Radionuclide Behavior in 

Soils and Soil-to-Plant 

Concentration Ratios for 

Assessing Food Chain 

Pathways

Office of Nuclear Regulatory Research

NUREG/CR-7120

PNNL-20979
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Radionuclide Behavior in 

Soils and Soil-to-Plant 

Concentration Ratios for 

Assessing Food Chain 

Pathways

Manuscript Completed: November 2011

Date Published: March 2012

Prepared by

B. A. Napier

R. J. Fellows

K. M. Krupka

Pacific Northwest National Laboratory

P.O. Box 999

Richland, WA 99352

P. R. Reed, NRC Project Manager

NRC Job Code N6455

Office of Nuclear Regulatory Research

NUREG/CR-7120

PNNL-20979

iii 

Abstract 

This report describes work performed under the U.S. Nuclear Regulatory Commission’s 

(NRC’s) project Radionuclide Uptake in Plants and Animals for Food-Chain Pathway 

Analyses in Biosphere Models. The project was established by the NRC to assess and 

evaluate a number of key parameters used in the food-chain models employed in 

performance assessments of radioactive waste disposal facilities. Section 1 of this report 

gives the objectives and a brief overview of the report’s organization. Section 2 

summarizes characteristics of samples of soils and groundwater from three geographical 

regions of the United States, the Southeast, Northwest, and Southwest, and analyses 

performed to characterize their physical and chemical properties. Section 3 discusses 

physicochemical speciation and geochemistry of radionuclides in these natural soil-water 

systems. Because the uptake and behavior of radionuclides in plant roots, plant leaves, 

and animal products depends on the chemistry of the water and soil coming in contact 

with plants and animals, water and soil samples collected from these regions of the 

United States were used in experiments at Pacific Northwest National Laboratory to 

determine radionuclide soil-to-plant concentration ratios. Section 4 describes how crops 

and forage used in the experiments were grown in the soils, and long-lived radionuclides 

introduced into the groundwater provide the contaminated water used to water the grown 

plants. The radionuclides evaluated include neptunium-237 and iodine-125. Plant 

varieties include alfalfa, corn, and potato. The radionuclide uptake results from this 

research study show how regional variations in water quality and soil chemistry affect 

radionuclide uptake. Section 4 summarizes the procedures and results of the uptake 

experiments, and relates the soil-to-plant uptake factors derived. In Section 5, the results 

found in this study are compared with similar values found in the biosphere modeling 

literature; the study’s results are generally in line with current literature, but soil- and 

plant-specific differences are noticeable. This food-chain pathway data may be used by 

the NRC staff to assess dose to persons in the reference biosphere (e.g., persons who live 

and work in an area potentially affected by radionuclide releases) of waste disposal 

facilities and decommissioning sites. 

v

Contents

Abstract.............................................................................................................................iii

List of Tables................................................................................................................... vii

List of Figures.................................................................................................................. vii

Acknowledgments............................................................................................................ xi

Acronyms........................................................................................................................ xiii

Units of Measure ............................................................................................................. xv

1.0 Introduction......................................................................................................... 1-1

1.1 References ........................................................................................................ 1-2

2.0 Sampling and Analysis of Groundwater and Soil Samples................................ 2-1

2.1 Sampling Sites for Groundwater and Soil Samples ......................................... 2-1

2.1.1 Hanford Site, Washington ..................................................................... 2-1

2.1.2 Nye County, Nevada.............................................................................. 2-2

2.1.3 Clemson University Site, South Carolina.............................................. 2-2

2.2 Methods for Analysis and Characterization of Groundwater and Soil 

Samples............................................................................................................. 2-3

2.2.1 Analysis of Groundwater Samples ........................................................ 2-4

2.2.1.1 pH and Conductivity ..................................................................... 2-4

2.2.1.2 Alkalinity....................................................................................... 2-4

2.2.1.3 Anions ........................................................................................... 2-4

2.2.1.4 Total Carbon.................................................................................. 2-4

2.2.1.5 Cations and Trace Metals.............................................................. 2-5

2.2.2 Characterization and Analysis of Bulk Soil Samples............................ 2-5

2.2.2.1 X-ray Diffraction........................................................................... 2-5

2.2.2.2 Elemental Analysis by X-ray Fluorescence .................................. 2-5

2.2.2.3 Particle Size Distribution............................................................... 2-6

2.2.2.4 Moisture Content........................................................................... 2-6

2.2.2.5 Cation Exchange Capacity ............................................................ 2-6

2.2.2.6 Carbon Content.............................................................................. 2-7

2.2.2.7 1:1 Soil:Water Extracts ................................................................. 2-7

2.3 Results of Analyses and Characterization of Groundwater and Soil Samples. 2-7

2.4 References ...................................................................................................... 2-23

3.0 Speciation and Geochemistry of Radionuclides in Soil-Water Systems............ 3-1

3.1 Background....................................................................................................... 3-1
vi

3.2 Eh-pH Species Predominance Diagrams.......................................................... 3-5

3.2.1 Technetium ............................................................................................ 3-6

3.2.2 Iodine ..................................................................................................... 3-7

3.2.3 Uranium ................................................................................................. 3-7

3.2.4 Plutonium............................................................................................... 3-8

3.2.5 Neptunium ............................................................................................. 3-8

3.2.6 Americium ............................................................................................. 3-9

3.3 References ...................................................................................................... 3-17

4.0 Soil-to-Plant Uptake............................................................................................... 4-1

4.1 Materials and Methods ..................................................................................... 4-2

4.1.1 Soils ....................................................................................................... 4-2

4.1.2 Contaminants......................................................................................... 4-3

4.1.3 Plant Material......................................................................................... 4-3

4.1.3.1 Growth Conditions....................................................................... 4-3

4.1.3.2 Plant Harvest and Isotope Analysis ............................................. 4-5

4.1.4 Soils Isotope Analysis............................................................................ 4-5

4.2 Experimental Results for 237Np ........................................................................ 4-6

4.2.1 Dry Matter Production........................................................................... 4-7

4.2.2 Neptunium-237 Uptake, Distribution, and Concentration..................... 4-9

4.2.3 Neptunium-237 Concentration Ratios................................................. 4-12

4.3 Experimental Results for Iodine-125.............................................................. 4-14

4.3.1 Dry Matter Production......................................................................... 4-15

4.3.2 Iodine-125 Uptake, Distribution, and Concentration .......................... 4-17

4.3.3 Iodine-125 Concentration Ratios......................................................... 4-19

4.4 References ...................................................................................................... 4-21

5.0 Discussion................................................................................................................ 5-1

5.1 Soils and Groundwater Analyses...................................................................... 5-1

5.2 Speciation and Geochemistry........................................................................... 5-2

5.3 Soil-to-Plant Concentration Ratios for the Soils and Crops Studied................ 5-2

5.4 Uncertainties in the Results.............................................................................. 5-3

5.5 Comparison of CR Results to Current Literature ............................................. 5-3

5.6 References ........................................................................................................ 5-6
vii

Figures

2.1 Background-Subtracted XRD Pattern for Hanford Site Soil Sample ................. 2-12

2.2 Background-Subtracted XRD Pattern for Nye County Soil Sample .................. 2-13

2.3 Background-Subtracted XRD Pattern for Clemson University Site Soil 

Sample................................................................................................................. 2-14

3.1 Eh-pH Diagram Showing Dominant Aqueous Species of Technetium.............. 3-11

3.2 Eh-pH Diagram Showing Dominant Aqueous Species of Iodine....................... 3-12

3.3 Eh-pH Diagram Showing Dominant Aqueous Species of Uranium................... 3-13

3.4 Eh-pH Diagram Showing Dominant Aqueous Species of Neptunium............... 3-14

3.5 Eh-pH Diagram Showing Dominant Aqueous Species of Plutonium ................ 3-15

3.6 Eh-pH Diagram Showing Dominant Aqueous Species of Americium............... 3-16

4.1 Component Arrangement for Soil Pots Employed in Soil-Plant 

Experiments........................................................................................................... 4-4

4.2 Plant and Pot Arrangement in Growth Chamber in Soil-Plant Experiments........ 4-4

4.3 Harvest of 237Np Alfalfa Plants Grown in South Carolina Soil ............................ 4-7

4.4 Corn Seed Harvested from Plants Grown in South Carolina Soil a for 

237Np Experiment .................................................................................................. 4-8

Tables

2.1 Tables and Figures Containing the Results of the Analyses and 

Characterization Studies of the Groundwater, Soil, and 1:1 

Soil:Water Extract Samples from the Hanford Site, Nye County, 

and Savannah River/Clemson University Locations ............................................ 2-8

2.2 pH and Conductivity Values for the Groundwater Samples............................... 2-10

2.3 Alkalinity Values for the Groundwater Samples................................................ 2-10

2.4 Concentrations of Dissolved Anions in the Groundwater Samples.................... 2-10

2.5 Concentrations of Total Dissolved Carbon in the Groundwater Samples .......... 2-10

2.6 Concentrations of Dissolved Macro and Trace Metals in the Groundwater 

Samples as Determined by ICP-OES.................................................................. 2-11

2.7 Concentrations of Dissolved Trace Metals in the Groundwater Samples as 

Determined by ICP-MS ...................................................................................... 2-11

2.8 Concentrations of Dissolved Trace Metals in the Groundwater Samples as 

Determined by ICP-MS (Continued).................................................................. 2-12

2.9 Concentrations of Major Elements in Bulk Soil Samples as Determined by 

XRF..................................................................................................................... 2-15
viii

2.10 Concentrations of Trace Elements in Bulk Soil Samples as Determined by 

XRF..................................................................................................................... 2-15

2.11 Particle Size Analysis of the Bulk Soil Samples................................................. 2-16

2.12 Moisture Contents of the Bulk Soil Samples...................................................... 2-16

2.13 Cation Exchange Capacity Values for the Soil Samples .................................... 2-16

2.14 Carbon Contents of the Soil Samples.................................................................. 2-17

2.15 pH and Conductivity Values for the 1:1 Soil:Water Extracts............................. 2-17

2.16 Alkalinity Values for the 1:1 Soil:Water Extracts.............................................. 2-17

2.17 Concentrations of Dissolved Anions in 1:1 Soil:Water Extract.......................... 2-18

2.18 Concentrations (μg/g soil) of Dissolved Macro and Trace Metals in the 

1:1 Water Extracts as Determined by ICP-OES ................................................. 2-19

2.19 Concentrations (μg/L pore water) of Dissolved Macro and Trace Metals 

in the 1:1 Water Extracts as Determined by ICP-OES ....................................... 2-20

2.20 Concentrations of Dissolved Macro and Trace Metals in 1:1 Water 

Extracts as Determined by ICP-MS .................................................................... 2-21

2.21 Concentrations of Dissolved Trace Elements in 1:1 Water Extracts as 

Determined by ICP-MS (Continued).................................................................. 2-22

3.1 Summary of Chemical Processes Affecting the Mobility of Radionuclides......... 3-2

4.1 Summarized Soil Properties.................................................................................. 4-2

4.2 Attributes of the Np-237 Employed in the Soil-Plant Uptake Experiments......... 4-6

4.3 Specific Activity and Calculated Weights of 237Np in the Three Differing 

Soil Type Pots Used in the Soil-Plant Uptake Experiments................................. 4-7

4.4 Total Plant Dry Weight Per Pot for 237Np Experiment ......................................... 4-8

4.5 Dry Weight of Corn Leaves, Stems, Cob, and Seed for 237Np Experiment .......... 4-8

4.6 Dry Weight of Potato Leaves and Potatoes for 237Np Experiment ....................... 4-9

4.7 Neptunium-237 Specific Activity of Alfalfa Shoots Grown from Seed in 

Differing Soil Types for a Minimum of 60 Days.................................................. 4-9

4.8 Neptunium-237 Specific Activity of Corn Leaves, Stem, Cobs, and 

Kernels from Plants Grown from Seed in Differing Soil Types for 

a Minimum of 60 Days ....................................................................................... 4-10

4.9 Neptunium-237 Specific Activity of Potato Shoots, Tubers, and Tuber 

Skins Grown from Cuttings in Differing Soil Types for a Minimum of 

60 Days ............................................................................................................... 4-10

4.10 Percent Distribution of Recovered Above Ground 237Np in Alfalfa Shoots 

for Different Soils and Total pCi Recovered in Plants ....................................... 4-11

4.11 Percent Distribution of Recovered Above Ground 237Np in Corn Shoots 

for Different Soils ............................................................................................... 4-11

4.12 Percent Distribution of Recovered 237Np in Potatoes for Different Soils........... 4-11
ix

4.13 Neptunium-237 Concentration Ratios for Alfalfa Shoots Grown from 

Seed in Differing Soil Types for a Minimum of 60 Days................................... 4-12

4.14 Neptunium-237 Concentration Ratios for Corn Shoots Grown from 

Seed in Differing Soil Types for a Minimum of 60 Days................................... 4-13

4.15 Neptunium-237 Concentration Ratios for Potato Shoots Grown from 

Seed in Differing Soil Types for a Minimum of 60 Days................................... 4-14

4.16 Attributes of the 125I Employed in the Soil-Plant Uptake Experiments.............. 4-14

4.17 Specific Activity and Calculated Weights of 125I in the Three Differing 

Soil Type Pots Used in the Soil-Plant Uptake Experiments............................... 4-15

4.18 Total Plant Dry Weight Per Pot for 125I Experiment........................................... 4-15

4.19 Dry Weight of Corn Leaves, Stems, and Ear for 125I Experiment ...................... 4-15

4.20 Dry Weight of Potato Leaves and Potatoes for 125I Experiment......................... 4-16

4.21 Iodine-125 Specific Activity of Alfalfa Shoots Grown from Seed in 

Differing Soil Types for a Minimum of 60 Days................................................ 4-17

4.22 Iodine-125 Specific Activity of Corn Leaves, Stems, and Ears from 

Plants Grown from Seed in Differing Soil Types for a Minimum 

of 60 Days........................................................................................................... 4-18

4.23 Iodine-125 Specific Activity of Potato Shoots, Tubers, and Tuber Skins 

Grown from Cuttings in Differing Soil Types for a Minimum of 

60 Days ............................................................................................................... 4-18

4.24 Percent Distribution of Recovered Above-Ground 125I in Alfalfa Shoots 

for Different Soils ............................................................................................... 4-18

4.25 Percent Distribution of Recovered Above-Ground 125I in Corn Shoots for 

Different Soils..................................................................................................... 4-18

4.26 Percent Distribution of Recovered 125I in Potatoes for Different Soils............... 4-19

4.27 Iodine-125 Concentration Ratios for Alfalfa, Corn, and Potato Plants 

Grown from Seed in Nevada, Hanford, and South Carolina Soil 

Types for a Minimum of 60 Days....................................................................... 4-20

5.1 Soil-to-Plant Concentration Ratios Commonly Used in Environmental 

Assessments.......................................................................................................... 5-5

xi

Acknowledgments

The authors are particularly grateful for the technical guidance, review, and 

encouragement provided by Phillip R. Reed of the U.S. Nuclear Regulatory Commission. 

The authors thank KR Krupka, SR Baum, KM Geiszler, IV Kutnyakov, VL LeGore, MJ 

Lindberg, HT Schaef, and TS Vickerman (all of PNNL) for assisting with various aspects 

of the analyses and characterization of the groundwater and soil samples. We also extend 

our appreciation to RJ Serne, WJ Deutsch, and their PNNL co-workers for providing 

written descriptions of the methods used for analysis and characterization of the 

groundwater and soil samples. We particularly thank J Rossabi (Savannah River 

Technology Center) and J Mueller (Edisto Research and Education Center) for their 

assistance in sample collection. We also wish to thank those who assisted at PNNL with 

the sample plant growth and evaluation: Rick Herrington, Danielle Saunders, and Brad 

Barfus. Finally, we thank Kirk Cantrell for stepping in and helping complete Section 3 

upon the untimely loss of our friend and co-author Ken Krupka.

xiii

Acronyms

APHIS Animal Plant Health Inspection Service

ASA American Society of Agronomy

ASTM American Society for Testing and Materials

CBP Columbia Basin Project

CEC cation exchange capacity

cps counts per second

CR Concentration Ratio

CY calendar year

DOE U.S. Department of Energy

EPA U.S. Environmental Protection Agency

ICP-MS inductively coupled plasma-mass spectroscopy (spectrometer)

ICP-OES inductively coupled plasma-optical emission spectroscopy 

ICDD International Center for Diffraction Data, Newtown Square, Pennsylvania

JCPDS Joint Committee on Powder Diffraction Standards

LLW low-level waste

LOI loss on ignition

N Normality

ND not detected

NRC Nuclear Regulatory Commission

N-P-K Nitrogen – Phosphorous – Potassium

PDFTM powder diffraction file

PNNL Pacific Northwest National Laboratory

QA quality assurance

RCP Radioactive Control Policy

SBMS Standards in Business Management

SRF Savannah River Field soil

SRS Savannah River Site

USDA United States Department of Agriculture 

USEPA United States Environmental Protection Agency

USGS U.S. Geological Survey

XRD X-ray powder diffractometry analysis (commonly called X-ray diffraction)

XRF X-ray fluorescence analysis

xv

Units of Measure

Å angstrom

g gram

kV kilovolt

L liter

M molarity, mol/L

mA milliampere

mg milligram

mL milliliter

MPa megapascal

mS millisiemens

N Normality (of a solution), in number of gram equivalent weights of solute 

per liter of solution

I/Io relative intensity of an XRD peak to the most intense peak

wt% weight percent

oC temperature in degrees Celsius [T(oC) = T(K) – 273.15)]

λ wavelength

μ micro (prefix, 10-6)

μEinstein microEinstein (a measure of irradiance – about 6.02x1017 photons)

μeq microequivalent

μg microgram

μm micrometer

θ angle of incidence (Bragg angle)

1-1

1.0 Introduction

The U.S. Nuclear Regulatory Commission’s (NRC’s) project Radionuclide Uptake in 

Plants and Animals for Food-Chain Pathway Analyses in Biosphere Models was

established to assess and evaluate a number of key parameters used in the food-chain 

models employed in performance assessments of radioactive waste disposal facilities. 

The objectives of the research program include: 

• Provide data and information for the important features, events, and processes of 

the pathway models for use in biosphere computer codes. These codes calculate 

the total effective dose equivalent (TEDE) to the average member of the critical 

group and maximally exposed individual—for example, from radionuclides in the 

contaminated groundwater release scenarios in the NRC’s performance 

assessments of waste disposal facilities and decommissioning sites;

• Reduce uncertainties in food-chain pathway analysis from the agriculture scenarios 

of biosphere models in performance assessment calculations;

• Provide better data and information for food-chain pathway analyses by:

o Performing laboratory and field experiments, including integral and 

separate-effect experiments, to evaluate the potential pathways and uptake 

mechanisms of plants and animals contaminated by long-lived 

radionuclides;

o Presenting food-chain pathway data and information by regional and local 

geographical locations;

o Quantifying uncertainties in the radioactive contamination of food crops 

and long-term build-up of radionuclides in soils with contaminated ground 

water from water irrigation systems;

o Determining data on factors affecting radionuclide uptake of food crops 

including irrigation water processes, soil physical and chemical properties, 

soil leaching and retention properties near crop roots, soil resuspension 

factors, and other soil and plant characteristics.

The results of this research program provide needed food-chain pathway data and 

information for important radionuclides that may be used by the NRC staff to assess dose 

to persons who live and work in areas potentially affected by radionuclide releases from

waste disposal facilities and decommissioning sites. 

Section 2 of this report describes activities undertaken to collect samples of soils and 

groundwater from three regions of the United States, the Southeast, Northwest, and 

Southwest, and perform analyses to characterize their physical and chemical properties. 

This section of the report is largely the same as that presented in earlier project reports

(Napier et al. 2005; Napier et al. 2007) so that the soil and plant data could be 

conveniently located in a single report. 

In Section 3 of this report, computer modeling methods are used to calculate, from 

equilibrium thermodynamic principles, the distributions of dominant aqueous species and 

potential solubility controls for the environmentally important oxidation states of several
1-2 

selected radionuclides. The materials evaluated are technetium, iodine, uranium, 

plutonium, neptunium, and americium. The results of these speciation and solubility 

calculations for each radionuclide are graphically presented as a series of Eh-pH (or 

Pourbaix) diagrams in the water collected from the three different geographical regions 

and used in the soil-to-plant concentration determination studies. 

 

Because the uptake and behavior of radionuclides in plant roots, plant leaves, and animal 

products depends on the chemistry of the water and soil coming in contact with plants 

and animals, water and soil samples collected from these regions of the United States 

were used in experiments at Pacific Northwest National Laboratory to determine 

radionuclide soil-to-plant concentration ratios. Crops and forage used in the experiments 

were grown in the soils, and long-lived radionuclides introduced into the groundwater 

provide the contaminated water used to water the grown plants. Radionuclides evaluated 

include 125I and 237Np. Plant types include alfalfa, corn, and potato. The radionuclide 

uptake results from this research study show how regional variations in water quality and 

soil chemistry affect radionuclide uptake. Section 3 summarizes the methods used in 

preparing the soils, growing the plants, and analyzing the information gathered regarding 

soil-to-plant transfer factors for the crops grown in each of these three soil types. In 

Section 4, the results found in this study are compared with comparable values found in 

the biosphere modeling literature. 

Additional efforts were expended to try to gather information about foliar interception of 

wet deposition and subsequent translocation from leaves to other plant parts. These 

experiments were generally unsuccessful. A brief description of the experimental setup 

and problems encountered is given in Appendix A. 

Data from this research program are expected to be used in biosphere models to calculate 

the dose from groundwater release scenarios in performance assessment computer codes. 

1.1 References 

Napier BA, KM Krupka, MM Valenta, and TJ Gilmore. 2005. Soil and Groundwater 

Sample Characterization and Agricultural Practices for Assessing Food Chain Pathways 

in Biosphere Models. NUREG/CR-6881, U.S. Nuclear Regulatory Commission, 

Washington, D.C. 

Napier BA, RJ Fellows, and KM Krupka. 2007. Soil-to-Plant Concentration Ratios for 

Assessing Food Chain Pathways in Biosphere Models. NUREG/CR-6941, U.S. Nuclear 

Regulatory Commission, Washington, D.C. 
2-1

2.0 Sampling and Analysis of Groundwater 

and Soil Samples

Uncontaminated soil and groundwater samples were collected from three sites that are in 

the vicinity of waste disposal facilities and unaffected by disposal activities at those sites. 

The soil and groundwater samples were collected for use in plant radionuclide uptake 

studies. The areas for sampling included agricultural sites and currently operating and 

proposed waste disposal facilities and decommissioning sites, including the commercial 

low-level radioactive waste (LLW) sites in the states of Washington and South Carolina. 

The information in this section is a subset of that originally reported in Napier et al. 

(2005; 2007) so that the groundwater, soils, and transfer factor information could be 

easily found within a single reference.

2.1 Sampling Sites for Groundwater and Soil Samples

Three areas for soil and water samples were identified that met the objectives. These 

sites include the Hanford Site, Washington; Savannah River, South Carolina; and Nye 

County, Nevada. Together they provide a range of soil characteristics for radionuclide 

plant uptake studies. The Hanford location is about 15 km (9 miles) west of the 

U.S. Ecology low-level waste disposal site; the South Carolina soil sample was obtained 

from a research field operated by Clemson University in Blackville, South Carolina, in 

Barnwell County, located 15 mi. east-northeast of the Savannah River Plant, and the 

Nevada location is about 80 km (50 miles) southeast of the Beatty low-level waste site.

The experimental design of the uptake experiments requires approximately 300 liters of 

water and 0.2 cubic meters of soil from each site. The latitude and longitude position of 

each sampling location was recorded by using a global positioning system (GPS) unit to 

provide traceability and the opportunity to provide duplicate samples if required. No 

measurements were made at the well of parameters such as Eh, temperature, dissolved 

oxygen, etc., because in the anticipated use of spray irrigation, these parameters would 

rapidly change to match the terrestrial conditions.

2.1.1 Hanford Site, Washington

The sampling site for the Hanford soil and groundwater samples is located off 

Washington highway 240 near the area referred to as the “Yakima Barricade” at the 

western entrance to the U.S. Department of Energy Hanford Site in southeastern 

Washington State. Logistically, the sample site is easily accessible by road, and a pump 

is installed in the well used for groundwater sampling. The Hanford Site designation for 

the well is 699-49-100C, and the coordinates are North 46.577°, West 119.726°. The 

well is used to provide “up-gradient background” groundwater samples (i.e., water not 

affected by Hanford disposal activities) to the Hanford Site environmental programs.
2-2

The water chemistry of the well has been extensively characterized, and the analytical 

results are available through the Hanford Environmental Information System (HEIS

1994) database. 

The Hanford soil1 sample was collected within 100 m of the well used for the 

groundwater sample, and the coordinates for the location of the soil sample are North 

46.576°, West 119.726°. The soil sample is a silty, very fine sand that is referred to as 

the McGee Ranch soil. The soil in this area has been extensively characterized, because 

there are plans to use this sediment as a soil covering for surface barriers on wastedisposal areas at the Hanford Site (DOE 1999).

2.1.2 Nye County, Nevada

The sampling site in Nye County is located in a desert valley approximately 175 km 

(110 miles) miles west of Las Vegas in the Amargosa Valley in Nye County, Nevada. 

The soil and groundwater samples were collected by agreement with the owner from 

private land. The site is located west of Las Vegas approximately 175 km (110 miles) on 

Nevada highway 95.

The groundwater was collected from an irrigation well that is used to flood irrigate

pastureland. The coordinates for the well used for the groundwater sample are 

North 36 29’ 24.4”, West 116 30’ 51.5”. The pasture was used to grow alfalfa for about 

14 years up until about 1996, when it was allowed to turn to pasture. According to the 

land owner, the soil was originally conditioned using approximately 0.225 kg/m2

(10 tons/acre) of gypsum. No commercial fertilizer was used on the pasture.

The soil was approximately 75 cm (2.5 feet) thick at the sample site, and consists of a 

light brown silty sand. The coordinates for the site of the soil sample are 

North 36° 29’ 23.7”, West 116° 30’ 52.0”. Near the base, the occurrence of white streaks 

in the soil increased until the soil transitioned into broken-up calcrete. 

2.1.3 Clemson University Site, South Carolina

This site was selected because this soil provides a good representation of an 

agricultural soil from the southeastern United States. This site receives considerably 

more infiltration from rainfall and snowmelt than the soil samples from Hanford and Nye 

County. The soil sample was provided by a professor of plant pathology and physiology 

at the Edisto Research and Education Center (664 Research Road, Blackville, 

South Carolina) at Clemson University. Blackville is 16 km (10 mi.) northeast of 

Barnwell on the junction of US 78 and US 321, and is approximately 50 km (30 mi.) east 

of Augusta, 25 km (15 mi.) east-northeast of the Savannah River Plant, and 70 km 

(45 mi.) south-southwest of Columbia, South Carolina. Based on GPS, the soil sample 

was taken at coordinates North 33.2124°, West 81.18446°. Published soils maps indicate 

the soil is described as a Dothan Loamy Sand with a slope of 0 to 2% or less. The soil 

 1 Because of its depositional history, the unconsolidated surface and near-surface geologic material at the 

Hanford Site is referred to as “sediment” in Hanford Site literature.
2-3

sample is from a research field at The Edisto Research and Education Center. The field 

has been in agricultural production, primarily cotton and soybean, continuously for the 

last 25 years. The field was planted in soybeans in CY 2004, in cotton for one or two 

years before that, and then primarily in soybeans for the previous 10 or 12 years. Except 

for cleaning off plant debris, the location of the soil sample was undisturbed before 

digging of the soil sample. The soil was collected by scraping off the top 2 to 8 cm (1 to 

3 inches) and collecting the sample at the 5 to 20 cm (2 to 8 inch) depth. The soil from 

this site falls under the Restricted Shipping Regulations of the United States Department 

of Agriculture Animal Plant Health Inspection Service (USDA-APHIS). The reason 

given for this restriction is the potential for fire-ant contamination. Following a lengthy 

approval period by APHIS, the Savannah River soils were processed as follows:

• The soil was considered contaminated until heat-treated and therefore handled 

using sterile technique. This meant that it was opened and handled only in an 

appropriate biosafety cabinet. These are within locked, negative air-pressure 

laboratories, with controlled access to authorized personnel only. At the 

minimum, safety apparel included a lab coat and two (2) pairs of disposable gloves 

that could be subsequently autoclaved. 

• The five-gallon containers were placed in a freezer (-5°C) for 14 days and then 

transferred to an oven maintained at 80°C for an additional four days. Following 

this the soils were allowed to return to room temperature and then prepared as the 

Hanford and Nevada soils above. 

• All soil residues (wastes and empty containers) were treated by either heating in a 

forced air oven at 110°-125°C for 16 h or autoclaving at temperatures ≥ 110°C and 

15 pounds pressure for a minimum of 30 min. 

Prior to use in the experiment all soils were tested for soil-water holding capacity and 

percent moisture remaining in air-dried/sieved soil. The water samples are from 

Savannah River Site well HSB 85A at coordinates North 33° 17’ 6.548”, West 81° 39’

17.7448”. The groundwater sample was provided by the Savannah River Technology 

Center in Aiken, South Carolina. The location selected for the groundwater represents 

“clean” groundwater, which does not contain any radionuclide contamination at 

concentrations above natural background levels. Also, this sampling location has 

background data associated with it that was collected as part of the environmental 

monitoring program at the Savannah River Site.

2.2 Methods for Analysis and Characterization of Groundwater and 

Soil Samples

The following method descriptions were taken, with the permission of the lead authors, 

from reports published by the PNNL Applied Geology and Geochemistry Group, such as 

Deutsch et al. (2004) and Serne et al. (2004). 
2-4

2.2.1 Analysis of Groundwater Samples

2.2.1.1 pH and Conductivity

The pH values of the groundwater samples from the Hanford Site, Nye County, and 

Savannah River Site were measured using a solid-state pH electrode and a pH meter 

calibrated with buffers bracketing the expected range. This measurement is similar to 

Test Methods for Evaluating Solid Wastes: Physical/Chemical Methods SW-846 9040B 

(EPA 1995). Electrical conductivity was measured and compared to potassium chloride 

standards with a range of 0.001 M to 1.0 M. The pH and conductivity subsamples were 

filtered prior to analysis. The basic unit of conductivity is the siemens (S), formerly 

called the mho.

2.2.1.2 Alkalinity

The alkalinity of the groundwater samples from the Hanford Site, Nye County, and 

Savannah River Site were measured using standard titration. A volume of standardized 

sulfuric acid (H2SO4) was added to the sample to an endpoint of pH 8.3 and then an 

endpoint of pH 4.5. The volume of H2SO4 needed to achieve each endpoint is used to 

calculate the phenolphthalein (OH- + CO3

2-

) and total (OH- + HCO3

- + CO32-

) alkalinity 

as calcium carbonate (CaCO3). The alkalinity procedure is similar to Standard Method 

2320 B (Clesceri et al. 1998). 

2.2.1.3 Anions

Analyses of dissolved anions in groundwater samples from the Hanford Site, Nye 

County, and Savannah River Site were measured using an ion chromatograph. Bromide, 

carbonate, chloride, fluoride, nitrate, phosphate, and sulfate were separated on a Dionex 

AS17 column with a gradient elution technique from 1 mM to 35 mM KOH and 

measured using a conductivity detector. This methodology is similar to Method 9056 in 

Test Methods for Evaluating Solid Wastes: Physical/Chemical Methods EPA SW-846

(EPA 1994b) with the exception of using gradient elution with NaOH.

2.2.1.4 Total Carbon

Total carbon contents of the groundwater samples from the Hanford Site, Nye County, 

and Savannah River Site were measured using a Shimadzu Carbon analyzer Model 

TOC-V csn that is equipped with an autosampler. The method used of measuring the 

carbon content of the groundwater samples is described in PNNL Technical Procedure

AGG-TOC-001 (PNNL 2004),2 and is similar to EPA Method 9060 (Total Organic 

Carbon) in Test Methods for Evaluating Solid Wastes: Physical/Chemical Methods EPA 

SW-846 (EPA 1986). The adequacy of the system performance was confirmed by 

analyzing for known quantities of a liquid carbon standard.

 2 PNL. 2004. “PNNL Technical Procedure AGG-TOC-001 [Operating of Carbon Analyzer (TOC-V + 

SSM-5000A + ASI (Shimadzu))].” Pacific Northwest National Laboratory, Richland, Washington.
2-5

2.2.1.5 Cations and Trace Metals

Analyses of major cations, such as Al, Ca, Fe, K, Mg, Mn, Na, and Si, dissolved in the 

groundwater samples from the Hanford Site, Nye County, and Savannah River Site were 

completed by inductively coupled plasma-optical emission spectroscopy (ICP-OES) 

(EPA Method 6010B, EPA 1996). Trace metals analyses, including Ag, As, Cd, Cr, Mo, 

Pb, Ru, Se, and U, were completed by inductively coupled plasma-mass spectroscopy 

(ICP-MS) using a method that is similar to EPA Method 6020 (EPA 1994a). For both 

ICP-OES and ICP-MS, high-purity calibration standards were used to generate 

calibration curves and to verify continuing calibration during the analysis. Multiple 

dilutions of selected samples were made and analyzed to investigate and correct for 

matrix interferences. The ICP-MS results are reported as total element concentration in 

terms of the specific isotope measured. The instrument software converts the 

concentration of an isotope of an element to the total concentration of the element based 

on the distribution of isotopes in the natural environment. For example, the total Cr 

concentration is reported from the raw count rates for both 52Cr and 53Cr isotopes based 

on taking the raw counts and dividing by the fraction of 52Cr and 53Cr found in nature to 

yield estimates of total Cr in the sample. (Note that these are stable isotopes of the 

elements).

2.2.2 Characterization and Analysis of Bulk Soil Samples

2.2.2.1 X-ray Diffraction

The primary crystalline minerals present in each bulk soil sample were identified using a 

Scintag X-ray powder diffraction (XRD) unit equipped with a Pelter thermoelectrically 

cooled detector and a copper X‐ray tube. The diffractometer was operated at 45 kV and 

40 mA. Individual scans were obtained from 2 to 65° 2θ with a dwell time of 2 seconds. 

Scans were collected electronically and processed using the JADE® XRD patternprocessing software. Identification of the mineral phases in the background-subtracted 

patterns was based on a comparison of the XRD patterns measured for the sludge samples 

with the mineral powder diffraction files (PDFTM) published by the Joint Committee on 

Powder Diffraction Standards (JCPDS) International Center for Diffraction Data (ICDD).

2.2.2.2

 

Elemental Analysis by X-ray Fluorescence

Elemental analysis of the bulk soil samples was determined by X-ray fluorescence 

(XRF). The XRF analyses were completed for PNNL by staff at the GeoAnalytical 

Laboratory in the Department of Geology at Washington State University (1228 Webster 

Physical Sciences Building, Pullman, Washington 99164-2812) using a Thermo-ARL 

Advant’XP+ automated spectrometer. The sequential, wavelength dispersive 

spectrometer contains a Rh-target X-ray tube operated at 60 kV, 60 mA. Samples were

prepared for XRF analysis using a lithium tetraborate flux fusion method which includes 

double fusing (for homogeneity) in carbon crucibles at 1000°C. Preparation time and 

analytical time were both approximately one hour per sample. Except for now using 
2-6

diamond-impregnated metal disks to improve the lapping of specimen surfaces to 

flatness, the details of sample preparation are essentially those described in Johnson et al. 

(1999).

2.2.2.3 Particle Size Distribution

American Society for Testing and Materials (ASTM) procedures ASTM D1140-00 

(ASTM 2000) (Standard Test Methods for Amount of Material in Soils Finer Than the 

No. 200 [75 μm] Sieve) and D422-63 (ASTM 2003) (Standard Test Method for ParticleSize Analysis of Soils) were used for particle size analysis of the soil samples from the 

Hanford Site, Nye County, and Clemson University locations. In ASTM D422-63, a 

sedimentation process using a hydrometer is used to determine the distribution of particle 

sizes smaller than 75 μm, while sieving was used to measure the distribution of particle 

sizes larger than 53 μm (retained on a No. 270 sieve). A No. 10 sieve, which has sieve 

size openings of 2.00 mm, was first used to remove the fraction larger than “very coarse”

prior to particle size analysis.

2.2.2.4 Moisture Content

Gravimetric water contents of the soil samples from the Hanford Site, Nye County, and 

Clemson University locations were determined using PNNL procedure PNL-MA-567-

DO-1 (PNL 1990).3 This procedure is based on the ASTM Method D2216-98 (Test 

Method for Laboratory Determination of Water (Moisture) Content of Soil and Rock by 

Mass) (ASTM 1998). One representative subsample of each soil sample was placed in 

tared containers, weighed, and dried in an oven at 105°C (221°C) until constant weight 

was achieved, which took at least 24 hours. The containers then were removed from the 

oven, sealed, cooled, and weighed. At least two weighings, each after a 24-hour heating, 

were performed to ensure that all moisture was removed. The gravimetric water content 

was computed as the percentage change in soil weight before and after oven drying.

2.2.2.5 Cation Exchange Capacity

The cation exchange capacity (CEC) of the soil samples from the Hanford Site, Nye 

County, and Clemson University locations were determined using the method described 

in ASA (1982). This method is particularly suited to arid land soils, including those 

containing carbonate, gypsum, and zeolites. This procedure involves two steps. The first

consists of saturation of the cation exchange sites with Na by reaction of the soil with pH 

8.2, 60% ethanol solution of 0.4-N NaOAc–0.1 N NaCl. This is then followed by 

extraction of 0.5 N MgNO3. The concentrations of dissolved Na and Cl are then 

measured in the extracted solution so that the dissolved Na from the excess saturation 

solution, carried over from the saturation step to the extraction step, is deducted from the 

total Na. This provides amount of exchangeable Na, which is equivalent to the CEC.

 3 PNL. 2000. “PNNL Technical Procedure SA-7. Water Content.” Procedure approved in May 2000, in 

Procedures for Ground-Water Investigations, PNL-MA-567, Pacific Northwest National Laboratory, 

Richland, Washington.
2-7

2.2.2.6 Carbon Content

The total carbon and the inorganic carbon contents of the soil samples from the Hanford 

Site, Nye County, and Clemson University locations were measured using a Shimadzu 

Carbon Analyzer Model TOC-V csn. The method used to measure the carbon contents of 

the soil samples is similar to ASTM Method E1915-01 (Test Methods for Analysis of 

Metal Bearing Ores and Related Materials by Combustion Infrared Absorption 

Spectrometry) (ASTM 2001). Known quantities of calcium carbonate standards were 

analyzed to verify that the instrumentation was operating properly. Inorganic carbon 

content was determined through calculations performed using the microgram per-sample 

output data and sample weights. The organic carbon content of the soil samples was 

calculated by subtracting the inorganic carbon contents from the respective total carbon 

contents for each sample.

2.2.2.7 1:1 Soil:Water Extracts

The water-soluble inorganic constituents in the soil samples from the Hanford Site, Nye 

County, and Clemson University locations were determined using a 1:1 soil:deionizedwater extract method. The extracts were prepared by adding an exact weight of 

deionized water to approximately 60 to 80 g of soil subsample. The weight of deionized 

water needed was calculated based on the weight of the field-moist samples and their 

previously determined moisture contents. The sum of the existing moisture (porewater) 

and the deionized water was fixed at the mass of the dry soil. The appropriate amount of 

deionized water was added to screw cap jars containing the soil samples. The jars were 

sealed and briefly shaken by hand, then placed on a mechanical orbital shaker for one 

hour. The samples were allowed to settle until the supernatant liquid was fairly clear. 

The supernatant was carefully decanted and filtered (passed through 0.45 μm 

membranes) for conductivity, pH, anion, carbon, and cation analyses. More details can 

be found in Rhoades (1996) and within Methods of Soils Analysis - Part 3 (ASA 1996). 

The methods used for the pH, conductivity, anion, carbon, and cation analyses are the 

same as those described above for the analysis of the groundwater samples. The results 

for the analyses of the 1:1 soil:water extracts for the three soil samples are reported in 

terms of both units per gram of soil and units per milliliter of pore water. This 

conversion is based on a soil-to-water ratio of 1.0.

2.3 Results of Analyses and Characterization of Groundwater and Soil 

Samples

Table 2.1 lists the tables and figures that contain the results of the analyses and 

characterization studies of the groundwater, soil, and 1:1 soil:water extract samples from 

the Hanford Site, Nye County, Savannah River, and Clemson University locations. 

In the following tables, analyses are listed for primary and duplicate samples of one of 

the three groundwater, soil, and 1:1 soil:water extract samples. A duplicate sample is 

selected at random when a set of samples is submitted for analyses as part of the standard 
2-8

laboratory quality-assurance operating procedures used by the analytical laboratories in 

the PNNL Applied Geology and Geochemistry Group. 

Table 2.1. Tables and Figures Containing the Results of the Analyses and 

Characterization Studies of the Groundwater, Soil, and 1:1 Soil:Water 

Extract Samples from the Hanford Site, Nye County, and Savannah 

River/Clemson University Locations

Type of Sample Table or

Figure Numbers Results Reported

Groundwater Samples

Table 2.2 pH and Conductivity

Table 2.3 Alkalinity at pH 8.3 and 4.5 Endpoints

Table 2.4 Dissolved Anions by IC

Table 2.5 Total Dissolved Carbon

Table 2.6 Dissolved Macro and Trace Elements by 

ICP-OES

Table 2.7 and 

Table 2.8 Dissolved Trace Metals by ICP-MS

Soil Samples

Figure 2.1, Figure 2.2, 

and

Figure 2.3

XRD patterns for soil samples from Hanford, 

Nye County, and Clemson University Sites, 

respectively

Table 2.9 and 

Table 2.10

Elemental analyses of bulk soil samples by 

XRF 

Table 2.11 Particle Size of Bulk Solid

Table 2.12 Moisture Content

Table 2.13 Cation Exchange Capacity (CEC)

Table 2.14 Contents of Total, Inorganic, and Organic 

Carbon

1:1 Soil:Water Extracts

Table 2.15 pH and Conductivity

Table 2.16 Alkalinity at pH 8.3 and 4.5 Endpoints

Table 2.17 Dissolved Anions by IC

Table 2.18 and 

Table 2.19

Dissolved Macro and Trace Elements by 

ICP-OES

Table 2.20 and 

Table 2.21

Dissolved Trace Metals by ICP-MS
2-9

The background-subtracted XRD patterns for the soil samples from the Hanford Site, 

Nye County, and Clemson University Site are shown in Figure 2.1, Figure 2.2, and 

Figure 2.3, respectively. Each XRD pattern is shown as a function of degrees 2θ based 

on Cu Kα radiation (λ=1.5406 Å). The vertical axis in each pattern represents the 

intensity in counts per second (cps) of the XRD peaks. In order to conveniently scale the 

XRD patterns on the vertical axes and visualize the minor XRD peaks, it was necessary 

to cut off the intensity of the most intense XRD peak in each pattern. These intensity 

cutoffs are labeled on each XRD pattern and correspond to the largest XRD peak for 

feldspar for the Hanford Site soil sample, and for quartz for the Nye County and Clemson 

University Site soil samples. 

At the bottom of each XRD pattern, one or more schematic database (PDF) patterns 

considered for phase identification are also shown for comparison purposes. The height 

of each line in the schematic PDF patterns represents the relative intensity of an XRD 

peak (i.e., the most intense [the highest] peak has a relative intensity [I/Io] of 100%). As 

noted previously, a crystalline phase typically must be present at greater than 5 wt% of 

the total sample mass (greater than 1 wt% under optimum conditions) to be readily 

detected by XRD.

The following minerals were identified in the soil samples (see Figure 2.1, Figure 2.2, 

and Figure 2.3):

• Hanford Site soil – quartz, plagioclase feldspar, microcline feldspar, amphibole, 

chlorite, and mica

• Nye County soil – quartz, plagioclase feldspar, microcline feldspar, amphibole, 

zeolite, and mica

• Clemson University Site soil – quartz

More detailed analyses would be required to refine the identities of the general mineral 

identifications (e.g., plagioclase, amphibole, zeolite, mica, etc.) to specific compositions. 

The soil sample from Nye County appears to contain a zeolite mineral. Although the 

pattern for this soil sample (Figure 2.2) was a good match to the database pattern for 

clinoptilolite (PDF 47-1870), other compositions of zeolites may also match this pattern. 

Several reflections in the XRD patterns for soil samples from the Clemson University 

Site (i.e., 19.96, 23.99, 25.48, 25.67, 34.95, 37.74, 38.54 °2θ) could not be identified. 

Additional XRD patterns measured at slower scanning rates would be needed to identify 

the minerals associated with these reflections. Some of the unassigned reflections in the 

XRD pattern for the Clemson University soil appear to match anthropogenic organic 

compounds, but this identification is problematic. To test this possibility, a sample of the 

Clemson University soil was heated for approximately 5 hours at 500°C in an attempt to 

decompose any organic solids present in the sample, and then re-analyzed by X-ray 

diffraction. The results however were inconclusive because there were no differences in 

the XRD patterns for the Clemson University soil before and after heating at 500°C. 
2-10

Table 2.2. pH and Conductivity Values for the Groundwater Samples

Groundwater Samples pH Conductivity*

(mS/cm)

Hanford Site 8.43 0.544

Hanford Site (duplicate) 8.35 0.543

Nye County 8.42 0.197

Savannah River Site 8.75 1.052

*

 The basic unit of conductivity is the siemens (S), formerly 

called the mho.

Table 2.3. Alkalinity Values for the Groundwater Samples

Groundwater Samples

Alkalinity at

pH 8.3 Endpoint

Total Alkalinity at 

pH 4.5 Endpoint

(mg CaCO3/L)

Hanford Site 0.0* 168.36

Hanford Site (duplicate) 0.0 167.63

Nye County 15.372 290.60

Savannah River Site 0.0 81.984

* Alkalinity values of 0.0 mg CaCO3/L at the pH 8.3 endpoint indicate that the 

starting pH values of the respective groundwater samples were near or less than 

pH 8.3. 

Table 2.4. Concentrations of Dissolved Anions in the Groundwater Samples

Groundwater 

Samples

Br- CO3

2- Cl- F- NO3- PO43- SO42-

(μg/mL)

Hanford Site <0.48 222.7 20.07 0.42 13.76 <0.51 79.75

Hanford Site 

(duplicate)

<0.48 220.9 20.00 0.42 13.66 <0.51 79.49

Nye County <0.48 389.1 44.96 5.91 2.47 <0.51 187.0

Savannah River Site <0.48 59.38 2.60 0.09 <0.43 <0.51 5.29

Table 2.5. Concentrations of Total Dissolved Carbon in the Groundwater Samples

Groundwater Samples

Total Dissolved Carbon

#1 #2 Average

(mg/L)

Hanford Site 39.85 40.14 40.00

Nye County 68.40 68.33 68.37

Savannah River Site 17.83 17.74 17.79
2-11

Table 2.6. Concentrations of Dissolved Macro and Trace Metals in the Groundwater 

Samples as Determined by ICP-OES

Groundwater 

Samples

Al As B Ba Be Bi Ca Cd Co Cr

(μg/L)

Hanford Site ND <1.3E+02 <1.3E+02 1.8E+02 <6.3E+01 ND 5.8E+04 ND <2.5E+01 <6.3E+01

Hanford Site 

(duplicate) ND <1.3E+02 <1.3E+02 1.5E+02 <6.3E+01 ND 5.9E+04 ND <2.5E+01 <6.3E+01

Nye County ND <1.3E+02 8.8E+02 8.1E+01 <6.3E+01 ND 1.9E+04 ND <2.5E+01 <6.3E+01

Savannah River 

Site ND <1.3E+02 <1.3E+02 6.3E+01 <6.3E+01 ND 3.3E+04 ND ND <6.3E+01

Cu Fe K Li Mg Mn Mo Na Ni P

(μg/L)

Hanford Site <2.5E+02 <2.5E+01 7.6E+03 <2.5E+03 2.2E+04 ND <2.5E+01 2.4E+04 <2.5E+01 <3.1E+02

Hanford Site 

(duplicate) <2.5E+02 <2.5E+01 7.7E+03 <2.5E+03 2.2E+04 ND ND 2.4E+04 <2.5E+01 <3.1E+02

Nye County <2.5E+02 <2.5E+01 1.4E+04 <2.5E+03 1.7E+04 ND <2.5E+01 2.1E+05 <2.5E+01 <3.1E+02

Savannah River 

Site <2.5E+02 <2.5E+01 <1.3E+03 <2.5E+03 8.2E+02 ND <2.5E+01 1.7E+03 <2.5E+01 <3.1E+02

Pb S Se Si Sr Ti Tl V Zn Zr

(μg/L)

Hanford Site ND ND <5.0E+02 2.9E+04 2.3E+02 ND ND <2.5E+02 3.7E+02 <2.5E+01

Hanford Site 

(duplicate) ND ND <5.0E+02 2.9E+04 2.3E+02 ND ND <2.5E+02 3.5E+02 ND

Nye County ND ND <5.0E+02 2.2E+04 5.3E+02 ND ND ND <6.3E+01 ND

Savannah River 

Site ND ND <5.0E+02 1.3E+04 8.5E+01 ND ND <2.5E+02 <6.3E+01 <2.5E+01

Table 2.7. Concentrations of Dissolved Trace Metals in the Groundwater Samples as 

Determined by ICP-MS

Groundwater 

Samples

Ag – total based on As – total 

based on Cd – total based on Cr – total based on 

107Ag* 109Ag 75As 111Cd 114Cd 52Cr 53Cr

(μg/L)

Hanford Site <1.25E-01 <1.25E-01 2.51E+00 <5.00E-01 <5.00E-02 2.05E+00 2.24E+00

Hanford Site 

(duplicate) <1.25E-01 <1.25E-01 2.85E+00 <5.00E-01 <5.00E-02 1.99E+00 2.55E+00

Nye County <1.25E-01 <1.25E-01 4.02E+01 <5.00E-01 <5.00E-02 <1.25E+00 1.53E+00

Savannah River 

Site <1.25E-01 <1.25E-01 <2.50E+00 <5.00E-01 <5.00E-02 <1.25E+00 1.28E+00

* Note that all isotopes indicated are non-radioactive.
2-12

Table 2.8. Concentrations of Dissolved Trace Metals in the Groundwater Samples as 

Determined by ICP-MS (Continued) 

Groundwater 

Samples

Mo – total based on Pb – total based on Ru – total based on Se – total 

based on

U – total 

based on

95Mo** 98Mo 206Pb 208Pb 101Ru 102Ru 82Se 238U

(μg/L)

Hanford Site <2.50E+00 1.26E+00 <1.25E+00 <1.25E+00 <1.25E+00 <1.25E+00 <2.50E+01 2.32E+00

Hanford Site 

(duplicate) <2.50E+00 <1.25E+00 <1.25E+00 <1.25E+00 <1.25E+00 <1.25E+00 <2.50E+01 2.30E+00

Nye County 1.34E+01 1.24E+01 <1.25E+00 <1.25E+00 <1.25E+00 <1.25E+00 <2.50E+01 3.78E+00

Savannah River 

Site <2.50E+00 <1.25E+00 <1.25E+00 1.32E+00 <1.25E+00 <1.25E+00 <2.50E+01 <5.00E-02

* Note that all isotopes indicated are non-radioactive.

Figure 2.1. Background-Subtracted XRD Pattern for Hanford Site Soil Sample

°2θ

5 10 15 20 25 30 35 40 45 50 55 60 65

Relative Intensity (cps)

Hanford Site

Soil Sample

Quartz

Plagioclase

Microcline

Amphibole

Mica

Chlorite

Intensity Cutoff
2-13

Figure 2.2. Background-Subtracted XRD Pattern for Nye County Soil Sample

°2θ

5 10 15 20 25 30 35 40 45 50 55 60 65

Relative Intensity (cps)

Nye County

Soil Sample

Quartz

Plagioclase

Microcline

Amphibole

Mica

Zeolite

Intensity Cutoff
2-14

Figure 2.3. Background-Subtracted XRD Pattern for Clemson University Site Soil 

Sample

5 10 15 20 25 30 35 40 45 50 55 60 65

Relative Intensity (cps)

Clemson University Site

Soil Sample

Quartz

Intensity Cutoff

°2θ
2-15

Table 2.9. Concentrations of Major Elements in Bulk Soil Samples as Determined by 

XRF

Al2O3 CaO FeO* K2O MgO MnO** Na2O P2O5 SiO2 TiO2 Total

(wt% – dry basis, normalized to 100%)

Hanford Site 13.91 3.78 6.40 2.13 2.24 0.108 2.40 0.182 67.70 1.147 100.00

Nye County 13.44 6.23 2.04 4.31 1.55 0.064 3.00 0.071 68.95 0.347 100.00

Clemson University 

Site 0.90 0.02 0.28 0.04 0.03 0.007 0.00 0.047 98.27 0.328 99.93

LOI*** Al2O3 CaO FeO* K2O MgO MnO** Na2O P2O5 SiO2 TiO2 Total

(%) (wt% – normalized to 100% minus LOI)

Hanford Site 4.82 13.21 3.59 6.08 2.03 2.12 0.103 2.28 0.173 64.32 1.090 95.00

Nye County 7.91 12.35 5.73 1.88 3.97 1.42 0.059 2.75 0.065 63.37 0.319 91.91

Clemson 

University 1.04 0.89 0.02 0.27 0.04 0.03 0.007 0.00 0.047 97.19 0.325 98.90

*

 Concentrations of total iron are normalized to FeO. XRF determines the concentrations of total iron and 

manganese, but does not provide any data regarding the oxidation states of such redox sensitive elements present in 

the sample.

** Concentrations of total manganese are normalized to MnO. *** LOI = Loss on ignition

Table 2.10. Concentrations of Trace Elements in Bulk Soil Samples as Determined by 

XRF

Ba Ce Cr Cu Ga La Nb Nd Ni

(ppm)

Hanford Site 648 70 44 20 17 35 13 31 23

Nye County 694 95 13 9 17 53 19 36 10 

Clemson University

Site 24 46 17 4 2 18 6 15 3

Pb Rb Sc Sr Th V Y Zn Zr

(ppm)

Hanford Site 16 69 15 311 10 138 30 70 254 

Nye County 24 136 6 413 19 24 27 53 256

Clemson University

Site 7 4 0 3 7 10 13 21 445
2-16

Table 2.11. Particle Size Analysis of the Bulk Soil Samples

Soil Samples

Gravel

(x > 2 mm)

Sand

(2 > x > 0.050 mm)

Silt/Clay

(x < 0.050 mm)

(wt%)

Hanford Site 0.0 82.92 17.08

Nye County 0.0 98.99 1.01

Clemson University Site 0.0 97.50 2.50

Table 2.12. Moisture Contents of the Bulk Soil Samples

Soils

Moisture (wt%)

First 

Weighing

Second

Weighing

Hanford Site 2.49 2.39

Nye County 2.51 2.30

Nye County (duplicate) 2.57 2.38

Clemson University Site 0.16* 0.13*

* Soils from this site falls under USDA-APHIS because of the potential for 

fire-ant contamination. Prior to distribution for characterization, this soil

had therefore been heat-treated by either heating in a forced air oven at 

110°-125°C for 16 to 48 h, or autoclaving at temperatures 110°C and 15 

pounds pressure for a minimum of 30 min.

Table 2.13. Cation Exchange Capacity (CEC) Values for the Soil Samples

Soils CEC (meq/100 g)

#1 #2 #3 Average

Hanford Site 38.2 35.1 ND* 36.7

Nye County 27.3 28.5 29.3 28.4

Clemson University Site 27.8 23.6 ND* 25.7

* ND – Third analysis of CEC not determined for these soil samples.
2-17

Table 2.14. Carbon Contents of the Soil Samples

Soil

Total Carbon Total Inorganic

Carbon

Total 

Inorganic

Carbon As 

CaCO3

Total Organic 

Carbon

(by difference)

#1 #2 Ave #1 #2 Ave Ave Ave

(wt%)

Hanford Site 0.36 0.36 0.36 0.09 0.09 0.09 0.72 0.27

Nye County 1.10 1.08 1.09 0.97 0.98 0.97 8.11 0.12

Nye County 

(duplicate) 1.38 1.38 1.38 1.26 1.22 1.24 10.31 0.14

Clemson University 

Site 0.38 0.38 0.38 0.0 0.0 0.0 0.0 0.38

Table 2.15. pH and Conductivity Values for the 1:1 Soil:Water Extracts

1:1 Soil:Water Extracts pH Conductivity 

(mS/cm)

Conductivity (mS/cm)

Dilution Corrected (in 

Pore Water)

Hanford Site 7.48 0.184 7.38

Nye County 8.07 0.400 15.94

Nye County (duplicate) 8.14 0.407 15.85

Clemson University Site 4.92 0.158 96.51

Clemson University Site (duplicate) 4.87 0.149 91.06

Table 2.16. Alkalinity Values for the 1:1 Soil:Water Extracts

1:1 Soil:Water

Extracts

Akalinity at

pH 8.3 

Endpoint

Total Alkalinity 

at pH 4.5 

Endpoint

Porewater Total Alkalinity 

at pH 4.5 Endpoint

Dilution Corrected

(in Pore Water)

(mg CaCO3/L)

Hanford Site 0.0* 85.644 3,436.0

Nye County 6.588 137.61 5,485.7

Nye County (duplicate) 5.124 142.74 5,557.3

Clemson University Site 0.0* 19.764 12,070**

Clemson University Site (duplicate) 0.0* 19.032 11,630**

* Alkalinity values of 0.0 mg CaCO3/L at the pH 8.3 endpoint indicate that the starting pH values of the 

respective extract samples were near or less than pH 8.3. ** Indicated dilution-corrected, porewater alkalinity values are likely in error by a considerable, but unknown, 

amount. Because these soil samples fell under USDA-APHIS and had been heat treated before submission 

characterization and analysis, calculations based on their low (essentially zero) moisture contents resulted 

in error in the calculated, dilution-corrected, porewater alkalinity values.
2-18

Table 2.17. Concentrations of Dissolved Anions in 1:1 Soil:Water Extract

1:1 Soil:Water

Extracts*

Br- CO3

2- Cl- F- NO3- PO43- SO42-

(μg/g soil)

Hanford Site <0.48 70.36 <0.236 0.16 2.50 NR** 1.36

Nye County <0.48 161.8 6.86 7.03 5.57 NR** 30.81

Nye County (duplicate) <0.48 162.0 6.92 7.07 5.20 NR** 30.69

Clemson University Site <0.46 <48.19 0.39 1.05 1.68 7.37 18.11

Clemson University Site (duplicate) <0.46 <48.21 0.40 2.65 1.76 7.90 19.04

(μg/mL pore water)

Hanford Site <19.30 2,823 <9.452 6.62 100.3 NR** 54.63

Nye County <19.17 6,446 273.5 280.4 222.0 NR** 1,228

Nye County (duplicate) <18.73 6,307 269.5 275.2 202.3 NR** 1,195

Clemson University Site <293.8 <30,540 246.5 665.0 1,066 4,671 11,480

Clemson University Site (duplicate) <294.0 <30,560 254.5 1678 1,115 5,006 12,070

* Pore water dilution factors were 40.12, 39.86, 38.93, 399.00, 610.81, and 611.12, respectively.

Dilution factor corrected - μg in water extract per mL pore water. ** NR = Values not reported because analyses of PO4

3-

 standard were outside the control limits.
2-19

Table 2.18. Concentrations (μg/g soil) of Dissolved Macro and Trace Metals in the 1:1 

Water Extracts as Determined by ICP-OES

1:1 Soil:Water

Extracts

Al As B Ba Be Bi Ca Cd Co Cr

(μg/g soil)

Hanford Site ND ND <2.5E+02 <1.2E-01 <2.5E-01 <1.2E+00 2.10E+01 ND <6.2E-01 <1.2E-01

Nye County <5.0E-01 ND <2.5E+02 <1.3E-01 <2.5E-01 <1.3E+00 5.40E+00 ND <6.3E-01 <1.3E-01

Nye County 

(duplicate) <5.0E-01 <5.0E+00 <2.5E+02 <1.3E-01 <2.5E-01 <1.3E+00 5.64E+00 ND <6.3E-01 <1.3E-01

Clemson 

University Site 2.95E+00 ND <9.6E-02 9.51E-02 <9.6E-03 <1.9E-01 1.29E+01 <9.6E-03 <1.9E-02 <9.6E-03

Clemson Univ 

Site (duplicate) 3.20E+00 ND <9.6E-02 7.40E-02 <9.6E-03 ND 1.38E+01 <9.6E-03 <1.9E-02 <9.6E-03

Cu Fe K Li Mg Mn Mo Na Ni P

(μg/g soil)

Hanford Site <2.5E+00 <5.0E-01 <6.2E+01 <1.2E+00 5.19E+00 ND <2.5E-01 <2.5E+00 <1.2E+00 <6.2E+00

Nye County <2.5E+00 <5.0E-01 <6.3E+01 <1.3E+00 2.44E+00 ND ND 8.20E+01 <1.3E+00 <6.3E+00

Nye County 

(duplicate) <2.5E+00 <5.0E-01 <6.3E+01 <1.3E+00 2.38E+00 ND <2.5E-01 8.36E+01 <1.3E+00 <6.3E+00

Clemson 

University Site <9.6E-02 6.85E-01 9.24E+00 <9.6E-02 4.74E+00 2.76E+00 <3.8E-02 5.09E-01 <1.9E-02 3.69E+00

Clemson Univ 

Site (duplicate) <9.6E-02 7.26E-01 9.78E+00 <9.6E-02 5.04E+00 2.92E+00 ND 5.53E-01 <1.9E-02 3.91E+00

Pb S Se Si Sr Ti Tl V Zn Zr

(μg/g soil)

Hanford Site ND <1.0E+01 ND <2.5E+01 7.89E-02 <2.5E-01 ND ND <1.2E-01 ND

Nye County <1.3E+00 1.15E+01 ND <2.5E+01 5.79E-02 <2.5E-01 ND <2.5E+00 1.65E-01 <2.5E-01

Nye County 

(duplicate) ND 1.11E+01 ND <2.5E+01 5.99E-02 ND ND <2.5E+00 <1.3E-01 ND

Clemson 

University Site <9.6E-02 8.36E+00 <3.9E-01 <1.9E+00 <1.9E-02 <4.8E-02 <1.9E-01 <9.6E-02 9.57E-02 <1.9E-02

Clemson Univ 

Site (duplicate) <9.6E-02 8.89E+00 <3.9E-01 <1.9E+00 <1.9E-02 <4.8E-02 <1.9E-01 <9.6E-02 7.87E-02 <1.9E-02
2-20

Table 2.19. Concentrations (μg/L pore water) of Dissolved Macro and Trace Metals in 

the 1:1 Water Extracts as Determined by ICP-OES

1:1 Soil:Water

Extracts

Al As B Ba Be Bi Ca Cd Co Cr

(μg/L pore water)

Hanford Site ND ND <1.0E+07 <5.0E+03 <1.0E+04 <5.0E+04 8.44E+05 ND <2.5E+04 <5.0E+03

Nye County <2.0E+04 ND <1.0E+07 <5.0E+03 <1.0E+04 <5.0E+04 2.15E+05 ND <2.5E+04 <5.0E+03

Nye County 

(duplicate) <1.9E+04 <1.9E+05 <9.7E+06 <4.9E+03 <9.7E+03 <4.9E+04 2.20E+05 ND <2.4E+04 <4.9E+03

Clemson 

University Site 1.87E+06 ND <6.1E+04 6.03E+04 <6.1E+03 <1.2E+05 8.17E+06 <6.1E+03 <1.2E+04 <6.1E+03

Clemson Univ 

Site (duplicate) 2.03E+06 ND <6.1E+04 4.69E+04 <6.1E+03 ND 8.74E+06 <6.1E+03 <1.2E+04 <6.1E+03

Cu Fe K Li Mg Mn Mo Na Ni P

(μg/L pore water)

Hanford Site <1.0E+05 <2.0E+04 <2.5E+06 <5.0E+04 2.08E+05 ND <1.0E+04 <1.0E+05 <5.0E+04 <2.5E+05

Nye County <1.0E+05 <2.0E+04 <2.5E+06 <5.0E+04 9.74E+04 ND ND 3.27E+06 <5.0E+04 <2.5E+05

Nye County 

(duplicate) <9.7E+04 <1.9E+04 <2.4E+06 <4.9E+04 9.25E+04 ND <9.7E+03 3.26E+06 <4.9E+04 <2.4E+05

Clemson 

University Site <6.1E+04 4.34E+05 5.85E+06 <6.1E+04 3.00E+06 1.75E+06 <2.4E+04 3.22E+05 <1.2E+04 2.34E+06

Clemson Univ 

Site (duplicate) <6.1E+04 4.60E+05 6.20E+06 <6.1E+04 3.19E+06 1.85E+06 ND 3.51E+05 <1.2E+04 2.48E+06

Pb S Se Si Sr Ti Tl V Zn Zr

(μg/L pore water)

Hanford Site ND <4.0E+05 ND <1.0E+06 3.17E+03 <1.0E+04 ND ND <5.0E+03 ND

Nye County <5.0E+04 4.56E+05 ND <1.0E+06 2.31E+03 <1.0E+04 ND <1.0E+05 6.57E+03 <1.0E+04

Nye County 

(duplicate) ND 4.34E+05 ND <9.7E+05 2.33E+03 ND ND <9.7E+04 <4.9E+03 ND

Clemson 

University Site <6.1E+04 5.30E+06 <2.4E+05 <1.2E+06 <1.2E+04 <3.1E+04 <1.2E+05 <6.1E+04 6.06E+04 <1.2E+04

Clemson Univ 

Site (duplicate) <6.1E+04 5.63E+06 <2.4E+05 <1.2E+06 <1.2E+04 <3.1E+04 <1.2E+05 <6.1E+04 4.99E+04 <1.2E+04
2-21

Table 2.20. Concentrations of Dissolved Macro and Trace Metals in 1:1 Water Extracts 

as Determined by ICP-MS

1:1 Soil:Water

Extracts

Ag – total 

based on 

As – total 

based on Cd – total based on Cr – total based on Mo – total based on

109Ag** 75As 111Cd 114Cd 52Cr 53Cr 97Mo 98Mo

(μg/g soil)

Hanford Site 2.09E-04 7.02E-03 <1.25E-04 <1.25E-04 <2.50E-03 <5.00E-03 2.35E-03 2.35E-03

Nye County 8.07E-05 3.94E-02 1.63E-04* 1.41E-04* <2.50E-03 <5.00E-03 1.31E-02 1.33E-02

Nye County 

(duplicate) 6.12E-05 3.89E-02 <1.25E-04* <1.25E-04* <2.50E-03 <5.00E-03 1.37E-02 1.39E-02

Clemson 

University Site <1.20E-04 5.88E-03 3.14E-04 3.16E-04 7.43E-03 6.80E-03 <1.20E-03 <1.20E-03

Clemson 

University Site 

(duplicate)

<1.21E-04 6.30E-03 3.33E-04 3.57E-04 8.32E-03 7.48E-03 <1.21E-03 <1.21E-03

(μg/L pore water)

Hanford Site 8.40E+00 2.82E+02 <5.01E+00 <5.01E+00 <1.00E+02 <2.01E+02 9.42E+01 9.42E+01

Nye County 3.22E+00 1.57E+03 6.50E+00* 5.62E+00* <9.97E+01 <1.99E+02 5.24E+02 5.31E+02

Nye County 

(duplicate) 2.38E+00 1.51E+03 <4.87E+00* <4.87E+00* <9.73E+01 <1.95E+02 5.34E+02 5.43E+02

Clemson 

University Site <7.64E+01 3.72E+03 1.99E+02 2.00E+02 4.71E+03 4.31E+03 <7.64E+02 <7.64E+02

Clemson 

University Site 

(duplicate)

<7.64E+01 4.00E+03 2.11E+02 2.26E+02 5.27E+03 4.74E+03 <7.64E+02 <7.64E+02

* Indicated values for each respective cadmium isotope are suspect because the values for the primary and duplicate 

extract samples are too dissimilar. 

** Note that all isotopes indicated are non-radioactive.
2-22

Table 2.21. Concentrations of Dissolved Trace Elements in 1:1 Water Extracts as 

Determined by ICP-MS (Continued) 

1:1 Soil:Water

Extracts

Pb – total based on Ru – total based on Se – total 

based on

U – total 

based on

206Pb** 208Pb 101Ru 102Ru 82Se 238U

(μg/g soil)

Hanford Site <1.25E-03 <2.50E-03 <5.00E-05 <5.00E-05 <5.00E-03 1.93E-04

Nye County <1.25E-03 <2.50E-03 <5.00E-05 <5.00E-05 <5.00E-03 1.92E-03

Nye County 

(duplicate) <1.25E-03 <2.50E-03 <5.00E-05 <5.00E-05 <5.00E-03 2.07E-03

Clemson University 

Site 5.43E-03 5.32E-03 <2.41E-04 <2.41E-04 1.29E-03 2.97E-03

Clemson University 

Site (duplicate) 6.16E-03 6.06E-03 <2.41E-04 <2.41E-04 1.41E-03 3.10E-03

(μg/L pore water)

Hanford Site <5.01E+01 <1.00E+02 <2.01E+00 <2.01E+00 <2.01E+02 7.73E+00

Nye County <4.98E+01 <9.97E+01 <1.99E+00 <1.99E+00 <1.99E+02 7.65E+01

Nye County 

(duplicate) <4.87E+01 <9.73E+01 <1.95E+00 <1.95E+00 <1.95E+02 8.05E+01

Clemson University 

Site 3.44E+03 3.37E+03 <1.53E+02 <1.53E+02 8.20E+02 1.88E+03

Clemson University 

Site (duplicate) 3.90E+03 3.84E+03 <1.53E+02 <1.53E+02 8.96E+02 1.96E+03

** Note that all isotopes indicated are non-radioactive.
2-23

2.4 References 

ASA (American Society of Agronomy). 1982. Methods of Soil Analysis. Part 2, 

Chemical and Microbiological Properties. SSSA Book Series 9 (Part 2), AL Page (eds.), 

Soil Science Society of America, Madison, Wisconsin.

ASA (American Society of Agronomy). 1996. Methods of Soil Analysis. Part 3, 

Chemical Methods. SSSA Book Series 5, DL Sparks (eds.), Soil Science Society of 

America, Madison, Wisconsin.

ASTM (American Society for Testing and Materials). 1998. Method D2216-98. 

Standard Test Method for Laboratory Determination of Water (Moisture) Content of Soil 

and Rock by Mass. American Society for Testing and Materials, West Conshohocken, 

Pennsylvania.

ASTM (American Society for Testing and Materials). 2000. Method D1140-00.

Standard Test Methods for Amount of Material in Soils Finer Than the No. 200 (75 μm) 

Sieve. American Society for Testing and Materials, West Conshohocken, Pennsylvania.

ASTM (American Society for Testing and Materials). 2001. Method E1915-01. Test 

Methods for Analysis of Metal Bearing Ores and Related Materials by Combustion 

Infrared Absorption Spectrometry. American Society for Testing and Materials, 

West Conshohocken, Pennsylvania.

ASTM (American Society for Testing and Materials). 2003. Method D422-63. 

Standard Test Method for Particle-Size Analysis of Soils (Revised 1998). American 

Society for Testing and Materials, West Conshohocken, Pennsylvania.

Clesceri LS, AE Greenberg, and AD Eaton. 1998. Standard Methods for the 

Examination of Water and Wastewater, 20th Edition. American Public Health 

Association, American Water Works Association, and Water Environment Federation, 

Washington, D.C.

DOE. 1999. Final Hanford Comprehensive Land-Use Plan Environmental Impact 

Statement. DOE/EIS-0222-F, U.S. Department of Energy, Washington, D.C. Online at:

http://www.hanford.gov/eis/hraeis/maintoc.htm

Deutsch WJ, KM Krupka, MJ Lindberg, KJ Cantrell, CF Brown, and HT Schaef. 2004. 

Hanford Tanks 241-C-203 and 241-C-204: Residual Waste Contaminant Release Model 

and Supporting Data. PNNL-14903, Pacific Northwest National Laboratory, Richland, 

Washington. 
2-24

EPA (U.S. Environmental Protection Agency). 1986. Method 9060. Total Organic 

Carbon. Test Methods for Evaluating Solid Wastes: Physical/Chemical Methods, EPA 

SW-846, Third Ed., Vol. I, Section C, Chapter 5 (Miscellaneous Test Methods), 

pp. 9060-1 to 9060-5, U.S. Environmental Protection Agency, Office of Solid Waste and 

Emergency Response, Washington, D.C. Available at: 

http://www.epa.gov/epaoswer/hazwaste/test/pdfs/9060.pdf

EPA (U.S. Environmental Protection Agency). 1994a. Method 6020. Inductively 

Coupled Plasma-Mass Spectrometry. Test Methods for Evaluating Solid Wastes: 

Physical/Chemical Methods, EPA SW-846, Third Ed., Vol. I, Section A, Chapter 3 

(Inorganic Analytes), pp. 6020-1 to 6020-18, U.S. Environmental Protection Agency, 

Office of Solid Waste and Emergency Response, Washington, D.C. Available at: 

http://www.epa.gov/epaoswer/hazwaste/test/pdfs/6020.pdf

EPA (U.S. Environmental Protection Agency). 1994b. Method 9056. Determination of 

Inorganic Anions by Ion Chromatography. Test Methods for Evaluating Solid Wastes: 

Physical/Chemical Methods, EPA SW-846, Third Ed., Vol. I, Section C, Chapter 5 

(Miscellaneous Test Methods), pp. 9056-1 to 9056-16, U.S. Environmental Protection 

Agency, Office of Solid Waste and Emergency Response, Washington, D.C. Available 

at: http://www.epa.gov/epaoswer/hazwaste/test/pdfs/9056.pdf 

EPA (U.S. Environmental Protection Agency). 1995. Method 9040B. pH Electrometric 

Measurement. Test Methods for Evaluating Solid Wastes: Physical/Chemical Methods, 

EPA SW-846, Third Ed., Vol. I, Section C, Chapter 8 (Methods for Determining 

Characteristics), pp. 9040B-1 to 9040B-5, U.S. Environmental Protection Agency, Office 

of Solid Waste and Emergency Response, Washington, D.C. Available at: 

http://www.epa.gov/epaoswer/hazwaste/test/pdfs/9040b.pdf

EPA (U.S. Environmental Protection Agency). 1996. Method 6010B. Inductively 

Coupled Plasma-Atomic Emission Spectrometry. Test Methods for Evaluating Solid 

Wastes: Physical/Chemical Methods, EPA SW-846, Third Ed., Vol. I, Section A, 

Chapter 3 (Inorganic Analytes), pp. 6010B-1 to 6010B-25, U.S. Environmental 

Protection Agency, Office of Solid Waste and Emergency Response, Washington, D.C. 

Available at: http://www.epa.gov/epaoswer/hazwaste/test/pdfs/6010b.pdf

HEIS. 1994. Hanford Environmental Information System. Environmental Information 

Systems Department, Fluor Hanford, Inc., Richland, Washington.

Johnson DM, PR Hooper, and RM Conrey. 1999. XRF Analysis of Rocks and Minerals

for Major and Trace Elements on a Single Low Dilution Li-tetraborate Fused Bead. 

Advances in X-ray Analysis, Vol. 41, JV Gilfrich TC Huang, CR Hubbard, IC Noyan, 

PK Predecki, DK Smith, and RL Snyder (eds.), p. 843-867. International Centre for 

Diffraction Data (ICDD), Newtown Square, Pennsylvania.
2-25

Napier BA, KM Krupka, MM Valenta, and TJ Gilmore. 2005. Soil and Groundwater 

Sample Characterization and Agricultural Practices for Assessing Food Chain Pathways 

in Biosphere Model. NUREG/CR-6881, U.S. Nuclear Regulatory Commission, 

Washington, D.C.

Napier BA, RJ Fellows, and KM Krupka. 2007. Soil-to-Plant Concentration Ratios for 

Assessing Food Chain Pathways in Biosphere Models. NUREG/CR-6941, U.S. Nuclear 

Regulatory Commission, Washington, D.C.

Rhoades JD. 1996. Salinity: Electrical Conductivity and Total Dissolved Solids. 

Methods of Soil Analysis, Part 3, JM Bigham (ed.), pp. 417-435. American Society of 

Agronomy, Madison, Wisconsin.

Serne RJ, BN Bjornstad, DG Horton, DC Lanigan, CW Lindenmeier, MJ Lindberg, 

RE Clayton, VL LeGore, RD Orr, IV Kutnyakov, SR Baum, KN Geiszler, MM Valenta, 

and TS Vickerman. 2004. Characterization of Vadose Zone Sediments Below the 

TX Tank Farm: Boreholes C3830, C3831, C3832 and RCRA Borehole 299 W10-27. 

PNNL-14594, Pacific Northwest National Laboratory, Richland, Washington. 

3-1

3.0 Speciation and Geochemistry of Radionuclides 

in Soil-Water Systems

3.1 Background

The concentrations, mobility, and bioavailability of radionuclides in surface and subsurface 

geologic systems4 are controlled by numerous hydrologic and geochemical processes. These 

primarily include the amount and nature of radionuclides present at the source; the rate of their 

release from the source; hydrologic factors, such as dispersion, advection, and dilution; and 

geochemical processes, such as aqueous complexation, oxidation/reduction (redox), 

adsorption/desorption and ion exchange, precipitation/dissolution, diffusion, colloid-facilitated 

transport, and anion exclusion. Additionally, in the uppermost layer of surface soil,5

Table 3.1

the mobility 

of radionuclides can also be increased by biological activity and by the drying and subsequent 

cracking of soils. Colloid-facilitated transport and anion exclusion have received considerable 

attention recently in that they can enhance the transport of certain radionuclides. However, these 

processes are hard to quantify, and the extent to which they occur is difficult to determine. The 

geochemical processes listed above are discussed in detail in sources such as Baes and Mesmer 

(1976), Garrels and Christ (1965), Langmuir (1997), Lindsay (1979), Morel (1983), Nordstrom 

and Munoz (1985), Sposito (1989, 1994), Stumm and Morgan (1981), Yariv and Cross (1979), 

and others, and the references cited therein. , taken from the U.S. Environmental 

Protection Agency (EPA 1999a), summarizes the mechanism, anticipated effect on radionuclide 

mobility, and key environmental factors associated with each of these geochemical processes. 

The reader is cautioned that the importance of colloid-facilitated migration, especially in aquifer 

systems that do not involve fracture flow of groundwater, is still a subject of debate. 

Some radionuclides, such as technetium, uranium, and plutonium, may be present in more than 

one oxidation state in the environment. The adsorption and precipitation behavior of different 

oxidation states of a particular radionuclide are usually very different. For example, in 

environmental systems, the most stable oxidation states of technetium are +7 and +4 under 

oxidizing and reducing geochemical conditions, respectively. The chemical behavior of 

technetium in these two oxidation states differs drastically. Dissolved Tc(VII) exists as 

pertechnetate anion, TcO4

-

, over the complete pH range of natural waters under oxic conditions. 

Because the pertechnetate anion is highly soluble and is not strongly sorbed, it is highly mobile 

in most oxidizing systems. Under reducing conditions, however, Tc(IV) exists as hydrolyzed 

cations and is relatively immobile in the absence of strongly complexing ligands. 

Technetium(IV) is highly sorbed and forms the sparingly soluble TcO2nH2O solid.

 4 Surface and subsurface geologic systems include soils, sediments, surface waters, soil pore waters, groundwaters, 

and geological rock formations.

5 The terms “soil” and “sediment” have particular meanings, depending on one’s technical discipline. For example, 

“soil” is often limited to referring to the top layer of the earth’s surface, suitable for plant life. The term “sediment” 

is usually reserved for transported and deposited particles derived from soil, rocks, or biological material. In this 

report, the term “soil” is used to as a general term to refer to all unconsolidated geologic materials.
3-2

Table 3.1. Summary of Chemical Processes Affecting the Mobility of Radionuclides

Geochemical

Process Mechanism

Affect on

Radionuclide Mobility Important Factors

Aqueous 

complexation

Reaction where an 

aqueous molecular unit 

(ion) acts as a central 

group to attract and 

form a close 

association with other 

atoms or molecules

May enhance mobility 

or retardation, 

depending on 

radionuclide and 

geochemical conditions

• Function of pH and redox conditions

• Complexation may lower the 

potential for adsorption and/or 

increase solubility, both of which 

can enhance the potential for 

mobility

• Complexes may more readily bond to 

soils and thus retard migration

• Organic ligands from humic 

materials can be present in 

significant concentrations and 

dominate radionuclide complexation 

in some systems

Oxidation/ 

Reduction (redox) 

reactions

Reaction where 

electrons are 

transferred completely 

from one species to 

another

May enhance mobility 

or retardation, 

depending on 

radionuclide and 

geochemical conditions

• Change in redox status changes 

aqueous speciation, which may 

increase or decrease adsorption and 

solubility

• If the redox status is sufficiently low 

to induce the precipitation of sulfide 

minerals, reprecipitation of some

radionuclides may be expected

• The more difficult to predict mobility 

of redox-sensitive species because 

many redox reactions are kinetically 

slow in natural waters, and several 

elements may never reach 

equilibrium between their various 

valence states

Adsorption/ 

desorption and ion 

exchange

Special case of a 

complexation reaction 

where there is a net 

accumulation of a 

radionuclide at the 

interface between a 

solid phase and an 

aqueous solution 

phase; does not 

include the 

development of a 

three-dimensional 

molecular structure

Enhances retardation • Occurs primarily in response to 

electrostatic attraction

• Very dependent on pH and 

mineralogy

• Anion adsorption is greatest at low 

pH and decreases with increasing pH

• Cation adsorption is greatest at high 

pH and decreases with deceasing pH

• Some radionuclides may be present 

as cations or anions, depending on 

pH 

• Totally-to-partially reversible; 

decline in dissolved radionuclide 

concentration may result in 

desorption and release of adsorbed 

radionuclide to water

• Likely key process controlling 

radionuclide mobility in areas where 

chemical equilibrium exists
3-3

Table 3.1. (contd)

Geochemical

Process Mechanism Affect onRadionuclide Mobility Important Factors

Precipitation/ 

dissolution

Special case of a 

complexation reaction

in which the complex 

formed by two or more 

aqueous species is a 

solid with threedimensional molecular 

structure

Enhances retardation • Very dependent on pH and redox 

conditions

• Totally-to-partially reversible; decline 

in dissolved radionuclide concentration 

may result in dissolution of precipitated 

radionuclide to groundwater

• Likely process where chemical 

nonequilibium exists, an area where 

high radionuclide concentrations exist, 

or where steep pH and/or redox 

gradients exist

Diffusion Molecular process of

transport of matter in 

the absence of bulk 

flow

Enhances mobility • Flux of matter due to diffusion is 

proportional to concentration gradient

Colloidfacilitated 

transport

Radionuclides 

associated with 

suspended fine-grained 

material (smaller than 

clay size) that may be 

transported with 

flowing soil pore water 

and groundwater

Enhances mobility • Little information on occurrence, 

mineralogical and physicochemical 

properties, or conditions conducive to 

the generation of mobile colloids

• May originate from the dispersion of 

soils, decementation of secondary 

mineral phases, and/or the precipitation 

of groundwater constituents

• Difficult-to-collect colloids from 

subsurface in a manner that minimizes 

or eliminates sampling artifacts

• Difficult-to-unambiguously delineate 

between the radionuclides in the 

mobile-aqueous and mobile-solid 

phases

Anion 

exclusion

Occurs when the 

diffuse double layer, an 

extension of a particle’s 

negative surface charge 

into the surrounding 

solution, repulses 

anions

Enhances mobility • By excluding anions from the diffuse 

double layer, where water is relatively 

immobile, anions restricted to the faster 

moving pore water, resulting in an 

average rate of anion transport greater 

than the average pore-water velocity 

defined by Darcy’s Law

• More pronounced with higher CEC, i.e., 

negative charge, of the soil or rock.

CEC = cation exchange capacity.
3-4

Adsorption/desorption (including ion exchange) and precipitation/dissolution are considered the 

most important processes affecting radionuclide interactions with soils. Precipitation/dissolution 

is more likely to be an important process where elevated concentrations of dissolved 

radionuclides exist, such as in the near-field environment of radioactive waste disposal facilities 

or the spill sites of radionuclide-containing wastes or where steep pH or redox gradients exist. 

Adsorption/desorption will likely be the key process controlling radionuclide retardation in areas 

where trace concentrations of dissolved radionuclides exist, such as those associated with farfield environments of disposal facilities or spill sites or in areas of where soils are to be irrigated 

using radionuclide-contaminated water. 

Adsorption occurs primarily in response to electrostatic attraction. The degree of adsorption of 

ions is strongly governed by the pH of the solution because the magnitude and polarity of the net 

surface charge of a solid changes with pH. Mineral surfaces become increasingly more 

negatively charged as pH increases. The pH at which the net charge of solid surface changes 

from positive to negative is called the point-of-zero charge (PZC), or zero point of charge (ZPC) 

(Stumm and Morgan 1981; Langmuir 1997). At pH values greater than the pHPZC, deprotonation 

of surface hydroxyl groups results in a net negative charge. At pH values less than the pHPZC, 

the surface becomes protonated, which results in a net positive surface charge. Therefore, 

adsorption of radionuclides present as anions is expected to be greatest at low pH and decreases 

with increasing pH. The adsorption of cations, on the other hand, is greatest at high pH and 

decreases with decreasing pH.

Throughout this section, “sorption” will be used as a generic term devoid of mechanism and used 

to describe the partitioning of dissolved aqueous-phase constituents to a solid phase. When a 

radionuclide is associated with a geologic material, however, it is usually not known if the 

radionuclide is adsorbed onto the surface of the solid, absorbed into the structure of the solid, 

precipitated as a three-dimensional molecular structure on the surface of the solid, or partitioned 

into the organic matter (Sposito 1989). The term “sorption” encompasses all of the above 

processes.

The sorption of radionuclides on soils is frequently quantified by the partition (or distribution) 

coefficient (Kd). The Kd parameter is a factor related to the partitioning of a radionuclide 

between the solid and aqueous phases and is defined as the ratio of the quantity of the adsorbate 

adsorbed per mass of solid to the amount of the adsorbate remaining in solution at equilibrium. 

Radionuclides that adsorb very strongly to soil have large Kd values (typically greater than 

100 mL/g) compared to those values for radionuclides that are not significantly retarded by 

adsorption. Radionuclides that do not adsorb to soil and migrate essentially at the same rate as 

the waterflow have Kd values near 0 mL/g. The Kd model is a simple but not particularly robust 

sorption model. However, the Kd metric is the most common measure used in hydrologic 

transport and biosphere codes to describe the extent to which contaminants are sorbed to soils. 

The primary advantage of the Kd model is that it is easily inserted into computer codes to 

quantify the reduction in the extent of transport of a radionuclide relative to groundwater. The 

Kd is an empirical unit of measurement that attempts to account for various chemical and 

physical retardation mechanisms that are influenced by a myriad of variables. As such, the Kd

model is often the subject of criticism. The technical issues, complexities, and shortcomings 
3-5

of the Kd approach to describing radionuclide sorption to soils are discussed in detail in 

EPA (1999a) and the references cited therein.

3.2 Eh-pH Species Predominance Diagrams

Computer modeling methods were used to calculate from equilibrium thermodynamic principals, 

the distributions of dominant aqueous species, and potential solubility controls for the 

environmentally important oxidation states of each of the selected radionuclides. The results of 

these speciation and solubility calculations for each radionuclide were graphically presented as a 

series of Eh-pH (or Pourbaix) diagrams. The theory behind the calculation of Eh-pH diagrams is 

discussed by Garrels and Christ (1965), Langmuir(1997), Nordstrom and Munoz (1985), and 

others.

The Eh-pH diagrams were calculated at 25°C (298 K) and 1 atm pressure using the The 

Geochemist’s Workbench® (Version 8.0.8) software package and the expanded thermodynamic 

database file “thermo.com.V8.R6+.dat” provided with the software package. The Lawrence 

Livermore National Laboratory (LLNL) developed the thermodynamic database file originally 

for use with the EQ3/6 geochemical model. This database includes the thermodynamic values 

for the uranium and americium species given, respectively, in the extensive reviews by Grenthe 

et al. (1992) and Silva et al. (1995). However, the database file predates publication of the 

extensive reviews of thermodynamic values for technetium species by Rard et al. (1999), 

neptunium and plutonium by Lemire et al. (2001), and related data updates in Guillaumont et al. 

(2003). For the calculations made here, the thermo.com.V8.R6+.dat file was supplemented with 

thermodynamic data for the following aqueous species; TcCO3(OH)2

0 and TcCO3(OH)3- (Rard 

et al. 1999), CaUO2(CO3)3

2-

, MgUO2(CO3)3

2-

, and Ca2UO2(CO3)3

0 (Dong and Brooks 2006).

The Geochemist’s Workbench® software package calculates Eh pH diagrams for the speciation 

of a dissolved element (e.g., uranium) using input values of “activity,” which is often referred to 

as an “effective concentration” (Krauskopf 1979), for the concentration of the element of 

interest. Therefore, the concentrations of contaminants of interest (Am, I, Np, Pu, Tc, and U), 

cations and anions were used for the sake of simplicity as “activity” input values for the Eh-pH 

speciation calculations. A set of diagrams were calculated for representative groundwater 

chemistries from each of three locals; the Hanford Site, Nye County and the Savannah River Site 

(Napier et al. 2005), see Tables 2.2 - 2.8. The activity of the contaminants of interest used in the 

calculations was 1 × 10-8 M. The radionuclide concentration of 1×10-8 mol/L was arbitrarily 

selected to help demonstrate the importance of aqueous complexation, redox, and possible 

solubility reactions for each radionuclide. Although radionuclide concentrations in the far-field 

environments, such as deep groundwater and irrigated water systems, will likely be lower than 

1×10-8 mol/L, the dominant aqueous species that are calculated at lower concentrations of each 

radionuclide will not differ significantly from those plotted in the Eh-pH diagrams in following 

section. At trace concentrations, the stability relationships between dissolved species do not 

change significantly with changes in the concentrations of the metal or radionuclide of interest; 

however, changes in the concentrations of the metal or radionuclide of interest can significant 

impact on the stability fields of solid phases. In some cases, the formation of certain 

thermodynamically stable species was suppressed because formation of these species is known to 
3-6

be kinetically inhibited under most environmentally relevant conditions. Examples include; 

nitride (N3

-

), thiocyanate (SCN-), and a number of organic ligands such as formate, propanoate, 

and butanoate.

The Eh-pH diagrams shown display the stability fields for the dominant aqueous species. Each 

diagram contains dashed black lines from coordinates (Eh 1.2 V–pH 0) to (Eh 0.4 V–pH 14) and 

from (Eh 0.0 V–pH 0 to Eh -0.8 V–pH 14) that represent the Eh-pH boundaries for the 

dissociation of water to its gaseous components at 25°C and 1 atm pressure. At Eh-pH values 

above the upper black dashed line, water breaks down to oxygen gas. At Eh-pH values below 

the lower black dashed line, water breaks down to hydrogen gas. The redox conditions for 

essentially all environmental systems occur in the region within these water-stability limits. 

Similar examples of Eh-pH diagrams were presented in Robertson et al. (2003). The examples 

in that work were based on a “standard” groundwater composition for a generic location. The 

results presented here are for the specific groundwaters for the three sites.

3.2.1 Technetium

The behavior of technetium in environmental systems has been reviewed extensively by others. 

Reviews include Lieser (1993), Gu and Schulz (1991), Sparks and Long (1987), Meyer et al. 

(1985), Beasley and Lorz (1984), Coughtrey et al. (1983), Onishi et al. (1981), Wildung et al. 

(1979), Ames and Rai (1978), and others. Hughes and Rossotti (1987) review in detail the 

solution chemistry of technetium. Technetium exists in oxidation states from +7 to -1. In 

natural environments, the most stable oxidation states of technetium are +7 and +4 under 

oxidizing and reducing conditions, respectively. Other oxidation states are encountered chiefly 

in complex compounds (Mazzi 1989). 

The environmental behavior of technetium under oxic conditions has been studied extensively. 

Figure 3.1 shows Eh-pH diagrams for the three site groundwaters. The diagram was calculated 

at 25oC using a concentration of 1×10-8 mol/L total dissolved technetium for each of the three 

specific groundwater conditions. Dissolved technetium is present in oxic environmental systems 

as the aqueous Tc(VII) oxyanion species TcO4

- over the complete pH range of natural waters. 

The TcO4

- anion is essentially nonadsorptive, i.e., Kd values are ≈0 mL/g, at near neutral and 

basic pH values and is also highly soluble. The concentration of Tc(VII) in groundwater will 

therefore not be limited by adsorption or solubility processes and thus will be highly mobile in 

oxic environments. However, under reducing soil and geologic conditions, technetium is 

expected to be reduced to the +4 valance state due to biotic and abiotic reactive processes, such 

as surface-mediated reduction of Tc(VII) by Fe(II). Technetium(IV) is considered to be 

essentially immobile, because it is sparingly soluble and highly sorbed to iron and aluminum 

oxides and clays.

Under reducing conditions in the absence of dissolved carbonate, technetium aqueous speciation 

is dominated at pH values greater than 2 by the neutral Tc(IV) species TcO(OH)2o (aq). In 

carbonate-containing waters, Tc(IV) carbonate complexes, such as TcCO3(OH)2o (aq) and 

TcCO3(OH)3

-

, become important aqueous complexes of technetium (Rard et al. 1999). 

Thermodynamic calculations suggest the possible formation of Tc3+ at very low pH values,

extremely reducing conditions. Technetium(IV) is sparingly soluble and highly sorbed and is 

therefore considered to be essentially immobile in reducing environments. 
3-7

The three panels of this figure are similar to that for generic groundwater in Robertson et al. 

(2003), but show the influence of the increases in alkalinity (calcium carbonate) in the three site 

waters compared to the generic site.

3.2.2 Iodine

The environmental behavior of iodine has been reviewed by others, such as Lieser and 

Steinkopff (1989), Whitehead (1984), Coughtrey et al. (1983), and Ames and Rai (1978). 

Although the environmental chemistry of iodine is normally assumed to be simple and well 

known, recent studies suggest that the fate and mobility of iodine in environmental systems may 

be more complex than expected. This complexity is caused by the multiple redox states of 

iodine that may exist under oxidizing conditions. The -1, +5, and molecular I2 oxidation states 

are those most relevant for iodine in environmental systems. 

Figure 3.2 is an Eh-pH diagram that shows the dominant aqueous species of iodine predicted to 

be present for the three site groundwaters at 25oC and a total concentration of 1×10-8 mol/L 

dissolved iodine. In most aqueous environments, iodine is present as the iodide ion, I-

. The 

stability range of I- extends almost over the entire pH and Eh range for the thermodynamic 

stability of water. In marine and highly oxidizing environments, such as surface waters and 

some oxygenated shallow groundwaters, iodine may be present in the +5 oxidation state as the 

iodate ion, IO3

-

, which becomes the protonated species HIO3 under very acidic conditions. 

Under oxidizing, acidic conditions, I3

- (aq) may form from the reduction of IO3- or the oxidation 

of I-

. 

This figure is very similar to that for iodine in Robertson et al. (2003). 

3.2.3 Uranium

The geochemical behavior of uranium has received extensive study due to the importance of 

uranium as an energy source and as a geochronology indicator. There have been several 

published reviews of the geochemical behavior of uranium. The review by Langmuir (1978) and 

an updated discussion in Langmuir (1997) are particularly noteworthy. In 1999, an extensive 

compilation of detailed reviews on the mineralogical, geochemical, and environmental behavior 

of uranium was published in Burns and Finch (1999). More recent work has focused on waters 

with high concentrations of calcium; these are of particular interest in relation to the three site 

groundwaters that are all relatively “hard” and of low pH.

Uranium can exist in the +3, +4, +5, and +6 oxidation states in aqueous environments. 

Uranium(VI), i.e., uranyl, UO2

2+, and U(IV) are the most common oxidation states of uranium in 

natural environments. Uranium will exist in the +6 oxidation state under oxidizing to mildly 

reducing environments. Uranium(IV) is stable under reducing conditions and is considered 

relatively immobile because U(IV) forms sparingly soluble minerals, such as uraninite (UO2). 

Dissolved U(III) easily oxidizes to U(IV) under most reducing conditions found in nature. The 

U(V) aqueous species (UO2

+

) readily disproportionates to U(IV) and U(VI). As with the redox 

of technetium, the reduction of U(VI) to U(IV) by abiotic and biotic processes has recently 

received considerable attention because the oxidation state of uranium has a significant effect on 

its mobility in waste streams and the natural environment. These reaction processes are the basis 

for certain remediation technologies, such as permeable barriers composed of zero-valent iron 

particles, i.e., as metallic iron, or sodium-dithionite-reduced soils. Microbial reduction of U(VI) 
3-8

has also been suggested as a potential mechanism for removal of uranium from contaminated 

waters and soils, e.g., Lovley (1993, 1995). Suzuki and Banfield (1999) provide a detailed 

review and extensive reference list on the interactions between uranium and microorganisms. 

Recent studies have shown the importance of calcium compounds with uranium; the forms 

CaUO2(CO3)3

2-

, MgUO2(CO3)3

2-

, and Ca2UO2(CO3)3

0 were identified as important by Bernhard 

et al (2001) and elucidated by Dong and Brooks (2006).

The three panels of Figure 3.3 differ significantly from that in Robertson et al. (2003) for 

uranium. This result occurs because the three site groundwaters are all significantly more basic 

(higher pH) and contain more dissolved calcium than the generic water used by Robertson et al. 

As a result, the Ca2UO2(CO3)3

0 form is identified as being essentially completely dominant under 

essentially all Eh-pH conditions for these waters. 

3.2.4 Plutonium

The geochemical behavior of plutonium in natural systems has been reviewed by EPA (1999b), 

Onishi et al. (1981), Ames and Rai (1978), and others. Plutonium can exist in the +3, +4, +5, 

and +6 oxidation states under most environmental conditions (Allard and Rydberg 1983). Under 

oxidizing conditions, Pu(IV), Pu(V), and Pu(VI) are common, whereas Pu(III) and Pu(IV) would 

exist under reducing conditions. 

The dominant aqueous species of plutonium are shown for the three site groundwaters as a 

function of Eh-pH conditions in Figure 3.4. The Eh-pH diagram was calculated using a 

concentration of 1×10-8 mol/L total dissolved plutonium and the ligand concentrations listed in 

Tables 2.2 – 2.8. As indicated in Figure 3.4, the Pu(IV) is the dominant oxidation state 

throughout most of the diagram. Pu(HPO4)4

4- is the dominant species from low pH values up to 

a pH of approximately 8, whereas Pu(OH)4o (aq) is predicted to be most stable at pH values 

greater than 8 except under highly oxidizing conditions. Plutonium can exist in +4, +5, and +6 

oxidation states under oxidizing conditions (Keeney-Kennicutt and Morse 1985) as shown in 

Figure 4. However, a number of investigators believe that Pu(V) is the dominant oxidation state 

of plutonium under oxidizing conditions (Nelson and Orlandini 1979; Aston 1980; Bondietti and 

Trabalka 1980; Rai et al. 1980b).

Dissolved plutonium can form stable complexes with a variety of inorganic and organic ligands 

(Cleveland 1979). Plutonium is expected to form stronger complexes with dissolved carbonate, 

sulfate, phosphate, and fluoride, relative to those with ligands such as chloride and nitrate. 

Plutonium can also form strong mixed hydroxy-carbonate ligand complexes [e.g., 

Pu(OH)2(CO3)2

2-

] (Yamaguchi et al. 1994; Tait et al. 1995). 

The three panels of Figure 3.4 are similar to that for generic groundwater in Robertson et al. 

(2003), but show the influence of the increases in alkalinity (calcium carbonate) in the three site 

waters compared to the generic site.

3.2.5 Neptunium

The environmental chemistry and mobility of neptunium in surface water, groundwater, and 

geologic environments has been reviewed by others, such as Silva and Nitsche (1995), Tanaka 

et al. (1992), Lieser and Mühlenweg (1988), Coughtrey et al. (1984), Thompson (1982), Onishi 

et al. (1981), and Ames and Rai (1978). Neptunium may exist in the +3, +4, +5, +6, and 
3-9

+7 valence states, but only the +4, +5, and possibly +6 states are relevant to natural 

environments. Neptunium(VI), such as NpO2(CO3)2

4- is stable only in highly oxidizing solutions 

and is therefore not important under most environmental conditions. Neptunium(V) exists in 

oxidizing environmental systems and is considered relatively mobile because Np(V) aqueous 

species do not readily adsorb to soil, and Np(V) solids are quite soluble. Neptunium(IV) occurs 

under reducing conditions and is less mobile than Np(V). Like U(IV) and Pu(IV), Np(IV) may 

form sparingly soluble oxide and hydroxide solids that limit the mobility of Np(IV) under 

reducing conditions. 

The thermodynamic data for neptunium aqueous species and solids are limited and not well 

known relative to other radionuclides. Lemire et al. (2001) have published an extensive, detailed 

review of the chemical thermodynamics of neptunium. However, as noted above, the 

thermodynamic values compiled in their review were not included in the thermodynamic 

database used to calculate the Eh-pH diagrams. Figure 3.5 is an Eh-pH diagram that shows the 

dominant aqueous species for dissolved neptunium in the three site groundwaters. The diagram 

was calculated at 25oC using a concentration of 1×10-8 mol/L total dissolved neptunium and the 

ligand concentrations listed above. Np(HPO4)5

6-

, calculates to be the dominant Np(IV) aqueous 

species at pH values less than pH 8.5. Under reducing conditions, the hydroxyl complex

Np(OH)4o(aq) is the dominant Np(IV) aqueous complex at pH values greater than 8. Under more 

oxidizing conditions, Np(V) species become dominant at higher pH values. Neptunyl ion, 

NpO2

+

, tends to be the dominant species under oxidizing conditions and near neutral pHs. At 

higher pH values, anionic Np(V) carbonate complexes, such as NpO2CO3

- and NpO2(CO3)35-

, are 

predicted to be the aqueous complexes under oxidizing conditions. 

For the higher pH values, the three panels of Figure 3.5 are similar to that for generic 

groundwater in Robertson et al. (2003). The regions of lower pH show the influence of the 

increases in alkalinity (calcium carbonate) in the three site waters compared to the generic site.

3.2.6 Americium

The environmental behavior of americium has been reviewed by Silva and Nitsche (1995), 

Coughtrey et al. (1984), Onishi et al. (1981), Ames and Rai (1978), and others. Moulin et al. 

(1988, 1992) review the aqueous speciation of Am(III) in natural waters and in the presence of 

humic substances in natural waters, respectively. Silva et al. (1995) have published an extensive, 

detailed critical review of the chemical thermodynamics of americium aqueous species and 

solids. Americium can exist in the +3, +4, +5, and +6 oxidation states. However, Am(III) is the 

most stable and important oxidation state in environmental systems. The higher oxidation states 

are strong oxidizing agents and stable only in systems containing no oxidizable compounds 

(Ames and Rai 1978).

Figure 3.6 is an Eh-pH diagram that shows the dominant aqueous species of americium for the 

three site groundwaters. The diagram was calculated at 25oC using a total concentration of 

1×10-8 mol/L dissolved americium and dissolved ligand concentrations given in Tables 2.2–2.8. 

Americium is present in the +3 oxidation state in all of the dominant species predicted to be 

stable for the Eh-pH region of environmental interest. The AmH2PO4

2+ is the dominant aqueous 

species at moderately to highly acidic conditions. At near neutral to alkaline pH conditions, 

Am(III) carbonate and hydroxyl complexes will dominate the aqueous speciation of Am(III). 
3-10

Aqueous complexes, such as Am(CO3)3

3-

, will be increasingly important with increasing 

concentrations of dissolved carbonate at alkaline pH conditions.

The three panels of this figure are similar to that for generic groundwater in Robertson et al. 

(2003). The panel for the Savannah River site is most similar; the other two sites have a higher 

concentration of sulfate ion than the generic water used in Robertson et al. (2003). The presence 

of the increased sulfate ion concentrations results in the addition of a narrow band of stability for 

AmSO4

+ for the pH region around 5.
3-11

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.5

0

.5

1

pH

Eh (volts)

Hanford Site

TcO4

-

TcCO3(OH)2

0

TcCO3(OH)3

-

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.5

0

.5

1

pH

Eh (volts)

Hanford Site

TcO4

-

TcCO3(OH)2

0

TcCO3(OH)3

-

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Nye County

25°C

TcCO3(OH)2

0

TcO4

-

TcCO3(OH)3

-

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Nye County

25°C

TcCO3(OH)2

0

TcO4

-

TcCO3(OH)3

-

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Savannah River Site

25°C

TcO4

-

TcCO3(OH)2

0

TcO(OH)2

0

Tc3+

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Savannah River Site

25°C

TcO4

-

TcCO3(OH)2

0

TcO(OH)2

0

Tc3+

Figure 3.1. Eh-pH Diagram Showing Dominant Aqueous Species of Technetium (calculated at 1×10-8 mol/L diss
3-12

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Hanford Site

I

-

IO3

-

HIO3

-

I

3

-

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Hanford Site

I

-

IO3

-

HIO3

-

I

3

-

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Nye County

25°C

IO3

-

I

-

HIO3

-

I

3

-

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Nye County

25°C

IO3

-

I

-

HIO3

-

I

3

-

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Savannah River Site

25°C

IO3

-

I

-

I

3

-

HIO3

-

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Savannah River Site

25°C

IO3

-

I

-

I

3

-

HIO3

-

Figure 3.2. Eh-pH Diagram Showing Dominant Aqueous Species of Iodine (calculated at 1×10-8 mol/L dissol
3-13

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Hanford Site

Ca2UO2(CO3)3

0

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Hanford Site

Ca2UO2(CO3)3

0

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Nye County

25°C

Ca2UO2(CO3)3

0

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Nye County

25°C

Ca2UO2(CO3)3

0

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Savannah River Site

25°C

Ca2UO2(CO3)3

0

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Savannah River Site

25°C

Ca2UO2(CO3)3

0

Figure 3.3. Eh-pH Diagram Showing Dominant Aqueous Species of Uranium (calculated at 1×10-8 mol/L di
3-14

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Hanford Site

Np(HPO4)5

6-

Np(OH)4

0

NpO2(CO3)3

5-

NpO2

+ NpO2(CO3)2

3-

NpO2(CO3)3

4-

NpO2CO3

-

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Hanford Site

Np(HPO4)5

6-

Np(OH)4

0

NpO2(CO3)3

5-

NpO2

+ NpO2(CO3)2

3-

NpO2(CO3)3

4-

NpO2CO3

-

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Nye County

25°C

Np(HPO4)5

6-

NpO2CO3

-

Np(OH)4

0

NpO2

+ NpO2(CO3)2

3-

NpO2(CO3)3

4-

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Nye County

25°C

Np(HPO4)5

6-

NpO2CO3

-

Np(OH)4

0

NpO2

+ NpO2(CO3)2

3-

NpO2(CO3)3

4-

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Savannah River Site

25°C

Np(HPO4)5

6-

Np(OH)4

0

NpO2

+

NpO2CO3

-

NpO2(CO3)2

3-

NpO2(CO3)3

5-

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Savannah River Site

25°C

Np(HPO4)5

6-

Np(OH)4

0

NpO2

+

NpO2CO3

-

NpO2(CO3)2

3-

NpO2(CO3)3

5-

Figure 3.4. Eh-pH Diagram Showing Dominant Aqueous Species of Neptunium (calculated at 1×10-8 mol/L d
3-15

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Hanford Site

Pu(OH)4

0

Pu(HPO4)4

4-

PuOH2+

PuSO4

+

PuO2

+

PuO2(CO3)2

2-

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Hanford Site

Pu(OH)4

0

Pu(HPO4)4

4-

PuOH2+

PuSO4

+

PuO2

+

PuO2(CO3)2

2-

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Nye County

25°C

Pu(HPO4)4

4-

Pu(OH)4

0

PuO2(CO3)2

2-

Pu(SO4)2

-

PuOH2+

PuO2

+

(PuO2)3(OH)5

+

PuO2F3

-

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Nye County

25°C

Pu(HPO4)4

4-

Pu(OH)4

0

PuO2(CO3)2

2-

Pu(SO4)2

-

PuOH2+

PuO2

+

(PuO2)3(OH)5

+

PuO2F3

-

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Savannah River Site

25°C

Pu(HPO4)4

4-

Pu(OH)4

0

PuO2(CO3)2

2-

PuO2

+

PuOH2+

Pu3+

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Savannah River Site

25°C

Pu(HPO4)4

4-

Pu(OH)4

0

PuO2(CO3)2

2-

PuO2

+

PuOH2+

Pu3+

Figure 3.5. Eh-pH Diagram Showing Dominant Aqueous Species of Plutonium (calculated at 1×10-8 mol/L di
3-16

0 2 4 6 8 10 12 14

–.2

–.4

–.6

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Hanford Site

AmH2PO4

2+

AmSO4

+

AmCO3

+

Am(CO3)2

-

Am(CO3)3

3-

0 2 4 6 8 10 12 14

–.2

–.4

–.6

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Hanford Site

AmH2PO4

2+

AmSO4

+

AmCO3

+

Am(CO3)2

-

Am(CO3)3

3-

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Nye County

25°C

AmH2PO4

2+

AmSO4

+

AmCO3

+

Am(CO3)2

-

Am(CO3)3

3-

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Nye County

25°C

AmH2PO4

2+

AmSO4

+

AmCO3

+

Am(CO3)2

-

Am(CO3)3

3-

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Savannah River Site

25°C

AmH2PO4

2+

AmCO3

+

Am(CO3)3

3-

Am(OH)2

+

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

–.2

–.4

–.6

–.8

0

.8

.6

.4

.2

1

1.2

pH

Eh (volts)

Savannah River Site

25°C

AmH2PO4

2+

AmCO3

+

Am(CO3)3

3-

Am(OH)2

+

Figure 3.6. Eh-pH Diagram Showing Dominant Aqueous Species of Americium (calculated at 1×10-8 mol/L di
3-17

3.3 References 

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Chemistry, ACS Symposium Series 216, eds. WT Carnall and GR Choppin, pp. 275-295. 

American Chemical Society, Washington, D.C.

Ames LL, and D Rai. 1978. Radionuclide Interactions with Soil and Rock media. 

Volume 1: Processes Influencing Radionuclide Mobility and Retention, Element 

Chemistry and Geochemistry, and Conclusions and Evaluations. EPA 520/6-78-007-a, 

U.S. Environmental Protection Agency, Las Vegas, Nevada.

Aston SR. 1980. Evaluation of Chemical Forms of Plutonium in Seawater. Marine 

Chemistry 8:317-326.

Baes CF, Jr. and RE Mesmer. 1976. The Hydrolysis of Cations. John Wiley and Sons, 

New York.

Beasley TM and HV Lorz. 1984. A Review of the Biological and Geochemical 

Behavior of Technetium in the Marine Environment. In Technetium in the Environment, 

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Bernhard G, Geipel G, Reich T, Brendler V, Amayri S, Nitsche H. 2001. Uranyl(VI) 

carbonate complex formation: Validation of the Ca2UO2(CO3)3(aq.) species. Radiochim. 

Acta 89: 511–518.

Bondietti EA and JR Trabalka. 1980. Evidence for Plutonium(V) in an Alkaline, 

Freshwater Pond. Radioanalytical Letters 43:169-176.

Burns PC and R Finch, eds. 1999. Uranium: Mineralogy, Geochemistry and the 

Environment. Reviews in Mineralogy, vol. 38. Mineralogical Society of America, 

Washington, D.C.

Cleveland JM. 1979. The Chemistry of Plutonium. American Nuclear Society, 

LaGrange Park, Illinois.

Coughtrey PJ, D Jackson, CH Jones, P Kane, and MC Thorne. 1984. Radionuclide 

Distribution and Transport in Terrestrial and Aquatic Ecosystems. A Critical Review of 

Data. AA Balkema, Boston, Massachusetts.

Coughtrey PJ, D Jackson, and MC Thorne. 1983. Radionuclide Distribution and 

Transport in Terrestrial and Aquatic Ecosystems. A Critical Review of Data. 

AA Balkema, Rotterdam, Netherlands.
3-18

Dong WM and SC Brooks. 2006. Determination of the formation constants of ternary 

complexes of uranyl and carbonate with alkaline earth metals (Mg2+, Ca2+, Sr2+, and Ba2+) 

using anion exchange method. Environmental Science and Technology

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Garrels RM and CL Christ. 1965. Solutions, Minerals, and Equilibria. Freeman, 

Cooper and Co., San Francisco, California.

Grenthe I, J Fuger, RJM Konings, RJ Lemire, AB Muller, C Nguyen-Trung, and 

H Wanner. 1992. Chemical Thermodynamics 1: Chemical Thermodynamics of 

Uranium. North-Holland, Elsevier Science Publishing Company, Inc., New York.

Gu B and RK Schulz. 1991. Anion Retention in Soil: Possible Application to Reduce 

Migration of Buried Technetium and Iodine. NUREG/CR-5464, U.S. Nuclear 

Regulatory Commission, Washington, D.C.

Guillaumont R, FJ Mompean, T Fanghänel, J Fuger, I Grenthe, V Neck, DA Palmer, and 

ML Rand. 2003. Chemical Thermodynamics, Volume 5: Chemical Thermodynamics of 

Uranium, Neptunium, Plutonium, Americium, and Technetium. Elsevier Science 

Publishing Company, New York.

Hughes MA and FJC Rossotti. 1987. A Review of Some Aspects of the Solution 

Chemistry of Technetium. AERE-R 12820, University of Oxford, Oxford, England.

Keeney-Kennicutt WL and JW Morse. 1985. The Redox Chemistry of Pu(V)O2

+

Interaction with Common Mineral Surfaces in Dilute Solutions and Seawater. 

Geochimica. Cosmochimica. Acta. 49:2577-2588.

Krauskopf KB. 1979. Introduction of Geochemistry. McGraw-Hill Book Company, 

New York, New York.

Langmuir D. 1978. Uranium Solution-Mineral Equilibria at Low Temperatures with 

Applications to Sedimentary Ore Deposits. Geochimica. et Cosmochimica. Acta.

42:547-569.

Langmuir D. 1997. Aqueous Environmental Geochemistry. Prentice Hall, Upper Saddle 

River, New Jersey.

Lemire RJ, J Fuger, H Nitsche, P Potter, MH Rand, J Rydbrg, K Spahiu, JC Sullivan, 

WJ Ullman, P Vitorge, and H Wanner. 2001. Chemical Thermodynamics, Volume 4: 

Chemical Thermodynamics of Neptunium and Plutonium. Elsevier Science Publishing 

Company, Inc., New York.
3-19

Lieser KH. 1993. Technetium in the Nuclear Fuel Cycle, in Medicine and in the 

Environment. Radiochimica. Acta. 63:5–8.

Lieser KH and U Mühlenweg. 1988. Neptunium in the Hydrosphere and in the 

Geosphere. I. Chemistry of Neptunium in the Hydrosphere and Sorption of Neptunium 

from Groundwaters on Sediments under Aerobic and Anaerobic Conditions. 

Radiochimica. Acta. 44/45:129–133.

Lieser KH and Th Steinkopff. 1989a. Chemistry of Radioactive Cesium in the 

Hydrosphere and in the Geosphere. Radiochimica. Acta. 46:39–47.

Lindsay WL. 1979. Chemical Equilibria in Soils. John Wiley and Sons, New York.

Lovley DR. 1993. Dissimilatory Metal Reduction. Annual Rev. Microbiol. 47:263–290.

Lovley DR. 1995. Bioremediation of Organic and Metal Contaminants with 

Dissimilatory Metal Reduction. J. Indust. Microbio. 14:85–93.

Mazzi U. 1989. The Coordination Chemistry of Technetium in its Intermediate 

Oxidation States. Polyhedron 8:1683–1688.

Meyer RE, WD Arnold, and FI Case. 1985. Valence Effects on the Adsorption of 

Nuclides on Rocks and Minerals II. NUREG/CR-4114, U.S. Nuclear Regulatory 

Commission, Washington, D.C.

Morel FMM. 1983. Principles of Aquatic Chemistry. John Wiley and Sons, NY.

Moulin V, P Robouch, P Vitorge, and B Allard. 1988. Environmental Behavior of 

Americium(III) in Natural Waters. Radiochimica. Acta. 44/45:33–37.

Moulin V, J Tits, and G Ouzounian. 1992. Actinide Speciation in the Presence of Humic 

Substances in Natural Water Conditions. Radiochimica. Acta. 58/59:179–190.

Napier BA, KM Krupka, MM Valenta, and TJ Gilmore. 2005. Soil and Groundwater 

Sample Characterization and Agricultural Practices for Assessing Food Chain Pathways 

in Biosphere Models. NUREG/CR-6881, U.S. Nuclear Regulatory Commission, 

Washington, D.C.

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ANL-79-65, Argonne National Laboratory, Argonne, Illinois.

Nordstrom DK and JL Munoz. 1985. Geochemical Thermodynamics. The 

Benjamin/Cummings Publishing Co., Inc., Menlo Park, California.
3-20

Onishi Y, RJ Serne, EM Arnold, CE Cowan, and FL Thompson. 1981. Critical Review: 

Radionuclide Transport, Sediment Transport, and Water Quality Mathematical 

Modeling; and Radionuclide Adsorption/Desorption Mechanisms. NUREG/CR-1322 

U.S. Nuclear Regulatory Commission, Washington, D.C.

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Environment. J. Environ. Quality 9:417–420.

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Chemical Thermodynamics of Technetium, eds. MCA Sandino and E Östhols. NorthHolland, Elsevier Science Publishing Company, Inc., New York.

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3-21

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4-1

4.0 Soil-to-Plant Uptake

The Nuclear Regulatory Commission (NRC) is tasked with the determination of risks 

associated with long-term storage of nuclear waste, and processing by-products, at 

various locations within the United States. Current models for the calculation of such 

risks to humans and the environment assess the potential for transfer and 

(bio)concentration of contaminant radionuclides. The models depend on factors in soil or 

water which have significant spatial physical and chemical heterogeneity. These 

calculations are entirely dependent on experimentally derived factors obtained from 

laboratory and field studies. The numbers and types of these studies, however, are 

frequently limited in scope, or otherwise constrained in the environmental conditions 

under which they are performed thus limiting the accuracy of the final estimation. The 

study described in this section sought to provide additional data on some of the isotopes 

of concern determined in a previous review (Robertson et al. 2003)

The isotopes of concern, neptunium-237 (237Np) and iodine-125 (125I), were selected 

based on conflicting data currently present in the literature on transfer factors. This is 

particularly true for conditions like those to be encountered at present and future nuclear 

waste storage/processing facilities where material may enter the groundwater and 

subsequently be present in irrigation water to human crop plants.

Three geographical regions were chosen for study; these regions have had, or currently 

have, operating commercial nuclear waste disposal sites. The three sites selected are in 

South Carolina near the Barnwell facility, in eastern Washington state near the LLW 

disposal facility located on the Hanford Site, and in southern Nevada near the closed 

Beatty disposal facility. South Carolina depends primarily on rainfall to directly recharge 

soil moisture and the shallow aquifers. In eastern Washington, the primary source of 

water to crop plants is through irrigation from aerial sprayers - the water being derived 

from large rivers. In southern Nevada, water is also supplied through irrigation both 

aerial and also delivered as flood irrigation directly to the surface of the soil, with the 

water coming from large underground aquifers accumulated over thousands of years. 

The soil to plant pathway for transfer of radionuclides is dependent on a number of 

factors. These may include: 

a) the chemical nature and reactivity of the isotope as it may affect the availability of 

the isotope within the soil pore water within the rhizosphere of the plant root;

b) the route of exposure (e.g. root versus foliar exposure);

c) the plant species itself (physical stature, root-shoot ratio); and,

d) the nutrient requirements of the plant (chemical similarity of the isotope to a 

nutrient). 

The efforts reported in this document address the uptake and distribution of neptunium237 (237Np) and iodine-125 (125I) in three differing soil types and various crop types. In 

all instances, the label was surface applied to the soil as irrigation water and allowed to 

be flushed down into the soil profile to the plant roots.
4-2

4.1 Materials and Methods

4.1.1 Soils

The effort was to accurately determine realistic transfer factors of selected isotopes 

(neptunium, iodine) from soils selected from differing regions of the United States to 

crop plants (e.g. alfalfa, corn, and potatoes). The soils were amended through surface 

irrigation to reflect the potential contamination of groundwater aquifers. The basic 

properties of the soil type used are given in Table 4.1 (CEC is cation exchange capacity, 

OM is organic matter).

Three soils were employed during the study: 

• Hanford Sandy Loam Soil – Hanford Site 200-Area, WA

• Nevada Nye County Sandy Clay Soil – Amargosa, NV

• South Carolina Field Soil – Clemson University Research Station at Blackville, 

South Carolina (approximately 15 km [10 mi.] north-east of Barnwell, SC)

Table 4.1. Summarized Soil Properties

Soil Type pH CEC %OM %Sand %Silt/Clay

Hanford 7.48 37 0.27 83 17

Nevada 8.07 28 0.12 99 1

Savannah River 

Field Soil 4.87 25.7 0.38 97.5 2.5

All soils were received from the various sites in sealed 19 L (5-gallon) plastic buckets. 

The Washington State Hanford soil and the Nevada Nye County soil were: 1) air dried in 

the green house in soil bins for at least 7 days with frequent turnover; 2) sieved through 

2 mm standard soil sieves (No. 10) and stored in sealed plastic lined cans at room 

temperature until used. The soil from South Carolina now falls under the Post-9/11 

Restricted Shipping Regulations of USDA-APHIS because of the potential for fire-ant 

contamination. Following a lengthy approval period by APHIS the Savannah River soils 

were therefore processed as described in Section 2.1.3. It is not believed that the 

different soil treatment of the South Carolina soil (temperatures of 80°C and -5°C used to 

kill any living organisms that might be in the soil) had any impact on the experiments. 

Similar treatment in previous experiments (Napier, Fellows, and Krupka 2007) had no 

effect on uptake.

Prior to use in the experiment all soils were tested for soil water holding capacity and 

percent moisture remaining in air dried/sieved soil.
4-3

4.1.2 Contaminants 

In separate sets of experiments, the labels used were of 237Np in 1 N HNO3 and 125I in 

0.1 N NaOH. Contaminants were added to the surface of each pot of soil as either a 

dilute solution of HNO3 for the Np-237, or a dilute solution of NaOH for the I-125. 

Safety restrictions placed by PNNL Radiation Protection Services determined that given 

the potentially dispersible nature of the isotope on soil particles, the benchtop (growth 

chamber) limit would be a total of eight microcuries (8 μCi or 0.296 MBq) for 237Np and 

100 μCi (3.7 MBq) for 125I. In both experiments the isotope was kept in a non- or 

minimally-dispersible form (liquid) at all times. 

4.1.3 Plant Material

The root-soil studies employed a forage crop, alfalfa (Medicago sativa); a root or tuber 

crop, potato (Solanum tuberosum); and a grain and forage crop, corn (Zea mays), as 

representative agricultural species. Alfalfa and corn are grown in Washington, Nevada, 

and South Carolina for forage and grain, while potatoes are also grown in all three states 

as a row crop and in gardens. 

4.1.3.1 Growth Conditions

All seed were obtained locally (Columbia Basin Feed and Grain, Pasco, WA). To 

prevent root binding that might stunt plant growth, all species were grown in 1-gallon 

pots each containing 3 kg of soil. The number of plants in each pot varied: Alfalfa –

4 plants/pot; Potato - 2 plants/pot; and Corn - 3 plants/pot. Those derived from seed 

(alfalfa and corn) were seeded at a minimum of 10/pot and later thinned to the number 

above. The plants were grown for a minimum of 45 to 60 days, or until flowering and 

seed set or tuber development. 

Plants were grown in growth chamber where conditions included a light intensity of 

~400 μEinsteins/m2

/sec at soil level from a combination of fluorescent and incandescent 

lamps, a 12/12 h light/dark cycle with a 18°C night and 27°C day temperature and 80% 

relative humidity. 

The soils in the pots were maintained at ~60% to 80% field capacity (-2 bars or -20 Mpa) 

as measured by a soil moisture meter and sensors (Cole-Parmer Co., Vernon Hills, 

Illinois) placed 1/3 of the distance from the top to bottom of the soil column. The plants 

were watered with DI water as needed and once weekly with a 1/10th strength Hoagland’s 

solution if nutrient stress became evident. The upper surface of the soil was covered 

(5mm-deep) with black polyethylene beads to minimize water transpiration from the soil 

surface and prevent splashing when watering and amending with label as shown 

Figure 4.1. Moisture sensors were monitored every other day. 

We were required to keep the growth chamber doors closed except for labeling and 

harvesting. To accomplish this, the leads from the water sensors were threaded through a 

small hole in the side of the chamber which was sealed around the wires as shown in 
4-4

Figure 4.2 so that the water status of each pot could be monitored from outside. Water, 

or fertilizer if required, was supplied through irrigation tubing from outside the chamber 

as well. Air-flow out of the chamber was modified to maintain a negative pressure within 

the chamber. Air ports were covered with certified HEPA filters. 

Figure 4.1. Component Arrangement for Soil Pots Employed in Soil-Plant Experiments

Figure 4.2. Plant and Pot Arrangement in Growth Chamber in Soil-Plant Experiments

(numbers in circles indicate replicates for each soil type)
4-5

4.1.3.2 Plant Harvest and Isotope Analysis

When the plants were mature, water was withheld for three days to dry out the soil prior 

to harvest. The plants were then transferred to the hood and the soil loosened around the 

plant. The tissue samples (stem, leaves, fruit/seed, tubers) were removed from the plants, 

placed in tared glass containers and a fresh weight taken. All samples were then placed 

in an 80°C forced air oven for 24- to 48-h to dry. The containers were allowed to cool in 

a dessicator and a dry weight taken. The dried samples were then ground with a Wiley 

Mill (Sargent Welch, Inc. Philadelphia, Pennsylvania) to a 20 mesh size. The samples 

were then stored at room temperature.

Np-237 Plants. For isotope analysis, three 0.5g samples of each tissue (or less depending 

on availability) were transferred to pre-weighed and labeled 15-mL scintillation vials. 

The vials were marked and the tissues wet digested. Briefly, the dried tissues were 

wetted with 1.0-mL of 6 N HNO3 and the tops of the vials covered with watch glasses. 

The vials were then placed in a muffle furnace at 200°C for 2-h, then at 450°C for 20-h. 

The ashed samples were then cooled, wetted again with 1.0-mL of 6 N HNO3, and 

re-muffled at 450°C for 20-h. The samples were then cooled and suspended in 1.0-mL of 

0.01 N HNO3. Fifteen ml of liquid scintillation cocktail (Ready-Safe®, Beckman-Coulter 

Instruments, Fullerton, California) was then added to the vial and the activity (dpm) 

determined by liquid scintillation analysis using a Beckman 6500 Liquid Scintillation 

Spectrometer (Beckman-Coulter Instruments, Fullerton, California) with previously 

constructed quench curves. 

I-125 Plants. Plant tissue from the 125I experiment was processed in the same fashion as 

the Np tissue with the exceptions that the dried/ground tissue was wetted with 1.0-mL of 

3 N NH4OH prior to placement into the muffle furnace, and the ashed samples were 

wetted with 1.0-mL of 0.01 N NH4OH prior to the addition of scintillation cocktail. 

Activity was determined using experiment specific quench curves and decay correction 

for the 125I. The base NH4OH was used in the extraction to minimize the potential for 

volatilization. At the beginning of the analysis process, checks were run with control 

samples (plant tissue) with 125I pipetted on top and allowed to dry prior to putting them 

into the furnace. Losses were less than 5-10 % at most.

4.1.4 Soils Isotope Analysis

Following harvest of the plant tissue a series of samples were taken from the soil 

remaining in the pots. Ten samples of approximately 1 g each were randomly sampled 

from both 3- and 8-cm below the plastic beads. The samples were composited into a 

15-mL scintillation vial and mixed to randomize the material. The samples were then 

dried for 48 hr at 80°C in a forced air oven. 

Samples of 1g each from each pot were placed in 15-cm long (1-cm diam.) disposable 

liquid chromatography columns (Bio-Rad, Hercules, California) with sintered glass 

bases. Ten milliliters of soil specific ground water (Hanford for the Hanford soil, Nevada 

for the Nevada soil, and South Carolina for the South Carolina soil) were added to each 
4-6

column, the columns capped and inverted three times to mix the soil and groundwater, 

and allowed to sit for 1 hr. At that time the column stopcock was opened and the liquid 

allowed to flow into a clean scintillation vial. Following this 10-mL of 8 N HNO3 was 

added to the columns and the actions repeated following a 1 hr equilibration time. One 

milliliter of the extracts was then transferred to a new vial and 15-mL of scintillation 

cocktail added. The vials were then counted and analyzed as described above.

4.2 Experimental Results for 237Np

The soil-plant experiments sought to demonstrate variations in uptake derived from both 

the type of soil that the plant is growing in (contaminant availability and chemical species 

present in the soil pore water), and secondly, the plant species itself (root anatomy and 

distribution within the contaminant soil profile).

Neptunium is an anthropomorphic byproduct of plutonium production activities and 

results from the capture of neutrons by uranium isotopes. It is present in the environment 

only at those locations where nuclear fissile material has been released through accidents, 

production discharges of waste, detonation of weapons, or fallout from testing. 

Neptunium-237 (237Np) has a half-life of over 2 million years and it forms various 

complexes with inorganic and organic ligands when incorporated in soil (Koch-Steindl 

and Prohl 2001). 

The availability of these ligands to the roots of terrestrial plants growing in these soils is a 

function of soil composition, Np-237 oxidative state (pH and Eh), and Np concentration 

(Cataldo, Garland, and Wildung 1988). In order to characterize variations between soil 

types and plant species in the plant uptake experiments, we therefore took care to ensure 

that the 237Np was similar for all soil types and plant species. This is shown in Tables 4.2 

and 4.3 where the label was applied as a uniform solution which, when the amendments 

were completed, provided a similar final concentration of radionuclide and metal in each 

pot. The label was applied to the soil as an injection uniformly distributed over the 

surface and about 1-2 cm deep to mimic surface irrigation with contaminated water. The 

total amount per pot was restricted under our operating protocols but fell within the 

ranges previously used by Cataldo, Garland, and Wildung (1988) for bush bean 

(Phaeseolus vulgaris) and soybean (Glycine max).

Table 4.2. Attributes of the Np-237 Employed in the Soil-Plant Uptake Experiments

Attributes Neptunium 

Chemical Form Neptunium Nitrate

Solvent 2.0 N HNO3

Sp. Activity 0.000705 mCi/mg

Final Activity/Pot 0.294 μCi

Activity/50 mL Aliquot 0.0735 μCi

Aliquot Chemical Composition 0.01 N HNO3,

pH=~4.0
4-7

Table 4.3. Specific Activity and Calculated Weights of 237Np in the Three Differing Soil 

Type Pots Used in the Soil-Plant Uptake Experiments

Soil Type Weight/Pot 

(g)

Total 237Np 

Activity in 

Each Pot

237Np Specific 

Activity

(pCi/g Soil)

237Np 

Concentration

(ng/g Soil)

Hanford 3060 0.294 μCi 96.71 13.72

Nevada 3075 0.294 μCi 96.26 13.65

South Carolina 3003 0.294 μCi 98.56 13.97

4.2.1 Dry Matter Production

Plants were grown and harvested as in previous studies (see Figures 4.3 and 4.4). As is 

readily evident in Table 4.4, the Nevada soil was the least fertile of the three soil types 

and in all three plant species provided the poorest yield, or dry matter production. It was 

also the poorest in corn kernel and potato tuber production (Tables 4.5 and 4.6). The 

Hanford soil produced the greatest yield in alfalfa and potato tubers, crops normally 

grown in this region, while the South Carolina field soil, soil taken from an active corn 

field, gave comparable amounts to the Hanford soil which once again had the highest 

corn dry weight production (Table 4.5).

Figure 4.3. Harvest of 237Np Alfalfa Plants Grown in South Carolina Soil
4-8

Figure 4.4. Corn Seed Harvested from Plants Grown in South Carolina Soil a for 237Np 

Experiment

Table 4.4. Total Plant Dry Weight Per Pot for 237Np Experiment. Average dry weight 

(g) ± SD (N=3).

Soil Type Alfalfa Corn Potatoes

Avg. Plant Dry Wt (g)/Pot ± SD (N=3)

Hanford 17.07 ± 2.26 47.55 ± 1.69 22.95 ± 2.86

Nevada 3.85 ± 1.33 17.31 ± 6.66 8.22 ± 7.38

South Carolina 5.30 ± 3.51 45.55 ± 3.72 15.56 ± 1.09

Table 4.5. Dry Weight of Corn Leaves, Stems, Cob, and Seed for 237Np Experiment.

Average dry weight (g) ± SD (N=3).

Soil Type Leaves Stem Cob Seed

Avg. Plant Dry Wt (g)/Pot ± SD (N=3)

Hanford 12.65 ± 2.03 7.85 ± 3.03 4.33 ± 0.98 22.73 ± 6.84

Nevada 7.21 ± 1.18 5.71 ± 1.85 1.24 ± 1.18 3.16 ± 2.85

South Carolina 9.23 ± 1.07 3.73 ± 0.46 4.26 ± 0.89 28.33 ± 4.08
4-9

Table 4.6. Dry Weight of Potato Leaves and Potatoes (skin and tuber) for 237Np 

Experiment. Average dry weight (g) ± SD (N=3).

Soil Type Shoot 

(Leaves and Stem)

Potato 

(Tuber + Skin

Avg. Plant Dry Wt (g)/Pot ± SD (N=3)

Hanford 2.93 ± 0.76 20.01 ± 2.14

Nevada 1.94 ± 0.56 10.40 ± 2.20

South Carolina 3.57 ± 1.14 11.98 ± 1.62

4.2.2 Neptunium-237 Uptake, Distribution, and Concentration

The results of plant sample analyses giving the specific activities (pCi of 237Np/g Dry Wt. 

Tissue) for each species and soil type are given in Tables 4.7 (alfalfa), 4.8 (corn), and 4.9 

(potato). For all three species, those plants grown in the South Carolina soil contained 

the highest specific activity - in most cases four to six times the amount of the other soil 

plants. This was primarily evident in the shoot (leaves and stem) portions of the plants. 

In the case of corn and potato, the South Carolina plant shoots contained almost eight to 

ten times the specific activity of that found in the shoots of the other two soil types. The 

activity found in the ear (cob and seed) of the corn as well as the whole potato (tuber and 

skin) was also higher in the South Carolina soil plants but only about twice as much 

(Tables 4.8 and 4.9). 

There is no apparent correlation between the tissue specific activity and the plant dry 

weight (see above, Tables 4.4, 4.5, and 4.6) as the alfalfa and potatoes grown in the 

Hanford soil showed the highest dry weight gain but there was no statistical difference 

evident in the corn shoot dry weight comparison between the Hanford or South Carolina 

soil grown plants. This suggests that the differences in the soil types may not have been 

significant as far as availability of common plant nutrients, but that the 237Np was present 

in higher concentrations in the soil pore water next to the roots from which minerals are 

selected for plant absorption in the sandy South Carolina soil (Hursthouse et al. 1991). 

Table 4.7. Neptunium-237 Specific Activity (pCi/g dry wt. tissue) of Alfalfa Shoots 

Grown from Seed in Differing Soil Types for a Minimum of 60 Days

Soil Type Alfalfa Shoot 

Avg. 237Np pCi/g 

Dry Wt ± SD (N=3)

Hanford 72 ± 32

Nevada 53 ± 12

South Carolina 214 ± 65
4-10

Table 4.8. Neptunium-237 Specific Activity (pCi/g dry wt. tissue) of Corn Leaves, 

Stem, Cobs, and Kernels from Plants Grown from Seed in Differing Soil 

Types for a Minimum of 60 Days

Soil Type Leaves Stem Cob Kernels Whole Plant

Avg. 237Np pCi/g Dry Wt ± SD (N=3)

Hanford 27 ± 4 29 ± 10 17 ± 1 5 ± 2 78 ± 14

Nevada 25 ± 4 13 ± 2 17 ± 5 13 ± 8 64 ± 15

South 

Carolina

201 ± 50 179 ± 55 35 ± 4 3 ± 1 418 ± 108

Table 4.9. Neptunium-237 Specific Activity (pCi/g dry wt. tissue) of Potato Shoots, 

Tubers, and Tuber Skins Grown from Cuttings in Differing Soil Types for a 

Minimum of 60 Days. Skin was removed from tubers and counted separately 

to minimize soil contamination of the tuber tissue.

Soil Type Potato Shoot Potato Tuber Potato Skin Whole Plant

Avg. 237Np pCi/g Dry Wt ± SD (N=3)

Hanford 64 ± 3 12 ± 1 112 ± 46 188 ± 48

Nevada 75 ± 17 11 ± 1 65 ± 30 150 ± 48

South Carolina 673 ± 492 21 ± 3 119 ± 27 813 ± 480

For this experiment the entire above-ground portion of the alfalfa plants (leaves and 

stem) were combined, because this is the portion used as forage for animal feed. In this 

case, the transfer percentage was therefore 100% for the alfalfa grown in all three soil 

types as shown in Table 4.10. The average total activity recovered (pCi) per pot is also 

shown in the Table and this indicates that the 237Np was apparently more available for 

alfalfa uptake in the Hanford and South Carolina soils than in the Nevada soil. Higher 

accumulations were also evident in the South Carolina soil-grown plants than the other 

two for both the corn (Table 4.11) and potato (Table 4.12). These are results differ from 

expectations based on a strictly dry weight basis (see Tables above) and may reflect the 

label distribution within the pots or the root anatomy (Esau 1965), or both. Alfalfa has a 

fibrous root system that would penetrate mainly in the top 15 cm of the soil. Corn has 

more of a main tap-root from which branches radiate outward and therefore quickly went 

to the bottom of the pots and spread out from there. Potato is less fibrous but tends to 

remain in the upper 10 cm of the soil profile. Further, the tubers themselves function in 

absorption of minerals from the soil pore water. As stated several times before, soil type 

and plant species are significant variables to a uniform concept of Np uptake by plants. 

Distribution patterns of 237Np in the corn and potato plants growing in the three soil types 

varied only slightly. In all three, most of the label was found in the leaves of the plant 

followed by the stem. This pattern would normally occur where the transpiration water 

coming out of the roots would reach termination at the minor veins of the leaf or the 

storage parenchyma of the stem. The corn seeds undergo minimal transpiration during 
4-11

grain fill and so receive very little xylem flow. Most of the label in corn seeds would 

most likely have come through redistribution and phloem transport (Marschner 1995). 

Table 4.10. Percent Distribution of Recovered Above Ground 237Np in Alfalfa Shoots 

for Different Soils and Total pCi Recovered in Plants

Soil Type Alfalfa Shoot Tot Plant pCi/Soil

Avg. ±Sd (N=3)

Hanford 100 1177 ±505

Nevada 100 250 ± 95

South Carolina 100 1318 ± 1310

Table 4.11. Percent Distribution of Recovered Above Ground 237Np in Corn Shoots for 

Different Soils

Soil Type Leaves Stem Cob Kernels

Tot Plant 

pCi/Soil

Avg. ±Sd 

(N=3)

Hanford 46.1 ± 1.5 29.20 ± 3.9 10.4 ± 2.5 14.3 ± 6.6 726 ± 27

Nevada 61.1 ± 8.7 25.0 ± 4.7 7.3 ± 3.3 9.9 ± 4.9 291 ± 30

South Carolina 67.1 ± 11.6 24.1 ± 5.3 5.6 ± 1.9 3.2 ± 0.6 2714 ± 487

The wide variation seen in the South Carolina potato plants (Table 4.12) was apparently 

caused by a labeling problem in that only one pot had exceptionally high amounts in the 

plant material. The amendment procedure, although attempting to be random, may have 

injected the label within the center of the developing plant’s root ball and not near the 

growing tubers, thus promoting a higher uptake through mass action to the shoot.

Table 4.12. Percent Distribution of Recovered 237Np in Potatoes for Different Soils

Soil Type Potato Shoot Potato Tuber Potato Skin

Tot Plant 

pCi/Soil

Avg. ±Sd 

(N=3)

Hanford 23.5 ± 6.9 23.8 ± 1.5 52.6 ± 15.2 803 ± 78

Nevada 33.9 ± 2.1 18.4 ±1.9 47.7 ± 7.6 414 ± 15

South Carolina 80.8 ± 59.5 5.7 ± 0.6 13.5 ± 3.6 3101 ± 1753
4-12

4.2.3 Neptunium-237 Concentration Ratios

All of the soils were amended with the same solution, volume of injection, injection 

depth into the soil profile (1 to 2 cm), and at the same time during the growth period. 

Each time the plants were watered, sufficient liquid was added to cover the entire surface 

of the pot and this was allowed to soak into the soil. 

When the above-ground potions of the plants were harvested, soil samples were also 

collected. Samples were taken from areas inside of the irrigation tubing ring (see 

Materials and Methods) and from depths of 2 cm to 15 cm below the plastic beads. The 

material was pooled, thoroughly mixed, and subsampled (1 g) at least three times. The

subsamples were extracted with groundwater, groundwater with CaCl2 added (0.01 M), 

and 6 N HNO3, and the resulting counts summed for total available label to the roots. 

The actual amount of 237Np added to the pot was also calculated from specific activity 

and counting aliquots of the labeling solution. This activity was then matched with the 

average whole plant specific activity (pCi/g dry wt. of tissue) of the plant for each pot 

(Tables 4.7, 4.8, and 4.9). From these the Concentration Ratio (CR, [(pCi/g dry wt. 

tissue)/(pCi/g dry wt. soil)]) for each plant species and soil type was calculated. The 

comparative results are given in Tables 4.13, 4.14, and 4.15.

Table 4.13. Neptunium-237 Concentration Ratios [(pCi/g dry wt. tissue)/(avg. pCi/g dry 

wt. soil)] for Alfalfa Shoots Grown from Seed in Differing Soil Types for a 

Minimum of 60 Days. Soil specific activity was calculated both from actual 

amount of amended Np-237 (“Amended”) and from extracted (“Extracted”) 

soil samples taken from the pot at harvest.

Soil Type

“Amended”

Alfalfa Soil 

Specific Activity

(pCi/g Dry wt.)

“Amended”

Alfalfa Shoot 

CR1

“Extracted”

Soil Specific 

Activity

(pCi/g Dry wt.)

Avg. ± SD 

(n=3)

“Extracted”

Alfalfa Shoot 

CR1

Hanford 96 0.7419 ± 0.4048 45 ± 43 1.5993 ± 0.8725

Nevada 97 0.5540 ± 0.1565 126 ± 43 0.4221 ± 0.1192

South Carolina 

Field

99 2.1641 ± 0.8069 58 ± 62 3.7586 ± 1.4015

1. [(Avg pCi. 237Np /g Dry Wt. Plant)/(Avg pCi/g Dry wt. Soil)] ± SD (N=3)

It is very obvious looking at the large standard deviations for the extracted soil samples 

for all soils and plant species that there was no significant uniformity to the distribution 

of the 237Np within the soil profile. As stated above, it was anticipated that the “flooding”

of the surface of the pots would present a uniform saturation front of water passing into 

the soil profile. Apparently the label did not distribute evenly within the pots but 

remained in a pattern of “hot spots.” This is reflected in the variations between the two 

calculated concentration ratios. Schreckhise and Cline (1980) and Hursthouse et al. 
4-13

(1991) have reported that while 237Np will distribute within a soil profile at much faster 

rates than 239-240Pu, their time periods were expressed in years and not months. Perhaps 

future experiments could use a technique to uniformly saturate the surface of the soil 

prior to planting to obviate this problem, although channelization of the water into the 

soil is inevitable in most conditions even in the field.

However, even within the variances of soil sampling, it was evident that for all three 

species there was a greater uptake from the South Carolina soil than the others while the 

least was always noted in the Nevada plants. Based on the specific activity of the Np 

(Table 4.1), the actual concentration of Np added in each pot was 1.37- to 1.39 × 10-8 g 

Np/g dry wt. of soil (~42 ng/pot). While the literature values of concentration ratio for 

237Np vary widely (Romney et al. 1981; Sheppard et al. 2006), those seen in this 

experiment do fall within the observed range. Further, based on the Np concentration 

within each of the soil types, the concentration ratios for the South Carolina soils fall 

directly in line with those reported for bushbean grown in Ritzville silt loam by Cataldo, 

Garland, and Wildung (1989).

Because natural conditions are likely to be closer to the results from the experiment than 

homogeneous averaging, the “extracted” values are recommended for modeling use.

Table 4.14. Neptunium-237 Concentration Ratios [(pCi/g dry wt. tissue)/(avg. pCi/g dry 

wt. soil)] for Corn Shoots Grown from Seed in Differing Soil Types for a 

Minimum of 60 Days. Soil-specific activity was calculated both from 

actual amount of amended Np-237 (“Amended”) and from extracted 

(“Extracted”) soil samples taken from the pot at harvest.

Soil Type

“Amended”

Corn SoilSpecific Activity

(pCi/g Dry wt.)

“Amended”

Corn Whole 

Plant CR1

“Extracted” SoilSpecific Activity

(pCi/g Dry wt.)

Avg. ± SD (n=3)

“Extracted”

Corn Shoot CR1

Hanford 96 0.8084 ± 0.1426 134 ± 115.9 0.7920 ± 0.1856

Nevada 97 0.6642 ± 0.1520 80.8 ± 39 0.5828 ± 0.1046

South 

Carolina Field

99 4.2383 ± 1.0978 73 ± 45 5.7079 ± 1.4748

1 [(Avg pCi. 237Np /g Dry Wt. Plant)/(Avg pCi/g Dry wt. Soil)] ± SD (N=3)
4-14

Table 4.15. Neptunium-237 Concentration Ratios [(pCi/g dry wt. tissue)/(avg. pCi/g dry 

wt. soil)] for Potato Shoots Grown from Seed in Differing Soil Types for a 

Minimum of 60 Days. Soil-specific activity was calculated both from 

actual amount of amended 237Np (“Amended”) and from extracted 

(“Extracted”) soil samples taken from the pot at harvest.

Soil Type

Amended 

Potato SoilSpecific Activity

(pCi/g Dry wt.)

Amended 

Potato Whole 

Plant CR1

CaCl2 Extracted 

Soil-Specific 

Activity

(pCi/g Dry wt.)

Avg. ± SD (n=3)

Extracted 

Potato Shoot 

CR1

Hanford 96 1.9458 ± 0.4433 77 ± 57 2.4329 ± 0.7549

Nevada 97 1.5630 ± 0.4942 172 ± 149 0.8709 ± 0.2787

South 

Carolina Field

99 8.2522 ± 4.8656 78 ± 33 10.4529 ± 6.1714

1 [(Avg pCi. 237Np /g Dry Wt. Plant)/(Avg pCi/g Dry wt. Soil)] ± SD (N=3)

4.3 Experimental Results for Iodine-125

Iodine-125 is a reactor produced isotope through electron capture decay by Xe-125m. It 

has a relatively short half-life of 59.4 days. It is used in these experiments as a surrogate 

for longer-lived iodine isotopes such as 129I. The data presented below are all corrected 

for decay to time zero, the first application of the 125I solution to the soil pots. To reduce

the potential for volatility of the 125I from the soil surface the amended material was kept 

at room temperature and was alkaline in pH. An alkaline pH was also maintained during 

the tissue and soil processing and analysis. Other attributes of the label are presented in 

Tables 4.16 and 4.17

Table 4.16. Attributes of the 125I Employed in the Soil-Plant Uptake Experiments

Attributes Iodine 

Chemical Form Sodium Iodide

Solvent 1.0 N NaOH

Final Activity/Pot 2.277 μCi

Aliquot Chemical Composition 0.1 N NaOH

pH=~9.0
4-15

Table 4.17. Specific Activity and Calculated Weights of 125I in the Three Differing 

Soil Type Pots Used in the Soil-Plant Uptake Experiments. Activity was 

corrected for decay back to the time-zero soil application.

Soil Type Weight/Pot 

(g)

Total 125I 

Activity in 

Each Pot

125I Specific 

Activity

(pCi/g Soil)

Hanford 3060 2.277 μCi 744

Nevada 3075 2.277 μCi 740

South Carolina 3003 2.277 μCi 758

4.3.1 Dry Matter Production

The Hanford soil produced the greatest yield in alfalfa, corn, and potato tubers, crops 

normally grown in this region (Table 4.18). As is readily evident in Table 4.18, the 

Nevada soil was again the least fertile of the three soil types and in all three plant species 

provided the poorest yield, or dry matter production. It was also the poorest in corn 

kernel production, and, although we replanted the seed potatoes twice, the plants failed to 

grow and ultimately rotted in the pots (Tables 4.19 and 4.20). The experiment was begun 

in the winter months (November-December) and the latest crop of seed potatoes was not 

available at this time. We therefore had to employ previously stored older tubers. These 

were not as viable as a new tuber would have been.

Table 4.18. Total Plant Dry Weight Per Pot for 125I Experiment. Average dry weight 

(g) ± SD (N=3).

Soil Type Alfalfa Corn Potatoes

Avg. Plant Dry Wt (g)/Pot ± SD (N=3)

Hanford 6.34 ± 1.55 14.82 ± 4.67 8.55 ± 0.77

Nevada 1.73 ± 1.03 7.52 ± 6.15 0.0 ± 0.01

South Carolina 2.68 ± 1.45 11.10 ± 3.32 7.54 ± 6.00

1.Nevada soil potatoes failed to grow

Table 4.19. Dry Weight of Corn Leaves, Stems, and Ear (cob and seed) for 125I 

Experiment. Average dry weight (g) ± SD (N=3).

Soil Type Leaves Stem Cob

Avg. Plant Dry Wt (g)/Pot ± SD (N=3)

Hanford 8.72 ± 1.88 5.12 ± 2.43 0.98 ± 0.45

Nevada 4.23 ± 3.11 3.02 ±2.80 0.26 ±0.30

South Carolina 7.36 ±1.71 2.94 ±1.22 0.71 ± 0.48
4-16

Table 4.20. Dry Weight of Potato Leaves and Potatoes (skin and tuber) for 125I 

Experiment. Average dry weight (g) ± SD (N=3).

Soil Type Shoot

(Leaves and Stem)

Potato

(Tuber + Skin)

Avg. Plant Dry Wt (g)/Pot ± SD (N=3)

Hanford 3.16 ± 0.21 4.72 ± 1.75

Nevada 0.00 ± 0.001 0.00 ± 0.001

South Carolina 2.36 ± 1.54 5.19 ± 4.53

1.Nevada soil potatoes failed to grow

During the growth period, we noted some discrepancies between the soil moisture 

readings and the appearances of the plants. On several occasions, the plants were 

showing water stress but the readings were indicating 90 to 95% soil saturation. It was 

possible that the sensors were not functioning properly but as replacing/repairing the 

sensors would have required uprooting the plants we decided to let them remain in place 

and watered instead on a set schedule.

Harvest times for the plants were set for the time at which the plants were to reach 

physiological maturity, a period where theoretically uptake from the soil would cease. 

For the potatoes and alfalfa this was usually extended because both crops will continue to 

grow into the first frost of the year. The corn has a more defined growth period when the 

ear matures followed by the senescence of the leaves and stalk. In the iodine experiment 

the corn reached maturity about 5- to 6-weeks prior to when it was harvested and 

remained in the chamber until the budgetary problems were overcome. It is possible that 

some of the dry weight present in all three species was lost to respiration or to decay 

during this time. As decay would have affected the carbon content of the tissues first this 

would also have affected the ratio between the carbon and the minerals also affecting the 

specific activity of the 125I.

Iodine has been recognized as a micronutrient in plants (Borst Pauwels 1961) and is 

readily accumulated by marine kelp. Hydroponic studies indicate concentration ratios of 

14 to 20 for spinach (Zhu et al. 2003) when the iodine is in the iodide form. There was a 

limit of 100 μCi for a bench top experiment at PNNL when the material is in a semidispersible form, therefore we used a total activity of 2.277 μCi/pot – a total of 62 μCi 

for the experiment. 

Iodine toxicity in solution culture of rice was reported at concentrations of 10 and 

100 μM as I, or 1.27 × 10-3 g/L and 1.27 × 10-2 g/L respectively (Mackowiak and Grossi, 

1999). They also reported that the Iodine concentration was higher in those plants whose 

dry matter accumulation was adversely affected.

The specific activity of the 125I used in the experiment was 629 GBq/mg or ~17Ci/mg. 

This means that 1.0 μCi would contain 5.84 × 10-11 g of I. Therefore the 2.277 μCi of 

I-125 that was added to each pot would give a total of ~13.3 × 10-10 g of I. This was 
4-17

injected into the top 3-cm of a 15-cm column of soil and allowed to penetrate into the soil 

column with subsequent watering. Each pot contained 3000 g dry weight of soil and 

while the actual soil pore water I concentration could not be determined throughout the 

soil profile, the potential for possible I toxicity to the plants is believed to be minimal. 

Further, the carrying solution (10 mL of 0.01 M NaOH) would do little to change the soil 

pH in the entire pot and so this might be discounted as a potential contributor to the 

reduced growth.

4.3.2 Iodine-125 Uptake, Distribution, and Concentration

Uptake was much greater than that seen for the 237Np as seen in Tables 4.21, 4.22, and 

4.23. The South Carolina soil-grown corn and potatoes exhibited a higher uptake than 

the plants grown in the other soils but the variations between pots make the results 

questionable for the potatoes. As is evident for the alfalfa (Table 4.21 vs. Table 4.18), for 

the South Carolina soil there was no direct correlation between plant dry weight and 

tissue-specific activity. Again, we were unable to get the potatoes to grow in the Nevada 

soil. 

Ashworth and Shaw (2006) reported that radioiodine (125I) accumulated in soil columns 

at the boundary between the anoxic and oxic boundaries because of its redox-dependent 

sorption behavior.

The percentage of label partitioning within the plants placed most of the 125I in the stem 

and leaves of the corn and potatoes (Tables 4.25 and 4.26). The plant growth in general 

was less than we have seen previously and this may have been related to the necessary 

use of older seed (the experiment was started in November). There was very poor 

reproductive development in all plants but particularly in those growing in the Nevada 

soil. The higher percentage observed in the South Carolina soil potatoes was an anomaly 

with one plant exhibiting activity at 10 times that of previous samples. This may have 

occurred during the labeling of the soil where a higher amount of the labeling solution 

during the second injections was injected too close to the developing plant’s root system. 

This would have a low probability as the injections were made away from the seedlings 

present.

Table 4.21. Iodine-125 Specific Activity (pCi/g dry wt. tissue) of Alfalfa Shoots Grown from 

Seed in Differing Soil Types for a Minimum of 60 Days

Soil Type Alfalfa Shoot 

Avg. 125I pCi/g Dry Wt ± 

SD (N=3)

Hanford 1157 ± 638

Nevada 1789 ± 533

South Carolina 5733 ± 395
4-18

Table 4.22. Iodine-125 Specific Activity (pCi/g dry wt. tissue) of Corn Leaves, Stems, 

and Ears (cobs and kernels) from Plants Grown from Seed in Differing Soil 

Types for a Minimum of 60 Days

Soil Type Leaves Stem Cob/Seed Whole Plant

Avg. 125Ip pCi/g Dry Wt ± SD (N=3)

Hanford 692 ± 82 158 ± 16 96 ± 37 473 ± 61

Nevada 1854 ± 219 341 ± 35 122 ± 103 847 ± 450

South 

Carolina

948 ± 272 56 ± 17 91 ± 36 659 ± 148

Table 4.23. Iodine-125 Specific Activity (pCi/g dry wt. tissue) of Potato Shoots, Tubers, 

and Tuber Skins Grown from Cuttings in Differing Soil Types for a 

Minimum of 60 Days. Skin was removed from tubers and counted 

separately to minimize soil contamination of the tuber tissue.

Soil Type Potato Shoot Potato Tuber Potato Skin Whole Plant

Avg. 125I pCi/g Dry Wt ± SD (N=3)

Hanford 1400 ± 340 170 ± 30 502 ± 217 697 ± 228

Nevada -

1 - - -

South Carolina 

Field

11295 ± 

97702

1140 ± 6292 7963 ± 81692 2502 ± 5252

1.No potatoes grew in the Nevada soil.

2. Variance. Only two pots had potatoes with wide differences in activity.

Table 4.24. Percent Distribution of Recovered Above-Ground 125I in Alfalfa Shoots for 

Different Soils

Soil Type Alfalfa Shoot 

Hanford 100

Nevada 100

South Carolina 100

Table 4.25. Percent Distribution of Recovered Above-Ground 125I in Corn Shoots for 

Different Soils

Soil Type Leaves Stem Cob

Hanford 87.4 ± 26.1 11.3 ± 4.5 1.3 ± 0.7

Nevada 88.1 ± 34.7 7.2 ± 2.3 0.6 ± 0.4

South Carolina 94.4 ± 44.0 2.4 ± 1.6 1.4 ± 0.7
4-19

Table 4.26. Percent Distribution of Recovered 125I in Potatoes for Different Soils

Soil Type Potato Shoot Potato Tuber Potato Skin

Hanford 76.3 ± 19.5 11.2 ± 1.8 12.5 ± 6.3

Nevada - - -

South Carolina 55.4 ± 47.9 5.6 ± 3.1 39.0 ± 40.0

4.3.3 Iodine-125 Concentration Ratios

As in the 237Np experiment, all of the soils were amended with the same solution, volume 

of injection, injection depth into the soil profile (1 to 2 cm), and at the same time during 

the growth period. Each time the plants were watered, sufficient liquid was added to 

cover the entire surface of the pot and this was allowed to soak into the soil. Once again 

the variations in soil sample activity were significant for the extracted soil versus the total 

activity applied to the pots. This variation promoted higher concentration ratio values 

from the extracted soils than those using just the amount provided to each pot. The 

highest concentration ratio values for alfalfa and corn were seen in the plants grown in 

the South Carolina soil for both types of soil activity calculation.

The analyses of the soil pore water anion concentrations given in Table 2.17 provide a 

potential explanation for the much higher CRs evident in the plants growing in the 

Clemson University (SCF) soil. The soil pore water concentration of NO3 in the SCF 

soil was five times higher than that of the Nevada soil and ten times higher than that of 

the Hanford soil. This is expected given the agricultural history of soil fertilization for 

this soil. This becomes important in light of recent publications that address the potential 

of enhancing the iodine concentration of crops (biofortification) for human health. 

Smolen et al. (2011) reported that enhanced levels of N fertilization (NO3 and NH4) 

promoted I uptake (particularly in the IO3 form) into the storage tissues of carrot roots. 

Low levels of I as IO3 in solution culture were reported to enhance N uptake (NO3 and 

NH4) and concomitantly I uptake in lettuce leaves by Biasco et al. (2010). The 

interaction between the soil pore water NO3 levels and I could have led to the higher 

I content within the tissues. This should be considered in future studies.
4-20

Table 4.27. Iodine-125 Concentration Ratios [(pCi/g dry wt. tissue)/(avg. pCi/g dry wt. 

soil)] for Alfalfa, Corn, and Potato Plants Grown from Seed in Nevada, 

Hanford, and South Carolina Soil Types for a Minimum of 60 Days. Soilspecific activity was calculated both from actual amount of amended 125I 

(“Amended”) and from extracted (“Extracted”) soil samples taken from the 

pot at harvest.

Soil 

Type Plant

Average 

Plant-Specific 

Activity

(pCi/g dry wt.) 

± S.D. n=3

Average Soil 

ExtractSpecific 

Activity

(pCi/g dry 

wt.) ± S.D. 

n=3

Soil 

Extract

CR1

Pot Soil 

Amended 

Specific 

Activity

(pCi/g dry 

wt

Pot Soil 

Amended

CR2

(Avg. ± SD. 

n=3)

Nevada Alfalfa 1789 ± 533 345 ± 15 5.18 ± 1.54 740 2.42 ± 0.72

Corn 847 ± 450 152 ± 5 5.57 ± 2.96 740 1.14 ± 0.61

Potato -

3 380 ± 19 -3 740 -3

Hanford Alfalfa 1157 ± 638 537 ± 5 2.15 ± 1.19 744 1.56 ± 0.86

Corn 473 ± 61 327 ± 11 1.45 ± 0.19 744 0.64 ± 0.08

Potato 697 ± 228 472 ± 9 1.48 ± 0.48 744 0.94 ± 0.31

S. C. Alfalfa 5753 ± 395 183 ± 5 31.41 ± 2.16 758 7.59 ± 0.52

Corn 659 ± 148 508 ± 30 1.29 ± 0.29 758 0.87 ± 0.20

Potato4 2502 ± 525 326 ± 10 7.68 ± 1.61 758 3.30 ± 0.69

1 [(Avg pCi. I-125 /g Dry Wt. Plant)/(Avg pCi I-125 /g Dry wt. Soil)] ± SD (N=3).

2 [(Avg pCi. I-125 /g Dry Wt. Plant)/(Avg Amended pCi I-125 /g Dry wt. Soil)]. 

3 No potatoes grew in the Nevada soil.

4 Skewed results from a single sample.
4-21

4.4 References 

Biasco B, JJ Rios, LM Cervilla, E Sanchez-Rodriguez, MM Rubio-Wilhelmi, 

MA Rosales, JM Ruiz, and L Romero. 2010. Photorespiration process and Nitrogen 

metabolism in lettuce plants (Latuca sativa L.): Induced changes in response to Iodine 

biofortification. J. Plant Growth Regulation 29(4):477–486.

Borst Pauwels, GWFH. 1961. Iodine as a micronutrient for plants. Plant and Soil

14(4):377–392.

Cataldo DA, TR Garland, and RE. Wildung. 1988. Absorption, distribution, and fate of 

Neptunium in plants. J. Agric. Food Chem. 36:657–662.

Esau K. 1965. Plant Anatomy. John Wiley & Sons, New York.

Hursthouse AS, MS Baxter, FR Livens, and HJ Duncan. 1991. Transfer of Sellafieldderived 237Np to and within the terrestrial environment. J. Environ. Radioact. 14:147–

174.

Koch-Steindl H and G Prohl. 2001. Considerations on the behavior of long-lived radio 

nuclides in the soil. Radiat. Environ. Biophys. 40(2):93–104.

Marschner H. 1995. Mineral nutrition of higher plants. 2nd ed. Academic Press, 

New York.

Napier BA, RJ Fellows, and KM Krupka. 2007. Soil-to-Plant Concentration Ratios for 

Assessing Food Chain Pathways in Biosphere Models. NUREG/CR-6941, U.S. Nuclear 

Regulatory Commission, Washington, D.C.

Robertson DE, DA Cataldo, BA Napier, KM Krupka, and LB Sasser. 2003. Literature 

Review and Assessment of Plant and Animal Transfer Factors Used in Performance 

Assessment Modeling. NUREG/CR-6825, U.S. Nuclear Regulatory Commission, 

Washington, D.C.

Romney EM, A Wallace, R Schulz, J Kinnear, and RA Wood. 1981. Plant uptakes of 

Np-237, Pu-239, Am-241, and Cm-244 from soils representing major food production 

areas of the United States. Soil Sci. 132:104–107.

Schreckhise RG and JF Cline. 1989. Comparative Uptake and Distribution of 

Plutonium, Americium, and Neptunium in Four Plant Species. Health Physics

38:817–824.

Sheppard SC, MI Sheppard, JC Tait, and BL Sanipelli. 2006. Revision and metaanalysis of selected biosphere parameter values for chlorine, iodine, neptunium, radium, 

radon and uranium. J. Environ. Radioact. 89:115–137.
4-22

Smolen S, W Sady, S Rozek, I Ledwozyw-Smolen, and P Strzetelski. 2011. Preliminary 

evaluation of the influence of Iodine and Nitrogen fertilization on the effectiveness of 

Iodine biofortification and mineral composition of carrot storage roots. J. Elementology

16(2):275–285.

Zhu Y-G, Y-Z Huang, Y Hu, and Y-X Liu. 2003. Iodine uptake by spinach (Spinacia 

oleracea L.) plants grown in solution culture: effects of iodine species and solution 

concentrations. Environ. Internat. 29(1):33–37.
5-1

5.0 Discussion

Because the uptake and behavior of radionuclides in plant roots, plant leaves, and animal 

products depends on the chemistry of the water and soil coming in contact with plants 

and animals, water and soil samples collected from these regions on the United States 

were used in experiments at Pacific Northwest National Laboratory to determine 

radionuclide soil-to-plant concentration ratios. Crops and forage used in the experiments 

were grown in the soils, and long-lived radionuclides introduced into the groundwater 

provide the contaminated water used to water the grown plants. Radionuclides under 

consideration included 237Np and 125I. Plant types included alfalfa, corn, and potato. The 

radionuclide uptake results from this research study are expected to show how regional 

variations in water quality and soil chemistry affect radionuclide uptake. 

Some summary observations are provided for the soil and groundwater analyses and the 

plant uptake studies. The results are compared with concentration ratio values currently 

common in the radiological assessment literature.

5.1 Soils and Groundwater Analyses

Physical and chemical characteristics are presented for three samples of soil and three 

associated groundwaters. These soil/groundwater combinations were used in 

radionuclide uptake studies within the U.S. Nuclear Regulatory Commission’s project 

Assessment of Food Chain Pathway Parameters in Biosphere Models. The differences in 

composition of the soils and waters from the three locations were expected to result in 

measurable differences in soil-to-plant transfer of the investigated radionuclides.

The groundwater samples showed some differences. The groundwater from Nevada was 

the most alkaline. The waters from both western sites, Nevada and Washington, had 

more carbonates than the eastern sample. The Nevada groundwater sample had 

somewhat lower nitrate concentrations than might be expected from the literature, but the 

sample location is at the edge of an agricultural area.

Differences are apparent in the soils from the three geographic locations. The major 

difference is prevalence of silica (quartz) sand in the South Carolina samples. Soils from 

this region were originally anticipated to be rich in organic materials, but both were lower 

in organic carbon and most other minerals than either of the western soil samples. All 

sites were low in organic carbon. The Hanford location soil has the highest 

concentrations of silt and clay, possibly because of the history of glacial flooding in the 

Hanford region. The Nevada soil was lowest in clay, although the South Carolina 

samples were only slightly higher. Differences were also noted in the soil pore water 

concentrations of dissolved minerals; these differences may be the most predictive in 

determining plant uptake.

Agricultural practices in the three locations also differ. Agriculture in the two western 

locations is dependent upon irrigation, although the sources of irrigation water in Nevada 

are essentially entirely derived from groundwater while the sources of irrigation water in 
5-2

southeastern Washington State are primarily derived from surface water, with 

groundwater only used in areas where surface water canals are not economically 

available. Irrigation is used to a much lesser extent in South Carolina, and only for 

supplementing rainfall for brief periods. The types of crops, their growing periods, and 

overall yields also differ among the three locations.

5.2 Speciation and Geochemistry

Computer modeling methods were used to calculate from equilibrium thermodynamic 

principals, the distributions of dominant aqueous species, and potential solubility controls 

for the environmentally important oxidation states of each of the selected radionuclides. 

The results of these speciation and solubility calculations for each radionuclide were 

graphically presented as a series of Eh-pH (or Pourbaix) diagrams. The Eh-pH diagrams 

were calculated at 25°C (298 K) and 1 atm pressure using the The Geochemist’s 

Workbench® (Version 8.0.8) software package and the expanded thermodynamic 

database file “thermo.com.V8.R6+.dat” provided with the software package. 

The results shown in Section 3 of this report are similar to those found by others. The 

single remarkable difference is the geochemical behavior of uranium predicted for the 

three soils evaluated. Recent discoveries and revisions to the understanding of uranium 

behavior have resulted in changes in this series of diagrams. These results occur because 

the three site groundwaters are all quite basic (high pH) and contain substantial amounts 

of dissolved calcium. As a result, the Ca2UO2(CO3)3

0 form is identified as being 

essentially completely dominant under essentially all Eh-pH conditions for these waters. 

This is a relatively soluble, and mobile, chemical form.

5.3 Soil-to-Plant Concentration Ratios for the Soils and Crops Studied

The various plants grew in generally the same manner in all three soil types, 

representative of regional variations in soils. In general, the shoot portions of the plants 

were reduced in mass in the Nevada Soil plants compared to the harvested shoots from 

the other soils.

Marked differences between plant species as well as soil types were evident in the 

amount of applied 237Np taken up by the plants. The soil types are indicative of regional 

variations in CR. The distribution patterns between the roots and shoots are similar for 

each species no matter which soil it was grown in. Higher activity in the South Carolina

field-grown plants was evident in plant/soil concentration ratios. The South Carolina 

crops had significantly higher concentration ratios than the other soil types. The Nevada 

crops were also significantly lower than the others. It is evident that there are 

significantly differing CR’s between species and also between soil type. 

Similarly, there were differences between plant species and crop types for iodine. 

Although potatoes were unable to grow in the Nevada soil, uptake in the Nevada soil for 

alfalfa and corn were slightly higher than for these crops in the Hanford soil, but both 

were less than in the South Carolina soil.
5-3

5.4 Uncertainties in the Results

The soil-to-plant uptake experiments were conducted with three soil types, three plant 

types, and two radionuclides. In order to have a reasonably reliable estimate of the mean 

and variance of each of these combinations, we attempted to have at least five replicate 

plants in each group. Within each soil/plant/radionuclide combination, the plant-to-plant 

variability, as represented by the ratio of the standard deviation of the measurements to 

the mean, ranged up to about 50% for the 237Np and up to about 50% for the 125I. Thus, 

for a single plant/soil/radionuclide combination, variations of over a factor of 2 are not 

unusual. The plants were grown under standardized conditions; in actual field conditions, 

where the soil characteristics, sunlight, temperature, and moisture conditions would not 

be expected to remain constant, the individual measurement variability will be higher. 

However, when averaged over an entire field or an entire harvest, the variability may be 

reduced.

Factors that we have observed that impact on the value of the transfer factor, besides soil 

characteristics and plant species, include stress on the growing plant (heat, watering), 

nutritional value of the soil for the plant (fertilization), maturity of the plant (influencing 

transport into edible portions), chemical form of the contaminant (materials deposited 

with irrigation from groundwater water may be more soluble than those that fall out from 

the atmosphere), and amount of available light (the corn did not grow well in the growth 

chambers because the light was less intense than natural sunlight). 

Concentrations of contaminants may also have an effect which is not included in the 

current model of linear uptake. The assumption of linearity may be appropriate for 

elements that are not essential to biological function, are not analogues of such elements, 

or are not absorbed by organisms via nutrient pathways. Linearity may not apply for 

contaminants that are nutrients or are chemical analogues for them. Thus, for the 

radionuclides evaluated here, linearity is likely for neptunium, but may not apply to 

iodine because it is a known micronutrient.

5.5 Comparison of CR Results to Current Literature

Soil-to-plant concentration ratios are used in most radioecological assessment models. A 

selection of concentration ratios for the types of crops and radionuclides assessed in this 

report are shown in Table 5.1. These are excerpted from the popular computer codes 

GENII (Napier et al. 2010) and RESRAD (Yu et al. 2001), from the compendia prepared 

by the International Union of Radioecologists published by the International Atomic 

Energy Agency (IAEA 1994; IAEA 2010), and from the biosphere model of Wasiolek 

(2004). The RESRAD (Biwer et al. 2000) values are taken from NCRP (1996), using the 

conservative value from NCRP and adding a geometric standard deviation (GSD) of 

either 2.5 or 3.0, which indicates a log-normal distribution with possible values ranging 

from about one-tenth to ten times the nominal value. Rather than a true distribution of 

the full range of uncertainty, this tends to greatly over-weight the larger values. The 

RESRAD values are for wet produce, and should be increased to be equivalent to the 

others for dry produce. It is interesting to notice that the various sources use different 
5-4

classifications of plant types (the Wasiolek [2004] biosphere code is derived from an 

earlier version of the GENII model [Napier et al. 1988] and has the same internal 

structure). The RESRAD code lumps all types of vegetation into one compartment. The 

IAEA provides summaries of multiple investigations by individual crop type; many 

modelers use the IAEA values as a basis, but the way in which the crops are aggregated 

may vary.

Because of the wide range of results found in the current literature shown in Table 5.1, 

generic concentration ratios are of limited use in site-specific dose analyses. The work 

performed for this report shows that there can be regional variations in soil-to-plant 

uptake. Within a single regional soil type, uncertainties in the soil-to-plant concentration 

ratio can be significantly reduced by site-specific investigations.

For neptunium and for iodine, the results generated by this study are substantially larger 

than the generic factors used in any of the models. This may have been the result of the 

study design, where the radionuclide label was added with the irrigation water. This may 

have resulted in the chemical form of the amended radionuclides being more soluble than 

those commonly used elsewhere. However, this degree of solubility should be expected 

for the type of environmental scenario being explored where the contaminant is delivered 

to the crop soil carried by irrigation water. The results of this study indicate that use of 

generic CR values adds an unpredictable degree of bias to performance assessments.

The scenario of radionuclide application used in this study was one of input with 

irrigation water. Both radionuclides tested herein tended to distribute in non-uniform 

fashion in the soil. Performance assessment models generally average radionuclides over 

a “plow layer” of between 10–30 cm thickness. For irrigation deposition of sorbed 

radionuclides, this is actually not representative, even after many years of deposition and 

plowing. In this respect, the somewhat higher effective CR values found in this study 

may actually be more representative of the modeled conditions.

This type of information is directly useful in formulating inputs to radioecological and 

food-chain models used in performance assessments and other kinds of environmental 

assessment. This food-chain pathway data may be used by the NRC staff to assess dose 

to persons who live and work in areas potentially affected by radionuclide releases from 

waste disposal facilities and decommissioning sites. These data are expected to be used 

in biosphere models to calculate the dose from groundwater release scenarios in 

performance assessment computer codes.
5-5

Table 5.1. Soil-to-Plant Concentration Ratios Commonly Used in Environmental Assessments (plant pCi/g dry wt.)/(soi

Staven et al.

(2003)

(GENII V.2)

Biwer et al.

(2000)

(RESRAD V.6)

IAEA

(TRS-364)

Wasiolek 2004 IAEA

(TRS

Element Crop Best 

Estimate

Best 

Estimate

GSD Best 

Estimate

Range Best 

Estimate

GSD Range Best 

Estim

Iodine

All Plants 0.02 2.5 0.02

Leafy 

Vegetables

0.04 0.026 9.9 0.000072 - 9.7 0.006

Other 

Vegetables

0.04 0.032 4.4 0.0007 - 1.5 0.007

Grain 0.04 0.025 10 0.000066 - 9.4 0.000

Forage 0.04 0.04 10 0.00011 - 15 0.003

Potato/Tuber 0.1 

Onion

Grass 0.0034 .00034 - 0.034

Neptunium

All Plants 0.02 2.5

Leafy 

Vegetables

0.032 0.059 4.4 0.0013 - 2.6 0.027 

Other 

Vegetables

0.013 0.031 4.9 0.0005 - 1.9 0.002

Grain 0.0027 0.0027 0.000023 -

0.083

0.0044 6.9 0.000031 - 0.63 0.002

Forage/Maize 0.032 0.021 0.0014 - 0.28 0.058 5.6 0.00068 - 4.9 0.06

Fodder

Potato/Tuber 0.0067 0.00071 - 0.14 0.005

Onion 0.033

Grass 0.069 0.13 - 0.57

*The RESRAD values are reported in wet weight of plant and should be increased by a factor of about 5 to be comparable with the oth
5-6

5.6 References

Biwer BM, S Kamboj, JJ Cheng, E Gnanapragasam, C Yu, J Arnish, D LePoire, 

YY Wang, JP Butler, H Hartmann, SY Chen. 2000. Parameter Distributions for Use in 

RESRAD and RESRAD-BUILD Computer Codes, Attachment C to Yu C, D LePoire, 

E Gnanapragasam, J Arnish, S Kamboj, BM Biwer, JJ Cheng, A Zielen, SY Chen. 2000. 

Development of Probabilistic RESRAD 6.0 and RESRAD-BUILD 3.0 Computer Codes. 

NUREG/CR-6697, U.S. Nuclear Regulatory Commission, Washington, D.C.

International Atomic Energy Agency (IAEA). 1994. Handbook of Parameter Values for 

the Prediction of Radionuclide Transfer in Temperate Environments, Technical Report 

Series #364, IAEA, Vienna, Austria.

International Atomic Energy Agency (IAEA). 2010. Handbook of Parameter Values for 

the Prediction of Radionuclide Transfer in Terrestrial and Freshwater Environments, 

IAEA Technical Reports Series No. 472, IAEA, Vienna, Austria.

Napier BA, RA Peloquin, DL Strenge, and JV Ramsdell. 1988. GENII - The Hanford 

Environmental Radiation Dosimetry Software System. Volume 1: Conceptual 

Representation, Volume 2: Users’ Manual, Volume 3: Code Maintenance Manual. 

PNL-6584, Vols. 1-3, Pacific Northwest Laboratory, Richland, Washington.

Napier BA, DL Strenge, JV Ramsdell, Jr, PW Eslinger, and CJ Fosmire. 2010. GENII 

Version 2 Software Design Document. PNNL-14584 Rev.3, Pacific Northwest National 

Laboratory, Richland, Washington. 

National Council on Ionizing Radiation and Protection (NCRP). 1996. Screening 

Models for Releases of Radionuclides to Atmosphere, Surface Water and Ground. NCRP 

Report No. 123, Vol. I., Bethesda, Maryland.

Staven LH, BA Napier, K Rhoads, and DL Strenge. 2003. A Compendium of Transfer 

Factors for Agricultural and Animal Products. PNNL-13421, Pacific Northwest 

National Laboratory, Richland, Washington.

Wasiolek M. 2004. Environmental Transport Input Parameters for the Biosphere 

Model. ANL-MGR-MD-000007, Rev. 2, Bechtel SAIC Company, Las Vegas, Nevada.

Yu C, AJ Zielen, J-J Cheng, DJ Lepoire, E Gnanapragasam, S Kambof, J Arnish, 

A Wallo III, WA Williams and H Peterson. 2001. User’s Manual for RESRAD 

Version 6. ANL/EAD-4, Argonne National Laboratory, Argonne, Illinois.



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NUREG/CR-7120 Radionuclide Behavior in Soils and Soil-to-Plant Concentration Ratios

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