Water Quality and Possible Sources of Nitrate in

the Cimarron Terrace Aquifer, Oklahoma, 2003

Scientific Investigations Report 2004–5221

Prepared in cooperation with the

Oklahoma Department of Environmental Quality

U.S. Department of the Interior

U.S. Geological Survey
Cover: Photos, clockwise from upper left:

Tractor and plow near Dover, Oklahoma. Photo by Jason R. Masoner, July 2003.

A well owner, right, helps USGS staff locate a well near Waynoka, Oklahoma. Photo by S. Jerrod Smith, July 2003.

Center-pivot irrigation of corn near Ringwood, Oklahoma. Photo by S. Jerrod Smith, July 2003.

Grain silos near Ringwood, Oklahoma. Photo by Jason R. Masoner, July 2003.

Center photo:

Horses near Cleo Springs, Oklahoma, with petroleum pump jack and storage tanks, background. Photo by Shana L. Mashburn, July 2003.
Masoner, J.R., and Mashburn, S.L.—Water Quality and Possible Sources of Nitrate in the Cimarron Terrace Aquifer, Oklahoma, 2003—USGS/SIR 2004–5221

Printed on recycled paper
U.S. Department of the Interior

U.S. Geological Survey

Water Quality and Possible Sources

of Nitrate in the Cimarron Terrace Aquifer,

Oklahoma, 2003

By Jason R. Masoner and Shana L. Mashburn

Prepared in cooperation with the Oklahoma Department of Environmental Quality

Scientific-Investigations Report 2004-5221
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

U.S. Geological Survey, Reston, Virginia: 2004

For sale by U.S. Geological Survey, Information Services

Box 25286, Denver Federal Center

Denver, CO 80225

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U.S. Geological Survey

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Oklahoma City, OK 73116

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UNITED STATES GOVERNMENT PRINTING OFFICE: OKLAHOMA CITY 2004
iii

Contents

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Purpose and scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Description of study area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Hydrogeology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Land use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Historical pesticide use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Selection of sampling sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Ground-water sampling and analysis methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Statistical analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Water quality in the Cimarron terrace aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Water properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Nutrients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Nitrogen isotopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Pesticides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Wastewater compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Possible sources of nitrate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Selected references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Appendixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Appendix 1. Quality Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Table 19. Nutrient concentrations for environmental and replicate samples, shown with relative

percent difference (RPD) values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Table 20. Nitrogen isotope delta values (δ15N) in nitrate for environmental and replicate samples, shown

with relative percent difference (RPD) values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Table 21. Pesticide concentrations for the single environmental and replicate sample in which

pesticides were detected, shown with relative percent differences (RPD) values . . . . . . . . . . . . 49

Table 22. Summary of pesticide environmental-matrix spike recoveries for selected pesticides

in U.S. Geological Survey schedule 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Table 23. Individual pesticide environmental-matrix spike recoveries for selected pesticides

in U.S. Geological Survey schedule 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Appendix 2. Water properties measured in samples from 45 wells in the Cimarron terrace aquifer, July

and August 2003. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Appendix 3. Nutrient concentrations in samples from 45 wells in the Cimarron terrace aquifer, July

and August 2003. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Appendix 4. Nitrogen isotope delta values (δ15N) in nitrate measured in samples from 45 wells

in the Cimarron terrace aquifer, July and August 2003 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Appendix 5. Concentrations of pesticide and metabolite compounds detected in samples from 15

of 45 wells in the Cimarron terrace aquifer, July and August 2003. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Appendix 6. Concentrations of wastewater compounds detected in 28 of 45 wells sampled in the

Cimarron terrace aquifer, July and August 2003 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
iv

Figures

1.Map showing locationof study areaand majorland-use determinations fromthe 1992National

Land Cover Dataset overlying the Cimarron terrace aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2. Graph showing land-use proportions in the study area overlying the Cimarron terrace aquifer. . . . . . . . 4

3.Map showing locationsof wells andreclassification ofNational Land CoverDataset intotwo

general land-use categories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Figures 4–5. Boxplots showing:

4. Distribution of water properties measured in samples from 45 wells in the Cimarron terrace aquifer,

July and August 2003. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

5.Distributionofspecificconductancemeasuredinwatersamplesfrom28wellslocated

in agricultural areas and 17 wells located in grassland areas in the Cimarron terrace

aquifer, July and August 2003. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

6.Graphshowingnumberofsamplesinselectednitrateconcentrationsranges. . . . . . . . . . . . . . . . . . . . . . . 19

7.Map showing locationof wells andselected nitrateconcentration ranges insamples fromthe

Cimarron terrace aquifer, July and August 2003. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

8. Boxplots showing distribution of nitrate concentrations in samples from 28 wells located

in agricultural areas and 17 wells located in grassland areas in the Cimarron terrace aquifer,

July and August 2003. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

9. Graph showing nitrogen isotope delta values (δ15N) in nitrate measured in samples from 42

of 45 wells in the Cimarron terrace aquifer, July and August 2003.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

10.Boxplotsshowingnitrogenisotopedeltavalues(δ15N)innitratemeasuredinsamplesfrom

28 wells in agricultural areas andδ15N values from 14 of 17 wells in grassland areas in the

Cimarron terrace aquifer, July and August 2003. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

11. Map showing locations of wells with samples having detectable concentrations of pesticide compounds in the Cimarron terrace aquifer, July and August 2003. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

12.Graphshowingdistributionofpesticideandmetabolitecompoundsdetectedinsamplesfrom15

of 45 wells in the Cimarron terrace aquifer, July and August 2003. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

13.Mapshowinglocationofwellswithsampleshavingdetectableconcentrationsofwastewater

compounds in the Cimarron terrace aquifer, July and August 2003. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

14. Piechart showingproportion of wastewatercompounds detected inwater samplesfor sixselected

wastewater-effluent categories. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Figures 15–16. Graphs showing:

15. Wastewatercompounds detectedin samples from28 of45 wellsin the Cimarronterrace

aquifer, July and August 2003. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

16.Distributionofnitrogenisotopedeltavalues(δ15N)innitratemeasuredinsamples,grouped

by possible sources of nitrate, from 42 of 45 wells in the Cimarron terrace aquifer, July

and August 2003. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

17.Boxplotsshowingdistributionofnitrogenisotopedeltavalues(δ15N)innitrateforselectednitratesource

categories. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

18.Numberofwellslocatedinagriculturalandgrasslandareasforselectednitratesource

categories. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Tables

1. Pesticide-use estimates for the 30-most commonly applied pesticide compounds for counties

included in the Cimarron terrace aquifer, 1992-1995, derived from county pesticide-use

information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
v

2. Location and well information for 45 wells sampled in the Cimarron terrace aquifer, July and August

2003 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

3.Nutrients and interimreporting levels asof 2003,U.S. Geological SurveyNational WaterQuality

Laboratory Schedule 2752 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

4. Pesticidesand reportinglevels as of2003, U.S.Geological Survey NationalWater Quality Laboratory

Schedule 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

5.Wastewatercompoundsandminimumreportinglevelsasof2003,U.S.GeologicalSurveyNational

Water Quality Laboratory custom lab code 8033 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

6. Statistical summary of water properties in samples from 45 wells in the Cimarron terrace aquifer,

July and August 2003 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

7. Statistical summary of water properties in samples from 28 wells located in agricultural areas in the

Cimarron terrace aquifer, July and August 2003 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

8. Statistical summary of water properties in samples from 17 wells located in grassland areas in the

Cimarron terrace aquifer, July and August 2003 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

9.Statistical summary ofnutrient data for45 ground-watersamples collected inthe Cimarronterrace

aquifer, July and August 2003 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

10. Statistical summary of nutrient data collected in samples from 28 wells located in agricultural areas

in the Cimarron terrace aquifer, July and August 2003 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

11. Statistical summary of nutrient data collected in samples from 17 wells located in grassland areas

in the Cimarron terrace aquifer, July and August 2003 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

12. Range of nitrogen isotope delta values (δ15N) in nitrate in water for selected sources of nitrate . . . . . . 23

13. Statistical summary of nitrogen delta values (δ15N) in nitrate measured in samples from 28 wells

in agricultural areas and 14 of 17 wells in grassland areas in the Cimarron terrace aquifer,

July and August 2003 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

14.Detectedpesticideandmetabolitecompoundsandrangeofconcentrationsinsamplesfrom15

of 45 wells in the Cimarron terrace aquifer, July and August 2003 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

15.Detected wastewater compoundsand range ofconcentrations insamples from 28of 45wells

sampled in the Cimarron terrace aquifer, July and August 2003 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

16.Descriptionofnitratesourcecategoriesusedtodeterminepossiblesourcesofnitrate,based

on nitrate concentrations, nitrogen isotope delta values (δ15N) in nitrate, and detection

of pesticides and wastewater compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

17.Numberofdetectedpesticidesandwastewatercompounds,land-usecategories,nitrate

concentrations, nitrogen isotope delta values (δ15N) in nitrate, and possible sources of nitrate

in water samples from the Cimarron terrace aquifer, July and August 2003 . . . . . . . . . . . . . . . . . . . . . . . 37

18.Statistical summary ofnitrogen isotope deltavalues (δ15N)in nitrate,for selectednitrate source

categories, from samples of 42 of 45 wells in the Cimarron terrace aquifer, July and

August 2003. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
vi

Conversion Factors and Datum

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F = (1.8 × °C) + 32

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C = (°F - 32) / 1.8

Vertical coordinate information is referenced to North American Vertical Datum of 1988 (NAVD

88).

Horizontal coordinate information is referenced to North American Datum of 1983 (NAD 83).

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at

25 ̊C).

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) or

micrograms per liter (μg/L).

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

kilometer (km) 0.6214 mile (mi)

Area

acre 4,047 square meter (m2)

Volume

gallon (gal) 3,785 milliliter (mL)

cubic inch (in3) 0.01639 liter (L)

liter (L) 0.2642 gallon (gal)

Mass

pound, avoirdupois (lb) 0.4536 kilogram (kg)
Water Quality and Possible Sources of Nitrate in the

Cimarron Terrace Aquifer, Oklahoma, 2003

By Jason R. Masoner and Shana L. Mashburn

Abstract

Water from the Cimarron terrace aquifer in northwest

Oklahoma commonly has nitrate concentrations that exceed the

maximum contaminant level of 10 milligrams per liter of nitrite

plus nitrate as nitrogen (referred to as nitrate) set by the U.S.

Environmental Protection Agency for public drinking water

supplies. Starting in July 2003, the U.S. Geological Survey, in

cooperation with the Oklahoma Department of Environmental

Quality, conducted a study in the Cimarron terrace aquifer to

assess the water quality and possible sources of nitrate. A qualitative and quantitative approach based on multiple lines of evidence from chemical analysis of nitrate, nitrogen isotopes in

nitrate, pesticides (indicative of cropland fertilizer application),

and wastewater compounds (indicative of animal or human

wastewater) were used to indicate possible sources of nitrate in

the Cimarron terrace aquifer.

Nitrate was detected in 44 of 45 ground-water samples and

had the greatest median concentration (8.03 milligrams per

liter) of any nutrient analyzed. Nitrate concentrations ranged

from <0.06 to 31.8 milligrams per liter. Seventeen samples had

nitrate concentrations exceeding the maximum contaminant

level of 10 milligrams per liter. Nitrate concentrations in agricultural areas were significantly greater than nitrate concentrations in grassland areas.

Pesticides were detected in 15 of 45 ground-water samples. Atrazine and deethylatrazine, a metabolite of atrazine,

were detected most frequently. Deethylatrazine was detected in

water samples from 9 wells and atrazine was detected in samples from 8 wells. Tebuthiuron was detected in water samples

from 5 wells; metolachlor was detected in samples from 4

wells; prometon was detected in samples from 4 wells; and

alachlor was detected in 1 well. None of the detected pesticide

concentrations exceeded the maximum contaminant level or

health advisory level set by the U.S. Environmental Protection

Agency.

Wastewater compounds were detected in 28 of 45 groundwater samples. Of the 20 wastewater compounds detected, 11

compounds were from household chemicals, 3 compounds

were hydrocarbons, 2 compounds were industrial chemicals, 2

compounds were pesticides, 1 compound was of animal source,

and 1 compound was a detergent compound. The most frequently detected wastewater compound was phenol, which was

detected in 23 wells. N,N-diethyl-meta-toluamide (DEET) was

detected in water samples from 5 wells. Benzophenone, ethanol-2-butoxy-phosphate, and tributylphosphate were detected

in water samples from 3 wells.

Fertilizer was determined to be the possible source of

nitrate in samples from 13 of 45 wells sampled, with δ15N values ranging from 0.43 to 3.46 permil. The possible source of

nitrate for samples from the greatest number of wells (22 wells)

was from mixed sources of nitrate from fertilizer, septic or

manure, or natural sources. Mixed nitrate sources had δ 15N values ranging from 0.25 to 9.83 permil. Septic or manure was

determined as the possible source of nitrate in samples from 2

wells. Natural sources were determined to be the possible

source of nitrate in samples from 7 wells, with δ 15N values

ranging from –0.83 to 9.44 permil.

Introduction

Water from the Cimarron terrace aquifer in northwestern

Oklahoma (fig. 1) commonly has nitrate concentrations that

exceed the maximum contaminant level (MCL) of 10 milligrams per liter (mg/L) of nitrite plus nitrate as nitrogen (referred

to as nitrate in subsequent discussions due to low nitrite concentrations) set by the U.S. Environmental Protection Agency

(USEPA) for public drinking water supplies (U.S. Environmental Protection Agency, 2002a). Fifty of 161 ground-water samples (31 percent) collected from the Cimarron terrace aquifer

from 1985 through 1993 had nitrate concentrations that

exceeded the MCL (Becker, 1994). Eighty percent of groundwater samples collected in the Cimarron terrace aquifer at or

near confined animal feeding operations (CAFOs) in 2001 had

nitrate concentrations exceeding the MCL for nitrate (Becker

and others, 2002). Consumption of nitrate concentrations

greater than 4 mg/L in water from community wells has been

associated with an increased risk of cancer (Ward and others,

1996). Elevated nitrate concentrations also have been linked to

hypertension (Malberg and others, 1978), diabetes (Parslow and

others, 1997), methemoglobinemia (blue-baby syndrome), and

possible birth defects (National Governors’ Association, 1991).

The Cimarron terrace aquifer is a shallow, unconfined

aquifer that may have moderate to high vulnerability to contamination from land-use activities (Osborn and others, 1998,

Appendix B, pg. B-9). Land uses overlying the Cimarron terrace aquifer include raising of livestock and production of feed-
Ames Alva Dover Bison Helena Waynoka Orienta

Freedom

Ringwood

Fairview

Drummond

Cres

Hennessey

Kingfisher

Cleo Springs

Enid

-99°

-99°

-98°30'

-98°30'

-98°

-98°

36°

36°30'

WOODWARD

WOODS

ALFALFA

GARFIELD

KINGFISHER

BLAINE

0 10 20 5 KILOMETERS0 10 20 5 M

Base data from Adams and others (1997), scale 1:100,000USGS Albers Equal Area Conic ProjectionNorth American Datum of 1983

EXPLANATIONLand Use

Mixed Deciduous and Evergreen ForestsSand dunes, Transitional, and Urban areasShrublandsGrasslandsCultivated Hay and PastureRow CropsSmall Grains

Turkey 

Creek

Cimarron River

Eagle Chief

Cree

k

Towns

Little SaharaState Park

MAJOR County Boundary

Cimarron Terrace Aquifer

Streams

 Figure 1. Location of study area and major land-use determinations from the 1992 National Land Cover Dataset overlying the Cimarron terrace 

Geological Survey, 2002).
Introduction 3

grain crops such as wheat, corn, and soybeans (Bloyd and Shepler, 2001). Agricultural activities are commonly associated with

elevated nitrate concentrations in ground water, particularly

where row crops are irrigated (Mueller and Helsel, 1996).

Starting in July 2003, the U.S. Geological Survey, in cooperation with the Oklahoma Department of Environmental Quality, conducted a study in the Cimarron terrace aquifer to assess

the water quality, land uses, and possible sources of nitrate. An

understanding of the water quality and possible sources of

nitrate in the Cimarron terrace aquifer will help water-resources

managers and local residents better protect the water resources

of the Cimarron terrace aquifer.

Purpose and Scope

The purpose of this report is to describe the water quality

and possible sources of nitrate in the Cimarron terrace aquifer.

Forty-five ground-water wells in the Cimarron terrace aquifer

were randomly selected. Wells were grouped into two land-use

categories, areas of agricultural use, referred to as agricultural

areas, and grassland areas not disturbed by agriculture, referred

to as grassland areas. Wells were sampled for nutrients, nitrogen isotope ratios in nitrate, pesticides, and wastewater compounds during July and August 2003.

Concentrations of nutrients, nitrogen isotope ratios in

nitrate, pesticides, and wastewater compounds sampled from

wells in agricultural and grassland areas were statistically and

graphically analyzed. A qualitative and quantitative approach

based on multiple lines of evidence from chemical analysis of

nitrate, nitrogen isotopes in nitrate, commonly applied pesticides (indicative of fertilizer application), and wastewater compounds (indicative of animal or human waste) was used to indicate possible sources of nitrate in the Cimarron terrace aquifer.

Description of Study Area

The study area consists of 1,305 square miles (mi2) and

includes Quaternary-age terrace deposits located north of the

Cimarron River floodplain extending from Freedom to Guthrie

in northwest Oklahoma (fig. 1). The Cimarron terrace aquifer

lies within the Cimarron River drainage basin, which has a

drainage area of approximately 18,927 mi2 (Adams and Bergman, 1996). Average annual precipitation in the study area

ranges from 26 inches in the northwest to 32 inches in the southeast (Johnson and Duchon, 1995).

Ground water in the Cimarron terrace aquifer is an important economic resource for northwest Oklahoma. Approximately 63 percent of ground-water withdrawals in Alfalfa,

Garfield, Kingfisher, Major, and Woods Counties in 2000 were

withdrawn from the Cimarron terrace aquifer. The Cimarron

terrace aquifer produced over 4.27 billion gallons of water for

public supply in 2000. More than 4.40 billion gallons of water

from the aquifer were used for irrigation and livestock purposes

in 2000 (Phyllis Robertson, Oklahoma Water Resources Board,

written commun., 2003).

Hydrogeology

The Cimarron terrace aquifer is underlain by Permian-age

units that crop out along the study area boundary (Adams and

Bergman, 1996). Cimarron terrace sediments were originally

deposited by the southward migration of the ancestral Cimarron

River (Adams and Bergman, 1996). Since deposition, these terrace sediments have been reworked by water and wind that creates sand dunes. The terrace deposits consist of interfingered

lenses of clay, sandy clay, and cross-bedded poorly-sorted sand

and gravel and range from 0 to 120 feet (ft) (Adams and Bergman, 1996). The Cimarron terrace sediments are composed of

quartz, feldspar, ferruginous shale, and quartzitic sandstone

(Reed and others, 1952). Most dunes in the study area are stabilized by vegetation. However, a field of large, active dunes

located within and around Little Sahara State Park, 4 miles

south of Waynoka (fig. 1), are unvegetated and can reach

heights as high as 70 ft (Adams and Bergman, 1996).

Ground-water flow in the Cimarron terrace aquifer is generally southeast to southwest flowing towards the Cimarron

River, except where flow direction is influenced by perennial

tributaries to the Cimarron River (Adams and Bergman, 1996).

Potentiometric surface maps shown in Adams and Bergman

(pg, 20-22, 1996) indicate that surface water is not a major

source of recharge to the aquifer. The two greatest sources of

recharge to the Cimarron terrace aquifer are infiltration of precipitation and irrigation return flow (Adams and Bergman,

1996).

Land Use

Agriculture is the predominant land use in the study area

(fig. 1). Agriculture in this report refers to areas that have been

planted or are intensely managed for the production of livestock

for food. Agricultural land use overlying the aquifer consists of

41.4 percent small grains, 7.0 percent row crops, and 6.3 percent cultivated hay and pasture (fig. 2) (U.S. Geological Survey,

2002). Additional land-use types overlying the aquifer are

grasslands (27.1 percent), shrublands (11.0 percent), mixed

deciduous and evergreen forest (4.4 percent), and other less

prevalent land uses (2.8 percent). The development of modern

irrigation systems has facilitated an increase in the cultivation

of wheat, corn, and oats in the Cimarron terrace aquifer (U.S.

Department of Agriculture, 1996). Numerous CAFOs have

been established since 1994 overlying the Cimarron terrace

aquifer (Becker and others, 2002; Oklahoma Department of

Environmental Quality, 2003). Oil and gas production and

related petroleum service oriented companies are the predominant industry in the Cimarron terrace aquifer area (Mark Gregory, Oklahoma State University, written commun., 1988).

Historical Pesticide Use

According to pesticide-use estimates for counties included

in the study area, dimethoate, 2,4-D, bromoxynil, and ethyl-par-
4 Water Quality and Possible Sources of Nitrate in the Cimarron Terrace Aquifer, Oklahoma, 2003

0

5

10

15

20

25

30

35

40

45

0.6

Sand dunes

6.3

Cultivated hay and pasture

7.0

Row crops

41.4

Small grains

0.3

Urban/Residential

4.4

Mixed deciduous

and evergreen

forest

11.0

Shrublands

27.1

Grasslands

1.9

Transitional

LAND USES

PERCENT LAND USE

athion were the most abundantly applied pesticide compounds

from 1992 to 1995 (G.P. Thelin, U.S. Geological Survey, written commun., 2001). Dimethoate and ethyl-parathion are insecticides commonly applied on wheat, alfalfa, corn, sorghum,

cotton, sunflowers, soybeans, barley, oats, and rye (Thelin and

Gianessi, 2000). Bromoxynil and 2,4-D are herbicides commonly applied on common forage crops, wheat, corn, barley,

sorghum, and oats (G.P. Thelin, U.S. Geological Survey, written

commun., 2001). For counties included in the study area,

Garfield County had the greatest total pesticide use, followed by

pesticide use in Alfalfa and Woods Counties (table 1).

Acknowledgments

The authors thank the homeowners and landowners who

allowed access to domestic and stock wells; to the cities of

Alva, Enid (located east of study area), and Waynoka; and the

Major County Rural Water District for allowing access to public water-supply wells. Additional thanks to U.S. Geological

Survey employees and volunteers, Martin Schneider, Chris

Neel, Jerrod Smith, and Martyn McMurphy, who assisted in

data collection and to Mike Sughru who helped to combine

Geographic Information System (GIS) data bases.

Methods

This section describes the methodology used to select sampling locations within the Cimarron terrace aquifer. Information

about the techniques of ground-water sampling, chemical analysis, and statistical analysis also are provided.

Selection of Sampling Sites

Well-location data stored in the U.S. Geological Survey Ground

Water Information System (GWSI) and the Oklahoma Water

Resources Board (OWRB) data bases were combined into a

single GIS data set. Land-use data from the National Land

Cover Dataset (NLCD) (U.S. Geological Survey, 2002) were

used to categorize land uses overlying the Cimarron terrace

aquifer into two general categories, agricultural areas and grassland areas, because those were the most predominant land uses

(fig. 3). NLCD land-use categories small grains, row crop, and

cultivated pasture or hay were grouped into one land-use category, defined agricultural. NLCD land-use categories grassland, shrubland, forested areas, sand dunes, and transitional

areas were grouped into one land-use category, defined in this

report as grasslands. While sampling sites were grouped into

two general categories, most of the sampled wells were located

in rural homesteads, which could be considered a separate landuse category within the larger more general NLCD land-use categories.

 Figure 2. Land-use proportions in the study area overlying the Cimarron terrace aquifer (U.S. Geological Survey, 2002).
Methods 5

 Table 1. Pesticide-use estimates for the 30-most commonly applied pesticide compounds for counties included in the Cimarron terrace

aquifer, 1992-1995, derived from county pesticide-use information (G.P. Thelin, U.S. Geological Survey, written commun., 2001)

[all units are in pounds of active ingredient; -, indicates pesticide was not applied in county or the amount applied was less than amount needed to be in the top 30

most applied]

Pesticides Alfalfa Garfield Kingfisher Logan Major Woods

Dimethoate 52,235 73,892 44,666 16,415 32,128 39,944

2,4-D 21,585 30,651 25,360 18,369 24,527 38,484

Bromoxynil 19,212 27,525 16,581 6,073 11,777 14,836

Ethyl-parathion 20,354 13,518 9,763 4,681 8,326 9,131

Methyl-parathion 18,422 8,841 7,159 3,849 6,610 6,821

Permethrin 4,470 4,626 2,973 1,211 2,278 2,701

MCPA 2,548 3,628 2,191 842 1,633 1,951

Dicamba 2,145 3,070 2,738 2,201 2,774 4,404

Glyphosate 1,995 2,845 1,724 641 1,304 1,541

Chlorpyrifos 2,986 2,574 1,718 806 1,571 1,585

Malathion 5,437 1,356 1,486 1,009 1,613 1,485

Carbofuran 5,280 1,326 1,463 973 1,710 1,452

Tebuthiuron 887 1,217 1,198 - 1,389 2,468

Chlorsulfuron 817 1,170 705 258 502 631

Picloram 455 639 637 576 709 1,219

Propiconazole 272 390 234 87 167 210

Carbaryl 1,191 296 324 290 356 323

Atrazine 420 286 249 362 1,322 336

Hexazinone 989 247 270 180 293 270

Triasulfuron 148 212 128 - 91 115

2,4-DB 791 197 216 144 235 216

Metolachlor 209 142 147 180 654 168

Metsulfuron - 135 81 - 58 73

Methomyl 201 55 - 78 83 61

Alachlor - 43 65 55 273 51

Chlorothalonil 160 - - 609 225 6

Terbufos - - - - 246 29

Disulfoton - - 112 - 677 14

Fonofos - - 63 - 89 -

Cyanazine - - 44 - 273 -

Total 163,209 178,881 122,295 59,889 103,893 130,525
W15 W7

W1

W2

W8

W4

W6 W5

W3

W9

W33

W41

W39 W40

W44

W36

W45

W42

W34

W28

W38

W32

W23

W25

W22

W37

W43

W29

W24

W10

W35

W30

W27

W19

W17

W13

W11

W16

W26

W21

W18

W14

W20

W31

W12

-99°

-99°

-98°30'

-98°30'

-98°

-98°

36°

36°30'

WOODWARD

WOODS

ALFALFA

GARFIELD

KINGFISHER

BLAINE

MAJOR

0 10 20 5 KILOMETE0 10 20 5 

Base from Adams and others (1997), scale 1:100,000USGS Albers Equal Area Conic ProjectionNorth American Datum of 1983

Primary Land Use Category

Agriculture (small grains, row crops, and cultivated hay & pasture)Grassland (grasslands, shrublands, mixed deciduous & evergreen forests,

County Boundary

Cimarron Terrace Aquiferand sand dunes, transitional, and urban areas)

EXPLANATION

SAMPLING SITE AND WELL NUMBER W31

 Figure 3. Locations of wells and reclassification of National Land Cover Dataset into two general land-use categories (U.S. Geological Survey, 200
Methods 7

Forty-five ground-water sampling locations were selected

randomly (table 2) using a computerized stratified random

selection algorithm (Scott, 1990). A modification to a simple

random selection of wells was implemented to ensure an equalarea distribution of selected wells in the agricultural and grassland areas. Agricultural and grassland areas were divided into

10-kilometer grid cells and one or more wells were randomly

selected within each grid cell. Ultimately, 28 wells were

selected in the agricultural areas and 17 wells were selected in

the grassland areas (fig. 3). Wells that overlaid an agriculture

land use were designated an agricultural well, and wells that

overlaid a grassland land use were designated a grassland well.

More wells were selected in agricultural areas, because the

majority land use was agriculture. The owners of the selected

wells were contacted to gain permission to include their well in

the study. There were instances where permission could not be

obtained. In those cases, a replacement well was located in the

same or adjacent cell. Two of the 45 wells, W9 and W31, were

selected to represent background nitrate concentrations in the

study area. These wells were located in remote grassland areas

more than 6 miles away from agricultural activities or septic

systems. W9 is a well located in a remote area in Kingfisher

County near the Cimarron River. W31 is a water-supply well

used by the Oklahoma Department of Transportation to supply

water needed for temporary road maintenance and construction

purposes located in Major County. Although W31 was not near

any major nutrient sources, a 5-acre area starting 20 ft east of

the well was used as a staging ground for heavy-duty and lightduty vehicles used for road construction.

Ground-Water Sampling and Analysis Methods

Fifty-two water samples were collected from 45 wells in

the Cimarron terrace aquifer in July and August 2003. Seven

samples were collected for quality-control purposes, which are

described in Appendix 1. Field measurements of specific conductance, pH, water temperature, and dissolved oxygen were

recorded every 3 minutes with a calibrated multi-probe meter in

a sealed flow-through cell to monitor changes in water quality

while purging. After three well volumes had been purged and

field measurements had stabilized, samples were collected

using U.S. Geological Survey protocols (Wilde and others,

1998, Table 6.0-1, pg. 6).

Nutrients, nitrogen isotopes, pesticides, and wastewater

compounds were analyzed from samples collected mostly from

domestic or public-supply wells equipped with submersible

pumps. Thirty-one of the 45 wells were domestic wells, 10 were

public water-supply wells, 3 were irrigation wells, and 1 was a

low-volume general water-supply well leased by the Oklahoma

Department of Transportation. Samples were collected through

Teflon tubing attached to spigots at or near the wellhead. All

samples were collected inside a sealed preservation chamber to

limit exposure from potential sources of contamination in the

atmosphere (Horowitz and others, 1994). Water for nutrient

compounds was filtered in the field through a 0.45-micron disposable capsule filter and collected in 125-milliliter brown

polyethylene bottles. Water for nitrogen isotope samples and

wastewater compounds was not filtered. Samples for nitrogen

isotopes were collected in 1-liter polyethylene bottles with

poly-seal caps. Water for pesticide compounds was filtered in

the field using an aluminum plate-filter assembly with a glassfiber filter with a 0.7-micrometer (μm) nominal pore size,

baked at 450 degrees Celsius, collected in 1-liter baked amber

glass bottles sealed with Teflon-lined caps. Samples of wastewater compounds were collected in 1-liter baked amber glass

bottles sealed with Teflon-lined caps. All samples upon collection at each well were immediately submersed in ice and chilled

to less than 4 degrees Celsius. Nutrients, pesticide, and wastewater compound samples were shipped submersed in ice to the

laboratory for analysis within 48 hours of sample collection.

Nitrogen isotope samples were frozen within 24 hours of sample collection and were shipped to the laboratory 3 weeks later,

after all samples had been collected.

Water samples collected during this study were sent to two

laboratories. Samples were analyzed at the U.S. Geological Survey National Water Quality Laboratory (NWQL) in Lakewood,

Colorado, for 6 nutrients (table 3), 52 pesticides (table 4), and

72 wastewater compounds (table 5). Nitrogen-isotope samples

were analyzed at the University of Nebraska Water Sciences

Laboratory in Lincoln, Nebraska.

Nutrients were analyzed according to methods presented

in Fishman (1993). Pesticides were extracted at the NWQL by

solid-phase extraction and were analyzed by selected ion monitoring with gas chromatography/mass spectrometry (Zaugg

and others, 1995). Wastewater compounds were extracted at the

NWQL by continuous liquid-liquid extraction using methylene

chloride solvent and were analyzed by full scan capillary-column gas chromatography/mass spectrometry (Steven Zaugg,

U.S. Geological Survey, written commun., 2003).

Preparation for nitrogen isotope analysis involves steam

distillation, and a quantitative conversion to nitrogen gas that is

purified and collected on a high vacuum preparation system.

Nitrogen isotope analysis was done using isotope ratio mass

spectrometer (Daniel Snow, University of Nebraska Water Sciences Laboratory, written commun., 2003).

There are instances when a concentration value is reported

as an estimated concentration (E). An estimated concentration

value has been confirmed during the laboratory analysis, but the

actual concentration is reported as an estimate for one or more

of the following reasons: (1) the calculated concentration is

greater than or equal to the long-term method detection level

(LT-MDL) but less than the lowest calibration standard (LS), or

(2) the calculated concentration is greater than or equal to the

LT-MDL but less than the laboratory reporting level (LRL)

(Childress and others, 1999). The unquantified result of “M” is

preferable in instances of very low concentrations below the

reporting level when material has been detected and verified.
8 Water Quality and Possible Sources of Nitrate in the Cimarron Terrace Aquifer, Oklahoma, 2003

 Table 2. Location and well information for 45 wells sampled in the Cimarron terrace aquifer, July and August 2003

[-, not measured, well casing inaccessible; ID, identification number]

Well number

(fig. 3)

U.S. Geological

Survey

station ID

County Depth of well

(feet)

Depth to water

(feet) Date measured Land use

W1 355351097400301 Logan 57.3 25.2 08/07/03 Agriculture

W2 355812097460001 Kingfisher 61.5 33.7 07/18/03 Agriculture

W3 355842097570001 Kingfisher 29.8 13.5 07/16/03 Grassland

W4 360004097523601 Kingfisher 70.0 15.3 07/15/03 Agriculture

W5 360236097593501 Kingfisher 43.0 22.9 07/15/03 Agriculture

W6 360300098044601 Kingfisher 52.0 11.9 07/15/03 Grassland

W7 360451097534801 Kingfisher 98.0 37.8 07/11/03 Agriculture

W8 360605098000401 Kingfisher 58.0 18.7 07/15/03 Agriculture

W9 360653098085601 Kingfisher - - 07/16/03 Grassland

W10 360726098040101 Kingfisher 97.0 11.6 07/11/03 Agriculture

W11 360851098023901 Kingfisher 108 12.9 07/08/03 Agriculture

W12 361005098072601 Major 62.0 20.1 07/16/03 Agriculture

W13 361159098051501 Garfield 109 12.8 07/08/03 Agriculture

W14 361303098131501 Major 51.1 15.2 07/10/03 Grassland

W15 361347098120901 Major 65.0 9.80 07/10/03 Agriculture

W16 361454098142601 Major 65.0 25.0 07/09/03 Grassland

W17 361712098103401 Major 108 33.6 07/08/03 Agriculture

W18 361812098192101 Major 60.0 9.50 07/09/03 Agriculture

W19 361813098103201 Major 76.8 21.3 07/08/03 Agriculture

W20 361850098145201 Major - - 07/10/03 Agriculture

W21 361939098215301 Major 60.0 42.2 07/09/03 Grassland

W22 362146098215401 Major 65.0 40.1 07/16/03 Agriculture

W23 362212098165201 Major 55.0 21.9 07/16/03 Agriculture

W24 362233098243601 Major 40.6 28.6 08/07/03 Grassland

W25 362426098221001 Major 65.1 34.8 07/16/03 Agriculture

W26 362435098282201 Major 52.6 24.2 07/09/03 Grassland

W27 362530098355201 Woods - 9.70 07/03/03 Grassland

W28 362655098253101 Major 50.0 19.6 07/17/03 Agriculture

W29 362657098203101 Major 69.4 25.4 08/08/03 Agriculture

W30 362800098383701 Woods 87.5 30.4 07/02/03 Grassland

W31 362842098482401 Woods 26.4 9.70 07/02/03 Grassland

W32 362939098225701 Alfalfa 75.0 35.0 07/17/03 Agriculture

W33 363023098424801 Woods 60.0 16.1 07/16/03 Grassland

W34 363113098315201 Alfalfa 33.0 7.90 07/11/03 Agriculture

W35 363211098392401 Woods 59.8 6.60 07/03/03 Grassland

W36 363330098470001 Woods 29.0 6.60 07/08/03 Grassland

W37 363348098325401 Woods 40.4 6.30 07/09/03 Agriculture

W38 363445098264001 Alfalfa 48.0 16.4 07/23/03 Agriculture
Methods 9

W39 363452098384301 Woods 50.0 4.50 07/08/03 Grassland

W40 363510098514601 Woods 70.0 17.0 07/02/03 Agriculture

W41 363735098551801 Woods 40.0 12.0 07/11/03 Grassland

W42 363834098343801 Woods 70.0 18.0 07/09/03 Agriculture

W43 364519098311701 Alfalfa 32.0 11.9 07/09/03 Agriculture

W44 364258099000801 Woods 30.0 6.00 07/08/03 Grassland

W45 364605098350001 Woods 89.0 19.5 07/11/03 Agriculture

 Table 3. Nutrients and interim reporting levels as of 2003, U.S. Geological Survey National Water Quality Laboratory Schedule 2752

 [method reference: Fishman (1993); mg/L, milligrams per liter]

Constituent Interim

reporting levels Unit

Nitrogen, nitrite 0.008 mg/L

Nitrogen, nitrite plus nitrate1

1Referred to as nitrate in this report

0.060 mg/L

Nitrogen, ammonia 0.04 mg/L

Nitrogen, ammonia plus organic nitrogen 0.10 mg/L

Phosphorus 0.004 mg/L

Phosphorus, orthophosphate 0.018 mg/L

 Table 2. Location and well information for 45 wells sampled in the Cimarron terrace aquifer, July and August 2003—Continued

[-, not measured, well casing inaccessible; ID, identification number]

Well number

(fig. 3)

U.S. Geological

Survey

station ID

County Depth of well

(feet)

Depth to water

(feet) Date measured Land use
10 Water Quality and Possible Sources of Nitrate in the Cimarron Terrace Aquifer, Oklahoma, 2003

 Table 4. Pesticides and reporting levels as of 2003, U.S. Geological Survey National Water Quality Laboratory Schedule 2001

[method reference: Zaugg and others (1995); μg/L, micrograms per liter; Irl, interim reporting level; Mrl, minimum reporting level]

Pesticide Reporting levels Unit Reporting

level type Use

2,6-Diethylaniline 0.006 μg/L Irl Fungicide

Acetochlor 0.006 μg/L Irl Herbicide

Alachlor 0.005 μg/L Irl Herbicide

alpha-HCH 0.005 μg/L Mrl Insecticide

Atrazine 0.007 μg/L Irl Herbicide

Azinphos-methyl 0.05 μg/L Irl Insecticide

Benfluralin 0.01 μg/L Irl Herbicide

Butylate 0.002 μg/L Irl Herbicide

Carbaryl 0.041 μg/L Irl Insecticide

Carbofuran 0.02 μg/L Irl Insecticide

Chlorpyrifos 0.005 μg/L Irl Insecticide

cis-Permethrin 0.006 μg/L Irl Insecticide

Cyanazine 0.018 μg/L Irl Herbicide

Dacthal 0.003 μg/L Irl Herbicide

Deethylatrazine (metabolite) 0.006 μg/L Irl Herbicide

Desulfinylfipronil 0.004 μg/L Irl Insecticide

Desulfinylfipronil amide 0.009 μg/L Irl Insecticide

Diazinon 0.005 μg/L Mrl Insecticide

Dieldrin 0.005 μg/L Irl Insecticide

Disulfoton 0.021 μg/L Irl Insecticide

EPTC 0.002 μg/L Irl Herbicide

Ethalfluralin 0.009 μg/L Irl Herbicide

Ethoprophos 0.005 μg/L Irl Insecticide

Fipronil 0.007 μg/L Irl Insecticide

Fipronil sulfide 0.005 μg/L Irl Insecticide

Fipronil sulfone 0.005 μg/L Irl Insecticide

Fonofos 0.003 μg/L Irl Insecticide

Lindane 0.004 μg/L Irl Insecticide

Linuron 0.035 μg/L Irl Herbicide

Malathion 0.027 μg/L Irl Insecticide
Methods 11

Metolachlor 0.013 μg/L Irl Herbicide

Metribuzin 0.006 μg/L Irl Herbicide

Molinate 0.002 μg/L Irl Herbicide

Napropamide 0.007 μg/L Irl Herbicide

p,p'-DDE 0.003 μg/L Irl Insecticide

Parathion 0.01 μg/L Irl Insecticide

Parathion-methyl 0.006 μg/L Irl Insecticide

Pebulate 0.004 μg/L Irl Herbicide

Pendimethalin 0.022 μg/L Irl Herbicide

Phorate 0.011 μg/L Irl Insecticide

Prometon 0.015 μg/L Irl Herbicide

Propachlor 0.025 μg/L Irl Herbicide

Propanil 0.011 μg/L Irl Herbicide

Propargite 0.023 μg/L Irl Insecticide

Propyzamide 0.004 μg/L Irl Herbicide

Simazine 0.005 μg/L Irl Herbicide

Tebuthiuron 0.016 μg/L Irl Herbicide

Terbacil 0.034 μg/L Irl Herbicide

Terbufos 0.017 μg/L Irl Insecticide

Thiobencarb 0.005 μg/L Irl Herbicide

Tri-allate 0.002 μg/L Irl Herbicide

Trifluralin 0.009 μg/L Irl Herbicide

Table 4. Pesticides and reporting levels as of 2003, U.S. Geological Survey National Water Quality Laboratory Schedule 2001—Continued

[method reference: Zaugg and others (1995); μg/L, micrograms per liter; Irl, interim reporting level; Mrl, minimum reporting level]

Pesticide Reporting levels Unit Reporting

level type Use
12 Water Quality and Possible Sources of Nitrate in the Cimarron Terrace Aquifer, Oklahoma, 2003

 Table 5. Wastewater compounds and minimum reporting levels as of 2003, U.S. Geological Survey National Water Quality Laboratory

custom lab code 8033

[method reference: Steven Zaugg, U.S. Geological Survey, written commun., 2003; μg/L, micrograms per liter; %, percent; >, greater than; UV, ultraviolet]

Wastewater compounds Minimum

reporting level Unit Effluentcategories Use

1,4-Dichlorobenzene 0.5 μg/L Household Moth repellent, fumigant, deodorant

17-beta-Estradiol 5 μg/L Animal Estrogen replacement therapy, estrogen metabolite

1-Methylnaphthalene 0.5 μg/L Hydrocarbon 2-5% of gasoline, diesel fuel, or crude oil

2,6-Dimethylnaphthalene 0.5 μg/L Hydrocarbon Present in diesel/kerosene (trace in gasoline)

2-Methylnaphthalene 0.5 μg/L Hydrocarbon 2-5% of gasoline, diesel fuel, or crude oil

3,4-dichlorophenyl isocyanate 1 μg/L Industrial Dyes

3-beta-Coprostanol 2 μg/L Animal Carnivore fecal indicator

3-tert-butyl-4-hydroxy anisole

(BHA)

5 μg/L Household Antioxidant, general preservative

4-Cumylphenol 1 μg/L Detergent Nonionic detergent metabolite

4-n-Octylphenol 1 μg/L Detergent Nonionic detergent metabolite

4-tert-Octylphenol 1 μg/L Detergent Nonionic detergent metabolite

5-Methyl-1H-benzotriazole 2 μg/L Industrial Antioxidant in antifreeze and deicers

Acetophenone 0.5 μg/L Household Fragrance in detergent and tobacco, flavor in beverages

Acetyl hexamethyl tetrahydronaphthalene (AHTN)0.5 μg/L Household Musk fragrance

Anthracene 0.5 μg/L Hydrocarbon Wood preservative, component of tar, diesel, or

crude oil

Anthraquinone 0.5 μg/L Household Manufacture dye/textiles, seed treatment, bird repellent

Benzo[a]pyrene 0.5 μg/L Household Used in cancer research

Benzophenone 0.5 μg/L Household Fixative for perfumes and soaps

Beta-Sitosterol 2 μg/L Animal Plant sterol

beta-Stigmastanol 2 μg/L Animal Plant sterol

Bisphenol A 1 μg/L Household Plasticizer, resin

Bromacil 0.5 μg/L Pesticide Herbicide, >80% noncrop usage on grass/brush

Bromoform 0.5 μg/L Household Ozonation byproduct, military/explosives

Caffeine 0.5 μg/L Household Beverages, diuretic

Camphor 0.5 μg/L Household Flavor, odorants, ointments

Carbaryl 1 μg/L Pesticide Insecticide, crop and garden usage

Carbazole 0.5 μg/L Household Manufacture dyes, explosives, and lubricants
Methods 13

Chlorpyrifos 0.5 μg/L Pesticide Insecticide, domestic pest and termite control

Cholesterol 2 μg/L Animal Fecal indicator and plant sterol

Cotinine 1 μg/L Household Primary nicotine metabolite

Diazinon 0.5 μg/L Pesticide Insecticide, > 40% nonagricultural usage, ants, flies

d-Limonene 0.5 μg/L Household Fungicide, antimicrobial, antiviral, fragrance in aerosols

Dichlorovs 1 μg/L Pesticide Insecticide, pet collars, flies

Diethylhexyl phthalate 0.5 μg/L Household Celluloid, cosmetics, varnishes, and dopes. Plasticizer for cellulose ester plastics. Insecticide sprays

Equilenin 5 μg/L Animal Hormone replacement drug therapy

Estrone 5 μg/L Animal Biogenic hormone

Ethanol-2-butoxy-phosphate 0.5 μg/L Household Plasticizers

Ethynyl estradiol 5 μg/L Animal Oral contraceptive

Fluoranthene 0.5 μg/L Hydrocarbon Component of coal tar and asphalt

Galaxolide 0.5 μg/L Household Musk Fragance

Hexahydro hexamethyl cyclopenta benzopyran (HHCB)0.5 μg/L Household Musk fragrance

Indole 0.5 μg/L Household Pesticide inert ingredient, fragrance in coffee

Isoborneol 0.5 μg/L Household Fragrance in perfumery, in disinfectants

Isophorone 0.5 μg/L Industrial Solvent for lacquer, plastic, oil, silicon, resin

Isopropylbenzene 0.5 μg/L Industrial Manufacture phenol/acetone, fuels and paint thinner

Isoquinoline 0.5 μg/L Household Flavors and fragrances

Menthol 0.5 μg/L Household Cigarettes, cough drops, liniment, mouthwash

Metalaxyl 0.5 μg/L Pesticide Fungicide, mildew, blight, pathogens, golf/turf

Methyl salicylate 0.5 μg/L Household Liniment, food, beverage, UV-absorbing lotion

Metolachlor 0.5 μg/L Pesticide Herbicide

N,N-diethyl-meta-toluamide

(DEET)

0.5 μg/L Pesticide Insecticide, mosquito repellent, urban usage

Naphthalene 0.5 μg/L Hydrocarbon Fumigant, major component (about 10%) of gasoline

Nonylphenol, diethoxy (total) 5 μg/L Detergent Nonionic detergent metabolite

Octylphenol, diethoxy 1 μg/L Detergent Nonionic detergent metabolite

Octylphenol, monoethoxy 1 μg/L Detergent Nonionic detergent metabolite

 Table 5. Wastewater compounds and minimum reporting levels as of 2003, U.S. Geological Survey National Water Quality Laboratory

custom lab code 8033—Continued

[method reference: Steven Zaugg, U.S. Geological Survey, written commun., 2003; μg/L, micrograms per liter; %, percent; >, greater than; UV, ultraviolet]

Wastewater compounds Minimum

reporting level Unit Effluentcategories Use
14 Water Quality and Possible Sources of Nitrate in the Cimarron Terrace Aquifer, Oklahoma, 2003

para-Nonylphenol (total) 5 μg/L Detergent Nonionic detergent metabolite

p-Cresol 1 μg/L Industrial Wood preservative

Pentachlorophenol 2 μg/L Pesticide Herbicide, fungicide, wood preservative, termite

control

Phenanthrene 0.5 μg/L Hydrocarbon Manufacture explosives, component of tar, diesel

fuel, or crude oil

Phenol 0.5 μg/L Household Disinfectant, manufacture several products, leachate

Prometon 0.5 μg/L Pesticide Herbicide, noncrop usage, applied prior to blacktop

Pyrene 0.5 μg/L Hydrocarbon Component of coal tar and asphalt

Skatole (3-Methyl-1(H)-indole) 1 μg/L Animal Fragrance, stench in feces and coal tar

Tetrachloroethylene 0.5 μg/L Industrial Solvent, degreaser, veterinary anthelmintic

Tonalide 0.5 μg/L Household Musk Fragance

Tri(2-butoxyethyl)phosphate 0.5 μg/L Household Flame retardant

Tri(2-chloroethyl)phosphate 0.5 μg/L Household Plasticizer, flame retardant

Tributylphosphate 0.5 μg/L Detergent Antifoaming agent, flame retardant

Triclosan 1 μg/L Household Disinfectant, antimicrobial

Triethyl citrate (ethyl citrate) 0.5 μg/L Household Cosmetics, pharmaceuticals

Triphenyl phosphate 0.5 μg/L Industrial Plasticizer, resin, wax, finish, roofing paper, flame

retardant

Tris(dichlorisopropyl)-

phosphate

0.5 μg/L Household Flame retardant

 Table 5. Wastewater compounds and minimum reporting levels as of 2003, U.S. Geological Survey National Water Quality Laboratory

custom lab code 8033—Continued

[method reference: Steven Zaugg, U.S. Geological Survey, written commun., 2003; μg/L, micrograms per liter; %, percent; >, greater than; UV, ultraviolet]

Wastewater compounds Minimum

reporting level Unit Effluentcategories Use

Statistical Analysis

Several tabular, graphical, and other statistical approaches

were used to summarize and analyze water-quality data collected for this study. Water-quality data were analyzed as a single data set and data were analyzed by comparing data grouped

by two primary land-use categories, agricultural areas and

grassland areas. Summary statistics such as number of detections, minimum and maximum values, selected percentiles, and

median values are listed in tables and are referenced throughout

the report.

Cross-tabulations were constructed to form contingency

tables in order to measure the association between two nominal

categorical variables. The rows of the contingency table represent one variable, while the columns represent the second variable. Each variable has two possible responses which are listed

as counts in the contingency table. The null hypothesis is that

the two variables are independent and is tested using classical

Chi-Square techniques for independence (Helsel and Hirsch,

1992).

Graphical approaches including bar charts, box plots, bubble plots, frequency histograms, line plots, and pie charts were

used in this report to emphasis key results of this study. For a

complete description of the graphical approaches used in this

report, refer to Helsel and Hirsch (1992).

Spearmen's rho and Pearson's r correlation were used to

measure association between water-quality constituents. Correlation coefficients measure the strength of association between

two continuous variables. Correlation coefficients (designated

as cor.) are dimensionless and range from -1 to +1 (Helsel and
Water Quality in the Cimarron Terrace Aquifer 15

Hirsch, 1992). When there is no correlation between variables,

cor. = 0; when both variable increase, cor. is positive; and when

variables vary in opposite directions, cor. is negative (Helsel

and Hirsch, 1992). Spearmen's rho is a rank-based correlation

coefficient. Spearmen's rho is a non-linear measure of correlation and is less sensitive to outliers. Spearmen's rho was used if

data were not normally distributed as determined through

graphical techniques. Pearson's r is a measure of linear correlation between two variables and is sensitive to outliers and was

used if data followed a normal distribution.

The Wilcoxon rank-sum test was used to determine if differences existed between water-quality concentrations sampled

from two independent groups. The Wilcoxon rank-sum test is a

non-parametric test that measures the probability that two independent sample groups are similar in median or central value.

The null hypothesis is that there is no difference between

median values. The alternate hypothesis is that there is a difference between median values. The null hypothesis is rejected in

favor of the alternate hypothesis if the attained p-value from the

test is less than or equal to the α-level (significance level). An

α-value of 0.05 was used in this study. The α = 0.05 significance level is the probability (5 percent) that the null hypothesis

would incorrectly be rejected in favor of the alternate hypothesis. A p-value is the significance level attained by the data

(Helsel and Hirsch, 1992).

Water Quality in the Cimarron Terrace

Aquifer

This section describes the water quality of samples collected during July and August 2003, from 45 wells in the Cimarron terrace aquifer. Water properties, nutrients, nitrogen isotopes, pesticides, and wastewater compounds are described

independently in separate headings as listed in the “Groundwater sampling and analysis methods,” tables 3, 4, and 5.

Water-quality samples from agricultural areas were compared

with water-quality samples from grassland areas. Associations

between nitrate, pesticides, wastewater compounds, and other

factors such as water properties, site characteristics, and other

water-quality constituents also were evaluated and are

described if statistically significant.

Water Properties

Water properties such as specific conductance, pH, water

temperature, and dissolved oxygen are important supplemental

information which are measured in the field at the time of sampling. Certain water properties such as pH and dissolved oxygen can change rapidly with changes in temperature, atmospheric pressure, and exposure to sunlight. Field measurements

of pH and dissolved oxygen also can be useful in the preparation for laboratory analysis.

Specific conductance can be used as an indirect measurement of total dissolved solids in water (Hem, 1992). Specific

conductance measurements ranged from 289 to 2,118 microsiemens per centimeter at 25 degrees Celsius (μS/cm), with a

median value of 759 μS/cm (table 6). Ninety-one percent of the

specific conductance measurements ranged from 289 to 1,232

μS/cm (fig. 4). The four largest specific conductance measurements were from water samples collected in the northern part of

the Cimarron terrace aquifer from wells W42, W43, W44, and

W45 (fig. 3, Appendix 2).

 Table 6. Statistical summary of water properties in samples from 45 wells in the Cimarron terrace aquifer, July and August 2003

[μS/cm, microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter;  ̊C, degrees Celsius; --, pH mean not calculated]

Water properties Minimum Mean

 Concentration at indicated percentile

Maximum

25 50

(median) 75

Specific conductance (μS/cm) 289 819 607 759 938 2,118

pH (standard units) 6.1 -- 6.7 7.0 7.3 7.5

Water temperature ( ̊C) 16.0 17.2 17.0 17.2 17.6 18.9

Dissolved oxygen (mg/L) 0.2 3.9 2.0 3.2 5.7 9.4
16 Water Quality and Possible Sources of Nitrate in the Cimarron Terrace Aquifer, Oklahoma, 2003

0

500

1,000

1,500

2,000

SPECIFIC CONDUCTANCE, IN

MICROSIEMENS PER CENITMETER AT

25 DEGREES CELSIUS

45

2,250

0

2

4

6

8

10

DISSOLVED OXYGEN,

IN MILLIGRAMS PER LITER

44

6.4

6.8

7.2

7.6

45

pH, IN STANDARD UNITS

6.0

Median

Number of analyses

First observation less than or

equal to [ A + ( INT * 1.5 ) ]

EXPLANATION

75th percentile = (A)

Outlier

25th percentile = (B)

45

Secondary drinkingwater standard for pH

(U.S. Environmental Protection

Agency, 2002a)

Interquartile range (INT)

First observation greater than

or equal to [ B - ( INT * 1.5) ]

Tukey’s standard boxplot, described in

Helsel and Hirsch (1992, pg. 25)

TEMPERATURE, IN DEGREES CELSIUS

45

16.0

16.5

17.0

17.5

18.0

18.5

19.0

The pH measurements ranged from 6.1 to 7.5 standard

units, with a median value of 7.0 standard units (table 6, fig. 4).

The USEPA has established secondary drinking water standards for pH ranging from 6.5 to 8.5 standard units (U.S. Environmental Protection Agency, 2002a). The pH measurements at

wells W23, W33, W36, and W39 were less than 6.5 standard

units (Appendix 2).

Water temperature measurements ranged from 16.0 to 18.9

degrees Celsius, with a median value of 17.2 degrees Celsius

(fig. 4, Appendix 2). Dissolved oxygen (DO) concentrations

ranged from 0.2 to 9.4 mg/L, with a median concentration of 3.2

mg/L. Eighty-two percent of DO concentrations were greater

than 1.5 mg/L. All wells in the study area were generally shallow. Results from Spearman’s rho correlation test (Helsel and

Hirsch, 1992) indicated no significant correlation between DO

and well depths. DO is a controlling factor during the oxidation

of ammonia to nitrate and lack of DO may facilitate denitrification.

A Wilcoxon Rank-Sum test, comparing specific conductance measured in samples from wells located in agricultural

areas to specific conductance measured in samples from wells

located in grassland areas, indicated that specific conductance

was significantly greater in agricultural areas (z = 1.92, p-value

= 0.027) (fig. 5). The median specific conductance value mea-

 Figure 4. Distribution of water properties measured in samples from 45 wells in the Cimarron terrace aquifer, July and August 2003.
Water Quality in the Cimarron Terrace Aquifer 17

Median

Number of analyses

First observation less than or

equal to [ A + ( INT * 1.5 ) ]

EXPLANATION

75th percentile = (A)

Outlier

25th percentile = (B)

28

Interquartile range (INT)

First observation greater than

or equal to [ B - ( INT * 1.5) ]

Tukey’s standard boxplot, described in

Helsel and Hirsch (1992, pg. 25)

SPECIFIC CONDUCTANCE, IN

MICROSIEMENS PER CENTIMETER

AT

25 DEGREES CELSIUS

1,500

2,000

1,000

500

Agricultural

areas

Grassland

areas

2,250

17

28 Z = 1.92

p = 0.027 Z = Wilcoxon Rank Sum Statistic

p = p-value of test

sured in water from wells in agricultural areas was 833 μS/cm

(table 7), whereas, the median specific conductance value measured in water from wells in grassland areas was 675 μS/cm

(table 8). Comparisons of pH, water temperature, and DO measurements in grassland and agricultural areas did not indicate

significant differences in measured values.

Nutrients

Nutrients described in this report are species of nitrogen

and phosphorous. Nitrogen and phosphorous are chemical elements that are essential to plant and animal growth, but in large

concentrations are considered contaminants. Ground-water

samples collected were analyzed for nitrite, nitrate, ammonia,

ammonia plus organic nitrogen, phosphorus, and orthophosphate.

Nitrite is an unstable intermediate by-product of nitrification and denitrification. Nitrite concentrations in ground-water

samples were generally small. Nitrite concentrations were less

than the reporting level of 0.008 mg/L in 42 of the 45 groundwater samples. Nitrite concentrations ranged from E 0.005 to

0.046 mg/L (table 9, Appendix 3).

Nitrate concentrations in ground-water samples commonly are greater in agricultural areas than in areas of other

land uses (Mueller and Helsel, 1996). Nitrate is a very soluble

compound and is readily transported in the environment. Nitrate

concentrations greater than 3.0 mg/L in ground water are often

considered to result from human influence, such as fertilizer

applications on row crops or animal waste (Mueller and Helsel,

1996). An investigation using data from over 87,000 wells, collected over a 25-year period, indicated that nitrate concentrations less than 0.2 mg/L were representative of natural background concentrations (Madison and Brunett, 1984).

Concentrations of nitrate in ground water between 0.2 to 3.0

mg/L are considered transitional zones between background

and possible human influence (Madison and Brunett, 1984).

Nitrate concentrations in samples collected from background

wells were consistent with background concentrations reported

by Madison and Brunett, (1984), having no detectable nitrate in

W9 and 0.13 mg/L in W31 (Appendix 3).

Nitrate was detected in 44 of the 45 ground-water samples

and had the highest median concentration (8.03 mg/L) of any

nutrient analyzed (table 9). Nitrate concentrations ranged from

<0.06 to 31.8 mg/L (table 9, Appendix 3). Two samples had

nitrate concentrations less than 0.20 mg/L; 9 samples had

nitrate concentrations between 0.21 and 3.0 mg/L; and 17 samples had nitrate concentrations between 3.0 and 9.9 mg/L (fig.

6). Seventeen samples (38 percent) had nitrate concentrations

that exceeded the MCL of 10 mg/L of nitrate (fig. 6, fig. 7). The

10 highest nitrate concentrations occurred in samples from agricultural areas. Results from a Spearman’s Rank Correlation test

indicated that nitrate concentrations were not statistically correFigure 5. Distribution of specific conductance measured in water samples from 28 wells located in agricultural

areas and 17 wells located in grassland areas in the Cimarron terrace aquifer, July and August 2003.
18 Water Quality and Possible Sources of Nitrate in the Cimarron Terrace Aquifer, Oklahoma, 2003

 Table 7. Statistical summary of water properties in samples from 28 wells located in agricultural areas in the Cimarron terrace aquifer,

July and August 2003

[μS/cm, microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter;  ̊C, degrees Celsius; --, pH mean not calculated]

Water

properties Minimum Mean

Concentration at indicated percentile

Maximum

25 50

(median) 75

Specific conductance (μS/cm) 365 885 642 833 1,028 2,118

pH (standard units) 6.3 -- 6.7 6.9 7.2 7.5

Water temperature ( ̊C) 16.0 17.3 17 17.3 17.6 18.8

Dissolved oxygen (mg/L) 0.2 3.9 1.9 3.1 5.4 8.6

 Table 8. Statistical summary of water properties in samples from 17 wells located in grassland areas in the Cimarron terrace aquifer,

July and August 2003

[μS/cm, microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter;  ̊C, degrees Celsius; --, pH mean not calculated]

Water properties Minimum Mean

Concentration at indicated percentile

Maximum

25 50

(median) 75

Specific conductance (μS/cm) 289 709 576 675 763 1,770

pH (standard units) 6.1 -- 7.0 7.3 7.4 7.4

Water temperature ( ̊C) 16.0 16.9 16.5 17.0 17.3 18.0

Dissolved oxygen (mg/L) 0.2 3.9 2.8 3.3 5.7 9.4

 Table 9. Statistical summary of nutrient data for 45 ground-water samples collected in the Cimarron terrace aquifer, July and August

2003, (all units are in milligrams per liter)

[<, Less than; E, estimate]

Nutrient constituent Total number

of detections Minimum

Concentration at indicated percentiles

Maximum

10 25 50

(median) 75 90

Nitrite 3 E 0.005 <0.008 <0.008 <0.008 <0.008 <0.008 0.046

Nitrite plus nitrate as

nitrogen

44 <0.06 1.16 3.30 8.03 14.8 17.5 31.8

Ammonia 3 E 0.03 <0.04 <0.04 <0.04 <0.04 <0.04 0.70

Ammonia plus organic

nitrogen

33 E0.05 E 0.06 E 0.09 <0.10 0.10 0.20 0.88

Phosphorus 45 0.006 0.019 0.039 0.053 0.077 0.126 0.160

Orthophosphate 39 <0.02 0.02 0.03 0.04 0.07 0.12 0.15
Water Quality in the Cimarron Terrace Aquifer 19

NUMBER OF SAMPLES, IN DESIGNATED

CONCENTRATION RANGES

2

0

4

6

8

10

12

14

16

18

0 - 0.2 0.21 - 3.0 3.01 - 9.9 10.0 - 31.8

4%

20%

38%

38% = percent of samples

in designated concentration

range

DESIGNATED NITRATE CONCENTRATION RANGES

38%

lated with site characteristics such as well depth, depth to water,

distance from the Cimarron River, water properties, and other

water-quality variables.

Ammonia is a precursor to nitrate in oxidizing systems and

is readily used by crops and other plants. Commercial nitrogen

fertilizers are commonly applied as ammonia and animal

manure, which is converted to ammonia and ultimately converted to nitrate in the soil (Mueller and Helsel, 1996). Ammonia concentrations in most ground-water samples were low

(table 9, Appendix 3). Ammonia concentrations were less than

the reporting level of 0.04 mg/L in 42 of the 45 ground-water

samples. Ammonia concentrations ranged from E 0.03 to 0.70

mg/L. The maximum ammonia concentration occurred in a

sample from W38, which also had an elevated nitrate concentration (20.4 mg/L) (Appendix 3).

Ammonia plus organic nitrogen was detected in 33 of the

45 samples and ranged in concentration from E 0.05 to 0.88

mg/L. Thirty of the 33 samples (91 percent) with detectable

ammonia plus organic nitrogen consisted mostly of organic

nitrogen (Appendix 3). Organic forms of nitrogen may be considered indicators of contamination through disposal of sewage

or organic waste (Hem, 1992).

Phosphorus was detected in all 45 samples, with concentrations ranging from 0.006 to 0.160 mg/L (table 9). The median

phosphorus concentration was 0.053 mg/L. Phosphorus concentrations can be expected to be low in most ground-water

samples because of low solubility in water and tendency to sorb

to soil particles. Orthophosphate was detected in 39 of 45

ground-water samples and ranged in concentration from <0.02

to 0.15 mg/L, with a median concentration of 0.04 mg/L.

A Wilcoxon Rank-Sum test, comparing nitrate concentrations in agricultural areas to nitrate concentrations in grassland

areas, indicated that nitrate concentrations are significantly

greater in agricultural areas than in the grassland areas

(z = 3.557, p-value = <0.001) (fig. 8). Nitrate concentrations in

the agricultural areas ranged from 0.95 to 31.8 mg/L (table 10),

whereas, nitrate concentrations in the grassland areas ranged

from <0.06 to 14.9 mg/L (table 11). The median nitrate concentration in agricultural areas was 11.6 mg/L, whereas, the median

nitrate concentration in grassland areas was 3.63 mg/L. Nitrate

was the only nutrient with significant difference in concentration between samples from the agricultural and grassland areas.

 Figure 6. Number of samples in selected nitrate concentrations ranges.
W15 W7

W1

W2

W8

W4

W6 W5

W3

W9

W33

W41

W39 W40

W44

W36

W45

W42

W34

W28

W38

W32

W23

W25

W22

W37

W43

W29

W24

W10

W35

W30

W27

W19

W17

W13

W11

W16

W26

W21

W18

W14

W20

W31

W12

-99°

-99°

-98°30'

-98°30'

-98°

-98°

36°

36°30'

WOODWARD

WOODS

ALFALFA

GARFIELD

KINGFISHER

BLAINE

MAJOR

0 10 20 5 KILOMETE0 10 20 5 

NO2+NO3-N Concentration, in milligrams per liter

0 - 0.2 (2 wells)0.21 - 3.0 (9 wells)3.01 - 10.0 (17 wells)10.0 - 31.8 (17 wells)

Primary Land Use Category

AgricultureGrassland Cimarron Terrace Aquifer

EXPLANATION

County Boundary

Base data from Adams and others (1997), scale 1:100,000USGS Albers Equal Area Conic ProjectionNorth American Datum of 1983

 Figure 7. Location of wells and selected nitrate concentration ranges in samples from the Cimarron terrace aquifer, July and August 2003 (U.S

Survey, 2002).
Water Quality in the Cimarron Terrace Aquifer 21

 Table 10. Statistical summary of nutrient data collected in samples from 28 wells located in agricultural areas in the Cimarron terrace

aquifer, July and August 2003, (all units are in milligrams per liter)

[E, estimate; <, less than]

Nutrient constituent Number of

detections Minimum

Concentration at indicated percentiles

Maximum

10 25 50

(median) 75 90

Nitrite 2 E 0.005 <0.008 <0.008 <0.008 <0.008 <0.008 0.046

Nitrite plus nitrate as

nitrogen

28 0.95 2.42 6.02 11.6 15.8 20.4 31.8

Ammonia 1 <0.04 <0.04 <0.04 <0.04 <0.04 <0.04 0.70

Ammonia plus organic

nitrogen

21 E 0.06 E 0.08 E 0.10 <0.10 0.10 0.20 0.88

Phosphorus 28 0.006 0.010 0.038 0.054 0.110 0.140 0.160

Orthophosphate 23 <0.02 <0.02 0.03 0.04 0.09 0.12 0.15 NITRATE CONCENTRATION, IN MILLIGRAMS PER LITER

0

4

8

12

16

20

24

28

32

Median

Number of analyses

First observation less than or

equal to [ A + ( INT * 1.5 ) ]

EXPLANATION

75th percentile = (A)

Outlier

25th percentile = (B)

45

Primary drinking-water standard for

nitrate (U.S. Environmental Protection

Agency, 2002a)

Interquartile range (INT)

First observation greater than

or equal to [ B - ( INT * 1.5) ]

Tukey’s standard boxplot, described in

Helsel and Hirsch (1992, pg. 25)

Agricultural

areas

Grassland

areas

Z = Wilcoxon Rank Sum Statistic

p = p-value of test Z = 3.557

p =

28

17

<0.001

 Figure 8. Distribution of nitrate concentrations in samples from 28 wells located in agricultural areas and 17 wells located

in grassland areas in the Cimarron terrace aquifer, July and August 2003.
22 Water Quality and Possible Sources of Nitrate in the Cimarron Terrace Aquifer, Oklahoma, 2003

 Table 11. Statistical summary of nutrient data collected in samples from 17 wells located in grassland areas in the Cimarron terrace

aquifer, July and August 2003, (all units are in milligrams per liter)

[E, estimate; <, less than]

Nutrient constituent Number of

detections Minimum

Concentration at indicated percentiles

Maximum

10 25 50

(median) 75 90

Nitrite 3 <0.008 <0.008 <0.008 <0.008 <0.008 <0.008 0.020

Nitrite plus nitrate as

nitrogen

16 <0.06 0.27 2.19 3.63 6.14 8.35 14.9

Ammonia 2 E 0.03 <0.04 <0.04 <0.04 <0.04 <0.04 0.05

Ammonia plus organic

nitrogen

11 E 0.50 E 0.06 E 0.07 E 0.10 0.10 0.14 0.18

Phosphorus 17 0.014 0.030 0.040 0.048 0.062 0.070 0.099

Orthophosphate 16 <0.02 0.03 0.03 0.04 0.06 0.06 0.09

Nitrogen Isotopes

Nitrogen isotopes are commonly used as tracers to indicate

sources of nitrate (Kreitler, 1975 and 1979, Kreitler and Browning, 1983; and Wassenaar, 1995). There are many nitrogen isotopes, but only two are stable (non-radioactive), 14N and 15N.

The 14N isotope is the lighter of the two stable isotopes and

comprises 99.632 percent (plus or minus 0.002 percent) nitrogen in the atmosphere (Junk and Svec, 1958). The 15N isotope

is much less abundant than 14N and comprises 0.367 percent

nitrogen in the atmosphere (Neyens and others, 1999).

The ratios of 14N to 15N in a sample are compared to ratios

of 14N to 15N in atmospheric nitrogen, known as the reference

standard. Nitrogen isotope ratios are expressed as the isotopic

ratio delta value (δ) in parts per thousand, denoted as permil

(‰). The formula used to calculate nitrogen isotopic ratio deltas

is expressed in equation 1 (Kendall and Aravena, 1999):

 (1)

where

15N/ 14N = the ratio of the heavier, less abundant isotope to the lighter, more abundant isotope;

15N/14N sample = the collected sample; and

15N/14N standard = the internationally accepted standard gas,

atmospheric N2

(3.677 x 10-3, Clark and Fritz, 1997)

Nitrogen-isotope ratios in nitrate are controlled by biological, chemical, and physical processes that may cause preferential enrichment or depletion of one isotope relative to the other,

a process known as fractionation (Clark and Fritz, 1997). Samples enriched in 15N relative to atmospheric nitrogen have positive δ15N values, whereas, samples depleted in 15N relative to

atmospheric nitrogen will have negative δ15N values. Sufficient

fractionation may result in distinct isotopic compositions that

allow identification of nitrate sources in the environment (Clark

and Fritz, 1997).

Nitrogen in nitrate leached from animal waste, including

humans, is relatively enriched in 15N, with δ15N values ranging

from +10 to +20‰ (table 12). Increases in δ15N values from

animal waste are due to the excretion of the lighter 14N isotope,

volatilization of 15N-depleted ammonia, and oxidation of residual waste (Wolterink and others, 1979). Nitrate leached from

synthetic fertilizers have δ15N values ranging from –4 to +4‰

due to fixation of atmospheric N2 (table 12). Nitrate from synthetic fertilizers and precipitation have similar δ15N ranges due

to common exposure to atmospheric N2. Nitrate leached from

soils generally has δ15N values ranging from +2 to +10‰,

while nitrate leached from plants generally has δ15N values

ranging from –10 to + 10‰ (table 12). δ15N values in soils are

controlled by a wide range of soil factors, such as soil depth,

vegetation, soil use, and climate (Kendall, 1998). Plants can

have a wide range δ15N values due to the ability to utilize a variety of inorganic compounds (NH4, NO3, N2, and NO2) and

amino acids (Kendall, 1998).

The δ15N values were measured in water samples from 42

of 45 wells sampled in the Cimarron terrace aquifer (fig. 9,

δ N15

N15

N14--------sample

N15

N14--------s dard tan

= ---------------------------------- – 1 × 1 000 ,
Water Quality in the Cimarron Terrace Aquifer 23

 Table 12. Range of nitrogen isotope delta values (δ15N) in nitrate in water for selected sources of nitrate

Nitrogen isotope ratios δ15Ν ranges References

Animal (manure) and septic waste (human) +10 to +20‰ Kendall and Aravena (1999), Kreitler (1975)

Synthetic fertilizers –4 to +4‰ Kendall and Aravena (1999)

Soils +2 to +10‰ Kendall and Aravena (1999)

Plants –10 to +10‰ Clark and Fritz (1997)

Precipitation -8 to +4‰ Clark and Fritz (1997)

Appendix 4). δ15N values were not analyzed in water samples

from wells W9, W31, and W36, because nitrate concentrations

were less than the needed concentration (0.5 mg/L) to determine δ15N values. Measured δ15N values ranged from –0.83 to

10.1‰, with a median value of 4.28‰ and a mean of 4.59‰.

A complicating factor in using δ15N values alone to determine possible sources of nitrate is mixing of nitrogen from several sources such as manure or septic waste, the atmosphere,

fertilizers, plants, and soils. Mixing of several nitrogen sources

can cause isotopic ratios in water to resemble those of plants

and natural soils (fig. 9). δ15N values can be used with nitrate

concentrations, and detection of pesticides and wastewater

compounds to indicate possible sources of nitrate and are

described in the “Possible sources of nitrate” section.

Results from a Wilcoxon Rank-Sum test indicated that

δ15N values were significantly greater in samples from agricultural areas than in samples from grassland areas (z = 2.98, pvalue = 0.002) (fig. 10). The median δ15N value in the agricultural areas was 5.15‰, whereas the median δ15N value in the

grassland areas was 2.36‰ (table 13). This difference was

unexpected because low δ15N values and greater nitrate concentrations are commonly associated with agricultural areas

where fertilizers are applied to soils. An investigation in the

Central High Plains aquifer showed that anthropogenic compounds including pesticides tend to be detected twice as often

in public-water supply wells than in domestic wells due to

altered flow paths and recharge rates (Bruce and Oelsner,

2001). A Wilcoxon Rank-Sum test was done to see if δ15N values were significantly greater in samples from public-water

supply wells than in samples from domestic wells and results

indicated no significant difference (z = 1.03, p-value = 0.154).

The reason for δ15N values being greater in agricultural areas

than in grassland areas is not understood.

Pesticides

Synthetic pesticides are organic compounds that are not

naturally present in water and are used to control unwanted

plants or animals (Ware, 1989). Two common characteristics

associated with the mobility and ultimately the presence of pesticides in ground water are the aqueous solubility and partition

coefficient between a contaminant and natural organic matter

(Koc) (Bedient and others, 1997). Aqueous solubility quantifies

the amount of a particular compound that will dissolve in a

known volume of water. Compounds with greater aqueous solubility have a greater likelihood of moving in the environment.

The Koc is a measure of the tendency for a compound to adsorb

to soil particles or partition into soil organic matter. The smaller

the Koc, the weaker the potential for a compound to adsorb to

soil particles or partition into soil organic matter, resulting in

greater mobility in the environment.

Each of the samples collected from 45 ground-water wells

sampled in the Cimarron terrace aquifer was analyzed for 52

commonly applied pesticide compounds (table 4). Pesticides

were detected in samples from 15 of 45 (33 percent) wells (fig.

11, Appendix 5).

Five pesticides and 1 metabolite of the 52 pesticides that

were analyzed in each sample were detected, (table 14, Appendix 5). Atrazine and deethylatrazine, a metabolite of atrazine,

were the most frequently detected. Deethylatrazine was

detected in water samples from 9 of the 15 wells with pesticide

detections (table 14). Atrazine was detected in water samples

from 8 of 15 wells. Atrazine is a triazine herbicide that disrupts

photosynthesis in selected plants, and is commonly applied to

kill weeds in corn, sorghum, wheat, hay, sod, and turf grasses

(Thelin and Gianessi, 2000). Atrazine was the second most frequently detected pesticide in USEPA National Survey of Pesticides in Drinking Water Wells (U.S. Environmental Protection

Agency, 2002b). Based on an aqueous solubility of 30 mg/L at

20 degrees Celsius and a Koc of 122, atrazine is considered to

have a moderate mobility rating (U.S. Environmental Protection Agency, 2002b). Atrazine may potentially cause a variety

of health effects from exposures at concentrations above the

MCL of 3 micrograms per liter (μg/L) (U.S. Environmental

Protection Agency, 2002a). Although atrazine was detected in

water samples from 8 of the 15 wells, concentrations were less
24 Water Quality and Possible Sources of Nitrate in the Cimarron Terrace Aquifer, Oklahoma, 2003

0 5 10 15

δ

15N, IN PARTS PER THOUSAND

W1

W2

W3

W4

W5

W6

W7

W8

W10

W11

W12

W13

W14

W15

W16

W17

W18

W19

W20

W21

W22

W23

W24

W25

W26

W27

W28

W29

W30

W31

W32

W33

W34

W35

W36

W37

W38

W39

W40

W41

W42

W43

W44

W45

-4

Plants

Synthetic fertilizer

Precipitation

Soils

Septic or manure waste

20

WELLS SAMPLED IN THE CIMARRON TERRACE AQUIFER, JULY AND AUGUST 2003

0.95

2.48

8.03

15.4

2.53

2.20

1.24

2.27

1.11

3.68

15.6

6.03

14.9

8.35

11.2

16.4

9.01

10.1

17.9

5.99

11.9

21.3

15.3

5.83

6.93

6.14

16.8

2.19

3.63

3.30

8.48

20.4

4.38

31.8

4.11

14.4

20.5

8.36

4.21

14.8

12.3

9.37

W9 *

*

*

Nitrate concentration

in milligrams per liter

* N value not determined,

nitrate concentration too

small for

δ

δ N analysis

15

15

EXPLANATION

3.68

Agriculture site

Grassland site

Figure 9. Nitrogen isotope delta values (δ15N) in nitrate measured in samples from 42 of 45 wells in the Cimarron terrace aquifer, July and

August 2003. Shown with nitrate concentrations and δ15N ranges for major sources of nitrate in the hydrosphere (based on Kreitler, 1975;

Clark and Fritz, 1997; and Kendall and Aravena, 1999).
Water Quality in the Cimarron Terrace Aquifer 25

 Table 13. Statistical summary of nitrogen delta values (δ15N) in nitrate measured in samples from 28 wells in agricultural areas and 14 of 17 wells in

grassland areas in the Cimarron terrace aquifer, July and August 2003

Land use Minimum Mean 25th 50th

(median) 75th Maximum

Agriculture -0.83 5.38 3.19 5.15 7.72 10.1

Grassland 0.25 2.99 1.55 2.36 3.81 9.44

Median

Number of analyses

First observation less than or

equal to [ A + ( INT * 1.5 ) ]

EXPLANATION

75th percentile = (A)

Outlier

25th percentile = (B)

28

Interquartile range (INT)

First observation greater than

or equal to [ B - ( INT * 1.5) ]

Tukey’s standard boxplot, described in

Helsel and Hirsch (1992, pg. 25)

Z = Wilcoxon Rank Sum Statistic

p = p-value of test

Agricultural

areas

Grassland

areas

-1

0

1

2

3

4

5

6

7

8

9

10

11

12

-2

N, IN PARTS PER THOUSAND δδ15

z = 2.98

28 p = 0.002

14

 Figure 10. Nitrogen isotope delta values (δ15N) in nitrate measured in samples from 28 wells in agricultural areas and δ15N values from 14 of 17 wells in grassland areas in the Cimarron terrace aquifer, July and August 2003.
W15 W7

W1

W2

W8

W4

W6 W5

W3

W9

W33

W41

W39 W40

W44

W36

W45

W42

W34

W28

W38

W32

W23

W25

W22

W37

W43

W29

W24

W10

W35

W30

W27

W19

W17

W13

W11

W16

W26

W21

W18

W14

W20

W31

W12

-99°

-99°

-98°30'

-98°30'

-98°

-98°

36°

36°30'

WOODWARD 

WOODS

ALFALFA

GARFIELD

KINGFISHER

BLAINE

MAJOR

0 10 20 5 KILOMETER0 10 20 5 M

pesticide was detected (15 wells)pesticide was not detected (30 wells)

1 numbers in red bold are the number of pesticides detected

2

2

1

4

2

3 3

4

1

1

1

3 2

1

Primary Land Use Category

AgricultureGrassland Cimarron Terrace Aquifer

EXPLANATION

County Boundary

Base data from Adams and others (1997), scale 1:100,000USGS Albers Equal Area Conic ProjectionNorth American Datum of 1983

 Figure 11. Locations of wells with samples having detectable concentrations of pesticide compounds in the Cimarron terrace aquifer, July an
Water Quality in the Cimarron Terrace Aquifer 27

Table 14. Detected pesticide and metabolite compounds and range of concentrations in samples from 15 of 45 wells in the Cimarron terrace aquifer, July and August 2003

[E, estimate; μg/L, micrograms per liter]

Pesticides detected

Number of pesticides detected Range of

concentrations

(μg/L)

Use Agricultural

areas

Grassland areas Total

Alachlor 1 0 1 0.009 Herbicide

Atrazine 6 2 8 E 0.004 - 0.111 Herbicide

Deethylatrazine 6 3 9 E 0.007 - E 0.580 None (metabolite)

Metolachlor 4 0 4 E 0.011 - 0.092 Herbicide

Prometon 4 0 4 0.025 - 0.127 Herbicide

Tebuthiuron 2 3 5 E 0.010 - 0.159 Herbicide

than the MCL of 3 μg/L (fig. 12, Appendix 5).

Tebuthiuron was detected in water samples from 5 wells

(fig. 12, Appendix 5). Tebuthiuron is a herbicide used to control

weeds in non-cropland areas, rangelands, rights-of-way, and

industrial sites by disrupting the photosynthetic process (Ventures, Inc., 2003). Due to a large aqueous solubility of 2,500

mg/L at 25 degrees Celsius and low Koc of 80, tebuthiuron can

be very prevalent in the environment and is classified as very

mobile (U.S. Department of Agriculture, 1996). The USEPA

has not set a MCL for tebuthiuron, but has established a health

advisory for a lifetime consumption of 500 μg/L (U.S. Environmental Protection Agency, 2002a). The lifetime health advisory

is based on the concentration of a chemical in drinking water

that is not expected to cause any adverse non-carcinogenic or

carcinogenic effects for a lifetime exposure (based on 70 kilogram adult consuming 2 liters of water per day) (U.S. Environmental Protection Agency, 2002a). None of the detected tebuthiuron concentrations exceeded the USEPA lifetime health

advisory (fig. 12).

Metolachlor was detected in water samples from 4 wells

(fig. 12, Appendix 5). Metolachlor is a chloroacetanilide herbicide that acts as a growth inhibitor in selected plants, and is primarily used to kill weeds in corn, soybeans, peanuts, sorghum,

potatoes, and cotton (Thelin and Gianessi, 2000). Metolachlor

has an aqueous solubility of 530 mg/L at 20 degrees Celsius and

a Koc of 200, indicating that metolachlor has moderate to high

mobility and can potentially contaminate ground water (Rivard,

2003). The USEPA has not set a MCL for metolachlor, but has

established a health advisory concentration for a lifetime exposure greater than 100 μg/L (U.S. Environmental Protection

Agency, 2002a). None of the detected metolachlor concentrations exceeded the USEPA lifetime health advisory level (fig.

12).

Prometon was detected in water samples from 4 wells (fig.

12, Appendix 5). Like tebuthiuron, prometon is a herbicide that

is used to control broadleaf weeds in non-cropland areas, rangelands, rights-of-way, industrial sites, and recreational areas by

disrupting the photosynthetic process (Ventures, Inc., 2003).

Prometon can be very persistent in the environment due to a

half-life in soil of 500 days. Prometon has an aqueous solubility

of 700 mg/L at 22 degrees Celsius (AERVOE, 2003) and a Koc

of 150. It is rated as having very high mobility (Kerle and others, 1996). The USEPA has not set a MCL for prometon, but has

established a health advisory level of 500 μg/L (U.S. Environmental Protection Agency, 2002a). None of the detected prometon concentrations exceeded the USEPA lifetime health advisory level (fig. 12).

Alachlor was only detected in a water sample from 1 well

(fig. 12, Appendix 5). Alachlor is a pre-emergent herbicide used

to control grasses and weeds in cropland areas such as corn, sorghum, soybeans, peanuts, and cotton. Like the other pesticides

detected, alachlor has a moderate to high mobility rating due to

an aqueous solubility of 140 mg/L and an average Koc value of

155 (U.S. Environmental Protection Agency, 2002c). Alachlor

may cause a variety of health effects from long-term exposure

at concentrations exceeding the MCL of 2 μg/L for alachlor

(U.S. Environmental Protection Agency, 2002a). The concentration of alachlor detected in water from the single well was

less than the MCL of 2 μg/L (fig. 12).
28 Water Quality and Possible Sources of Nitrate in the Cimarron Terrace Aquifer, Oklahoma, 2003

Estimated concentration

Measured concentration

Maximum contaminant

level (MCL) (U.S. Environmental

Protection Agency, 2002a)

Alachlor Atrazine Deethylatrazine

(metabolite)

Metolachlor Prometon Tebuthiuron

DETECTED PESTICIDE COMPOUNDS

0.001

2

3

4

5

6

8

2

3

4

5

6

8

2

3

4

5

6

8

2

3 (1) (9) (4) (4) (5) (8)

(2) Number of pesticides detected

0.01

0.1

1

PESTICIDE CONCENTRATIONS, IN

MICROGRAMS PER LITER

Results from contingency tables indicated that the number

of pesticide detections were not statistically different between

wells sampled in agricultural areas and wells sampled in grassland areas (Chi squared = 0.189, p-value = 0.664) (Helsel and

Hirsch, 1992). Pesticide concentrations were not significantly

correlated to nitrate and phosphorus concentrations, nor were

pesticide concentrations significantly correlated to well depth

or any other site characteristics.

Wastewater Compounds

Wastewater compounds in this report refer to a wide range

of organic chemicals that are commonly associated with domestic and industrial wastewater effluent. The wastewater compounds can be grouped into six categories: (1) animal, (2) detergent, (3) household, (4) hydrocarbon, (5) industrial, and (6)

pesticide (table 5).

Each of the samples from the 45 ground-water wells in the

Cimarron terrace aquifer was analyzed for 72 wastewater compounds (table 5). Wastewater compounds were detected in

water samples from 28 of 45 wells (62 percent) (fig. 13, Appendix 6). Twenty of the 72 wastewater compounds were detected.

Of the 20 wastewater compounds detected, 11 compounds (55

percent) were in the household category, 3 compounds (15 percent) were in the hydrocarbon category, 2 compounds (10 percent) were in the industrial category, 2 compounds (10 percent)

were in the pesticides category, 1 compound (5 percent) was in

the animal category, and 1 compound (5 percent) was in the

detergent category (fig. 14, table 15).

Wastewater compounds in the household category (fig.

15) are commonly used in products such as perfumes, coffee,

soaps, dyes, flame retardant products, lubricants, and disinfectants (table 5). Fluoranthene, phenanthrene, and pyrene were in

the hydrocarbon category and are commonly used in asphalt,

diesel fuel, crude oil, and tar products. P-cresol and triphenyl

Figure 12. Distribution of pesticide and metabolite compounds detected in samples from 15 of 45 wells in the Cimarron terrace aquifer,

July and August 2003.
W15

W7

W1

W2

W8

W4

W6 W5

W3

W9

W33

W41

W39 W40

W44

W36

W45

W42

W34

W28

W38

W32

W23

W25

W22

W37

W43

W29

W24

W10

W35

W30

W27

W19

W17

W13

W11

W16

W26

W21

W18

W14

W20

W31

W12

-99°

-99°

-98°30'

-98°30'

-98°

-98°

36°

36°30'

WOODWARD

WOODS

ALFALFA

GARFIELD

KINGFISHER

BLAINE

MAJOR

0 10 20 5 KILOMETE0 10 20 5 

1

2

2

1

1

1

2

1

4

7

2

4

2

1

1

1

6

1

1

2

3

6 1

1

2

1

1

1

1

wastewater compound was detected (28 wells),

numbers in red bold are the number of compounds detected

wastewater compound was not detected (17 wells)

Primary Land Use Category

AgricultureGrassland Cimarron Terrace Aquifer

EXPLANATION

County Boundary

Base data from Adams and others (1997), scale 1:100,000USGS Albers Equal Area Conic ProjectionNorth American Datum of 1983

 Figure 13. Location of wells with samples having detectable concentrations of wastewater compounds in the Cimarron terrace aquifer, July and 
30 Water Quality and Possible Sources of Nitrate in the Cimarron Terrace Aquifer, Oklahoma, 2003

Household

55%

Hydrocarbon

15%

Industrial

10%

Pesticide

10%

Detergent

5%

Animal

5%

 Figure 14. Proportion of wastewater compounds detected in water samples for six selected wastewater-effluent categories.
Water Quality in the Cimarron Terrace Aquifer 31

Table 15. Detected wastewater compounds and range of concentrations in samples from 28 of 45 wells sampled in the Cimarron terrace

aquifer, July and August 2003

[μg/L, micrograms per liter; E, estimate]

Wastewater compounds

detected

Number of wastewater compounds detected Range of

concentrations

(μg/L)

Effluent

Agricultural categories

 areas

Grassland

 areas

Total

Skatole (3-methyl-1h-indole) 1 0 1 E 0.83 Animal

Tributylphosphate 3 0 3 E 0.02 – E 0.03 Detergent

Anthraquinone 1 0 1 E 0.23 Household

Benzophenone 2 1 3 E 0.01 – E 0.02 Household

Benzo[a]pyrene 0 1 1 E 0.01 Household

Caffeine 1 0 1 E 0.02 Household

Carbazole 1 1 2 E 0.01 – E 0.11 Household

Diethylhexyl phthalate 2 0 2 1.10 – 1.5 Household

Ethanol-2-butoxy-phosphate 1 2 3 E 0.19 – E 0.82 Household

Indole 1 0 1 E 0.12 Household

Isoquinoline 1 0 1 0.04 Household

Methyl salicylate 0 1 1 E 0.02 Household

Phenol 15 8 23 E 0.20 – 5.0 Household

Fluoranthene 1 1 2 E 0.01 Hydrocarbon

Phenanthrene 1 1 2 E 0.01 – E 0.02 Hydrocarbon

Pyrene 1 1 2 E 0.01 Hydrocarbon

P-cresol 2 0 2 E 0.03 - 35.0 Industrial

Triphenyl phosphate 1 0 1 E 0.02 Industrial

Bromacil 1 1 2 E 0.10 - 1.7 Pesticide

N,N-diethyltoluamide (DEET) 4 1 5 E 0.03 – E 0.04 Pesticide
Caffeine

Carbozole

Benzophenone

Diethylhexyl phthalate

Ethanol,2-butoxy-

,phosphate

Indole

Isoquinoline

Methyl salicylate

Phenol

Household

Measured concentrationEstimated concentration

(3)

Pyrene

(2)

N,N-dieth

Fluoranthene

Hydrocarbon

Phenanthrene

(2)

Benzo[a]pyrene

(1) (2)

Indu

Triphenyl phosph

P-cresol

(2)

(3)

WASTEWATER COMPOUNDS

CONCENTRATION, IN MICROGRAMS PER LITER

682345682345682345682345

0.001

100

234568

0.01

0.1

1

10

Number of detections

(1) (2) (2) (3) (1) (1) (1) (23)

Animal categoryDetergent category

Anthraquinone

Skatole (3-methyl-1h-indole)

(1)

Tributylphosphate

(3) (1)

 Figure 15. Wastewater compounds detected in samples from 28 of 45 wells in the Cimarron terrace aquifer, July and August 2003.
Possible Sources of Nitrate 33

phosphate were the compounds detected from the industrial category and are commonly used in wood preservation and flame

retardant products. Bromacil and N,N-diethyl-meta-toluamide

(DEET) were the compounds detected in the pesticides category. Bromacil is a herbicide that is used for brush and weed

control in non-cropland areas. DEET is a common insecticide

used to control ticks, chiggers, and mosquitoes. Skatole (3-

methyl-1h-indole) was the compound detected from the animal

category and is commonly found in feces. Tributylphosphate

was the compound detected from the detergent category and is

a common anti-foaming agent and flame retardant.

The most frequently detected wastewater compound was

phenol. It was detected in water samples from 23 wells and

ranged from E0.20 to 5.0 μg/L (fig. 15, table 15, Appendix 6).

DEET was the second most frequently detected wastewater

compound. DEET was detected in 5 wells and ranged from

E0.03 to E0.04 μg/L. Benzophenone, ethanol-2-butoxy-phosphate, and tributylphosphate each were detected in 3 wells,

ranging from E0.01 to E0.02, E0.19 to E0.82, and E0.02 to

E0.03 μg/L, respectively. A sample from W38 had the greatest

p-cresol and phenol concentrations, with 35.0 μg/L and 5.0

μg/L.

The greatest number of wastewater compounds detected in

a single sample was from well W38, with 7 detections (Appendix 6). Six wastewater compounds were detected in water samples from wells W1 and W36. Water samples from wells W8

and W45 each had 4 wastewater compounds detected. Water

samples from the remaining 23 wells had 3 or fewer wastewater

compounds detected.

Results from contingency tables indicate that the number

of wastewater compounds detected were not statistically different between wells sampled in agricultural areas and wells sampled in grassland areas (Chi squared = 0.134, p-value = 0.714)

(Helsel and Hirsch, 1992). Concentrations of wastewater compounds were not significantly correlated with nitrate and phosphorus concentrations, nor were they significantly correlated to

well depth or any other site characteristics.

Possible Sources of Nitrate

Nitrogen isotope ratios in nitrate are a common tool for

determining the sources of nitrate in water (Kreitler, 1975 and

1989; Kreitler and Browning, 1983; and Wassenaar, 1995).

Denitrification is a complicating factor that can limit the use of

nitrogen isotopes to determine sources of nitrate. Denitrification causes δ15N values to increase substantially as nitrate concentrations decrease (Kendall, 1998). Denitrification is a process in which bacteria or inorganic substrates can convert

nitrate to nitrous oxide or nitrogen gas (Madison and Brunett,

1984). A second complicating factor can occur when mixing of

nitrogen occurs from several sources such as manure or septic

waste, the atmosphere, fertilizers, plants, and soils. Denitrification and mixing of several nitrogen sources can cause isotopic

ratios to resemble those of plants and natural soils. Nitrate from

synthetic fertilizers and precipitation have similar δ15N ranges

because of common exposure to atmospheric nitrogen (table

12), but nitrate concentrations in precipitation were much less

than nitrate concentrations in ground-water samples collected

for this study. The annual precipitated-weighted mean nitrate

concentration in northwest Oklahoma for 2002 was 1.34 mg/L

(National Atmospheric Deposition Program, 2002).

Using multiple lines of evidence from chemical analysis in

conjunction with nitrogen isotopes may assist in determining

possible nitrate sources. The methods used to determine the

possible nitrate sources are based on nitrate source criteria

developed using nitrate concentrations, nitrogen-isotope ratios,

detection of pesticides, and detection of wastewater compounds. Pesticides and wastewater compounds were used as

indicators of fertilizer application or septic or manure waste.

Using these diagnostic tools, individual wells were grouped into

four possible nitrate source (PNS) categories: (PNS -1) synthetic fertilizer source; (PNS -2) mixed sources (combination of

synthetic fertilizer, septic or manure waste, or natural sources);

(PNS -3) septic or manure source; and (PNS -4) natural source

(plant, soil, or precipitation) (table 16).

There are four main components of how the nitrate source

criteria were determined: (1) a nitrate concentration of 3.0

mg/L is used to help determine if nitrate could be from natural

sources or the result of human or animal influence; (2) the use

of published nitrogen isotopic delta values; (3) indication that

synthetic fertilizer could be or is contributing to nitrate concentrations by the detection of one or more pesticides; and (4) the

indication that septic or manure waste could be or is contributing to nitrate concentrations by the detection of two or more

wastewater compounds detected. Due to very low concentrations and the likelihood of a few of the compounds included in

the wastewater schedule (table 5) to occur naturally in the environment, at least two wastewater compounds had to be detected

before septic or manure could be considered a possible source

of nitrate. The pesticides used as indicators of fertilizer application do not occur naturally and, therefore, only one pesticide

had to be detected before synthetic fertilizer could be considered a possible source of nitrate.

Two sets of criteria, Criteria 1 and Criteria 2, were developed by combining nitrate concentrations, nitrogen isotopic

delta values, detection of pesticides, or detection of wastewater

compounds (table 16). Criteria 1 overrides Criteria 2. If conditions in Criteria 1 were not met, then the determination of the

possible source of nitrate was based on Criteria 2. If δ15N values could not be determined because of nitrate concentrations

being too low, the possible nitrate source was considered to be

from natural sources.

Synthetic fertilizer was the possible source of nitrate for 13

of 45 wells sampled in the Cimarron terrace aquifer (fig. 16 and

17, table 17). δ15N values in the synthetic fertilizer category

ranged from 0.43 to 3.46‰ (table 18). The nitrate source category with the greatest number of wells (22 wells) was in the

mixed sources category. δ15N values in the mixed sources category ranged from 0.25 to 9.83‰. Two wells (W36 and W43)
34 Water Quality and Possible Sources of Nitrate in the Cimarron Terrace Aquifer, Oklahoma, 2003

Table 16. Description of nitrate source categories used to determine possible sources of nitrate, based on nitrate concentrations, nitrogen isotope delta values (δ15N) in nitrate, and detection of pesticides and wastewater compounds

[<, less than; , ≥ greater than or equal to; ≤, less than or equal to; PNS, possible nitrate sources; ID, identification number; mg/L, milligrams per liter; δ15N, nitrogen isotope delta value; ‰, permil]

PNS ID Nitrate source categories 1Criteria 1 for nitrate source categories

1

Criteria 1 overrides Criteria 2.

2

Criteria 2 for nitrate source

categories

2

Nitrate concentration based on Mueller and Helsel (1996) and Madison and Brunett (1984), δ15N values based on table 12.

PNS-1 Synthetic fertilizer source One or more pesticides detected and < 2 wastewater

compounds detected and -4‰ < δ15N < +4‰

Nitrate ≥ 3.0 mg/L, and -4‰ <

δ15N < +4‰

PNS-2 Mixed, combination of synthetic fertilizer, septic or

manure waste, or natural

sources

 One or more pesticides detected and 2 or more household wastewater compounds detected; or Two or more

wastewater compounds detected and

0‰ ≤ δ15N < +10‰

Nitrate ≥ 3.0 mg/L and, +4‰ ≤

δ15N < +10‰

PNS-3 Septic or manure sources Nitrate < 3.0 mg/L and 2 or more wastewater compounds detectedNitrate ≥ 3.0 mg/L and, +10‰

≤ δ15N ≤ +20‰

PNS-4 Natural sources (plant, soil,

or precipitation)

Nitrate < 3.0 mg/L, and -10‰ < δ15N < +10‰ Nitrate < 3.0 mg/L

had possible septic or manure source as the possible source of

nitrate. A δ15N value was not analyzed in water samples from

well W36, because the nitrate concentration was less than the

needed concentration (0.5 mg/L) for δ15N analysis. Natural

sources were the possible source of nitrate for 7 wells. The natural sources category had the greatest range of δ15N values

(table 17), ranging from -0.83 to 9.44‰.

Of the 28 wells in the agricultural areas, 5 wells (18 percent) were in the synthetic fertilizer category, 18 wells (64 percent) were in the mixed sources category, 1 well (4 percent) was

in the septic or manure source category, and 4 wells (14 percent)

were in the natural sources category (fig. 18). Of the 17 wells in

the grassland areas, the possible sources of nitrate were determined for 16 wells. Eight wells (50 percent) were in the synthetic fertilizer category, 4 wells (25 percent) were in the mixed

sources category, 1 well (6 percent) was in septic or manure

sources category, and 3 wells (19 percent) were in the natural

sources category (fig. 18).

Summary

Water in the Cimarron terrace aquifer in northwestern

Oklahoma commonly has nitrate concentrations that exceed the

maximum contaminant level (MCL) of 10 milligrams per liter

(mg/L) of nitrite plus nitrate as nitrogen (referred to as nitrate)

set by the U.S. Environmental Protection Agency for public

drinking water.

Starting in July 2003, the U.S. Geological Survey, in cooperation with the Oklahoma Department of Environmental Quality, conducted a study in the Cimarron terrace aquifer to assess

the occurrence and distribution of nitrate, pesticides, and wastewater compounds from land-use activities and to determine

possible sources of nitrate. A quantitative and qualitative

approach based on multiple lines of evidence from chemical

analysis of nitrate, nitrogen isotopes in nitrate, commonly

applied pesticides (indicative of fertilizer application), and
Summary 35

0 5 10 15

δ

15N, IN PARTS PER THOUSAND

W1

W2

W3

W4

W5

W6

W7

W8

W10

W11

W12

W13

W14

W15

W16

W17

W18

W19

W20

W21

W22

W23

W24

W25

W26

W27

W28

W29

W30

W31

W32

W33

W34

W35

W36

W37

W38

W39

W40

W41

W42

W43

W44

W45

-4

Plants

Synthetic fertilizer

Precipitation

Soils

Septic or manure waste

20

WELLS SAMPLED IN THE CIMARRON TERRACE AQUIFER, JULY AND AUGUST 2003

0.95

2.48

8.03

15.4

2.53

2.20

1.24

2.27

1.11

3.68

15.6

6.03

14.9

8.35

11.2

16.4

9.01

10.1

17.9

5.99

11.9

21.3

15.3

5.83

6.93

6.14

16.8

2.19

3.63

3.30

8.48

20.4

4.38

31.8

4.11

14.4

20.5

8.36

4.21

14.8

12.3

9.37

W9 *

*

*

Number corresponds to nitrate

concentration, in milligrams per liter

EXPLANATION

Agriculture site

Grassland site

Colors indicate possible nitrate

sources based on Table 16

* δ

δ

N15 value not determined,

nitrate concentrations too

small for N anlaysis 15

W9 Source not determined, no

nitrate detected

W31 Natural source

W36 Septic/Manure source

4.38 Synthetic fertilizer source

(PNS-1)

Natural source (atmosphere,

plants, or soils) (PNS-4)

2.27

Mixed sources, includes

fertilizer, septic/manure,

or natural sources (PNS-2)

6.93

5.99 Septic or manure

source (PNS-3)*

*

 Figure 16. Distribution of nitrogen isotope delta values (δ15N) in nitrate measured in samples, grouped by possible

sources of nitrate, from 42 of 45 wells in the Cimarron terrace aquifer, July and August 2003. Shown with nitrate concentrations and δ15N ranges for major sources of nitrate in the hydrosphere (based on Kreitler, 1975 and Kendall and Aravena, 1999).
36 Water Quality and Possible Sources of Nitrate in the Cimarron Terrace Aquifer, Oklahoma, 2003

Median

Number of analyses

First observation less than or

equal to [ A + ( INT * 1.5 ) ]

EXPLANATION

75th percentile = (A)

Outlier

25th percentile = (B)

28

Interquartile range (INT)

First observation greater than

or equal to [ B - ( INT * 1.5) ]

Tukey’s standard boxplot, described in

Helsel and Hirsch ( 1992, pg. 25)

NITRATE SOURCE CATEGORIES

Z = Wilcoxon Rank Sum Statistic

p = p-value of test

Single observation

Synthetic fertilizer (PNS-1)

Natural (PNS-4)

Mixed (PNS-2)

Septic/Manure (PNS-3)

N, IN PARTS PER THOUSAND

δ15

0

2

4

6

8

10

-1

1

3

5

7

9

11

W9, W31, and W36 are not reflected in

graph because nitrate concentrations were

too low for δ

15N analysis.

13 22 1 6

 Figure 17. Distribution of nitrogen isotope delta values (δ15N) in nitrate for selected nitrate source categories.
 Table 17. Number of detected pesticides and wastewater compounds, land-use categories, nitrate concentrations, nitrogen isotope delta values (δ15

sources of nitrate in water samples from the Cimarron terrace aquifer, July and August 2003

[ID, identification number; δ, isotope delta value; ‰, permil; mg/L, milligrams per liter; Syn., synthetic; n/a, nitrogen isotope delta value not measured because nitrate concentration needed for nitrogen isotope analysis; <, less than; -, non-detect]

Well

number Site ID

Detections

Land use Nitrate (mg/L) δ15N 

Wastewater compounds

Total Pesti- cides Animal Deter- gent House- hold Hydro- carbon Indus- trial

W1 355351097400301 6 1 - - 4 1 - Agriculture 9.37 2.6W2 355812097460001 2 - - - 2 - - Agriculture 12.3 3.1W3 355842097570001 1 - - - 1 - - Grassland 2.19 9.4W4 360004097523601 - - - - - - - Agriculture 14.8 2.3W5 360236097593501 3 2 - - 1 - - Agriculture 16.8 7.6W6 360300098044601 2 1 - - 1 - - Grassland 6.14 6.4W7 360451097534801 - - - - - - - Agriculture 10.1 5.7W8 360605098000401 4 1 - - 3 - - Agriculture 6.93 7.7W9 360653098085601 2 2 - - - - - Grassland <0.06 n/a W10 360726098040101 1 - - - 1 - - Agriculture 5.83 7.1W11 360851098023901 1 - - - 1 - - Agriculture 15.3 7.9W12 361005098072601 - - - - - - - Agriculture 9.01 4.8W13 361159098051501 - - - - - - - Agriculture 1.11 -0.8W14 361303098131501 1 1 - - - - - Grassland 4.21 1.4W15 361347098120901 2 1 - - 1 - - Agriculture 15.4 7.7W16 361454098142601 - - - - - - - Grassland 8.36 2.2W17 361712098103401 - - - - - - - Agriculture 21.3 8.5W18 361812098192101 4 3 - - 1 - - Agriculture 20.5 3.2
W19 361813098103201 - - - - - - - Agriculture 2.27 2.3W20 361850098145201 2 - - - 1 - 1 Agriculture 14.4 2.8W21 361939098215301 5 2 - - 3 - - Grassland 4.11 0.2W22 362146098215401 4 3 - - 1 - - Agriculture 16.4 5.1W23 362212098165201 3 3 - - - - - Agriculture 31.8 3.4W24 362233098243601 1 - - - 1 - - Grassland 8.03 3.0W25 362426098221001 5 4 - - 1 - - Agriculture 11.2 4.9W26 362435098282201 - - - - - - - Grassland 4.38 0.4W27 362530098355201 1 - - - 1 - - Grassland 8.35 4.0W28 362655098253101 1 1 - - - - - Agriculture 2.48 5.5W29 362657098203101 1 - - - 1 - - Agriculture 0.95 8.6W30 362800098383701 - - - - - - - Grassland 14.9 4.4W31 362842098482401 - - - - - - - Grassland 0.13 n/a W32 362939098225701 - - - - - - - Agriculture 6.03 4.9W33 363023098424801 1 - - - 1 - - Grassland 3.63 1.5W34 363113098315201 2 - - - 2 - - Agriculture 15.6 5.5W35 363211098392401 2 1 - - 1 - - Grassland 1.24 2.4W36 363330098470001 6 - - - 2 4 - Grassland 0.37 n/a W37 363348098325401 4 2 - - 2 - - Agriculture 3.68 5.1W38 363445098264001 7 - 1 1 4 - 1 Agriculture 20.4 2.4

 Table 17. Number of detected pesticides and wastewater compounds, land-use categories, nitrate concentrations, nitrogen isotope delta values (δ15

sources of nitrate in water samples from the Cimarron terrace aquifer, July and August 2003—Continued

[ID, identification number; δ, isotope delta value; ‰, permil; mg/L, milligrams per liter; Syn., synthetic; n/a, nitrogen isotope delta value not measured because nitrate concentration needed for nitrogen isotope analysis; <, less than; -, non-detect]

Well

number Site ID

Detections

Land use Nitrate (mg/L) δ15N 

Wastewater compounds

Total Pesti- cides Animal Deter- gent House- hold Hydro- carbon Indus- trial
W39 363452098384301 3 2 - - 1 - - Grassland 2.20 2.5W40 363510098514601 4 3 - - 1 - - Agriculture 8.48 3.4W41 363735098551801 - - - - - - - Grassland 2.53 1.8W42 363834098343801 - - - - - - - Agriculture 11.9 9.8W43 364519098311701 3 1 - - - 2 - Agriculture 5.99 10.1 W44 364258099000801 2 - - - 2 - - Grassland 3.30 1.6W45 364605098350001 4 1 - 1 2 - - Agriculture 17.9 8.6

 Table 17. Number of detected pesticides and wastewater compounds, land-use categories, nitrate concentrations, nitrogen isotope delta values (δ15

sources of nitrate in water samples from the Cimarron terrace aquifer, July and August 2003—Continued

[ID, identification number; δ, isotope delta value; ‰, permil; mg/L, milligrams per liter; Syn., synthetic; n/a, nitrogen isotope delta value not measured because nitrate concentration needed for nitrogen isotope analysis; <, less than; -, non-detect]

Well

number Site ID

Detections

Land use Nitrate (mg/L) δ15N 

Wastewater compounds

Total Pesti- cides Animal Deter- gent House- hold Hydro- carbon Indus- trial
40 Water Quality and Possible Sources of Nitrate in the Cimarron Terrace Aquifer, Oklahoma, 2003

Table 18. Statistical summary of nitrogen isotope delta values (δ15N) in nitrate, for selected nitrate source categories, from samples of 42 of 45 wells

in the Cimarron terrace aquifer, July and August 2003.

[PNS, possible nitrate sources; ID, identification number]

PNS

ID

Nitrate source

categories

1

Number of

wells in

category

1

δ15N value not determined for well (W9) because nitrate was not detected.

δ15N summary statistics, in permil

Maximum

Minimum Mean 25th 50th

(median) 75th

PNS-1 Synthetic fertilizer source13 0.43 2.35 1.61 2.43 3.05 3.46

PNS-2 Mixed source 22 0.25 5.69 4.59 5.30 7.68 9.83

PNS-3 Septic/Manure

source

2

(1)

2

δ15N value not determined for well (W36) because the nitrate concentration was too low for δ15N analysis. Nitrate source was determined using criteria 1.

10.1

PNS-4 Natural source 3

(6)

3

δ15N value not determined for well (W31) because the nitrate concentration was too low for δ15N analysis. Nitrate source was determined using only nitrate concentrations as described in criteria 2.

-0.83 4.48 1.97 3.92 7.83 9.44

NITRATE SOURCE CATEGORIES

Grassland areas

Agriculture areas

50 Percent of wells

Synthetic fertilizer (PNS-1)

Mixed (PNS-2)

Septic/Manure (PNS-3)

Natural (PNS-4)

0

2

4

6

8

10

12

14

16

18

20

NUMBER OF WELLS IN NITRATE

SOURCE CATEGORIES

18

50

25

64

4 6

14

19

 Figure 18. Number of wells located in agricultural and grassland areas for selected nitrate

source categories.
Summary 41

wastewater compounds (indicative of animal and human wastewater) was used to assess sources of nitrate contamination in the

Cimarron terrace aquifer.

Forty-five ground-water sampling locations were selected

randomly using a computerized stratified random selection

algorithm. Land-use information from the National Land Cover

Dataset (NLCD) was used to categorize the land use in the

Cimarron terrace aquifer into two general land-use categories,

agricultural areas and grassland areas.

Specific conductance measurements ranged from 289 to

2,118 microsiemens per centimeter at 25 degrees Celsius

(μS/cm), with a median concentration of 759 μS/cm. The pH

measurements ranged from 6.1 to 7.5, with a median value of

7.0. The USEPA has established secondary drinking water standards for pH ranging from 6.5 to 8.5. The pH measurements at

wells W23, W33, W36, and W39 were less than 6.5. Temperature measurements ranged from 16.0 to 18.9 degrees Celsius,

with a median value of 17.2 degrees Celsius. Dissolved oxygen

measurements ranged from 0.2 to 9.4 mg/L, with a median

value of 3.2 mg/L. Specific conductance measurements from

wells in agricultural areas were significantly greater than specific conductance measurements from wells in grassland areas

(z = 1.92, p-value = 0.027).

Nitrate was detected in 44 of 45 ground-water samples and

had the greatest median concentration (8.03 mg/L) of any nutrient. Nitrate concentrations ranged from <0.06 to 31.8 mg/L.

Seventeen samples (38 percent) had nitrate concentrations that

exceeded the MCL of 10 mg/L. Nitrate concentrations in wells

in agricultural areas were significantly greater than nitrate concentrations in grassland areas (z = 3.55, p-value = <0.001).

The δ15N values were measured in water samples from 42

of 45 wells sampled in the Cimarron terrace aquifer. δ15N values for the 42 wells ranged from –0.83 to 10.1‰, with a median

value of 4.28‰ and a mean of 4.59‰. Results from a Wilcoxon

Rank-Sum test comparing δ15N values measured in samples

from agricultural areas to δ15N values measured in samples

from grassland areas indicated that δ15N values were significantly greater in the agricultural areas than in the grassland

areas (z = 2.98, p-value = 0.002). The median δ15N value in the

agricultural areas was 5.15‰, whereas the median δ15N value

in the grassland areas was 2.36‰.

Pesticides were detected in water samples from 15 of 45

(33 percent) wells. Atrazine and deethylatrazine, a metabolite

of atrazine, were the most frequently detected. Deethylatrazine

was detected in water samples from 9 wells and atrazine was

detected in water samples from 8 wells. Atrazine concentrations

were less than the MCL of 3 micrograms per liter (μg/L).

Tebuthiuron was detected in water samples from 5 of the 45

wells, but none of the tebuthiuron concentrations exceeded the

USEPA health advisory of 500 μg/L. Metolachlor was detected

in water samples from 4 wells, but none of the metolachlor concentrations exceeded the USEPA health advisory of 100 μg/L.

Prometon was detected in water samples from 4 wells, but none

of the prometon concentrations exceeded the USEPA health

advisory of 500 μg/L. Alachlor was only detected in 1 well and

the concentration was less than the MCL of 2 μg/L.

Wastewater compounds were detected in water samples

from 28 of 45 wells (62 percent). Of the 20 wastewater compounds detected, 11 compounds (55 percent) were in the household category, 3 compounds (15 percent) were in the hydrocarbon category, 2 compounds (10 percent) were in the industrial

category, 2 compounds (10 percent) were in the pesticides category, 1 compound (5 percent) was in the animal category, and

1 compound (5 percent) was in the detergent category.

Wastewater compounds in the household category are

commonly used in products such as perfumes, coffee, soaps,

dyes, flame retardant products, lubricants, and disinfectants.

Fluoranthene, phenanthrene, and pyrene were the compounds in

the hydrocarbon category. P-cresol and triphenyl phosphate

were the compounds detected in the industrial category and are

commonly used in wood preservation and flame retardant products. Bromacil and N,N-diethyl-meta-toluamide (DEET) were

the compounds detected in the pesticides category. Skatole (3-

methyl-1h-indole) was the compound detected from the animal

category and is found in feces. Tributylphosphate was the compound detected from the detergent category and is a common

anti-foaming agent and flame retardant.

Phenol was the most frequently detected wastewater compound and was detected in 23 wells. DEET was the second most

frequently detected wastewater compound and was detected in

5 wells. Benzophenone, ethanol,2-butoxy phosphate, and tributylphosphate each were detected in 3 wells. The greatest number of wastewater compounds detected in a single well occurred

in W38 with 7 detections. Six wastewater compounds were

detected in W1 and W36. Wells W8 and W45 each had 4 wastewater compounds detected. The remaining 23 wells had 3 or

fewer wastewater compounds detected.

A qualitative and quantitative approach based on multiple

lines of evidence from chemical analysis of nitrate, nitrogen

isotopes in nitrate, commonly applied pesticides (indicative of

fertilizer application), and wastewater compounds (indicative

of human animal waste) was used to indicate possible sources

of nitrate. Individual wells were grouped into four possible

nitrate source categories: (1) synthetic fertilizer source; (2)

mixed sources (combination of synthetic fertilizer, septic or

manure sources, or natural sources); (3) septic or manure

sources; and (4) natural sources (plant, soil, or precipitation).

Synthetic fertilizer was the possible source of nitrate for 13

wells sampled in the Cimarron terrace aquifer. The nitrate

source category with the greatest number of wells (22 wells)

was the mixed sources category. There were 2 wells (W36 and

W43) where the possible source of nitrate was from septic or

manure sources. Seven wells had natural sources as the possible

nitrate source. The natural sources category had the greatest

range of δ15N values, with δ15N values ranging from –0.83 to

9.44‰.
42 Water Quality and Possible Sources of Nitrate in the Cimarron Terrace Aquifer, Oklahoma, 2003

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Appendixes
46 Water Quality and Possible Sources of Nitrate in the Cimarron Terrace Aquifer, Oklahoma, 2003
Appendixes 47

Appendix 1. Quality Control

All equipment used to collect water samples was cleaned

between sites using a non-phosphate detergent and was thoroughly rinsed with tap water followed by deionized water. After

rinsing of equipment with tap and deionized water, pesticide

equipment was rinsed with pesticide-grade methanol solvent

then allowed to air dry. Stainless steel compression fittings and

aluminum equipment were wrapped in aluminum foil and

placed inside new quality-assured plastic bags, as was the

Teflon tubing.

Quality-control samples were collected and analyzed to

evaluate the degree of accuracy, precision, and bias of environmental samples. Quality-control samples for this investigation

consisted of two field blank samples from W3 and W32, three

replicate environmental samples from wells W2, W19, and

W39, and two environmental-matrix spike samples from wells

W19 and W28.

Field blank samples are used to determine if environmental samples were contaminated during the sampling process.

Field blanks were prepared in the field by processing qualityassured high purity organic blank water through the sampling

equipment in exactly the same manner that environmental samples were collected. Field blank samples were analyzed for concentrations of nutrients, pesticides, and wastewater compounds.

For nutrients, a concentration of 0.2 mg/L of ammonia plus

organic nitrogen and a concentration of 0.002 mg/L of phosphorus were detected in a field blank collected at W3 (Appendix 3).

No nutrient concentrations were detected in the field blank sample collected from W32. Pesticide and wastewater compounds

were not detected in any of the field blanks collected from W3

and W32 (Appendix 5 and 6). Field blank samples indicated

that contamination from equipment and field procedures were

minimal.

Replicate environmental samples were analyzed for concentrations of nutrients, nitrogen isotopes, pesticides, and

wastewater compounds. Precision is calculated from one environmental sample and one replicate environmental sample,

expressed as the relative percent difference (RPD) using equation 2:

RPD = | C1 – C2 | / ((C1 + C2) / 2) * 100 (2)

where

C1 = largest of the two values;

C2 = smaller of the two values.

If either of a constituent concentration was less than the

analytical reporting level, then the RPD was not calculated.

RPD values for nutrient replicate samples ranged from 0 to 40

percent (table 19). RPD values for nitrogen isotope replicate

samples ranged from 3.9 to 41.8 percent (table 20). Pesticides

were not detected in environmental and replicate samples col-

 Table 19. Nutrient concentrations for environmental and replicate samples, shown with relative percent difference (RPD) values

[mg/L, milligrams per liter; RPD, relative percent difference; <, less than]

Well number Nitrite

(mg/L)

Nitrite plus

nitrate as

Nitrogen

(mg/L)

Ammonia

(mg/L)

Ammonia plus

organic

nitrogen

(mg/L)

Phosphorus

(mg/L)

Orthophosphate

(mg/L)

W39 (sample) <0.008 2.2 <0.04 0.06 0.047 0.04

W39 (replicate) <0.008 2.21 <0.04 0.05 0.048 0.04

RPD (percent) 0.45 18.2 1.4 0

W2 (sample) <0.008 12.3 <0.04 0.06 0.16 0.15

W2 (replicate) <0.008 12.5 <0.04 0.09 0.16 0.14

RPD (percent) 1.6 40.0 0 6.9

W19 (sample) <0.008 2.27 <0.04 <0.1 0.009 0.02

W19 (replicate) <0.008 2.18 <0.04 0.08 0.008 <0.02

RPD (percent) 4.0 11.7
48 Water Quality and Possible Sources of Nitrate in the Cimarron Terrace Aquifer, Oklahoma, 2003

lected from wells W2 and W19 (Appendix 5). Out of the three

replicate samples collected, pesticides were only detected in

well W39. RPD values were less than 6 percent (table 21). Concentrations in environmental and replicate samples for wastewater compounds were very similar (Appendix 6). RPD values

were not calculated because concentrations were listed as estimates or as non-detects. Small differences in low constituent

concentrations led to the greater RPD values. Replicate samples

generally indicated an acceptable degree of reproducibility of

results.

Two samples (W19 and W28) were spiked in the field with

known concentrations of pesticide compounds. Analytical

recoveries (AR) of the spiked pesticide compounds are

expressed in percentages in relation to a theoretical or calculated (expected) concentration using equation 3:

AR = ((Cspike –Csample) / Cexpect) * 100 (3)

where

Cspike = is the concentration of the spiked environmental

sample;

Csample = is the concentration of the environmental sample;

Cexpect = is the theoretical or calculated concentration, based

on spiked concentrations, known volume of individual spiked compounds, and volume of spiked environmental sample.

Analytical recoveries for samples from W19 ranged from

44.9 to 126.1 percent, with a mean recovery of 93.8 percent

(table 22). Analytical recoveries for the spiked sample from

well W28 ranged from 35.1 to 314.6 percent, with a mean

recovery of 102.7 percent. Five pesticides in the spiked sample

from well W19 (azinphos-methyl, carbaryl, cis-permethrin,

deethylatrazine, and Disulfoton) had analytical recoveries less

than 70 percent, and eight pesticides (acetochlor, alachlor,

alpha-HCH, diazinon, 2-6 diethylaniline, fonofos, lindane, and

Linuron) had analytical recoveries greater than 115 percent

(table 23). Six pesticides in the spiked sample from well W28

(cis-permethrin, deethylatrazine, disulfoton, p,p’-DDE, phorate, and Terbufos) had analytical recoveries less than 70 percent, and five pesticides (azinphos-methyl, carbaryl, carbofuran, Linuron, and propargite) had analytical recoveries greater

than 115 percent (table 23). Pesticides concentrations that are

underestimated in spike samples indicate that they could be

underestimated in the environmental samples. Pesticides concentrations that are overestimated in spike samples indicate that

they could be overestimated in the environmental samples.

 Table 20. Nitrogen isotope delta values (δ15N) in nitrate for environmental and replicate samples,

shown with relative percent difference (RPD) values

[RPD, relative percent difference; δ15N nitrogen isotope delta value]

Well number δ15N (permil)

W2 (sample) 3.16

W2 (replicate) 3.04

RPD (percent) 3.9

W19 (sample) 2.34

W19 (replicate) 2.75

RPD (percent) 16.1

W39 (sample) 2.52

W39 (replicate) 3.85

RPD (percent) 41.8
Appendixes 49

 Table 21. Pesticide concentrations for the single environmental and replicate sample in which pesticides were detected, shown with relative percent differences (RPD) values

[μg/L, micrograms per liter; RPD, relative percent difference; E, estimate]

Well ID Deethylatrazine

(μg/L)

Atrazine

(μg/L)

W39 (sample) E 0.117 0.043

W39 (replicate) E 0.124 0.043

RPD (percent) 5.8 0

 Table 22. Summary of pesticide environmental-matrix spike recoveries for selected pesticides in U.S. Geological Survey schedule 2001.

[all units are in percent]

Well ID

Percentiles

Maximum Mean

Minimum 25th 50th (Median) 75th

W19 44.9 72.2 92.8 109.0 126.1 93.8

W28 35.1 68.0 95.7 105.8 314.6 102.7
50 Water Quality and Possible Sources of Nitrate in the Cimarron Terrace Aquifer, Oklahoma, 2003

 Table 23. Individual pesticide environmental-matrix spike recoveries for selected pesticides in U.S. Geological Survey schedule 2001

[Env., environmental sample; conc., concentration; μg/L, micrograms per liter; %, percent]

Pesticide

W19 W28

Recovery

(%)

1

Env.

Sample

conc.

(μg/L)

Spiked

conc.

(μg/L)

Recovery

(%)

Env.

Sample

conc.

(μg/L)

Spiked

conc.

(μg/L)

Acetochlor 0 0.128 115.3 0 0.114 104.9

Alachlor 0 0.128 115.3 0 0.116 106.7

Alpha-HCH 0 0.134 120.7 0 0.101 92.9

Atrazine 0 0.112 100.9 0 0.121 111.3

Azinphos-methyl 0 0.052 46.9 0 0.221 203.3

Benfluralin 0 0.083 75.1 0 0.083 76.6

Butylate 0 0.127 114.4 0 0.096 88.5

Carbaryl 0 0.075 67.8 0 0.342 314.6

Carbofuran 0 0.11 99.1 0 0.26 239.5

Chlorpyrifos 0 0.111 100 0 0.107 98.4

cis-permethrin 0 0.067 60.5 0 0.067 62

Cyanazine 0 0.122 109.9 0 0.11 101.2

Dacthal (dcpa) 0 0.12 108.1 0 0.112 103

Deethylatrazine 0 0.05 44.9 0 0.041 37.8

Diazinon 0 0.14 126.1 0 0.106 97.5

Dieldrin 0 0.096 86 0 0.1 91.9

2-6 diethylaniline 0 0.131 118 0 0.112 103

Disulfoton 0 0.055 49.9 0 0.038 35.1

EPTC 0 0.102 91.9 0 0.095 87

Ethalfluralin 0 0.095 85.7 0 0.094 86.6

Ethoprophos 0 0.097 86.9 0 0.098 89.7

Fonofos 0 0.131 118 0 0.099 90.6

Lindane (Gamma-HCH) 0 0.137 123.4 0 0.104 95.7

Linuron 0 0.135 121.6 0 0.147 135.2

Malathion 0 0.102 91.9 0 0.137 126

Metolachlor 0 0.108 97.3 0 0.117 107.6

Metribuzin 0 0.091 81.8 0 0.094 86

Molinate 0 0.098 88.5 0 0.099 90.9
Appendixes 51

Napropamide 0 0.102 91.9 0 0.087 80.4

p,p'-DDE 0 0.089 80.4 0 0.072 66.2

Parathion 0 0.094 84.8 0 0.113 104

Parathion-methyl 0 0.09 80.7 0 0.123 113.2

Pebulate 0 0.1 89.8 0 0.097 89

Pendimethalin 0 0.084 75.9 0 0.084 77.5

Phorate 0 0.106 95.5 0 0.075 68.9

Prometon 0 0.125 112.6 0 0.117 107.6

Pronamide 0 0.115 103.6 0 0.096 88.7

Propachlor 0 0.114 102.7 0 0.115 105.8

Propanil 0 0.103 92.8 0 0.111 102.1

Propargite 0 0.113 101.8 0 0.131 120.5

Simazine 0 0.093 84 0 0.115 105.8

Tebuthiuron 0 0.111 100 0.0397 0.154 105.2

Terbacil 0 0.1 90.1 0 0.097 88.8

Terbufos 0 0.084 75.5 0 0.072 66.6

Thiobencarb 0 0.117 105.4 0 0.111 102.1

Triallate 0 0.126 113.5 0 0.095 86.9

Trifluralin 0 0.088 79.1 0 0.09 83.1

1

If a pesticide compound was not detected, a “0” was substituted as a value in order to calculate the recoveries.

 Table 23. Individual pesticide environmental-matrix spike recoveries for selected pesticides in U.S. Geological Survey schedule

2001—Continued

Pesticide

W19 W28

Recovery

(%)

1

Env.

Sample

conc.

(μg/L)

Spiked

conc.

(μg/L)

Recovery

(%)

Env.

Sample

conc.

(μg/L)

Spiked

conc.

(μg/L)
52 Water Quality and Possible Sources of Nitrate in the Cimarron Terrace Aquifer, Oklahoma, 2003

 Appendix 2. Water properties measured in samples from 45 wells in the Cimarron terrace aquifer, July and August 2003

[ID, identification number; μS/cm; microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter: -, no data]

Well

number

(fig. 3)

Site ID Date measured Time

Specific

conductance

(μS/cm)

pH

(standard units)

Water temperature

(degrees Celsius)

Dissolved

oxygen

(mg/L)

W1 355351097400301 08/07/03 0900 365 6.9 17.6 7.2

W2 355812097460001 07/18/03 0900 482 7.0 17.8 3.0

W3 355842097570001 07/16/03 1600 763 7.4 17.1 0.2

W4 360004097523601 07/15/03 0900 460 6.7 17.4 4.9

W5 360236097593501 07/15/03 1500 873 7.3 18.9 5.2

W6 360300098044601 07/15/03 1700 675 7.3 16.6 1.9

W7 360451097534801 07/11/03 1100 759 7.0 17.4 3.0

W8 360605098000401 07/15/03 1200 1,005 6.9 17.4 0.9

W9 360653098085601 07/16/03 1400 735 7.3 17.2 3.9

W10 360726098040101 07/11/03 0900 830 7.1 17.2 1.3

W11 360851098023901 07/08/03 1600 804 6.8 16.9 3.1

W12 361005098072601 07/16/03 1100 423 7.3 17.6 5.1

W13 361159098051501 07/08/03 1400 622 7.5 17.5 0.4

W14 361303098131501 07/10/03 1000 630 7.3 17.2 1.1

W15 361347098120901 07/10/03 1100 948 7.2 17.2 2.8

W16 361454098142601 07/09/03 1000 806 7.3 17.9 6.8

W17 361712098103401 07/08/03 1030 1,200 7.1 17.2 1.3

W18 361812098192101 07/09/03 1200 1,130 7.2 17.0 3.1

W19 361813098103201 07/08/03 0800 649 7.4 17.2 7.0

W20 361850098145201 07/10/03 1500 674 7.0 17.0 4.5

W21 361939098215301 07/09/03 1400 622 7.4 16.2 6.2

W22 362146098215401 07/16/03 1300 778 6.6 16.5 8.6

W23 362212098165201 07/16/03 0900 862 6.3 17.5 5.7

W24 362233098243601 08/07/03 1500 435 7.1 17.3 3.2

W25 362426098221001 07/16/03 1130 837 7.0 18.0 8.1

W26 362435098282201 07/09/03 1600 809 7.4 16.4 2.8

W27 362530098355201 07/03/03 1530 519 7.4 16.3 3.3

W28 362655098253101 07/17/03 0900 860 6.7 18.0 1.6

W29 362657098203101 08/08/03 1200 1,230 7.5 17.4 1.0

W30 362800098383701 07/02/03 1400 696 7.3 17.6 5.0

W31 362842098482401 07/02/03 1030 411 7.4 16.6 5.7

W32 362939098225701 07/17/03 1130 489 6.9 17.0 6.6

W33 363023098424801 07/16/03 1500 289 6.3 18.0 7.5

W34 363113098315201 07/11/03 1200 532 6.6 18.0 3.0

W35 363211098392401 07/03/03 0900 607 7.4 16.0 2.8

W36 363330098470001 07/08/03 1400 747 6.4 17.0 0.2

W37 363348098325401 07/09/03 1400 938 6.6 17.0 2.0

W38 363445098264001 07/23/03 1000 1,100 6.9 16.0 -

W39 363452098384301 07/08/03 1530 575 6.1 18.0 3.7

W40 363510098514601 07/02/03 1500 715 7.3 17.2 5.2

W41 363735098551801 07/11/03 1500 974 7.0 17.0 9.4

W42 363834098343801 07/09/03 1030 1,440 6.6 17.0 2.0

W43 364519098311701 07/09/03 1200 1,680 6.6 16.0 1.8

W44 364258099000801 07/08/03 1000 1,770 6.8 16.5 3.0

W45 364605098350001 07/11/03 0930 2,118 6.7 18.0 8.5
 Appendix 3. Nutrient concentrations in samples from 45 wells in the Cimarron terrace aquifer, July and August 2003[shading indicates quality-control sample; FB, field blank; R, replicate; E, estimate; mg/L, milligrams per liter; <, less than]

Well

number

(fig. 3)

Site ID Date Measured Time Nitrite (mg/L) Nitrite plus nitrate as nitrogen (mg/L) Ammonia (mg/L) Ammonia plus organic nitrogen (mg/L) Phosphorus (mg/L) 

W1 355351097400301 08/07/03 0900 <0.008 9.37 <0.04 <0.10 0.078 W2 355812097460001 07/18/03 0900 <0.008 12.3 <0.04 E 0.06 0.160 

W2-R 355812097460001 07/18/03 0905 <0.008 12.5 <0.04 E 0.09 0.160 

W3 355842097570001 07/16/03 1600 <0.008 2.19 <0.04 <0.10 0.044 

W3-FB 355842097570001 07/16/03 1615 <0.008 <0.06 <0.04 0.2 0.002 

W4 360004097523601 07/15/03 0900 <0.008 14.8 <0.04 E 0.06 0.140 W5 360236097593501 07/15/03 1500 <0.008 16.8 <0.04 E 0.09 0.050 W6 360300098044601 07/15/03 1700 <0.008 6.14 <0.04 <0.10 0.064 W7 360451097534801 07/11/03 1100 <0.008 10.1 <0.04 0.13 0.039 W8 360605098000401 07/15/03 1200 <0.008 6.93 <0.04 E 0.09 0.132 W9 360653098085601 07/16/03 1400 <0.008 <0.06 0.05 E 0.09 0.058 

W10 360726098040101 07/11/03 0900 <0.008 5.83 <0.04 E 0.09 0.153 W11 360851098023901 07/08/03 1600 <0.008 15.3 <0.04 0.14 0.082 W12 361005098072601 07/16/03 1100 <0.008 9.01 <0.04 <0.10 0.125 W13 361159098051501 07/08/03 1400 <0.008 1.11 <0.04 <0.10 0.034 W14 361303098131501 07/10/03 1000 <0.008 4.21 <0.04 0.15 0.077 W15 361347098120901 07/10/03 1100 <0.008 15.4 <0.04 0.14 0.077 W16 361454098142601 07/09/03 1000 <0.008 8.36 <0.04 0.13 0.035 W17 361712098103401 07/08/03 1030 <0.008 21.3 <0.04 0.16 0.049 W18 361812098192101 07/09/03 1200 <0.008 20.5 <0.04 0.12 0.026 W19 361813098103201 07/08/03 0800 <0.008 2.27 <0.04 <0.10 0.009 

W19-R 361813098103201 07/08/03 0805 <0.008 2.18 <0.04 E 0.08 0.008 

W20 361850098145201 07/10/03 1500 <0.008 14.4 <0.04 0.11 0.107 W21 361939098215301 07/09/03 1400 <0.008 4.11 <0.04 E 0.1 0.040 W22 362146098215401 07/16/03 1300 <0.008 16.4 <0.04 <0.10 0.053 W23 362212098165201 07/16/03 0900 <0.008 31.8 <0.04 E 0.1 0.138 W24 362233098243601 08/07/03 1500 <0.008 8.03 <0.04 <0.10 0.071 W25 362426098221001 07/16/03 1130 <0.008 11.2 <0.04 E 0.07 0.059 W26 362435098282201 07/09/03 1600 <0.008 4.38 <0.04 0.13 0.048 W27 362530098355201 07/03/03 1530 <0.008 8.35 <0.04 0.18 0.053 W28 362655098253101 07/17/03 0900 <0.008 2.48 <0.04 0.10 0.050 W29 362657098203101 08/08/03 1200 E 0.005 0.95 <0.04 <0.10 0.006 W30 362800098383701 07/02/03 1400 <0.008 14.9 <0.04 <0.10 0.061 
 Appendix 3. Nutrient concentrations for 45 wells sampled in the Cimarron terrace aquifer, July and August 2003 –Continued [FB, field blank; R, replicate; E, estimate; mg/L, milligrams per liter; <, less than] Well number Site ID Date Measured Time Nitrite (mg/L) Nitrite plus nitrate as nitrogen (mg/L) Ammonia (mg/L) Ammonia plus organic nitrogen (mg/L) Phosphorus (mg/L) 

W31 362842098482401 07/02/03 1030 <0.008 0.13 E 0.03 E 0.05 0.014 W32 362939098225701 07/17/03 1130 <0.008 6.03 <0.04 <0.10 0.111 

W32-FB 362939098225701 07/17/03 1133 <0.008 <0.02 <0.04 <0.1 <0.004 

W33 363023098424801 07/16/03 1500 <0.008 3.63 <0.04 E 0.06 0.099 W34 363113098315201 07/11/03 1200 <0.008 15.6 <0.04 E 0.09 0.033 W35 363211098392401 07/03/03 0900 <0.008 1.24 <0.04 <0.10 0.045 W36 363330098470001 07/08/03 1400 0.020 0.37 <0.04 E 0.06 0.062 W37 363348098325401 07/09/03 1400 <0.008 3.68 <0.04 0.15 0.009 W38 363445098264001 07/23/03 1000 <0.008 20.4 0.70 0.88 0.068 W39 363452098384301 07/08/03 1530 <0.008 2.20 <0.04 E 0.06 0.047 

W39-R 363452098384301 07/08/03 1531 <0.008 2.21 <0.04 E 0.05 0.048 

W40 363510098514601 07/02/03 1500 <0.008 8.48 <0.04 0.10 0.047 W41 363735098551801 07/11/03 1500 <0.008 2.53 <0.04 E 0.07 0.037 W42 363834098343801 07/09/03 1030 0.046 11.9 <0.04 0.15 0.049 W43 364519098311701 07/09/03 1200 <0.008 5.99 <0.04 0.20 0.010 W44 364258099000801 07/08/03 1000 <0.008 3.30 <0.04 0.10 0.028 W45 364605098350001 07/11/03 0930 <0.008 17.9 <0.04 0.12 0.054 
Appendixes 55

 Appendix 4. Nitrogen isotope delta values (δ15N) in nitrate measured in samples

from 45 wells in the Cimarron terrace aquifer, July and August 2003

[shading indicates quality-control samples; ID, identification number; R, replicate; n/a, nitrogen

isotopes not measured because nitrate concentration was less than the concentration needed for nitrogen isotope analysis]

Well number

(fig. 3) Site ID Date measured Time δ15N (permil)

W1 355351097400301 08/07/03 900 2.66

W2 355812097460001 07/18/03 900 3.16

W2-R 355812097460001 07/18/03 905 3.04

W3 355842097570001 07/16/03 1,600 9.44

W4 360004097523601 07/15/03 900 2.31

W5 360236097593501 07/15/03 1,500 7.61

W6 360300098044601 07/15/03 1,700 6.47

W7 360451097534801 07/11/03 1,100 5.70

W8 360605098000401 07/15/03 1,200 7.70

W9 360653098085601 07/16/03 1,400 n/a

W10 360726098040101 07/11/03 900 7.11

W11 360851098023901 07/08/03 1,600 7.96

W12 361005098072601 07/16/03 1,100 4.88

W13 361159098051501 07/08/03 1,400 -0.83

W14 361303098131501 07/10/03 1,000 1.47

W15 361347098120901 07/10/03 1,100 7.77

W16 361454098142601 07/09/03 1,000 2.28

W17 361712098103401 07/08/03 1,030 8.53

W18 361812098192101 07/09/03 1,200 3.20

W19 361813098103201 07/08/03 800 2.34

W19-R 361813098103201 07/08/03 805 2.75

W20 361850098145201 07/10/03 1,500 2.85

W21 361939098215301 07/09/03 1,400 0.25

W22 362146098215401 07/16/03 1,300 5.15

W23 362212098165201 07/16/03 900 3.46

W24 362233098243601 08/07/03 1,500 3.05

W25 362426098221001 07/16/03 1,130 4.95

W26 362435098282201 07/09/03 1,600 0.43

W27 362530098355201 07/03/03 1,530 4.06

W28 362655098253101 07/17/03 900 5.50

W29 362657098203101 08/08/03 1,200 8.60

W30 362800098383701 07/02/03 1,400 4.49

W31 362842098482401 07/02/03 1,030 n/a

W32 362939098225701 07/17/03 1,130 4.98

W33 363023098424801 07/16/03 1,500 1.52

W34 363113098315201 07/11/03 1,200 5.50

W35 363211098392401 07/03/03 900 2.43

W36 363330098470001 07/08/03 1,400 n/a

W37 363348098325401 07/09/03 1,400 5.14

W38 363445098264001 07/23/03 1,000 2.48

W39 363452098384301 07/08/03 1,530 2.52

W39-R 363452098384301 07/08/03 1,531 3.85

W40 363510098514601 07/02/03 1,500 3.42

W41 363735098551801 07/11/03 1,500 1.85

W42 363834098343801 07/09/03 1,030 9.83

W43 364519098311701 07/09/03 1,200 10.1

W44 364258099000801 07/08/03 1,000 1.61

W45 364605098350001 07/11/03 930 8.69
 Appendix 5. Concentrations of pesticide and metabolite compounds detected in samples from 15 of 45 wells in the Cimarron terrace aquifer, July and [shading indicates quality-control sample; ID, site identification number; -, not detected; R, replicate; E, estimate; μg/L micrograms per liter] Well number (fig. 3) Site ID Date measured Time Total number of detections Alachlor (μg/L) Atrazine (μg/L) Deethylatrazine (metabolite) (μg/L) Metolachlor (μg/L) Promet

(μg/L

W5 360236097593501 07/15/03 1500 2 - E 0.004 E 0.012 - - W9 360653098085601 07/16/03 1400 2 - - E 0.007 - - 

W14 361303098131501 07/10/03 1000 1 - - - - - W15 361347098120901 07/10/03 1100 1 - - - - - W18 361812098192101 07/09/03 1200 4 - E 0.051 E 0.580 0.092 0.02W21 361939098215301 07/09/03 1400 2 - 0.111 E 0.056 - - W22 362146098215401 07/16/03 1300 3 - 0.027 E 0.063 E 0.011 - W23 362212098165201 07/16/03 0900 3 - E 0.007 E 0.023 0.060 - W25 362426098221001 07/16/03 1130 4 0.009 E 0.005 E 0.009 0.083 - W28 362655098253101 07/17/03 0900 1 - - - - - W32 362939098225701 07/17/03 1130 0 - - - - - 

W32-FB 362939098225701 07/17/03 1133 0 - - - - - 

W35 363211098392401 07/03/03 0900 1 - - - - - W37 363348098325401 07/09/03 1400 1 - - - - 0.04W39 363452098384301 07/08/03 1530 2 - 0.043 E 0.12 - - 

W39-R 363452098384301 07/08/03 1531 2 - E 0.043 E 0.12 - - 

W40 363510098514601 07/02/03 1500 3 - 0.008 E 0.02 - 0.12W43 364519098311701 07/09/03 1200 1 - - - - 0.08
 Appendix 6. Concentrations of wastewater compounds detected in 28 of 45 wells sampled in the Cimarron terrace aquifer, July and August 2003[ID, identification number; E, estimate; FB, field blank; <, less than; R, replicate; μg/L, micrograms per liter; -, non-detect]

Well

number Station ID Date measured Time Total number of detections Anthraquinone (μg/L) Benzophenone (μg/L) Benzo[a]pyrene (μg/L) Br

(

W1 355351097400301 08/07/03 0900 6 E 0.23 - - W2 355812097460001 07/18/03 0900 2 - E 0.02 - 

W2-R 355812097460001 07/18/03 0905 1 - <0.5 - 

W3 355842097570001 07/16/03 1600 1 - - - W5 360236097593501 07/15/03 1500 1 - - - W6 360300098044601 07/15/03 1700 2 - - - W8 360605098000401 07/15/03 1200 4 - - - 

W10 360726098040101 07/11/03 0900 1 - - - W11 360851098023901 07/08/03 1600 1 - - - W15 361347098120901 07/10/03 1100 1 - - - W18 361812098192101 07/09/03 1200 1 - - - W20 361850098145201 07/10/03 1500 2 - - - W21 361939098215301 07/09/03 1400 3 - E 0.01 - W22 362146098215401 07/16/03 1300 1 - - - W24 362233098243601 08/07/03 1500 1 - - - W25 362426098221001 07/16/03 1130 1 - - - W27 362530098355201 07/03/03 1530 1 - - - W29 362657098203101 08/08/03 1200 1 - - - W32 362939098225701 07/17/03 1130 0 - - - 

W32-FB 362939098225701 07/17/03 1133 0 - - - 

W33 363023098424801 07/16/03 1500 1 - - - W34 363113098315201 07/11/03 1200 2 - - - W35 363211098392401 07/03/03 0900 1 - - - W36 363330098470001 07/08/03 1400 6 - - E 0.01 W37 363348098325401 07/09/03 1400 2 - - - E W38 363445098264001 07/23/03 1000 7 - E 0.01 - W39 363452098384301 07/08/03 1530 1 - <0.50 - 

W39-R 363452098384301 07/08/03 1531 4 - E 0.01 - 

W40 363510098514601 07/02/03 1500 1 - - - W43 364519098311701 07/09/03 1200 2 - - - W44 364258099000801 07/28/03 0900 2 - - - W45 364605098350001 07/11/03 0930 4 - - - 
 Appendix 6. Concentrations of wastewater compounds detected in 28 of 45 wells sampled in the Cimarron terrace aquifer, July and August 2003—Co

Well ID Station ID Date measured (mo/dy/yr) Time Total number of detections Carbazole (μg/L) Diethyhexyl phthalate (μg/L) Ethanol,2-butoxy- phosphate (μg/L) Fluo

(

W1 355351097400301 08/07/03 0900 6 E 0.11 - - W2 355812097460001 07/18/03 0900 2 - - - W3 355842097570001 07/16/03 1600 1 - - - W5 360236097593501 07/15/03 1500 1 - - - W6 360300098044601 07/15/03 1700 2 - - - W8 360605098000401 07/15/03 1200 4 - - - 

W10 360726098040101 07/11/03 0900 1 - - - W11 360851098023901 07/08/03 1600 1 - - - W15 361347098120901 07/10/03 1100 1 - - - W18 361812098192101 07/09/03 1200 1 - - - W20 361850098145201 07/10/03 1500 2 - - - W21 361939098215301 07/09/03 1400 3 - - E 0.19 W22 362146098215401 07/16/03 1300 1 - - - W24 362233098243601 08/07/03 1500 1 - - - W25 362426098221001 07/16/03 1130 1 - - - W27 362530098355201 07/03/03 1530 1 - - - W29 362657098203101 08/08/03 1200 1 - - - W32 362939098225701 07/17/03 1130 0 - - - 

W32-FB 362939098225701 07/17/03 1133 0 - - - 

W33 363023098424801 07/16/03 1500 1 - - E 0.82 W34 363113098315201 07/11/03 1200 2 - - 0.50 W35 363211098392401 07/03/03 0900 1 - - - W36 363330098470001 07/08/03 1400 6 E 0.01 - - E W37 363348098325401 07/09/03 1400 2 - - - W38 363445098264001 07/23/03 1000 7 - 1.10 - W39 363452098384301 07/08/03 1530 1 - <1.0 - 

W39-R 363452098384301 07/08/03 1531 4 - 0.16 - 

W40 363510098514601 07/02/03 1500 1 - - - W43 364519098311701 07/09/03 1200 2 - - - E W44 364258099000801 07/28/03 0900 2 - - - W45 364605098350001 07/11/03 0930 4 - 1.50 - 
 Appendix 6. Concentrations of wastewater compounds detected in 28 of 45 wells sampled in the Cimarron terrace aquifer, July and August 2003—Co

Well

number Station ID Date measured Time Total number of detections Isoquinoline (μg/L) Methyl salicylate (μg/L) N,N-diethyl-meta- toluamide (DEET) (μg/L) P-

(

W1 355351097400301 08/07/03 0900 6 0.04 - E 0.04 W2 355812097460001 07/18/03 0900 2 - - - W3 355842097570001 07/16/03 1600 1 - - - W5 360236097593501 07/15/03 1500 1 - - - W6 360300098044601 07/15/03 1700 2 - - E 0.03 W8 360605098000401 07/15/03 1200 4 - - E 0.04 

W10 360726098040101 07/11/03 0900 1 - - - W11 360851098023901 07/08/03 1600 1 - - - W15 361347098120901 07/10/03 1100 1 - - - W18 361812098192101 07/09/03 1200 1 - - - W20 361850098145201 07/10/03 1500 2 - - - W21 361939098215301 07/09/03 1400 3 - E 0.02 - W22 362146098215401 07/16/03 1300 1 - - - W24 362233098243601 08/07/03 1500 1 - - - W25 362426098221001 07/16/03 1130 1 - - - W27 362530098355201 07/03/03 1530 1 - - - W29 362657098203101 08/08/03 1200 1 - - - W32 362939098225701 07/17/03 1130 0 - - - 

W32-FB 362939098225701 07/17/03 1133 0 - - - 

W33 363023098424801 07/16/03 1500 1 - - - W34 363113098315201 07/11/03 1200 2 - - - W35 363211098392401 07/03/03 0900 1 - - - W36 363330098470001 07/08/03 1400 6 - - - W37 363348098325401 07/09/03 1400 2 - - E 0.04 W38 363445098264001 07/23/03 1000 7 - - - 3W39 363452098384301 07/08/03 1530 1 - - <0.5 

W39-R 363452098384301 07/08/03 1531 4 - - E 0.04 

W40 363510098514601 07/02/03 1500 1 - - - W43 364519098311701 07/09/03 1200 2 - - - W44 364258099000801 07/28/03 0900 2 - - - W45 364605098350001 07/11/03 0930 4 - - E 0.03 E 
 Appendix 6. Concentrations of wastewater compounds detected in 28 of 45 wells sampled in the Cimarron terrace aquifer, July and August 2003—Co

Well number Station ID Date measured Time Total number of detections Phenol (μg/L) Pyrene (μg/L) Skatole (3-methyl-1h- indole) (μg/L) Tr

pho

(

W1 355351097400301 08/07/03 0900 6 E 0.29 - - W2 355812097460001 07/18/03 0900 2 E 0.33 - - 

W2-R 355812097460001 07/18/03 0905 1 2.0 - - 

W3 355842097570001 07/16/03 1600 1 1.20 - - 

W3-FB 355842097570001 07/16/03 1615 0 <0.5 - - 

W5 360236097593501 07/15/03 1500 1 E 0.98 - - W6 360300098044601 07/15/03 1700 2 E 0.26 - - W8 360605098000401 07/15/03 1200 4 E 0.48 - - E 

W10 360726098040101 07/11/03 0900 1 0.85 - - W11 360851098023901 07/08/03 1600 1 E 0.20 - - W15 361347098120901 07/10/03 1100 1 0.59 - - W18 361812098192101 07/09/03 1200 1 E 0.26 - - W20 361850098145201 07/10/03 1500 2 0.94 - - W21 361939098215301 07/09/03 1400 3 - - - W22 362146098215401 07/16/03 1300 1 E 0.97 - - W24 362233098243601 08/07/03 1500 1 E 0.47 - - W25 362426098221001 07/16/03 1130 1 1.20 - - W27 362530098355201 07/03/03 1530 1 E 0.32 - - W29 362657098203101 08/08/03 1200 1 E 0.39 - - W32 362939098225701 07/17/03 1130 0 - - - 

W32-FB 362939098225701 07/17/03 1133 0 - - - 

W33 363023098424801 07/16/03 1500 1 - - - W34 363113098315201 07/11/03 1200 2 E 0.47 - - W35 363211098392401 07/03/03 0900 1 E 0.28 - - W36 363330098470001 07/08/03 1400 6 E 0.21 E 0.01 - W37 363348098325401 07/09/03 1400 2 - - - W38 363445098264001 07/23/03 1000 7 5.0 - E 0.83 E W39 363452098384301 07/08/03 1530 1 E 0.20 - - 

W39-R 363452098384301 07/08/03 1531 4 E 0.43 - - 

W40 363510098514601 07/02/03 1500 1 E 0.34 - - W43 364519098311701 07/09/03 1200 2 - E 0.01 - W44 364258099000801 07/28/03 0900 2 E 0.27 - - W45 364605098350001 07/11/03 0930 4 - - - E