QUALITY OF WATER FROM SHALLOW WELLS IN THE

RICE-GROWING AREA IN SOUTHWESTERN LOUISIANA,

1999 THROUGH 2001

NATIONAL WATER-QUALITY ASSESSMENT PROGRAM

Water-Resources Investigations

Report 03-4050

U.S. Department of the Interior

U.S. Geological Survey
Cover photographs

Left: Crawfish/rice field, Acadia Parish, Louisiana

Upper right: Rice, Pointe Coupee Parish, near Livonia, Louisiana

Lower right: Pumping well in rice field, Acadia Parish

(Photographs by Dennis K. Demcheck, U.S. Geological Survey)
i

Quality of Water from Shallow Wells in the 

Rice-Growing Area in Southwestern 

Louisiana, 1999 through 2001

By Roland W. Tollett and Robert B. Fendick, Jr.

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 03-4050

National Water-Quality Assessment Program

Baton Rouge, Louisiana

2004
ii

U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

Any use of trade, product, or firm names in this report is for descriptive purposes only and does not imply endorsement 

by the U.S. Government.

For additional information contact: Copies of this report can be purchased

from:

District Chief

U.S. Geological Survey U.S. Geological Survey

3535 S. Sherwood Forest Blvd., Suite 120 Branch of Information Services

Baton Rouge, LA 70816 Box 25286

E-mail: dc_la@usgs.gov Denver, CO 80225

Fax: (225) 298-5490 E-mail: infoservices@usgs.gov

Telephone: (225) 298-5481 Fax: (303) 202-4693

Telephone (toll free): 1-888-ASK-USGS

Information regarding the National Water-Quality Assessment (NAWQA) Program is available on 

the Internet via the World Wide Web. You may connect to the NAWQA Home Page using the 

Universal Resource Locator (URL) at:

http://water.usgs.gov/nawqa
iii

FOREWORD

The U.S. Geological Survey (USGS) is committed to serve the Nation with accurate and timely scientific information that helps enhance and protect the overall quality of life and facilitates effective management of water, biological, energy, and mineral resources. Information on the quality of the Nation’s water 

resources is of critical interest to the USGS because it is so integrally linked to the long-term availability of 

water that is clean and safe for drinking and recreation and that is suitable for industry, irrigation, and habitat 

for fish and wildlife. Escalating population growth and increasing demands for the multiple water uses make 

water availability, now measured in terms of quantity and quality, even more critical to the long-term sustainability of our communities and ecosystems.

The USGS implemented the National Water-Quality Assessment (NAWQA) Program to support

national, regional, and local information needs and decisions related to water-quality management and policy. Shaped by and coordinated with ongoing efforts of other Federal, State, and local agencies, the NAWQA

Program is designed to answer: What is the condition of our Nation’s streams and ground water? How are the

conditions changing over time? How do natural features and human activities affect the quality of streams and

ground water, and where are those effects most pronounced? By combining information on water chemistry,

physical characteristics, stream habitat, and aquatic life, the NAWQA Program aims to provide science-based

insights for current and emerging water issues. NAWQA results can contribute to informed decisions that

result in practical and effective water-resource management and strategies that protect and restore water quality.

Since 1991, the NAWQA Program has implemented interdisciplinary assessments in more than 50 of

the Nation’s most important river basins and aquifers, referred to as Study Units. Collectively, these Study

Units account for more than 60 percent of the overall water use and population served by public water supply

and are representative of the Nation’s major hydrologic landscapes, priority ecological resources, and agricultural, urban, and natural sources of contamination. 

Each assessment is guided by a nationally consistent study design and methods of sampling and analysis. The assessments thereby build local knowledge about water-quality issues and trends in a particular 

stream or aquifer while providing an understanding of how and why water quality varies regionally and 

nationally. The consistent, multi-scale approach helps to determine if certain types of water-quality issues are 

isolated or pervasive and allows direct comparisons of how human activities and natural processes affect 

water quality and ecological health in the Nation’s diverse geographic and environmental settings. Comprehensive assessments on pesticides, nutrients, volatile organic compounds, trace metals, and aquatic ecology 

are developed at the national scale through comparative analysis of the Study-Unit findings. 

The USGS places high value on the communication and dissemination of credible, timely, and relevant science so that the most recent and available knowledge about water resources can be applied in management and policy decisions. We hope this NAWQA publication will provide you the needed insights and 

information to meet your needs and thereby foster increased awareness and involvement in the protection and 

restoration of our Nation’s waters. 

The NAWQA Program recognizes that a national assessment by a single program cannot address all 

water-resource issues of interest. External coordination at all levels is critical for a fully integrated understanding of watersheds and for cost-effective management, regulation, and conservation of our Nation’s 

water resources. The Program, therefore, depends extensively on the advice, cooperation, and information 

from other Federal, State, interstate, Tribal, and local agencies, non-government organizations, industry, academia, and other stakeholder groups. The assistance and suggestions of all are greatly appreciated.

Robert M. Hirsch

Associate Director for Water
iv
v

CONTENTS

Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .iii

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

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

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

Description of Study Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Hydrogeologic Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Land Use, Water Use, and Population . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Well-Site Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Well Installation and Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Well-Construction Data and Measurement of Water Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Sample Collection and Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Quality-Control Data Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Quality of Water from Shallow Wells in the Rice-Growing Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

General Ground-Water Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

Dissolved Solids and Major Inorganic Ions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

Trace Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

Nutrients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

Dissolved Organic Carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

Pesticides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

Radon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

Chlorofluorocarbons (Apparent Age of Ground Water) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

Stable Isotopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

Statistical Correlations of Physical Properties and Chemical Constituents. . . . . . . . . . . . . . . . . . . . . . . . .23

Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

Selected References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26

Appendixes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29

1. General ground-water properties in water from selected shallow wells in the rice-growing area in 

southwestern Louisiana, 2000-01 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30 

2. Dissolved solids and major inorganic ion concentrations in water from selected shallow wells in

the rice-growing area in southwestern Louisiana, 2000-01 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

3. Trace-element concentrations in water from selected shallow wells in the rice-growing area in 

southwestern Louisiana, 2000-01 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

4. Nutrients and dissolved organic carbon concentrations in water from selected shallow wells in

the rice-growing area in southwestern Louisiana, 2000-01 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

5. Pesticide concentrations in water from selected shallow wells in the rice-growing area in

southwestern Louisiana, 2000-01 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

6. Concentrations of pesticide degradation products in water from selected shallow wells in the

rice-growing area in southwestern Louisiana, 2000-01 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42

7. Radon, chlorofluorocarbons, and stable isotope concentrations in water from selected shallow 

wells in the rice-growing area in southwestern Louisiana, 2000-01 . . . . . . . . . . . . . . . . . . . . . . . . . . .44

FIGURES

1. Map showing study area and well locations in the rice-growing area in southwestern Louisiana 

in the Acadian-Pontchartrain Study Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2. Diagram showing selected hydrogeologic units in southwestern Louisiana . . . . . . . . . . . . . . . . . . . . . 5

3. Map showing major land-use types in the rice-growing area in southwestern Louisiana 

in the Acadian-Pontchartrain Study Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4. Graph showing percentages of major inorganic ions in water from selected shallow wells in the 

rice-growing area in southwestern Louisiana, 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
vi

5. Map showing highest percentage cations and anions in water from selected shallow wells in the 

rice-growing area in southwestern Louisiana, 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

6. Map showing number of pesticides and pesticide degradation products detected in water from 

selected shallow wells in the rice-growing area in southwestern Louisiana, 2000 . . . . . . . . . . . . . . . .17

7. Graph showing frequency of pesticides and pesticide degradation products in water from selected

shallow wells in the rice-growing area in southwestern Louisiana, 2000 . . . . . . . . . . . . . . . . . . . . . . .19

8. Graph showing radon concentrations in water from selected shallow wells in the rice-growing

area in southwestern Louisiana, 2000-01 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

9. Map showing radon concentrations in water from selected shallow wells in the rice-growing

area in southwestern Louisiana, 2000-01 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

10. Map showing apparent ages of water from selected shallow wells in the rice-growing area in 

southwestern Louisiana, 2000-01 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

11. Graph showing relation between delta (δ) deuterium and δ oxygen-18 in water from selected 

shallow wells in the rice-growing area in southwestern Louisiana, 2000 . . . . . . . . . . . . . . . . . . . . . . .23

TABLES

1. Site information and well-construction data for selected shallow wells in the rice-growing area in 

southwestern Louisiana, 1999-2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2. Methods used to analyze ground-water samples from selected shallow wells in the rice-growing

area in southwestern Louisiana . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3. Summary statistics for general ground-water properties, dissolved solids, major inorganic ions, 

trace elements, nutrients, and dissolved organic carbon in water from selected shallow wells in

the rice-growing area in southwestern Louisiana, 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

4. Concentrations of pesticide and pesticide degradation products in water from selected shallow

wells in the rice-growing area in southwestern Louisiana, 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

5. Results of Spearman rank correlation test for physical properties and selected chemical constituents in water from selected shallow wells in the rice-growing area in southwestern Louisiana, 

2000-01 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

CONVERSION FACTORS, DATUMS, AND ABBREVIATED WATER-QUALITY UNITS

Multiply By To obtain

acre 0.4047 hectare

foot (ft) 0.3048 meter (m)

inch (in.) 25.4 millimeter (mm)

mile (mi) 1.609 kilometer (km)

million gallons per day (Mgal/d) 0.04381 cubic meter per second

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 (NGVD 29)--a geodetic datum 

derived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called Sea Level

Datum of 1929.

Horizontal coordinate information is referenced to the North American Datum of 1927.

Temperature in degrees Fahrenheit (°F) can be converted to degrees Celsius (°C) as follows: °C = (°F - 32)/1.8.

Abbreviated water-quality units:

micrograms per liter (μg/L)

microsiemens per centimeter at 25 degrees Celsius (μS/cm)

milligrams per liter (mg/L)

nephelometric turbidity units (NTU)

picocuries per liter (pCi/L)

picograms per kilogram (pg/kg)

standard units (S.U.)
1

Quality of Water from Shallow Wells in the RiceGrowing Area in Southwestern Louisiana, 1999 

through 2001

By Roland W. Tollett and Robert B. Fendick, Jr.

ABSTRACT

 In 1999-2001, the U.S. Geological Survey 

installed and sampled 27 shallow wells in the ricegrowing area in southwestern Louisiana as part of the 

Acadian-Pontchartrain Study Unit of the National WaterQuality Assessment Program. The purpose of this report 

is to describe the quality of water from shallow wells in 

the rice-growing area and to relate that water quality to 

natural and anthropogenic activities, particularly rice 

agriculture. Ground-water samples were analyzed for 

general ground-water properties and about 150 waterquality constituents, including major inorganic ions, 

trace elements, nutrients, dissolved organic carbon 

(DOC), pesticides, radon, chlorofluorocarbons, and 

selected stable isotopes.

Dissolved-solids concentrations for 17 wells 

exceeded the U.S. Environmental Protection Agency 

secondary maximum contaminant level of 500 milligrams per liter (mg/L) for drinking water. Concentrations for major inorganic ions, trace elements, and 

pesticides generally were less than the maximum contaminant levels for drinking water. Two major inorganic 

ions, sulfate and chloride, and two trace elements, iron 

and manganese, had concentrations that were greater 

than the secondary maximum contaminant levels. 

Three nutrient concentrations were greater than 2 mg/L, 

a level that might indicate contamination from human 

activities, and one nutrient concentration (that for nitrite 

plus nitrate as nitrogen) was greater than the maximum 

contaminant level of 10 mg/L for drinking water. The 

median concentration for DOC was 0.5 mg/L, indicating naturally-occurring DOC conditions in the study 

area. Thirteen pesticides and 7 pesticide degradation 

products were detected in 14 of the 27 wells sampled. 

Bentazon, 2,4-D, and molinate (three rice herbicides) 

were detected in water from four, one, and one wells, 

respectively, and malathion (a rice insecticide) was 

detected in water from one well. Low-level concentrations and few detections of nutrients and pesticides indicated that ground-water quality was affected slightly by 

anthropogenic activities. Quality-control samples, 

including field blanks, replicates, and spikes, indicated 

no bias in ground-water data from collection or analysis.

Radon concentrations for 22 of the 24 wells 

sampled were at or greater than the U.S. Environmental 

Protection Agency proposed maximum contaminant 

level of 300 picocuries per liter. Chlorofluorocarbon 

concentrations in selected wells indicated the apparent 

ages of the ground water varied with depth and water 

level and ranged from about 17 to 49 years. The stable 

isotopes of hydrogen and oxygen in water molecules 

indicated the origin of ground water in the study area was 

rainwater that originated near the study area and that few 

geochemical or physical processes influenced the stable 

isotopic composition of the shallow ground water.

The Spearman rank correlation was used to 

determine whether significant correlations existed 

between physical properties, selected chemical 

constituents, the number of pesticides detected, and the 

apparent age of water. The depth to ground water was 

positively correlated to the well depth and inversely 

correlated to dissolved solids and other constituents, 

such as radon, indicating the ground water was under 

unconfined or semiconfined conditions and more dilute 

with increasing depth. As the depth to ground water 

increased, the concentrations of dissolved solids and 

other constituents decreased, possibly because the 

deeper sands had a greater transmittal of ground water, 

which, over time, would flush out, or dilute, the 

concentrations of dissolved solids in the natural 

sediments. The apparent age of water was correlated 

inversely with nitrite plus nitrate concentration, 

indicating that as the apparent age increased, the nitrite 

plus nitrate concentration decreased. No significant 

correlations existed between the number of pesticides 

detected and any of the physical or chemical properties 

of the ground water.
2

INTRODUCTION

Ground water is one of the Nation’s most important resources and is the source of drinking water for about 

50 percent of the population, or about 130 million United 

States residents (U.S. Geological Survey, 1999b). 

Because ground water is used for public-water supplies 

and because of the potential for ground water to affect surface-water quality and ecological and recreational 

resources, degradation of ground-water quality as a result 

of anthropogenic activities is a major concern. Therefore, 

in 1991, the U.S. Geological Survey (USGS) began full 

implementation of the National Water-Quality Assessment (NAWQA) Program to describe the status and trends 

in the quality of the Nation’s surface- and ground-water 

resources and to determine the natural and human-related 

factors that affect water quality (Hirsch and others, 1988; 

Gilliom and others, 1995). Knowledge of the quality of 

the Nation’s surface- and ground-water resources is 

important for the protection of human and aquatic health 

and for the management of land and water resources and 

the conservation and regulation of those resources. More 

than 50 major river basins or aquifer systems, referred to 

as Study Units, have been identified for investigation as 

part of the NAWQA Program. Together, these basins and 

aquifer systems include water resources available to more 

than 60 percent of the population and cover about onehalf of the land area in the conterminous United States.

Ground-water studies in the NAWQA Program 

include (1) sub-unit surveys, designed to assess the water 

quality of major aquifer systems within a Study Unit; 

(2) land-use studies, designed to assess the quality of 

recently recharged ground water associated with regionally extensive combinations of land use and hydrogeologic conditions; and (3) flowpath studies, designed to 

examine specific relations among land-use practices, 

ground-water flow, contaminant occurrence and transport, and surface- and ground-water interactions (Gilliom 

and others, 1995). During 1997-2002, two sub-unit 

surveys (Chicot aquifer system and Chicot equivalent 

aquifer system) and two land-use studies (one agriculture 

study and one urban study) were completed for the 

Acadian-Pontchartrain (ACAD) Study Unit of the 

NAWQA Program. The ACAD Study Unit encompasses 

most of southern Louisiana and a small part of southwestern Mississippi (fig. 1).

A land-use study was begun in 1999 for the ricegrowing area overlying the Chicot aquifer system in 

southwestern Louisiana in the ACAD Study Unit. 

Objectives of the study were to assess the occurrence and 

distribution of water-quality constituents in recently 

recharged ground water (generally less than 20- to 

30-years old) associated with a major land use in the study 

area and to gain an understanding of the natural and 

human-related factors that affect ground-water quality. 

Data from the study can be compared to data from similar 

studies throughout the United States to assess the quality 

of the Nation’s water resources, to determine any longterm changes in water quality, and to identify the natural 

and human-related factors that might affect water quality 

(Gilliom and others, 1998).

Rice was chosen for this land-use study because 

that crop accounts for the second largest crop acreage in 

southwestern Louisiana and because the rice-growing 

area in southwestern Louisiana overlies the Chicot aquifer 

system. The Chicot aquifer system is the primary source 

of water for irrigation and public-water supplies in the 

area and, in 1988, was declared a Sole Source Aquifer by 

the U.S. Environmental Protection Agency (USEPA) 

(U.S. Environmental Protection Agency, 2002c). This 

designation recognizes that the aquifer system is the sole 

or principal source of drinking water for the area and also 

recognizes that no alternative sources of drinking water 

are reasonably available should the aquifer become 

contaminated. Water in the Chicot aquifer system is 

vulnerable to the effects of land-surface activities in many 

areas of southwestern Louisiana because of shallow 

depths to ground water. Vertical leakage through the 

surficial confining unit that overlies the aquifer system 

and large ground-water withdrawals for irrigation near 

pumping centers might contribute to the potential for 

downward migration of contaminants to the aquifer 

underlying the rice-growing area.

Purpose and Scope

The purpose of this report is to describe the 

quality of water from 27 shallow wells in the ricegrowing area in southwestern Louisiana and to relate 

that water quality to natural factors, such as well 

depth and depth to ground water, and human activities, such as pesticide and fertilizer use. Groundwater samples collected from 1999 through 2001 from 

the 27 wells were analyzed for 7 general ground-water 

properties, 10 major inorganic ions, 24 trace elements, 6 nutrients, dissolved organic carbon (DOC), 

109 pesticides, radon, chlorofluorocarbons (CFCs), 

and selected stable isotopes. The Spearman rank correlation was used to determine whether significant 

correlations existed between physical properties, 

selected chemical constituents, the number of pesticides detected, and the apparent age of ground water. 

Although the shallow wells are not used as a 

drinking-water source, many of the constituents are 

regulated in public drinking-water supplies by the 

USEPA, and USEPA standards can be used as a frame 

of reference.
Map credit: Modified from, Official Map of Louisiana, Department of Transportation and Development, 1986

Area Shown

Index Map

ACAD Study 

Unit Boundary

Arkansas

Louisiana

iss s ipp

M

i s i

Texas

30 MILES

0 30 KILOMETERS

0

Rice-growing area

 (source: Joseph Holmes, Louisiana

 Department of Environmental Quality,

 written commun., 2001)

EXPLANATION

Well location and number

Study a are

Water

24

Figure 1. Study area and well locations in the rice-growing area in southwestern Louisiana in the Acadian-Pontchartrain Study Unit.

Recharge area of the Chicot

aquifer system in the AcadianPontchartrain (ACAD) Study Unit

(modified from Nyman, 1984, pl. 1)

Boundary of freshwater in the Chicot

aquifer system in the ACAD Study

Unit m( odified from Smoot, 1986)

Boundary of the ACAD Study Unit

3

Lake

Charles

Jennings Crowley

Oberlin

Lafayette

Lake

Arthur

1

13

22

24

26

17

16

8

5

18

6

9

3

19

15

4

23

25

11

30

28

10

27

14

2

21

7

B N SA I E L E AK

A C IE L AS U C

LAKE

WHITE

LAKE

GRAND

LAKE

S

CAL

A

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VERMILION

BAY WEST COTE

BLANCHE BAY

V n ermilio

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Teche

BA OU Y

b n Sa e i Riv r e

G F M XI O

ULF O E C

92° 00 ́

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BEAUREGARD

VERNON

EVANGELINE

ALLEN

ST LANDRY

JEFFERSON

DAVIS

CALCASIEU

ACADIA

VERMLI ION IBERIA

ST. MARTIN

CAMERON

LAFAYETTE

RAPIDES

AVOYELLES
4

Acknowledgments

The authors express appreciation to the rice 

farmers and landowners in the study area for allowing 

the USGS to install and sample wells located on their 

property. The authors also wish to thank personnel 

from the Louisiana State University Agricultural 

Center, particularly Dr. J.A. Musick (Rice Research 

Station, Crowley, La.) and Dr. J.K. Saichuk (Louisiana State Cooperative Extension Service, Crowley, 

La.), and individual county agents in the study area 

for their cooperation and participation in determining 

locations to install wells.

DESCRIPTION OF STUDY AREA

The study area is located in southwestern 

Louisiana (fig. 1). Land-surface elevations in the ricegrowing area range from about 5 to 80 ft above the 

NGVD 29. The region is drained primarily by Bayou 

Lacassine and the Calcasieu, Mermentau, and 

Vermilion Rivers.

Climate

The climate in southwestern Louisiana is 

humid and subtropical. The average annual rainfall 

for the area ranges from about 56 in. to 64 in. 

(Carlson, 1986, p. 253). The average annual rainfall 

for three selected stations in the rice-growing area for 

1998-2000 was 51.4 in., about 10.2 in. less than the 

30-year normal for 1971-2000 (Louisiana State Office 

of Climatology, written commun., 2000). Rainfall at 

the three stations--the Oberlin Fire Tower, Crowley 

Airport, and Lake Arthur Airport--was less than 

normal during 1999 and 2000. Annual rainfall ranged 

from 37.6 in. at the Crowley Airport in 1999 to 

74.6 in. at the Lake Arthur Airport in 1998. The 

average annual temperature for the three stations for 

1998-2000 was 69.5°F, which is 1.9°F higher than the 

30-year normal for 1971-2000. Annual temperatures 

ranged from 68.3°F at the Oberlin Fire Tower in 2000 

to 71.3°F at the Lake Arthur Airport in 2000.

Hydrogeologic Setting

The Chicot aquifer system is a thick sequence 

of interbedded clays, silts, sands, and gravels and 

underlies most of southwestern Louisiana and parts 

of eastern Texas. The sediments, deposited in deltaic and near-shore marine environments during the 

Pleistocene Epoch, dip and thicken southward to the 

Gulf Coast (Lovelace, 1999) and are characterized by 

massive beds of coarse sand and gravel separated by 

beds of clay. The sand beds generally are several 

hundred feet thick and are separated in places by 

thick discontinuous clays (Nyman and others, 1990). 

Recharge to the Chicot aquifer system (fig. 1) occurs 

from downward percolation of water in the outcrop 

area, through the Atchafalaya aquifer in the eastern 

part of the study area, and through surficial clay 

units, and, to a lesser extent, from upward leakage 

from the underlying Evangeline aquifer 

(Lovelace, 1999).

Shallow sands in the northern part of the 

study area are referred to as “undifferentiated sands” 

of the Chicot aquifer system (fig. 2) (Nyman and 

others, 1990). In the Lake Charles area, the Chicot 

aquifer system contains the “200-foot”, “500-foot”, 

and “700-foot” sands. East of the Lake Charles area 

in the rice-growing area, the Chicot aquifer system is 

divided into two major sand units, an “upper sand” 

and a “lower sand”. Prior to development, regional 

ground-water flow in the Chicot aquifer system 

generally was to the south-southeast (Nyman and 

others, 1990, p. 34). However, intensive use of 

ground water for rice irrigation in the central part of 

southwestern Louisiana and for industrial use in the 

Lake Charles area has affected the regional flow 

direction in many areas. Ground-water movement 

now is to the west in parts of the eastern part of the 

study area and to the north (from the Louisiana 

coast) in parts of the central part of the study area 

(Lovelace and others, 2002).

At the top of the Chicot aquifer system is a 

thick layer of clay that is a surficial confining unit. 

The confining unit is areally extensive throughout 

most of southwestern Louisiana and generally 

averages about 100 ft in thickness throughout most of 

the study area. However, the unit is more than 

500 ft thick in parts of Calcasieu and Cameron 

Parishes (Jones and others, 1954, pl. 4). The surficial 

confining unit once was thought to be an 

impermeable layer, but ground-water model estimates 

indicate that as much as 6 in. per year of water, 

primarily from the surface, recharge the Chicot 

aquifer system near major pumping centers (Nyman 

and others, 1990, p. 33). Although the model 

estimates indicate slight permeability in the surficial 

confining unit, rice cultivation during the past 

100 years has caused salts and fine clays to leach 

downward, forming a low-permeability horizon, or 

hardpan, in sediments underlying the rice fields 

(Lovelace, 1999, p. 9).
5

Land Use, Water Use, and Population

The rice-growing area in southwestern Louisiana 

includes all or parts of 12 parishes (fig. 3). Rice agriculture is the primary land use followed by forest, other 

crops, marsh, and urban. For 1992-96, the major crop 

grown was rice (about 428,000 acres) followed by soybeans (about 343,000 acres), corn (about 53,000 acres), 

and sugarcane (about 39,000 acres). For the same 5-year 

period, the number of acres planted in rice was largest in 

Vermilion Parish (about 95,000 acres), second largest in 

Acadia Parish (about 93,000 acres), and third largest in 

Jefferson Davis Parish (about 90,000 acres).

During 1999-2000, ground water in the ricegrowing area was used primarily for rice irrigation and 

public supply. The Chicot aquifer system supplied 

798 Mgal/d of ground water to the area. Of the total, 

537 Mgal/d was used for rice irrigation (Sargent, 2002) 

and 89 Mgal/d was used for public supply. Groundwater withdrawals for rice irrigation were largest in 

Vermilion Parish (149 Mgal/d), second largest in 

Jefferson Davis Parish (132 Mgal/d), and third largest 

in Acadia Parish (125 Mgal/d). All other parishes 

each used about 40 Mgal/d or less of ground water for 

irrigation. The top two parishes for public-supply use 

were Calcasieu (24 Mgal/d) and Lafayette (21 Mgal/d) 

Parishes, which, combined, accounted for more than 

50 percent of the total public-supply use. The Chicot 

aquifer system was not used for public supply in 

Avoyelles, Rapides, and Vernon Parishes. The 

remaining parishes each used 10 Mgal/d or less of 

ground water for public supply.

The rice-growing area is sparsely populated with 

the primary economic activity being agriculture. In 

2000, the total population of the area was about 500,000 

(U.S. Census Bureau, 2002). Lafayette Parish had the 

largest population (about 190,000), and Calcasieu Parish 

had the second largest population (about 175,000). All 

other parishes had populations of less than 100,000. 

Cameron Parish was the least populated and had less than 

10,000 people. The two largest cities were Lafayette, 

which had a population of about 116,000, and Lake 

Charles, which had a population of about 72,000.

METHODS

The NAWQA guidelines used to design this 

study are described in Gilliom and others (1995). 

NAWQA ground-water protocols (Lapham and 

others, 1997; Koterba, 1998) were followed during data 

collection. Standardization of the data-collection 

protocols was intended to produce a nationally 

consistent data base for statistically valid 

interpretations. However, because of local conditions, 

modification of the national protocols sometimes was 

necessary. The following sections describe how the 

protocols were applied and, when necessary, how they 

were modified.

System Series

Hydrogeologic units

Aquifer system or 

confining unit

Aquifers or confining units

Northern part of

study area

Lake Charles 

area

Rice-growing 

area

Quaternary Pleistocene

Chicot aquifer 

system or surficial 

confining unit

Shallow sands in 

confining unit

Shallow sands in 

confining unit Shallow sands in 

confining unit and 

undifferentiated 

sands 

“200-foot” sand Upper sand

“500-foot” sand 

“700-foot” sand

Tertiary Pliocene

Evangeline aquifer Miocene

Figure 2. Selected hydrogeologic units in southwestern Louisiana (modified from Lovelace and 

Lovelace, 1995, p. 10).

 Lower sand

?
30 MILES

0 30 KILOMETERS

0

Boundary f o the AcadianPontchartrain ACAD) ( Study Unit 6

Rice

Soybeans

Sugarcane

Cotton

Urban

Pasture

Forest

Wildlife ese pr rve

Marsh

Water

Aquaculture

EXPLANATION

Well location and number

Study a are

Figure 3. Major land-use types in the rice-growing area in southwestern Louisiana in the Acadian-Pontchartrain Study Unit.

24

1

13

22

24

26

17

16

8

5

18

6

9

3

19

15

4

23

25

11

30

28

10

27

14

2

21

7

Area Shown

Index Map

Acad Study 

Unit Boundary

Arkansas

Louisiana

iss s ipp

M

i s i

Texas

BEAUREGARD

VERNON

EVANGELINE

ALLEN

ST LANDRY

JEFFERSON

DAVIS

CALCASIEU

ACADIA

VERMLI ION IBERIA

ST. MARTIN

CAMERON

LAFAYETTE

RAPIDES

AVOYELLES

Map credit: Modified from, Official Map of Louisiana, Department of Transportation and Development, 1986

and-use L data

 (source: Joseph Holmes, Louisiana

 Department of Environmental Quality,

 written commun., 2001)

B N SA I E L E AK

A C IE L AS U C

LAKE

WHITE

LAKE

GRAND

LAKE

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7

Well-Site Selection

Well-site selection criteria followed the criteria 

published in Lapham and others (1997). The main 

criterion used for site selection was that the site be 

located on deposits that make up the Chicot aquifer 

system or surficial confining unit. Boundaries for the 

rice-growing area were obtained from the Louisiana 

State University Remote Sensing and Image Processing 

Laboratory. After the rice-growing area boundaries 

were determined, a computer-generated program 

(Scott, 1990) was used to divide the total rice area into 

30 equal-area cells. The program then randomly 

selected sites located in each of the 30 cells. A field 

inventory of the potential sites was conducted to 

determine the approximate percentage of rice farmland 

within a 500-1,640 ft radius of each site. The Louisiana 

State University Agricultural Center’s Rice Research 

Station in Crowley, La., then was contacted and asked to 

provide a list of landowners and rice farmers at or near 

the 30 sites. Letters were delivered to the landowners 

and rice farmers explaining the study and requesting 

permission to drill, install, and sample a well at that site. 

In a few cases, permission was not obtained to drill a 

well near the selected point; therefore, the search was 

expanded to nearby areas within the cell. A total of 

27 wells were drilled in the rice-growing area in 

southwestern Louisiana (fig. 3).

Well Installation and Development

Shallow wells were drilled and installed by 

USGS personnel using a drill rig. The 27 wells 

installed in the rice-growing area were drilled between 

April and October 1999 using hollow-stem augers. All 

wells were constructed according to NAWQA guidelines described in Lapham and others (1997) and 

according to Louisiana State regulations (Louisiana 

Department of Environmental Quality and Louisiana 

Department of Transportation and Development, 2000). 

All wells were constructed using 2-inch outsidediameter polyvinyl chloride (PVC) flush, threaded casing and 

screens. Annular spaces around the well screens were 

sand packed, and then the annular spaces above the 

screened intervals were sealed with bentonite and filled 

with cement to land surface to prevent downward 

migration of surficial fluids. Cuttings formed during 

the drilling process were inspected visually by USGS 

personnel to describe the lithology at each drill site. 

Drilling equipment was pressure washed and steam 

cleaned before being moved to the next drilling site to 

prevent potential cross contamination between wells.

After installation, all wells were developed using 

a combination of pumping and surging to remove as 

much sediment as possible. The developing tools 

consisted of an electrically operated pump, 5/8-inch 

high-density polyethylene (HDPE) tubing, a PVC foot 

valve, and a PVC surge block. The tubing, foot valve, 

and surge block were dedicated to individual wells to 

prevent possible cross contamination. Wells were 

developed until the discharged water cleared. 

Development times ranged from about 2 hours to as 

many as 15 hours depending on the lithology and 

hydrologic properties of the screened interval.

Well-Construction Data and Measurement of 

Water Levels

Construction data for the 27 wells installed and 

sampled for this study are shown in table 1. The wells 

ranged in depth from 12.25 to 92 ft below land surface 

and had a median depth of 26 ft. Water levels ranged 

from 0.57 to 80.19 ft below land surface. Borehole 

lithology was determined from visual inspection of 

drill cuttings obtained from above the screened waterbearing sediment. Interlayering and changes in 

sediment size occurred on scales ranging from inches 

to tens of feet. Sediment sizes consisted of clay, silt, 

sand, and some gravel. Borehole lithology generally 

indicated an increase in coarse sediments in the 

northern part of the study area and an increase in 

coarse sediments with depth. 

Sample Collection and Analysis

The 27 wells installed for this study were 

sampled from January through September 2000. All 

wells were sampled using a portable, stainless-steel 

submersible pump attached to a Teflon discharge line 

and Teflon-coated powerlines with stainless-steel 

fittings. Ground-water samples were collected and 

processed according to parts-per-billion-level 

protocols described in Koterba and others (1995). To 

minimize the risk of sample contamination, all sample 

collection and preservation took place in 

environmental chambers that consisted of clear 

polyethylene bags supported by a PVC frame that 

were dedicated for use at individual wells. The 

polyethylene bags that formed the sample-collection 

and -preservation chambers were replaced between 

each sample-collection site. After all samples were 

collected at a sample-collection site, sampling 

equipment was cleaned thoroughly using a 

progression of nonphosphate detergent wash, tapwater rinse, and deionized-water rinse. A final 

methanol rinse was used to clean the pesticide 

sampling equipment. All sampling equipment was 

stored in clean plastic bags or containers between 

sample-collection sites.
8

Table 1. Site information and well-construction data for selected shallow wells in the rice-growing area in southwestern Louisiana, 1999-2000[ACAD, Acadian-Pontchartrain Study Unit of the National Water-Quality Assessment Program; DOTD, Department of Transportation and Development; USGS, U.S. Geological 

Survey; NGVD 29, National Geodetic Vertical Datum of 1929; P, plastic; 112CHCT, Chicot aquifer, undifferentiated; 112CHCTC, Chicot aquifer system 

surficial confining unit; 112CHCTS, Chicot aquifer, shallow sand unit]

ACAD

well

number

DOTD local

well number

USGS site

identification

number

Date well

constructed

Water-level 

measurement

and sample

date

Landsurface 

elevation

above

NGVD 29

(feet)

Casing

material

Aquifer

code

Well

depth

(feet)

Casing 

diameter

(inches)

Water

level

(feet

below

land

surface)

Depth to

top of

screen

(feet)

Depth to

bottom of

screen

(feet)

Sample

depth

(feet)

1 AL-5475Z 303839092435101 08-03-99 05-02-00 82 P 112CHCT 78.5 2 66.10 68.5 78.5 682 EV-5477Z 303741092213901 08-17-99 01-27-00 56 P 112CHCTC 25 2 4.20 14.5 24.5 143 AL-5477Z 302927092490001 08-04-99 05-25-00 46 P 112CHCT 68 2 55.21 58 68 604 EV-5482Z 302952092325501 08-04-99 01-26-00 46 P 112CHCTS 20 2 3.11 14.5 19.5 145 JD-6843Z 302220092570201 08-02-99 01-11-00 27 P 112CHCTC 35.5 2 2.17 30 35 296 JD-6844Z 302246092400101 08-19-99 01-25-00 36 P 112CHCTS 21 2 12.53 15.5 20.5 157 JD-6834Z 301451092541401 06-08-99 01-12-00 20 P 112CHCTC 26 2 15.59 20.5 25.5 208 AC-7869Z 301444092211501 05-04-99 01-13-00 24 P 112CHCTC 37.6 2 24.56 32.1 37.1 279 JD-6845Z 301003092561301 08-10-99 01-18-00 10 P 112CHCTC 31 2 8.28 25.5 30.2 25

10 AC-7977Z 300659092352901 10-18-99 02-09-00 5 P 112CHCTC 29.9 2 4.92 19.4 29.4 1911 VE-10210Z 295531092132001 08-11-99 05-23-00 6 P 112CHCTC 24 2 20.15 18.5 23.5 2213 EV-5470Z 304121092293301 05-05-99 02-15-00 60 P 112CHCTC 19 2 8.98 13.5 18.5 1314 EV-5486Z 303616092331801 10-19-99 02-16-00 44 P 112CHCTS 21.8 2 11.02 16.3 21.3 1615 AL-5479Z 303127092404801 08-18-99 05-11-00 53 P 112CHCT 92 2 80.19 82 92 8316 SL-6706Z 303237092105501 04-29-99 02-01-00 59 P 112CHCTC 21.5 2 0.57 16 21 1617 AC-7934Z 302821092171001 08-05-99 02-03-00 50 P 112CHCTC 27 2 2.50 21.5 26.5 2118 JD-6909Z 302448092510501 10-05-99 05-09-00 40 P 112CHCTS 86 2 65.69 76 86 7519 AC-7935Z 302132092234401 08-12-99 01-19-00 36 P 112CHCTC 26.5 2 4.61 16 26 1521 JD-6835Z 301525092425701 06-09-99 05-10-00 22 P 112CHCTC 23 2 13.68 18 23 1722 AC-7936Z 301906092272401 08-17-99 01-09-00 32 P 112CHCTC 30 2 9.87 19.5 29.5 1923 AC-7976Z 301042092211101 09-09-99 02-17-00 21 P 112CHCTC 23.7 2 6.48 13.2 23.2 1224 JD-6846Z 300626092462901 08-25-99 09-21-00 16 P 112CHCTS 74 2 60.10 64 74 6325 AC-7938Z 300614092233001 08-11-99 02-10-00 17 P 112CHCTC 21 2 4.23 15.5 20.5 1526 CN-5863Z 300216093042301 05-13-99 01-10-00 8 P 112CHCTS 12.25 2 2.93 6.75 11.75 627 VE-10211Z 295932092284401 08-10-99 02-08-00 7 P 112CHCTC 25.5 2 3.69 20 25 2028 JD-6847Z 301737093010301 08-09-99 01-11-00 27 P 112CHCTC 25 2 7.34 19.5 24.5 1930 BE-6230Z 302723093144201 05-27-99 09-28-00 70 P 112CHCTC 53 2 39.22 42.5 52.5 43
9

Before sample collection, the wells were purged 

of three casing volumes to remove stagnant water so 

that a sample representative of ground water in the 

aquifer could be obtained. After the stagnant water 

was removed, specific conductance, pH, temperature, 

and dissolved oxygen were measured about every 

5 minutes in a flow-through chamber until stable 

readings were obtained. Turbidity also was measured 

using a portable turbidity meter. After stable readings 

were obtained for the physical properties, water was 

redirected to the clean sampling chamber where whole 

water and filtered samples were collected immediately. 

Whole water samples were analyzed for total 

constituents. Filtered samples were obtained by 

passing whole water through a 0.45-micrometer filter 

into the appropriate bottle. Filtered water was 

analyzed for dissolved constituents. Most groundwater samples were chilled and shipped to the USGS’s 

National Water Quality Laboratory (NWQL) in 

Lakewood, Colo., for analysis. CFC and selected 

stable-isotope samples were analyzed at the USGS 

Laboratory in Reston, Va. Methods used to analyze 

the water samples are given in table 2.

Quality-Control Data Analysis

Quality-control (QC) data were collected to test 

sample-collection, sample-processing, and laboratoryanalysis procedures. QC samples collected included fieldblank samples, replicate environmental samples, and fieldand laboratory-spiked samples (Mueller and 

others, 1997). Field-blank samples were collected to 

verify that cleaning procedures were sufficient and that 

collection and analysis procedures did not contaminate the 

samples. Replicate environmental samples were collected 

to assess the effects of sample-collection and laboratoryanalysis procedures on measurement variability. The 

spiked samples (field and laboratory) were environmental 

samples that were injected with a known concentration of 

the analyte(s) of interest to determine the accuracy and 

precision of organic analyses, the stability of analytes 

during typical holding times, and whether characteristics 

of the environmental samples might interfere with the 

analysis of the analytes.

Field-blank samples were collected and 

analyzed at three wells for concentrations of major 

inorganic ions, trace elements, nutrients, DOC, and 

Table 2. Methods used to analyze ground-water samples from selected shallow wells in the rice-growing area 

in southwestern Louisiana

[AA, Atomic absorption spectrometry; IC, Ion-exchange chromatography; ICP, Inductively-coupled plasma; MS, mass spectrometry; 

UV, ultraviolet; C, carbon; ECD, electron capture detector; 2H, deuterium; 1H, hydrogen; 18O, oxygen-18; 16O, oxygen-16] 

Constituent Analytical method Reference

Major inorganic ions AA, Colorimetry, or ICP Fishman and Friedman (1989) and

Fishman (1993)

Trace elements AA or ICP-MS Faires (1993), Garbarino (1999), and McLain (1993)

Nutrients Colorimetry Fishman (1993), Patton and Truitt (2000), and U.S. 

Environmental Protection Agency (1993)

Dissolved organic carbon UV-persulfate oxidation and infrared spectrometry Brenton and Arnett (1993)

Pesticides and degradation 

products

Solid-phase extraction using a C-18 cartridge and gas 

chromatography/mass spectrometry

Determination of low concentrations of acetochlor in water 

by automated solid-phase extration and gas 

chromatography with mass selective detetection

Graphitized carbon-based solid-phase extraction and 

high-performance liquid chromatography/mass 

spectrometry

Zaugg and others (1995)

Lindley and others (1996)

Furlong and others (2001)

Volatile organic compounds Purge and trap capillary gas chromatography/mass 

spectrometry

Rose and Schroeder (1995)

Radon Liquid scintillation American Society for Testing and Materials (1996)

Chlorofluorocarbons Gas chromatography with electron capture detector Busenberg and Plummer (1992)

2H/1H Hydrogen equilibrium and mass spectrometry Coplen and others (1991)

18O/16O Carbon dioxide equilibrium and mass spectrometry Epstein and Mayeda (1953)
10

pesticides. The source solution for the field-blank 

samples was organic-free or inorganic-free water 

passed through all sampling equipment in the field 

and placed in the appropriate bottles. Few waterquality constituents analyzed for were detected in the 

field-blank samples. Major inorganic ion and DOC 

concentrations were less than the analytical reporting 

limits and most trace-element concentrations were at 

or less than the analytical reporting limits. Copper 

concentrations in two field-blank samples were 3.1 

and 3.9 μg/L, slightly greater than the analytical 

reporting limits and greater than the concentrations in 

most of the environmental samples. No nutrients or 

pesticides were detected in the field-blank samples. 

Results of the field-blank sample analyses indicated 

cleaning procedures were adequate to prevent onsite 

and site-to-site contamination.

Replicate environmental samples were collected at four wells and analyzed for concentrations of 

all constituents. The relative percent difference 

between the environmental sample and the corresponding replicate sample was calculated by multiplying 100 times the absolute value of the difference in 

replicate concentrations and dividing by the summation of replicate concentrations. The relative percent 

difference between the environmental samples and 

the corresponding replicate samples was less than 

5 percent for all constituents except potassium 

(6 percent), fluoride (8 percent), bromide (13 percent), nitrogen as ammonia (6 percent), and nitrogen 

as ammonia plus organic nitrogen (8 percent). Results 

of the replicate environmental sample analyses indicated an acceptable degree of laboratory precision and 

data collection reproducibility.

Field- and laboratory-spiked samples were 

collected from one well that best represented the 

average water conditions for all wells. Spike 

solutions that contained known amounts of pesticides 

were added to two replicate environmental samples in 

the field and to two environmental samples at the 

NWQL. The field-spiked samples were evaluated for 

47 compounds, and the laboratory-spiked samples 

were evaluated for 107 compounds. Mean recovery 

of pesticides from the field-spiked and field-spiked 

replicate samples ranged from 63 to 104 percent. 

Mean recovery of pesticides from the laboratoryspiked and laboratory-spiked replicate samples was 

within the NWQL control limits. Results of the 

spiked-sample analyses indicated sampling and 

analysis procedures adequately detected the pesticides 

analyzed for and no major matrix interferences 

existed.

QUALITY OF WATER FROM SHALLOW 

WELLS IN THE RICE-GROWING AREA 

The quality of water from the 27 shallow wells 

screened in the Chicot aquifer or surficial confining unit 

in the rice-growing area is presented in this section. The 

water-quality data are grouped by type (appendixes 1-7, at 

the back of the report): general ground-water properties; 

dissolved solids and major inorganic ions; trace elements; 

nutrients and DOC; pesticides and pesticide degradation 

products; and radon, CFCs, and selected stable isotopes.

The ground-water quality is discussed in the 

following sections in relation to USEPA drinking-water 

standards established for physical properties and 

chemical constituents that might have adverse effects on 

human health or affect the odor, appearance, or 

desirability of water (U.S. Environmental Protection 

Agency, 2002b). Although the shallow wells installed for 

this study are not used for a drinking-water source, 

concentrations of selected ground-water constituents in 

the water were compared to the USEPA Maximum 

Contaminant Levels (MCLs) and Secondary Maximum 

Contaminant Levels (SMCLs) to provide a frame of 

reference. An MCL is the maximum permissible level for 

a contaminant in drinking water that is delivered to any 

user of a public-water system, and an SMCL is a 

nonenforceable Federal guideline regarding aesthetic 

effects, such as taste or odor of drinking water, or 

cosmetic effects, such as tooth or skin coloration, caused 

by drinking water.

General Ground-Water Properties

Data for seven general ground-water properties 

(specific conductance, pH, air and water temperature, 

turbidity, dissolved oxygen, and alkalinity) were collected 

(appendix 1, at the back of the report). Measurements of 

the properties were made at the time of sample collection. 

The data were used to estimate ground-water conditions, 

such as clarity, redox state, acidity, salt content, and 

buffering capacity, at the time of sample collection.

A statistical summary for the ground-water 

properties is listed in table 3 along with applicable waterquality standards. The median value for specific 

conductance was 1,020 μS/cm, and values ranged from 

227 to 3,160 μS/cm. The SMCL for pH is 6.5 to 

8.5 standard units (U.S. Environmental Protection 

Agency, 2002b). Values for 5 of the 27 wells sampled 

were less than 6.5 standard units. The median value for 

turbidity was 2.0 NTU, and values for nine wells 

exceeded the MCL of 5.0 NTU (U.S. Environmental 

Protection Agency, 2002b). Dissolved oxygen 

concentrations were less than 1.0 mg/L in water from 
11

Table 3. Summary statistics for general ground-water properties, dissolved solids, major inorganic ions, trace 

elements, nutrients, and dissolved organic carbon in water from selected shallow wells in the rice-growing area 

in southwestern Louisiana, 2000

[Concentrations are dissolved unless noted. MCL, Maximum Contaminant Level; SMCL, Secondary Maximum Contaminant Level; oC, degrees Celsius; 

μS/cm, microsiemens per centimeter at 25o

C; ---, no value available; NTU, nephelometric turbidity units; mg/L, milligrams per liter; E, estimated; μg/L, 

micrograms per liter; ND, not detected; <, less than]

Property or constituent

Number of 

detections/

number of 

samples

Analytical 

reporting 

level

Median 

of all 

samples

Minimum 

detection

Maximum 

detection

Federal guideline 

or standarda

 MCL SMCL

Number

of values

or concentrations

exceeding

drinkingwater

standard

General ground-water properties

Specific conductance, 25°C, in μS/cm 27/27 1 1,020 227 3,160 --- --- ---

pH, in standard units 27/27 0.1 7.1 6.1 7.4 --- 6.5-8.5 b5

Air temperature, in °C 27/27 1 21.0 9.0 33.0 --- --- ---

Water temperature, in °C 27/27 0.1 21.5 17.0 27.1 --- --- ---

Turbidity, in NTU 27/27 1.0 2.0 0 110 5.0 --- 9

Dissolved oxygen, in mg/L 26/26 0.1 1.4 0.5 3.2 --- --- ---

Alkalinity as CaCO3, in mg/L 27/27 1 320 39 550 --- --- ---

Dissolved solids and major inorganic ions, in mg/L

Dissolved solids, residue on 

evaporation, 180°C

27/27 10 578 180 1,850 --- 500 17

Calcium, as Ca 27/27 0.01 71 8.2 140 --- --- ---

Magnesium, as Mg 27/27 0.01 30 3.8 61 --- --- ---

Sodium, as Na 27/27 0.10 93 20 410 --- --- ---

Potassium, as K 27/27 0.1 1.3 0.6 3.9 --- --- ---

Bicarbonate, (calculated) 27/27 1 388 48 666 --- --- ---

Sulfate, as SO4 27/27 0.30 16 E0.3 270 --- 250 1

Chloride, as Cl 27/27 0.30 120 12 830 --- 250 7

Fluoride, as F 25/27 0.1 0.4 0.1 0.7 4.0 2.0 0

Bromide, as Br 27/27 0.03 0.4 0.1 2.2 --- --- ---

Silica, as SiO2 27/27 0.13 28 20 74 --- --- ---

Trace elements, in μg/L

Aluminum, as Al 14/27 1.0 1 1 20 --- 50-200 0

Antimony, as Sb 0/27 0.048 ND ND ND 6 --- 0

Arsenic, as As 12/27 0.18 3 E1 4 10 --- 0

Barium, as Ba 27/27 1.0 220 16 850 2,000 --- 0

Beryllium, as Be 0/27 0.06 ND ND ND 4 --- 0

Boron, as B 11/11 7.0 30 10 60 --- --- ---

Cadmium, as Cd 0/27 0.037 ND ND ND 5 --- 0

Chromium, as Cr 11/27 0.8 1 E1 2 c

100 --- 0

Cobalt, as Co 5/27 0.015 1.5 1.1 3.4 --- --- ---

Copper, as Cu 10/27 0.23 3.5 1 11 d

1,300 1,000 0

Iron, as Fe 16/27 10 ND 10 6,500 --- 300 3

Lead, as Pb 0/27 0.08 ND ND ND 15 --- 0
12

a

 U.S. Environmental Protection Agency, 2002b.

bNumber of values less than 6.5 standard units.

c

Total concentration.

dU.S. Environmental Protection Agency Maximum Contaminant Level Goal (MCLG).

e

Under review.

Trace elements, in μg/L (continued)

Lithium, as Li 11/11 0.30 20 0 60 --- --- ---

Manganese, as Mn 25/27 2.2 100 E2 740 --- 50 15

Mercury, as Hgd 1/26 0.011 <0.3 E0.2 E0.2 2 --- 0

Molybdenum, as Mo 15/27 0.2 3 1 9 --- --- ---

Nickel, as Ni 23/27 0.06 3 1 8 --- --- ---

Selenium, as Se 8/27 0.33 6 1 29 50 --- ---

Silver, as Ag 0/27 1.0 ND ND ND --- 100 0

Strontium, as Sr 11/11 0.08 180 20 430 --- --- ---

Thallium, as Tl 0/11 0.041 ND ND ND 2 --- 0

Uranium, as U 16/27 0.018 5.2 1.8 16 e

20 --- 0

Vanadium, as V 8/11 0.21 3.5 1.2 6.7 --- --- ---

Zinc, as Zn 14/27 1.0 2 1 6 --- 5,000 0

Nutrients and dissolved organic carbon, in mg/L

Ammonia, as N 14/27 0.041 0.04 0.02 0.84 --- --- ---

Ammonia plus organic nitrogen, as N 14/27 0.10 E0.06 E0.06 0.99 --- --- ---

Nitrite plus nitrate, as N 13/27 0.047 0.87 0.05 13 10 --- 1

Nitrite, as N 0/27 0.008 --- --- --- 1.0 --- ---

Phosphorus, as P 26/27 0.0044 0.05 E0.01 0.48 --- --- ---

Orthophosphorus, as P 25/27 0.018 0.05 0.02 0.45 --- --- ---

Dissolved organic carbon, as C 24/26 0.33 E0.5 E0.2 1.4 --- --- ---

Property or constituent

Number of 

detections/

number of 

samples

Analytical 

reporting 

level

Median 

of all 

samples

Minimum 

detection

Maximum 

detection

Federal guideline 

or standarda

 MCL SMCL

Number

of values

or concentrations

exceeding

drinkingwater

standard

Table 3. Summary statistics for general ground-water properties, dissolved solids, major inorganic ions, trace 

elements, nutrients, and dissolved organic carbon in water from selected shallow wells in the rice-growing area 

in southwestern Louisiana, 2000--Continued
13

10 of the 26 wells sampled and ranged from 0.5 to 3.2 mg/L 

(appendix 1, at the back of the report). The alkalinity, as 

CaCO3, of the water ranged from 39 to 550 mg/L. Values 

for pH, specific conductance, and alkalinity were typical for 

the Chicot aquifer (Nyman, 1989).

Dissolved Solids and Major Inorganic Ions

The dissolved-solids and major inorganic ion 

concentrations for the 27 wells sampled are listed in 

appendix 2 (at the back of the report). A statistical 

summary for the dissolved solids and major inorganic ions 

is listed in table 3 with applicable water-quality standards. 

Dissolved solids are an important indicator of water quality 

and, in uncontaminated ground water, are the result of 

natural dissolution of rocks and minerals. Dissolved solids 

also are an important indicator of the suitability of water for 

drinking, irrigation, and industrial use. The dissolvedsolids concentrations for the 27 wells sampled ranged from 

180 to 1,850 mg/L and had a median of 578 mg/L, slightly 

greater than the 500-mg/L SMCL (U.S. Environmental 

Protection Agency, 2002b). Water from 17 wells had 

dissolved-solids concentrations that were greater than the 

SMCL. Although ground water containing more than 

500 mg/L dissolved solids is undesirable for drinking water 

and irrigation, it is used in many areas where lessmineralized water is not available.

Major inorganic ions were the primary constituents 

of dissolved solids in water from the 27 wells (appendix 2, 

at the back of the report). The major inorganic ions 

consisted of the positively charged cations--calcium, 

magnesium, sodium, and potassium; the negatively charged 

anions--bicarbonate, sulfate, chloride, fluoride, and 

bromide; and one uncharged ion--silica. The 250-mg/L 

SMCL for sulfate (U.S. Environmental Protection Agency, 

2000b) was exceeded in water from one well, and the 250-

mg/L SMCL for chloride was exceeded in water from seven 

wells (table 3).

Water types were classified by the percentages of 

major inorganic ions in the water. Because the potassium 

concentrations were low, those concentrations were 

added to the sodium concentrations before the water 

types were classified. Water types were classified as 

mixed cation mixed anion (18 wells), mixed cation 

bicarbonate (5 wells), mixed cation chloride (2 wells), 

and sodium mixed anion (2 wells). Mixed cation types 

had two or more cations for which the percent of each 

was greater than 20 percent of the total cations. Mixed 

anion types had two or more anions for which the 

percent of each was greater than 20 percent of the total 

anions. The mineral ratios (percentages), in 

milliequivalents per liter, of the cations (calcium, 

magnesium, and sodium plus potassium) and anions 

(bicarbonate, sulfate, and chloride plus fluoride) are 

shown in figure 4 (Hem, 1985). Sodium was the highest 

percentage cation in 20 wells, calcium was the highest in 

6 wells, and magnesium was the highest in 1 well. 

Bicarbonate was the highest percentage anion in 

20 wells, and chloride was the highest in 7 wells. Sulfate 

concentrations were low in most of the ground-water 

samples. The highest percentage cation and the highest 

percentage anion for each well are shown in figure 5. 

The many different water types in the study area reflect 

the high degree of lithologic variation in the shallow 

sediments of southwestern Louisiana.

Trace Elements

The trace-element concentrations in water from the 

27 wells sampled are listed in appendix 3 (at the back of the 

report). A statistical summary for the trace elements is 

listed in table 3 with 16 established and 2 proposed USEPA 

drinking-water standards. Trace elements occur naturally 

in water at concentrations of less than 1,000 mg/L 

(Drever, 1988, p. 326). Most of the trace elements detected 

in ground water are metals or semimetallic elements produced from the weathering of minerals. Concentrations of 

all trace elements detected in this study, except iron, were 

less than 1,000 mg/L (appendix 3, at the back of the 

report), and most were less than the drinking-water standards. Of the 24 trace elements analyzed for, 6 (antimony, 

beryllium, cadmium, lead, silver, and thallium) were not 

detected in the ground-water samples. Barium was the 

only trace metal detected in water from all 27 wells. The 

barium concentrations ranged from 16 to 850 mg/L and 

had a median of 220 mg/L (table 3). All barium concentrations were less than the SMCL of 2,000 mg/L (U.S. Environmental Protection Agency, 2002b). The maximum iron 

concentration was 6,500 mg/L, and concentrations for 

three wells exceeded the SMCL of 300 mg/L (U.S. Environmental Protection Agency, 2002b). Manganese concentrations for 15 wells exceeded the SMCL of 50 mg/L, 

and the maximum concentration was 740 mg/L. Mercury 

was detected in water from one well, and the estimated 

concentration for that well was 0.2 mg/L.

Nutrients

The nutrient concentrations in water from the 27 

wells sampled are listed in appendix 4 (at the back of the 

report). A statistical summary for the nutrients is listed in 

table 3 with applicable water-quality standards. Nutrients 

are nitrogen- or phosphorus-containing compounds that are 

necessary for plant growth and important for animal 

nutrition (Mueller and others, 1995). Although these 

compounds do occur naturally, concentrations in ground or 

surface water can be increased through human activities 

such as fertilizer applications, sewerage and septic effluent, 
14

and atmospheric deposition from industrial emissions. 

Excessive nutrient concentrations may cause adverse 

human-health effects, such as methemoglobinemia (blue 

baby syndrome) (Hem, 1985, p. 125), and excessive 

nitrogen and phosphorus concentrations may cause 

adverse environmental effects, such as eutrophication of 

surface-water bodies (Hem, 1985, p. 126-128). Nitrite 

and nitrate concentrations in uncontaminated water 

usually are relatively small (generally less than 2 mg/L), 

and larger concentrations of several milligrams per liter 

indicate possible contamination from human activities 

(Mueller and Helsel, 1996).

Nutrient concentrations for three wells were 

greater than 2 mg/L (appendix 4, at the back of the 

report). Ammonia and ammonia plus organic nitrogen 

each were detected in water from 14 (52 percent) of the 

27 wells sampled. Ammonia concentrations ranged from 

0.02 to 0.84 mg/L. The median ammonia plus organic 

nitrogen concentration was an estimated 0.06 mg/L 

(table 3). The nitrite plus nitrate concentration for one 

well was 13 mg/L which exceeded the MCL of 10 mg/L 

(U.S. Environmental Protection Agency, 2002b), and was 

the only nutrient concentration that was greater than the 

drinking-water standard. The nitrite concentration for 

the same well was less than 0.01 mg/L (appendix 4, at 

the back of the report), so all of the nitrite plus nitrate 

was assumed to be nitrate. The elevated nitrate concentration can be attributed to a previous land use in the area 

(chicken and pig yard), and, thus, may not be attributed 

to rice-growing practices. Nitrite was not detected in any 

of the ground-water samples. Phosphorus and orthophosphorus concentrations ranged from 0.01 mg/L (an 

estimated value) to 0.48 mg/L and had medians of 

0.05 mg/L (table 3).

Figure 4. Percentages of major inorganic ions in water from selected shallow wells in the rice-growing 

area in southwestern Louisiana, 2000.

0

20

40

60

80

100

1 2 3 4 5 6 7 8 9 10 11 13 14 15 16 17 18 19 21 22 23 24 25 26 27 28 30

100

80

60

40

20

Map number (see fig. 5)

Sodium plus potassium

Magnesium

Calcium

Chloride plus fluoride

Sulfate

Bicarbonate

EXPLANATION

WELL NUMBER

Cations Anions

PERCENTAGE OF MILLIEQUIVALENTS PER LITER
30 MILES

0 30 KILOMETERS

0

Well location and number 24

Boundary f o the AcadianPontchartrain ACAD) ( Study Unit

sodium plus potassium

calcium

magnesium

bicarbonate

chloride plus fluoride

Highest percentage cation or anion

Urban

Water

R ci e

Study a are

EXPLANATION

Figure 5. Highest percentage cations and anions in water from selected shallow wells in the rice-growing area in southwestern Louisiana, 2000.

Lake

Charles

Jennings Crowley

Oberlin

Lafayette

Lake

Arthur

Area Shown

Index Map

ACAD Study 

Unit Boundary

Arkansas

Louisiana

s ipp

Missi s i

Texas

BEAUREGARD

VERNON

EVANGELINE

ALLEN

ST LANDRY

JEFFERSON

DAVIS

CALCASIEU

ACADIA

VERMLI ION IBERIA

ST. MARTIN

CAMERON

LAFAYETTE

RAPIDES

AVOYELLES

B N SA I E L E AK

A C IE L AS U C

LAKE

WHITE

LAKE

GRAND

LAKE

S

CAL

A

I

U

C

E

R

RIVE

des

annes C

t Me men au r

i er R v

B

yo a u

AFALAY

ATCH

A

R ER IV

UEUE

Q

DE

O

T

E

T

R

U

o B y u a

ez i e N

p qu

ER D

ER

RIV

u on Ho st

River

VERMILION

BAY WEST COTE

BLANCHE BAY

V n ermilio

v r Ri e

Teche

BA OU Y

b n Sa e i Riv r e

GU F OF M XICO L E

92° 00 ́

9 2° 30 ́ 93° 00 ́

9 3° 30 ́

3 00 0°  ́

3 30 0°  ́

3 00 1°  ́

yo B u a

CALCASIEU

RIVER

y B u a o

c i a ass ne L

1

13

22

24

26

17

16

8

5

18 6

9

3

19

15

4

23

25

11

30

28

10

27

14

2

21

7

Map credit: Modified from, Official Map of Louisiana, Department of Transportation and Development, 1986

15

and-use L data

 (source: Joseph Holmes, Louisiana

 Department of Environmental Quality,

 written commun., 2001)
16

Dissolved Organic Carbon

The amount of organic carbon present in 

ground water can have a substantial effect on microbial communities in an aquifer and, in turn, affect the 

concentration of redox-sensitive species such as dissolved oxygen, trace elements, and nutrients. DOC 

was measured for 26 wells, and all concentrations 

were less than or equal to 1.4 mg/L (appendix 4, at 

the back of the report). DOC concentrations ranged 

from 0.2 mg/L (an estimated value) to 1.4 mg/L and 

had an estimated median of 0.5 mg/L (table 3). 

According to Drever (1997, p. 107), DOC concentrations of about 0.5 mg/L typically occur naturally in 

ground water, and concentrations can increase with 

human activity. The median concentration of 

0.5 mg/L in water from wells in this study probably 

indicates naturally-occurring DOC conditions.

Pesticides

Pesticides are chemicals used to control 

unwanted vegetation, insects, and fungi. They are 

applied primarily to cropland in rural areas but also 

are used on lawns, gardens, and rights-of-way. The 

widespread use of pesticides creates the potential for 

the movement of pesticides or their degradation 

products into shallow ground water. The presence of 

pesticides in ground water indicates an impact from 

human activities on ground-water quality and is a 

human-health concern for those using ground water as 

a drinking-water supply.

Pesticides were detected in water from 14 of the 

27 wells sampled (fig. 6). One compound was 

detected in water from eight wells, and two compounds 

were detected in water from three wells. Water from 

the remaining three wells had three, four, or six 

detected compounds. The maximum concentration for 

the pesticides and pesticide degradation products was 

an estimated value of 0.704 μg/L (imazaquin), and all 

concentrations were less than the drinking-water standards (U.S. Environmental Protection Agency, 2002b). 

Of the 92 pesticides analyzed for (appendix 5, at the 

back of the report), 13 were detected in the groundwater samples; and, of the 17 degradation products 

analyzed for (appendix 6, at the back of the report), 7 

were detected in the ground-water samples (fig. 7). Of 

the pesticides detected, four commonly were used on 

rice crops in the study area (Dr. J.K. Saichuk, Louisiana State Cooperative Extension Service, oral 

commun., 2000). Bentazon, 2,4-D, and molinate (three 

rice herbicides) were detected in water from four, one, 

and one wells, respectively, and malathion (a rice 

insecticide) was detected in water from one well. Two 

rice insecticide degradation products (fipronil RPA and 

fipronil sulfone) were detected in water from one well 

(well 26), but no concentrations of these fipronil degradation products were detected upon resampling. Only 

two insecticides (diazinon and malathion), one herbicide (atrazine), one herbicide degradation product 

[3 (4-chlorophenyl)-1-methyl urea], and one insecticide degradation product (fipronil sulfone) had concentrations that were greater than estimated values. Of the 

20 compounds detected, only four--bentazon, imazaquin, p,p’-DDE, and deethyldeisopropylatrazine--were 

detected in water from more than one well. Bentazon, 

which was detected in 4 (15 percent) of the 27 wells 

sampled, was the most frequently detected pesticide 

and had an estimated maximum concentration of 

0.15 μg/L (table 4).

In water from one well (well 11), the 

concentration of atrazine (0.008 μg/L) was slightly 

greater than the concentration of deethylatrazine 

(estimated 0.007 μg/L), one of its degradation products. 

A greater concentration of the parent product than of the 

degradation product might indicate the parent product 

was recently input into the environment (Townsend and 

Young, 1999). Concentrations of selected nutrients 

(nitrite plus nitrate, phosphorus, and orthophosphorus) 

and DOC were slightly greater in water from well 11 

than in water from most of the other wells. The greater 

concentrations of selected nutrients, DOC, and pesticides 

indicated agricultural or domestic activities had an effect 

on the quality of water from well 11; however, all 

concentrations of constituents in the water from well 11 

were much less than the drinking-water standards (U.S. 

Environmental Protection Agency, 2002b). The 

presence of rice and other pesticides in the shallow 

ground water indicates the hardpan beneath the rice 

fields is not preventing downward movement in all areas.

Radon

Radon is a naturally-occurring radioactive 

element that produces a radioactive isotope, radon-222, 

as a gas. Radon is a byproduct of the natural decay of 

uranium that is present in small quantities in certain 

rock and sediment types. Radon gas is soluble in 

water and is transported in ground water. The USEPA 

has an MCL for radon in ground water of 300 pCi/L 

for states without a Multimedia Mitigation (MMM) 

program and an Alternate Maximum Contaminant 

Level (AMCL) of 4,000 pCi/L for states with an 

MMM program (U.S. Environmental Protection 

Agency, 2002b). When radon gas is exposed to air, 

such as when ground water is pumped from an aquifer 

and used for indoor use, the radon diffuses into the air 
30 MILES

0 30 KILOMETERS

0

Well location and number 24

Boundary f o the AcadianPontchartrain ACAD) ( Study Unit

17

Urban

Water

Rice

Study a are

EXPLANATION

1

2

3

4

6

no s pe ticides detected

Number f o pesticides detected:

Figure 6. Number of pesticide and pesticide degradation products detected in water from selected shallow wells in the rice-growing area in 

southwestern Louisiana, 2000.

Lake

Charles

Jennings Crowley

Oberlin

Lafayette

Lake

Arthur

Area Shown

Index Map

ACAD Study 

Unit Boundary

Arkansas

Louisiana

s ipp

Missi s i

Texas

BEAUREGARD

VERNON

EVANGELINE

ALLEN

ST LANDRY

JEFFERSON

DAVIS

CALCASIEU

ACADIA

VERMLI ION IBERIA

ST. MARTIN

CAMERON

LAFAYETTE

RAPIDES

AVOYELLES

B N SA I E L E AK

A C IE L AS U C

LAKE

WHITE

LAKE

GRAND

LAKE

S

CAL

A

I

U

C

E

R

RIVE

des

annes C

t Me men au r

i er R v

B

yo a u

AFALAY

ATCH

A

R ER IV

UEUE

Q

DE

O

T

E

T

R

U

o B y u a

ez i e N

p qu

ER D

ER

RIV

u on Ho st

River

VERMILION

BAY WEST COTE

BLANCHE BAY

V n ermilio

v r Ri e

Teche

BA OU Y

b n Sa e i Riv r e

GU F OF M XICO L E

92° 00 ́

9 2° 30 ́ 93° 00 ́

9 3° 30 ́

3 00 0°  ́

3 30 0°  ́

3 00 1°  ́

yo B u a

CALCASIEU

RIVER

y B u a o

c i a ass ne L

1

13

22

24

26

17

16

8

5

18

6

9

3

19

15

4

23

25

11

30

28

10

27

14

2

21

7

Map credit: Modified from, Official Map of Louisiana, Department of Transportation and Development, 1986

Land-use ata d

 (source: Joseph Holmes, Louisiana

 Department of Environmental Quality,

 written commun., 2001)
18

Table 4. Concentrations of pesticide and pesticide degradation products in water from selected shallow 

wells in the rice-growing area in southwestern Louisiana, 2000 

 [All concentrations are in micrograms per liter. MCL, Maximum Contaminant Level; E, estimated; ---, no value available; HA, Health Advisories 

established by U.S. Environmental Protection Agency] 

a

 U.S. Environmental Protection Agency, 2002b.

Pesticide or pesticide

degradation product

Number of

detections/

number of

samples

Analytical

reporting

level

Minimum

detection

Maximum

detection

Drinkingwater

standard

Type of

standard

Number of

concentrations

exceeding

drinkingwater

standard

Atrazine 1/28 0.001 0.008 0.008 3 MCLa 0

Bentazon 4/28 0.02 E0.01 E0.15 --- --- ---

Chlorimuronethyl 1/28 0.37 E0.008 E0.008 --- --- ---

Chlorpyrifos 1/28 0.004 E0.004 E0.004 --- --- ---

2,4-D 1/28 0.08 E0.01 E0.01 70 MCLa 0

Diazinon 1/28 0.002 0.007 0.007 --- --- ---

Diuron 1/28 0.08 E0.0007 E0.0007 10 HAa 0

Flumetsulam 1/28 0.866 E0.0437 E0.0437 --- --- ---

Imazaquin 2/28 0.103 E0.015 E0.704 --- --- ---

Malathion 1/28 0.005 0.006 0.006 --- --- ---

Metalaxyl 1/28 0.057 E0.005 E0.005 --- --- ---

Molinate 1/28 0.004 E0.003 E0.003 --- --- ---

Tebuthiuron 1/28 0.010 E0.008 E0.008 --- --- ---

p,p'-DDE (DP of DDT) 2/28 0.006 E0.001 E0.002 --- --- ---

Deethylatrazine (DP of atrazine) 1/28 0.002 E0.008 E0.008 --- --- ---

Deethyldeisopropylatrazine

(DP of atrazine)

3/28 0.06 E0.004 E0.02 --- --- ---

Fipronil RPA (DP of fipronil) 1/28 0.005 E0.001 E0.001 --- --- ---

Fipronil sulfone (DP of fipronil) 1/28 0.001 0.005 0.005 --- --- ---

2-Hydroxyatrazine

(DP of atrazine)

1/28 0.193 E0.066 E0.066 --- --- ---

3 (4-chlorophenyl)-1-methyl urea

(DP of neburon)

1/28 0.915 0.2056 0.2056 --- --- ---
19

Figure 7. Frequency of pesticides and pesticide degradation products in water from selected shallow wells 

in the rice-growing area in southwestern Louisiana, 2000.

where it can be inhaled. Only about 1 to 2 percent of 

radon in indoor air comes from drinking water

(U.S. Environmental Protection Agency, 2002a). 

Although the entire State of Louisiana is classified in 

the lowest national risk zone, Zone 3 (Louisiana 

Department of Environmental Quality, 1990), for 

radon, a 1990 survey of Louisiana homes indicated 10 

of 1,314 homes had elevated levels (greater than 

4 pCi/L) of radon in the indoor air.

Radon-222 (radon) was detected in water from 

24 of the 27 wells sampled (appendix 7, at the back of 

the report). The minimum radon concentration in the 

ground-water samples was 216 pCi/L, and the maximum 

radon concentration was 1,450 pCi/L (fig. 8). The 

median radon concentration was 800 pCi/L, and the 25th 

and 75th percentiles occurred at 456 and 961 pCi/L, 

respectively (fig. 8). Radon concentrations for 22 of 

the 24 wells were at or greater than the MCL and all were 

less than the AMCL (fig. 9) (U.S. Environmental 

Protection Agency, 2002b). The effects that the elevated 

radon concentrations in ground water might have on 

domestic and public-water supplies and on indoor air 

quality are unknown. 

Chlorofluorocarbons (Apparent Age of Ground 

Water)

CFCs were used to estimate the apparent age of 

water in 21 of the 27 wells sampled (appendix 7). CFCs 

are stable, synthetic organic compounds developed in the 

early 1930’s to replace ammonia and sulfur dioxide in the 

refrigeration process (Plummer and Friedman, 1999). 

Production of dichlorodifluoromethane (CFC-12) began 

in 1931 and was followed by production of trichlorofluoromethane (CFC-11) in 1936. Many other CFCs have 

been produced since that time. The presence of measurable concentrations of CFCs in a water sample indicates 

the sample contains some water that was recharged after 

1940 (post-1940 water). Chemical processes, such as 

microbial degradation and sorption during transit, and 

physical processes, such as mixing with older water, can 

affect the concentration of CFCs; thus, the term apparent 

is used to qualify the age term. The apparent age of water 

from the 21 wells ranged from about 17 to 49 years 

(fig. 10) and had a median of 38 years. The apparent ages 

indicated the water in the 21 wells was recharged 

sometime since the 1940’s and contaminants transported 

with recharge water might not be detected for several 

years or decades in water sampled from the wells.

1 2

(E0.005)

0 345

NUMBER OF PESTICIDE DETECTIONS

Molinate (E0.003)

2,4-D (E0.01)

p,p’-DDE (E0.002)

Chlorpyrifos (E0.004)

Diazinon (0.007)

Malathion (0.006)

Atrazine (0.008)

Deethylatrazine (E0.008)

Deethyldeisopropylatrazine (E0.02)

2-Hydroxyatrazine (E0.066)

Chlorimuronethyl (E0.008)

Diuron (E0.0007)

Tebuthiuron (E0.008)

Bentazon (E0.15)

Fipronil RPA (E0.001)

Fipronil sulfone (0.005)

Flumetsulam (E0.0437)

Imazaquin (E0.704)

Pesticide

EXPLANATION

Pesticide degradation 

product

Maximum concentration, 

in micrograms per liter

Metalaxyl (E0.005) E Estimated value

3 (4-chlorophenyl)-1-methyl urea (0.2056)

6
20

Stable Isotopes

Stable isotopes of hydrogen and oxygen in water 

molecules were used to determine the sources of shallow 

ground water in the rice-growing area in southwestern 

Louisiana. The two stable isotopes of hydrogen are 1

H 

and 2H (deuterium, D), and the two stable isotopes of 

oxygen are 16O and 18O. The isotopic compositions of 

hydrogen and oxygen in a water sample are reported in 

terms of the differences of the D/H and 18O/ 16O ratios 

relative to the Vienna Standard Mean Ocean Water 

(VSMOW) (Faure, 1986, p. 431). A delta (δ) notation, 

expressed as per mil (parts per thousand), is used to 

describe the relation of the abundance of a particular 

isotope to the standard.

Ocean water is enriched in the heavy stable 

isotopes of hydrogen and oxygen (D and 18O) relative 

to the light stable isotopes (H and 16O) and is the 

source for most rain. The rain forms in a cloud by 

condensation of water vapor, and the first raindrops to 

fall are enriched in D and 18O, similar to ocean water. 

As the moist air mass moves away (inland) from its 

source (ocean), the continuing preferential removal of 

D and 18O in the rainfall causes enrichment of 1H 

and 16O in the air mass, and δD and δ18O become 

progressively more negative. Craig (1961) used a 

large number of analyses of meteoric waters collected 

at different latitudes to determine that this isotopic 

fractionation process is related linearly and is 

represented as the Global Meteoric Water Line 

(GMWL) on plots of δD and δ18O (fig. 11).

The hydrogen 2/1 ratio, or δD, in the shallow wells 

in the rice-growing area ranged from -10.0 to -19.7 per mil 

(appendix 7, at the back of the report), and the oxygen 

ratio, or δ18O, ranged from -1.69 to -4.04 per mil. The 

values plotted very near the GMWL. The enrichment of 

the heavy stable isotopes indicated that the origin of the 

ground water was rainwater that originated near the study 

area (a possible source is the Gulf of Mexico), and the 

close proximity of the stable isotopes to the GMWL indiFigure 8. Radon concentrations in water from selected shallow wells in the rice-growing area in southwestern Louisiana, 2000-01.

WELL NUMBER

1

Maximum Contaminant Level

25th percentile

Median

1

0

100

200

300

400

500

600

700

800

900

1,000

1,100

1,200

1,300

1,400

1,500

1,600

2 3 4 5 6 7 8 9 11 13 14 15 16 17 18 19 21 23 24 25 26 28 30

Radon-222

C

O

N

C

E

N

T

R

ATI

O

N, I

N

PIC

O

C

U

RIE

S

P

E

R LIT

E

R

75th percentile

1 Source: U.S. Environmental Protection Agency, 2002b

Map number (see fig. 9)
30 MILES

0 30 KILOMETERS

0

Well location and number 24

Boundary f o the AcadianPontchartrain ACAD) ( Study Unit

21

Urban

Water

R ci e

udy St area

EXPLANATION

216 - 300

3 10 90 - 0

9 10 1- , 54 0

not pl sam ed for radon

Radon nce co ntrations, in picocuries

per liter

Lake

Charles

Jennings Crowley

Oberlin

Lafayette

Lake

Arthur

Area Shown

Index Map

ACAD Study 

Unit Boundary

Arkansas

Louisiana

iss s ipp

M

i s i

Texas

Figure 9. Radon concentration in water from selected shallow wells in the rice-growing area in southwestern Louisiana, 2000-01.

BEAUREGARD

VERNON

EVANGELINE

ALLEN

ST LANDRY

JEFFERSON

DAVIS

CALCASIEU

ACADIA

VERMLI ION IBERIA

ST. MARTIN

CAMERON

LAFAYETTE

RAPIDES

AVOYELLES

B N SA I E L E AK

A C IE L AS U C

LAKE

WHITE

LAKE

GRAND

LAKE

S

CAL

A

I

U

C

E

R

RIVE

des

annes C

t Me men au r

i er R v

B

yo a u

AFALAY

ATCH

A

R ER IV

UEUE

Q

DE

O

T

E

T

R

U

o B y u a

ez i e N

p qu

ER D

ER

RIV

u on Ho st

River

VERMILION

BAY WEST COTE

BLANCHE BAY

V n ermilio

v r Ri e

Teche

BA OU Y

b n Sa e i Riv r e

G F M XI O

ULF O E C

92° 00 ́

9 2° 30 ́ 93° 00 ́

9 3° 30 ́

3 00 0°  ́

3 30 0°  ́

3 00 1°  ́

yo B u a

CALCASIEU

RIVER

y B u a o

c i a ass ne L

1

13

22

24

26

17

16

8

5

18

6

9

3

19

15

4

23

25

11

30

28

10

27

14

2

21

7

Map credit: Modified from, Official Map of Louisiana, Department of Transportation and Development, 1986

Land-use ata d

 (source: Joseph Holmes, Louisiana

 Department of Environmental Quality,

 written commun., 2001)
30 MILES

0 30 KILOMETERS

0

Well location and number 24

Boundary f o the AcadianPontchartrain ACAD) ( Study Unit

22

Urban

Water

R ci e

udy St area

EXPLANATION

17 - 30

31 - 40

41 - 49

not pl sam ed for apparent age

Apparent age, in years

Lake

Charles

Jennings Crowley

Oberlin

Lafayette

Lake

Arthur

Area Shown

Index Map

ACAD Study 

Unit Boundary

Arkansas

Louisiana

iss s ipp

M

i s i

Texas

Figure 10. Apparent ages of water from selected shallow wells in the rice-growing area in southwestern Louisiana, 2000-01.

BEAUREGARD

VERNON

EVANGELINE

ALLEN

ST LANDRY

JEFFERSON

DAVIS

CALCASIEU

ACADIA

VERMLI ION IBERIA

ST. MARTIN

CAMERON

LAFAYETTE

RAPIDES

AVOYELLES

B N SA I E L E AK

A C IE L AS U C

LAKE

WHITE

LAKE

GRAND

LAKE

S

CAL

A

I

U

C

E

R

RIVE

des

annes C

t Me men au r

i er R v

B

yo a u

AFALAY

ATCH

A

R ER IV

UEUE

Q

DE

O

T

E

T

R

U

o B y u a

ez i e N

p qu

ER D

ER

RIV

u on Ho st

River

VERMILION

BAY WEST COTE

BLANCHE BAY

V n ermilio

v r Ri e

Teche

BA OU Y

b n Sa e i Riv r e

G F M XI O

ULF O E C

92° 00 ́

9 2° 30 ́ 93° 00 ́

9 3° 30 ́

3 00 0°  ́

3 30 0°  ́

3 00 1°  ́

yo B u a

CALCASIEU

RIVER

y B u a o

c i a ass ne L

1

13

22

24

26

17

16

8

5

18

6

9

3

19

15

4

23

25

11

30

28

10

27

14

2

21

7

Map credit: Modified from, Official Map of Louisiana, Department of Transportation and Development, 1986

Land-use ata d

 (source: Joseph Holmes, Louisiana

 Department of Environmental Quality,

 written commun., 2001)
23

cated that few geochemical or physical processes, such as 

evaporation, influenced the stable isotopic composition of 

the shallow ground water (Faure, 1986, p. 431).

Statistical Correlations of Physical Properties 

and Chemical Constituents

The Spearman rank correlation (SAS Institute 

Inc., 1990) was used to determine whether significant correlations existed between physical properties, selected 

chemical constituents, the number of pesticides detected, 

and the apparent age of ground water. Correlation analysis assesses not only the relation between two variables 

but also the strength of the relation (Helsel and 

Hirsch, 1993, p. 210-217). The Spearman rank correlation was chosen because water-quality data usually are not 

normally distributed and the number of samples was 

greater than 20 (Helsel and Hirsch, 1993, p. 217-218).

Correlation tests calculate a probability statistic 

(p-value) and a correlation coefficient (rho). The probability statistic relates to a confidence level. The 95-percent confidence level used in this report indicated a 95-

percent probability (p equal to or less than 0.05) that a 

correlation was statistically significant. The correlation 

coefficient describes the strength of the correlation and 

how the parameters (physical properties and chemical 

constituents) vary. For this report, parameters that had 

correlation coefficients of 0.6 or greater were considered 

strongly correlated, parameters that had correlation coefficients between 0.4 and 0.6 were considered moderately 

correlated, and parameters that had correlation coefficients of 0.4 or less were considered weakly correlated. A 

positive correlation coefficient means that as the value of 

one parameter increases, the value of the other parameter 

also increases. A negative correlation coefficient means 

that as the value of one parameter decreases, the value of 

the other parameter increases (Helsel and Hirsch, 1993, 

p. 209-211).

Correlations between physical properties (depth to 

ground water and well depth), selected chemical constituents (major inorganic ions, trace elements, and nutrients), the number of pesticides detected, and the apparent 

age of ground water were determined and are listed in 

table 5. Major-ion and trace-element concentrations that 

were less than the analytical reporting level were assigned 

a value of one-half the reporting limit so they would not 

have a rank equal to that of a measured value.

Correlations reflected the natural geochemical 

evolution of ground water in the study area. The depth 

to ground water was positively correlated to the well 

depth, indicating the ground water was under unconFigure 11. Relation between delta (δ) deuterium and δ oxygen-18 in water from selected shallow wells in 

the rice-growing area in southwestern Louisiana, 2000 (Craig, 1961; Faure, 1986).

High latitude

Global Meteoric Water Line (Craig, 1961)

D = 8

O + 10 per mil

δ

δ 18

Low latitude

Heaviest precipitation

-50 -40 -30 -20 -10 0 10

-400

-300

-200

-100

100

0

δ OXYGEN-18, IN PER MIL

δ DEUTERIUM, IN PER MIL

-5

-40

-20

0

-4 -3 -2 -1 0
24

fined or semiconfined conditions. As the depth to 

ground water increased, the concentrations of dissolved 

solids and the other constituents listed in table 5 

decreased. A possible explanation is that the flow rate 

was greater in the deeper sands, and, over time, the sediments were flushed and the concentrations of dissolved 

solids in the ground water decreased. The correlations 

with the radon concentration might be explained in a 

similar manner (Wanty and Nordstrom, 1993, p. 433). 

In addition to being inversely correlated to the depth to 

ground water, the radon concentrations were correlated 

inversely with well depth and the apparent age of ground 

water. Radon concentrations correlated positively with 

specific conductance, pH, and bicarbonate and alkalinity 

concentrations indicating that radon concentrations generally decreased in the deeper ground water similar to 

the other dissolved constituents. The apparent age of 

ground water was correlated inversely with nitrite plus 

nitrate concentration, indicating that as the apparent age 

increased, the nitrite plus nitrate concentration 

decreased. This might have been a result of changes in 

agriculture and domestic practices or a result of natural 

processes, such as greater dissolution and movement of 

naturally-occurring nitrogen sources (organic matter) in 

the higher transmissivity, or higher yield, deep wells. 

No correlations existed between the number of pesticides detected and any of the physical or chemical properties of the ground water.

SUMMARY AND CONCLUSIONS 

The purpose of this report is to describe quality 

of water from shallow wells in the rice-growing area 

and to relate that water quality to natural and 

anthropogenic influences. In 1999-2001, the U.S. 

Geological Survey (USGS) installed and sampled 

27 shallow wells in the Chicot aquifer system in the 

rice-growing area in southwestern Louisiana as part of 

the Acadian-Pontchartrain Study Unit of the National 

Water-Quality Assessment Program. The study area 

overlies the Chicot aquifer system, which is the primary 

source of water for irrigation and public-water supplies 

in the area and is vulnerable to the effects of surface 

activities because of the lack of a continuous confining 

unit throughout the region. Wells were installed at 

shallow depths in the Chicot aquifer system or surficial 

confining unit and ranged in depths from 12.25 to 92 ft 

below land surface. Water levels ranged from 

0.57 to 80.19 ft below land surface.

Quality-control samples, including field-blank 

samples, replicate environmental samples, and fieldand laboratory-spiked samples, were collected to test 

sample-collection and -processing procedures. Few 

water-quality constituents analyzed for were detected in 

the field-blank samples. The variability between the 

environmental samples and the corresponding replicate 

Variables Number of 

sample pairs

Probability 

statistic

Correlation 

coefficient

Depth to ground water and well depth 27 0.002 0.58

Depth to ground water and specific conductance 27 .014 - .47

Depth to ground water and pH 27 .032 - .41

Depth to ground water and alkalinity 27 .016 - .46

Depth to ground water and dissolved solids 27 .014 - .47

Depth to ground water and calcium 27 < .001 - .63

Depth to ground water and magnesium 27 .011 - .48

Depth to ground water and iron 27 .008 .50

Depth to ground water and uranium 27 .023 - .43

Depth to ground water and radon 24 .001 - .62

Radon concentration and well depth 24 .027 - .45

Radon concentration and specific conductance, pH, bicarbonate, and alkalinity 24 < .057 > .39

Radon concentration and apparent age of ground water 18 .016 - .56

Apparent age of ground water and nitrite plus nitrate concentration 20 < .001 - .70

Table 5. Results of Spearman rank correlation test for physical properties and selected chemical constituents in 

water from selected shallow wells in the rice-growing area in southwestern Louisiana, 2000-01

[<, less than; >, greater than] 
25

samples typically was less than 5 percent, indicating an 

acceptable degree of laboratory precision and 

reproducibility. Mean recoveries of pesticides from the 

field-spiked and field-spiked replicate samples ranged 

from 63 to 104 percent, and mean recoveries from the 

laboratory-spiked and laboratory-spiked replicate 

samples were within the USGS National Water Quality 

Laboratory control limits. Results of the spiked-sample 

analyses indicated sampling and analysis procedures 

adequately detected the pesticides analyzed for and no 

major matrix interferences existed. Quality-control 

samples indicate no bias in ground-water data from 

collection or analysis.

Ground-water samples were analyzed for general 

ground-water properties and about 150 water-quality 

constituents, including major inorganic ions, trace 

elements, nutrients, dissolved organic carbon (DOC), 

pesticides, radon, chlorofluorocarbons, and selected 

stable isotopes. General ground-water properties were 

typical of those obtained in previous studies of the 

Chicot aquifer. Dissolved-solids concentrations for 

17 wells exceeded the U.S. Environmental Protection 

Agency secondary maximum contaminant level 

(SMCL) of 500 milligrams per liter (mg/L) for drinking 

water. Major inorganic ion concentrations generally 

were less than their respective maximum contaminant 

levels (MCLs) for drinking water. The 250-mg/L 

SMCL for sulfate was exceeded in water from one well, 

and the 250-mg/L SMCL for chloride was exceeded in 

water from seven wells.

Concentrations of all trace elements, except iron, 

were less than 1,000 micrograms per liter (mg/L), and 

most were less than the drinking-water standards. Iron 

concentrations for 3 wells and manganese concentrations 

for 15 wells exceeded their respective SMCLs of 300 and 

50 mg/L. Only three nutrient concentrations were 

greater than 2 mg/L, a level that might indicate contamination from human activities, and only one nutrient concentration (that for nitrite plus nitrate as nitrogen) was 

greater than a respective MCL. The elevated nitrate concentration could be attributed to a previous land use in 

the area (chicken and pig yard), and, thus, may not be 

attributed to rice-growing practices. DOC concentrations had a median of 0.5 mg/L, which indicated naturally-occurring DOC conditions in the study area.

Of the 92 pesticides analyzed for, 13 were 

detected in the ground-water samples; and of the 17 

pesticide degradation products analyzed for, 7 were 

detected in the ground-water samples. At least one 

pesticide was detected in 14 of the 27 wells sampled. 

All pesticides and pesticide degradation products 

detected had concentrations that were less than U.S. 

Environmental Protection Agency drinking-water 

standards. Bentazon, 2,4.-D, and molinate (three rice 

herbicides) were detected in water from four, one, and 

one wells, respectively, and malathion (a rice 

insecticide) was detected in water from one well. One 

well had low concentrations of atrazine, deethlyatrazine, 

nitrate, phosphorus, orthophosphorus, and DOC, 

indicating a possible effect from agricultural or 

domestic activities. The presence of rice and other 

pesticides in the shallow ground water indicates that the 

hardpan the beneath rice fields is not preventing 

downward movement in all areas.

Radon concentrations for 22 of the 24 wells 

sampled were at or greater than the U.S. Environmental 

Protection Agency proposed MCL of 300 picocuries per 

liter. Chlorofluorocarbons were used to estimate the 

apparent age of water in 21 of the 27 wells sampled. 

Ages varied with depth and water level and ranged from 

about 17 to 49 years. The median age was about 

38 years. Stable isotopes of hydrogen and oxygen in 

water molecules indicated that the origin of ground 

water in the study area was rainwater that originated 

near the study area and that few geochemical or 

physical processes influenced the stable isotopic 

composition of the shallow ground water.

The Spearman rank correlation was used to 

determine whether significant correlations existed 

between physical properties, selected chemical 

constituents, the number of pesticides detected, and the 

apparent age of water. The depth to ground water was 

positively correlated to the well depth, indicating the 

ground water was under unconfined or semiconfined 

conditions. The depth to ground water was inversely 

correlated to specific conductance, pH, and alkalinity, 

dissolved solids, calcium, magnesium, uranium, and 

radon concentrations. As the depth to ground water 

increased, the concentrations of dissolved solids and 

other constituents decreased, possibly because the 

deeper sands had a greater ability to transmit ground 

water, which, over time, would flush out, or dilute, the 

concentrations of dissolved solids and other constituents 

in the natural sediments. The apparent age of water was 

correlated inversely with nitrite plus nitrate 

concentration, indicating that as the apparent age 

increased, the nitrite plus nitrate concentration 

decreased. No correlations existed between the number 

of pesticides detected and any of the physical or 

chemical properties of the ground water.
26

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southwestern Louisiana: Louisiana Department of 

Transportation and Development Technical 

Report no. 42, 22 p.

Nyman, D.J., Halford, K.J., and Martin, A., Jr., 1990, 

Geohydrology and simulation of flow in the Chicot 

aquifer system of southwestern Louisiana: Louisiana 

Department of Transportation and Development 

Technical Report no. 50, 58 p.

Patton, C.J., and Truitt, E.P., 2000, Methods of analysis 

by the U.S. Geological Survey National Water Quality 

Laboratory--Determination of ammonium plus 

organic nitrogen by a Kjeldahl digestion method and 

an automated photometric finish that includes digest 

cleanup by gas diffusion: U.S. Geological Survey 

Open-File Report 00-170, 31 p.

Plummer, L.N., and Friedman, L.C., 1999, Tracing and 

dating young ground water: U.S. Geological Survey 

Fact Sheet FS-134-99, 4 p.

Rose, D.L., and Schroeder, M.P., 1995, Methods of analysis by the U.S. Geological Survey National Water 

Quality Laboratory - Determination of volatile 

organic compounds in water by purge and trap capillary by gas chromatography/mass spectrometry: U.S. 

Geological Survey Open-File Report 94-708, 26 p.

Sargent, B.P., 2002, Water use in Louisiana: Louisiana 

Department of Transportation and Development 

Water Resources Special Report no. 15, 133 p.

SAS Institute Inc., 1990, SAS procedures guide, version 

6, (3rd ed.): Cary, N.C., SAS Institute Inc., 705 p.

Scott, J.C., 1990, Computerized stratified random siteselection approaches for design of a ground-water-quality sampling network: U.S. Geological Survey WaterResources Investigations Report 90-4101, 109 p.

Smoot, C.W., 1986, Areal extent of freshwater in major 

aquifers in Louisiana: U.S. Geological Survey Water 

Resources Investigations Report 86-4150, 1 sheet.

Townsend, M.A., and Young, D.P., 1999, Atrazine and its 

metabolites as indicators of stream-aquifer interaction 

in Kansas in The seventh symposium on the chemistry 

and fate of modern pesticides, Sept. 14-16, 1999 [abs.]: 

Lawrence, Kansas, University of Kansas, p. 27.

U.S. Census Bureau, 2002, United States census 2000, Census 2000 gateway: accessed October 18, 2002, at 

URL http://www.census.gov/main/www/cen2000.html

U.S. Environmental Protection Agency, 1993, Methods for 

the determination of inorganic substances in environmental samples: Cincinnati, Ohio, Environmental 

Monitoring and Support Laboratory, EPA/600/R93/100, August 1993, p. 79.

-----2000, Ground water & drinking water, Proposed 

radon in drinking water rule: accessed October 17, 

2002, at URL 

http://www.epa.gov/safewater/radon/proposal.html

-----2002a, Air - Indoor air, radon: accessed October 22, 

2002, at URL http://www.epa.gov/iaq/radon

-----2002b, Ground water and drinking water, Current 

drinking water standards: accessed October 22, 

2002, at URL http://www.epa.gov/safewater/mcl.html

 -----2002c, Source water protection, Designated Sole 

Source Aquifer in EPA Region VI: accessed 

October 17, 2002, at URL 

http://www.epa.gov/safewater/swp/ssa/reg6.html

U.S. Geological Survey, 1999a, Index of /pub/data/landcover/states: accessed October 23, 2002, at URL 

http://edcwww.cr.usgs.gov/pub/data/landcover/states

-----1999b, Strategic directions for the U.S. Geological 

Survey ground-water resources program--A report to 

Congress, November 30, 1998: Reston, Va., U.S. 

Geological Survey Office of Ground Water, 14 p.

Wanty, R.B., and Nordstrom, D.K., 1993, Natural radionuclides, chap. 17 of Alley, W.M., ed., Regional 

Ground Water Quality: New York, Van Nostrand 

Reinhold, p. 423-441.

Zaugg, S.D., Sandstrom, M.W., Smith, S.G., and Fehlberg, 

K.M., 1995, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory--

Determination of pesticides in water by C-18 solid 

phase extraction and capillary-column gas chromatography/mass spectrometry with selected-ion monitoring: U.S. Geological Survey Open-File 

Report 95-181, 60 p.
29

APPENDIXES

1. General ground-water properties in water from selected shallow wells in the rice-growing area in southwestern Louisiana, 2000-01

2. Dissolved solids and major inorganic ion concentrations in water from selected shallow wells in the 

rice-growing area in southwestern Louisiana, 2000-01 

3. Trace-element concentrations in water from selected shallow wells in the rice-growing area in southwestern Louisiana, 2000-01 

4. Nutrients and dissolved organic carbon concentrations in water from selected shallow wells in the ricegrowing area in southwestern Louisiana, 2000-01 

5. Pesticide concentrations in water from selected shallow wells in the rice-growing area in southwestern 

Louisiana, 2000-01 

6. Concentrations of pesticide degradation products in water from selected shallow wells in the rice-growing area in southwestern Louisiana, 2000-01 

7. Radon, chlorofluorocarbons, and stable isotope concentrations in water from selected shallow wells in 

the rice-growing area in southwestern Louisiana, 2000-01 
30

ACAD

well

number

DOTD local

well number

USGS site

identification

number

Sample

date

Specific

conductance,

field

(μS/cm)

Specific

conductance,

lab

(μS/cm)

pH, 

field

(S.U.)

pH, 

lab

(S.U.)

Air

temperature

(oC)

Water

temperature

(oC)

Air

pressure

(mm Hg)

Turbidity

(N.T.U.)

Dissolved

oxygen

(mg/L)

Dissolved

oxygen

(percent)

Acid neutralizing

capacity, 

fixed

end-point 

titration,

field

(mg/L as 

CaCO3)

Alkalinity,

 incremental

titration, 

field

(mg/L as 

CaCO3)

Alkalinity, 

fixed 

endpoint

titration, 

laboratory

(mg/L as 

CaCO3)

Sample 

flow rate

(gallons 

per 

minute)

Pump

period

(minutes)

1 AL-5475Z 303839092435101 05-02-00 227 233 6.1 6.4 21.0 20.7 762 0 2.3 31 63 64 68 0.14 902 EV-5477Z 303741092213901 01-27-00 867 870 7.1 7.1 9.0 19.5 767 6.0 2.5 27 370 370 390 0.15 503 AL-5477Z 302927092490001 05-25-00 317 331 6.4 6.8 33.0 24.0 758 20 1.2 14 120 120 110 0.15 354 EV-5482Z 302952092325501 01-26-00 1,150 1,170 7.2 7.5 15.0 20.4 769 <1.0 1.4 16 330 330 330 0.14 455 JD-6843Z 302220092570201 01-11-00 3,160 3,100 6.6 6.7 19.0 21.1 764 1.0 0.9 10 230 230 240 0.16 956 JD-6844Z 302246092400101 01-25-00 715 710 7.2 7.3 18.0 21.5 766 14 1.4 16 270 270 270 0.15 457 JD-6834Z 301451092541401 01-12-00 1,930 1,950 7.1 7.2 21.0 22.3 762 2.0 <1.0 <12 490 470 490 0.15 358 AC-7869Z 301444092211501 01-13-00 960 961 7.1 7.3 21.0 22.3 769 <30 3.2 23 480 480 490 0.12 659 JD-6845Z 301003092561301 01-18-00 1,420 1,440 7.1 7.2 23.0 20.5 767 1.0 0.5 6 420 420 430 0.15 75

10 AC-7977Z 300659092352901 02-09-00 1,860 1,870 7.1 7.1 12.0 20.0 770 5.0 1.5 17 540 550 560 0.14 8511 VE-10210Z 295531092132001 05-23-00 540 536 6.5 6.7 33.0 27.1 759 1.0 2.8 35 190 190 200 0.08 6513 EV-5470Z 304121092293301 02-15-00 619 625 6.1 6.1 21.0 21.5 764 38 1.9 22 120 110 110 0.15 4514 EV-5486Z 303616092331801 02-16-00 1,340 1,360 7.4 7.4 25.0 22.1 766 25 0.6 7 460 460 470 0.17 7515 AL-5479Z 303127092404801 05-11-00 510 524 6.6 6.7 30.0 22.6 759 1.0 1.5 17 130 140 140 0.16 8016 SL-6706Z 303237092105501 02-01-00 648 664 7.1 7.2 10.0 19.6 768 <1.0 0.9 10 270 280 290 0.17 9017 AC-7934Z 302821092171001 02-03-00 911 920 7.0 7.4 13.0 20.7 767 2.0 1.5 17 340 340 350 0.14 6018 JD-6909Z 302448092510501 05-09-00 1,690 1,720 6.2 6.4 31.0 21.8 759 1.0 2.9 34 140 130 140 0.14 6019 AC-7935Z 302132092234401 01-19-00 795 788 6.8 7.0 27.0 22.3 761 <1.0 1.8 20 270 270 280 0.15 6021 JD-6835Z 301525092425701 05-10-00 1,020 1,040 7.2 7.4 33.0 22.6 756 4.0 2.7 32 310 320 340 0.18 4522 AC-7936Z 301906092272401 01-09-00 1,810 1,790 7.0 7.2 19.0 21.1 759 8.0 0.6 7 360 360 370 0.17 4523 AC-7976Z 301042092211101 02-17-00 1,150 1,160 7.2 7.4 28.0 22.9 764 2.0 1.3 15 380 380 320 0.14 5024 JD-6846Z 300626092462901 09-21-00 675 678 7.3 7.8 29.0 22.6 759 1.3 0.9 10 210 210 210 0.12 8025 AC-7938Z 300614092233001 02-10-00 1,420 1,430 7.2 7.4 20.0 21.2 763 3.0 0.7 7 300 300 310 0.15 5526 CN-5863Z 300216093042301 01-10-00 1,870 1,860 7.0 7.0 18.0 19.0 761 1.0 0.7 8 480 470 370 0.15 6027 VE-10211Z 295932092284401 02-08-00 2,220 2,300 7.1 7.3 14.0 21.2 772 110 3.0 35 530 530 540 0.17 7528 JD-6847Z 301737093010301 01-11-00 1,180 1,160 7.3 7.3 26.0 22.8 764 2.0 0.6 7 370 360 380 0.14 6030 BE-6230Z 302723093144201 09-28-00 250 255 6.2 6.3 27.0 17.0 --- <30 --- --- 46 39 46 0.12 55

Appendix 1. General ground-water properties in water from selected shallow wells in the rice-growing area in southwestern Louisiana, 2000-01[ACAD, Acadian-Pontchartrain Study Unit of the National Water-Quality Assessment Program; DOTD, Department of Transportation and Development; USGS, U.S. Geological 

Survey; μS/cm, microsiemens per centimeter at 25 degrees Celsius; S.U., standard units; oC, degrees Celsius; mm Hg, millimeters of mercury; NTU, nephelometric turbidity units; 

mg/L, milligrams per liter; <, less than; ---, no data]
31

ACAD

well

number

DOTD local

well number

USGS site

identification

number

Sample

date

Dissolved

residue

at 180oC

(mg/L)

no CAS

number

Calcium

(mg/L

as Ca)

7440-70-2

Magnesium

(mg/L as

Mg)

7439-95-4

Sodium

(mg/L as

Na)

7440-23-5

Potassium

(mg/L as

K)

7440-09-7

Bicarbonate

(calculated)

(mg/L as

HCO3)

no CAS

number

Sulfate

(mg/L as

SO4)

14808-79-8

Chloride

(mg/L as

Cl)

16887-00-6

Fluoride

(mg/L as

F)

16984-48-8

Bromide

(mg/L as

Br)

24959-67-9

Silica

(mg/L as

SiO2)

7631-86-9

1 AL-5475Z 303839092435101 05--02-00 180 13 6.1 22 1.6 78 5.0 26 <0.1 0.1 582 EV-5477Z 303741092213901 01-27-00 520 99 33 45 0.9 451 28 48 0.4 0.4 303 AL-5477Z 302927092490001 05-25-00 240 23 10 20 2.2 144 17 12 0.2 0.1 744 EV-5482Z 302952092325501 01-26-00 634 66 46 100 0.9 399 6.1 180 0.5 1.0 265 JD-6843Z 302220092570201 01-11-00 1,850 120 61 410 1.3 277 49 830 0.5 2.2 506 JD-6844Z 302246092400101 01-25-00 425 69 17 55 0.8 332 15 55 0.2 0.3 357 JD-6834Z 301451092541401 01-12-00 1,150 89 36 280 1.0 569 110 290 0.6 1.1 238 AC-7869Z 301444092211501 01-13-00 574 70 61 44 1.9 582 10 45 0.7 0.2 279 JD-6845Z 301003092561301 01-18-00 856 86 35 170 1.8 510 100 160 0.6 0.7 24

10 AC-7977Z 300659092352901 02-09-00 1,180 91 60 220 3.6 666 270 140 0.3 0.3 2711 VE-10210Z 295531092132001 05-23-00 357 36 12 60 1.2 234 27 31 <0.1 0.1 5713 EV-5470Z 304121092293301 02-15-00 335 29 13 64 1.9 134 5.8 120 <0.1 0.5 2014 EV-5486Z 303616092331801 02-16-00 764 49 29 200 1.0 555 11 160 0.4 0.6 2715 AL-5479Z 303127092404801 05-11-00 310 28 13 51 1.2 168 5.5 73 0.3 0.4 4616 SL-6706Z 303237092105501 02-01-00 387 80 19 28 0.6 338 16 34 0.2 0.1 3217 AC-7934Z 302821092171001 02-03-00 508 98 31 45 1.1 417 4.5 91 0.3 0.3 3218 JD-6909Z 302448092510501 05-09-00 1,020 78 40 180 1.7 161 25 420 0.2 1.2 4819 AC-7935Z 302132092234401 01-19-00 465 64 19 71 1.5 332 23 70 0.3 0.3 3021 JD-6835Z 301525092425701 05-10-00 578 81 25 93 0.7 388 18 120 0.5 0.8 2522 AC-7936Z 301906092272401 01-09-00 1,000 101 54 170 1.9 434 28 330 0.5 1.4 2623 AC-7976Z 301042092211101 02-17-00 644 61 30 140 1.3 468 1.6 150 0.5 0.5 2624 JD-6846Z 300626092462901 09-21-00 381 48 15 62 1.7 256 7.0 81 0.1 0.3 2825 AC-7938Z 300614092233001 02-10-00 776 71 29 170 1.2 370 4.2 280 0.5 0.8 2826 CN-5863Z 300216093042301 01-10-00 1,080 140 48 170 0.9 578 43 310 0.6 1.0 2827 VE-10211Z 295932092284401 02-08-00 1,260 84 59 310 3.9 643 52 400 0.7 1.0 2528 JD-6847Z 301737093010301 01-11-00 664 81 32 110 1.4 445 10 160 0.7 0.4 2330 BE-6230Z 302723093144201 09-28-00 180 8.2 3.8 34 0.8 48 E0.3 48 <0.1 0.2 53

Appendix 2. Dissolved solids and major inorganic ion concentrations in water from selected shallow wells in the rice-growing area in southwestern 

Louisiana, 2000-01

[All concentrations are dissolved. Numbers below the chemical names are the Chemical Abstracts Service (CAS) numbers. ACAD, Acadian-Pontchartrain Study Unit of the National Water-Quality Assessment Program; DOTD, Department of Transportation and Development; USGS, U.S. Geological Survey; oC, degrees Celsius; mg/L, milligrams per liter;<, less than; E, estimated]
32

ACAD

well

number

DOTD local

well number

USGS site

identification

number

Sample

date

Aluminum

(μg/L as Al)

7429-90-5

Antimony

(μg/L as Sb)

7440-36-0

Arsenic

(μg/L as As)

7440-38-2

Barium

(μg/L as Ba)

7440-39-3

Beryllium

(μg/L as Be)

7440-41-7

Boron

(μg/L as B)

7440-42-8

Cadmium

(μg/L as Cd)

7440-43-9

Chromium

(μg/L as Cr)

740-47-3

Cobalt

(μg/L as Co)

7440-48-4

Copper

(μg/L as Cu)

7440-50-8

Iron

(μg/L as Fe)

7439-89-6

1 AL-5475Z 303839092435101 05-02--00 <1 <1 <1 98 <1 20 <1 <1 2.4 <1 202 EV-5477Z 303741092213901 01-27-00 <1 <1 <2 410 <1 --- <1 E.4 <1.0 <1 E93 AL-5477Z 302927092490001 05-25-00 <17 <2 <2 100 <2 10 <2 <1 <2.0 <2 6,5004 EV-5482Z 302952092325501 01-26-00 2 <1 E2 360 <1 --- <1 <1 <1.0 1 <105 JD-6843Z 302220092570201 01-11-00 6 <2 3 180 <2 --- <2 E1 3.4 <2 5406 JD-6844Z 302246092400101 01-25-00 <1 <1 E1 350 <1 --- <1 1 <1.0 4 207 JD-6834Z 301451092541401 01-12-00 1 <1 <2 48 <1 --- <1 E1 <1.0 <1 <108 AC-7869Z 301444092211501 01-13-00 5 <1 <2 820 <1 --- <1 2 <1.0 <1 E89 JD-6845Z 301003092561301 01-18-00 1 <1 E1 150 <1 --- <1 <1 1.1 <1 20

10 AC-7977Z 300659092352901 02-09-00 1 <1 <2 37 <1 --- <1 <2 <1.0 11 1011 VE-10210Z 295531092132001 05-23-00 <9 <1 4 180 <1 50 <1 E1 <1.0 <1 <1013 EV-5470Z 304121092293301 02-15-00 <1 <1 <1 180 <1 10 <1 <1 <1.0 7 E814 EV-5486Z 303616092331801 02-16-00 2 <1 1 280 <1 60 <1 2 <1.0 2 E715 AL-5479Z 303127092404801 05-11-00 <1 <1 2 160 <1 20 <1 <1 <1.0 <1 82016 SL-6706Z 303237092105501 02-01-00 1 <1 E1 250 <1 --- <1 <1 <1.0 8 E617 AC-7934Z 302821092171001 02-03-00 <1 <1 <2 380 <1 --- <1 <1 <1.0 1 <1018 JD-6909Z 302448092510501 05-09-00 1 <1 4 410 <1 20 <1 <1 <1.0 <1 3019 AC-7935Z 302132092234401 01-19-00 1 <1 <2 270 <1 <1 <1 <1.0 2 <1021 JD-6835Z 301525092425701 05-10-00 <19 <1 <1 16 <1 30 <1 E1 1.5 <1 <1022 AC-7936Z 301906092272401 01-09-00 <1 <1 <2 850 <1 --- <1 <1 <1.0 <1 <1023 AC-7976Z 301042092211101 02-17-00 1 <1 1 540 <1 40 <1 <1 <1.0 4 <1024 JD-6846Z 300626092462901 09-21-00 <1 <1 4 220 <1 40 <1 E1 <1.0 <1 8025 AC-7938Z 300614092233001 02-10-00 <1 <1 E1 210 <1 --- <1 <1 <1.0 <1 E526 CN-5863Z 300216093042301 01-10-00 <1 <1 <2 250 <1 --- <1 E1 1.3 <1 <1027 VE-10211Z 295932092284401 02-08-00 1 <1 <2 160 <1 --- <1 <2 <1.0 3 <1028 JD-6847Z 301737093010301 01-11-00 <1 <1 <2 640 <1 --- <1 <1 <1.0 <1 <1030 BE-6230Z 302723093144201 09-28-00 1 <1 <1 110 <1 30 <1 1 <1.0 <1 20

Appendix 3. Trace-element concentrations in water from selected shallow wells in the rice-growing area in southwestern Louisiana, 2000-01[Concentrations are dissolved unless noted. ACAD, Acadian-Pontchartrain Study Unit of the National Water-Quality Assessment Program (NAWQA); DOTD, Department of Transportation and Development; USGS, U.S. Geological Survey; μg/L, micrograms per liter; numbers below the chemical names are the Chemical Abstracts Service (CAS) numbers; 

<, less than; ---, no data; E, estimated]
33

ACAD

well

number

Lead

(μg/L as Pb)

7439-92-1

Lithium

 (μg/L as Li)

7439-93-2

Manganese

(μg/L as Mn)

7439-96-5

Mercury, total

(μg/L as Hg)

7439-37-6

Molybdenum

(μg/L as Mo)

7439-98-7

Nickel

(μg/L as Ni)

7440-02-0

Selenium

(μg/L as Se)

7782-49-2

Silver

(μg/L as Ag)

7440-22-4

Strontium

(μg/L as Sr)

7440-24-6

Thallium

(μg/L as Tl)

7440-28-0

Uranium

(μg/L as U)

7440-61-0

Vanadium

(μg/L as V)

7440-62-2

Zinc

(μg/L as Zn)

7440-66-6

1 <1 10 73 --- <1 4 <1 <1 130 <0.9 <1.0 2.0 22 <1 --- 2 <0.3 <1 3 <2 <1 --- --- 2.6 --- <13 <2 30 360 <0.3 <2 <2 <2 <2 190 <2 <2.0 <2.0 54 <1 --- 48 <0.3 2 2 E2 <1 --- --- 3.8 --- <15 <2 --- 450 <0.3 <2 4 <2 <2 --- --- 4.4 --- 36 <1 --- E2 <0.3 <1 2 <2 <1 --- --- <1.0 --- <17 <1 --- 120 <0.3 3 1 E2 <1 --- --- 4.9 --- 18 <1 --- 100 <0.3 7 5 14 <1 --- --- 11 --- 29 <1 --- 740 <0.3 9 2 <2 <1 --- --- 10 --- 1

10 <1 --- 220 <0.3 5 3 <2 <1 --- --- 16 --- 211 <1 10 180 <0.3 <1 3 <1 <1 180 <0.9 <1.0 4.5 <313 <1 10 4 E0.2 <1 2 4 <1 160 <0.9 <1.0 1.6 114 <1 50 <2 <0.3 3 2 <1 <1 400 <0.9 5.8 6.6 <115 <1 20 380 <0.3 <1 <1 1 <1 150 <0.9 <1.0 <1.0 <116 <1 --- 210 <0.3 2 3 <2 <1 --- --- 1.8 --- <117 <1 --- 9 <0.3 1 <1 <2 <1 --- --- 1.8 --- <118 <1 60 360 <0.3 <1 6 29 <1 420 <0.9 <1.0 6.7 <119 <1 --- 4 <0.3 <1 <1 <2 <1 --- --- <1.0 --- <121 <1 0 <2 <0.3 <1 2 <1 <1 20 <0.9 <1.0 <1.0 <522 <1 --- 9 <0.3 2 8 6 <1 --- --- 5.8 --- 123 <1 30 40 <0.3 3 2 <1 <1 430 <0.9 4.6 4.4 124 <1 20 400 <0.3 4 1 <1 <1 290 <0.9 <1.0 2.6 <125 <1 --- 24 <0.3 4 2 E1 <1 --- --- 4.4 --- 626 <1 --- 390 <0.3 2 6 <2 <1 --- --- 8.6 --- 127 <1 --- 210 <0.3 4 7 <2 <1 --- --- 7.5 --- 228 <1 --- 270 <0.3 2 7 <2 <1 --- --- 5.5 --- <130 <1 10 3 <0.3 <1 3 <1 <1 50 <0.9 <1.0 1.2 5

Appendix 3. Trace-element concentrations in water from selected shallow wells in the rice-growing area in southwestern Louisiana, 2000-01--Continued
34

ACAD

well

number

DOTD local

well number

USGS site

identification

number

Sample

date

Nitrogen,

ammonia

 (mg/L as N)

7664-41-7

Nitrogen,

ammonia plus

organic nitrogen

(mg/L as N)

17778-88-0

Nitrogen,

nitrite plus nitrate

 (mg/L as N)

no CAS number

Nitrogen,

nitrite

(mg/L as N)

14797-65-0

Phosphorus

(mg/L as P)

7732-14-0

Orthophosphorus

(mg/L as P)

14265-44-2

Carbon,

organic

(mg/L as C)

no CAS

number

1 AL-5475Z 303839092435101 05-02-00 0.02 <0.10 <0.05 <0.01 0.21 0.19 E0.22 EV-5477Z 303741092213901 01-27-00 <0.02 <0.10 0.90 <0.01 0.04 0.04 0.53 AL-5477Z 302927092490001 05-25-00 0.07 E0.08 <0.05 <0.01 <0.01 <0.01 0.64 EV-5482Z 302952092325501 01-26-00 0.02 <0.10 <0.05 <0.01 0.06 0.03 0.65 JD-6843Z 302220092570201 01-11-00 <0.02 <0.10 <0.05 <0.01 0.02 0.06 <0.36 JD-6844Z 302246092400101 01-25-00 <0.02 <0.10 3.6 <0.01 0.07 0.06 0.67 JD-6834Z 301451092541401 01-12-00 <0.02 <0.10 <0.05 <0.01 0.11 0.09 E0.68 AC-7869Z 301444092211501 01-13-00 0.03 <0.10 0.10 <0.01 0.04 0.04 0.99 JD-6845Z 301003092561301 01-18-00 0.11 E0.09 <0.05 <0.01 0.17 0.17 ---

10 AC-7977Z 300659092352901 02-09-00 0.70 0.83 <0.05 <0.01 0.04 0.04 0.711 VE-10210Z 295531092132001 05-23-00 0.08 0.11 0.77 <0.01 0.48 0.45 1.413 EV-5470Z 304121092293301 02-15-00 <0.02 0.26 0.23 <0.01 E0.01 <0.01 E0.214 EV-5486Z 303616092331801 02-16-00 <0.02 <0.10 1.1 <0.01 0.08 0.08 E0.215 AL-5479Z 303127092404801 05-11-00 0.03 <0.10 <0.05 <0.01 0.31 0.35 E0.216 SL-6706Z 303237092105501 02-01-00 <0.02 <0.10 0.36 <0.01 0.06 0.04 0.417 AC-7934Z 302821092171001 02-03-00 0.02 <0.10 <0.05 <0.01 0.05 0.04 E0.218 JD-6909Z 302448092510501 05-09-00 <0.02 <0.10 0.87 <0.01 0.28 0.26 <0.319 AC-7935Z 302132092234401 01-19-00 <0.02 0.26 2.4 <0.01 0.04 0.04 0.621 JD-6835Z 301525092425701 05-10-00 <0.02 E0.07 1.0 <0.01 0.05 0.04 0.622 AC-7936Z 301906092272401 01-09-00 0.04 E0.07 13 <0.01 0.05 0.05 E0.623 AC-7976Z 301042092211101 02-17-00 0.05 E0.07 <0.05 <0.01 0.06 0.06 E0.224 JD-6846Z 300626092462901 09-21-00 0.15 0.17 <0.05 <0.01 0.25 0.25 0.625 AC-7938Z 300614092233001 02-10-00 <0.02 E0.06 <0.05 <0.01 0.08 0.07 E0.226 CN-5863Z 300216093042301 01-10-00 0.03 0.12 <0.05 <0.01 0.03 0.03 E127 VE-10211Z 295932092284401 02-08-00 0.84 0.99 <0.05 <0.01 0.03 0.03 E0.328 JD-6847Z 301737093010301 01-11-00 <0.02 <0.10 0.05 <0.01 0.02 0.02 E0.630 BE-6230Z 302723093144201 09-28-00 <0.02 E0.06 0.07 <0.01 0.09 0.08 E0.2

Appendix 4. Nutrients and dissolved organic carbon concentratons in water from selected shallow wells in the rice-growing area in southwestern Louisiana, 

2000-01

[All concentrations are dissolved. ACAD, Acadian-Pontchartrain Study Unit of the National Water-Quality Assessment Program (NAWQA); DOTD, Department of Transportation and Development; USGS, U.S. Geological Survey; mg/L, milligrams per liter; numbers below the chemical names are the Chemical Abstracts Service (CAS) numbers; <, less than; E, estimated; ---, no data. ]
35

ACAD

well

number

DOTD local

well number

USGS site

identification

number

Sample

date

Acetochlor

H

34256-82-1

Acifluorfen

H

50594-66-6

Alachlor

H

15972-60-8

Aldicarb

I

116-06-3

Atrazine

H

1912-24-9

Azinphos-methyl

I

86-50-0

Bendiocarb

I

22781-23-3

Benfluralin

H

1861-40-1

Benomyl

(carbamate?)

F

17804-35-2

Bensulfuron 

methyl

83055-99-6

1 AL-5475Z 303839092435101 05-02-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.04822 EV-5477Z 303741092213901 01-27-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.04823 AL-5477Z 302927092490001 05-25-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.04824 EV-5482Z 302952092325501 01-26-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.04825 JD-6843Z 302220092570201 01-11-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.04826 JD-6844Z 302246092400101 01-25-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.04827 JD-6834Z 301451092541401 01-12-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.04828 AC-7869Z 301444092211501 01-13-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.04829 JD-6845Z 301003092561301 01-18-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.0482

10 AC-7977Z 300659092352901 02-09-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.048211 VE-10210Z 295531092132001 05-23-00 <0.002 <0.06 <0.002 <0.08 0.008 <0.001 <0.061 <0.002 <0.022 <0.0482

13 EV-5470Z 304121092293301 02-15-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.048214 EV-5486Z 303616092331801 02-16-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.048215 AL-5479Z 303127092404801 05-11-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.010 <0.061 <0.002 <0.022 <0.048216 SL-6706Z 303237092105501 02-01-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.048217 AC-7934Z 302821092171001 02-03-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.048218 JD-6909Z 302448092510501 05-09-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.048219 AC-7935Z 302132092234401 01-19-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.048221 JD-6835Z 301525092425701 05-10-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.048222 AC-7936Z 301906092272401 01-09-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.048223 AC-7976Z 301042092211101 02-17-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.048224 JD-6846Z 300626092462901 09-21-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.048225 AC-7938Z 300614092233001 02-10-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.048226 CN-5863Z 300216093042301 01-10-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.048226 CN-5863Z 300216093042301 05-10-00 <0.002 --- <0.002 --- <0.001 <0.001 --- <0.002 --- ---27 VE-10211Z 295932092284401 02-08-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.048228 JD-6847Z 301737093010301 01-26-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.048230 BE-6230Z 302723093144201 09-28-00 <0.002 <0.06 <0.002 <0.08 <0.001 <0.001 <0.061 <0.002 <0.022 <0.0482

Appendix 5. Pesticide concentrations in water from selected shallow wells in the rice-growing area in southwestern Louisiana, 2000-01[All concentrations are total recoverable and are in micrograms per liter. Detections are shown in bold. ACAD, Acadian-Pontchartrain Study Unit of the National Water-Quality 

Assessment Program (NAWQA); DOTD, Department of Transportation and Development; USGS, U.S. Geological Survey; numbers below the chemical names are the Chemical 

Abstracts Service (CAS) numbers; <, less than; ---, no data; E, estimated]
36

ACAD

well

number

Bentazon

H

25057-89-0

Bromacil

H

314-40-9

Bromoxynil

H

1689-84-5

Butylate

H

2008-41-5

Carbaryl

I

63-25-2

Carbofuran

I

1563-66-2

Chloramben

methyl ester

H

133-90-4

Chlorimuron

ethyl

H

90982-32-4

 Chlorothalonil

F

1897-45-6

 Chlorpyrifos

I

2921-88-2

Clopyralid

H

1702-17-6

Cyanazine

H

21725-46-2

Cycloate

H

1134-23-2

2,4-D

H

94-75-7

1 <0.02 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.082 <0.02 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.083 <0.02 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.084 <0.02 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.085 <0.02 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.086 E0.07 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.087 <0.02 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.088 E0.11 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.089 <0.02 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.08

10 <0.02 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.0811 <0.02 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.0813 E0.01 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.0814 <0.02 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 E0.008 <0.05 <0.004 <0.04 <0.004 <0.05 <0.0815 <0.02 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.0816 <0.02 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.0817 <0.02 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.0818 <0.02 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.0819 <0.02 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.0821 <0.02 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.0822 <0.02 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 E0.004 <0.04 <0.004 <0.05 <0.0823 <0.02 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.0824 <0.02 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 E0.01

25 <0.02 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.0826 <0.02 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.0826 --- --- --- <0.002 <0.003 <0.003 --- --- --- <0.004 --- <0.004 --- ---27 <0.02 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.0828 E0.15 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.0830 <0.02 <0.08 <0.06 <0.002 <0.003 <0.003 <0.11 <0.037 <0.05 <0.004 <0.04 <0.004 <0.05 <0.08

Appendix 5. Pesticide concentrations in water from selected shallow wells in the rice-growing area in southwestern Louisiana, 2000-01--Continued
37

ACAD

well

number

Dacthal 

(DCPA)

H

1861-32-1

Dacthal,

monoacid

H

887-54-7

2,4-DB

H

94-82-6

Diazinon

I

333-41-5

Dicamba 

H

1918-00-9

Dichlorprop

H

120-36-5

Dieldrin

I

60-57-1

 Dinoseb

H

88-85-7

Diphenamid

H

957-51-7

Disulfoton

I

298-04-4

Diuron

H

330-54-1

2,4-D

methyl ester

H

1928-38-7

EPTC

H

759-94-4

Ethalfluralin

H

55283-68-6

Ethopropos

I

13194-48-4

1 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.0032 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.0033 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.0034 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.0035 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.0036 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.0037 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.0038 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.0039 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.003

10 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.00311 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.00313 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 E0.007 <0.086 <0.002 <0.004 <0.00314 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.00315 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.00316 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.00317 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.00318 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.00319 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.00321 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.00322 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.00323 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.00324 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.00325 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.00326 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.00326 <0.002 --- --- <0.002 --- --- <0.001 --- --- <0.017 --- --- <0.002 <0.004 <0.00327 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.00328 <0.002 <0.07 <0.05 <0.002 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.00330 <0.002 <0.07 <0.05 0.007 <0.10 <0.05 <0.001 <0.04 <0.06 <0.017 <0.08 <0.086 <0.002 <0.004 <0.003

Appendix 5. Pesticide concentrations in water from selected shallow wells in the rice-growing area in southwestern Louisiana, 2000-01--Continued
38

ACAD

well

number

Fenuron

H

101-42-8

Fipronil

I

120068-37-3

Flumetsulam

H

98967-40-9

Fluometuron

H

2164-17-2

Fonofos

I

944-22-9

HCH, alpha

I

319-84-6

Imazaquin

H

81335-37-7

Imazethapyr

H

81335-77-5

Imidacloprid

I

13826-41-3

Lindane

I

58-89-9

Linuron

H

330-55-2

Malathion

I

121-75-5

MCPA

H

94-74-6

MCPB

H

94-81-5

Metalaxyl

F

57837-19-1

1 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 <0.088 <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.0572 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 E0.704 --- <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.0573 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 <0.088 <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.0574 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 --- <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.0575 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 <0.088 <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.0576 <0.07 <0.004 E0.0437 <0.06 <0.003 <0.002 <0.103 --- <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 E0.0057 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 E0.015 <0.088 <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.0578 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 --- <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.0579 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 --- <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.057

10 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 --- <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.05711 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 <0.088 <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.05713 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 <0.088 <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.05714 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 <0.088 <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.05715 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 <0.088 <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.05716 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 --- <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.05717 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 --- <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.05718 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 <0.088 <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.05719 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 --- <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.05721 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 <0.088 <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.05722 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 --- <0.1060 <0.004 <0.002 0.006 <0.06 <0.06 <0.057

23 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 <0.088 <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.05724 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 <0.088 <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.05725 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 <0.088 <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.05726 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 --- <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.05726 --- <0.004 --- --- <0.003 <0.002 --- --- --- <0.004 <0.002 <0.005 --- --- ---27 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 --- <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.05728 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 --- <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.05730 <0.07 <0.004 <0.0866 <0.06 <0.003 <0.002 <0.103 <0.088 <0.1060 <0.004 <0.002 <0.005 <0.06 <0.06 <0.057

Appendix 5. Pesticide concentrations in water from selected shallow wells in the rice-growing area in southwestern Louisiana, 2000-01--Continued
39

ACAD

well

number

Methiocarb

I

2032-65-7

Methomyl

I

16752-77-5

MethyI

parathion

I

298-00-0

Metolachlor

H

51218-45-2

Metribuzin

H

21087-64-9

Metsulfuron

methyl

H

74223-64-6

Molinate

H

2212-67-1

Napropamide

H

15299-99-7

Neburon

H

555-37-3

Nicosulfuron

H

111991-09-4

Norflurazon

H

27314-13-2

Oryzalin

H

19044-88-3

Oxamyl

I

23135-22-0

Parathion

I

56-38-2

1 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.0042 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.0043 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 E0.003 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.0044 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.0045 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.0046 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.0047 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.0048 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.0049 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.004

10 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.00411 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.00413 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.00414 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.00415 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.00416 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.00417 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.00418 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.00419 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.00421 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.00422 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.00423 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.00424 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.00425 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.00426 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.00426 --- --- <0.006 <0.002 <0.004 --- <0.004 <0.003 --- --- --- --- --- <0.00427 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.00428 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.00430 <0.08 <0.08 <0.006 <0.002 <0.004 <0.1138 <0.004 <0.003 <0.07 <0.065 <0.08 <0.07 <0.02 <0.004

Appendix 5. Pesticide concentrations in water from selected shallow wells in the rice-growing area in southwestern Louisiana, 2000-01--Continued
40

ACAD

well

number

Pebulate

H

1114-71-2

Pendimethalin

H

40487-42-1

cis-Permethrin

I

52341-33-0

Phorate

I

298-02-2

Picloram

H

1918-02-1

Prometon

H

1610-18-0

Pronamide

H

23950-58-5

Propachlor

H

1918-16-7

Propanil

H

709-98-8

Propargite

I

2312-35-8

Propham

H

122-42-9

Propiconazole

F

60207-90-1

1 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.0642 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.0643 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.0644 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.0645 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.0646 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.0647 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.0648 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.0649 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.064

10 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.06411 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.06413 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.06414 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.06415 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.06416 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.06417 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.06418 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.06419 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.06421 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.06422 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.06423 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.06424 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.06425 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.06426 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.06426 <0.004 <0.004 <0.005 <0.002 --- <0.018 <0.003 <0.007 <0.004 <0.013 --- ---27 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.06428 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.06430 <0.004 <0.004 <0.005 <0.002 <0.07 <0.018 <0.003 <0.007 <0.004 <0.013 <0.07 <0.064

Appendix 5. Pesticide concentrations in water from selected shallow wells in the rice-growing area in southwestern Louisiana, 2000-01--Continued
41

ACAD

well

number

Propoxur

I

204-043-8

Siduron

H

1982-49-6

Simazine

H

122-34-9

Sulfometuron

methyl

H

74222-97-2

Tebuthiuron

H

34014-18-1

Terbacil

H

5902-51-2

Terbufos

I

13071-79-9

Thiobencarb

H

28249-77-6

Tri-allate

H

2303-17-5

Tribenuron 

methyl

H

101200-48-0

Triclopyr

H

55335-06-3

Trifluralin

H

1582-09-8

1 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.002

2 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.002

3 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.002

4 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.002

5 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.002

6 <0.06 <0.093 <0.005 <0.039 E0.008 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.0027 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.002

8 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.002

9 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.002

10 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.00211 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.00213 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.00214 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.00215 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.00216 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.00217 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.00218 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.00219 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.00221 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.00222 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.00223 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.00224 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.00225 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.00226 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.00226 --- --- <0.005 --- <0.010 <0.007 <0.013 <0.002 <0.001 --- --- <0.00227 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.00228 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.00230 <0.06 <0.093 <0.005 <0.039 <0.010 <0.007 <0.013 <0.002 <0.001 <0.07 <0.10 <0.002

Appendix 5. Pesticide concentrations in water from selected shallow wells in the rice-growing area in southwestern Louisiana, 2000-01--Continued
42

ACAD

well

number

DOTD local

well number

USGS site

identification

number

Sample

date

Aldicarb

sulfone

DP (aldicarb)

1646-88-4

Aldicarb

sulfoxide

DP (aldicarb)

1646-87-3

3-hydroxycarbofuran

DP (carbofuran)

16655-82-6

DDE, p,p’

DP (DDT)

72-55-9

Deethylatrazine

DP (atrazine)

6190-65-4

Deethyldeisopropylatrazine

DP (atrazine)

3397-62-4

DeisopropylatrazineDP (atrazine)

1007-28-9

2,6-diethylaniline

DP (alachlor)

579-66-8

1 AL-5475Z 303839092435101 05-02-00 <0.16 <0.03 <0.06 <0.006 <0.001 <0.06 <0.07 <0.0032 EV-5477Z 303741092213901 01-27-00 <0.16 --- <0.06 <0.006 <0.001 <0.06 <0.07 <0.0033 AL-5477Z 302927092490001 05-25-00 <0.16 <0.03 <0.06 <0.006 <0.001 <0.06 <0.07 <0.0034 EV-5482Z 302952092325501 01-26-00 <0.16 --- <0.06 <0.006 <0.001 <0.06 <0.07 <0.0035 JD-6843Z 302220092570201 01-11-00 <0.16 <0.03 <0.06 <0.006 <0.001 <0.06 <0.07 <0.0036 JD-6844Z 302246092400101 01-25-00 <0.16 --- <0.06 <0.006 <0.001 E0.02 <0.07 <0.0037 JD-6834Z 301451092541401 01-12-00 <0.16 <0.03 <0.06 <0.006 <0.001 <0.06 <0.07 <0.0038 AC-7869Z 301444092211501 01-13-00 <0.16 <0.03 <0.06 <0.006 <0.001 <0.06 <0.07 <0.0039 JD-6845Z 301003092561301 01-18-00 <0.16 <0.03 <0.06 <0.006 <0.001 <0.06 <0.07 <0.003

10 AC-7977Z 300659092352901 02-09-00 <0.16 --- <0.06 <0.006 <0.001 <0.06 <0.07 <0.00311 VE-10210Z 295531092132001 05-23-00 <0.16 <0.03 <0.06 <0.006 E0.008 <0.06 <0.07 <0.00313 EV-5470Z 304121092293301 02-15-00 <0.16 <0.03 <0.06 <0.006 <0.001 <0.06 <0.07 <0.00314 EV-5486Z 303616092331801 02-16-00 <0.16 <0.03 <0.06 <0.006 <0.001 <0.06 <0.07 <0.00315 AL-5479Z 303127092404801 05-11-00 <0.16 <0.03 <0.06 <0.006 <0.001 E0.01 <0.07 <0.00316 SL-6706Z 303237092105501 02-01-00 <0.16 --- <0.06 <0.006 <0.001 <0.06 <0.07 <0.00317 AC-7934Z 302821092171001 02-03-00 <0.16 --- <0.06 <0.006 <0.001 <0.06 <0.07 <0.00318 JD-6909Z 302448092510501 05-09-00 <0.16 <0.03 <0.06 <0.006 <0.001 <0.06 <0.07 <0.00319 AC-7935Z 302132092234401 01-19-00 <0.16 <0.03 <0.06 <0.006 <0.001 <0.06 <0.07 <0.00321 JD-6835Z 301525092425701 05-10-00 <0.16 <0.03 <0.06 <0.006 <0.001 <0.06 <0.07 <0.00322 AC-7936Z 301906092272401 01-09-00 <0.16 <0.03 <0.06 <0.006 <0.001 <0.06 <0.07 <0.00323 AC-7976Z 301042092211101 02-17-00 <0.16 <0.03 <0.06 <0.006 <0.001 <0.06 <0.07 <0.00324 JD-6846Z 300626092462901 09-21-00 <0.16 <0.03 <0.06 <0.006 <0.001 <0.06 <0.07 <0.00325 AC-7938Z 300614092233001 02-10-00 <0.16 <0.03 <0.06 <0.006 <0.001 <0.06 <0.07 <0.00326 CN-5863Z 300216093042301 01-10-00 <0.16 <0.03 <0.06 <0.006 <0.001 E.004 <0.07 <0.00326 CN-5863Z 300216093042301 05-10-00 --- --- --- E0.001 <0.001 --- --- <0.00327 VE-10211Z 295932092284401 02-08-00 <0.16 --- <0.06 <0.006 <0.001 <0.06 <0.07 <0.00328 JD-6847Z 301737093010301 01-26-00 <0.16 --- <0.06 <0.006 <0.001 <0.06 <0.07 <0.00330 BE-6230Z 302723093144201 09-28-00 <0.16 <0.03 <0.06 E0.002 <0.001 <0.06 <0.07 <0.003

Appendix 6. Concentrations of pesticide degradation products in water from selected shallow wells in the rice-growing area in southwestern Louisiana, 

2000-01

[All concentrations are total recoverable and are in micrograms per liter. Detections are shown in bold. ACAD, Acadian-Pontchartrain Study Unit of the National Water-Quality Assessment Program (NAWQA); 

DOTD, Department of Transportation and Development; USGS, U.S. Geological Survey; DP, parent compound in parenthesis of degradation product; numbers below the chemical names are the Chemical Abstracts 

Service (CAS) numbers; <, less than; ---, no data; E, estimated]
43

ACAD

well

number

2,6-diethylaniline

DP (alachlor)

579-66-8

Desulfinylfipronil

DP (fipronil)

no CAS number

Fipronil

RPA

105048

DP (fipronil)

no CAS number

Fipronil

sulfide

DP (fipronil)

120067-83-6

Fipronil

sulfone

DP (fipronil)

120068-36-2

2-Hydroxyatrazine

DP (atrazine)

2163-68-0

3-Ketocarbofuran

DP (carbofuran)

16709-30-1

Methomyl

oxime

DP (methomyl)

16752-77-5

3 (4-chlorophenyl)

-1-

Methyl

urea

DP (neburon)

5352-88-5

Oxamyl

oxime

DP (oxamyl)

23135-22-0

1 <0.003 <0.010 <0.005 <0.010 <0.001 <0.193 <0.072 <0.0102 <0.0915 <0.0642 <0.003 --- <0.005 --- <0.001 <0.193 <0.072 <0.0102 <0.0915 <0.0643 <0.003 <0.010 <0.005 <0.010 <0.001 <0.193 <0.072 <0.0102 <0.0915 <0.0644 <0.003 --- <0.005 --- <0.001 <0.193 <0.072 <0.0102 <0.0915 <0.0645 <0.003 --- <0.005 --- <0.001 <0.193 <0.072 <0.2000 <0.0915 <0.0646 <0.003 --- <0.005 --- <0.001 E0.066 <0.072 <0.0102 <0.0915 <0.0647 <0.003 --- <0.005 --- <0.001 <0.193 <0.072 <0.0102 <0.0915 <0.0648 <0.003 --- <0.005 --- <0.001 <0.193 <0.072 <0.2000 <0.0915 <0.0649 <0.003 --- <0.005 --- <0.001 <0.193 <0.072 <0.2000 <0.0915 <0.064

10 <0.003 --- <0.005 --- <0.001 <0.193 <0.072 <0.0102 <0.0915 <0.06411 <0.003 <0.010 <0.005 <0.010 <0.001 <0.193 <0.072 <0.0102 <0.0915 <0.06413 <0.003 --- <0.005 --- <0.001 <0.193 <0.072 <0.0102 0.2056 ---

14 <0.003 --- <0.005 --- <0.001 <0.193 <0.072 <0.0102 <0.0915 ---15 <0.003 <0.010 <0.005 <0.010 <0.001 <0.193 <0.072 <0.0102 <0.0915 <0.06416 <0.003 --- <0.005 --- <0.001 <0.193 <0.072 <0.0102 <0.0915 <0.06417 <0.003 --- <0.005 --- <0.001 <0.193 <0.072 <0.0102 <0.0915 <0.06418 <0.003 <0.010 <0.005 <0.010 <0.001 <0.193 <0.072 <0.0102 <0.0915 <0.06419 <0.003 --- <0.005 --- <0.001 <0.193 <0.072 <0.2000 <0.0915 <0.06421 <0.003 --- <0.005 --- <0.001 <0.193 <0.072 <0.0102 <0.0915 <0.06422 <0.003 --- <0.005 --- <0.001 <0.193 <0.072 <0.2000 <0.0915 <0.06423 <0.003 --- <0.005 --- <0.001 <0.193 <0.072 <0.0102 <0.0915 ---24 <0.003 <0.010 <0.005 <0.010 <0.001 <0.193 <0.072 <0.0102 <0.0915 <0.06425 <0.003 --- <0.005 --- <0.001 <0.193 <0.072 <0.0102 <0.0915 ---26 <0.003 --- E0.001 --- 0.005 <0.193 <0.072 <0.2000 <0.0915 <0.064

26 <0.003 --- <0.005 --- <0.001 --- --- --- --- ---27 <0.003 --- <0.005 --- <0.001 <0.193 <0.072 <0.0102 <0.0915 <0.06428 <0.003 --- <0.005 --- <0.001 <0.193 <0.072 <0.0102 <0.0915 <0.06430 <0.003 <0.010 <0.005 <0.010 <0.001 <0.193 <0.072 <0.0102 <0.0915 <0.064

Appendix 6. Concentrations of pesticide degradation products in water from selected shallow wells in the rice-growing area in southwestern Louisiana, 

2000-01--Continued
44

ACAD

well

number

DOTD local

well number

USGS site

identification

number

Sample

date

Sample

time

Radon 222,

 total

(pCi/L)

14859-67-7

Radon-222,

2-sigma

precision

estimate

(pCi/L)

CFC-11

trichlorofluoromethane

(pg/kg)

75-69-4

CFC-113

trichlorotrifluoroethane

(pg/kg)

76-13-1

CFC-12

dichlorodifluoromethane 

(pg/kg)

75-71-1

Apparent

modeled

groundwater

sample 

age

Hydrogen,

 2 / 1

ratio per 

mil,

no CAS 

number

Oxygen,

 18 / 16

ratio per 

mil,

no CAS 

number

1 303839092435101 AL-5475Z 5/2/00 1200 354 24 --- --- --- --- --- ---

1 303839092435101 AL-5475Z 3/6/01 1300 --- --- 2 0 7 48 -19.2 -4.04

2 303741092213901 EV-5477Z 1/27/00 1000 852 28 --- --- --- --- --- ---

2 303741092213901 EV-5477Z 2/28/01 1200 --- --- 90 10 100 26 -11.9 -2.50

3 302927092490001 AL-5477Z 5/25/00 1000 268 19 --- --- --- --- --- ---

3 302927092490001 AL-5477Z 3/7/01 1100 --- --- 10 0 10 43 -13.0 -2.68

4 302952092325501 EV-5482Z 1/26/00 1100 933 29 --- --- --- --- --- ---

4 302952092325501 EV-5482Z 2/28/01 0900 --- --- 20 0 10 43 -19.1 -3.68

5 302220092570201 JD-6843Z 1/11/00 1000 1,130 32 --- --- --- --- --- ---

5 302220092570201 JD-6843Z 2/14/01 0900 --- --- 30 --- 30 37 -18.4 -3.87

6 302246092400101 JD-6844Z 1/25/00 1100 1,020 30 --- --- --- --- --- ---

6 302246092400101 JD-6844Z 2/21/01 1100 --- --- 200 20 100 23 -11.3 -2.72

7 301451092541401 JD-6834Z 1/12/00 1000 799 27 --- --- --- --- --- ---

7 301451092541401 JD-6834Z 2/20/01 1100 --- --- 8 0 8 49 -15.3 -3.00

8 301444092211501 AC-7869Z 1/13/00 1100 889 29 --- --- --- --- --- ---

8 301444092211501 AC-7869Z 2/15/01 1000 --- --- 5 0 20 38 -11.2 -2.58

9 301003092561301 JD-6845Z 1/18/00 1000 961 30 --- --- --- --- --- ---

9 301003092561301 JD-6845Z 2/27/01 1200 --- --- 5 0 10 44 -10.0 -1.69

11 295531092132001 VE-10210Z 5/23/00 1400 481 24 --- --- --- --- --- ---

11 295531092132001 VE-10210Z 2/19/01 1200 --- --- 20 2 60 29 -14.0 -3.16

13 304121092293301 EV-5470Z 2/15/00 1100 799 27 --- --- --- --- --- ---

14 303616092331801 EV-5486Z 2/16/00 1100 800 30 --- --- --- --- --- ---

14 303616092331801 EV-5486Z 3/2/01 1100 --- --- 200 20 100 21 -13.5 -2.42

15 303127092404801 AL-5479Z 5/11/00 1000 216 20 --- --- --- --- --- ---

16 303237092105501 SL-6706Z 2/1/00 0900 995 30 --- --- --- --- --- ---

16 303237092105501 SL-6706Z 2/26/01 0900 --- --- 20 3 40 35 -19.7 -3.92

17 302821092171001 AC-7934Z 2/3/00 1000 776 27 --- --- --- --- --- ---

17 302821092171001 AC-7934Z 2/26/01 1200 --- --- 10 0 10 46 -15.9 -2.91

18 302448092510501 JD-6909Z 5/9/00 1100 453 23 --- --- --- --- --- ---

19 302132092234401 AC-7935Z 2/26/01 1400 1,340 34 100 20 100 17 -10.1 -1.80

21 301525092425701 JD-6835Z 5/10/00 1400 991 31 --- --- --- --- --- ---

21 301525092425701 JD-6835Z 2/21/01 0900 --- --- 100 20 200 19 -11.9 -2.82

22 301906092272401 AC-7936Z 2/14/01 1200 --- --- 7 2 20 42 -13.2 -3.26

23 301042092211101 AC-7976Z 2/17/00 1200 828 27 --- --- --- --- --- ---

23 301042092211101 AC-7976Z 2/15/01 1200 --- --- 6 0 6 46 -14.3 -3.58

24 300626092462901 JD-6846Z 9/21/00 1400 303 22 --- --- --- --- --- ---

24 300626092462901 JD-6846Z 2/27/01 1000 --- --- 20 --- 60 31 -18.5 -3.79

25 300614092233001 AC-7938Z 2/10/00 1000 780 28 --- --- --- --- --- ---

25 300614092233001 AC-7938Z 2/19/01 0900 --- --- 10 0 7 46 -15.5 -3.40

26 300216093042301 CN-5863Z 1/10/00 1400 509 22 --- --- --- --- --- ---

27 295932092284401 VE-10211Z 3/9/01 1100 --- --- 100 20 80 27 -12.0 -2.78

28 301737093010301 JD-6847Z 1/11/00 1500 1,450 34 --- --- --- --- --- ---

28 301737093010301 JD-6847Z 2/13/01 1800 --- --- 70 7 100 27 -13.7 -3.26

30 302723093144201 BE-6230Z 9/28/00 0800 456 23 --- --- --- --- --- ---

Appendix 7. Radon, chlorofluorocarbons, and stable isotope concentrations in water from selected shallow wells in 

the rice-growing area in southwestern Louisiana, 2000-01

[ACAD, Acadian-Pontchartrain Study Unit of the National Water-Quality Assessment Program (NAWQA); DOTD, Department of Transportation and 

Development; USGS, U.S. Geological Survey; pCi/L, picocuries per liter; numbers below the chemical names are the Chemical Abstracts Service (CAS) numbers; 

pg/kg, picograms per kilogram; 2/1, 1

H and 2H; 18/16, 18O/16O, ---, no data]