both 

barite and gypsum are reported to be present in the rocks of 

the Newark basin (Herpers and Barksdale, 1951; Dombroski, 1980). Thermodynamic calculations made with the 

computer program WATEQF (Plummer and others, 1976) 

indicate that the calcium magnesium sodium sulfate bicarbonate type waters in the Newark basin are supersaturated 

with respect to barite. Barium concentrations show a strong 

inverse correlation with the concentration of both sulfate 

and strontium, and the median concentration value of 

barium in the sulfate-rich waters (57 J.Lg/L) is well below the 

median concentration value of barium in ground-water 

samples from the entire data set (table 46). Coprecipitation 

of radium with barite may be another mechanism that limits 

the activities of 226Ra in the sulfate-rich ground water. This 

constraint in sulfate-rich water explains why water samples 

containing 226Ra concentrations above 0.6 pCi/L are solely 

the reducing bicarbonate type of waters (with the exception 

of one sample). 

In summary, uranium and radium concentrations in 

ground water in the Newark basin are determined not only 

by uranium abundance in the rock material but also by 

geochemical processes involving these elements. Uranium 

concentrations are controlled by ( 1) the solubility of the 

U+6 ion and (2) carbonate complexing and the lack of 

adsorption due to carbonate complexing. Radium-226 concentrations in the ground water of the Newark basin are 

constrained by the simultaneous occurrence of at least three 

important geochemical processes, which are adsorption 

262 Field Studies of Radon in Rocks, Soils, and Water 

onto iron and manganese hydroxides, ion exchange onto 

clay minerals, and precipitation as alkaline-earth sulfate 

minerals. All these reactions, in turn, may be limited by the 

pH and Eh of the ground water. 

Relations Among Ground-Water Chemistry, 

Lithology, and Radionuclide Activities 

The geographic distribution of uranium and 226Ra in 

ground water depends upon the outcrop pattern of the 

different formations in the Newark basin, because the 

chemical characteristics (pH and Eh) and constituents differ 

somewhat from formation to formation. Ground water in 

the red siltstone of the Passaic Formation and the arkose of 

the Stockton Formation is generally oxidizing, whereas in 

the black organic mudstones of the lower part of the Passaic 

Formation and the Lockatong Formation it is generally 

reducing. Where the underlying rock is uranium rich, 

uranium is present in oxidizing waters (mostly the Passaic 

and Stockton Formations), and 226Ra is present in reducing 

waters (mostly the lower part of the Passaic Formation and 

Lockatong Formation). 

CONTROLS ON DISSOLVED RADON-222 

CONCENTRATION IN THE NEWARK BASIN 

Radon-222 concentration in the ground water is 

highly variable and is two to three orders of magnitude 

greater than the corresponding uranium and 226Ra concentration (fig. 100). This finding is consistent with the 

conclusions of Tanner (1964b) that the dissolved 222Rn 

concentration is too high to be derived from dissolved 226Ra 

and must be derived from alpha-recoil (Tanner, 1964a,b) of 222Rn from 226Ra decay in the rock matrix. Because the 

half-life of 222Rn is relatively short (3.82 days), it cannot 

migrate far from its source rock. Therefore, the dissolved 222Rn concentration of a water sample from a well is likely 

to be proportional to the radioactivity in the rock around the 

well borehole, and not necessarily to the concentration of 

radionuclides in solution. 

Radon-222 concentration in the ground water does 

not correlate with concentrations of dissolved uranium (fig. 

100A), but 222Rn concentration does correlate with the 

concentrations of dissolved 226Ra (fig. 100B). In general, 

ground-water samples from the Newark basin that contained 

concentrations of 226Ra greater than 1 pCi/L also contained 222Rn concentrations greater than 2,000 pCi/L (fig. 100B), 

whereas all samples that contained concentrations of 226Ra 

less than the detection limit of 0.6 pCi/L also contained 222Rn concentrations less than 2,000 pCi/L. However, 

several wells containing abundant 226Ra concentrations 

contain dissolved 222Rn concentrations below the median 

value. 
Uranium concentrations do not correlate with 222Rn 

concentrations in ground water of the Newark basin, 

because uranium concentrations in the ground water are 

controlled by chemical reactions, and because uranium can 

migrate far from its source bed, as it has a long half-life. 

Radium-226 concentrations correlate with 222Rn concentrations in ground water of the Newark basin, while 

uranium concentrations do not, because in the reducing 

waters of the uranium-rich black mudstones in the Newark 

b . 226R . . asm, a can go mto solutiOn to some degree as can 

222Rn. In addition, 226Ra has a much shorter half-life than 

uranium and, therefore, cannot migrate as far from its 

source bed as can uranium. However, the half-life of 226Ra 

is still much longer than that of 222Rn, so 226Ra may migrate 

at least some distance from its source bed and not represent 

radioactivity in the rock around the well borehole. This 

ability to migrate may cause the abundant scatter on the 

scatter plot of 222Rn and 226Ra (fig. 100B). Additional 

scatter may be caused by the fact that 226Ra does not go into 

solution in the oxidizing ground water of the Newark basin. 

Dissolved 222Rn concentration does not correlate with 

the concentration of any chemical constituent in the ground 

water in the Newark basin. This is not surprising in light of 

the fact that 222Rn is an inert gas that is not chemically 

reactive. In the Newark basin, many uranium-enriched rock 

zones are found in black mudstones containing reducing 

ground water; this environment prohibits uranium from 

going into solution while allowing the chemically inert 

222R . l . n to go mto so utwn. Therefore, the concentration of 

dissolved uranium in reducing environments does not represent the radioactivity in the rock around the well borehole. 

Conversely, in oxidizing ground water in the Newark basin 

(particularly in the sulfate-rich water), uranium is soluble, 

can migrate far from its source bed, and, therefore, may not 

represent the radioactivity in the rock around the well 

borehole. 

Radon-222 concentrations in ground water in 

fractured-rock terrain are reported to be controlled by 226Ra 

content of the local bedrock and by several physical 

characteristics, not by geochemical reactions involving 

radon. These characteristics include pumping rate, hydrodynamic dispersion, fracture length (Chen and Wilson, 

1987), fracture width, and the 226Ra content and radon 

emanation coefficient of the material in the radiumcontaining aquifer (Korner and Rose, 1977). These characteristics have not yet been evaluated in the fractured rocks 

of the Newark basin. 

Applications to Indoor Airborne Radon 

One of the most important factors in identifying areas 

of elevated activities of indoor airborne 222Rn is locating 

areas of rock (soil) material containing anomalously high 

concentrations of uranium or 226Ra (Otten, 1987). This 

study of the Newark basin has shown that areas of the 

Newark basin that have elevated radioactivity in ground 

water are areas that generally have underlying rock units 

enriched in uranium. In the lower part of the Passaic 

Formation, and in the Lockatong and Stockton Formations, 

anomalous activities of radionuclides are present in ground 

water, and anomalous amounts of radioactivity usually are 

found in the rock material intercepted by wells. Therefore, 

the outcrop areas of these formations may be areas that 

have the potential for indoor airborne 222Rn contamination. 

Measurements of radioactivity in ground water and in the 

adjoing rock units in the Newark basin may prove valuable 

in the study of the distribution of indoor airborne 222Rn 

concentrations (Thomas, 1987). 

CONCLUSIONS 

Elevated concentrations of naturally occurring radionuclides in ground water are associated with uranium 

enrichment in the rocks of the Newark basin in New Jersey. 

Elevated gross alpha-particle activities are found primarily 

in ground water along the southeastern border of the study 

area, in the upper part of the Lockatong Formation and 

lower part of the Passaic Formation of Olsen (1980a), and 

in the Hopewell and Flemington fault blocks, where these 

formations are repeated. Many wells located near the 

mapped stratigraphic contact of these formations had elevated alpha-particle activities. 

The source of radioactivity was determined by borehole geophysical testing, analysis of lithologic cores, and 

autoradiography. Thin, laterally extensive, uraniumenriched black mudstones within the Lockatong Formation 

and lower part of the Passaic Formation are the primary 

source of natural radioactivity in ground water in the study 

area. 

Elevated radionuclide activities in ground water also 

are found locally in wells open to uranium-enriched zones 

of arkosic sandstone of the Stockton Formation and in the 

Lockatong and lower part of the Passaic Formation in the 

northeastern part of the basin. Ground water from the upper 

part of the Passaic Formation, basalt and diabase units, and 

the undifferentiated sedimentary units interbedded with and 

overlying the basalt flows is predominantly low in radionuclides. 

The distribution of 226Ra and uranium concentrations 

in ground water of the Newark basin is controlled not only 

by uranium abundance in the rock but also by ground-water 

geochemistry. Elevated concentrations of uranium and 

226Ra generally are not found concurrently in the same 

ground water. Elevated concentrations of uranium are 

present in ground water that exhibits high gross alphaparticle activity and that is oxidizing, low in iron and 

manganese, and often high in sulfate and bicarbonate. In 

contrast, elevated concentrations of 226Ra occur in ground 

Factors Controlling Uranium, Radium-226, and Radon-222 in Ground Water, Newark Basin, New Jersey 263 
water that has high gross alpha-particle activity and that is 

reducing, contains elevated concentrations of iron, manganese, and, locally, barium, and low concentrations of 

sulfate. 

Uranium concentrations in ground water in the Newark basin are determined by two geochemical processes, the 

solubility of the u+6 ion and carbonate complexing. 

Radium-226 concentrations are determined by three important geochemical processes: ( 1) adsorption onto iron and 

manganese hydroxides, (2) adsorption and (or) ion 

exchange onto clay minerals, and (3) coprecipitation with 

alkaline-earth sulfate minerals. All these reactions are, in 

turn, governed by the pH and Eh of the ground water. The 

dissolved concentration of 222Rn, an inert gas, is not 

constrained by the geochemical composition of the ground 

water. Radon-222 concentrations in ground water are limited by the 226Ra content and the radon-emanation coefficient of the rock matrix, and by physical characteristics of 

the aquifers, such as ground-water flow conditions, and the 

length and width of the fractures in the rock. 

ACKNOWLEDGMENTS 

The authors are grateful to personnel at the New 

Jersey Department of Environmental Protection, Bureau of 

Environmental Laboratories, for their timely analytical 

work throughout the study. We especially wish to thank 

Patricia Gardener for coordinating the cooperative effort 

and Nicholas Tummillo for providing quality-assurance and 

analytical-methods documentation and field supplies. We 

also are very grateful to Christy Bell of the New Jersey 

Geological Survey for preparing autoradiographs from core 

samples. Geophysical logging was done by the USGS 

Borehole Geophysics Research Group. 

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Factors Controlling Uranium, Radium-226, and Radon-222 in Ground Water, Newark Basin, New Jersey 265 

RADIUM-226, RADIUM-228, AND RADON-222 IN GROUND WATER OF THE 

CHICKIES QUARTZITE, SOUTHEASTERN PENNSYLVANIA 

L. DeWayne Cecil, Lisa A. Senior, and Karen L. Vogel 

Abstract 

The Chickies Quartzite, a Cambrian quartzite, slate, 

and conglomerate, typically forms ridges and borders 

uplands on a 112-square-mile area of the Piedmont physiographic province of southeastern Pennsylvania. The 

Chickies is a minor water-table aquifer recharged primarily by precipitation. 

Radium-226 concentrations for ground water from 

107 wells range from less than 0.1 to 31 picocuries per liter, 

and radium-228 concentrations range from less than 0.5 to 

100 picocuries per liter. Fifty-one of the 107 analyses 

exceeded the Environmental Protection Agency maximum 

, contaminant level for radium of 5 picocuries per liter and 

had radium-228 concentrations in excess of those for 

radium-226. Elevated radium concentrations in ground 

water are distributed throughout the Chickies Quartzite. 

The range of radium-228/radium-226 activity ratios for 70 

analyses is 0.7 to 30, and the median is 2.7. Radon-222 

concentrations range from 86 to 24,500 picocuries per 

liter. 

Total dissolved-solids concentration of the ground 

water is low (as low as 7 milligrams per liter), and pH is 

acidic (as low as 4.3). The ground waters are slightly 

reducing with respect to iron and manganese and contain 

detectable dissolved concentrations of these constituents. 

Nonparametric Spearman rank correlation was used 

to determine the relation between concentrations of radionuclides, other chemical constituents, and well construction characteristics. Total radium (sum of dissolved 

radium-226 and dissolved radium-228) relations that were 

found to be significant at the 95-percent confidence level 

are a negative correlation with pH and a positive correlation with dissolved organic carbon, barium, and manganese. Total radium concentrations also showed a slight 

negative correlation with well yield and a slight positive 

correlation with specific conductance, sodium, chloride, 

and sulfate. Radon-222 relations found to be significant 

are slightly negative correlations with sulfate, magnesium, 

total dissolved solids, and specific conductance. 

Low pH may be used as a predictor of elevated 

radium concentrations in ground waters of the Chickies 

Quartzite. At pH below 4.7, all samples of ground water 

contained concentrations of total radium that exceeded 

the Environmental Protection Agency maximum contaminant level of 5 picocuries per liter. 

Possible controls on radium in solution in ground 

water of the Chickies Quartzite are adsorption and complexation. The low pH of the ground water decreases the 

ability of quartz and kaolinite in the aquifer matrix to serve 

as adsorption sites for radium. The dissolution of iron and 

manganese oxyhydroxides, possible adsorption sites, 

decreases the number of available adsorption sites and 

may release the radium into solution. Also, complexation 

with dissolved organic carbon may increase radium mobility. 

Lack of correlation between concentrations of 

radon-222 and its parent, radium-226, suggests that radon222 is not supported by radium-226 in solution. Concentrations of radon-222 in solution differ locally. 

INTRODUCTION 

The Chickies Quartzite is a Cambrian quartzite, slate, 

and conglomerate that crops out in the Piedmont physiographic province of southeastern Pennsylvania, generally 

forming narrow ridges (fig. 108). The Chickies Quartzite 

occurs in parts of Adams, Berks, Bucks, Chester, Lan.:. 

caster, Montgomery, and York Counties. Although the 

Chickies is a minor aquifer, it is the only source of water for 

thousands of people served by private wells. 

In 1985, routine sampling by the Pennsylvania 

Department of Environmental Resources (PaDER) at three 

trailer parks that derive their water supply from the Chickies 

Quartzite showed gross alpha-particle radioactivity, excluding uranium and radon, above the Environmental Protection 

Agency (EPA) 15 pCi/L (picocuries per liter) maximum 

contaminant level (MCL) (EPA, 1986). Subsequent sampling in 1985 showed total radium concentrations (sum of 

dissolved radium-226 and radium-228) that exceeded the 

MCL of 5 pCi/L for radium. 

A study of the occurrence and distribution of radium 

and radon in ground water of the Chickies Quartzite in 

southeastern Pennsylvania was conducted by the U.S. 

Geological Survey in cooperation with the PaDER Bureau 

of Topographic and Geologic Survey and the PaDER 

Bureau of Radiation Protection from October 1986 through 

December 1987. An understanding of the conditions and 

processes that favor the dissolution and retention of radium 

and radon in solution may help predict concentrations in the 

Chickies Quartzite and similar geologic units. 

Purpose and Scope 

This paper identifies the extent and magnitude of 

radium and radon concentrations in ground water in the 

Chickies Quartzite in southeastern Pennsylvania and briefly 

characterizes the geochemical environment associated with 

elevated radium and radon concentrations. Inductive statistics are used to determine correlations between radionuclide 

concentrations, other chemical constituents, and well con .. 

struction characteristics. 

Radium-226, Radium-228, and Radon-222 in Ground Water of the Chickies Quartzite 267 
I 5 11 15 HILES 

I I·. 1

1 I 

MARYLAND 

N EXPLANATION 

I 5 11 15 XI LCHITIJI8 

1 J AJIDII UltDEIU.AI" JH 

QQCIJES IIUAITZITB 

Figure 108. location of the Chickies Quartzite in southeastern Pennsylvania. Base by the Pennsylvania Geological Survey. 

Phase one of the sampling program, a reconnaissance 

to determine the extent and magnitude of radium and radon 

concentrations, was conducted between October 1986 and 

January 1987. The sampling program was based on available data and adjusted as new data became available. 

Fifty-one water samples were collected to supplement 

available radionuclide and chemical data and provide 

evenly distributed areal coverage in the six counties where 

the Chickies occurs. Data collection was concentrated in 

Chester, Lancaster, and York Counties; a few sites were 

sampled in Berks, Bucks, and Montgomery Counties. 

During phase two of the sampling program (March to 

October 1987), an additional 56 samples were collected for 

chemical analyses. Sampling sites were distributed throughout the Chickies, but sampling was concentrated in several 

smaller areas to characterize the geochemical and hydrologic conditions indicative of elevated radium and radon 

concentrations. 

Acknowledgments 

The authors are indebted to the many individuals who 

provided assistance and information essential for the successful completion of this study. Special thanks are given to 

Robert C. Smith II of the PaDER Bureau of Topographic 

and Geologic Survey, Margaret A. Reilly of the PaDER 

Bureau of Radiation Protection, and Arthur W. Rose of the 

Pennsylvania State University for their many suggestions 

268 Field Studies of Radon in Rocks, Soils, and Water 

for this paper. Sincere thanks are given to Michael Webb of 

the PaDER Bureau of Laboratories for his assistance in 

quality-assurance analyses. The authors gratefully acknowledge the cooperation of the many individuals who kindly 

permitted access to their wells for the collection of data 

essential to this study. 

GEOHYDROLOGIC SETTING 

Geology 

The Chickies Quartzite is Early Cambrian in age and 

lies unconformably on Precambrian deformed and metamorphosed crystalline rocks. The Lower Cambrian Antietam Quartzite and underlying Harpers Phyllite-undivided 

quartzite, quartz schist, and phyllite units-lie conformably 

above the Chickies Quartzite. The Chickies Quartzite has 

three mapped members: the upper quartzite, upper slate, 

and lower Hellam Member, a conglomerate. The upper 

slate member has been mapped in York County (Stose and 

Stose, 1944), and both other members have been mapped in 

all counties underlain by the formation. Overall thickness of 

the Chickies Quartzite is reported to range from 430 to 

1 ,300 ft (feet) (Lyttle and Epstein, 1987); the Hellam 

Member ranges from 200 to 500 ft in thickness (Bascom 

and Stose, 1938; Stose and Jonas, 1939; Willard and others, 

1959). Thickness of the upper slate member is estimated to 
be 350 ft (Stose and Stose, 1944). The Chickies Quartzite 

has been folded and faulted repeatedly and, where exposed, 

forms narrow ridges that trend generally east-northeast. The 

formation is highly resistant to weathering. 

The quartzite is light gray to white, vitreous to 

granular, and massive to thin bedded, with sericitic quartz 

schist (Bascom and Stose, 1938). In general, the quartzite is 

very clean, with small amounts of feldspar, has undergone 

some recrystallization, and may contain nondetrital tourmaline (commonly stretched) and mica. Other minerals present 

as accessories include zircon, rutile, apatite, monazite, 

limonite after pyrite, hematite, magnetite, and unidentified 

opaque minerals (Bascom, 1905; Bascom and Stose, 1938; 

Dryden and Dryden, 1964; Berkheiser, 1985). Thin, discontinuous beds of "white siliceous clay" or kaolinite in the 

quartzite have been interpreted as weathered mica-rich 

feldspars layers (Bascom and Stose, 1938). The iron content of the quartzite is reported to increase to the west from 

Lancaster County (Berkheiser, 1985). The basal Hellam 

Member is a coarse feldspar and quartz-pebble conglomerate that grades into conglomeratic quartzite having a quartz 

and sericitic matrix and accessory zircon, magnetite, and 

hematite (Knopf and Jonas, 1929; Bascom and Stose, 

1938). Quartz pebbles in the conglomerate are commonly 

blue. Interbeds of slate are reported to occur in both 

members. The upper slate member is interbedded slate, 

phyllite, and quartzite; the member contains quartz, albite, 

chlorite, muscovite, magnetite, zircon, and tourmaline 

(Stose and Stose, 1944). 

Because zircon, monazite, and apatite are known to 

contain minor amounts of uranium and thorium, these 

minerals are possible sources of radionuclides within the 

formation. Generally, zircon may contain up to 13.1 percent thorium and 2. 7 percent uranium, monazite may 

contain up to 26.5 percent thorium and up to 0.1 percent 

uranium, and apatite may contain up to 3 percent thorium 

and 0.02 percent uranium (Fronde! and others, 1967; 

Durrance, 1986). Detrital zircons from the Devonian 

Catskill Formation in east-central Pennsylvania are reported 

to contain up to about 0.17 percent thorium and 1. 2 percent 

uranium (Tole, 1979). 

Goodwin and Anderson (1974) described the environment of deposition of the quartzite as a mosaic of 

subtidal channels, intertidal flats, and tidal flat ponds. They 

base this interpretation on identifiable physical and biogenic 

structures within the formation, such as stratification, bed 

form, grain size, and fossil burrow forms of Scolithus and 

Monicraterion. 

Aquifer Characteristics 

The Chickies Quartzite is a water-table aquifer. 

Springs and artesian conditions occur locally on slopes. 

Recharge to the aquifer is predominately by local precipitation. Soil cover is thin (1 to 5 ft), and depth to consolidated bedrock commonly is 10 ft or less, although some 

weathered zones may extend deeper. Beds dip steeply in 

places. Openings to the surface have. developed along 

bedding, jointing, and structurally controlled planes such as 

cleavage, faults, and fractures caused by folding. This 

secondary porosity is estimated to be very slight to moderate (McGlade and others, 1972; Wilshusen, 1979). In very 

well cemented sandstones and recrystallized quartzites, 

porosities may be less than 1 percent (Freeze and Cherry, 

1979). 

Well Yield, Well Depth, and Specific Capacity 

Reported yields for 167 domestic ·wells ranged from 

0.5 to 73 gal/min (gallons per minute); the median yield was 

9.0 gal/min. Reported yields for 37 nondomestic wells 

ranged from 3 to 125 gal/min; the median yield was 23.5 

gal/min. Some of the difference between the median yield 

for domestic and nondomestic wells may be attributable to 

the generally larger (greater than 6 in (inches)) diameter of 

nondomestic wells. Also, nondomestic wells are drilled for 

the largest yield obtainable and are generally deeper than 

domestic wells. Well depths for 196 domestic wells ranged 

from 16 to 500 ft; the median depth was 140 ft. Well depths 

for 48 nondomestic wells ranged from 42 to 600 ft; the 

median depth was 155 ft. 

Specific capacities of 76 domestic wells ranged from 

less than 0.01 to 5.0 (gal/min)/ft (gallons per minute per 

foot of drawdown); the median was 0.2 (gal/min)/ft. Specific capacities are less than 1.0 (gallmin)/ft for 87 percent 

of the domestic wells. Specific capacities for 21 nondomestic wells ranged from 0.2 to 3.0 (gallmin)/ft, and the 

median was 0.25 (gal/min)/ft. Specific capacities are less 

than 1.0 (gal/min)/ft in 81 percent of the nondomestic wells. 

DATA COLLECTION AND ANALYSIS 

Data for this study consist of chemical analyses of 

ground-water samples and physical characteristics of the 

wells. A total of 107 wells completed in the Chickies 

Quartzite was sampled from November 1986 through October 1987. Several wells were sampled more than once, but 

only the results of the initial sampling are reported and 

included in data analysis. Temperature, pH, alkalinity, 

specific conductance, and dissolved oxygen of groundwater samples were measured in the field at each sampling 

site. Water samples were analyzed in the laboratory for 

dissolved radionuclides, inorganic constituents, and dissolved organic carbon. Information about well construction 

and characteristics was obtained from driller records, if 

available, from owners, and from the U.S. Geological 

Survey data base. 

Radium-226, Radium-228, and Radon-222 in Ground Water of the Chickies Quartzite 269 
Sampling Sites 

Of the 107 sampling sites, 101 were domestic wells 

and 6 were nondomestic wells. Generally, these wells were 

drilled by the air-rotary or air-hammer method, cased with 

steel or plastic casing set 20 to 40 ft into bedrock, and 

finished as open holes. Depth to consolidated rock from 

land surface is usually less than 30 ft. Most domestic wells 

have a 6-in diameter and are equipped with submersible 

pumps. The nondomestic wells range in diameter from 6 to 

8 in. Driller records indicate that more than one fracture or 

water-bearing zone contributes water to some of the wells. 

Information from driller logs, geologic maps, and 

field water chemistry was used to ensure that sampled wells 

were completed in the Chickies Quartzite. However, it is 

possible that some wells near contacts penetrate other 

formations. 

Sample Collection 

Wells were pumped until water temperature stabilized 

(about 30 to 60 minutes). Water samples were collected as 

close to the well head as possible, ahead of filters or 

treatment equipment. Water for analysis of dissolved radionuclides and inorganic constituents was filtered through a 

0.45-J.Lm (micrometer) filter by use of a peristaltic pump. 

The radiochemical samples were preserved in the field by 

treatment with concentrated hydrochloric or nitric acid. For 

radon- 222 e22Rn) analysis by liquid scintillation, two 

10-mL (milliliter) aliquots per sample site were collected by 

the method outlined by the EPA (1978). 

Field Analysis 

Field measurements of pH, temperature, specific 

conductance, alkalinity, and dissolved oxygen were 

obtained by use of methods described by Wood ( 1981). 

Total alkalinity is assumed to be the sum of bicarbonate and 

carbonate, and samples were titrated to pH 4.5. If the pH of 

a water sample was below 4.5, alkalinity is reported as 0.0 

mg/L (milligrams per liter) as CaC03 . The presence of 

organic acids or other titratable anions not identified in the 

sample may interfere with the alkalinity titration by lowering the endpoint. Other errors in determination of alkalinity 

may be caused by inaccurate pH measurements of the 

sample. 

Dissolved oxygen was measured by the azide modification of the Winkler method (American Public Health 

Association and Water Pollution Control Federation, 1985). 

Reported values for dissolved oxygen may be elevated and 

may not reflect actual ground-water concentrations because 

oxygenation may have occurred during pumping or sampling. Possible interference by ferrous iron (greater than 

270 Field Studies of Radon in Rocks, Soils, and Water 

1,000 J.Lg/L (micrograms per liter)) would cause a low value 

for dissolved oxygen that had been determined by the azide 

modification of the Winkler method. Dissolved-oxygen 

measurements were made at 37 sites sampled during the 

first phase of the project. Both a membrane polarographic 

cell probe and the Winkler method were used. Air was used 

to calibrate the membrane polarographic cell probe. Comparison of the two methods shows that the Winkler method 

generally measured greater values for dissolved oxygen (the 

range of difference for the Winkler and membrane methods 

combined is -1.2 to +3.6 mg/L, the median is +0.6 mg/L, 

and the mean is +0.8 mg/L). Dissolved-oxygen measurements from independent work in 1985 (Cecil and others, 

1987) confirm that the values for dissolved oxygen in 

ground water of the Chickies Quartzite are elevated. 

Eh was measured during phase one sampling as a 

semiquantitative indicator of redox potential. For 48 sites, 

Eh ranged from +210 mv (millivolts) to +660 mv, and the 

median was +430 mv. Given the observed range of pH, the 

Eh measurements, which agree with previous work from 

1985 (Cecil and others, 1987), indicate that the ground 

water is slightly reducing for iron and manganese. Dissolved ferrous and total iron were field determined at a few 

sites during phase two by use of a spectrophotometric 

method (American Public Health Association and Water 

Pollution Control Federation, 1985). The field determinations indicate that the ferrous form is predominant; this 

determination is consistent with observed Eh and pH 

values. 

Generally, ground water from the Chickies Quartzite 

is acidic, exhibits low alkalinity and specific conductance, 

and apparently has elevated concentrations of dissolved 

oxygen. Median and ranges of field values are presented in 

table 4 7. The highest value of pH (7. 3) and second highest 

specific conductance (626 J.LS/cm (microsiemens per centimeter at 25 °C)) are for a water sample from a well that 

probably penetrates the Ledger Dolomite and represents 

mixed waters. 

Radionuclides 

Analysis of water samples for radionuclides was 

contracted to private laboratories. Concentrations of dissolved radium-226 e26Ra), radium-228 e28Ra), total uranium, and gross alpha- and beta-particle radioactivities 

were measured by Teledyne Isotopes, Westwood, N.J. 

Concentrations of 226Ra were determined by radon emanation, 228Ra by coprecipitation with barium sulfate, and 

beta-gamma counting and total uranium by laser fluorometry. Lower limits of detection for analytical methods are 

reported as less-than (<)values and differ with background 

count of the laboratory at the time of analysis. All values 

less than the lower limit of detection were set equal to the 

same rank for use in nonparametric statistical analysis 
Table 47. Field measurements of temperature, pH, specific conductance, alkalinity, and dissolved oxygen for ground 

water from the Chickies Quartzite 

[°C, degrees Celsius; f.l.S/cm, microsiemens per centimeter at 25 °C; mg/L, milligrams per liter] 

Physical property 

or constituent 

Temperature (°C) .................................... . 

pH (pH units) ....................................... . 

Specific conductance (J.LS/cm) ........................ . 

Alkalinity (mg/L as CaC03) .......................... . 

Dissolved oxygen (mg/L) ............................. . 

Number of 

measurements 

107 

107 

107 

95 

102 

Range 

Minimum Maximum 

9 

4.3 

115 

.0 

.0 

15 

7.3 

663 

296 

12.1 

Median 

12.0 

5.3 

137 

22.4 

6.7 

Table 48. Laboratory determinations for dissolved concentrations of radium-226, radium-228, total uranium, and 

radon-222, and gross alpha-particle and gross beta-particle radioactivity 

[pCi/L, picocuries per liter; J..l.g/L, micrograms per liter] 

Constituent Number 

of samples 

Number of samples 

below 

detection limits 

Range 

Minimum Maximum Median 

Radium-226 (pCi/L) .................................. . 

Radium-228 (pCi/L) .................................. . 

Uranium, total (J,Lg!L) ................................ . 

Radon-222 (pCi/L) ................................... . 

Gross alpha-particle radioactivity (pCi/L) ............... . 

Gross beta-particle radioactivity (pCi/L as cesium-137) .. . 

107 

107 

107 

103 

107 

107 

19 

31 

29 

0 

29 

1 

<0.1 

<.5 

<.05 

86 

<.7 

<1.0 

31±2 1.0±0.4 

100±10 2.7±.5 

6.6±1.0 .2±.03 

24,500 2,000 

55±6 3.5± 1.1 

210±10 6.7±1.0 

Table 49. Distribution by county of total radium and radon-222 in samples of ground water in the Chickies Quartzite 

[pCi/L, picocuries per liter] 

Total radium1 (pCi/L) Radon-222 (pCi/L} 

Number Number (percent) Range Number of Range 

County of samples exceeding 5 pCi/L Minimum 

Berks .......... 1 0 (0) 3.2±0.7 

Bucks ......... 5 2 (40) <.8 

Chester ........ 57 34 (60) <.6 

Lancaster ...... 18 10 (56) <.8 

Montgomery ... 4 0 (0) <1.0 

York .......... 22 5 (23) <.7 

Total. ...... 107 51 (48) <.8 

1

Sum of dissolved radium-226 and radium-228. 

(D.R. Helsel, U.S. Geological Survey, oral commun., 

1988). Less-than values were set equal to the method 

detection limit (for example, <0.1 =0.1) for use in plots. 

Less-than values were excluded from 228Ra/226Ra activityratio calculations. Radon-222 e22Rn) measurements by the 

liquid scintillation method were made at the Physics Department, University of Maine, Orono, Maine. Reported 222Rn 

values are the mean of two samples collected at each site. A 

summary of the results of the radiochemical analyses is 

listed in table 48. 

Results of total radium and 222Rn sampling by county 

are presented in table 49. All counties except Berks ( 1 

sample) and Montgomery (4 samples) have wells in which 

Maximum Median samples Minimum Maximum Median 

1 114 

54±2.1 <1.4 5 760 3,530 1,630 

86±6.3 6.5±.4 53 228 9,270 2,070 

107±10 6.6±.6 18 475 24,500 1,950 

1.5± .4 <1.2 4 86 2,680 500 

14± 1.1 <1.4 22 180 20,320 2,300 

107±10 4.1 103 86 24,500 2,000 

the water exceeds the EPA MCL of 5 pCi/L total radium. 

Wells in Chester and Lancaster Counties, where much of 

the formation crops out, show the greatest numbers and 

percentage of samples above the EPA MCL. Elevated 

radium concentrations in ground water appear to be distributed throughout the formation. However, some areas of the 

Chickies Quartzite within each county seem more likely to 

have elevated radium concentrations in the ground water. 

This suggests that local lithology and hydrology may be 

controlling factors. 

Radon-222 concentrations differ throughout the formation and appear to be site specific with no regional trend. 

For example, two wells that are approximately 300 ft 

Radium-226, Radium-228, and Radon-222 in Ground Water of the Chickies Quartzite 271 
18 

16 

(/) 

5 14 

a:: ~ 12 I.LI 

(/) 

~ 10 

LL.. 

0 

a:: 

I.LI 

m 

~ 6 

z 

0 1 2 3 4 5 6 7 8 9 10 11121314151617181920212223242526272829303132 

ACTIVITY RATIO OF RADIUM-228 TO RADIUM-226 

Figure 109. Activity ratios of radium-228 to radium-226 for 

70 ground-water samples from the Chickies Quartzite. The 

range of ratios is 0.75 to 30. The median of ratios is 2.7. 

apart and have similar depths and similar hydrologic settings were sampled at the same time, and the mean 222Rn 

concentrations were 5,000 and 28,400 pCi/L. The larger 222Rn concentration (28,400 pCi/L) was obtained during the 

second sampling of the well. The concentration of the first 

sample (24,500 pCi/L) was used in the data analysis. 

In 97 samples, 228Ra concentrations e~ceeded those 

of 226Ra, and in the 10 samples where the 228Ra concentration was less than or equal to that of 226Ra, total radium 

concentrations were less than 5 pCi/L, and 228Ra concentrations were at or near the method detection limit. For the 

51 wells having total radium concentrations greater than 5 

pCi/L, all 228Ra concentrations were greater than those of 226Ra. Because 228Ra is a beta emitter, the screening of 

gross alpha-particle radioactivity for drinking water that has 

a potential for high radium values may need to be used with 

caution. 

Activity ratios of 228Ra to 226Ra were calculated for a 

subset of samples. Analytical determinations reported as 

less than the method detection limit were excluded from the 

calculations. Seventy analyses for which both 226Ra and 228Ra concentrations were above the method detection 

limits were used to calculate radium-isotope ratios. The 

activity ratios are reported only as a semiquantitative 

indicator of the apparently unusual 228Ra to 226Ra activity 

ratios observed in the ground water of the Chickies Quartzite. 

The range of 228Ra/226Ra activity ratios is 0. 75 to 30 

(fig. 109), and the median is 2. 7. The abundance of the 

parent radionuclides, thorium-232 e32Th) and uranium-238 

e38U), in the rocks of the Chickies Quartzite is not known. 

Mean crustal abundances are about 8. 5 ppm (parts per 

million) thorium and 2.7 ppm uranium (Durrance, 1986). 

For an average sandstone, the thorium content is estimated 

272 Field Studies of Radon in Rocks, Soils, and Water 

to be 1.7 ppm, and the uranium content is estimated to be 

0.45 ppm (Durrance, 1986). The activity ratio of 232Th to 238U may be estimated to be about 1.1 in the solid phase for 

an average sandstone or rocks that have mean crustal 

abundances of thorium and uranium. The expected 228Ra!226Ra activity ratio for water in contact with the rock 

should be close to unity if dissolution reactions and rates for 

the two radium isotopes are similar. Although a number of 

analyses fall near unity, 80 percent exceed 1. 5. It is 

suggested that the abundance of 232Th relative to 238U may 

be greater in the Chickies Quartzite than for an average 

sandstone. For example, an average thorium content of 

orthoquartzites is about 12 ppm (Durrance, 1986). The 

Hardyston Quartzite, also Early Cambrian in age and of 

similar lithology to the Chickies Quartzite, but cropping out 

to the north, contains a basal layer enriched in thorium and 

uranium. Three analyses of rock samples from the Hardyston yielded high thorium/uranium weight ratios (R.C. Smith 

II, Pennsylvania Department of Environmental Resources, 

Bureau of Topographic and Geologic Survey, oral commun., 1988), which are approximately equivalent to 232Th/238U activity ratios of 2.5 or greater. Therefore, 

differences in the observed ratios of 228Ra to 226Ra in the 

ground water of the Chickies Quartzite may reflect differences in composition of the aquifer material. Initial aquifer 

composition may have changed through preferential leaching of 238U or 234U at some time, and this leaching would 

account for relative depletion of 226Ra with respect to 228Ra 

in the ground water. 

Inorganic Constituents and Dissolved Organic 

Carbon 

Chemical analyses of water samples for inorganic 

constituents other than radionuclides and for dissolved 

organic carbon (DOC) were performed at the U.S. 

Geological Survey National Center. Water samples for 

determination of major and minor ions and dissolved 

organic carbon were collected at all sites, and a summary of 

available results is listed in table 50. The chemical data are 

not normally distributed and are positively skewed. 

Results of chemical analyses indicate that ground 

water in the Chickies Quartzite is soft (Durfor and Becker, 

1964), relatively dilute, and low in dissolved solids. More 

than 80 percent of samples have a hardness of less than 60 

mg/L as CaC03 • The sum of major cation milliequivalents 

ranges from 0.1 to 7.0 meq/L (milliequivalents per liter), 

and the median is 0.9 meq/L. Sodium is the dominant cation 

in some water samples, and sodium concentrations vary 

directly with chloride concentrations. In other samples, 

calcium and magnesium dominate. Dominant anions are 

bicarbonate and chloride, although in a few samples sulfate 
Table 50. Determinations of inorganic constituents and dissolved organic carbon in ground water in the Chickies 

Quartzite 

[mg!L, milligrams per liter; ~J.g/L, micrograms per liter; -, no samples below detection limits] 

Constituent Number 

of samples 

Number of 

samples below 

detection 

limits 

Range 

Minimum Maximum Median 

Major ions (mg/L) 

Calcium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 0.1 59 4.4 

Magnesium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 .2 38 3.3 

Sodium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 .7 59 4.2 

Potassium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 .3 11 1.9 

Chloride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 .3 83 8.2 

Sulfate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 1 <.2 62 6.2 

Fluoride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 43 <.1 .5 .1 

Silica . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 3.4 28 8.8 

Minor ions (J.tg/L) 

Barium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 4 2.0 380 66.5 

Manganese . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 8 1.0 870 33.5 

Iron, dissolved . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 6 3.0 27,000 35.5 

Other constituents 

Iron, total (j.Lg/L) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 

Total dissolved solids (mg/L) . . . . . . . . . . . . . . . . . . . . . . . . . . 93 

Dissolved organic carbon (mg/L) . . . . . . . . . . . . . . . . . . . . . . . 89 

is dominant. Associations between ions differ; sulfate and 

bicarbonate show a tendency to pair with magnesium or 

calcium. 

The laboratory and field data suggest that recharge to 

the ground water is local precipitation that has enriched 

sodium and chloride concentrations that are due to evapotranspiration and, possibly, contamination with road salt. 

Chemical analysis of precipitation collected since 1979 at a 

rain gage in central Chester County shows sodium, calcium, 

and magnesium concentrations of up to 1 mg/L, chloride 

concentrations of up to 1 mg/L, and sulfate concentrations 

of up to 10 mg/L, with pH as low as 3.6. The relatively low 

concentrations of calcium and magnesium, and low pH 

observed in the ground water, may be accounted for by the 

sparsity of easily dissolved or weathered feldspar and other 

silicates in the formation. The presence of dissolved iron 

and sulfate in the ground water may reflect oxidation of 

pyrite, a mineral that is known to occur in the Chickies 

Quartzite. Such a reaction would be favored in the acidic 

and oxygen-rich geochemical environment observed in the 

ground water. Relatively elevated concentrations of dissolved and total iron and dissolved manganese were measured in a few samples. 

Thirty percent of the samples had dissolved organic 

carbon concentrations greater than or equal to 1 mg/L. 

Median dissolved organic carbon concentrations for crystalline rock aquifers are reported as 0.5 mg/L, and for 

sandstone, limestone, and gravel aquifers as 0. 7 mg/L 

(Thurman, 1985). Three samples had elevated (greater than 

5.0 mg!L) concentrations of dissolved organic carbon for 

ground water; the well that had the highest concentrations of 

7 <10.0 51,000 230 

7.0 343 68 

.5 10.0 .8 

dissolved organic carbon in water was resampled later, and 

the ground water was found to be contaminated with 

manmade organic compounds. Naturally elevated dissolved 

organic carbon values may indicate short residence time or 

rapid transport of organic-rich recharge waters. 

RADIUM AND RADON IN GROUND WATER 

To evaluate the physical and chemical factors that 

may affect the source and mobility of radionuclides in the 

Chickies Quartzite, the nonparametric Spearman rank correlation test was used to determine the correlation between 

concentrations of radionuclides and well depth, well yield, 

and concentrations of other chemical constituents. The 

correlation coefficient, Spearman's rho (r5 ), measures 

monotonic trends, which may not be linear. Total radium 

and 222Rn concentrations were tested for correlation with 

well depth, well yield, pH, specific conductance, temperature, concentrations of alkalinity, dissolved organic carbon, 

calcium, magnesium, sodium, potassium, chloride, sulfate, 

silica, barium, total iron, dissolved iron, manganese, uranium, total dissolved solids, and dissolved oxygen. Because 

of the EPA MCL of 5 pCi/L for combined 226Ra and 228Ra, 

correlations were calculated for total radium. Radon-222 

was tested for correlation with its parent, 226Ra. 

A positive or negative correlation between the physical property or chemical constituent and · radionuclide 

concentration may be used to help predict anomalous 

radionuclide concentrations in ground water of the Chickies 

Quartzite. Because a significant correlation coefficient 

(positive or negative) does not necessarily imply a causeRadium-226, Radium-228, and Radon-222 in Ground Water of the Chickies Quartzite 273 
Table 51. Spearman rank correlation for chemical constituents and well yield with total radium (sum of dissolved 

radium-226 and radium-228) and radon-222 significant at 

the 95-percent confidence level 

Chemical constituent 

or physical property 

Correlation 

coefficient 

(Spearman's rho) 

Total radium 

Dissolved organic carbon . . . . . . 0.68 

pH . . . . . . . . . . . . . . . . . . . . . . . . . . -.66 

Silica . . . . . . . . . . . . . . . . . . . . . . . . - . 57 

Alkalinity .. .. .. .. .. .. .. .. .. .. -.50 

Barium . . . . . . . . . . . . . . . . . . . . . . .46 

Manganese . . . . . . . . . . . . . . . . . . . .35 

Chloride .. .. .. .. .. .. .. .. .. .. . .26 

Specific conductance . . . . . . . . . . .24 

Sodium . . . . . . . . . . . . . . . . . . . . . . .24 

Sulfate . . . . . . . . . . . . . . . . . . . . . . . .23 

Well yield .. .. .. .. .. .. .. .. .. . -.23 

Radon-222 

Sulfate . . . . . . . . . . . . . . . . . . . . . . . - .25 

Magnesium . . . . . . . . . . . . . . . . . . - .23 

Total dissolved solids . . . . . . . . . -.23 

Specific conductance . . . . . . . . . . - . 20 

p value 

<1 x w-6 

<1 x w-6 

<1 x w- 6 

<1 x w- 6 

4x w- 6 

.000632 

.013651 

.012464 

.0229 

.027777 

.047777 

.016846 

.027426 

.030419 

.04667 

and-effect relation, the correlations were evaluated in terms 

of possible geochemical reactions or physical processes that 

may control the concentration and distribution of radionuclides. The Spearman rank correlations significant at the 

95-percent level of confidence are listed in table 51. If the 

p value (the smallest level of significance that allows the 

null hypothesis to be rejected) for the Spearman rank 

correlation test is less than or equal to 0.05 (the significance 

level), then the null hypothesis that the two variables are 

independent is rejected. 

Radium 

A negative correlation between total radium concentration and pH in ground water of the Chickies Quartzite 

was first noted by Cecil and others ( 1987). Figure 110 is a 

scatter plot of total radium concentration and pH for 106 

wells in the Chickies Quartzite. Figure 110 shows that all 

samples having a pH lower than 4. 7 equal or exceed the 

MCL of 5 pCi/L for total radium. No water samples having 

a pH greater than 6.5 exceed the MCL for total radium. 

Low pH may reduce the adsorption of radium by 

mineral surfaces and thereby increase radium concentrations in the water. Experiments conducted by Riese (1982) 

showed that adsorption of radium by quartz and kaolinite is 

inhibited by low pH. The data presented in figure 110 

suggest that radium is not being adsorbed or otherwise 

immobilized in the low-pH water in the Chickies Quartzite. 

A scatter plot of total radium concentration as a 

function of manganese concentration (fig. 111) shows a 

positive correlation (rs = 0.35). Because radium is strongly 

27 4 Field Studies of Radon in Rocks, Soils, and Water 

100 

25 

MCL 

. : 

.. 

. .. .. . . . . . =·· : . : . . . . --------· :-t ~-....! .. -1-; .. _----------. -·---------------------- 0 ~~~~~~~~~~~~~~~~~~~ 

. . . 4 4.5 5.5 6 

pH 

6.5 7.5 8 

Figure 110. Relation between total radium concentration 

and pH for 106 wells in the Chickies Quartzite. MCL, the 

Environmental Protection Agency maximum contaminant 

level. 

adsorbed by manganese oxyhydroxides, the dissolution of 

manganese oxyhydroxides would result in the release of 

adsorbed Ra +2

• Eh and pH are important controls on 

manganese dissolution; however, the relation (correlation 

coefficient) between dissolved manganese concentration 

and pH was not statistically significant. 

A scatter plot of total radium concentration as a 

function of barium concentration (fig. 112) depicts a positive correlation (correlation coefficient, r5 = 0.46). This 

positive correlation may reflect the similar chemical behavior of barium and radium and also may reflect the dissolution of manganese oxyhydroxides. Manganese oxyhydroxides act as effective scavengers of barium and radium 

(Hem, 1985). Therefore, chemical environments favoring 

the dissolution of manganese oxyhydroxides may result in 

elevated concentrations of barium and radium in solution. 

This factor is supported by the correlation coefficient, r 5 = 

0.34, between manganese and barium that is significant at 

the 95-percent level of confidence. 

The positive correlation between total radium concentration and dissolved organic carbon shown in figure 113 

and supported by a correlation coefficient of 0. 68 suggests 

the possible complexation of radium by dissolved organic 

carbon. Thurman ( 1985) states "complexation of metal ions 

by organic matter is an important organic-inorganic process." Dissolved organic carbon has a cation-exchange 

capacity of about 1 microequivalent per milligram (Thurman, 1985). Given the low concentrations of cations in 

ground water of the Chickies, some exchange sites on 

dissolved organic carbon may be available for radium. The 
150 

100 

. . . .. . z . . . Qc::: 

~~ 

~:J 

1.&.11.&.1 

zc::: .. • (.)C.. . . ZVJ 

01.&.1 10 

UQ2 . . ::t=> 

:::>(..) . -0 

ou .. ~a: 

...JZ 

~-

:2 . . . . \ 

.. . . . .. ··-= 

0.5 

0.5 10 100 1000 

MANGANESE CONCENTRATION, IN MICROGRAMS PER LITER 

Figure 111. Relation between total radium and manganese 

concentrations for 92 wells in the Chickies Quartzite. 

relation between DOC and radium also may be coincidental, reflecting greater mobility of DOC and radium in low 

pH waters. 

Total radium shows a negative correlation with alkalinity and silica (table 51). Alkalinity and silica show 

positive correlations with pH (r5 = 0.89 and rs = 0.53, 

respectively). These correlations are significant at the 95-

percent confidence level. However, 226Ra and 228Ra concentrations have a negative correlation with pH, and this 

factor may explain the negative correlations between 

radium and alkalinity and radium and silica. Other physical 

properties or chemical constituents that show a slight 

positive correlation with total radium are specific conductance, sodium, chloride, and sulfate (table 51). This suggests that radium solubility increases with greater ionic 

concentrations. Total radium shows a slight negative correlation with well yield. 

Radon 

The data-point scatter in figure 114 indicates the lack 

of a linear relation between concentrations of 222Rn and its 

parent, 226Ra, in solution. Low total uranium 

concentrations1 (less than 0.05 to 4.49 pCi/L) and low 226Ra concentrations (fig. 114) indicate that 222Rn is unsup1

Uranium-isotope ratios are assumed to equal natural crustal abundances. The measured concentrations in micrograms per liter are multiplied by 0.68 pCi/j.Lg to convert uranium concentrations to picocuries per 

liter. 

150 

100 

z" 

Qc::: 

~I:!! 

~:J 

zc::: 

1.&.11.&.1 

(.)C.. 

ZVJ 

01.&.1 10 

UQ2 

::t=> 

:::>(..) 

-o Clu 

~a: 

...JZ 

~-

0 

1-

0.5 

1 10 

. . 

• • • I 

.. . 

. . 

. . .• • I 

... 

. .. . . .. 

. . . ... 

.. 

. . 

. . . .... . . . 

. .... . 

100 

. . 

500 

BARIUM CONCENTRATION, IN MICROGRAMS PER LITER 

Figure 112. Relation between total radium and barium 

concentrations for 92 wells in the Chickies Quartzite. 

100 

. . . . . . 

.. . . • • • 

. . . . 

. 

. 

••• 

• I 

• I : • • I 

... 

.. 

... 

0.5 L---~--'----1....--'--...J...._J.--l..J...J..__ __ .J...____._----L---.J..--'-"'--L--'-'-----' 

0.1 

DISSOLVED ORGANIC CARBON CONCENTRATION, 

IN MILLIGRAMS PER LITER 

10 15 

Figure 113. Relation between total radium and dissolved 

organic carbon concentrations for 89 wells in the Chickies 

Quartzite. 

ported in ground water of the Chickies Quartzite. The 

apparent lack of correlation between 222Rn and 226Ra 

concentrations in ground water has been reported by other 

investigators (Tanner, 1964; Snihs, 1972; Lee and others, 

1979). The variability of 222Rn concentrations in ground 

Radium-226, Radium-228, and Radon-222 in Ground Water of the Chickies Quartzite 275 
10,000 

. .. .. . . . . . . .. . . . . . ·-· . . .. . . \ 

•. . \ . . 1,000 N 

N 

N 

z 

I .... . 0 

0 .. <( 

~ 

100 

soL---~~~~~~----~~~~~~--~--~ 

0.1 10 

RADIUM-226 CONCENTRATION, IN PICOCURIES PER LITER 

40 

Figure 114. Relation between radon-222 and radium-226 

concentrations for 103 wells in the Chickies Quartzite. 

water from the Chickies Quartzite suggests that controls on 222Rn concentrations are site specific. In a fractured-rock 

aquifer, the proximity of 226Ra to water bearing zones, 

ground-water flow distance, and flow time will affect 

concentrations of 222Rn in solution. Wathen (1987) and 

Rumbaugh (1983) suggest that low uranium concentrations 

and· elevated 222Rn concentrations in ground water indicate 

a 226Ra source in the aquifer matrix close to the well rather 

than in the ground water. 

Radon-222 has a slightly negative significant correlation with specific conductance, sulfate, magnesium, and 

total dissolved solids (table 51). Mechanisms responsible 

for these relations are not presently understood. 

CONCLUSIONS 

Elevated concentrations of 226Ra and 228Ra in ground 

water in the Chickies Quartzite indicate that the geochemical environment favors the mobility of radium. Elevated 

radium concentrations in ground water are distributed 

throughout the formation. The ground water is dilute, soft, 

and acidic. The ground water contains detectable concentrations of dissolved iron and manganese and is slightly 

reducing with respect to these constituents. 

Adsorption is an important control on radium concentrations in solution. Low pH decreases the ability of quartz 

and kaolinite in the aquifer matrix to adsorb radium. Iron 

and manganese oxyhydroxides also provide possible 

adsorption sites, and the dissolution of these minerals 

decreases the number of available adsorption sites and may 

release adsorbed radium into solution. 

276 Field Studies of Radon. in Rocks, Soils, and Water 

Radium in solution may complex with dissolved 

organic carbon. Concentrations of dissolved radium 

increase with increasing concentrations of dissolved organic 

carbon. This fact suggests that complexation of radium with 

dissolved organic carbon may be an important control on 

dissolved radium concentrations and mobility in the ground 

water or that DOC and radium exhibit similar chemical 

behavior. 

Barium and radium exhibit similar chemical behavior. Data from this study show a positive correlation 

between barium and manganese concentrations and radium 

and manganese concentrations. Similar behavior of radium 

and barium with respect to manganese oxyhydroxide 

adsorption is implied. 

The slight positive correlation between dissolved 

radium concentrations and specific conductance indicates 

that radium solubility may increase with ionic strength in 

the ground water of the Chickies Quartzite. 

At pH less than 4. 7, all samples of ground water 

contained concentrations of total radium that exceeded the 

EPA MCL of 5 pCi/L. Low pH may be used as a predictor 

of elevated radium concentrations in ground water of the 

Chickies Quartzite. 

Sources of 226Ra, 228Ra, and 222Rn in the ground 

water appear to be from within the aquifer matrix of the 

Chickies Quartzite. Because the formation typically forms 

ridges and is a water-table aquifer recharged primarily by 

local precipitation, it is unlikely that radionuclides in 

solution have sources outside the formation. Observed 

· · . · f 228R d 226R fl t th 232 activity ratios o a an a may re ec e Th an d 238U content of the aquifer matrix and distribution of the 

thorium- and uranium-bearing minerals within the aquifer. 

. Lack of correlation between 222Rn and its parent, 226Ra, suggests that 222Rn is not supported by 226Ra in 

solution and that the source is in the aquifer matrix. 

Regional and local variability of 222Rn concentrations in 

ground water of the Chickies Quartzite indicates that 

controls on concentrations are site specific. 

REFERENCES CITED 

American Public Health Association and Water Pollution Control 

Federation, 1985, Standard methods for the examination of 

water and wastewater: Washington, D.C., American Public 

Health Association, 1,268 p. 

Bascom, F., 1905, Piedmont district of Pennsylvania: Geological 

Society of America Bulletin, v. 16, p. 296-298. 

Bascom, F., and Stose, G.W., 1938, Geology and mineral 

resources of the Honey brook and Phoenixville quadrangles, 

Pennsylvania: U.S. Geological Survey Bulletin 891, 145 p. 

Berkheiser, S. W., 1985, High-purity silica occurrences in Pennsylvania: Pennsylvania Geological Survey, 4th ser., Mineral 

Resource Report 88, 67 p. 

Cecil, L.D., Smith, R.C., II, Reilly, M.A., and Rose, A.W., 

1987, Radium-228 and radium-226 in ground water of the 

Chickies Formation, southeastern Pennsylvania, in Graves, 
B., ed., Radon in ground water: Chelsea, Mich., Lewis 

Publishers, Inc., p. 437-447. 

Durfor, C.N., and Becker, E., 1964, Public water supplies of the 

100 largest cities in the United States, 1962: U.S. Geological 

Survey Water-Supply Paper 1812, 363 p. 

Durrance, E.M., 1986, Radioactivity in geology: Principles and 

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441 p. 

Dryden, L., and Dryden, C., 1964, Source-rock heavy minerals of 

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College, Bryn Mawr, Pa., 58 p. 

Environmental Protection Agency, 1978, Radon in water sampling 

program: Publication EPA/EERF-Manual-78-1, 11 p. 

---1986, Maximum contaminant levels (subpart B of part 

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U.S. Code of Federal Regulations, Title 40, Parts 100 to 149, 

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Cliffs, N.J., Prentice-Hall, Inc., 604 p. 

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Goodwin, P.W., and Anderson, E.J., 1974, Associated physical 

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Cambrian tidal sand body: Journal of Geology, v. 82, p. 

779-794. 

Hem, J.D., 1985, Study and interpretation of the chemical 

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Survey Water-Supply Paper 2254, 264 p. 

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New York: U.S. Geological Survey Miscellaneous Investigations Series Map 1-1715, scale 1 :250,000, 2 sheets. 

McGlade, W.G., Geyer, A.R., and Wilshusen, J.P., 1972, 

Engineering characteristics of the rocks of Pennsylvania: 

Pennsylvania Geological Survey, 4th ser.: Environmental 

Geology Bulletin 1, 200 p. 

Riese, A. C., 1982, Adsorption of radium and thorium onto quartz 

and kaolinite: A comparison of solution surface equilibria 

models: Unpublished Ph.D. dissertation, Colorado School of 

Mines, 292 p. 

Rumbaugh, J.O., III, 1983, Effect of fracture permeability on 

radon-222 concentration in ground water of the Reading 

Prong, Pennsylvania: Unpublished M.Sc. thesis, Pennsylvania State University, 111 p. 

Snihs, J.O., 1972, The content of some natural radioactive 

elements, especially Rn-222, in some potable waters in 

Sweden: Nordic Hydrology, v. 4, p. 256-274. 

Stose, A.J., and Stose, G.W., 1944, Geology of the Hanoveryork District: U.S. Geological Survey Professional Paper 

204, 84 p. 

Stose, G.W., and Jonas, A.l., 1939, Geology and mineral 

resources of York County, Pennsylvania: Pennsylvania Geological Survey, 4th ser., County Report 67, 199 p. 

Tanner, A.B., 1964, Radon migration in the ground: A review, in 

Adams, J.A.S., and Lowder, W.M., eds., The natural 

radiation environment: Chicago, Ill., University of Chicago 

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Catskill Formation, eastern Pennsylvania: unpublished M.Sc. 

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Thurman, E.M., 1985, Organic geochemistry of natural waters: 

Dordrecht, Netherlands, Marinus Nijoff/Dr. W. Junk Publishers, 497 p. 

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Pennsylvania Geological Survey, 4th ser., County Report 9, 

243 p. 

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U.S. Geological Survey Techniques of Water-Resources 

Investigations, Book 1, Chap. D2, 24 p. 

Radium-226, Radium-228, and Radon-222 in Ground Water of the Chickies Quartzite 277 

RADON IN GROUND WATER OF CARSON VALLEY, WEST-CENTRAL NEVADA 

Michael S. Lico and Timothy G. Rowe 

Abstract 

Radon-222 activities in ground-water samples from 

the basin-fill sedimentary aquifers of Carson Valley were 

determined to delineate the areal distribution of, and 

possible geochemical controls on, the radon-222. Activities of radon-222 in 30 ground-water samples ranged from 

less than 100 to 10,000 picocuries per liter and have a 

median activity of 480 picocuries per liter. The highest 

radon-222 activities are in ground water from the confined 

alluvial-fan deposits along the western periphery of Carson Valley. 

Several factors may contribute to the high radon-222 

activity in ground water of Carson Valley. First, Cretaceous 

granitic rocks of the Carson Range (western border of 

Carson Valley) contain uranium in concentrations as high 

as 10 milligrams per kilogram. These rocks, both as alluvial 

detritus and bedrock, may contribute significant amounts 

of radon-222 to ground water in the alluvial-fan deposits. 

Second, ground water enriched in radon-222 may flow 

from fractured bedrock into the alluvial-fan aquifer. Third, 

water rich in radon-222 also may be moving upward along 

a major fault bordering the eastern side of the Carson 

Range. Fourth, organic-rich sediments along the western 

side of Carson Valley contain high uranium concentrations (greater than 53 milligrams per kilogram) and may be 

releasing radon-222 to the ground water. These factors, 

along with the composition of radon-222-enriched water 

and the slope of the piezometric surface, indicate that 

most of the radon-222 is derived from the Carson Range. 

INTRODUCTION 

The major source of domestic drinking water in 

Carson Valley is ground water. Recent increases in population have resulted in the construction of many new private 

and municipal wells. Although little is known about the 

distribution and occurrence of radon-222 CZ22Rn) in ground 

water of western Nevada, previous studies suggest that high 

activities may exist, and these activities would pose some 

risk to the population. Otton and others (1985, p. 21) found 

anomalous activities of 222Rn in water from springs in the 

Lake Tahoe basin (fig. 115). The same study (Otton and 

others, 1985, table 1) revealed that slightly elevated concentrations of uranium, 5-53 mg/kg (milligrams per kilogram), are present in the valley-fill sediments derived from 

the Carson Range along the western margin of Carson 

Valley. A study of public drinking-water supplies (Horton, 

1985, p. 123) found high activities of 222Rn in the Gardnerville, Reno, and Yerington areas. 

Radon-222 is a naturally occurring, colorless, odorless, inert gas that is formed by the radioactive decay of 

uranium-238 (Wanty and Schoen, this volume). Uranium238 is present in trace concentrations in all rocks, with 

certain types such as granitic rocks, late-stage volcanic 

rocks, shales, and limestones generally having higher uranium concentrations (Lanctot and others, 1985, p. 68). Two 

intermediate radioactive decay products of the uranium-238 

decay series, thorium-230 and radium-226, are important in 

determining the amount of 222Rn generated. Because both 

thorium and radium tend to be immobile under most 

geohydrologic conditions, the uranium content of rocks 

generally is a good indicator of 222Rn activity in associated 

ground water. 

Several natural geochemical processes can concentrate uranium-238 in the environment. Late-stage igneous 

rocks, present in western Nevada, are rich in uranium 

because of the occlusion of uranium from the crystal lattice 

of early-forming minerals. The same process occurs in 

high-grade metamorphic rocks during recrystallization and 

enriches the late-crystallizing minerals with uranium. Uranium also can be concentrated by transport, by way of 

ground water, from an oxidizing to a reducing environment. 

Roll-front uranium deposits (Turner-Peterson and Fishman, 

1986) exemplify this type of process. Otton and others 

( 1985, p. 7) have reported several areas in the Carson 

Range where organic-rich bog sediments have accumulated 

uranium. Hydrothermal fluids also can produce deposits of 

extremely high uranium content. 

Radon-222 is radioactive, and at high concentrations 

it and its daughter products can cause lung cancer in humans 

(Cothern, 1987, p. 7). Radon-222 released from drinkingwater sources has been estimated to cause as much as 7 

percent of the lung cancer fatalities (between 5,000 and 

20,000 per year) attributed to 222Rn (Cothern and others, 

1986, p. 40). Radon gas is released from water to the 

atmosphere by any one of several household activities, 

including showering and laundering (Lowry and others, 

1987, p. 363). 

Human exposure to 222Rn, and its radioactive daughter products (isotopes of polonium, lead, and bismuth), is 

possible through (1) inhalation of 222Rn gas or decay 

products that adhere to small dust particles and directly 

affect the lungs and (2) ingestion of 222Rn-containing water, 

by which the dose of radiation to the stomach and intestines 

is increased (Brutsaert and others, 1981, p. 407). Potential 

health effects are greatest to private domestic well-water 

users by these exposure pathways because of the generally 

short time between pumping and consumption of well 

water. The half-life of 222Rn is relatively short (3.82 days); 

thus, the residence time of water in public-supply 

Radon in Ground Water of Carson Valley, West-Central Nevada 279 
systems and loss to the atmosphere in storage tanks would 

determine the potential effects of high 222Rn activity in 

these systems. 

Purpose and Scope 

The primary purpose of this report is to describe the 

areal distribution of 222Rn in ground water in Carson 

Valley, west-central Nevada. A secondary purpose is to 

relate high 222Rn activities with certain types of rocks or 

sediments. This investigation was made during 1987 by the 

U.S. Geological Survey. 

Description of Study Area 

Figure 115 shows the location and general features of 

the study area. Most of Carson Valley lies in west-central 

Nevada; the extreme southwestern part of the valley lies in 

California. Carson Valley is bordered on the west by the 

Carson Range of the Sierra Nevada (maximum altitude, 

about 10,000 ft (feet)) and on the east by the Pine Nut 

Mountains (maximum altitude, nearly 9,000 ft). Carson 

Valley is approximately 15 mi (miles) wide and 24 mi long, 

with a valley floor that slopes from altitudes of about 5,000 

ft in the south to about 4,600 ft in the north (Maurer, 1986, 

p. 7). The major population center in Carson Valley is the 

Minden-Gardnerville area. The economy of Carson Valley 

is dominated by agriculture and related activities. 

The climate on the valley floor is semiarid, with mean 

annual precipitation of less than 9 in (inches) (Glancy and 

Katzer, 1976, table 4) and mean annual evapotranspiration 

exceeding 40 in (Pennington, 1980, table 9). The Carson 

Range and the Pine Nut Mountains receive 45 and 26 in of 

precipitation, respectively, in an average year, most of 

which is winter snowfall (Maurer, 1986, p. 7). 

Methods of Sample Collection and Analysis 

Water samples considered representative of the sampled aquifers were obtained at each well by pumping or 

bailing until water temperature, specific conductance, and 

pH were constant, and a minimum of three well-bore 

volumes was extracted. With the public supply and domestic wells (table 52), existing in-well pumps were used, and 

the sample was obtained as near to the well as possible. The 

observation wells (table 52) were sampled by use of a 

Teflon bailer. Loss of 222Rn gas due to aeration by the pump 

may be significant in water samples from public-supply 

wells. Radon-222 values produced for samples from these 

wells represent minimum 222Rn activities. 

A sample for radon analysis was obtained by filling a 

1-L (liter) polyethylene bottle gently to avoid aeration. A 

10-mL (milliliter) water sample from the bottle was with280 Field Studies of Radon in Rocks, Soils, and Water 

drawn with a syringe below the water surface. The 10-mL 

sample was added to a 30-mL glass scintillation vial that 

contained 5 mL of a mineral-oil-based liquid scintillator by 

careful injection of the water sample underneath the mineral 

oil. The vial then was capped tightly and shaken. The vials 

were shipped by express mail to the contract laboratory for 

analysis by liquid scintillation counting. Samples were 

shipped as soon as possible after collection so radon decay 

would be minimized prior to analysis. 

Duplicate water samples were collected from each 

well for 222Rn analysis. The duplicate analyses generally 

agreed to within 5 percent and were averaged and reported 

as one value. For differences greater than 5 percent, the 

larger value is reported. 

The radon concentrations in five well waters (sites 

14, 15, 19, 28, and 29 in table 54) were measured by use of 

a field-screening method. A 1-L polyethylene bottle was 

filled with 750 mL of water and capped with a septum cap. 

The bottle was shaken vigorously for 30 seconds and then 

allowed to stand for 3 minutes. A 50-mL sample of the 

head-space gas was removed through the septum cap with a 

syringe and needle. The gas sample was injected, through a 

septum connector, into an evacuated Lucas-type, phosphorcoated cell. The cell was inserted into an EDA RDA-200 

alpha scintillometer, and the gas activity counted for 30 

minutes. The counts were converted to radon activities in 

picocuries per liter. 

GEOHYDROLOGIC SETTING 

Geology 

The area discussed in this report is entirely within the 

borders of the Cretaceous Sierra Nevada batholith (Moore, 

1969, p. 1). Pre-Cretaceous rocks, which are present as roof 

pendants in the batholith, include for the most part Triassic 

and Jurassic metamorphosed volcanic rocks and volcanically derived sedimentary rocks (fig. 116 and table 53). 

Some limestone and gypsum are interbedded with the 

clastic and volcanic rocks. The Cretaceous batholith is, in 

this area, composed of quartz monzonite, granodiorite, and 

some mafic rocks. 

Overlying the granitic and metamorphic rocks is a 

thick sequence of Cenozoic volcanic and interbedded sedimentary rocks. Generally, this sequence begins with 

Miocene rhyolitic tuff that is several thousand feet thick. 

Overlying the rhyolite is a thick accumulation of Miocene 

and Pliocene andesitic and dacitic breccias interbedded with 

lacustrine and fluviatile sediments. The youngest volcanic 

rocks are Pliocene and Pleistocene basaltic flows that cap 

many of the mountain ranges. 

Alluvium is present as valley-fill sediments throughout the area. The older alluvial deposits include pediment 

gravel of Pliocene to Pleistocene age capping poorly con-
NEVADA 

0 

I 

0 

R. 19 E. 

I 

119° 45' 

10 MILES 

I 

10 KILOMETERS 

R. 21 E. 

T. 

15 

N. 

T. 

14 

N. 

T. 

13 

N. 

T. 

12 

N. 

T. 

11 

N. 

EXPLANATION 

VALLEY -FILL SEDIMENTS 

CONSOLIDATED ROCKS 

- • •- BOUNDARY OF CARSON VALLEY 

HYDROGRAPHIC AREA 

---;Jill~ GENERAL DIRECTION OF 

GROUND-WATER FLOW 

SAMPLING SITES AND RANGES OF RADON-222 

ACTIVITY --Site numbers (table 52, 54 ) are indicated 

3 e Less than 500 picocuries per liter 

500-1 ,000 picocuries per liter 

1 ,001-5,000 picocuries per liter 

More than 5,000 picocuries per liter 

Figure 115. Location of study area and sampling sites. Symbols indicate levels of radon-222 activities. 

solidated Tertiary sediments. Younger alluvium, mainly 

alluvial-fan gravel and stream-laid gravel, sand, and silt, 

occupies the valley floor and attains a thickness of at least 

5,000 ft (Maurer, 1986, plate 2). 

The geologic structure of the study area is dominated 

by normal faulting. Most of the deformation was during two 

general periods, one preceding and accompanying the 

emplacement of the Cretaceous granitic rocks and the other 

consisting of normal faulting, warping, and tilting, in late 

Tertiary and Quaternary time. The Carson Range, a major 

part of the study area, is an uplifted block that has 

prominent normal faults bordering it on the eastern and 

Radon in Ground Water of Carson Valley, West-Central Nevada 281 
Table 52. Data on sampled wells, Carson Valley, Nev. 

(-, data not available] 

Site no. local Depth (feet below land surface) 

(fig. 115) identification 1 Producing Total Aquifer Use3 Reported lithology of 

interval unit2 producing interval 

1 ............ 105 N12 E19 15ABAD1 125-300 300 A p Sand, gravel, clay lenses. 

2 ............ 105 N12 E19 23DDD1 121-141 141 A D Decomposed granite, clay lenses. 

3 ............ 105 N12 E20 04ADA1 100-300 300 c p Sand, gravel, some clay lenses. 

4 ............ 105 N12 E20 11ADD1 105-125 125 B D Gravel and sand. 

5 ............ 105 N12 E20 15ADD1 183-372 375 c p Gravel, cobbles, cemented gravel, clay. 

6 ............ 105 N12 E20 17CCD1 67-87 91 B D Gravel. 

7 ............ 105 N12 E20 20ABAA1 200-450 450 p Gravel, sand, clay lenses. 

8 ............ 105 N12 E20 24ADC1 122-142 145 D Gravel. 

9 ............ 105 N12 E21 18CAB1 D No report. 

10 ............ 105 N13 E19 09ADCA1 156-176 180 A D Gravel, broken rock, clay lenses. 

11 ............ 105 N13 E19 10DBB1 80-115 115 A D Sand, gravel, clay lenses. 

12 ............ 105 N13 E19 13BCC1 150-500 518 A I Sand, gravel, clay lenses. 

13 ............ 105 N13 E20 02CBB 1 156-176 176 B D Sand. 

14 ............. 105 N13 E20 08CAA1 110-125 135 B D Sand. 

15 ............ 105 N13 E20 18BAAA1 20 B 0 No report. 

16 ............ 105 N13 E20 26ABB1 72-85 150 B D Decomposed granite, sand, clay lenses. 

17 ............ 105 N13 E20 29BDDD1 93-114 118 c D Sand, gravel. 

18 ............ 105 N 13 E20 29CDC 1 400 p No report. 

19 ............ 105 N13 E20 30BCAD1 200-360 360 c p Gravel, clay lenses. 

20 ............ 105 N13 E20 34ACC1 D No report. 

21 ............ 105 N13 E21 33BCAB1 140-160 163 D Gravel, clay lenses. 

22 ............ 105 N14 E19 12ADA2 120-150 155 B D Gravel, sand, and clay lenses. 

23 ............ 105 N14 E19 14BBD1 76-96 100 A D Decomposed granite, clay lenses. 

24 ............ 105 N14 E20 06CBAB2 73-93 96 B D Sand. 

25 ............ 105 N14 E20 17ADCA1 27 B 0 No report. 

26 ............ 105 N14 E20 18ABAB1 151-301 425 c p Gravel and clay. 

27 ............ 105 N14 E20 28CDC1 68-88 88 B D Gravel. 

28 ............ 105 N14 E20 30DCCB1 20 B 0 No report. 

29 ............ 105 N14 E20 32DCCC1 21 B 0 No report. 

30 ............ 105 N14 E20 34BDC1 100 D No report. 

1

The local site-identification system used in this report is based on an index of hydrographic areas in Nevada (Rush, 1968) and the rectangular 

subdivision of the public lands referenced to the Mount Diablo base line and meridian. Each site designation consists of four units separated by spaces. 

The first unit is the hydrographic area number. The second unit is the township, preceded by anN or S to indicate location north or south of the base line. 

The third unit is the range, preceded by an E to indicate location east of the meridian. The fourth unit consists of the section number and letters designating 

the quarter section, quarter-quarter section, and so on (A, B, C, and D indicate the northeast, northwest, southwest, and southeast quarters, respectively), 

followed by a number indicating the sequence in which the site was recorded. For example, site 105 N12 E20 4ADA1 is in Carson Valley (hydrographic 

area 105). It is the first site recorded in the NE 114 of theSE 114 of the NE 1/4 of section 4, Township 12 North, Range 20 East, Mount Diablo base line 

and meridian. 

2

Aquifer unit refers to unit of unconsolidated Quaternary sedimentary aquifer: A, confined alluvial-fan unit; B, unconfined fluviatile and lacustrine 

unit; and C, confined fluviatile and lacustrine unit. 3

Use of well: D, domestic-supply well; I, irrigation well; 0, observation well; P, public-supply well. 

western flanks. These faults have displacements of at least 

4,000 ft (Moore, 1969, p. 17). The Pine Nut Mountains 

constitute a west-tilting structural block that borders the 

study area on the east. The west flank of these mountains is 

dominated by many north-trending normal faults that have 

relatively small displacements (Moore, 1969, p. 18). 

The uranium and thorium concentration of sediment 

derived from the various rock types in the area has been 

determined by the National Uranium Resource Evaluation 

program (Bennett, 1980). Samples were taken from source 

areas of Jurassic, Tertiary, and Quaternary rocks. Generally, uranium concentrations range from about 2 to 5 mg/kg 

282 Field Studies of Radon in Rocks, Soils, and Water 

(milligrams per kilogram), and thorium from 4 to 16 mg/kg 

in stream sediment, regardless of the age of the source 

rocks. Forty-seven shallow soil samples collected in Carson 

Valley by the U.S. Geological Survey (Ron Tidball, written 

commun., 1988) had a thorium concentration that averaged 

11 mg/kg and ranged from 5 to 42 mg/kg. Data for uranium 

and thorium content of the silicic volcanic rocks in the study 

area are lacking. Elsewhere in the northern Basin and Range 

province, however, Walker (1981) found the uranium and 

thorium content of silicic volcanic complexes, mostly 

rhyolites, to range from 2 to 17 and 6 to 66 mglkg, 

respectively. 
Table 53. Generalized stratigraphy of the Carson Valley study area (modified from Moore, 1969) 

Age Rock unit 

(map symbol) 

Quaternary Younger alluvium (Qal) 

Older alluvium (QToa) 

Quaternary 

and Tertiary Basaltic rocks (QTb) 

Andesitic rocks (Ta) 

Tertiary Sedimentary rocks (Ts) 

Rhyolitic rocks (Tr) 

Granitic rocks 

Cretaceous of the Sierra Nevada 

batholith (Kg) 

Metasedimentary rocks (JRs) 

Jurassic 

and Triassic 

Metavolcanic rocks (JRv) 

Hydrology 

Three generalized aquifers are present in the Carson 

Valley study area (fig. 117): (1) an unconsolidated Quaternary sedimentary aquifer, (2) a poorly consolidated Tertiary 

sedimentary aquifer, and (3) a granitic and metamorphic 

bedrock aquifer surrounding and underlying the basin-fill 

sediments (Maurer, 1986, p. 16). 

The unconsolidated Quaternary sedimentary aquifer 

is the most common source of water for domestic, municipal, and irrigation supply in Carson Valley. This aquifer 

has been further subdivided by Maurer (1986, p. 16) into 

(1) a confined unit consisting of alluvial-fan deposits along 

the western side of the valley, (2) an unconfined unit of 

fluvial and lacustrine sediments present throughout the 

valley, and (3) a confined unit consisting of fluvial and 

lacustrine sediments present throughout the valley. 

Ground-water flow in the unconfined (water-table) 

unit is generally toward the center of the valley from the 

east and west, and then north along an axis approximately 2 

mi west of U.S. Highway 395 (see fig. 115). Gradients 

range from about 5 ft/mi in the north to as great as 100 ft/mi 

in the southwestern and western parts of the valley (Maurer, 

1986, p. 17). Water in the underlying confined units 

Description 

Mainly alluvial-fan gravel, stream-laid gravel, sand, and 

silt, with some talus and dune sand. Also includes some 

fine sand, silt, and clay of river flood plains, and playa 

clay and sand. 

Predominantly fanglomerate and pediment gravel; 

includes terrace gravel and late Pleistocene lake beds. 

Predominantly thin lava flows, with interbeds of scoriaceous basalt breccia and diatomaceous sediments. 

Flow breccias, lava flows, .and agglomerates, with interbedded sediments. Locally includes basaltic and rhyolitic 

rocks. 

Lacustrine and fluviatile sediments. Sandstone, shale, 

mudstone, marl, diatomite, limestone, and calcareous 

tufa. Includes interbedded tuffaceous rocks, lava flows, 

and breccias. 

Rhyolitic tuffs, flows, and intrusions. Biotite rhyolite 

pumice tuff-breccia and welded tuff are widespread. 

Granite porphyry, porphyritic quartz monzonite, nonporphyritic quartz monzonite, granodiorite, and hybrid mafic 

rocks. 

Shale, slate, tuffaceous siltstone, sandstone, and graywacke, largely derived from volcanic rocks. Includes 

interbeds of conglomerate, limy shale, limestone, 

dolomite, and gypsum. 

Andesite breccias, tuffs, and flows; basalt; and rhyolite; 

with interbedded volcanic-derived sedimentary rocks and 

limestone. Metamorphosed to greenschist or higher 

facies. 

generally flows in the same direction as in the water-table 

unit but with reduced gradients. The depth to water ranges 

from about 5 ft on the valley floor to more than 100 ft on the 

alluvial fans along the margins of the valley. 

DISTRIBUTION OF RADON IN THE GROUND 

WATER 

Ground water is the major source of drinking water in 

the Carson Valley. Most households outside of the urban 

Minden-Gardnerville area use private wells as water 

sources. Residences are distributed throughout the valley in 

such a way as to allow good areal coverage for the sampling 

of ground water. Samples were collected from the deeper 

confined units and the shallow water-table unit (table 52). 

Radon-222 activities in ground water sampled for this 

study ranged from less than 100 to 10,000 pCi/L (picocuries 

per liter; table 54). The distribution of 222Rn activities in 

Carson Valley is shown in figure 118. Activities of 222Rn 

are log-normally distributed about a median value of 480 

pCi/L, except for the two highest values (5,600 and 10,000 

pCi/L). Without exception, the highest 222Rn activities 

(> 1,000 pCi/L) determined in this study were present in 

Radon in Ground Water of Carson Valley, West-Central Nevada 283 
0 

I 

0 

B 

laToaf 

JaTbl 

G 

G 

G 

I 

5 

5 

I 

I 

CARSON 

VALLEY 

QaJ 

Minden- • Gardnerville 

10 MILES I 

10 KILOMETERS 

EXPLANATION 

YOUNGER ALLUVIUM GJ 

OLDER ALLUVIUM G 

BASAL TIC ROCKS E1 

ANDESITIC ROCKS 

SEDIMENTARY ROCKS -··- RHYOLITIC ROCKS 

GRANITIC ROCKS OF THE SIERRA 

NEVADA BATHOLITH 

METASEDIMENTARY ROCKS 

METAVOLCANIC ROCKS 

FAULT -- Ball on downthrown side 

BOUNDARY OF CARSON 

VALLEY HYDROGRAPHIC 

AREA 

Figure 116. Generalized geology of the study area and adjacent areas. Modified from Moore (1969); see table 

53 for description of rock units. 

284 Field Studies of Radon in Rocks, Soils, and Water 
West East 

Carson Range 

Carson Valley 

EXPLANATION 

FLUVIATILE AND LACUSTRINE DEPOSITS-- Ground 

water can be confined or unconfined 

f1f.~.'tk1ia Dominated by cobbles and gravel 

('V;WN}/td 

F--=--=--3 

Dominated by sand and silt 

Dominated by clay -- Thick units 

overlying bedrocK are of Tertiary 

age 

r:t~!iJ~~ ~k,~~~~!~i~f~e~e~~~~~in~oorly sorted; 

- BEDROCK 

MAJOR FAULT-- Arrows show 

relative direction of movement 

GROUND-WATER FLOW PATH 

WATER TABLE 

Figure 117. Cross section of hydrogeologic relations in Carson Valley. Upper part of basin-fill section is Quaternary age 

and lower part is Tertiary age. View looking north, modified from Maurer (1986, p. 44). 

ground water from wells along the extreme western side of 

Carson Valley. These wells (table 52) are completed in or 

close to the alluvial-fan deposits at the base of the Carson 

Range. 

GEOLOGIC AND GEOCHEMICAL CONTROLS 

ON RADON IN THE GROUND WATER 

The high activities of 222Rn in ground water from the 

western side of Carson Valley may be caused by several 

factors. The alluvial-fan deposits along the western side of 

the valley consist primarily of coarse-grained, relatively 

fresh detritus from the Cretaceous intrusive rocks of the 

Carson Range. These rock fragments have been mechanically weathered but show little evidence of chemical weathering (Otton and others, 1985, p. 25). Uranium concentration ranges from 2.9 to 10.1 mg/kg and averages 5.4 mg/kg 

in granitic rocks in the Carson Range (Otton and others, 

1985, p. 23). Because of their high uranium concentrations, 

the granitic rocks may generate sufficient 222Rn to contribute to the associated ground water and cause the high 222Rn 

activities measured. 

10~~~--~~~~~~~~~~--r-~-,--, 

9 

en 8 z 

Q 7 

~ 

6: 6 w 

~ 5 

0 

~ 4 a: 

~ 3 ~ 

::) 

z 2 

0 

1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4":2 

LOGARITHM OF RADON-222 ACTIVITY, IN PICOCURIES PER LITER 

Figure 118. Distribution of radon-222 activities in sampled 

ground water. 

Another possible factor that may be contributing to 

elevated 222Rn activities in ground water associated with the 

alluvial-fan deposits is direct flow into the aquifer 

Radon in Ground Water of Carson Valley, West-Central Nevada 285 
1-,J 

= ~ 

., 

;::r 

es: 

~ c 

Q. 

~· 

Q 

-

Q 

~ 

= :r 

:::0 

Q 

I') 

~ 

~ 

til 

~ ~ 

I» 

Q. = 

~ 

a 

~ 

Table 54. Analyses of water from sampled wells in the Carson Valley 

[Chemical analyses are measures of dissolved concentration in milligrams per liter, except as indicated. Abbreviations: °C, degrees Celsius; 1-LS/cm, microsiemens per centimeter; !-LgiL, micrograms per 

liter; pCi/L, picocuries per liter; -, data not available] 

pH Water Site no. 

(fig. 115) Sample date (standard temperature 

Specific 

conductance 

<v..S/cm) 

Calcium Magnesium Sodium Potassium Bicarbonate Carbonate Sulfate Chloride Fluoride 

Iron 

(f.Lg/l) 

I ....... . 

2 0 0 0 0 0 0 0 0 

3 0 0 0 0 0 0 0 0 

4 0 0 0 0 0 0 0 0 

5 0 0 0 0 0 0 0 0 

6 0 0 0 0 0 0 0 0 

7 0 0 0 0 0 0 0 0 

8 0 0 0 0 0 0 0 0 

9 0 0 0 0 0 0 0 0 

10 0 0 0 0 0 0 0 0 

87-06--23 

87-04-16 

87-04-13 

87-04-15 

87-04-10 

87-04-16 

87-06-23 

87-04-28 

87-04-14 

87-04-29 

II . . . . . . . . 87-04-29 

12 0 0 0 0 0 0 0 0 87-04-28 

13 0 0 0 0 0 0 0 0 87-04-15 

14 0 0 0 0 0 0 0 0 87-04-27 

15 0 0 0 0 0 0 0 0 87-06-29 

16 0 0 0 0 0 0 0 0 87-04-13 

17 0 0 0 0 0 0 0 0 87-04-15 

18 0 0 0 0 0 0 0 0 87-04-27 

19 0 0 0 0 0 0 0 0 87-06-25 

20 0 0 0 0 0 0 0 0 87-04-16 

21 0 0 0 0 0 0 0 0 87-06-24 

22 0 0 0 0 0 0 0 0 87-04-30 

23 0 0 0 0 0 0 0 0 87-04-29 

24 0 0 0 0 0 0 0 0 87-05-30 

25 0 0 0 0 0 0 0 0 87-04-29 

26 0 0 0 0 0 0 0 0 

27 0 0 0 0 0 0 0 0 

28 0 0 0 0 0 0 0 0 

29 0 0 0 0 0 0 0 0 

30 0 0 0 0 0 0 0 0 

87-04-16 

87-04-17 

87-06-30 

87-06-30 

87-04-17 

units) (

0

C) 

6.9 12.0 

7.8 15.0 

7.2 12.0 

8.1 11.0 

7.3 12.0 

6.9 13.5 

8.7 17.5 

7.9 14.0 

7.5 21.0 

7.2 12.0 

7.6 

8.0 

8.0 

8.0 

7.2 

7.7 

7.9 

8.4 

8.9 

7.8 

8.0 

8.2 

8.6 

7.4 

6.7 

8.6 

8.0 

7.5 

7.9 

7.7 

13.0 

15.5 

20.0 

15.0 

12.0 

15.5 

12.0 

14.0 

12.0 

14.0 

14.5 

13.0 

15.0 

13.5 

14.0 

19.0 

15.0 

12.0 

13.5 

16.0 

82 

102 

385 

273 

219 

200 

351 

578 

414 

282 

199 

196 

339 

383 

889 

318 

476 

183 

164 

300 

331 

243 

117 

518 

3,670 

260 

473 

401 

397 

353 

8.4 

5.2 

44 

34 

22 

21 

8.2 

78 

34 

42 

28 

15 

9.2 

38 

100 

31 

63 

21 

15 

33 

35 

18 

13 

61 

230 

14 

38 

43 

20 

15 

1 Samples for 222Rn analyses were collected August 24-27, 1987. 

1.0 

.5 

13 

6.4 

6.8 

8.7 

2.0 

14 

5.0 

5.7 

5.7 

4.3 

3.0 

2.9 

23 

9.3 

16 

3.9 

3.0 

7.4 

II 

2.0 

.07 

7.1 

6.9 

1.7 

4.3 

7.6 

8.1 

4.9 

7.4 

18 

21 

16 

14 

II 

70 

26 

53 

15 

10 

17 

59 

41 

65 

24 

20 

13 

19 

23 

25 

33 

14 

41 

570 

42 

63 

31 

58 

56 

0.6 

.7 

2.8 

2.2 

1.8 

2.3 

.9 

2.5 

2.4 

3.1 

1.4 

4.4 

3.8 

3.6 

5.4 

2.9 

3.4 

2.1 

2.5 

1.6 

3.9 

1.7 

1.0 

2.6 

6.8 

.7 

3.5 

5.1 

1.9 

3.3 

41 

36 

195 

127 

97 

102 

146 

248 

168 

184 

125 

100 

138 

101 

310 

172 

275 

93 

78 

164 

136 

107 

65 

227 

143 

111 

169 

195 

183 

128 

<I 

<I 

<I 

<I 

<I 

<I 

5 

<I 

<I 

<I 

<I 

<I 

<I 

<I 

<I 

<I 

<I 

1 

7 

<I 

<I 

<I 

2 

<I 

<1 

5 

<1 

<I 

<1 

<I 

7.3 

21 

32 

2I 

24 

II 

39 

64 

34 

12 

0.6 

I. I 

II 

9.1 

5.5 

5.3 

5.9 

22 

17 

1.2 

2.I 2.0 

18 4.4 

37 10 

82 IS 

130 71 

30 7.7 

19 5.6 

17 4.4 

16 4.6 

20 5.2 

66 6.9 

20 12 

0.7 1.0 

23 17 

I,700 200 

17 

76 

50 

54 

47 

12 

13 

11 

8.5 

I6 

2

Values are results from gas-scintillation counting, where extraction procedures produced values lower than the liquid scintillation method. 

0.2 

.8 

.I 

.I 

.I 

<.I 

1.4 

<.I 

.I 

.2 

12 

59 

<3 

<3 

7 

<3 

8 

<3 

7 

14 

<.I 14 

.3 

1.5 10 

.4 26 

.2 

.2 36 

<.I <3 

.I <3 

.4 79 

.2 3 

.2 32 

1.4 I6 

<.1 I20 

.6 5 

5.6 9,600 

.4 

1.7 

.4 

.9 

1.5 

5 

<3 

.5 

Dissolved 

organic 

carbon 

4.5 

.5 

.7 

.5 

.8 

.8 

4.4 

.9 

.8 

.6 

.5 

.6 

.6 

.9 

8.8 

.6 

I. I 

.5 

.4 

.7 

.4 

.8 

.5 

1.2 

2.5 

3 

.7 

2.8 

Radon222 

(pCi/l) 1 

10,000 

5,600 

480 

440 

530 

800 

760 

<IOO 

590 

380 

l,IOO 

500 

320 

2

500 

2

200 

440 

480 

350 

2

20 

780 

310 

460 

660 

1,200 

<IOO 

560 

200 

2

300 

2400 

460 
from subsurface fractures in the granitic bedrock. Most 

recharge is from spring snowmelt in the Carson Range and 

along the alluvial fans at the base of the range. Some of this 

water flows directly from the bedrock into the alluvial-fan 

aquifer. This water would likely contain an elevated 222Rn 

activity because of its intimate contact with the Cretaceous 

granitic rocks. 

Wells along the western side of the valley typically 

are artesian. Upward head gradients exist that may be 

carrying 222Rn-rich water up from depth. At the edge of the 

valley, lateral distance to bedrock is less, and bedrock 

presumably is closer to land surface, a situation that allows 

for the short-time flow paths needed to minimize 222Rn 

decay. 

The major normal fault along the eastern base of the 

Carson Range (fig. 116) separates bedrock from the basinfill sediments. This fault has a displacement exceeding 

4,000 ft and dips 36° to 60° to the east beneath the valley-fill 

sediments (Moore, 1969, p. 17). The fault zone may act as 

a conduit for deeper 222Rn-rich water from the bedrock 

aquifer to migrate up into the confined alluvial-fan unit. 

Relatively high uranium concentrations (greater than 

53 mg/kg) are present in sediments from shallow auger 

holes along the bottom of Carson Valley adjacent to the 

eastern side of the Carson Range (Otton and others, 1985, 

table 1). These sediments are rich in organic materials that 

tend to sorb dissolved uranium from the ground water. 

These sediments are young, and, thus, their 222Rngeneration potential is relatively low. Similar depositional 

processes have been dominant since late Tertiary time 

(Moore, 1969, p. 14); therefore, uranium-rich sediments 

probably are present at depth in the valley-fill sediments 

along the western side of Carson Valley. These older 

deposits may contain sufficient uranium to cause elevated 

activities of 222Rn in ground water. 

Most of the ground water in the unconsolidated 

Quaternary sedimentary aquifer in Carson Valley is dilute 

and of the sodium-calcium-bicarbonate type. Although 

most of these waters have specific conductances of less than 

500 J.l.S/cm (microsiemens per centimeter), ground water 

from one well in this study (well 25 in tables 52 and 54), 

which has been influenced by seepage from sewage-effluent 

ponds, and possibly by geothermal water, is slightly saline. 

In general, ground water is more mineralized toward Hot 

Springs Mountain in the northeast part of the valley (Garcia, 

1988). 

Water-quality relations suggest that the 222Rn is 

derived from the granitic rocks of the Carson Range. Sulfate 

and specific conductance are inversely related to 222Rn 

activities (fig. 119); that is, waters having high specific 

conductances or sulfate concentrations tend to have low 222Rn activities. No apparent relation exists between 222Rn 

activity and other water-quality constituents in ground water 

from Carson Valley. Water from springs and runoff in the 

Carson Range typically is dilute (less than 200 JLS/cm), low 

6,000 .. 'I .. a: ~ w 

~tii 

u.i~ 

~ffi 1,000 ~ ~ 1-0 ~ 

~~$~ Oa: 

=>w Oa.. 

~CJ) oz ~ ~~ w ~ ~~ 100 ~ ~ !::!:- ~ ~ - ~~ a.. a: cno 

:i 

~ 

.• •• J 10 1~0--._~~w1~0~0--~~~~1.~000~--~~~1~0.~000~ 

RADON-222 ACTIVITY, IN PICOCURIES PER LITER 

Figure 119. Relation between radon-222 and specific conductance in sampled ground water. 

in sulfate (less than 4 mg!L), of the sodium-calciumbicarbonate type (Feth and others, 1964, table 1), and 

similar to ground water on the western side of Carson 

Valley. Ground water on the eastern and northern sides of 

the valley commonly has higher specific conductance and 

sulfate concentrations (see fig. 115 and table 53) than water 

on the western side of the valley (Garcia, 1988). Apparently, water east of the major ground-water trough in the 

Carson Valley, as indicated by the slope of the piezometric 

surface, is derived largely from recharge in the Pine Nut 

Mountains (fig. 115), where Tertiary sedimentary rocks 

predominate. Although the uranium concentration of these 

rocks is unknown, the 222Rn generation potential of these 

rocks and their derived sediments probably is low, as 

reflected in the low 222Rn activities in ground water from 

the east side of the valley. 

SUMMARY 

Ground water in the unconsolidated Quaternary sedimentary aquifer of Carson Valley contains 222Rn activities 

ranging from less than 100 to 10,000 pCi/L. The median 

activity for 30 ground-water samples is 480 pCi/L. Radon222 activities are highest along the western periphery of 

Carson Valley in the alluvial-fan deposits. 

Several possible factors may contribute to elevated 222Rn activities. Cretaceous granitic rocks that have high 

uranium content, both as bedrock and alluvial detritus, may 

release 222Rn to the ground water. Significant amounts of 222Rn-enriched ground water from the fractured bedrock 

may flow into the confined alluvial-fan unit. The major 

normal fault bordering the eastern side of the Carson Range 

may function as a conduit for 222Rn-rich water from depth. 

Organic-rich sediments that are present along the western 

Radon in Ground Water of Carson Valley, West-Central Nevada 287 
side of Carson Valley contain high uranium concentrations 

and may be releasing 222Rn to the ground water. 

Relations between water quality and 222Rn activities 

indicate that the major source of 222Rn is the Carson Range. 

Radon-222 activity is related inversely to sulfate and 

specific conductance. The chemical character of 222Rn-rich 

ground water in the unconsolidated Quaternary aquifer is 

similar to that of water from the Carson Range. 

REFERENCES CITED 

Bennett, C.B., 1980, Reno 1 x 2 NTMS area, Nevada, data 

report, National Uranium Resource Evaluation Program, 

hydrogeochemical and stream sediment reconnaissance: U.S. 

Department of Energy Report DPST-79-146-15, 50 p. 

Brutsaert, W.F., Norton, S.A., Hess, C.T., and Williams, J.S., 

1981, Geologic and hydrologic factors controlling radon-222 

in ground water in Maine: Ground Water, v. 19, p. 407-417. 

Cothern, C.R., 1987, Development of regulations for radionuclides in drinking water, in Graves, B., ed., Radon, radium, 

and other radioactivity in ground water: Chelsea, Mich., 

Lewis Publishers, p. 1-11. 

Cothern, C.R., Lappenbusch, W.L., and Michel, J., 1986, 

Drinking-water contribution to natural background radiation: 

Health Physics, v. 50, p. 33-47. 

Feth, J.H., Roberson, C.E., and Polzer, W.L., 1964, Sources of 

mineral constituents in water from granitic rocks, Sierra 

Nevada, California and Nevada: U.S. Geological Survey 

Water-Supply Paper 1535-I, 70 p. 

Garcia, K.T., 1988, Ground-water quality in Douglas County, 

western Nevada: U.S. Geological Survey Water-Resources 

Investigations Report 87-4269, 107 p. 

Glancy, P.A., and Katzer, T.K., 1976, Water-resources appraisal 

of the Carson-River Basin, western Nevada: Nevada Division 

of Water Resources, Reconnaissance Report 59, 126 p. 

Horton, T.R., 1985, Nationwide occurrence of radon and other 

natural radioactivity in public water supplies: Environmental 

Protection Agency Report 520/5-85--008, 208 p. 

288 Field Studies of Radon in Rocks, Soils, and Water 

Lanctot, E.M., Tolman, A.L., and Loiselle, M., 1985, Hydrogeochemistry of radon in ground water: Eastern Regional 

Ground Water Conference, Association of Ground Water 

Scientists and Engineers, National Water Well Association, 

Worthington, Ohio, Proceedings, p. 66-85. 

Lowry, J.D., Hoxie, D.C., and Moreau, E., 1987, Extreme levels 

of 222Rn and U in a private water supply, in Graves, B., ed.; 

Radon, radium, and other radioactivity in ground water: 

Chelsea, Mich., Lewis Publishers, p. 363-375. 

Maurer, D .K., 1986, Geohydrology and simulated response to 

ground-water pumpage in Carson Valley, a river-dominated 

basin in Douglas County, Nevada, and Alpine County, 

California: U.S. Geological Survey Water-Resources 

Investigations Report 86-4328, 109 p. 

Moore, J.G., 1969, Geology and mineral deposits of Lyon, 

Douglas, and Ormsby Counties, Nevada: Nevada Bureau of 

Mines and Geology Bulletin 75, 45 p. 

Otton, J.K., Zielinski, R.A., and Been, J.M., 1985, Uranium in 

Holocene valley-fill sediments, and uranium, radon, and 

helium in waters, Lake Tahoe-Carson Range area, Nevada 

and California: U.S. Geological Survey Open-File Report 

85-389, 30 p. 

Pennington, R.W., 1980, Evaluation of empirical methods for 

estimating crop water consumptive use for selected sites in 

Nevada: Nevada Division of Water Planning, Report 3, 206 

p. 

Rush, F.E., 1968, Index of hydrographic areas in Nevada: Nevada 

Division of Water Resources Information Report 6, 38 p. 

Turner-Peterson, C.E., and Fishman, N.S., 1986, Geologic 

synthesis and genetic models for uranium mineralization in 

the Morrison Formation, Grants Uranium Region, New 

Mexico, in Turner-Peterson, C.E., Santos, E.S., and Fishman, N. S. , eds. , A basin analysis case study-The Morrison 

Formation, Grants Uranium Region, New Mexico: American 

Association of Petroleum Geologists, Studies in Geology, 

No. 22, p. 357-388. 

Walker, G.W., 1981, Uranium, thorium, and other metal 

association in silicic volcanic complexes of the northern 

Basin and Range, a preliminary report: U.S. Geological 

Survey Open-File Report 81-1290, 45 p. 
GEOCHEMISTRY OF GROUND WATER AND RADIONUCLIDE MOBILITY 

IN TWO AREAS OF THE READING PRONG, EASTERN PENNSYLVANIA 

Richard B. Wanty, Paul H. Briggs, and Linda C.S. Gundersen 

Abstract 

High levels of indoor radon-222 have been found in 

homes built on the Reading Prong, a continuous exposure 

of Proterozoic metamorphic rocks trending northeastward 

from Reading, Pa. The radon-222 is derived from radioactive decay of uranium-238, in which these rocks are 

enriched. Radon-222 is present also in the ground water in 

these fractured crystalline aquifers. Ground-water samples were taken from 31 domestic supply wells in two 

areas and were analyzed for common major and minor 

elements, as well as for total uranium, radium-226, and 

radon-222. The waters are dilute, usually less than 200 

milligrams per liter in total dissolved solids, but many of 

the water samples had high concentrations of the radionuclides. In a study area near Boyertown, Pa., measured 

pH values ranged from 5.8 to 9.0. The water quality in that 

area is determined by the aquifer rock types, which 

include hornblende gneiss and quartz-feldspar gneiss; 

some of the quartz-feldspar gneiss is mylonitized. In 

Easton, Pa., the water samples had low total dissolved 

solids and slightly acidic pH values (5.5 to 6.7). The 

dominant rock type in Easton is also quartz-feldspar 

gneiss, but one well appeared to be penetrating a local 

carbonate aquifer. 

In Boyertown, the highest radon-222 and uranium 

concentrations were in water drawn from the mylonitized 

quartz-feldspar gneiss. Dissolved radon-222 concentrations as high as 100,000 picocuries per liter and total 

uranium concentrations as high as 200 picocuries per liter 

were measured. Radium-226 concentrations ranged from 

<0.1 to 4.2 picocuries per liter but seldom exceeded 1 

picocurie per liter. In Easton, dissolved radon-222 values 

were generally higher, ranging from 6,000 to 80,000 picocuries per liter. Radium-226 concentrations also were 

higher, ranging from 0.2 to 10.1 picocuries per liter. 

Secular equilibrium between radon-222 and uranium-238 

is not attained in any of the samples from either area. In 

every case, radon-222 activity greatly exceeds that of 

uranium-238 in the water. Thus, the source of the dissolved radon-222 lies ultimately in uranium-238 in the solid 

phase. Likewise, the aqueous radium-226 activity is lower 

than that of radon-222 in every sample. Dissolved uranium 

concentrations are controlled by the oxidizing or reducing 

nature of the ground water. However, the data suggest 

that for oxidizing ground water, uranium concentrations 

are independent of major chemical parameters such as pH 

and carbonate concentration and depend on aquifer rock 

type. Waters from the mylonitized quartz-feldspar gneiss 

have a higher average uranium concentration. Reduced 

ground water, restricted to two narrow zones of hornblende gneiss within the Boyertown study area, contains 

uniformly lower uranium concentrations ( <1 picocurie 

per liter). Therefore, aquifer rock type appears to be a 

dominant factor in determining the radon-222 potential of 

ground water in the two sites studied in the Reading 

Prong. 

INTRODUCTION 

Although the issue of indoor radon and its sources has 

received considerable attention, there is still little information concerning the source of radon-222 e22Rn) dissolved 

in ground water. Most studies of 222

Rn in ground water 

have been aimed at characterizing 222Rn values for statistical or geochemical exploration purposes (Dyck and Tan, 

1978; Prichard and Gesell, 1983; Loomis, 1987) or at 

understanding the hydrologic processes governing 222Rn 

availability (Brutsaert and others, 1981; Rumbaugh, 1983; 

Wathen, 1986). Few studies have been performed in which 

specific chemical processes have been examined for the role 

they may play in controlling 222Rn availability. This paper 

presents the results of a field study designed to understand 

the source of the radionuclides uranium-238 e38U), radium226 e26Ra), and 222Rn in domestic ground-water supply 

wells from two areas in the Reading Prong physiographic 

province of eastern Pennsylvania. 

A thorough understanding of radionuclide mobility 

can be derived from a detailed examination of the overall 

ground-water quality. Therefore, major geochemical 

parameters of the ground-water samples were measured, 

including pH, dissolved oxygen, and the concentrations of 

major and trace cations and anions. A key feature of this 

study is the examination of a broad range of geochemical 

processes that affect ground-water quality as well as the 

mobility of 238U, 226Ra, and 222

Rn. Insights into the 

availability of 222Rn in ground water may be gained from 

studying these geochemical processes. A detailed summary 

of the geochemistry of the radionuclides is presented in an 

earlier paper in this volume (Wanty and Schoen, this 

volume). 

GEOLOGY AND GROUND-WATER CHEMISTRY 

OF THE STUDY AREAS 

The study was performed in two areas in the Reading 

Prong (figs. 120 and 121), near Boyertown and Easton , Pa. 

The geology of the two areas is dominated by a complex 

sequence of metamorphic rocks of varying grade and 

composition. Structural features such as folding, faulting , 

and foliation further complicate the geologic interpretation. 

Specific geologic characteristics of the two areas will be 

Geochemistry of Ground Water and Radionudide Mobility in the Reading Prong 289 
summarized briefly here; for a more detailed description of 

the geology, the reader is referred to Drake ( 1967), Gundersen and others (1988), and Gundersen (this volume). 

Rocks in the Boyertown study area (fig. 120) constitute a metasedimentary sequence including interlayered 

biotite and quartz-feldspar gneisses (QFG), and hornblendepyroxene gneisses. The more mafic gneisses contain 

relatively low amounts of uranium and may contain sulfide 

minerals such as pyrite. Ground water in the mafic gneisses 

typically has low or below-detection concentrations of 

dissolved oxygen, high iron concentrations (up to several 

parts per million), variable pH, low levels of uranium, and 

variable 222Rn concentrations. The QFG contains abundant 

uranium, sometimes in discrete grains of uraninite or in 

uraniferous minerals such as allanite, monazite, or sphene. 

The QFG has been severely mylonitized, and ground-water 

flow through this rock unit is restricted to fractures. Ground 

water in the QFG has a generally low pH (5.2-6.2), a high 

dissolved oxygen content, and high values of dissolved 

uranium and 222Rn. Weathered surfaces of the QFG 

typically are iron stained. 

The Easton study area (fig. 121) contains gneisses of 

variable composition, which represent a metasedimentary 

sequence. The rock units present in the area include 

interlayered quartz-feldspar and biotite gneisses, sillimanite 

gneiss, and marble. The QFG are enriched in uranium, 

which is contained in uraninite or other exotic uraniferous 

minerals. Limestones of the Lower and Middle Cambrian 

Leithsville Formation underlie the QFG and crop out to the 

north of them. Most of the homes in Easton are connected 

to a community water supply; only six private domestic 

wells were sampled in this area. All of the sample sites 

appear within the outcrop of the QFG on the geologic map 

(fig. 121). Ground water in the QFG generally has a low 

pH, a high dissolved oxygen content, and high uranium, 226Ra, and 222Rn contents. One of the well waters sampled 

had a higher pH (6.7), alkalinity (100 ppm (parts per 

million) HC03), and total dissolved solids (TDS; nearly 

twice the average of the other samples), all of which 

indicate a mixed origin for this water between the QFG and 

the underlying limestone. 

METHODS OF SAMPLING, ANALYSIS, AND 

DATA TREATMENT 

Samples were collected in the field from privately 

owned domestic-supply wells. Each well was pumped while 

temperature and specific conductivity were monitored. 

When these two quantities had stabilized (usually 10-20 

minutes), the sampling procedure was begun. Field 

analyses were performed for concentrations of dissolved 

oxygen and 222Rn, as well as pH, temperature, specific 

conductivity, and alkalinity. A summary of the methods 

used and detailed references for each method are listed in 

290 Field Studies of Radon in Rocks, Soils, and Water 

Figure 120. Geology of the Boyertown study area. Dots 

show the sample locations. Numbers correspond to table 

56. The light and intermediate stippled patterns represent 

various mafic gneisses. The hachured pattern near the 

center is the mylonitized quartz-feldspar gneiss unit. For a 

detailed description of the geology of the Boyertown area, 

see Gundersen and others (1988). 

table 55. In addition to the field analyses, samples were 

collected for later laboratory analysis. These samples first 

were passed through a 0.45-~J.m (micrometer) filter and then 

collected in polyethylene bottles. The samples were 

acidified to pH < 1 with concentrated nitric acid and 

returned to the laboratory for analysis of major and trace 

cations and major anions. The cations were analyzed by 

inductively coupled plasma atomic emission spectroscopy 

(Lichte and others, 1987), and the anions were analyzed by 

ion chromatography (Fishman and Pyen, 1979). The 

chemical data were entered into the program PHREEQE 

(Parkhurst and others, 1980), which was used to calculate 

the equilibrium distribution of aqueous species and to 

determine the saturation state of various phases in the 

ground water. The saturation state of the water with respect 

to a given solid phase is quantitatively expressed as the 

saturation index (SI), defined as the logarithm of the ratio of 

the ion activity product of the solid to its solubility product 

constant. Positive values of SI indicate supersaturation of a 

water with respect to the solid, negative values indicate 

undersaturation, and an SI of zero indicates equilibrium. 

For further details of the method of calculation and 

theoretical fundamentals, see Truesdell and Jones (1974) 

and Parkhurst and others (1980). 
r---> 

L::5 

/ 

/ 

/ 

/ 

/ 

/ 

/ 

/ 

/Ar:::z:J~~ 

/ 

/ 

EXPLANATION 

contact 

~fault 

Leithsville 

Formation 

_ _ approximate 

contact 

0.5 kilometer I I I I I 

N 

Figure 121. Geology of the Easton study area. Dots show 

the sample locations. Numbers correspond to table 57. All 

samples studied lie within a quartz-feldspar gneiss unit. 

For details of the geology, see Drake (1967) and Gundersen and others (1988). 

Table 55. Field methods used during ground-water 

sampling in the Reading Prong, Pa. 

Property Method Reference 

pH ............. Electrode ............. Wood, 1981. 

Conductivity ..... Conductivity bridge .... Wood, 1981. 

Alkalinity . . . . . . . . Titrimetric . . . . . . . . . . . . Skougstad and others, 

1979. 

Dissolved 0 2 . . . . . Electrode . . ........... Wood, 1981. 

Dissolved H2S . . . . Precipitation with zinc Skougstad and others, 

acetate, gravimetric 1979; Tuttle and 

determination. others, 1986. 

Dissolved 222Rn . . Degassing followed by Reimer, this volume. 

scintillometry. 

RESULTS AND DISCUSSION 

Boyertown Study Area 

The Boyertown study area provided the greatest 

number of wells, with an approximate sample density of 8 

per square kilometer. Twenty-five wells, representing 

several aquifers, were sampled in the Boyertown area; 

analytical results for the water samples are presented in 

table 56. Although the water samples were of generally 

good quality (all meet Environmental Protection Agency 

drinking water standards for TDS), many of the wells 

contain high levels of the various radionuclides. The highest 222Rn values occur in waters sampled from mylonitized 

zones within the QFG (figs. 122 and 123). 

The QFG contains anomalously high uranium, 

particularly in mylonitized zones. The residence of this 

uranium is either in discrete uranium minerals or 

incorporated in other minerals such as sphene. Uranium 

also is adsorbed onto the iron oxides on weathered surfaces. 

Ground-water samples from the QFG contained the highest 

concentrations of dissolved oxygen (fig. 124). Because 

uranium is most soluble in oxidized waters (Langmuir, 

1978), high dissolved uranium concentrations are expected 

in water from the QFG (fig. 125). Furthermore, the 

saturation indexes of uraninite, a reduced uranium solid 

(U02), are lowest in water samples drawn from this rock 

unit (fig. 126). Water samples from the hornblende gneiss 

had low uraninite SI values because those rocks contain 

much lower amounts of leachable uranium. In addition, the 

waters in the QFG had the lowest pH values observed in the 

Boyertown study area. This effect is due in part to the 

oxidation of pyrite in the rocks. The iron released to the 

solution during this oxidation reaction reprecipitates as 

ferric oxyhydroxide. The iron oxides are effective adsorbents for uranium when the ground water has pH values 

above 5 to 6 and low total carbonate concentrations (Hsi, 

1981). Qualitatively, other substrates, such as clay 

minerals, should behave similarly. In the waters that have 

the lowest pH ( <6), particularly in the mylonitized zones, 

high concentrations(> 1 ppb (part per billion)) of dissolved 

uranium are observed because adsorption reactions are less 

effective at limiting uranium mobility. Nevertheless, the 

observed uranium concentrations are still many orders of 

magnitude lower than the 222Rn concentrations. 

Radium-226 values in the Boyertown ground-water 

samples were generally low; all but one sample tested below 

1 pCi/L. The highest value (4.1 pCi/L) was found in the 

mylonitized QFG. Iron oxides are abundant on weathered 

surfaces of the QFG (whether mylonitized or not) and 

effectively adsorb the aqueous radium (Ames and others, 

1983 a,b,c). Therefore, 226Ra levels in the ground waters 

probably are limited by adsorption processes. Dissolution of 

biotite or pyrite in the rocks is a probable source for 

dissolved iron. Iron oxide minerals then precipitate as the 

aqueous Fe2

+ is oxidized to Fe3+. Calculations made by use 

of the computer programs BALANCE (Parkhurst and others, 

1982) and PHREEQE (Parkhurst and others, 1980) suggest 

that dissolution of both of these phases is necessary to 

produce the observed iron concentrations. 

The highest concentrations of 238U, 226Ra, and 222Rn 

all occur in waters drawn from the mylonitized QFG. 

However, they are not in secular equilibrium. Dissolved 222Rn concentrations are several orders of magnitude higher 

than would be expected if secular equilibrium were 

established in the ground water alone (table 56). Therefore, 

virtually all of the dissolved 222Rn is derived from 226Ra and 238U in the solid phase. It is logical to assume that the 

dominant control on 226Ra (and, to some extent, 238U) 

solubility is adsorption onto mineral surfaces at the 

Geochemistry of Ground Water and Radionuclide Mobility in the Reading Prong 291 
• >10,000 

0 

I O.Smile 

I 

0.5 kilometer 

Figure 122. Radon-222 concentrations in ground water of 

the Boyertown study area. All values are in picocuries per 

liter; actual values are listed in table 56. Patterns depict 

lithologies as in figure 120. 

aqueous-solid interface. Thus, the 222Rn concentrations in 

the ground water are unsupported by the parents in the 

water, although the parents are concentrated in the solid 

phase. The implications of this observation are extremely 

important: rocks having the highest uranium concentrations 

generally have the highest concentrations of 222Rn in the 

ground water. In order for this statement to be true, a 

portion of the solid-phase uranium must be located near the 

rock-water interface. This condition is met if the uranium 

and radium are adsorbed on mineral surfaces rather than 

bound in crystal structures. 

Although the waters themselves are not in secular 

equilibrium, the local water-rock system may be. Chemical 

evidence from rocks and soils in the Boyertown area 

suggests that this may be the case. Analyses of rock samples 

collected in Boyertown indicate that 238U and 226Ra contents are within the correct order of magnitude to support 

the observed 222Rn in the ground water (Gundersen and 

others, 1988). In support of this argument, Rumbaugh 

( 1983, 1987) successfully modeled 222Rn concentrations in 

ground water when assuming secular equilibrium in the 

local water-rock system. 

292 Field Studies of Radon in Rocks, Soils, and Water 

"' Q) 

~ 5 

Jl 

0 

Q; 4 .0 

E 

::J 

z 

g) 3 a. 

E 

l1l 

(f) 

0 2 

Q; 

.0 

E 

::J I z 

"' Q) 

a. 

E 

l1l 

(f) 

0 

Q; 

.0 

E 

::J 

z 

Hornblende Gneiss 

Quartz-Feldspar Gneiss 

Mylonite 

..______.... ........... 

10 20 30 40 50 60 70 80 90 100 

Rn (thousands of picocuries per liter) 

Figure 123. Dissolved-radon-222 concentrations in ground 

water from three aquifers in the Boyertown study area. 

Easton Study Area 

Sampling from the Easton study area was limited by 

the small number of homes having wells; most Easton 

residents are connected to a municipal water supply. Six 

wells were sampled in the area, all of which were situated 

in the same geologic unit (fig. 121). Indeed, the overall 

water chemistry is similar for these wells, with the exception of site 5. It is apparent from the ionic strength, pH, and 222Rn and bicarbonate concentrations (table 57) that well 5 

is drawing some portion of its water from the Leithsville 

Formation limestones, which underlie the main QFG body. 

Except for site 5, the Easton samples closely resemble the samples drawn from the QFG in Boyertown, and 

many of the observations and conclusions derived from the 

Boyertown QFG samples also apply to Easton. The Easton 

ground water generally is of good quality, except for the 

high radionuclide concentrations. The Easton ground water 

is characterized by high concentrations of dissolved oxygen, low pH, low TDS, and high dissolved 222Rn. As in 

Boyertown, dissolved 222Rn is almost completely unsup-
• 1-5 

• >5 

0 

I O.Smile I 

O.Skilometer 

Figure 124. Dissolved-oxygen concentration in the Boyertown ground water. All values are in parts per million, 

actual values are listed in table 56. Patterns depict lithologies as in figure 120. 

ported by dissolved 238U and 226Ra. Nevertheless, the 

rock-water system, taken as a whole, may be in secular 

equilibrium. As in the Boyertown study area, 226Ra and 238U contents of the aquifer rocks are within the right order 

of magnitude to support the dissolved 222Rn (Gundersen and 

others, 1988). 

Total uranium concentrations in the Easton ground 

waters ranged from 0.5 to 14 ppb (table 57). Radium-226 

concentrations ranged from 0.2 to 10.1 pCi/L. Uranium238 and 226Ra approach secular equilibrium in some cases, 

although this is probably fortuitous. Uraninite is extremely 

undersaturated in every sample from the Easton area (maximum uraninite SI value is -7.1; most are less than - 23). 

Therefore, reduced uranium solids do not control the 

mobility of uranium in this ground water. Similarly, no 

radium solids approach saturation in these waters. Two 

processes may limit 238U and 226Ra concentrations in these 

waters: slow kinetics of dissolution of uranium and radium 

minerals, or, more likely, the adsorption of both elements 

onto various aquifer materials. Iron oxides and quartz 

probably provide the majority of adsorption sites. Iron 

oxides are less abundant but more effective adsorbents (Hsi, 

1981; Ames and others, 1983a,b,c). Quartz, although a 

weak adsorbent, is much more abundant in the rock. On the 

other hand, 222Rn is weakly adsorbed onto mineral surfaces, 

• 1-10 

• >10 

0 O.Smile 

1-l------'' 0.5 kilometer 

Figure 125. Dissolved-uranium concentration in the 

Boyertown ground water. All values are in parts per 

million, actual values are listed in table 56. Patterns depict 

lithologies as in figure 120. 

if at all. Thus, radon is partitioned into the aqueous phase, 

and its concentration is high relative to that which would be 

expected if the water itself were in secular equilibrium. 

CONCLUSIONS 

Radionuclide concentrations in ground waters from 

crystalline aquifers in two sites in eastern Pennsylvania are 

controlled primarily by aquifer lithology. Within the geologic framework, specific chemical processes, including 

adsorption/desorption and mineral dissolution and precipitation, act to control the concentrations of the individual 

elements. Weathering reactions that take place during 

recharge of oxygenated ground waters include pyrite oxidation and dissolution of uranium-bearing minerals. Iron 

released during pyrite oxidation later reprecipitates as a 

ferric oxyhydroxide. This ferric oxyhydroxide is an effective adsorbent for 238U and 226Ra. Uranium concentrations 

are highest in oxidizing ground water but only in rocks that 

contain leachable uranium. For the Boyertown and Easton 

study areas, the highest dissolved uranium concentrations 

occur in uraniferous QFG. Mylonitized areas within the 

QFG are enriched in uranium over the surrounding rocks, 

and waters in this aquifer have particularly high dissolved 222Rn concentrations. Radium-226 concentrations are highest in low-pH ground waters, where adsorption onto minGeochemistry of Ground Water and Radionuclide Mobility in the Reading Prong 293 
t>J 

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=E 

a 

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Table 56. Chemical analyses of the Boyertown study area well waters 

[Units are as follows: Temp., temperature in degrees Celsius; SpC, specific conductance in micromhos per centimeter; DO (dissolved oxygen), TDS (total dissolved solids), SO 4 , HC03 , Cl, Ca, Mg, Na, 

K, Si, and Fe, all in parts per million; Rn, Ra, both in picocuries per liter; U, B, Mn, Cu, Zn, Li, Ba, Sr, and Cr, all in parts per billion. Rock type: QFG, quartz-feldspar gneiss; HG, hornblende gneiss; 

and My, mylonitized quartz-feldspar gneiss. na, not analyzed; nd, not detected] 

Site no. Rock type Temp. SpC DO pH Rn Ra u TDS 504 HC03 Cl Ca 

I ....... . 

2 .... . . . . 

3 ....... . 

4 .. ... .. . 

5 .. ..... . 

6 ....... . 

7 ....... . 

8 ....... . 

9 ....... . 

10 ....... . 

II ....... . 

I2 ....... . 

I3 .. . .... . 

14 ...... . . 

15 ....... . 

16 ....... . 

17 ....... . 

18 ..... .. . 

19 ....... . 

20 ....... . 

21 ....... . 

22 ....... . 

23 ....... . 

24 ....... . 

25 ....... . 

26 ....... . 

27 ....... . 

QFG 

QFG 

HG 

QFG 

HG 

HG 

HG 

HG 

HG 

QFG 

QFG 

My 

My 

HG 

QFG 

QFG 

HG 

HG 

QFG 

My 

My 

My 

My 

QFG 

HG 

QFG 

QFG 

13.6 

13 

12 

13 

12.4 

12 

13.3 

13.7 

12.3 

13 

12 

13.5 

13.6 

12.4 

13 

13.7 

13.1 

13.1 

13.9 

13.5 

13.4 

13.1 

13.1 

na 

I2.1 

13.1 

I2.3 

na na 

190 9.2 

360 .3 

240 5.5 

310 .3 

222 .22 

336 .3 

280 .I 

200 2.9 

258 4.8 

180 8.1 

201 8.4 

300 9.3 

370 3.6 

282 7.6 

280 8.7 

240 .69 

185 .79 

170 6.8 

130 11.1 

235 3.6 

262 .08 

182 7.8 

na na 

285 3.5 

280 2.3 

I45 9.8 

5.95 4,300 na 

6.05 3,900 .2 

6.75 100 .2 

6.3 16,600 .2 

6.65 I ,200 .2 

6.45 670 .2 

7.9 120 .I 

8.95 1,400 

6.05 1,200 

6.65 3,700 

6.15 5,500 

6.05 41,000 

5.95 34,000 

6.65 II, 100 

5.95 8,200 

5.85 6,300 

.I 

.I 

. I 

.2 

.3 

.5 

.2 

.I 

.2 

.3 

.I 

.3 

.2 

.6 

na na 

.18 112 

.36 214 

6 159 

0 200 

.18 164 

.14 216 

.18 

0 

.33 

.33 

6.55 

167 

II7 

I94 

107 

Il2 

4.59 127 

2.06 2I4 

.14 137 

.48 178 

3.48 

1.82 

.67 

197 

164 

132 

1.18 IOI 

58 I87 

7.65 28,800 

8.55 13,400 

6.65 26,300 

6.1 12,000 

6.65 99,000 

7.65 71,900 

5.95 39,600 

4.1 590 203 

.4 3.6 113 

na 14,200 na 

6.35 100 . I 

6.65 I ,400 .2 

6.05 II ,300 .I 

na 

.21 

.33 

.05 

na 

205 

185 

106 

na 

32 

59 

43 

50 

46 

50 

16 

31 

52 

25 

36 

3I 

49 

53 

44 

44 

38 

36 

33 

42 

45 

30 

na 

57 

54 

35 

na 

38 

89 

57 

84 

63 

97 

95 

43 

79 

40 

35 

19 

98 

34 

35 

94 

70 

52 

29 

68 

85 

29 

na 

62 

62 

32 

na na 

nd 11.9 

nd 28.2 

10 21.4 

nd 20.1 

nd 19.6 

nd 30.8 

nd 4.16 

nd I3.5 

nd 35.7 

nd 12.2 

nd I3.2 

30 17.9 

nd 31.4 

nd 15.8 

35 23.2 

nd 28 . 1 

nd 9.28 

nd 15.5 

nd 12.2 

20 27.5 

15 31 .7 

I5 I6 

na na 

15 33.6 

10 23.3 

nd 12.5 

Mg Na K Si 

na na na na 

5 7.3 nd I7.8 

IO.I 8.2 I I6.4 

7.03 6.3 nd 14.2 

9.46 7.4 nd 20.I 

7.09 6.1 I I8.2 

8.13 9.1 I 19.8 

.48 40.6 nd Il.I 

6.83 5.I nd I7.1 

6.82 5.7 I I3.5 

4.59 5.7 nd I9.4 

6.22 7.9 nd 14 

8.13 9.6 I 10.1 

9.73 8.6 nd I7 

8.82 9.4 nd 16.4 

10.4 I3.1 I 15.8 

8.42 7.6 nd I4.8 

1.24 29 nd 16.3 

4.63 5.6 nd I7.8 

4.46 7.3 nd 14.9 

8.89 9.1 nd 12 

7.28 8.4 nd 10.6 

6.77 7.2 I 8.03 

na na na na 

10.6 8.8 2 16.3 

10.8 7.9 I I5.7 

4.44 6.1 nd 16.4 

B Fe Mn Cu Zn Li Ba Sr Cr 

na na na na 

nd .02 nd nd 

40 1.73 I15 nd 

30 .02 7 nd 

80 9 103 nd 

nd 3.24 

90 .07 

130 nd 

nd .63 

nd nd 

nd .04 

nd .02 

10 nd 

10 nd 

nd nd 

30 .02 

40 nd 

100 nd 

220 .07 

10 .05 

80 nd 

80 .18 

10 nd 

na na 

nd nd 

10 .04 

10 .05 

77 nd 

98 nd 

4 nd 

23 IO 

nd nd 

I nd 

nd nd 

nd 10 

46 nd 

nd nd 

2 nd 

5 nd 

nd nd 

I3 nd 

nd 20 

12 nd 

85 nd 

3 10 

na 

188 nd 

20 10 

2 nd 

na na na na na 

I3 4 129 67.9 2 

8 7 93 7I.I 

7 nd 2 62.6 

26 9 14 55 

15 6 32 47.6 

nd 5 10 II6 

nd 5 

42 nd 

5 nd 

6 nd 

5 nd 

147 nd 

10 5 

10 5 

10 5 

5 4 

nd 6 

I2 nd 

6 nd 

1,800 5 

624 5 

20 nd 

na na 

I4 nd 

53 5 

12 nd 

nd 20.7 

14 51.5 

I4 IIO I 

nd 40.9 2 

nd 51.4 

nd 82.2 nd 

7 63.9 I 

16 67.7 

4 110 

62 105 

nd 59.2 

4 74.6 I 

nd 64.4 2 

nd 83.7 

2 48.1 

nd 82.8 2 

na na na 

2I I38 

22 72.3 

nd 45.5 
• <·10 

• 0>X>·10 

• >0 

0 

I 0.5mile I 

0.5kilometer 

Figure 126. Uraninite saturation indexes for the Boyertown ground-water samples. Positive values indicate 

supersaturation with respect to uraninite, and negative 

values represent undersaturation. Actual values are listed 

in table 56. Patterns depict lithologies as in figure 120. 

erals such as iron oxides and quartz is weakest. Groundwater concentrations of 222Rn are much higher than 

expected, given the relatively low dissolved-238U and 

dissolved-226Ra concentrations. Uranium-238 and 226Ra 

concentrations of the aquifer materials are high enough to 

support the dissolved 222Rn concentrations. Therefore, 

although the waters themselves are not found to be in 

secular equilibrium, the overall water-rock system may be. 

Specific chemical processes are active in every aquifer at the rock-water interface. Chemically, each phase 

impacts the others in some way. These processes are 

predictable from the basis of thermodynamics and kinetics. 

A detailed examination of these processes should lead to a 

better understanding of the overall water-rock system. 

ACKNOWLEDGMENT 

We would like to thank Susan L. Johnson for assistance with the field sampling. 

(/') 

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Geochemistry of Ground Water and Radionuclide Mobility in the Reading Prong 295 
REFERENCES CITED 

Ames, L.L., McGarrah, J.E., and Walker, B.A., 1983a, Sorption 

of trace constituents from aqueous solutions onto secondary 

minerals, II. Radium: Clays and Clay Minerals, v. 31, p. 

335-342. 

---1983b, Sorption of uranium and radium by biotite, 

muscovite, and phlogopite: Clays and Clay Minerals, v. 31, 

p. 343-351. 

Ames, L.L., McGarrah, J.E., Walker, B.A., and Salter, P.F., 

1983c, Uranium and radium sorption on amorphous ferric 

oxyhydroxide: Chemical Geology, v. 40, p. 135-148. 

Brutsaert, W.F., Norton, S.A., Hess, C.T., and Williams, J.S., 

1981, Geologic and hydrologic factors controlling radon-222 

in ground water in Maine: Ground Water, v. 19, no. 4, p. 

407-417. 

Drake, A.A., 1967, Geologic map of the Easton quadrangle, New 

Jersey-Pennsylvania: U.S. Geological Survey Geologic 

Quadrangle Map GQ-594, scale 1:24,000. 

Dyck, W., and Tan, B., 1978, Seasonal variations of helium, 

radon, and uranium in lake waters near the Key Lake uranium 

deposit, Saskatchewan: Journal of Geochemical Exploration, 

V. 10, p. 153-167. 

Fishman, M.J., and Pyen, G., 1979, Determination of selected 

anions in water by ion chromatography: U.S. Geological 

Survey Water-Resources Investigations Report 79-101, 30 p. 

Gundersen, L.C.S., Reimer, G.M., and Agard, S.S., 1988, The 

correlation between geology, radon in soil gas, and indoor 

radon in the Reading Prong, in Marikos, M., ed., 

Proceedings of the GEORAD Conference: Geological Causes 

of Radionuclide Anomalies: Missouri Department of Natural 

Resources Special Publication No. 4, p. 91-102. 

Hsi, C.-K. D., 1981, Sorption of uranium(VI) by iron oxides: 

Unpublished Ph.D. thesis, The Colorado School of Mines, 

154 p. 

Langmuir,D., 1978, Uranium solution-mineral equilibria at low 

temperatures with applications to sedimentary ore deposits: 

Geochimica et Cosmochimica Acta, v. 42, p. 547-569. 

Lichte, F.E., Golightly, D.W., and Lamothe, P.J., 1987, 

Inductively coupled plasma-atomic emission spectrometry, in 

Baedecker, P.A., ed., Methods for geochemical analysis: 

U.S. Geological Survey Bulletin 1770, p. B1-B10. 

296 Field Studies of Radon in Rocks, Soils, and Water 

Loomis, D.P., 1987, Radon-222 concentration and aquifer lithology in North Carolina: Ground Water Monitoring Review, 

Spring, p. 33-39. 

Parkhurst, D.L., Thorstenson, D.C., and Plummer, L.N., 1980, 

PHREEQE-A computer program for geochemical 

calculations: U.S . Geological Survey Water-Resources 

Investigations 80-96, 210 p. 

---1982, BALANCE-A computer program for calculating 

mass transfer for geochemical reactions in ground water: 

U.S. Geological Survey Water-Resources Investigations 

82-14, 29 p. 

Prichard, H.M., and Gesell, T.F., 1983, Radon-222 in municipal 

supplies in the central United States: Health Physics, v. 45, p. 

991-993. 

Rumbaugh, J.O., III, 1983, Effect of fracture permeability on 

radon-222 concentration in ground water of the Reading 

Prong, Pennsylvania: Unpublished M.Sc. thesis, The 

Pennsylvania State University, 111 p. 

---1987, Effect of aquifer transmissivity on radon-222 

concentration of groundwater of the Reading Prong, 

Pennsylvania [abs.]: Geological Society of America 

Abstracts with Programs, v. 19, no. 2, p. 127. 

Skougstad, M.W., Fishman, M.J., Friedman, L.C., Erdmann, 

D.E., and Duncan, S.S., 1979, Methods for determination of 

inorganic substances in water and fluvial sediments: U.S. 

Geological Survey Techniques of Water-Resources 

Investigations, Book 5, Chap. A1, 626 p. 

Truesdell, A.H., and Jones, B.F., 1974, WATEQ, a computer 

program for calculating chemical equilibria of natural waters: 

J oumal of Research of the U.S. Geological Survey, v. 2, no. 

2, p. 233-248. 

Tuttle, M.L., Goldhaber, M.B., and Williamson, D.L., 1986, An 

analytical scheme for determining forms of sulphur in oil 

shales and associated rocks: Talanta, v. 33, no. 12, p. 

953-961. 

Wathen, J.B., 1986, Factors affecting levels of Rn-222 in wells 

drilled into two-mica granites in Maine and New Hampshire: 

Unpublished M.Sc. thesis, University of New Hampshire, 97 

p. 

Wood, W.W., 1981 Guidelines for collection and field analysis of 

ground-water samples for selected unstable constituents: U.S. 

Geological Survey Techniques of Water-Resources 

Investigations, Book 1, Chap. D2, 24 p. 
RADIONUCLIDES IN THE PUERCO AND LOWER UTILE COLORADO RIVER BASINS, 

NEW MEXICO AND ARIZONA, BEFORE 1987 

John R. Gray and Robert H. Webb 

Abstract 

Radionuclides in the Little Colorado River and tributaries have several sources in the Little Colorado River 

basin of Arizona and New Mexico. Naturally occurring 

radionuclides of the uranium-238 and thorium-232 decay 

series enter the hydrologic cycle through natural erosion. 

Uranium-mining operations in two areas of the basinthe Grants Mineral Belt of New Mexico and the Cameron 

Uranium Mining Belt of Arizona-also resulted in releases 

of radionuclides. A cumulative 22 years of mine dewatering between 1960 and 1986 from the Grants Mineral Belt 

upstream from Gallup, N. Mex., and a tailings-pond spill 

in 1979 resulted in releases of radionuclides to the Puerco 

River. Mine pits left open from wildcat operations in the 

1950's and early 1960's in the Cameron Uranium Mining 

Belt now contain water that has elevated activities of 

radionuclides. The impact of mining on contamination of 

water resources of the region, however, is not well understood. 

In Arizona, surface water in the Puerco River at 

Chambers and the Little Colorado River at Cameron typically contains total gross alpha plus gross beta activities of 

several thousand picocuries per liter, or about 2 orders of 

magnitude larger than Arizona's maximum allowable limit 

of 30 picocuries per liter for surface water. Gross alpha 

plus gross beta activities in streamflow at both stations are 

associated primarily with the suspended phase. Measured 

radionuclides include large activities of uranium, thorium, 

radium, and lead-210. 

In December 1986, water from 5 of 14 wells that 

penetrate the alluvium adjacent to the Puerco River contained gross alpha minus uranium and radon activities 

equal to or greater than the Environmental Pro.tection 

Agency's maximum contaminant level of 15 picocuries per 

liter for drinking water. Water samples from several wells, 

springs, and open pits near Cameron, Ariz., contain 

activities of gross alpha plus gross beta in excess of 30 

picocuries per liter. If a "plume" of radionuclide-rich 

water exists in the alluvial aquifer underlying the Puerco 

or lower Little Colorado River, its areal extent cannot be 

determined from the data. 

The presence and extent of radionuclide activities in 

the Little Colorado River basin are generally unknown. A 

lack of understanding of processes of radionuclide movement in and between surface water and ground water 

presently limits assessments of trends in radionuclide 

contamination. 

INTRODUCTION 

Mining activities in the Little Colorado River basin of 

Arizona and New Mexico have resulted in the dispersion of 

radionuclides and other potentially hazardous trace elements to the environment. Inhabitants of the sparsely 

populated drainage basin, which is largely on the Navajo 

Indian Reservation, rely on ground water for domestic 

supplies and on surface water for livestock watering and 

irrigation of forage crops. 

This paper describes the occurrence of selected radionuclides in the Puerco and lower Little Colorado Rivers and 

in near-channel alluvial ground water in the Puerco River 

basin. The history and impacts of mining on selected water 

resources in this semiarid region are briefly described, and 

chemical and physical processes that probably control 

contaminant movement in surface water and ground water 

are reviewed. 

BACKGROUND 

The Little Colorado River basin covers 27,000 mi2 

(square miles) of the southern Colorado Plateau physiographic province. Eighty percent of the drainage area is in 

northeastern Arizona, and 20 percent is in northwestern New 

Mexico (fig. 127). The Little Colorado River heads in the 

White Mountains of east-central Arizona and descends 

6,300 ft over 356 mi before joining the Colorado River at 

Grand Canyon National Park. 

·In 1975, the' population of the Little Colorado River 

basin averaged six people per square mile. Principal communities are Flagstaff, Winslow, and Holbrook in Arizona 

and Gallup in New Mexico. The Navajo and Hopi Indian 

Reservations occupy most of the northern half of the basin 

(fig. 127). 

The climate is arid in the lower elevations and 

semiarid to subhumid in the uplands. Data from the U.S. 

Soil Conservation Service (1981, Appendix 1, p. 1-2) 

indicate that mean annual precipitation in the basin ranges 

from less than 8 in near Cameron, Ariz., to as much as 32 

in at the basin divide south of Winslow, Ariz. Daily average 

temperatures in the basin range from 26 to 80 op. Surface 

altitudes range from 12,630 ft to about 2,730 ft above mean 

sea level. The Little Colorado River is an ephemeral stream 

except for about 20 mi in its headwaters, where flow is 

regulated, and within about 10 mi of its mouth (Loughlin, 

1983). Peak runoff typically occurs in March and April 

from snowmelt and rainfall or in July and August from 

thunderstorms (U.S. Soil Conservation Service, 1981, 

Appendix 1, p. 1-2; Appendix 2, p. 5-13). 

The Puerco River basin includes about 3,000 mi2 of 

the northeastern part of the Little Colorado River basin 

(figs. 128 and 129). The Puerco River originates in the 

Radionuclides in the Puerco and Lower Little Colorado River Basins, New Mexico and Arizona 297 
c 

• 

Ill NAVAJO TRIBAL TRUST LAND (NEW LANDS) 

Figure 127. Little Colorado River basin. 

Chuska and Zuni Mountains of New Mexico and flows 

southwest about 140 mi to join the Little Colorado River 

near Holbrook, Ariz. Peak runoff in the Puerco River 

usually occurs in response to summer thunderstorms that 

produce flash floods. Before 1950, the Puerco River was an 

ephemeral alluvial stream (Kaufmann and others, 1976). 

For most of the period between the 1950's and the mid1980's, streamflow in the upper part of the basin (fig. 128) 

changed from ephemeral to perennial from near Church 

Rock, N. Mex., to downstream from the State line of 

Arizona and New Mexico. The principal sources of perennial streamflow were effluent from dewatering of uranium 

mines northeast of Gallup, N. Mex. , and effluent discharged from the sewage-treatment plant in Gallup. In the 

absence of runoff, all effluent typically infiltrated the 

298 Field Studies of Radon in Rocks, Soils, and Water 

25 50 KILOMETERS 

alluvium within a few miles downstream from Chambers, 

Ariz. (Shuey, 1986). 

Geology 

The Little Colorado River basin is geologically complex, and the regional stratigraphic sequence of sedimentary 

rocks is structurally deformed. Bedrock exposed in the 

basin ranges in age from Precambrian to Quaternary 

although exposures of Precambrian and Cambrian rocks are 

limited. Rocks of Cretaceous age, which include outcrops 

of Dakota Sandstone and Mancos Shale, are the most 

extensive and are the thickest sequence of any rock formations in the New Mexico part of the basin. Extensive 

volcanic activity began in the Tertiary Period and continued 
... 

• 

• 

EXPLANATION 

EXISTING GAGING STATION 

PROPOSED GAGING STATION 

SURFACE-WATER SITE WHERE HIGH ACTIVITIES OF RAOIONUCliOES HAVE BEEN MEASURED 

WELL WHERE GROSS ALPHA MINUS URANIUM ACTIVITIES HAVE BEEN MEASURED AT OR ABOVE ARIZONA'S MAXIMUM CONTAMINANT LEVElS IN DECEMBER 1986 

NAVAJO TRIBAL TRUST LAND (NEW LANDS) 

NAVAJO 

INDIAN . 

RESERVATI~~/ 

Petrified Forest 

National Park • 

-·-·-·-.-.~: 

/ L __ l 

Jso- •• co Ci· .• · 

\~~~~-r-l city •·• • • \r j Holbrook •• "{ J- /• 

• ~ r·J~ •• / /• L 

Wood ~ff 

···'-· 

Figure 128. Puerco River basin. 

0 

I 

0 

I I I I I 

25 

25 

well into the Quaternary Period. Volcanic rocks include 

rhyolite, dacite, andesite, and latite. Quaternary sediments 

consisting of sand, silt, and gravel are present throughout 

most of the basin (U.S. Soil Conservation Service, 1981, 

Appendix 1, p. 1-11 to 1-15). 

A large variety of ore deposits occurs in the Little 

Colorado River basin. Uranium, coal, bentonite, vanadium, 

sand, and gravel are commercially important deposits in the 

basin. In Arizona, uranium is found principally in sandstones and conglomerates of continental origin near Cameron, Chinle, and Round Rock (U.S. Soil Conservation 

Service, 1981, Appendix 1, p. 1-15 to 1-18). 

The bedrock in the Puerco River basin consists of 

Paleozoic and Mesozoic sedimentary rocks that dip slightly 

to the northeast. Steeply dipping fault zones that trend north 

and south displace these rocks. The Defiance and Zuni 

Uplifts occur to the north and east, respectively (Cooley and 

others, 1969). Rocks of Tertiary and Quaternary age, 

including the Tertiary Bidahochi Formation, generally are 

undeformed. Major uranium deposits and minor coal deposI 

50 MILES I 

INDEX MAP SHOWING AREA OF REPORT (SHAD ED) 

50 KILOMETERS 

its are present in the Jurassic Morrison Formation to the east 

and northwest of Gallup (Hackman and Olson, 1977). 

Uranium deposits also occur in the Petrified Forest Member 

of the Triassic Chinle Formation in the western half of the 

Puerco River basin. Chemical and physical weathering of 

exposed bedrock that contains uranium and other radionuclides is the source for background radiation in the regional 

water resources and sediments (Weimer and others, 1981). 

The alluvial aquifer of the Puerco River consists of 

interbedded gravel, sand, silt, and clay (Mann and Nemecek, 1983). The thickness of the aquifer is unknown, but 

several wells in the alluvial aquifer are 200 ft deep and do 

not encounter bedrock. The stratigraphy and variability of 

the sediments that compose the alluvial aquifer in the Little 

Colorado River basin are unknown. 

Standards for Radionuclides in Water 

Webb and others ( 1987b) list maximum contaminant 

levels (MCL's) and maximum allowable limits (MAL's) 

Radionuclides in the Puerco and Lower Little Colorado River Basins, New Mexico and Arizona 299 
Figure 129. Aerial view of the Puerco River basin. The Puerco River is an ephemeral stream in northeastern 

Arizona and northwestern New Mexico that has been contaminated by radionuclides and other trace elements. 

The contaminants are sorbed mostly in channel sediments. 

applicable for radionuclides in Arizona ground water and 

surface water, respectively. The amount of radium-226 

e26Ra) in water supplies forms a basis for monitoring 

natural radionuclides in drinking-water supplies in the 

United States (Lappenbusch and Cothern, 1985). The MCL 

is 5.0 pCi/L (picocuries per liter) for total 226Ra plus 228Ra. 

Total 226Ra plus 228Ra are the only natural radionuclides 

that have MCL's (McClennan, 1984; Environmental Protection Agency, 1986). The MCL for gross alpha activity 

minus uranium and radon is 15 pCi/L, and the MCL for 

total gross beta activity is 50 pCi/L. Although an MCL has 

not been established for uranium, 35 J.Lg/L (micrograms per 

liter) of uranium is a recommended limit (Lappenbusch and 

Cothern, 1985). State of Arizona regulations (State of 

Arizona Atomic Energy Commission, 1977) also mandate 

an MCL of 30 pCi/L if the identity or activity of any 

radionuclide in a mixture of radionuclides in water is 

unknown. 

The MAL for both dissolved 226Ra and dissolved 228Ra is 30 pCi/L. However, the MAL for total 226Ra plus 228Ra is 5 pCi/L. Other MAL's include 45 pCi/L for 

300 Field Studies of Radon in Rocks, Soils, and Water 

dissolved plus suspended uranium and 30 pCi/L for gross 

alpha plus gross beta activity (McClennan, 1986). 

History of Radionudide Releases 

Grants Mineral Belt, Puerco River Basin 

Effluent from dewatering of uranium mines was 

discharged to Pipeline Arroyo, a tributary of the Puerco 

River northeast of Gallup, from 1960 to 1961 and 1967 to 

1986 (Perkins and Goad, 1980). Effluent discharges contributed radionuclides to the Puerco River; however, the 

amount of radionuclides in effluent water from mining 

activities before 1967 is unknown. 

Permits under the National Pollutant Discharge Elimination System (NPDES) were required when the mines 

reopened in 1969 in an attempt to control the level of 

radioactive material in effluent water (Environmental Protection Agency, 197 5). Under the conditions of the permits, 

effluent water could contain as much as 3 pCi/L of 

dissolved 226Ra, as much as 10 pCi/L of total 226Ra, and as 
Figure 130. Church Rock tailing pond. The Church Rock 

Mill was the site of the largest accidental release of 

uranium tailings liquid in United States history. In July 

1979, approximately 94 million gallons of liquid and more 

than 1,100 tons of tailings were released into the Puerco 

much as 2.0 mg/L of total uranium (Chris Shuey, Southwest 

Research and Information Center, Albuquerque, N. Mex., 

written commun., 1987). Shuey (1986) reported 63 violations of the NPDES permits between 1980 and 1983. 

Additional discharges of radionuclides into the 

Puerco River resulted from a tailings-pond dam failure at 

the United Nuclear Corporation's Church Rock Mill on July 

16, 1979 (fig. 130) (Weimer and others, 1981; Shuey, 

1982; Millard and others, 1984). An estimated 94 Mgal 

(million gallons) of liquid were released into the Puerco 

River (Weimer and others, 1981). The liquid contained an 

estimated 18,000 tons of suspended sediment in addition to 

1, 100 tons of tailings eroded from the bottom of the tailings 

pond (Donald Hendricks, Environmental Protection 

Agency, written commun., 1982). The total amount that 

entered the Puerco River is probably less than these 

amounts because of retention of sediments behind an 

emergency catchment dam and postspill cleanup efforts 

(Weimer and others, 1981). A liquid sample taken from the 

tailings pond before the spill had total activities of 210 

pCi/L of 226Ra and 10,225 pCi/L of thorium-230 e30Th). 

River. The total activity of gross alpha in the Puerco River 

on the day of the spill was about 130,000 picocuries per 

liter. The recommended limit of gross alpha in Arizona 

surface water is 30 picocuries per liter. 

The pH of the liquid was 1. 9, and the concentration of 

uranium was about 4 mg/L (Weimer and others, 1981). 

The mines continued to discharge effluents as 

allowed under the NPDES permits after the spill of 1979. 

Activities of gross alpha and 226Ra were as large as 400 and 

2.5 pCi/L, respectively, in two samples from New Mexico 

measured in October 1981 (B.M. Gallaher, New Mexico 

Environmental Improvement Division, written commun., 

1982). Activities of lead-210 e10Pb) and polonium-210 

e10Po) ranged from 4.5 to 10 pCi/L, and 3.4 to 10 pCi/L, 

respectively, and activity of 230Th ranged from 0.1 to 3. 9 

pCi/L (B.M. Gallaher, written commun., 1982). Treated 

mine water that was released into the Puerco River had 

gross beta activities that ranged from 320 to 660 pCi/L in 

1982 (Shuey, Southwest Research and Information Center, 

written commun., 1987). Effluent from one mine contained 

total uranium concentrations that ranged from 1. 5 to 2. 7 

mg/L and a mean total concentration of 1.6 mg/L during 9 

months of 1982 (June Buzzell, Environmental Protection 

Agency, written commun., 1983). 

Radionuclides in the Puerco and Lower Little Colorado River Basins, New Mexico and Arizona 301 
Cameron U rani urn Mining Belt, lower little Colorado River 

Basin 

Most uranium ore in the lower Little Colorado River 

basin came from the Cameron Uranium Mining Belt (fig. 

127). Uranium mining occurred within a curved belt 

approximately 2 mi wide extending 6 mi north of Cameron 

along U.S. Highways 89 and 164, and 5 mi wide extending 

18 mi southeast along the Little Colorado River (Don 

Payne, Navajo Nation, written commun., 1987). Mining in 

this region began in the early 1950's, reached a production 

peak in 1957, and ceased in 1962. A total of 289,300 tons 

of spoil and more than 600 tons of uranium ore were 

extracted from 98 mining sites. Most ore was processed at 

Rare Metals near Moenkopi Wash (fig. 127; Don Payne, 

Navajo Nation, written commun., 1987). 

No regulations for stabilization of abandoned mines 

existed in 1962. As a result, many pits in the Cameron 

Uranium Mining Belt are open and have filled with water. 

Don Payne (Navajo Nation, written commun., 1987) collected water samples from 21 uranium mining pits, 14 

developed springs, 6 wells, 6 surface-water impoundments, 

and 2 other locations on the Little Colorado River in the 

mid-1980's and found elevated activities of gross alpha, 

gross beta, 226Ra, and uranium. 

Water-Quality Investigations Related to 

Radionuclide Releases 

Puerco River Basin 

Surface water in the Puerco River contained elevated 

concentrations of radionuclides and trace elements in the 

mid-1970's. In two samples taken at the State line of 

Arizona and New Mexico, one in 1975 and the other in 

1976, gross alpha activities were 330 and 100 pCi/L, and 

gross beta activities were 1,640 and 81 pCi/L, respectively 

(W.J. Shelley, Kerr-McGee Nuclear Corporation, written 

commun., 1979). Between 1975 and May 1979, 226Ra 

activities ranged from 0.1 to 22 pCi/L, and total uranium 

concentrations ranged from 0.2 to 0.9 mg/L. 

The effect of discharges allowed under the NPDES 

permits and discharges in violation of permits on the quality 

of ground water in the Puerco River basin is unknown. Scott 

and Barker (1962) report median values of 0.008 mg/L for 

uranium and 0.1 pCi/L for radium in ground water in a 

region that includes the Puerco River basin. Kaufmann and 

others (1976) studied ground-water contamination near 

uranium mines and milling operations in the Puerco River 

basin upstream from Gallup (fig. 128). In 71 ground-water 

samples that Kaufmann and others (1976) collected near 

uranium mines throughout northwestern New Mexico, only 

6 wells had activities of 226Ra above 3.0 pCi/L. Gross alpha 

activities exceeded 15 pCi/L in water from 33 of 71 wells 

(Kaufmann and others, 1976). Although radionuclide activ302 Field Studies of Radon in Rocks, Soils, and Water 

tttes in some of the samples are above current MCL's, 

Kaufmann and others (1976) concluded that none of the 13 

wells sampled in the Puerco River basin were contaminated 

by radionuclides. 

Water and sediments were sampled extensively 

throughout the Puerco River basin after the tailings-pond 

spill of 1979. Activities of 230Th in sediments commonly 

exceeded 30 pCi/g as far as 40 mi downstream from the 

mine (Weimer and others, 1981). After the spill of 1979, 230Th activity in sediments decreased with time to an 

average of 9 pCi/g in the same reach (Millard and others, 

1984). In 1979, sediments collected from the Puerco River 

in Arizona at Chambers and Petrified Forest National Park 

(fig. 128) had activities of 230Th between 1 and 8 pCi/g 

(E.K. Swanson, Arizona Department of Health Services, 

written commun., 1986). Webb and others (1987a) measured radionuclide activities equivalent to background 

activities in bed sediments collected from five sites along 

the Puerco River in December 1986. 

On July 16, 1979, following the tailings-pond spill, 

radionuclide activities in unfiltered samples from the Puerco 

River were 6,910 pCi/L of uranium, 12,000 pCi/L of 230Th, 

1.0 pCi/L of 226Ra, 260 pCi/L of 210Pb, and 38 pCi/L of 210Po at sites in New Mexico (Millard and others, 1984). 

The maximum gross alpha activity was 130,000 pCi/L on 

the day of the spill near the Church Rock Mill and 26,000 

to 40,000 pCi/L at Gallup (Shuey, 1982). 

After the spill of 1979, shallow wells in the alluvial 

aquifer of the Puerco River were monitored in New Mexico 

and Arizona. Wells in New Mexico near the Puerco River 

revealed some contamination by radionuclides (Gallaher 

and Cary, 1986). Gross alpha activity increased from a 

prespill average of 12 pCi/L to a postspill maximum of 304 

pCi/L with concomitant increases in the concentrations of 

total uranium (Shuey, 1982). Increases in gross alpha, 

uranium, and sulfate also occurred in alluvial well water in 

Arizona (Shuey, 1982). 

Since 1979, radionuclides and trace elements have 

been sampled sporadically in surface water of the Puerco 

River at Chambers (Webb and others, 1987a). Total gross 

alpha activities have fluctuated between 12 and 11,200 

pCi/L between 1979 and 1985 in the Puerco River at 

Chambers. The Arizona Department of Health Services 

(1986a) measured 34 violations of MCL's in 11 samples of 

surface water at 5 sites on the Puerco River in Arizona in 

February, April, and June 1985. The violations included 

elevated activities of gross alpha, gross beta, and 226Ra. 

During a flood on July 16, 1986, Chris Shuey (Southwest 

Research and Information Center, written commun., 1987) 

measured total gross alpha activities of 1,700 to 2,200 

pCi/L and gross beta activities of 1,800 to 2,100 pCi/L in 

the Puerco River near Lupton. On July 31, 1987, total gross 

alpha and gross beta activities at this site were 3,200 and 

3,500 pCi/L, respectively (Chris Shuey, Southwest 

Research and Information Center, written commun., 1987). 
Sampling of surface and ground water in the Puerco 

River basin between 1975 and 1986 has indicated that 

MCL's and MAL's for radionuclides were exceeded many 

times. The source of the elevated concentrations may be 

traced either to mining or to natural sources. Natural 

activities of radionuclides in Black Creek, a tributary to the 

Puerco River that was unaffected by uranium mining (fig. 

128), did not exceed MCL's of Arizona for surface water 

(Arizona Department of Health Services, 1986a; Chris 

Shuey, Southwest Research and Information Center, written commun., 1987). No radionuclide data are available for 

surface water for the period before the mining activities of 

the 1950's or before the resumption of mining in 1969. The 

Arizona Department of Health Services ( 1986b) used a 

statistical model of flood-recurrence interval and 

suspended-sediment concentrations to suggest that 226Ra 

activities in mine effluents alone were sufficient to cause 

violations of MAL's of Arizona for surface water in the 

·Puerco River. 

Lower Little Colorado River Basin 

Little is known about radionuclide releases in the 

lower Little Colorado River basin. Arizona Department of 

Health Services ( 1986a) has measured elevated activities of 

gross alpha, gross beta, and 226Ra in the Little Colorado 

River at Holbrook, just below the mouth of the Puerco 

River (fig. 128). Most radionuclides in the Little Colorado 

River probably emanate from the Puerco River. At Rare 

Metals (fig. 127), a contaminated mound of ground water 

underlies an unstabilized tailings pile near Moenkopi Wash, 

which is a tributary to the Little Colorado River (Carol 

Boughton, Navajo Nation, oral commun., 1987). Elevated 

activities of radionuclides near the mouth of the Little 

Colorado River may enter the river as springflow, originate 

in the Cameron Uranium Mining Belt (John McKlveen, 

Arizona State University, oral commun., 1988), or emanate 

from farther upstream. At least 56 springs enter the Little 

Colorado River within 30 mi of its mouth and may 

discharge over 200 fe/s (Loughlin, 1983). Gross alpha plus 

gross beta activities in five samples collected in 1985 and 

1986 at Blue Spring ranged from 5 to 48 pCi/L. Radium226 activities ranged from 0 to 1.6 pCi/L (Errol L. 

Montgomery and Associates, Inc., 1987). 

RADIONUCLIDE ACTIVITIES AT U.S. 

GEOLOGICAL SURVEY GAGING STATIONS 

Puerco River Near Church Rock, New Mexico 

The U.S. Geological Survey gaging station near 

Church Rock (09395350) has a drainage area of 205 mi2 

and is 5 mi downstream from the United Nuclear Corporation facility and 9. 5 mi northeast of Gallup. A water-quality 

sample was collected on July 17, 1979, and again on July 

19, 1979, at this station (table 58). Discharges at times of 

sample collection were 7.1 and 8.0 ft3

/s, and pH was 3.6 

and 5. 2, respectively. Significantly smaller activities for 

dissolved gross alpha, dissolved gross beta, and dissolved 226Ra on July 19 correspond with flushing of tailings-pond 

effluent from the reach by mine dewatering (table 58). 

Puerco River at Gallup, New Mexico 

The U.S. Geological Survey gaging station at Gallup 

(09395500) has a drainage area of 558 mi2 and is in the city 

limits (fig. 128). Seventeen water-quality samples were 

collected by the U.S. Geological Survey at the gage from 

1975 to 1984, and selected analytical results are shown in 

table 58. Maximum activities of both dissolved and suspended gross alpha and gross beta were measured on July 

17, 1979, concomitant with a pH of 3.4 (table 58). 

Minimum activities measured for dissolved gross alpha and 

gross beta were 48 and 22 pCi/L, respectively, on August 3, 

1983, and were associated with the maximum discharge 

(116 fe/s), which was measured when radiochemical data 

were collected. Minimum activities measured for suspended 

gross alpha and gross beta were 240 and 300 pCi/L, 

respectively. Dissolved 226Ra activities ranged from 0.07 to 

0.95 pCi/L. Dissolved uranium activities ranged from 18 to 

2,100 pCi/L. Maximum levels of dissolved 226Ra and 

uranium activities were both measured on July 17, 1979. 

Dissolved-solids concentrations measured on July 17 and 

19, 1979, were 8,300 and 4,300 mg/L, respectively, or an 

order of magnitude larger than typical dissolved-solids 

concentrations for this site. 

Puerco River at Chambers, Arizona 

The U.S. Geological Survey gaging station at Chambers (09396100) has a drainage area of 2,160 mi2 and is 1.5 

mi southwest of Chambers (fig. 128). Twenty-nine waterquality samples were collected from 1979 to 1985 (Webb 

and others, 1987b), and selected analytical results are 

shown in table 58. Dissolved and suspended gross alpha and 

gross beta activities have fluctuated widely with time (fig. 

131). Concentrations of total uranium, chloride, and sulfate 

fluctuated in 1979 apparently as a result of the tailings-pond 

spill (fig. 131). After 1980, changes in concentrations of 

these constituents are not well known because only three 

samples were measured for these constituents between May 

1980 and May 1985. Concentrations of total uranium 

average about 0.1 mg/L between 1980 and 1985. The 

amount of dissolved uranium is not definitively known, but 

data for 1985 (Arizona Department of Health Services, 

1986a) indicate that the concentration of dissolved uranium 

is 30 to 70 percent of the total uranium concentration. 

Activities of radionuclides, particularly those in the susRadionuclides in the Puerco and Lower Little Colorado River Basins, New Mexico and Arizona 303 
Table 58. Radionuclide activities and associated data of selected samples from U.S. Geological Survey gaging stations on 

the Puerco and lower Little Colorado Rivers, Arizona and New Mexico 

[ft3/s, cubic feet per second; J.LS/cm, microsiemens per centimeter; pCi/L, picocuries per liter; U-NAT, uranium natural; Cs-137, cesium-137; <,less than 

indicated value; ±, precision; dashes indicate no data available] 

Specific Gross alpha Gross beta 

Discharge Dissolved Suspended Dissolved Suspended Radium-226, Uranium, Date (fe/s} pH conductance (pCi/L as (pCi/L as (pCi/L as (pCi/L as dissolved dissolved (J.LS/cm) U-NAT) U-NAT) Cs-137) Cs-137) (pCi/L} (pCi!L) 

Puerco River near Church Rock, N. Mex (09395350) 

July 17, 1979 7.1 3.6 3,450 560±110 5,400± 1 '100 150±30 1,800±360 1.0± .10 

July 19, 1979 8.0 5.2 2,300 <18±4 2,800±560 <9.9±2 1,100±220 .47±.05 

Puerco River at Gallup, N. Mex. (09395500) 

October 6, 1976 ..... 8.2 800 1

1,900±380 1950±190 460±90 520±100 .84±.08 1,200± 180 

July 17, 1979 ••• 0 •• 0 11 3.4 8,300 5,200 ± 1 ,000 33,000±6,600 1,800±360 9,200± 1,840 .95±.10 2

2,100±320 

July 19, 1979 ••• 0 ••• 11 7.2 4,300 <58±12 12,000±2,400 34±7 4,200±840 .40±.04 2

55±8 

December 18, 1980 .... 4.8 8.5 800 750± 150 240±50 110±20 300±60 .68±.07 2

540±80 

May 4, 1981. ........ 9.6 8.9 955 1,400±280 590±120 370±70 690±140 .33±.03 2

1,100± 160 

December 7, 1982 ... 22 8.5 840 620±120 520± 100 230±50 600±120 .13±.01 2

820± 120 

August 3, 1983 ...... 116 7.8 48±10 1,800±360 22±4 1,700±340 .22±.02 2

18±3 

July 18, 1984 5.1 8.1 1

680±140 1

2,200±440 100±20 1,400±280 .15± .02 2630±94 

Puerco River at Chambers, Ariz. (09396100) 

July 26, 1979 ....... 6.2 4,730 99±20 .20±1 

May 18, 1982 ....... .04 8.7 1,220 160±30 68±14 41±8 140±30 

August 15, 1983 ..... 39 914 29±6 I< 1 , 500 ± 300 17±3 1,000±200 .20±1 2

25±4 

March 7, 1984 ...... 4.2 8.4 1,190 160±30 68±14 54±11 92±18 <.10±1 

March 28, 1984 60 8.4 1,180 140±30 820±160 29±6 1,200±240 <.10±1 

Little Colorado River at Cameron, Ariz. (09401200) 

June 6, 1980 ........ 1.4 8.4 1,280 <6±1 2±.40 7±1 2±.40 

July 15, 1981 ........ 231 8.0 1,190 13±3 3,900±780 12±2 3,200±640 

March 1 , 1982 ...... 1,340 8.2 445 20±4 1,700±340 10±2 1,700±340 

November 30, 1983 .. 44 8.4 903 1

<9±2 520± 100 <8±2 560± 110 

April 9, 1984 ....... 16 8.4 1,750 54±11 820±160 <16±3 860±170 

1

Micrograms per liter were converted to picocuries per liter by multiplying micrograms per liter by 0.68. This conversion is based on the assumptions 

that uranium-234 is in equilibrium with uranium-238 and that all alpha emission is from uranium. 2

Micrograms per liter were converted to picocuries per liter by multiplying micrograms per liter by 0.68. This conversion is based on the assumption 

that uranium-238 is in equilibrium with uranium-234. 

pended phase, are related statistically to suspendedsediment concentrations at Puerco River at Chambers (Arizona Department of Health Services, 1986b; Chris Shuey, 

Southwest Research and Information Center, written commun., 1987). 

Variations in measurable activities of radionuclides in 

streamflow in the Puerco River likely are caused in part by 

areal variability of tributary inflow. Tributary basins contain varying amounts of exposed uranium-bearing rock. 

Quality of runoff from tributaries depends partly on the 

amount of exposed uranium-bearing rock and amount and 

rate of precipitation or snowmelt. Variability of precipitation in the Puerco River basin, in conjunction with variability in amounts of exposed uranium-bearing rocks, results in 

highly variable discharges of radionuclides from tributaries 

to the main channel. Also, streamflow may cause remobilization of sediments deposited after the tailings-pond dam 

spill of 1979 (Arizona Department of Health Services, 

304 Field Studies of Radon in Rocks, Soils, and Water 

1986b). This mechanism also may produce large fluctuations in the activity of radionuclides carried by the Puerco 

River into Arizona. Extensive monitoring of surface water 

in the Puerco River indicates that water· recharging the 

alluvial aquifer in Arizona is of widely fluctuating quality. 

For example, dissolved gross alpha plus dissolved gross 

beta activities measured in samples from runoff in the 

Puerco River basin at Chambers, Ariz., ranged from 18 

pCi/L to 273 pCi/L. 

Little Colorado River at Cameron, Arizona 

The Little Colorado River at the sampling site at 

Cameron has an approximate drainage area of 24,000 me. 

Seventeen water-quality samples were collected and analyzed for gross alpha and gross beta activities from 1979 to 

1984. Selected analytical results are shown in table 58, and 
300 < :I: 

~ 225 (II 

(II 

0 

~ 150 

s 

~ 75 0 

(II 

(II 

0 

0 

<8,000 

:I: 

~ 

~6,000 

(II 

~ 0 

~4.000 0 It: ILl 

~ 0 

~2.000 ff) Q. 

(II 

~ ;:) 

;:) (II 

0 0 0 

0 450 ii: :< ~ 

~360 ~ E ~ > ~ 270 t (!) 

< s 180 

~ 

0 90 (II 

(II 

0 

0 

~ 

4,500 

a13,600 

(II 

(II 

~2.700 (!) 

~1.800 

~ 900 (II 

;:) 

(II 

0 

en 0 iii N I') .q- 10 

~ tX) tX) tX) tX) tX) 

S! S! S! S! S! S! 

co 

tX) 

S! 

It: 5 350 

It: 

~ 300 

(II 

~ 250 

~ 0 200 

5 

~ 150 ~ 

r:: &......--.L&&.LI ---'----1-----L.--..&I~.....___., 80 I 

0 I Jl 

1,000 .-----r----r------r---r-----,----r-----. 

It: 

5 800 - It: 

ILl 

Q. 

(II 

2 600 ~ < It: 

(!) 

3 

~ 400 ~ 

?: 

~ 5 200 

;:) 

II J I (II 

0 

en 0 iii N I') .q- 10 co 

~ tX) tX) tX) tX) tX) tX) 

S! S! S! S! S! S! S! 

Figure 131. Temporal variations of selected chemical constituents in the Puerco River at Chambers, Arizona. 

figure 132 shows dissolved and suspended gross alpha and 

gross beta activities measured from the 17 samples. Activities of individual radionuclides were not analyzed. Activities of dissolved gross alpha ranged from less than 6 to 54 

pCi/L, and dissolved gross beta activites ranged from 7 to at 

least 12 pCi/L. Unlike data from the Puerco River, however, the suspended fraction of both gross alpha and gross 

beta was typically one to two orders of magnitude larger 

than the associated dissolved fraction (fig. 132). All pH 

measurements were 7.6 or larger. The relatively small ratio 

of dissolved activities to suspended activities in the Little 

Colorado River at Cameron suggests that the effects of 

mining in the Grants Mineral Belt, more than 200 mi 

upstream, either are muted or are masked by suspended 

radiochemical inflows from other sources. 

CHARACTERIZATION OF QUALITY OF 

GROUND WATER 

Puerco River Basin 

On the basis of 14 well samples collected in December 1986 (Webb and others, 1987b), quality of water in the 

alluvium was characterized by dissolved-solids concentrations that were larger than 500 mg/L, sulfate concentrations 

that were larger than 250 mg/L, and some activities of 

radionuclides that exceeded MCL's. The median concentration of dissolved solids is 698 mg/L; alkalinity, sodium, 

and sulfate constitute most of this total. Concentrations of 

dissolved solids, sulfate, and chloride are similar to concentrations in samples measured in the 1930's (Harrell and 

Eckel, 1939). 

Radionudides in the Puerco and Lower Little Colorado River Basins, New Mexico and Arizona 305 
60 -< 

~~ ~ 0 

~30 

~ 15 en 

!l! 

0 0 

....:10,000 

~ ~ 7,500 

~ 0 

~ 5,000 

a ~ 0 

~ ~ 2,500 

en a: :::> :::> en 0 0 0 

0 20 II: 

3: ~ ~ ID 15 

I ~ 0 

~ 10 

a 

~ 5 

Ia 

0 

0 

6,000 

~ m5,000 

~4,000 

~ aJ,ooo 

~2,000 

~1,000 

en 0 

~ 0 iii ('I ~ 

~ 10 <0 co co co co co ~ ~ ~ ~ ~ ~ ~ 

Figure 132. Temporal variations of selected chemical 

constituents in the Little Colorado River at Cameron, Ariz. 

Arizona maximum allowable limits are 15 picocuries per 

liter of gross alpha minus uranium and 30 picocuries per 

liter of gross alpha plus gross beta. Gross alpha activities 

are not corrected for uranium activity. 

Median total gross alpha activity is 27 pCi/L, and 

activities range from 4 to 42 pCi/L. Median total gross beta 

activity is 6 pCi/L (table 59), and activities range from 1 to 

19 pCi/L. Uranium concentration normally is about 4.5 

J.Lg/L in ground water in the United States (Cothern and 

others, 1983). In samples from the Puerco River basin and 

surrounding areas, normal concentrations of uranium 

ranged from 0.1 to 6.1 J.Lg/L (Scott and Barker, 1962). 

Uranium concentrations in 14 wells and a spring in the 

Puerco River basin ranges from 1 to 38 J.Lg/L with a median 

value of 19 J.Lg/L. Other radionuclides, including 226Ra, 228Ra, 210Pb, and 230Th, generally have activities less than 

1 pCi/L. Only one well had a 226Ra plus 228Ra activity 

exceeding 5 pCi/L (Webb and others, 1987b). These data 

indicate that uranium activities account for most of the gross 

alpha activity measured in samples from the 14 wells. 

306 Field Studies of Radon in Rocks, Soils, and Water 

Table 59. Average and median concentrations or activities 

of selected constituents measured in 15 ground-water 

samples from the Puerco River basin, December 1-6, 1986 

[Values in parentheses are medians; includes values less than the detection 

limit that were considered equal to the detection limit in the arithmetic 

mean. The average and median pH values are 7. 7 and 7. 8, respectively. 

The average and median temperatures are 15 °C and 14 °C, respectively] 

Common ions 

(milligrams per liter, dissolved) 

Alkalinity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345 

Calcium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 

Chloride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 

Fluoride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 

Magnesium . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 

Potassium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8 

Silica . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 

Sodium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230 

Sulfate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 

Selected trace elements 

(micrograms per liter, total recoverable) 

Aluminum 

Arsenic .............................. . 

Barium .............................. . 

Boron ............................... . 

Cadmium ............................ . 

Copper .............................. . 

Iron .................................. . 

Lead ................................. . 

Manganese ............................ . 

Selenium ............................. . 

Strontium ............................. . 

Vanadium ............................ . 

Zinc .................................. . 

Radionuclides 

260 

<2.2 

<110 

400 

<2 

18 

540 

<6 

<240 

<44 

1,000 

<44 

85 

(picocuries per liter, except as noted, total) 

Gross alpha . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 

Gross beta . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

Lead-210 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 

Radium-226 . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 

Radium-228............................ <.7 

Thorium-230. . . . . . . . . . . . . . . . . . . . . . . . . . . .1 

Uranium (micrograms per liter).......... 19 

Lower Little Colorado River Basin 

(341) 

(75) 

(61) 

(.8) 

(15) 

(2.0) 

(14) 

(230) 

(280) 

(20) 

(1) 

(<100) 

(380) 

(<1) 

(9) 

(360) 

(<5) 

(140) 

(<39) 

(840) 

(<39) 

(70) 

(27) 

(6) 

(.4) 

(.1) 

(.3) 

(.0) 

(19) 

Few data are available on ground-water quality in the 

lower Little Colorado River basin. Don Payne (Navajo 

Nation, written commun., 1987) described water-quality 

data collected in 1984, 1985, and 1986 at 49locations in the 

Cameron Uranium Mining Belt region. Water samples from 

mining pits and nearby springs were considered indicative 

of ground-water conditions near the pits (Don Payne, 

Navajo Nation, written commun., 1987). All samples 

collected were analyzed for total concentrations or activities 

of constituents. 

Analyses of water samples collected from 21 

abandoned uranium mines yielded gross alpha activities that 

ranged from 24 to 9,400 pCi/L. Most of the gross alpha 

activity was attributed to 226Ra and uranium (Don Payne, 
Navajo Nation, written commun., 1987). Radium-226 

activities ranged from near below detection level to 760 

pCi/L. Uranium activities ranged from 24 pCi/L to 4,020 

pCi/L. 

Gross alpha activities in water from six wells ranged 

from 3 to 10 pCi/L in the Cameron Uranium Mining Belt 

(Don Payne, Navajo Nation, written commun., 1986). 

Gross beta activities ranged from near 2 to 22 pCi/L. 

Radium-226 activities were below 0.8 pCi!L, whereas 

uranium activities ranged from 2 to 10 pCi/L. 

Water from 14 developed springs had gross alpha 

activities that ranged from 4 to 200 pCi!L; gross beta 

activities ranged from 3 to 90 pCi!L; and all 226Ra activities 

were below the detection limit. Uranium activities ranged 

from 11 to 159 pCi!L. The maximum value for gross alpha 

activity was measured concomitant with a uranium activity 

of 98 pCi/L at one of three springs where "obvious signs" 

indicated that "local people used the spring ... as a source of 

potable water" (Don Payne, Navajo Nation, written commun., 1987). 

AREAL AND TEMPORAL VARIATIONS IN 

WATER QUALITY 

Puerco River Basin 

When distance from the river is compared with 

radionuclide activities, the wells having the largest 

activities are not necessarily the wells closest to the river. 

For example, water from a well located approximately 

1 ,000 ft from the Puerco River had a gross alpha plus gross 

beta activity of 7 pCi/L. Water from a well across the river 

and approximately 2,100 ft from the channel had a gross 

alpha plus gross beta activity of 27 pCi/L (Webb and others, 

1987b). Similar differences were observed in wells at 

varying distances from the Puerco River at other study sites. 

The data also indicate that radionuclide activity was not 

related to the distance from the headwaters of the Puerco 

River (Webb and others, 1987b). 

In addition to the 14 wells and 1 spring sampled in 

December 1986, historical water-quality data were 

available for 7 wells and 1 spring (Webb and others, 

1987b). Ground-water samples from 1969, 1974, 1975, and 

December 1986 were collected and analyzed by the U.S. 

Geological Survey. The remaining samples were collected 

by other agencies-notably the Environmental Protection 

Agency- and the Indian Health Service and were analyzed 

by several different laboratories. 

Data collected for Begay Well near the State line of 

Arizona and New Mexico include 32 water-quality 

measurements made before December 1986. Temporal 

variations of gross alpha, chloride, and sulfate indicate that 

activities and concentrations have fluctuated with time. For 

example, concentrations of sulfate rose from about 500 

mg/L to as much as 1,600 mg/L after the spill of 1979 and 

declined thereafter to at least 840 mg!L in December 1986. 

Gross alpha activities also fluctuated during the same 

period. The gross alpha activity measured in 1986 was 

similar in magnitude to the largest historical activities, 

although the activity in 1986 is the largest measured 

between 1979 and 1986. The difference may result from the 

fact that the 1986 sample was the only sample collected 

immediately after the well had been pumped (Don Payne, 

Navajo Nation, written commun., 1988). 

Historical variations in ground-water quality reflect 

the fluctuations in water chemistry of recharge to aquifers 

from the Puerco River. The data indicate that activities of 

radionuclides in ground water have fluctuated with time but 

have increased in some wells following the failure of the 

tailings-pond dam in 1979 near Church Rock, N. Mex. 

Concentrations of other constituents, such as chloride, 

appear to have changed little with time except at Begay 

Well, which is 50 ft from the Puerco River and may 

withdraw some of its water supply from the river through 

the alluvium. 

PROCESSES CONTROLLING THE MOVEMENT 

OF RADIONUCLIDES 

Radionuclide activities in surface water of the Puerco 

River at Chambers and Little Colorado River at Cameron 

are large compared with historical activities in ground water 

from wells. Total uranium concentrations have been 

approximately 100 J,Lg!L in the Puerco River; however, 

concentrations of dissolved uranium are unknown. The 

median concentration of total uranium in water from wells 

near the Puerco River sampled in December 1986 is 19 

J.Lg/L. Activities of 230Th and 226Ra have been large in 

surface waters and suspended sediments of the Puerco River 

(table 58; Weimer and others, 1981; Arizona Department of 

Health Services, 1986a), but these radionuclides do not 

occur in significant activities in the ground water of that 

region. The median activity of total uranium in wells 

sampled by Don Payne (Navajo Nation, written commun., 

1986) is 12 pCi/L. Uranium activities in surface water of the 

Little Colorado River are unknown. 

Geochemical processes related to sediments in the 

surface water, clays, and grain coatings in the aquifer, in 

addition to chemistry of the ground water, may effectively 

reduce the radionuclide activities before recharge water 

reaches the wells. Two of the processes that remove 

radionuclides from water as it moves through the aquifer are 

mineral/water interactions and sorption. One chemical process capable of removing a radionuclide from solution is the 

precipitation of a mineral containing the radionuclide 

(Stumm and Morgan, 1970). Certain radionuclides, 

especially radium isotopes, may coprectpttate by 

substitution for a different cation, such as barium (Ba + 2

), in 

Radionuclides in the Puerco and lower Little Colorado River Basins, New Mexico and Arizona 307 
a mineral that is precipitating (Langmuir and Riese, 1985). 

Sorption processes involve surface chemistry of certain 

minerals with water, such as cation exchange of radionuclides with other cations on clays (Beard and others, 1980), 

adsorption on particles, and complex cation reactions with 

organic compounds that adsorb with other cations or are 

taken up by plants (Landa, 1980). Sayre and others (1963) 

and Beard and others (1980) provide a more detailed 

description of the sorption process. Other processes, such as 

volatilization or biological activity, also may remove 

natural radionuclides from the· water, although there is no 

documentation of these processes occurring in the alluvium 

of the Little Colorado River basin. 

To test the importance of chemical reactions in 

ground water, a solution-equilibrium computer model 

(Kharaka and Barnes, 1973) that includes the reactions 

involving uranium (Y.K. Kharaka, U.S. Geological 

Survey, written commun., 1987) was used to determine the 

solubility of uranium minerals. Thermodynamic data for 

uranium are given by Langmuir (1978). The concentrations 

for uranium, measured as total concentrations, were 

assumed to be dissolved concentrations. The suspended and 

colloidal concentrations, therefore, are assumed to be 

negligible. Finally, the redox state was assumed to be 

positive, or oxidizing, owing to measurable concentrations 

of dissolved oxygen. 

The solution-equilibrium model distributes measured 

concentrations of an element or compound among different 

chemical species. These species include cations, or 

positively charged ions; anions, or negatively charged ions; 

and complexes, which can be positively charged, negatively 

charged, or electrically neutral compounds. The ability of 

the chemical species to remain in solution is calculated from 

the saturation index of the minerals that could precipitate as 

a result of ionic activities of the necessary chemical species. 

The saturation index (SI) is defined as 

SI = log(AP/K(T)), (1) 

where 

AP =ionic activity product and 

K(T)=equilibrium constant at absolute temperature, T 

(Lee and Strickland, 1988). 

If the value saturation index exceeds 0 for a chemical 

reaction, precipitation will occur; if the saturation index is 

negative, dissolution of the mineral will occur if it is present 

in the aquifer (Kharaka and Barnes, 1973). Stumm and 

Morgan (1970), Kharaka and Barnes (1973), and Hem 

(1985) give more information on the chemical reactions. 

The concentrations of constituents shown in table 59 

for all 15 water samples collected in December 1986 were 

used in the solution-equilibrium model. Uranium-bearing 

minerals that could possibly precipitate from the ground 

water have negative saturation indices in all 15 groundwater samples, and these values indicate that uranium 

308 Field Studies of Radon in Rocks, Soils, and Water 

precipitation should not occur. To test whether the waters 

were close to saturation, the average concentrations of the 

15 samples (table 59) also were used in the solutionequilibrium model. For modeling purposes, the uranium 

concentration was increased in the average sample from 19 

J..Lg/L to 100 j.Lg/L, which is the average total concentration 

in surface water, and to 360 j.Lg/L, which is the largest total 

concentration measured in the Puerco River at Chambers 

(fig. 131). Concentrations are large because 30 to 70 

percent of the total uranium is either in suspended sediments 

or in colloids. The negative saturation indices for all 

samples having the largest concentrations of uranium (table 

60) indicate that uranium precipitation should not occur. 

The dominant species containing uranium in the carbonaterich aquifer are U02(C03h - 2 and U02(C03h - 3 . 

Sorption decreases the amount of uranium in 

solution. Uranium is strongly adsorbed by organic 

compounds or clays, with maximum adsorption occurring at 

pH levels between 5 and 6 (Ames and Rai, 1978). Uranium 

complexes change from positively charged to negatively 

charged at a pH of about 6 (Ames and Rai, 1978; Langmuir, 

1978). Uranium can be adsorbed onto particles that have 

amorphous iron-oxyhydroxide coatings, and the amount of 

adsorption is largest between pH levels of 5. 5 and 8. 5 

(Langmuir, 1978). In the alluvial aquifer of the Puerco 

River, where pH is generally between 7.5 and 8.5, uranium 

should not precipitate from ground water under oxidizing 

conditions but may be adsorbed on iron-oxyhydroxidecoated particles. The data collected in this study suggest 

that uranium is mobile in the alluvial aquifer under 

oxidizing conditions. 

Other radionuclides have a different behavior. At pH 

levels of 7.5 to 8.5, thorium exists predominantly as 

thorium hydroxide (Langmuir and Herman, 1980), which is 

a mineral of low solubility (Ames and Rai, 1978). On the 

basis of thermodynamic data given by Langmuir and 

Herman (1980), the equilibrium activity of 230Th is 0.2 

pCi/L in alluvial ground water containing the average 

concentrations of constituents shown in table 60. Thorium 

is readily adsorbed on clays (Ames and Rai, 1978; Beard 

and others, 1980) and is almost completely adsorbed at pH 

levels greater than 6.5 (Langmuir and Herman, 1980). 

Thorium, therefore, is nearly immobile in a neutral or 

alkaline environment except when transported on sediment 

in surface water. The lack of 230Th activities that are 

significantly greater than the detection limit further 

indicates that thorium is immobile in ground water of the 

alluvial aquifer of the Puerco River. 

Radium-226 and 228Ra are chemically similar to 

barium (Ames and Rai, 1978) and form sulfate and 

carbonate complexes (Langmuir and Riese, 1985). 

Calculations for the equilibrium concentrations (if all free 

carbonate ions are bound in radium-carbonate complexes) 

indicate that 180 mg/L of total radium (about 

1.8X 1011pCi/L of 226Ra) could dissolve in the water. 
Table 60. Values of saturation indices for minerals of uranium and lead in an average sample of ground water from the 

Puerco River basin with uranium concentrations of 0.019, 0.100, and 0.360 milligrams per liter 

[Thermodynamic data for uranium minerals are from Langmuir (1978). Saturation indices for concentrations of uranium (milligrams per liter) are calculated 

from equation 1 using the average concentrations of constituents in ground water given in table 59] 

Solid-phase mineral Saturation indices for concentrations of uranium (milligrams per liter) 

Formula 

U02C03 •..••••.•••..••...•••...••. 

uo3 ••••.•••..•••..••...••.•.••.... 

U02 (0H)z ........................ . 

Kz(U02)z(V04)z ............... · ... · 

Caz(U02)z(V04)z ........ · · .. · · · · · · · 

Caz(U02)z(HSi04)z ................ . 

U02(0H)z · H20 .................. . 

MgU04 •••••••••••••••••••••••••••• 

CaU04 •.•.•••.•.••..•••...••.•.••. 

BaU04 •.••••..•••..••...••...••... 

U02F2 •...••••.••••..••..••....•••. 

PbC12 •••••••••••••••••••••••••••••• 

PbC03 •.•••.•••...••...•....••..•.• 

PbO ............................. .. 

PbO .............................. . 

PbS04 .•••.•.••.••••..••..•••....•• 

PbiV04 )z ........................ . 

Name 

Rutherfordine 

Gurnrnite 

Carnotite 

Tyuyarnunite 

Uranophane 

Schoepite 

Cotunnite 

Cerussite 

Litharge 

Massi cot 

Angle site 

Radium activities in natural waters are regulated by 

coprecipitation in other minerals and adsorption (Langmuir 

and Riese, 1985). Coprecipitation may occur in barite 

(BaS04 ), which has a saturation index of 0.9 in the average 

concentrations measured in the Puerco River basin. Radium 

may be sorbed on clays (Landa, 1980), although physical 

and chemical factors governing the adsorption are not well 

known (Beard and others, 1980). Ames and Rai (1978) 

report a correlation between the cation-exchange capacity of 

clays and the adsorption of radium. 

Published data on radium are inconclusive with 

respect to mobility in ground water in the Little Colorado 

River basin. Radium may be adsorbed too strongly on clays 

to be transported as dissolved species. The magnitude of 

adsorption is evident in a significant correlation in increased 226Ra activity and increased suspended sediment in the 

Puerco River (Arizona Department of Health Services, 

1986b) compared to small radium activity in surface water 

and ground water near uranium mines or mills (Kaufmann 

and others, 1976; Yang and Edwards, 1984). Although 

radium is dissolved in water as (RaS04)

0 and (RaC03)0

, 

radium occurs principally in the solid phase in the alluvial 

aquifer of the Puerco River basin because of coprecipitation 

and adsorption processes. 

Lead-210 is expected to have the same chemical 

properties as stable lead, has a half-life of 22 years, and can 

produce an activity of 1 pCi/L at a concentration of 

1. 3 X 10- 8 J.Lg/L. Saturation indices calculated from the 

av{~rage concentration suggest that two of six mineral 

phases are supersaturated at a lead concentration of 6 f,LgiL 

0.019 0.100 0.360 

-3.0 

-7.8 

-5.7 

-6.7 

-5.2 

-11.2 

-4.4 

-11.9 

-2.7 

-8.9 

-16.7 

-8.1 

.3 

-5.2 

-5.4 

-2.6 

4.3 

-2.3 -1.7 

-7.0 -6.5 

-5.0 -4.5 

-6.0 -5.5 

-4.5 -4.0 

-9.7 -8.6 

-3.7 -3.1 

-11.2 -10.6 

-2.0 -1.5 

-8.0 -7.6 

-16.1 -15.5 

(table 60). Cerussite (PbC03), one of the two supersaturated minerals (table 60), controls the chemistry of lead in 

carbonate-rich waters at a pH of 8 (Stumm and Morgan, 

1970). Lead also can be adsorbed by clay particles. The net 

effect of the chemical processes on the mobility of 210Pb in 

the alluvial aquifer of the Little Colorado River basin is 

unknown. 

DISCUSSION 

The presence of uranium ores in the Little Colorado 

River basin of Arizona and New Mexico probably contributes to elevated background levels of radionuclides in 

surface water and ground water. Impacts of mining superimposed on generally large background levels of radionuclides and other trace elements probably increased levels of 

radionuclides in some water resources of the region. The 

quality of both surface water and ground water in the Puerco 

River basin varies both temporally and areally, and the 

same probably is true for the lower Little Colorado River 

basin. 

Radionuclide transport in surface water and ground 

water is poorly understood. As of 1987, there are few 

reliable data on the presence and activities of radionclides in 

the Little Colorado River basin. Additionally, the lack of 

understanding of the processes that govern radionuclide 

movement and storage in the basin limits assessments of 

trends in the occurrence of contamination. This knowledge 

needs to be attained to develop and manage safe and reliable 

water supplies in the region. 

Radionuclides in the Puerco and Lower Little Colorado River Basins, New Mexico and Arizona 309 
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geochemistry, and conclusions and evaluation: Las Vegas, 

Nev., Environmental Protection Agency Report EPA 

520/6-78-007-A, 330 p. 

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---1986b, Puerco River sediment loading model, Puerco 

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properties of radium: Geochimica et Cosmochimica Acta, v. 

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Health Physics, v. 48, p. 535-551. 

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southeastern North Carolina: American Geophysical Union, 

Water Resources Research, v. 24, no. 2, February 1988, 

p. 291-303. 

Loughlin, W.D., 1983, The hydrogeologic controls on water 

quality, ground-water circulation, and collapse breccia pipe 

formation in the western part of the Black Mesa hydrologic 

basin, Coconino County, Arizona: Laramie, Wyo., University of Wyoming, unpublished M.Sc. thesis. 

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use in southern Apache County, Arizona: Arizona Department of Water Resources Bulletin 1, 86 p. 

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rules and regulations: Phoenix, Ariz., State of Arizona 

report, Advance Supplement 84-3, p. 68-84. 

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regulations: Phoenix, Ariz., State of Arizona report, Advance 

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uranium mill tailing spill-A health and environmental 

assessment, Technical Report I, Radiological Impacts: Albuquerque, N. Mex., New Mexico Health and Environment 

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discharges from New Mexico Uranium Mines and Mills: 

Albuquerque, N. Mex., New Mexico Health and Environment report, 87 p. 

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and transport of radionuclides by stream sediments: U.S. 

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in ground water in the United States, 1954 to 1957: U.S. 

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Puerco, but seepage problem consumes New Mexico's 

response: Mine Talk, v. 2, p. 10-26, 

---1986, The Puerco River-Where did the water go?, in 

The workbook: Albuquerque, N.Mex., Southwest Research 

and Information Center, v. XI, no. 1, p. 1-10. 
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regulations, title 12: Phoenix, Ariz., State of Arizona report, 

Advance Supplement 77-3, p. 1-133. 

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York, N.Y., John Wiley and Sons, 583 p. 

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along the Puerco River, northeastern Arizona-A reconnaissance sampling program: U.S. Geological Survey Open-File 

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Schultz, W.W., eds., Geochemical behavior of disposed 

radioactive waste: American Chemical Society Symposium 

Series, no. 246, p. 271-286. 

Radionudides in the Puerco and Lower Little Colorado River Basins, New Mexico and Arizona 311 

URANIUM, RADIUM, AND RADON IN DEEPLY BURIED SEDIMENTS OF THE 

U.S. GULF COAST 

Thomas F. Kraemer 

Abstract 

Uranium, radium, and radon were examined in the 

water, rock, and gases of deeply buried clastic sediments 

of the U.S. Gulf Coast. Results of these investigations are 

summarized in this paper. Uranium in solution in all cases 

examined seemed to be at or near saturation with a 

uranium mineral phase, either uraninite or coffinite. The 

presence of radium isotopes in solution in excess of 

supporting parent nuclides indicates a continuous 

removal of radium from the solid phase to the aqueous 

phase. The efficiency of this removal is proportional to the 

total dissolved-solids concentration of the aqueous phase. 

Radon was present in excess of radium in the aqueous 

phase in formation waters of less than 95 grams per liter 

total dissolved solids, whereas radon and radium were in 

secular equilibrium in waters above 95 grams per liter total 

dissolved solids. 

INTRODUCTION 

Conditions deep in large sedimentary basins are 

radically different from those of surface and near-surface 

environments; water temperature is much higher, pressure 

is greater, and the water usually is much more saline than 

surface or shallow ground waters. As a result, many 

changes take place that produce diagenetic reactions, mineralogic transformations, and changes in elemental distributions between water, rock, and gaseous phases present in 

the system. Examination of uranium- and thorium-series 

radioelements in this three-phase system can reveal a great 

deal about physical and chemical processes taking place in 

this environment. This report summarizes results of examinations of the natural radionuclide content of water, rock, 

and gas phases present in the thick clastic sequence of 

sediments deposited in the northern Gulf of Mexico basin. 

Samples of rock, water, and natural gas were collected from these formations. The sources of the samples 

were from oil and gas wells and "geopressured-geothermal" 

energy test wells. These latter wells, which were basically 

research wells, were drilled by the U.S. Department of 

Energy in Louisiana and Texas to test the possibility of 

recovering commercial amounts of dissolved methane from 

hot, highly pressured aquifers. Care was given to drilling, 

completion, and production techniques to maximize scientific usefulness. They yielded large volumes of brine that 

were accurately measured, as was any gas or gas condensate 

produced. In several cases, the wells also were cored 

through the productive sandstone, and these cores were the 

sources of the rock samples. These wells, though few in 

number, provided excellent samples of water, rock, and 

gas. 

The hydrocarbon-producing wells, drilled and owned 

by petroleum companies and also located in Louisiana and 

Texas, generally produced much less water than the 

geopressured-geothermal wells and presented sampling 

problems, in many cases. For example, at many wells that 

yielded only a small amount of water, the water was stored 

in tanks where cooling and oxidation could occur. At these 

wells, it was much more difficult to collect samples that 

were representative of in situ conditions, especially for 

uranium and radium, but the data reported in this summary 

are felt to be representative. Specific sampling techniques 

can be found in Kraemer and Reid ( 1984), Kraemer ( 1986), 

and Kraemer and Kharaka ( 1986). 

GEOLOGIC SETTING 

The study area encompasses the coastal section of 

Texas and Louisiana, where thick sequences of clastic 

sediments have been accumulating in the Gulf Coast geosyncline, a subsiding basin of deposition which presently is 

estimated to contain more than 15,000 m (meters) of 

water-saturated sediments at its center (Hardin, 1962). The 

major sedimentary rock types in this basin are sandstones 

and shales, the result of deposition of sediment carried by 

rivers draining the interior of the North American continent. 

Basinal subsidence, salt tectonics, and differential 

compaction of sand and shale layers resulted in the formation of an extensive system of faults in the Gulf Coast 

sediments. This subsidence heated the permeable sandstone 

aquifers, and the faulting compartmentalized them. As a 

result, high temperatures and high fluid pressures developed 

in water occupying the pore spaces. During the subsidence 

and compaction sequences, the contained pore fluids commonly accumulated large amounts of dissolved methane 

from the breakdown of indigenous kerogen. Salinity of the 

pore fluids commonly increased above that originally 

trapped at time of initial deposition of the sediment. The 

most often cited processes causing salinity increase are ion 

filtration by shale beds (White, 1965; Jones, 1969) and 

dissolution of Jurassic salt beds underlying the area (Kharaka and others, 1978). Salinity decreases also occur, 

probably as a result of clay-mineral diagenesis (Burst, 

1969) as temperatures rose above 110 °C in the sediment. 

URANIUM 

Uranium is present in solution in deep sedimentary 

aquifers in very low concentrations, ranging from 0.003 

Uranium, Radium, and Radon in Deeply Buried Sediments of the U.S. Gulf Coast 313 
Table 61. Uranium content of geopressured-geothermal 

formation-water samples from the U.S. Gulf Coast 

[From Kraemer and Kharaka, 1986, table 1; 2340, uranium-234; 2380, 

uranium-238; F, filtered; N, nonfiltered; J.Lg/L, micrograms per liter] 

Well Uranium 234u;z3su 

Filtering (f.Lg/L) activity ratio 

2 Zellerbach 0 •••••••••••• 0.007±.001 1.23± .10 N 

2 Sutter ................. .030±.002 1.21±.10 N 

1 Sweezy •••• 0 ••••••• 0 •• .003±.002 1.15± .30 N 

1 Girouard .............. .011±.001 1.35±.20 F 

2 Simon ... ·········· ... .009±.001 1.21 ± .12 N 

2 Pleasant Bayou •••••• 0 •• .003±.001 1.42±.14 N 

1 Delcambre, Planulina 3 ... .010±.001 1.62±.15 F 

1 Delcambre, Planulina 1. . . .005±.001 1.06±.10 F 

2 Saldana •••••••••••• 0 •• .044±.003 1.35±.15 F 

1 Koelemay ............. .054±.010 1.38± .10 F 

1 Prairie Canal ........... .030±.005 1.28±.10 N 

1 Amoco Fee (zone 5) ..... .003±.001 1.69± .17 F 

J.LgiL (micrograms per liter) to 0.054 J.Lg/L (table 61). This 

low concentration is consistent with the reducing nature of 

the formation water, where uranium is in a reduced, 

insoluble oxidation state. Kraemer and Kharaka (1986) 

have shown by use of chemical equilibrium modeling that 

the uranium concentrations presented in table 61 are very 

close to what would be expected for these formation waters 

in contact with solid uraninite (U02) or coffinite (USi04) at 

the presumed in situ pH and Eh conditions within the 

aquifers. 

Data on the nature or distribution of uranium minerals 

in geopressured-geothermal aquifers are not available, but it 

seems reasonable that the early diagenetic history of the 

sediments could be responsible for the deposition of small 

amounts of uranium on matrix grains, probably as amorphous U02 • This uranium would have come from interstitial 

sea water present at the time of deposition. Sea water 

contains 3 J.Lg/L of uranium under open-ocean conditions 

(Krauskopf, 1967). As conditions in the sediment became 

reducing, U+ 6 would have been converted to a lower 

oxidation state and precipitated. As temperatures rose in the 

sediment because of subsidence, amorphous uo2 probably 

became converted to crystalline U02 . Silica (Si02) from 

dissolution of quartz grains and silicate minerals also 

increased in the interstitial solution as a result of the rising 

temperature. According to Langmuir (1978), thermodynamic data suggest that under such conditions, USi04 

should be the stable phase, so the final reaction would be 

conversion of crystalline U02 to USi04 on the matrix grain 

surface. The kinetics of this final reaction are not well 

known, and, for lower temperatures, U02 and USi04 are 

commonly found to coexist in sedimentary uranium deposits (Brookins, 197 5). It would appear from the results of the 

314 Field Studies of Radon in Rocks, Soils, and Water 

geochemical modeling that both solid phases are close to 

equilibrium with dissolved uranium; hence, either mineral 

could be present (Kraemer and Kharaka, 1986). 

As shown in table 61, all uranium activity ratios 

(UAR) are within the range 1.06 to 1.69. Kraemer (1981) 

and Andrews (1983), among others, have shown, however, 

that the UAR of ground waters should be significantly 

affected by a process known as alpha-particle recoil, where 

uranium-234 e34U) becomes enriched in solution through 

the ejection of uranium-238 e38U) daughter atoms from the 

matrix as a result of alpha decay. Such a process can, 

theoretically, result in UAR of formation waters in excess 

of 20, and high values have been reported in the literature 

(Osmond and Cowart, 1976, 1982). The slightly elevated 

UAR in these deep formation waters probably result from 

the equilibration of dissolved uranium with uranium minerals and uranium recoiled from the matrix grains. 

These released 234U atoms would enter the formation 

water, but, before the large excess activities of 234U 

predicted by theory could build up, the 234U would participate in the equilibrium exchange between solid-phase and 

dissolved-phase uranium. The equilibrium UAR for the 

formation water then would be controlled not only by the 234U being supplied by alpha recoil effects but also by the 

total amount of uranium in the uranium-mineral phase and 

the liquid phase. Isotopically, this reequilibration would 

keep the UAR lower than if no solid-phase uranium were 

present, because much of the solid-phase uranium is 238U. 

The greater the amount of precipitated-phase uranium in 

relation to the 234U being added to solution by recoil effects, 

the nearer the UAR of the solution will be to unity. 

It appears that enough alpha-recoil-generated 234U is 

being introduced into the dissolved uranium-precipitated 

uranium system to cause a slight elevation of the UAR. It 

also appears that very high U AR are not likely to be found 

in deep, high-temperature formation waters of this type, 

because of the unusual circumstances that would be 

required, such as the presence of uranium-rich sand grains, 

extremely small grain size, or the absence of a solid 

uranium mineral with which to reequilibrate. 

Kraemer and Kharaka's (1986) finding of slightly 

elevated UAR and near equilibrium of waters with U02 or 

USi04 in the formation water produced by every well 

sampled indicates that alpha-recoil reequilibration with 

solid uranium minerals is widespread in the Gulf Coast. 

Formation water from oil and gas wells similarly has 

slightly elevated UAR (Osmond and Cowart, 1982). The 

overall process described above also may be common to 

other geothermal aquifers. For example, Osmond and 

Cowart (1976) report finding low uranium concentrations 

and slightly elevated UAR in other geothermal systems, 

including the Yellowstone, Imperial Valley, and Mt. Lassen geothermal areas. 
(/) 

z 

0 

i= 

<( 

ffiffi 

~!= z....l 

!Qffi 

Cl(l. 

LL W 

01-

a:=> 

w~ 

m~ 

~a: =>w 

ZCl. 

:i 

5 

0 

<( 

a: 

10,000 

1,000 

100 

10 

• 

• 

l!l 

l!l 

0.1 ~--'----l..--'----'--L....l...~'------'--....l--'-..L-..1.-'-~ 

10,000 100,000 1,000,000 

SALINITY, IN MILLIGRAMS PER LITER 

Figure 133. The radium and salinity relation in formation 

water from the U.S. Gulf Coast. Solid squares represent 

samples from geopressured-geothermal well tests 

conducted by the Department of Energy, and the other 

squares represent samples from aquifers that have coproduced oil or gas or both (from Kraemer and Reid, 1984). 

RADIUM 

Radium in Gulf Coast formation water is present in 

variable amounts, depending on the salinity of the formation water. Kraemer and Reid ( 1984) have shown that a 

correlation exists between salinity of formation water and 

radium activity that persists over a range of dissolved solids 

from 10,000 mg/L (milligrams per liter) to greater than 

250,000 mg/L (fig. 133). The best correlation is for the 

geopressured-geothermal wells, which, as described earlier, 

are the best sources of samples; however, the correlation 

remains strong even if samples from oil and gas wells are 

included. 

Because all radium isotopes are radioactive and the 

bulk of the radium in formation water is unsupported by its 

longer lived parents in solution, the formation water must 

continually be replenished in radium to replace the radium 

that decays. Because of its chemistry, radium is soluble in 

formation waters as long as the sulfate (SO~) concentration is low. When formed by decay of previously existing 

nuclides within the matrix grains, radium can undergo a 

transfer from the solid to the liquid in accordance with the 

new chemistry. The radium also can be transferred to the 

liquid phase by alpha-recoil processes similar to those 

affecting uranium. 

It can be demonstrated convincingly that radium is 

being leached from the aquifer matrix into solution if the 228Ra/226Ra (radium-228/radium-226) activities of the formation water are compared with the Th/U (thorium/ 

uranium) activity ratios of the matrix, as shown in table 62. 

As thorium and uranium decay to 228Ra and 226Ra, respecTable 62. Comparison of radium-228/radium-226 activity 

ratios of formation water with thorium/uranium activity 

ratios of the host matrix 

[From Kraemer, 1985; 228Ra, radium-228; 226Ra, radium-226; Th, 

thorium; U, uranium] 

Well 

2 Pleasant Bayou ............ . 

1 Sweezy ................... . 

1 Amoco Fee (zone 3) ....... . 

1 McCall (zone 8) ........... . 

Formation water 228Ra/226Ra Matrix Th/U 

activity ratio activity ratio 

0.9 

1.2 

.8 

.6 

1.4 

1.7 

.9 

1.3 

tively, the formation water will remove some fraction of the 

radium, but the relative activities of the two radium isotopes 

removed will be the same as the relative activities of their 

ultimate parents. Therefore, radium isotopic activities of 

formation water should reflect the Th/U activity ratios of the 

aquifer. In most cases, the two activity ratios agree (table 

62), although there is a tendency for the formation-water 

ratios to be less than the parental ratios in the matrix. This 

tendency may be the result of the alpha-recoil process, 

because during decay, the 238U atoms undergo three alpha 

decays before becoming 226Ra, whereas the 232Th atoms 

undergo only one alpha decay before becoming 228Ra. 

Thus, the 226Ra atom has three times as many chances as 228Ra to end up in the water phase. 

The relation that exists between radium content of the 

formation water and salinity of the water must be chemical. 

Kraemer and Reid ( 1984) suggest the following possible 

controls on the relation between radium and salinity. 

1. Ion exchange. In this process, the clay minerals in the 

formation control the radium content of the water by 

adsorbing more divalent cations (including radium) at 

lower salinity. The clay minerals are less efficient at 

adsorbing divalent cations at higher salinities, where 

Na + and other univalent cations are more abundant and 

compete more effectively for the clay exchange sites. 

2. Barite equilibration. In formation waters of low ionic 

strength, the concentration of barium is usually low. 

Radium, because of its close chemical similarity to 

barium, could become involved in the equilibration 

process with solid-phase barium to a greater extent than 

in solutions of higher ionic strength, where barium is 

generally in much higher concentration. This process, 

however, was not considered likely, because in most 

cases, no barite (BaS04 ) is reported in Gulf Coast 

sediments, and formation waters from these formations 

are usually undersaturated with respect to BaS04 . 

3. Chloride-ion complexing. At the time Kraemer and 

Reid (1984) published their data, no estimates of 

chloride (C1-) complexing of radium were known, 

although they suggested this complexing as a possibility in explaining the relation between radium and 

Uranium, Radium, and Radon in Deeply Buried Sediments of the U.S. Gulf Coast 315 
salinity. Langmuir and Riese ( 1985) subsequently published a paper that discussed the thermodynamic properties of radium and estimated formation constants of 

various radium complexes. If their data are used for the 

RaCl + complex, it can be estimated that the complexing of radium by the chloride ion, although possible, is 

not sufficient to explain satisfactorily the relation 

shown in figure 133. 

4. Chloride-ion influence on silicate-solution equilibration. The continuous reequilibration of silica between 

solution and grain surface is capable of freeing radium 

atoms from the solid matrix and delivering them to 

solution. The greater the salinity of the formation 

water, the more effective the solution is at removing 

radium from the solid matrix material. The result is 

represented in figure 133. Kraemer and Reid (1984) 

hypothesize that the process responsible for the 

liberation of radium from matrix to solution is the 

continuous exchange of Si02 between silicate grains 

and solution. As the outer shell around a matrix grain is 

continually rehomogenized with Si02 from solution, 

any radium atoms exposed during the process are free 

to escape into and remain in the solution. Kraemer and 

Reid ( 1984) hypothesize that the presence of Cl- in the 

formation water accelerates the rate at which Si02 

exchanges between solution and matrix. The higher the 

Cl- content, the more rapid the exchange, the result of 

which is a faster rate of "uncovering" of radium atoms. 

Radium atoms are allowed a faster rate of entry into 

solution, so a larger "standing crop" of radium exists in 

solution (not a continuously increasing amount, 

inasmuch as the radium atoms are also decaying in 

solution) in higher salinity water than in lower salinity 

water. 

RADON 

Radon is a decay product of radium. One isotope, 222Rn, has a half-life of 3.8 days and is the daughter of 226Ra. It commonly is found in subsurface voids, such as 

pore spaces and fractures, where it accumulates because of 

its noble-gas character. Two other isotopes of radon exist 

naturally, 220Rn and 219Rn, but their half-lives are so short 

that it is difficult to measure them or interpret their 

distribution patterns. 

Radon (as 222Rn) was measured in natural gas wells 

(table 63) and in gas produced from geopressuredgeothermal wells (table 64) where the gas was extracted 

from solution at the surface (Kraemer, 1986). The radon in 

free gas from the natural-gas wells is quite low, averaging 

only 1. 8 pCi/L (picocuries per liter) at standard temperature 

and pressure (STP). In fact, this figure is well below the 

average of 37 pCi/L found by Johnson and others (1973) in 

a survey of gas produced from the various gas-producing 

316 Field Studies of Radon in Rocks, Soils, and Water 

Table 63. Radon activity in conventional gas at well head 

in the U.S. Gulf Coast 

[From Kraemer, 1986; 222Rn, radon-222; STP, standard temperature and 

pressure] 

Well 222Rn, in picocuries Depth, Louisiana 

per liter at STP in meters1 parish 

1 Gayle ........... 0.7 4,973 Vermilion. 

1 Hardee .......... .8 4,878 Vermilion. 

1 Broussard ........ 1.0 5,180 Vermilion. 

S.L. 3057 no. 30 ... 2.2 4,546 Vermilion. 

S.L. 3057 no. 22 ... .8 4,512 Vermilion. 

S.L. 3055 no. 5 .... 2.9 4,489 Vermilion. 

1 Dartez ·········· 3.4 5,930 Vermilion. 

1 Hulin •••••••••• 0 .5 6,425 Vermilion. 

1 Landry .......... 2.2 4,396 Lafayette. 

2 McConnel ....... 5.8 3,424 Lafayette. 

1 McConnel •••• 0 0 0 1.2 3,575 Lafayette. 

1 Melancon ........ 3.4 3,891 Acadia. 

1 Guilbeau ........ 3.5 3,000 Lafayette. 

B-1 Hebert •••• 0 ••• 3.6 4,725 Lafayette. 

B-1 Blanchard ..... <.5 4,021 Lafayette. 

White Lake 40 ..... 1.0 4,553 Vermilion. 

2 Humble Fee ...... 2.5 4,935 Vermilion. 

4 Hardee .......... .8 4,860 Vermilion. 

LeJeune ........... .7 4,960 Vermilion. 

3 Hardee .......... .5 4,805 Vermilion. 

I Green ........... 1.0 5,146 Vermilion. 

3 McConnel ....... 2.8 4,725 Lafayette. 

Average ........ 1.8 

1

Depths below land-surface datum. 

regions of the United States. Radon in gas extracted from 

solution from the formation waters of the geopressuredgeothermal wells (table 65) was considerably higher and 

had a larger range (13-233 pCi/L at STP) than did the free 

gas. Even this range, however, is well within the range 

found by Johnson and others (1973). 

The difference in radon activity between solution gas 

and free gas can be explained by the differing nature of the 

gas in the subsurface. As explained by Kraemer (1986), 

conventional gas deposits occur as free gas occupying space 

between matrix grains. Most of the water has been 

displaced, with usually only a small amount (30 percent or 

less of pore volume) of water remaining. Radon originating 

from the decay of radium enters this gas space and 

establishes a concentration dependent on the rate of supply 

from the liquid and solid phases and the rate of decay of 

unsupported radon within the gas. When the natural gas is 

produced from deep, hot reservoirs, it undergoes expansion 

in the range 500 to 1 ,000 times its in situ volume. Because 

the amount of radon is constant (neglecting decay) during 

expansion, its concentration (in terms of activity per unit of 

constant volume) in the gas decreases by a factor of 500 to 

1 ,000 during this expansion to surface temperature and 

pressure, so the result is low radon activity per unit volume 

of gas. 
Table 64. Radon activity in geopressured solution gas at 

well head in the U.S. Gulf Coast 

[From Kraemer, 1986; 222Rn, radium-222; pCi/L; picocuries per liter; 

STP, standard temperature and pressure; La., Louisiana; Tex., Texas] 

Well 

222Rn, in Depth, Parish State pCi/L at STP in meters 1 or county 

1 Sutter .... .. .. . . . . 233 4,834 St. Mary La . 

2 Simon ............ 96 4,450 Vermilion La. 

2 Ple:asant Bayou .... 158 4,473 Brazoria Tex. 

1 Girouard .......... 46 4,511 Lafayette La. 

1 Prairie Canal . . . . 0. 58 4,511 Calcasieu La . 

2 Zellerbach ........ 34 5,105 Livingston La. 

1 Saldana . . . .. . . . . . 13 2,984 Zapata Tex. 

1 Koelemay ......... 30-119 3,567 Jefferson Tex. 

1 Amoco Fee (zone 5) . 127 4,694 Cameron La. 

1 Amoco Fee (zone 3) . 114 4,654 Cameron La. 

1 Sweezy ........... 95 4,079 Lafayette La. 

1 McCall (zone 9) . . . 55 4,738 Cameron La . 

1 McCall (zone 8) . . . 41 4,665 Cameron La . 

Average .......... 96 

1

Depths below land-surface datum. 

In a geopressured solution-gas reservoir, however, 

the same amount of radon is "stored" in the liquid phase. 

When the brine is withdrawn from the aquifer and brought 

to the surface, the radon is scavenged by the comparatively 

small amounts of natural gas exsolving from solution as a 

result of pressure and temperature reduction. Hence, the 

final activity of radon is much higher in this type of gas at 

surface conditions than in conventional gas. 

Table 65 shows radium and radon activity in 

geopressured-geothermal wells in a unit volume of formation water. It can be seen from this table that, for formation 

waters containing less than about 95,000 mg/L total dissolved solids, the activity of 222Rn in the water is greater 

than the activity of its parent, 226Ra, in the water. The 

explanation is probably that most of the radium is physically 

located on or within the solid matrix grains and is, therefore, immobile, whereas the daughter product of the decay, 222Rn, a noble gas, migrates with ease from the surfaces or 

even interior of the grains to the interstitial fluid. There it 

builds up to some equilibrium amount on the basis of its rate 

of supply from the solid material. 

At or above a salinity of 95,000 mg/L total dissolved 

solids, the situation changes. At these salinities, in most 

cases, the amount of 226Ra in the formation water is 

sufficient to supply the total amount of 222Rn found. In 

other words, the radon is supported by the radium in 

solution, a rather unusual case for ground waters. The 

values of less than 1.0 for the 222Rn/226Ra activity ratios for 

some wells probably reflect incomplete extraction of radon 

from the brine or slightly inaccurate gas- or waterproduction measurements, which, of course, could affect 

the other wells as well. 

Apparently, in these high-salinity formation waters, 

leaching of the matrix grains is sufficient to remove radium 

Table 65. Radon and radium activity in formation water 

produced from geopressured-geothermal test wells 

[From Kraemer, 1985; 222Rn, radon-222; 226Ra, radium-226; mg/L, 

milligrams per liter; pCi/L, picocuries per liter] 

Well 

A . 226Ra, 222Rn, 222Rn/226Ra 

pproxlmate dissolved dissolved actl.vl·ty salinity 

(mg/L) (pCi/L (pCi/L ratio 

of water) of water) 

1 Sutter ............ 190,000 784 945 1.20 

1 Amoco Fee (zone 5). 165,000 631 452 .72 

1 Amoco Fee (zone 3) . 165,000 509 405 .80 

2 Pleasant Bayou . ... 132,000 692 619 .89 

1 McCall (zone 9) . .. 95,000 233 235 1.01 

1 McCall (zone 8) . .. 95,000 201 209 1.04 

1 Sweezy ........... 95,000 190 338 1.78 

1 Prairie Canal • ••• 0. 42,600 101 465 4.61 

2 Zellerbach . ....... 36,000 56 180 3.23 

1 Girouard .......... 23,750 32 368 11.4 

1 Koelemay ......... 15,300 10 637 61.5 

2 Saldana • •••••••• 0 12,800 32 71 2.26 

from a depth within each grain equal to or greater than that 

which radon could diffuse had the radium remained in the 

matrix. Thus, all of the radium that would have supported 

the radon in solution is now in solution itself. It is surmised 

that a very active process is occurring between the aqueous 

and solid-phase surfaces that continually and rapidly 

extracts radium from the outer regions of the matrix grains 

to a depth of several micrometers. The process cannot be a 

simple dissolution of the sand grains, because all these 

waters are in equilibrium with Si02 , and dissolution would 

have long since ceased. The process is not understood at 

this time. Kraemer and Reid ( 1984) suggest that Cl- may 

act as a catalyst in the movement of silica between solid 

phase and solution by preventing the hydrolysis product 

Si(OH)4 from building up on the surfaces of the mineral 

grains. This action of the ion would tend to reduce the silica 

exchange rate. 

CONCLUSIONS 

1. Uranium is present in low concentrations in formation 

waters of clastic sediments of the U.S. Gulf Coast. 

Uranium in solution seems to be in chemical equilibrium with a solid phase of either uraninite or coffinite. 

The uranium isotopic-activity ratios support this conclusion. 

2. Radium in solution in these formation waters is present 

in activities related to the salinity of the formation 

water. The higher the salinity, the greater the activity 

of 226Ra. This relation indicates a continuous interaction of formation water with the matrix, and the result 

is the extraction of radium. The intensity of the 

reaction, and hence the activity of radium in solution, 

is proportional to the salinity of the formation water. 

3. Radon is present in these formation waters and natural 

gases. At low salinities, 222Rn is present in excess of 

Uranium, Radium, and Radon in Deeply Buried Sediments of the U.S. Gulf Coast 317 
the radium in solution. The excess radon in solution is 

the result of exhalation from the aquifer rock. In 

formation waters having greater than 95,000 mg/L total 

dissolved solids, however, the amount of 222Rn activity 

present in solution is nearly equal to the amount of 226Ra activity present in solution, a situation that once 

again indicates continuous removal of radium from the 

matrix grains. The exact mechanism for this removal is 

not known. 

REFERENCES CITED 

Andrews, J.N., 1983, Dissolved radioelements and inert gases in 

geothermal investigations: Geothermics, v. 12, p. 67-82. 

Brookins, D.O., 1975, Coffinite-uraninite stability relations in 

Grants .Mineral Belt, New Mexico [abs.]: American Association of Petroleum Geologists Bulletin, v. 59, p. 905. 

Burst, J.F., 1969, Diagenesis of Gulf Coast clayey sediments and 

its possible relation to petroleum migration: American Association of Petroleum Geologists Bulletin, v. 53, p. 73-93. 

Hardin, G.C., 1962, Notes on Cenozoic sedimentation in the Gulf 

Coast geosyncline, U.S.A., in Rainwater, E.H., and Zingula, R.A., eds., Geology of the Gulf Coast and central 

Texas: Houston, Tex., Houston Geological Society, 15 p. 

Johnson, R.H., Jr., Bernhardt, D.E., Nelson, N.S., Calley, 

H. W., Jr., 1973, Assessment of potential radiological health 

effects from radon in natural gas: Environmental Protection 

Agency Report 520-1-73-004, 60 p. 

Jones, P.H., 1969, Hydrology of Neogene deposits in the Northem Gulf of Mexico basin: Louisiana Water Resources 

Research Institute Bulletin, GT-2, 105 p. 

Kharaka, Y.K., Brown, P.M., and Carothers, W.W., 1978, 

Chemistry of waters in the geopressured zone from coastal 

Louisiana-Implications for the geothermal development: 

318 Field Studies of Radon in Rocks, Soils, and Water 

Proceedings of the Geothermal Resources Council 1978 

Annual Meeting, v. 2, p. 371-374. 

Kraemer, T.F., 1981, 234U and 238U concentration in brine from 

geopressured aquifers of the northern Gulf of Mexico basin: 

Earth and Planetary Science Letters, v. 56, p. 210-216. 

---1985, Natural radioelement behavior in geopressured aquifers, in Dorfman, M.H., and Morton, R.A., eds., Proceedings of the Sixth U.S. Gulf Coast Geopressured-Geothermal 

Energy Conference: New York, N.Y., Pergamon Press, p. 

127-136. 

---1986, Radon in unconventional natural gas from Gulf 

Coast geopressured-geothermal reservoirs: Environmental 

Science and Technology, v. 20, no. 9, p. 939-942. 

Kraemer, T.F., and Kharaka, Y.K., 1986, Uranium geochemistry 

in geopressured-geothermal aquifers of the U.S. Gulf Coast: 

Geochimica et Cosmochimica Acta, v. 50, no. 6, p. 

1233-1238. 

Kraemer, T.F., and Reid, D.F., 1984, The occurrence and 

behavior of radium in saline formation water of the U.S. Gulf 

Coast region: Isotope Geoscience, v. 2, p. 153-174. 

Krauskopf, K.B., 1967, Introduction to geochemistry: New York, 

N.Y., McGraw-Hill, 721 p. 

Langmuir, D., 1978, Uranium solution-mineral equilibria at low 

temperatures with applications to sedimentary ore deposits: 

Geochimica et Cosmochimica Acta, v. 42, p. 547-569. 

Langmuir, D., and Riese, A., 1985, The thermodynamic properties of radium: Geochimica et Cosmochimica Acta, v. 49, p. 

1593-1601. 

Osmond, J.K., and Cowart, J.B., 1976, The theory and uses of 

natural uranium isotopic variations in hydrology: Atomic 

Energy Review, v. 14, p. 621-679. 

---1982, Ground water, in Ivanovich, M., and Harmon, R.S., 

eds., Uranium series disequilibrium-Applications to environmental problems: Oxford, England, Clarendon Press, 

Chap. 9, p. 202-245. 

White, D.E., 1965, Saline water of sedimentary rocks, in Young, 

A., and Galley, J., eds., Fluids in the subsurface environment: American Association of Petroleum Geologists Memoir 4, p. 342-366. 
RADON, HELIUM, AND OTHER GASES IN SHALLOW GROUND WATERS OF 

URANIFEROUS HOLOCENE ALLUVIUM, FLODELLE CREEK, STEVENS COUNTY, 

NORTHEAST WASHINGTON 

Jarnes K. Otton and G.M. Reimer 

Abstract 

Shallow ground waters from highly uraniferous late 

Pleistocene and Holocene valley fill sediments along the 

north fork of Flodelle Creek in Stevens County, Wash., 

were sampled in shallow holes dug in the valley floor and 

permitted to fill with water drained from the sediment. 

Springs on the hillslope above the valley floor and on the 

bottom of the valley floor were sampled also. Dissolved 

gases in the water samples were analyzed for radon, 

helium, oxygen, carbon dioxide, and methane. 

Radon concentrations in the shallow ground waters 

of the valley floor are 2 to 3 orders of magnitude less than 

those expected for uranium deposits of similar grade 

because the uranium has not been in place long enough 

for secular equilibrium to be established between it and 

its decay products in these sediments. Radon concentrations in the ground waters in contact with the bedrock and 

overlying glacial till of the hillslopes of the catchment are 

greater than those in the uraniferous sediment of the 

valley floor, except where bedrock ground waters appear 

to be upwelling into the valley-floor sediment column. 

Measuring radon in the shallow ground water of drainages 

such as these is not a good method for searching for 

surficial uranium deposits but may be useful in determining ground-water flow paths in the catchment basin. 

The ground waters in the drainage basin show characteristic values of radon, helium, oxygen, carbon dioxide, and methane controlled by the environment in which 

the waters occur or have recently traveled through. Stagnant waters from the sediment of a beaver pond in the 

upper part of the study area are high in carbon dioxide 

and methane because the organic matter in the sediment 

column has been oxidized and biogenically degraded. 

These waters are low in helium and radon as a result of 

dilution of these gases by addition of the biogenic gases 

and depletion by bubbling of carbon dioxide and methane 

through the sediment column. Ground waters from 

springs on the hillslopes are high in oxygen but relatively 

low in carbon dioxide and methane because the waters 

have limited contact with thin soil horizons and organic 

matter. Such waters are high in radon and helium derived 

from recent contact with uranium-rich weathered bedrock 

(where uranium approaches secular equilibrium with its 

decay products) and sandy glacial till derived largely from 

bedrock material. "Normal" ground waters in the sediment filling the valley floor contain modest amounts of 

radon, helium, oxygen, carbon dioxide, and methane 

because the waters have recent contact with biologically 

active, uraniferous sediment in the upper part of the 

sediment column of the valley floor. Because ground 

waters in a zone of upwelling along the valley floor are 

very low in oxygen, carbon dioxide, and methane, but 

very high in radon and helium, a bedrock source is 

suggested, possibly a fracture zone that intercepts the 

valley floor. 

INTRODUCTION 

Late Quaternary organic-rich alluvium along the valley floor of the north fork of Flodelle Creek in eastern 

Stevens County, Wash. (fig. 134), is highly enriched in 

uranium. Mining of a section of the valley floor began in 

September of 1983, and about 1,000 pounds of uranium 

were recovered prior to cessation of operations in 1985. 

Since 1983, scientists of the U.S. Geological Survey have 

studied the uraniferous sediment, the ground and surface 

waters, the bedrock, and the vegetation within the drainage 

basin of the north fork of Flodelle Creek in order to 

understand the source, movement, and entrapment of uranium in this modem, natural system. This work has resulted 

in a series of reports describing the geologic setting and 

stratigraphy of the uranium deposit (Johnson and others, 

1987); the aqueous geochemistry of the shallow ground and 

surface waters (Zielinski and others, 1987); uranium series 

disequilibrium of the sediments (Zielinski and others, 

1986); mechanisms of entrapment of uranium in the sediment (Otton and Zielinski, 1985); and the biogeochemistry 

of uranium in Douglas fir in the drainage basin (Zielinski 

and Schumann, 1987). 

This earlier work strongly suggests that uranium is 

leached from the uranium-rich quartz monzonite bedrock of 

the drainage basin, is carried by oxidized ground waters, 

and then is trapped by adsorption on organic matter in the 

shallowest parts of the sediment column. Uranium mineralization has occurred continuously since ice departed the 

area about 12,500 years ago and organic-rich sediment first 

began to accumulate. Once the organic-rich sediment 

becomes compacted and less permeable (below about 1 m 

(meter) in depth), the sediment appears to be closed with 

respect to uranium addition or loss except where more 

permeable layers, such as coarse sands at the base, occur. 

Gross disequilibrium occurs within these sediments: the 

content of radioactive decay products (specifically radium226) increases from 1 percent of that expected under 

conditions of secular equilibrium at the surface to about 10 

percent near the base of the mineralized sediment column. 

The sediment column near the spring pool (S4) near site 

WR14 (see fig. 135C) shows excess activity of lead-210 

Radon, Helium, and Other Gases in Flodelle Creek, Washington 319 
' ' Drainage divide 0 CANADA 49 _, __ _ 

Study area I WASHINGTON ---"' ~ I ' " ~ I " 

I " I "-. 

" ' 

47° 

30'~~------------~~--~----~ 

/ 

/ 

.5 

0 

I I-~ 

.5 1 I 

2kilometers 

/ 

2miles 

I 

0 

Figure 134. Study area in the upper part of the drainage basin of the north fork of Flodelle Creek. Contour interval is 200 

feet. 

compared with radium-226. Addition of radon-222 at that 

site from a source external to the sediment column is 

suggested. 

Surface outcrop samples of the quartz monzonite in 

the drainage average 5. 9 ppm (parts per million) uranium, 

whereas bedrock core from the drainage averages 15.8 ppm 

uranium (J.K. Otton, unpub. data, 1986). The near surface 

rocks have lost about 10 ppm uranium evidently attributable 

to physical and chemical weathering since deglaciation. 

Spring waters, surface waters, and shallow ground waters 

from the sediment column contain 17 to 318 ppb (parts per 

billion) uranium because the uranium has been leached from 

the rocks and is mobile in these waters. 

In the summers of 1985 and 1986, we sampled 

shallow ground waters in the upper 0.9 km (kilometer) of 

the drainage basin in reconnaissance fashion and measured 

the dissolved radon, helium, carbon dioxide, oxygen, and 

methane contained in those waters (Sites WR1 to WR16, 

fig. 135). The objective of the study was to test a method 

for sampling dissolved gases in shallow ground water, to 

characterize the radiogenic and other gases dissolved in the 

shallow ground waters of this uranium deposit, to compare 

the dissolved gas content of the various types of waters 

found along the drainage, and to compare helium and radon 

content of the shallow ground waters to the uranium content 

of the subjacent sedimentary column. We wanted to under320 Field Studies of Radon in Rocks, Soils, and Water 

stand the source and movement of radiogenic gases in the 

ground-water system and the probable pathways of groundwater movement. 

CHEMISTRY OF RADON AND HELIUM 

Radon-222 has a 3.823 day half-life, whereas its 

immediate precursor, radium-226, has a 1,623 year halflife. Radium and its precursor, thorium-230, are not very 

soluble in most natural waters. Where thorium-230 is 

formed by radioactive decay of uranium-234 in the water, it 

is readily sorbed onto various solid components of rocks 

and organic-rich sediment. Radium-226 also is sorbed 

readily or is coprecipitated with various mineral species. 

Thus the radon concentrations observed in waters are 

generally proportional to the radium content of the rocks 

and sediments in recent contact with the water and not of the 

water itself. 

Radon readily degasses from water with agitation 

(during turbulent stream flow, for example) or with gas 

streaming through a sample (which forms the basis for the 

sampling technique used here and sampling techniques 

developed by others). Under equilibrium conditions, the 

ratio of the radon concentration in the water phase to the 

radon concentration in the gas phase of a gas-water system 

ranges downward from about 0.5 at 0 octo 0.15 near 45 oc 

(Rogers, 1958). 
The present-day atmospheric concentration of helium 

is 5,240 ppb. The helium content of water in equilibrium 

with the atmosphere at STP (standard temperature and 

pressure, 25 oc and 1 atmosphere) is 45 x 10-9 cm3 of 

helium per cubic centimeter of H20. For shallow ground 

waters recently in contact with the atmosphere, values 

lower than this indicate additions of other gases to the 

dissolved gas load. Gases derived from the oxidation of 

organic matter or the respiration of biota in the soil of the 

hillslope and sediment of the wetland, such as carbon 

dioxide, methane, and oxygen, may lower the helium 

content of the dissolved gases by simple dilution. Losses of 

helium also may occur by bubbling of gases through a 

water-saturated sediment column. Those losses may be 

greater for helium than for other gases because helium has 

such a low atomic weight. Additions of helium from decay 

of radionuclides in rocks and soils in close contact with the 

water increase the helium content of the dissolved gases. 

Because helium is small and chemically inert, it is a 

highly mobile element. It diffuses at a rate 7 times that of 

radon. Helium readily degasses from water upon agitation 

and has a strong affinity for the gas phase in a two-phase 

(air-water) system. 

SITE DESCRIPTION 

This study was confined to the upper 0. 9 km of the 

stream valley occupied by the north fork of Flodelle Creek 

(figs. 134 and 135), and this description will focus on that 

area. For a more complete description of the entire drainage 

basin, see Johnson and others (1987). This upper part of the 

drainage basin was selected because it is essentially undisturbed by mining development, contains the highest grade 

of uraniferous sediment observed by us (as much as 0.9 

percent uranium by dry weight near Site WR14), and 

contains several valley-slope and valley-bottom springs. 

Adjacent hillslopes are underlain by quartz monzonite 

bedrock mantled by sandy glacial till; the valley floor is 

underlain by postglacial fluvial and marsh sediments. Thin 

volcanic ash-bearing loess and thin, organic-rich, poorly 

developed soils rest on the sandy till. Volcanic ash also 

occurs within the sediment column of the valley floor at 

depths of a few tens of centimeters to almost 3 m. 

A<:cumulations of organic-rich sediment extend essentially 

continuously along the valley floor in the study area from a 

small marsh a few hundred feet south of the drainage divide 

to a major tum in the valley about 0.9 km downstream (fig. 

135). 

In the upper 180-210 m of the drainage basin (fig. 

135A, Site WR1 to just south of Site WR4), the valley 

bottom is about 15 to 23m wide, slopes gently down valley 

(1 to 21f2 percent), and is occupied by continuous wetland. 

The valley initially trends south-southeast but doglegs to the 

south near Site WR3. In the lower part of this section, 

where continuous streamflow develops (about halfway 

between Sites WR2 and WR3), beavers have dammed the 

stream and ponded the valley floor. The valley bottom is 

characterized by organic-rich, highly uraniferous sediment 

0.9 to 1.5 min thickness. The water table is at or near the 

surface throughout this part of the valley floor. 

South of this section, for a distance of about 90 m, the 

valley narrows to about 9 m, changes orientation to the 

southeast, and the gradient steepens (fig. 135A, from below 

Site WR4 to Site WR6). Surface flow is confined to a 

narrow channel cut in the valley floor a few tens of 

centimeters. The valley is choked with deadfall trees. 

Scattered boulders poke up through the valley-floor sediment. Organic-rich sediment 0. 6 to 0. 9 m thick persists in 

this interval, but the abundance of organic matter decreases 

between Sites WR5 and WR6. These sediments are only 

slightly to modestly enriched in uranium (less than 1,000 

ppm). 

South of Site WR6, the valley floor abruptly widens 

(21 to 36m), and the slope decreases. Between Sites WR6 

and WR16 (fig. 135 B,C), the valley forms a broad arc and 

changes trend gradually from south-southeast to southsouthwest. The character of the valley floor alternates from 

a flat-bottomed wetland with a meandering shallow stream 

channel to gently west-sloping valley bottom with a channel 

15 to 45 em deep cut into the valley floor by the present 

stream. These latter areas lie near the mouths of side valleys 

near Sites WR8, WR9, and ~15. At these localities, 

small alluvial fans that formed at the mouth of the tributary 

drainages force the stream channel to be displaced to the 

west side of the valley floor. These alluvial fans appear to 

have partially dammed the valley floor and thus have 

created ponded zones upstream. Auger holes near these fans 

are dominated by clastic sediments (Sites WR8 and WR9, 

fig. 135B), whereas auger holes upstream contain thick 

sections of organic-rich sediment (Site WR7, fig. 135B; 

Sites WR13 and WR14, fig. 135C). The alluvial fans have 

subsequently been cut by the channel in which the modem 

stream flows. The sediments in this part of the valley floor 

are variably enriched in uranium and have no particularly 

good correlation between the presence of organic matter and 

the presence of uranium. 

Previous hydrologic studies of watershed areas 

(Freeze, 1972; Freeze and Cherry, 1979) and studies of 

Douglas fir that sample shallow ground waters in this basin 

(Zielinski and Schumann, 1987) suggest that the principal 

movement of ground water on the hillslopes in this drainage 

basin occurs as interflow along the contact between the 

highly permeable sandy glacial till and the underlying much 

less permeable quartz monzonite bedrock. Logging roadcuts show that the depth of the sandy till is in the range of 

0 to 1. 5 m on the west side of the drainage and 0 to 0. 9 m 

or more on the east side. These roadcuts also show that the 

upper 2 or 3 m of the quartz monzonite has undergone rapid 

physical and chemical weathering since deglaciation. Outcrops and core show that the bedrock is highly fractured 

Radon, Helium, and Other Gases in Flodelle Creek, Washington 321 
WR1 

Lithology 

U~aniu~ Org. C ( %) 

\ ~op- ' \ 

Valley51 slope 

~ spring 

Valley slope 

Key to 

Lithology 

* Usually occurs as a 

corrponent cl other sediment. 

WR6 

Lithology 

V•••N-• 

1. ~-:~:-~.:~_:; 

2 .·.·.·_....,_-::: 

3 ~:-:-:c.-::-::~ 

------ 4 

5 

11 ~~~~-. 2 -··-·" 

_,...,_~_-

3 ~ .. -:;. .:.;~_-:-_ 

WR2 

Lithology 

Uranium 

(ppm> 

WR3 

0 4000 10 30 50 

Figure 135. Plan maps of the study area in the 

upper part of the drainage of the north fork of 

Flodelle Creek. See figure 134 for location. Maps 

show location of shallow holes sampled for 

ground water and lithologic logs and geochemical data for auger holes taken at the same sites. 

322 Field Studies of Radon in Rocks, Soils, and Water 

Uranium 

(ppm) 

0 4000 

5 :'?~:·.:: 6 ....... o• 

WRS 

Org. C (%) 

0 50 100 

feet 

Uranium 

o (ppm> 4000 

Uranium Org. C (%) 

o (ppm) 4000 10 30 50 

Uranium 

Lithology (ppm) Org. C (%) 

rf7 

Maps also show sample sites for the slope 

springs, the valley bottom spring, and the spring 

pool. All depths are in feet. Uranium values are in 

parts per million; organic carbon (Org. C) values 

are in percent. A, Upper section; B, Middle 

section; C, Lower section. 
WR7 Uranium (ppm) Org. c (%) 

Lithology o 40oo 10 30 50 

3 

4 .. ·--:=:··-::-.:-::. 

5 ----

--·--·-

7 ~-: ·. ·. ~::: ... 0 ••••• 

8 ~:.; :: ':": ~ ... ·0··· 9 . •0 .... q 

WR10 

2 

3 

Lithology 

4 -t-.:-=·.-~~-

5-,....==-..:;.....::::;.1 

6 

7 

8 

9 .. o ...... • • •• • ·0. 

10 :::o:::: . . . . .. o .. 

11 ::~:::::: 

. "'0"" 12 0 ...... 

WR11 

Figure 135.-Continued. 

-.-. I 

I 

~ 

Valley slope 

Uranium (ppm> Org. C (%) 

0 5GOO 10 30 50 

Lithology 

4 ....... . 

5~ 

6 ~~=.::=: 

7 ... ······ 8 : ~:: ~'7 :: 9 ~::::c,: 

Uranium (ppm) Org. C (%) 

0 3000 S3 

Valleyslope 

spring 

Valley slope 

-Valleyslope 

break 

Radon, Helium, and Other Gases in Flodelle Creek, Washington 323 
WR13 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

WR12 

Lithology 

12 ·::~::o: . ··0 ••.• 

13 ..... •O· 

WR14 Lithology 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 •• 0 ••.•• 

Figure 135.-Continued. 

Lithology 

Uranium (ppm) Org. C (%) 

0 3000 10 30 50 

324 Field Studies of Radon in Rocks, Soils, and Water 

Valley slope 

Valley slope 

Valley-slope break 

\ 
locally. Significant ground-water movement likely occurs 

within zones that have any significant fracture permeability. 

On the basis of the pattern of elevated uranium in Douglas 

fir twigs, the position of a slope spring, orientation of 

fracture and shear zones observed in the bedrock, and the 

north to northwesterly alignment of topographic elements in 

this basin and nearby basins, Zielinski and Schumann 

(1987) suggest that a major fracture zone parallels and lies 

directly west of this upper part of the drainage basin and 

intersects it in the lower part of the valley studied here. 

METHODS 

Sixteen water sample sites (Sites WRl to WR16, fig. 

135) were established at 61-m intervals down the axis of the 

valley floor along the upper 0. 9 km of the north Flodelle 

drainage basin starting in the wetland along the valley floor 

several tens of meters south of the drainage divide. Each 

site was selected as close to the topographic low point in the 

valley bottom as was practical, typically adjacent to flowing 

streams on the valley floor. At each site, a hole 45 em 

(centimeters) deep and 20-30 em in diameter was dug. 

Shallow ground water seeped in, and the site was left 

undisturbed overnight for 18 to 24 h (hours) to permit the 

hole to fill and for the water in the hole to equilibrate with 

the water-saturated sediment. The following day each site 

was revisited, a water sample taken, and dissolved gases 

retrieved for radon measurements. A split of each gas 

sample also was taken for later measurement of helium, 

carbon dioxide, oxygen, and methane. A hole was subsequently augered at each site, and samples on 0.3-m intervals 

were recovered for lithologic descriptions, uranium analyses (by delayed neutron activation), and loss on ignition 

(after drying 24 h at 95 oc to estimate organic-carbon 

content). At Sites WR1 and WR14, lithologic descriptions 

and uranium data from auger holes sampled during a 

previous summer's fieldwork were used. Geochemical data 

from auger holes at Sites WR15 and WR16 were not 

received in time to be included in the results reported here. 

Diffusive loss of dissolved gases from the surface of 

the water in the sample holes was expected to affect the gas 

measurements to some degree. Sequential readings of radon 

in waters of the same hole over 2 days showed a 20 percent 

drop in the second day (Site WR8, see table 66). This 

amount is within the analytical and sampling error of the 

technique. Sampling error is discussed later in this section. 

Because the holes were sampled uniformly 18 to 24 h after 

tht::y were dug, diffusive losses to the atmosphere were 

likely to be consistent and not affect the interpretation. 

Dissolved gases were recovered from the water at 

each site in a 1-L (liter) polyethylene bottle dipped into the 

water-filled hole, filled (with the minimum possible turbulence) to 0.75 L, capped, shaken for 1 min (minute), and 

allowed to rest for 1 min so all the gas bubbles could be 

exsolved. Then a gas sample was drawn from the headspace 

above the water with a 50-cm3 syringe through a septum 

fitted into the cap. 

Methods for determining the radon content were 

similar to but differed in detail between the 1985 and 1986 

sample visits. During the 1985 sampling, a 20-cm3 gas 

sample from the headspace was injected into an alphasensitive scintillometer (Lucas cell) counting device and 

counted for three 1-min intervals with a 1-min delay 

between counts. The scintillometer had a modified inlet 

system to permit the sample to be injected by syringe into 

the evacuated cell (Reimer, 1977). Background counts 

taken prior to sample injection were then subtracted from 

the sample count. Next, a second 20-cm3 sample was 

injected into a 10-cm3 metal cylinder for later analyses for 

helium, carbon dioxide, oxygen, and methane. During the 

1986 sampling, we used three consecutive 2-min counts of 

the sample and a 50-cm3 sample size to get greater 

precision. In 1986, no samples were taken for analysis of 

other gases. The counts per minute for radon in the gas 

sample were then converted to radon dissolved in the water 

in picocuries per liter. The conversions assume total 

degassing of the dissolved gases from the water in the 

bottle. Sequential degassing and radon measurements on the 

same sample (G.M. Reimer, unpub. data, 1975) show that 

about 10 percent of the radon remains dissolved in the water 

at low radon concentrations ( 100 pCi/L (picocuries per 

liter)) when this procedure is used, whereas only 1 percent 

remains in the water at higher concentrations (1 ,000 pCi/L). 

The scintillometer had been calibrated previously at the 

U.S. Bureau of Mines radon generation facility at Denver, 

Colo. The calibration established a sensitivity of 25 pCi/L 

for the unit for use with our sample size and field counting 

technique in the summer of 1985 and 5 pCi/L for our 

procedure in the summer of 1986. 

Samples of a valley-bottom spring (S2, adjacent to 

Site WR3, fig. 135A), a valley-bottom spring pool (S4, 

adjacent to Site WR14, fig. 135C), and two slope springs 

(S1, on the valley slope west of Site WR2 (fig. 135A) and 

S3, just above the valley slope break between Sites WR10 

and WR11, fig. 135B) were retrieved by a procedure in 

which the mouth of the 1-L polyethylene bottle was held as 

close to the source as possible and the water sample was 

allowed to flow into the bottle with a minimum of 

turbulence. Retrieval of dissolved gases followed a 

procedure similar to that of water from the shallow holes 

described above. 

All 16 sample localities were visited between August 

19 and August 24, 1985 (table 66), and revisited July 23 

and July 24, 1986. In 1985, some sample splits were lost 

because the metal cylinders failed, and some samples were 

insufficient for complete analysis of all gases. We sampled 

the study area in late summer so that the diluting effect of 

spring runoff would be minimized; however, during the 

July 1986 visit, the water table was noticeably higher along 

Radon, Helium, and Other Gases in Flodelle Creek, Washington 325 
Table 66. Multiple measurements of radon taken at the 

same site in northeast Washington 

Date Time 

S4-Spring pool near WR14 

Aug. 19, 1985 . . . . . . . . . . 5:06 p.m. 

Aug. 20, 1985 . . . . . . . . . . 9:32 a.m. 

Aug. 23, 1985 . . . . . . . . . . 3:51 p.m. 

Aug. 24, 1985 . . . . . . . . . . 12:01 p.m. 

Radon, 

in picocuries 

per liter 

2,175 

1,875 

1,825 

2,700 

2,150±400 average 

WR2-Shallow ground water 

Aug. 23, 1985 . . . . . . . . . . 9:23 a.m. 775 

Aug. 23, 1985 . . . . . . . . . . 9:33 a.m. 825 

WRS-Shallow ground water 

(hole dug Aug. 22, 1985, about 6 p.m.) 

Aug. 23, 1985 . . . . . . . . . . 12:47 p.m. 1,825 

Aug. 24, 1985 . . . . . . . . . . 9:25 a.m. 1,425 

the valley floor than during the August 1985 sampling. The 

higher water table affected our sampling in ways described 

in the following section. 

Helium analyses were made in laboratory facilities in 

Denver, Colo., by use of a mass spectrometer. The helium 

data are reported in parts per billion helium for the helium 

content of the gas in the headspace above the water in the 

sample bottle after the bottle was shaken, rather than for 

helium content of the water itself. For the sampling method 

used here, an increase of 20 ppb above the background of 

5,240 ppb in the helium content of the air in the heads pace 

corresponds to a sevenfold increase in the helium content of 

the water in the bottle. The other gases were analyzed on a 

gas chromatograph. The gas chromatograph uses a thermal 

conductivity detector for determining the permanent gases 

and a flame ionization detector for determining hydrocarbons. Data are reported as ratios with respect to nitrogen in 

the sampled gas. Ratios for a reference gas are also reported 

for comparison. 

Sampling and operator errors in our sampling method 

may include ( 1) diffusive losses from the surface of the 

sampling holes (discussed previously); (2) gas loss or gain 

during agitation of the water sample while the sample bottle 

was being filled; (3) incomplete degassing of the water 

sample in the bottle during agitation (discussed previously); 

(4) inconsistent filling of the bottle to the same 750-mL 

volume for each water sample; (5) variations in the gas 

pressure in the headspace after the sample was degassed; 

and (6) inconsistent extraction of the same volume of gas 

sample. The percent error introduced likely varies from gas 

to gas. Some errors are systematic and produce values that 

are consistently lower than expected, while others are 

random. We estimate the random sources of sampling and 

operator error to be about 20 to 30 percent. 

326 Field Studies of Radon in Rocks, Soils, and Water 

RESULTS AND DISCUSSION 

Radon in the Shallow Ground-Water Samples 

The radon content of shallow ground-water samples 

along the upper part of the north fork of Flodelle Creek 

ranged from about 50 pCi/L for Site WR7 to 8,700 pCi/L 

for Site WR13 (both in 1985, table 67, fig. 136) .. This range 

is in the same order of magnitude as those values observed 

in studies of springs (but not streams) draining unmineralized Paleozoic sedimentary and Precambrian crystalline 

rocks in the Wasatch Mountains of Utah (43 to 4,730 pCi/L 

in spring waters, Rogers, 1958) and for ground waters in 

two south-central Utah basins (70 to 8,800 pCi/L in wells 

and springs, McHugh and Miller, 1982). But the range 

along Flodelle Creek is 1 to 2 orders of magnitude lower 

than ranges observed in private and small public water 

supplies derived from granitic rocks in Maine (Brutsaert and 

others, 1981) and 2 to 3 orders of magnitude lower than 

radon measured in water-supply wells in the Helsinki, 

Finland, metropolitan area (10,000 to 880,000 pCi/L, 

Asikainen and Kahlos, 1979). Moreover, these values are 2 

to 3 orders of magnitude less than those observed in waters 

in contact with uranium deposits of this grade, 23,000 to 

1,600,000 pCi/L in uranium mine waters at Elliot Lake, 

Ontario (Dyck and Jonasson, 1977). These overall lowerthan-expected values are due to the extreme youth and gross 

disequilibrium found in this uranium deposit (Zielinski and 

others, 1986). Thus, measurement of radon in shallow 

ground waters is not expected to be an effective exploration 

tool in searching for this type of uranium occurrence. 

Observed radon levels for the sampling in 1986 were 

consistently lower than those in 1985. Precipitous drops in 

the year-to-year sampling were observed at Sites WR1, 

WR3, WR4, WR5, and WR14; for example, WR1 dropped 

from 3,500 pCi/L in 1985 to 960 pCi/L in 1986. The 1986 

sampling occurred earlier in the summer than the 1985 

sampling, the water table was noticeably higher, and at 

these holes the water levels were above the surface of the 

ground in 1986. We attribute these precipitous drops in 

radon content in 1986 to the draining of the surface layer of 

radon-poor water into the hole after digging. We attribute 

the overall lower 1986 readings to greater dilution of more 

radon-rich base flow by radon-poor surface runoff from the 

previous spring snowmelt. At Site WR6, the 1985 hole was 

dry when revisited the following day, so we took a stream 

water sample instead, and it contained 200 pCi/L radon. 

The following year we dug a hole in the adjacent streamchannel bottom to obtain a sample, and it contained 1,095 

pCi/L. Because of such sampling problems in 1986, we 

consider the 1985 dataset to be a more reliable estimate of 

the shallow ground-water radon concentrations at the time 

of sampling. 
Table 67. Measurements of radon and helium in shallow ground waters in northeast Washington 

[All radon data are in picocuries per liter; all helium data are in parts per billion; NS, not sampled; ND, analytical data not received in time for this study; 

lost, sample lost from container prior to analysis] 

Sample site 1985 1986 Calculated 1985 1986 Calculated 

Rn Rn Rn yield He He He yield 

WR1 .................................... 3,500 960 3,900 5,320 5,100 10,000 

WR2 .................................... 800 1,055 2,950 5,250 5,110 8,840 

WR3 .................................... 425 75 1,350 5,010 4,960 6,920 

WR4 .... ·················· .............. 1,700 255 3,850 5,230 5,260 9,950 

WR5 .................................... 800 225 1,000 5,290 5,140 6,470 

WR6 .................................... 1

200 1,095 5,850 5,310 5,180 12,410 

WR7 .................................... 50 160 150 5,250 5,310 5,440 

WR8 .................................... 1,825 1,500 2,200 5,330 4,980 7,930 

WR9 .................................... 2,050 1,295 2,750 5,210 5,260 8,600 

WR10 ................................... 1,125 1,040 2,150 5,310 5,310 7,890 

WR11 ................................... 300 330 1,850 lost 5,100 7,510 

WR12 ................................... 4,600 4,505 3,650 lost 5,050 9,770 

WR13 ................................... 8,700 7,520 6,950 5,300 5,190 13,710 

WR14 ................................... 3,700 1,705 1,350 6,860 6,580 6,900 

WR15 ................................... 3,875 NS ND 5,730 6,170 ND 

WR16 ................................... 2,375 NS ND 5,270 5,140 ND 

1

This sample was taken from surface water in the stream adjacent to the hole when the hole proved to be dry. 

Highest radon concentrations in the shallow ground 

water along the valley bottom occur from Site WR12 to Site 

WR16 (fig. 136, top graph). Within this section, upwelling 

ground waters are inferred from the abundance of seeps in 

the valley floor near Sites WR14 and WR15 and the 

presence of an open spring pool (S4, near Site WR14). 

Bedrock spring waters from the valley slopes (see fig. 136, 

1985, Sl and S3; table 68) have consistently higher radon 

values than adjacent valley floor waters. These observations 

suggest that ground waters in contact with the weathered 

bedrock and the overlying sandy till contain more radon 

than shallow ground waters in contact with the highly 

uraniferous valley fill. Several factors may be responsible 

for this difference: 

1. The uranium in the valley fill sediments is in gross 

disequilibrium with its radioactive decay products (the 

concentration of radioactive decay products is 1-4 

percent of that expected for the amount of uranium 

present in the shallowest parts of the sediment column); 

thus, far less radon is produced than that which would 

be expected for the uranium present in the sediment. 

2. The uranium content of the bedrock in this drainage 

basin is relatively high (5 and 15 ppm average for 

surface and core materials, respectively). 

3. The uranium in the weathered bedrock and sandy till 

probably approaches secular equilibrium with its decay 

products. With the very recent loss of uranium from the 

near surface, there may be an excess of radium with 

respect to uranium. 

4. Uranium (and radium) in the bedrock and till sources 

may tend to be concentrated on fracture and grain 

surfaces in contact with the water. This contact with 

concentrated uranium would tend to increase the apparent uranium content of the bedrock in a surface-area 

analysis and increase the fraction of radon (emanating 

power) that can escape to the water in the pores. 

Without some detailed investigations of the distribution of uranium in the bedrock and uranium series radionuclides in the bedrock and till and without comparisons of the 

emanating power of the bedrock, till, and valley-floor 

sediment, the relative effect of these factors cannot be 

evaluated. 

Radon levels in the shallow ground waters do not 

follow a pattern related in any simple way to the uranium 

content of the underlying sediment column. In order to 

evaluate this relation, we made grade X thickness ( GD 

calculations for the sample sites along the valley floor (fig. 

136). The GT calculation was developed by uranium 

geologists working with drill hole samples and gamma logs 

on the Colorado Plateau as a means of estimating and 

comparing uranium content. A 10-ft intercept of ore averaging 0. 1 percent yields a GT of 1. 0. In contrast to the 

findings of these geologists where the density of the 

sandstone ore varied only slightly, the GT calculations we 

made here have been weighted for the varying density of the 

sediment. 

Steady increases in the GTcalculation from Site WRl 

to Site WR4 are not followed by steady increases in the 

radon content of the shallow ground water. Note also that 

high GT calculations for Sites WRlO, WR13, and WR14 

(all close to 1.0) are marked by low, moderate, and high 

observed radon levels, respectively. This lack of correlation 

suggests that the radon content of the shallow ground water 

is not directly affected by the uranium (radium) present in 

Radon, Helium, and Other Gases in Flodelle Creek, Washington 327 
S1 S2 S3 S4 

10,000 I I I I 

• §ii)~ 0 "'0 cumO co ·- 5,000 

a: sa. • • 0 • • 

• • • 0 • 

0 • •o • • • • • 

10,000 

c: co...J • 

0 co:::. 5,000 ~ Ol() • a: sa. 0 

• • .o . • • • • • • . •o 0 

7,000 

E ii).o • -~ co c. 6,000 <D ~ c. :c - • 

...!. -. 9t..-. e.- Jt_. -•·-. J.-. .a...-.L.-e-. -•·-.-.-.-.-·'--.-.-.-.-. .- 5,000~--------~~------------------------------------------------------------~ 

7,000,--------------------------------------------------------------------------, 

• 6,000~-------------------------------------------------------------------------·----_, 

5,000-~·-·-·-·-·-•-·-·-·-·-·L·-·-·-•--~·-·-·-·-·-·-·-·-·-·-·- • • • • • • • • • • 

1.0,-----------------------------------------------~.~------------------•• ----------, • • 

• 0.5;-----~.~-----------------------------------------------------------------------; 

• • • • • • 

• 

Q I • 

WR1 

I I I I I I I I I I I I I I I 

WR2 WR3 WR4 WR5 WR6 WR7 WRS WR9 WR10 WR11 WR12 WR13 WR14 WR15 WR16 

Figure 136. Radon and helium data for shallow ground 

waters (Sites WR1 through WR16 represented by dots) 

and spring waters (springs 51 through 54 represented by 

open circles) from the 1985 and 1986 sampling in the 

study area. For sample site locations see figure 135. The 

relative positions of spring sample sites (51-54) are 

marked along the upper edge of the series of graphs, 

whereas the relative positions of the shallow groundSite 

water sample sites (WR1-WR16) are marked along the 

lower edge of the series of graphs. The dash-dot line on 

the helium graphs marks the helium content of air. Refer 

to text for explanation of grade X thickness calculations. 

pCi/l, picocuries per liter; ppb, parts per billion. Please 

refer to table 67 for an explanation of missing data from 

Sites WR1-WR16. Only one helium measurement for a 

spring (51, 1985) was made. 

Table 68. Radon measurements of selected spring and surface-water sample sites in northeast Washington 

[pCi/L, picocuries per liter] 

Site Description Date Time Radon (pCi/L) 

WR3 ............ Surface water from beaver pond Aug . 23, 1985 9:49a.m. 25 

WR6 .... .. ...... Surface water from stream adjacent to hole Aug . 23, 1985 11:38 a.m 225 

S1 ............... Slope spring on hillslope above Site WR2 Aug. 21, 1985 No time recorded 3,075 

S2 ............... Spring water from valley floor spring just below beaver Aug. 23, 1985 10:16 a.m. 775 

dam at Site WR3 

S3 ............... Spring water from valley wall spring between Sites Aug. 24, 1985 10:27 a.m. 5,900 

WRlO and WRll; seep about 3 or 4 feet above valley 

floor 

328 Field Studies of Radon in Rocks, Soils, and Water 
the underlying sediment column. We had previously noted 

in core sampling along this drainage basin that the nearsurface sediment is the least compact and most water 

saturated or, by inference, the most permeable. Zielinski 

and others (1986) also noted apparent closed-system behavior of uranium and its decay products through radium-226 in 

a 10-ft core through the sediment column near the spring 

pool just downvalley from Site WR14 (fig. 135C). This 

closed-system behavior requires that little or no contact of 

the lower layers of sediment with uraniferous ground waters 

occur after initial uranium entrapment and subsequent 

burial. Compaction of the peaty sediment and reduction in 

hydraulic conductivity most likely prevent movement of 

uranium-rich waters into the sediment below the surface 

layers. Clymo (1983) observed that the bulk density of 

Sphagnum peat increases by a factor of 3 to 4 between 10 

and 30 em below the surface and that the hydraulic 

conductivity of peaty sediment decreases by 3 to 5 orders of 

magnitude during compaction and humification. These 

observations suggest that the flow path of the shallow 

ground waters is, in .general, not downward (or upward) 

through the sediment column but rather horizontally 

through the near-surface layer, except near zones of 

upwelling waters marked by seeps and spring pools. In 

these areas, continuous upward flow of water has maintained flow paths through the sediment column. 

These observations lead us to conclude that the 

near-surface sediment should be an important contributor to 

the radon in the shallow ground water except where 

upwelling waters from the bedrock invade the sediment 

column. In order to evaluate the relative contribution of 

radon from the near-surface sediment in the immediate 

vicinity of the hole to radon in water from bedrock sources, 

we calculated the expected radon yield of the upper 45 em 

of sediment from each site by use of the auger hole data (see 

appendix A for methods and assumptions; table 67 and fig. 

137 for the calculated radon yields and comparisons with 

measured radon levels for 1985 and 1986, and fig. 138 for 

the ratio of observed to expected radon for the 1985 

samples). The ratio of observed to expected radon levels is 

below 1.0 from Sites WRl to WRll but goes over 1.0 from 

Sites WR12 to WR14 (in fig. 138, no calculations were 

possible for Sites WR15 and WR16). The zone from Sites 

WR12 to WR14 is also the zone that has the highest 

absolute radon levels. This observation suggests to us that 

excess radon is being contributed to the shallow ground 

waters from Site WR12 downstream to Site WR14. 

Upwelling ground waters recently in contact with bedrock 

are a likely source for the excess radon. Seeps and a spring 

pool are present near Sites WR14 and WR15 but such 

obvious surface evidence of upwelling waters is not present 

near Sites WR12 and WR13. However, we would suggest 

that upwelling bedrock-derived ground waters are likely in 

the subsurface near Sites WR12 and WR13. 

Helium in the Ground-Water Samples 

The helium content of the shallow ground waters in 

our sample sites along the valley floor ranged from 4,960 

ppb at Site WR3 in 1986 to 6,860 ppb at Site WR14 in 1985 

(table 67 and fig. 136). Waters taken from the spring pool 

near Site WR14 (S4) yielded 7,062 ppb in 1985 and 6,584 

ppb in 1986. Waters taken from the slope spring above Site 

WR2 (Sl) in 1985 yielded 5,327 ppb. Shallow ground 

waters along the valley floor yielded helium values close to 

or slightly below atmospheric levels except at Sites WR14 

and WR15 which, in both 1985 and 1986, were considerably above atmospheric levels. Helium levels in 1986 were 

generally lower than those in 1985, except at Sites WR14 

and WR15, where the values were similar overall. The 

lower 1986 values may result from a higher water table and 

thus greater contact of ground waters with biologic activity 

in soils on the hillslopes and in the surface layers of the 

valley-floor alluvium. In detail (fig. 137), the pattern of 

rising and falling values does not correspond from 1985 to 

1986 except at Site WR3 (both years low) and Sites WR14 

and WR15 (both years very high). In a fashion similar to 

that of radon, the observed helium values do not correspond 

in any simple way to calculated GT values for the sample 

sites (fig. 136), nor do observed values correspond with 

calculated helium yields for the near-surface (upper 45 em) 

sediment layers (fig. 137; Helium yields were calculated 

from methods similar to those in appendix A for radon 

except that the emanating power for helium was assumed to 

be 1.00 on the basis of the surface adsorption suggested by 

the studies of Zielinski and others ( 1987) and on the basis of 

the small size and inertness of the helium atom. The 

calculated values shown in figure 137 are the helium 

yielded by the radioactive decay in the shallow sediment 

added to atmospheric helium at 5,240 ppb.). 

Helium levels are significantly depressed at Site 

WR3, the beaver pond. At this site, we noted bubbling of 

gases from the sediment column, especially when it was 

disturbed during digging of the hole. High levels of carbon 

dioxide and methane, the highest observed in the study, 

occur in this water sample. Low helium levels at this site are 

likely due to dilution of the helium by biogenic carbon 

dioxide and methane produced by degradation of the 

organic matter in the sediment that has accumulated on the 

floor of the pond and by depletion of helium from the water 

by bubbling of carbon dioxide and methane through the 

water. 

Highest helium values occur at Sites WR14 and 

WR15 and at the spring pool (fig. 136). This region is 

within the zone of upwelling ground waters inferred from 

the radon data. We are uncertain why the zone of elevated 

helium values seems more restricted than the zone of 

elevated radon values except that other gases are elevated at 

Radon, Helium, and Other Gases in Flodelle Creek, Washington 329 
5,000 

g i:O -c::! "0 00·- 2,500 cumO 

a:::::.a. 

0 

I· 

• I 

·I 

8,700 

• • 

• • • • • • • • I • • 

2,000 

SW-c::! 

"0 CX) ·- 1,000 cumO 

a:::::.a. 

0 I· 

I I 

I 

4,505 7,520 • • • • • • 

• • • • • 

6,666 "0 

Q) • .Nss 

3,333 :l "0 ~ 

~~ (.) 

• • . • • • • • • • • 0 

5,400 

Ean..o .2 CX) a. 5,300 a; m a. 

::r:::::. 

5,200 ~ I I ~ 6,860 5,730 

• • • • • 

5,400 

E <0 ..o ~~8: -1::::. 5,200 

5,000 

20,000 

"0 

Q) 

cuE..o • • 

:; ~ a. 10,000 0 Q) Q. 

(ij.C • • • • • • • 

(.) ~·-·-·-·~·-·-·-'-·-·-·-&-·-·-·-·-·-·-~-·-·-·-·-·~·-·-·-·-

O I I I I I I I I I I I I I I I I 

WR1 WR2 WR3 WR4 WR5 WR6 WR7 WAS WR9 WR10 WR11 WR12 WR13 WR14 WR15 WR16 

Figure 137. Radon and helium data for shallow ground 

waters from the 1985 and 1986 sampling in the study area, 

shown with an expanded scale for comparison with calculated radon and helium yields for the shallow sediment. 

Calculated radon and helium yields are not given for Sites 

Sites WR12 and WR13 but not at Sites WR14 and WR15 

and the spring pool. Dilution or depletion of helium may 

occur at the first two sites. 

Because helium, in contrast to radon, does not decay 

to other products while entrained in the water, the helium 

values observed are affected by gains and losses along the 

entire flow path of the water since first falling in the 

drainage basin as rainfall and becoming isolated from the 

atmosphere. From the present data, we cannot estimate the 

amount of helium entrained in the water from the hillslopes 

before it entered the valley-floor environment or entrained 

along its pathway through the valley floor, nor can we 

330 Field Studies of Radon in Rocks, Soils, and Water 

Site 

WR15 and WR16 because uranium data were not available 

for these sites. Radon and helium values out of the range 

of the graphs are shown with leaders and numbers. Other 

missing data represent unsampled sites or lost s~mples. 

estimate the amount diluted by added biogenic and other 

gases along the way. Thus, we do not necessarily expect 

observed helium levels to be controlled by the uranium 

content of the sediment immediately surrounding the sample site. Specific environmental conditions like those at 

Sites WR3 (stagnant pond), WR14, and WR15 and the 

spring pool site (upwelling waters) may permit the observed 

helium values to correspond to the radon values (unusually 

low values at Site WR3 or unusually high at the latter sites). 

Dilution by added gases seems to be an important phenomenon overall, however, because about 30 percent of our 
3.0 

..... c • ~a: 

-o"O 

Q) Q) 

c:.E 1.5 Q) :::::J • • ~..Q 

0~ • • • • • • • • 0 I I I I - • • 

WA1 WA2 WA3 WA4 WAS WA6 WA7 WAS WA9 WA10 WA11 WA12 WA13 WA14 

Site 

Figure 138. Ratio of observed to calculated radon levels for the shallow ground waters in the 1985 sampling. Sites 15 and 

16 are not shown because uranium data were not available for these sites. 

samples yielded values less than those expected for waters 

in equilibrium with the atmosphere. 

Oxygen, Carbon Dioxide, and Methane in 

Ground Water 

Oxygen, carbon dioxide, and methane were measured 

for 14 of 16 shallow ground-water sample sites and for the 

slope spring (S 1, on the hillslope above Site WR2) and the 

spring pool (S4, near Site WR14). These data are reported 

in table 69 and figure 139 as ratios with respect to nitrogen 

(N2) in the sample. If we assume that the nitrogen in the 

samples varies only slightly, we can measure the relative 

variation in the three other species. 

Oxygen to nitrogen ratios varied within a narrow 

range for the shallow ground waters along the valley floor 

(0.253 to 0.265). The slope spring (Sl) was the most 

oxygenated (0.275) of all the samples collected, whereas 

Site WR14, the spring pool (S4), and Site WR15 were the 

least oxygenated (0.253 to 0.255). Consumption of oxygen 

during oxidation of organic matter and by other reactions 

may deoxygenate waters. Deeply circulating ground waters 

in granitic rocks typically are very oxygen poor. The 

relatively low oxygen levels at Sites WR14 and WR15 and 

the spring pool may indicate a bedrock source. 

Carbon dioxide to nitrogen ratios along the valley 

floor varied from 0.00550 to 0.08468; however, the slope 

spring was the least carbon dioxide rich (0.00260). Carbon 

dioxide values were highest at Site WR3 (the beaver pond) 

and at Site WR12 and lowest at Sites WR11 and WR14, the 

spring pool, and Site WR15. Carbon dioxide levels in this 

system are likely raised by the oxidation of organic matter 

in contact with the shallow ground water. The relatively low 

carbon dioxide values at Sites WR11 and WR14, the spring 

pool, and Site WR15 are atypical of the other shallow 

ground waters and may reflect a different origin for these 

waters. 

Methane to nitrogen ratios along the valley floor 

varied from 0.00000 (not detected) to 0.02344. The highest 

methane was measured at Site WR3 (the beaver pond) at a 

Table 69. Oxygen, carbon dioxide, and methane data 

for selected sample sites and springs in northeast 

Washington, 1985 

[Measured as a ratio to N2] 

Sample 02/N2 C02/N2 CH4/N2 site 

WR1 .................. 0.26535 0.0200 0.0019 

WR2 .................. .25910 .0307 .0017 

WR3 .................. .26253 .0847 .0234 

WR5 .................. .25879 .0128 .0037 

WR7 .................. .25883 .0187 .0051 

WR8 ·················· .25868 .0202 .0051 

WR9 .................. .25669 .0217 .0016 

WR10 ................. .26360 .0122 .0018 

WRll ................. .26296 .0055 .0000 

WR12 ................. .25690 .0593 .0011 

WR13 ................. .25883 .0252 .0033 

WR14 ................. .25290 .0055 .0000 

WR15 ................. .25513 .0085 .0000 

WR16 ................. .25729 .0237 .0019 

S 1 (valley slope spring) .27483 .0026 .0000 

S4 (spring pool) ........ .25522 .0065 .0000 

Reference gas .......... .27324 .0177 .0111 

Reference gas 1 ......... .27287 .0175 .0101 

Reference gas 1 ......... .27351 .0179 .0111 

1 Repeat measurements from the same reference gas cylinder. 

level more than 4 times that of the next highest sample, 

whereas methane was not detected at the slope spring site 

(S1), Sites WR11 and WR14, the spring pool, and Site 

WR 15. The high methane level at the beaver pond site is not 

surprising, because these stagnant waters and the underlying sediment at depth are likely hosts to methanogenic 

bacteria. A low methane level at the slope spring site is also 

not surprising, because these waters are flowing, are oxygenated, and have been in recent contact with the atmosphere and bedrock. Zero methane values for Sites WRll, 

WR14, and WR15 and the spring pool are surprising, 

because they are much lower than at other sites along the 

valley floor, yet the sediment column at these sites contains 

abundant organic matter. These four waters may represent 

ground waters upwelling through bedrock that have only 

limited contact with the organic-rich sediment because the 

Radon, Helium, and Other Gases in Flodelle Creek, Washington 331 
51 54 

30 I I 

29- 10 

0 28- x 0 N 27- ~ • 0 26- • • • • • • • • • • • •o • 25 

10,000 

10 8,000- • 0 

..... • >< 6,000- N 

E: 

N 4,000-

8 2,000- • • • • • • • • • n . eo • 0 

2,500 • 10 2,000- 0 

x 1,500- N 

E: "¢ 1,000- :r: 

(..) 500- • • 

• • • • • • • • an 0 • • I r I I I I I I I I I I I I I I 

WR1 WR2 WR3 WR4 WR5 WR6 WR7 WR8 WR9 WR10 WR11 WR12 WR13 WR14 WR15 WR16 

Site 

Figure 139. Oxygen, carbon dioxide, and methane data for the 1985 samples. Data are reported as ratios with respect to 

nitrogen. Samples WR4 and WR6 were lost from sample cylinders in transit from field to laboratory. 

transit time through the sediment column is rapid. Sites 

WR14 and WR15 and the spring pool are in a zone of 

waters suspected of upwelling through bedrock, and Site 

WRll is immediately downvalley from a slope spring. The 

bedrock source interpretation for Sites WR14 and WR15 

and the spring pool is compatible with our interpretation of 

the oxygen and carbon dioxide data. 

Four end-member assemblages of dissolved gases 

seem to be present in these shallow ground waters: (1) 

beaver pond waters that are methane and carbon dioxide 

rich; (2) slope spring waters that are oxygen rich and 

methane and carbon dioxide poor; (3) "normal" valley-floor 

waters that have modest levels of methane, oxygen, and 

carbon dioxide varying over a limited range; and (4) 

valley-bottom upwelling waters that are oxygen, carbon 

dioxide, and methane poor. The chemistry of the beaver 

pond waters is controlled by the intense biologic activity in 

the surface layers (carbon-dioxide generating) and subsurface layers (methanogenic). The chemistry of the slope 

spring waters may indicate limited interaction with soil and 

shallow interflow along the bedrock-till interface. 

CONCLUSIONS 

Sampling dissolved gases from waters in springs and 

shallow holes dug in a small drainage basin is an effective 

method for characterizing the shallow ground water of the 

basin. The holes must be dug so that standing water from 

above the ground surface is not admitted, and these holes 

must intercept a water-bearing interval. Sites should be 

332 Field Studies of Radon in Rocks, Soils, and Water 

selected carefully late in the dry season. The holes should 

be checked to confirm that they are seeping; if not, a deeper 

hole must be dug. 

The radon and helium concentrations in the shallow 

ground waters of the valley-floor sediment along the upper 

part of the north fork of Flodelle Creek are much lower than 

those expected for uranium ore deposits of this grade. The 

lower values are largely the result of the gross disequilibrium between uranium and its decay products in the very 

young surficial uranium deposit hosted by these sediments. 

Because of this disequilibrium, measurement of radon or 

helium in shallow ground waters is not likely to be effective 

in the search for surficial uranium deposits. 

Ground waters apparently derived from the bedrock 

have higher levels of radon associated with them than 

ground waters whose most recent contact has been with the 

valley-floor sediment alone. If so, measurement of radon in 

ground water, and, to a lesser degree, measurement of 

helium in ground water, may be an effective technique for 

examining the flux of ground water from the underlying 

bedrock into the sediment column of the valley floor. This 

technique is analogous to measuring the flux of radon in 

streams as a measure of the ground-water input to the 

surface flow (Lee and Hollyday, 1987). Sampling of ground 

waters for radon could have broader application to the study 

of the ground-water budget of wetlands in other areas where 

this contrast in radon levels exists. 

The ground waters in the drainage basin show radon, 

helium, oxygen, carbon dioxide, and methane concentrations characteristic of the environment in which the waters 
occur or have recently traveled through. Stagnant waters 

from the sediment of a beaver pond in the upper part of the 

·study area are high in carbon dioxide and methane, because 

the organic matter in the sediment column has been oxidized and biogenically degraded. These waters have low 

levels of helium and radon because these gases have been 

diluted by addition of the biogenic gases and depleted by 

bubbling of carbon dioxide and methane through the sediment column. Ground waters from springs on the hillslopes 

are high in oxygen but relatively low in carbon dioxide and 

methane because the waters have had limited contact with 

the thin soil horizons, and these horizons are low in organic 

matter. Such waters are high in radon probably because they 

have had recent contact with uranium-rich weathered bedrock and sandy glacial till; the waters are slightly below 

atmospheric levels in helium. "Normal" ground waters in 

the sediment filling the valley floor contain modest amounts 

of radon, helium, oxygen, carbon dioxide, and methane 

because these waters have had recent contact with biologically active, uraniferous sediment in the upper part of the 

sediment column of the valley floor. Ground waters in a 

zone of upwelling along the valley floor are very low in 

oxygen, carbon dioxide, and methane but are very high in 

radon and (or) helium. A bedrock source is thus suggested 

for the upwelling water, possibly a fracture zone intercepting the valley floor, as inferred by Zielinski and Schumann 

(1987). 

APPENDIX A. CALCULATION OF EXPECTED 

RADON YIELD 

For calculation of the expected radon in the shallow 

ground water at the sample site, we assume that the 

sediment contributing to the water in the sample hole lies 

within the upper 45 em of the surface (average depth of our 

sample holes) and that the nearby auger hole is representative of that interval. The radon content of water in a 

representative 1-L (1 ,000 cm3

) volume of water-saturated 

sediment is given by 

Rn (in pCi/L)= 1,000 cm3

/L X d x c X au X e x p 

f 

where d is the dry density of the sediment (in grams per 

cubic centimeter, estimated by comparison with measurements of organic-rich sediment here and elsewhere (Otton, 

unpub. data, 1985); cis the uranium content (in micrograms 

per gram) as determined in the nearby auger hole; au is the 

specific activity of uranium at secular equilibrium (0.33 

pCi/~g); e is the fractional equilibrium factor estimated by 

comparison with a study site near Site WR14 (Zielinski and 

others, 1987) where the fractional equilibrium ranged from 

0.01 to 0.04 for the near surface layers; pis the emanating 

power (the ratio of radon escaping to the pores to radon 

produced by the decay of radium in the sample) taken as 

0.33 (emanating power for "lignitic" soils reported by 

Barretto and others, 1975); and f is the fraction of water 

making up the 1-L volume of water-saturated sediment. 

Note that weighted averages for dry density, uranium 

content, and fractional equilibrium were estimated or 

calculated for the 45-cm interval from the descriptions of 

and analytical data for the sediment at each site. Although 

extensive measurements of emanating power of mineral 

matter in air have been made, the emanating power of 

water-saturated sediment is not well known. 

REFERENCES CITED 

Asikainen, M., and Kahlos, H., 1979, Anomalously high 

concentrations of uranium, radium and radon in water from 

drilled wells in the Helsinki region: Geochimica et Cosmochimica Acta, v. 43, p. 1681-1686. 

Barretto, P.M.C., Clark, R.B., and Adams, J.A.S., 1975, 

Physical characteristics of radon-222 emanation from rocks, 

soils, and minerals: Its relation to temperature and alpha 

dose, in Adams, J.A.S., Lowder, W.M., and Gesell, T.M., 

eds., The natural radiation environment II, v. 2, Symposium 

proceedings, Houston, Tex., August 7-11, 1972: ERDA 

Report CONF-720805-P2, p. 731-740, Rice University and 

the University of Texas, Houston, available from National 

Technical Information Service. 

Brutsaert, W.F., Norton, S.A., Hess, C.T., and Williams, J.S., 

1981 , Geologic and hydrologic factors controlling radon-222 

in ground water in Maine: Ground Water, v. 19, no. 4, p. 

407--417. 

Clymo., R.S., 1983, Peat, Chap. 4, in Gore, A.J.P., ed., Ecosystems of the world 4A, Mires: Swamp, bog, fen and moor: 

Amsterdam, Elsevier, p. 159-224. 

Dyck, ·w., and Jonasson, I.R., 1977, The nature and behavior of 

gases in natural waters: Water Research, v. 11, p. 705-711. 

Freeze, R.A., 1972, Role of subsurface flow in generating surface 

runoff, 2. Upstream source areas: Water Resources Research, 

v. 8, no. 5, p. 1272-1283. 

Freeze, R.A., and Cherry, J.A., 1979, Groundwater: Englewood 

Cliffs, N.J., Prentice-Hall, Inc., 604 p. 

Johnson, S.Y., Otton, J.K., and Macke, D.L., 1987, Geology of 

the Holocene surficial uranium deposit of the north fork of 

Flodelle Creek, northeastern Washington: Geological Society 

of America Bulletin, v. 98, p. 77-85. 

Lee, R.W., and Hollyday, E.F., 1987, Radon measurement in 

streams to determine location and magnitude of ground water 

seepage, in Graves, B., ed., Radon, radium, and other 

radioactivity in ground water, Proceedings of the NWW A 

Conference, April 7-9, 1987: Somerset, N.J., Lewis 

Publishers, p. 241-249. 

McHugh, J.B., and Miller, W.R., 1982, Radon survey of ground 

waters from Beaver and Milford Basins, Utah: U.S. Geological Survey Open-File Report 82-382, 13 p. 

Otton, J.K., and Zielinski, R.A., 1985, Movement and concentration of uranium in young organic-rich sediments, Stevens 

County, Washington, in Poty, B. , ed. , Proceedings of the 

International Conference on Concentration Mechanisms of 

Uranium in Geological Environments, Nancy, France, Octobe:r 1985: French Society for Mineralogy and Crystallography 

Radon, Helium, and Other Gases in Flodelle Creek, Washington 333 
and the Center for Research on the Geology of Uranium, p. 

49-52. 

Reimer, G.M., 1977, Fixed-volume gas inlet system for an 

alpha-sensitive cell adapted for radon measurement: U.S. 

Geological Survey Open-File Report 77-409, 3 p. 

Rogers, A.S.,1958, Physical behavior and geologic control of 

radon in mountain streams: U.S. Geological Survey Bulletin 

1052-E, p. 187-211. 

Zielinski, R.A., Bush, C.A., and Rosholt, J.N., 1986, Uranium 

series disequilibrium in a young surficial uranium deposit, 

334 Field Studies of Radon in Rocks, Soils, and Water 

northeastern Washington, U.S.A.: Applied Geochemistry, v. 

1,p.503-511. 

Zielinski, R.A., Otton, J.K., Wanty, R.B., and Pierson, C.T., 

1987, The geochemistry of water near a surficial organic-rich 

uranium deposit, northeastern Washington state, U.S.A.: 

Chemical Geology, v. 62, p. 263-289. 

Zielinski, R.A., and Schumann, R.R., 1987, Response of Douglas Fir (Pseudotsuga menziesii) to uraniferous groundwater 

in a small glaciated drainage, northeastern Washington state: 

Journal of Geochemical Exploration, v. 27, p. 281-298. 
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