U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 03–4182

Comparison Between Agricultural and Urban 

Ground-Water Quality in the Mobile River Basin, 

1999–2001

By James L. Robinson

Montgomery, Alabama

2003

NATIONAL WATER-QUALITY ASSESSMENT PROGRAM
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

CHARLES G. GROAT, Director

For additional information write to: Copies of this report can be purchased from:

District Chief U.S. Geological Survey

U.S. Geological Survey Branch of Information Services

2350 Fairlane Drive, Suite 120 Box 25286, Federal Center

Montgomery, AL 36116 Denver, CO 80225

email: dc_al@usgs.gov 1-888-ASK-USGS (275-8747)

Information about U.S. Geological Survey programs in Alabama can be obtained on the World Wide Web at 

http://al.water.usgs.gov.

The use of firm, trade, and brand names in this report is for identification purposes only and 

does not constitute endorsement by the U.S. Government.

Cover photographs—Top: Two views of the Tallapoosa River near Milstead, Alabama. Right: Railroad crossing 

over the Tallapoosa River near Tallassee, Alabama (just upstream from Milstead), with Thurlow Dam in the background. Bottom: Agricultural field near Milstead, Alabama (photographs taken by D.A. Harned, U.S. Geological Survey).
FOREWORD

Foreword III

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 longterm 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 WaterQuality 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 and priorities. 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, multiscale 

approach helps to determine if certain types of waterquality 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, nongovernment organizations, industry, academia, and 

other stakeholder groups. The assistance and 

suggestions of all are greatly appreciated.

Robert M. Hirsch

Associate Director for Water
Contents V

CONTENTS

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

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

Purpose and scope .......................................................................................................................................................... 2

Previous investigations ................................................................................................................................................... 4

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

Environmental setting of the Mobile River Basin................................................................................................................. 4

Description of the study area.......................................................................................................................................... 7

Hydrogeology of the study area ..................................................................................................................................... 9

Study design and methods..................................................................................................................................................... 9

Land use and land cover ................................................................................................................................................. 11

Monitoring well network................................................................................................................................................ 11

Water-quality samples .................................................................................................................................................... 11

Quality-assurance and quality-control procedures ......................................................................................................... 15

Graphical and statistical methods................................................................................................................................... 17

Chemical and physical properties of the shallow sediments................................................................................................. 17

Soil characteristics.......................................................................................................................................................... 17

Sediment core analyses................................................................................................................................................... 18

Lithology of the shallow sediments................................................................................................................................ 18

Shallow aquifer properties.............................................................................................................................................. 18

Ground-water quality ............................................................................................................................................................ 18

Physical properties.......................................................................................................................................................... 18

Major ions....................................................................................................................................................................... 20

Nutrients and dissolved organic carbon.......................................................................................................................... 21

Pesticides ........................................................................................................................................................................ 22

Age of ground water....................................................................................................................................................... 22

Relations among ground-water quality, ground-water age, and land use ............................................................................. 25

Summary ............................................................................................................................................................................... 27

References ............................................................................................................................................................................. 28

Appendix .............................................................................................................................................................................. 31

FIGURES

1–4. Map showing:

 1. Locations of major rivers and cities in the Mobile River Basin....................................................................... 3

 2. Generalized geology of the Mobile River Basin.............................................................................................. 5

 3. Physiographic units of the Mobile River Basin ............................................................................................... 6

 4. Location of agricultural and urban study areas in the Mobile River Basin ..................................................... 8

5. Diagram showing generalized section of stratigraphic and hydrogeologic units underlying the 

agricultural and urban study areas in the Mobile River Basin .............................................................................. 9

6. Diagram showing generalized hydrogeologic sections A-A' and B-B' in the agricultural and urban 

study areas of the Mobile River Basin .................................................................................................................. 10

7. Map showing locations of agricultural and urban wells sampled in the Mobile River Basin, 

and lines of sections A-A' and B-B' ...................................................................................................................... 12

8. Boxplots showing concentrations of selected water-quality constituents in ground water collected

from agricultural and urban wells in the Mobile River Basin .............................................................................. 20

9. Piper trilinear diagram showing major ion composition of ground water collected from agricultural wells

and the reference well ........................................................................................................................................... 21

10. Boxplots showing concentrations of magnesium in ground water collected from agricultural and urban 

wells in the Mobile River Basin ............................................................................................................................ 21

11. Boxplots showing concentrations of nitrite plus nitrate in ground water collected from agricultural and

urban wells in the Mobile River Basin.................................................................................................................. 22

12. Graph showing detection frequencies of selected pesticides in ground water collected from agricultural

wells in the Mobile River Basin ............................................................................................................................ 23
VI Contents

13. Graph showing range and distribution of concentrations of selected pesticides in ground water

collected from agricultural wells in the Mobile River Basin................................................................................. 24

14. Piper trilinear diagram showing major ion composition and age of selected ground water collected 

from agricultural wells .......................................................................................................................................... 26

TABLES

1. Ground-water resources of the Mobile River Basin................................................................................................. 7

2. Selected 1992 and 1997 statistics for agricultural study area, by county................................................................. 7

3. Predominant crop and land-use types within a 0.3-mile radius of the agricultural wells 

in the Mobile River Basin...................................................................................................................................... 13

4. Constituents analyzed and analytical methods used for agricultural ground-water samples collected 

in the Mobile River Basin...................................................................................................................................... 14

5. Summary of quality-control samples collected during sampling of the agricultural wells 

in the Mobile River Basin...................................................................................................................................... 15

6. Descriptive statistics for quality-control samples collected for pesticide analysis during sampling of the

agricultural wells in the Mobile River Basin ......................................................................................................... 16

7. Minimum, median, and maximum values of selected physical properties and chemical constituents 

in ground water collected from agricultural and urban wells in the Mobile River Basin...................................... 19

8. Maximum concentrations of selected pesticides in ground water collected from agricultural wells 

in the Mobile River Basin...................................................................................................................................... 23

9. Detection frequencies of selected pesticides in ground water from agricultural and urban wells 

collected using common laboratory reporting levels ............................................................................................. 24

10. Depths to well screens and ages of ground water collected from agricultural and urban wells 

in the Mobile River Basin...................................................................................................................................... 25

11. Correlation coefficients for selected physical properties and constituents in ground water

collected from agricultural wells in the Mobile River Basin................................................................................. 26

CONVERSION FACTORS, DATUMS, DEFINITIONS, and ABBREVIATIONS and ACRONYMS 

Vertical and horizontal datums:

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 (NAVD 88). Historical data collected

and stored as National Geodetic Vertical Datum of 1929 (NGVD of 1929) have been converted to NAVD 88 for use in this 

publication.

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83). Historical data collected and 

stored as North American Datum of 1927 (NAD 27) have been converted to NAD 83 for use in this publication.

Multiply By To obtain

Length

inch (in.) 2.54 centimeter

foot (ft) 0.3048 meter

mile (mi) 1.609 kilometer

Area

square mile (mi2

) 2.590 square kilometer 

Volume

gallon (gal) 3.785 liter

Flow rate

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

million gallons per day per square mile

 [(Mgal/d)/mi2

] 1,460 cubic meter per day per square kilometer 

Hydraulic conductivity

foot per day (ft/d) 0.3048 meter per day
Contents VII

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

°C = (° F - 32) / 1.8

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

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

Additional abbreviations and acronyms used in this report:

BWRA Black Warrior River aquifer

C-18 octadecyl

CFC chlorofluorocarbon

CaCo3 calcium carbonate

CFC-11 trichlorofluoromethane (CFCl3)

CFC-12 dichlorodifluoromethane (CF2Cl2)

CFC-113 trichlorotrifluoroethane (C2F3Cl3)

CO2 carbon dioxide

CO3 carbonate ion

ECD electron capture device

HCO3 bicarbonate ion

in/mo inch per month

LRL laboratory reporting level

LTMDL long-term method detection level

MCL U.S. Environmental Protection Agency drinking-water maximum contaminant level

MDL method detection level

NAWQA National Water-Quality Assessment

NWQL National Water Quality Laboratory

QA/QC quality assurance and quality control

RSD USEPA risk-specific dose health advisory for drinking water

SF6 sulfur hexafluoride

SPE solid-phase extraction

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

UV ultraviolet
Abstract 1

Comparison Between Agricultural and Urban 

Ground-Water Quality in the Mobile River Basin, 

1999–2001

By James L. Robinson

ABSTRACT

The Black Warrior River aquifer is a major 

source of public water supply in the Mobile River 

Basin. The aquifer outcrop trends northwest-southeast 

across Mississippi and Alabama. A relatively thin 

shallow aquifer overlies and recharges the Black 

Warrior River aquifer in the flood plains and terraces of 

the Alabama, Coosa, Black Warrior, and Tallapoosa 

Rivers. Ground water in the shallow aquifer and the 

Black Warrior River aquifer is susceptible to 

contamination due to the effects of land use. Groundwater quality in the shallow aquifer and the shallow 

subcrop of the Black Warrior River aquifer, underlying 

an agricultural and an urban area, is described and 

compared.

The agricultural and urban areas are located in 

central Alabama in Autauga, Elmore, Lowndes, 

Macon, Montgomery, and Tuscaloosa Counties. Row 

cropping in the Mobile River Basin is concentrated 

within the flood plains of major rivers and their 

tributaries, and has been practiced in some of the fields 

for nearly 100 years. Major crops are cotton, corn, and 

beans. Crop rotation and no-till planting are practiced, 

and a variety of crops are grown on about one-third of 

the farms. Row cropping is interspersed with pasture 

and forested areas. In 1997, the average farm size in the 

agricultural area ranged from 196 to 524 acres. The 

urban area is located in eastern Montgomery, Alabama, 

where residential and commercial development 

overlies the shallow aquifer and subcrop of the Black 

Warrior River aquifer. Development of the urban area 

began about 1965 and continued in some areas through 

1995. The average home is built on a 1/8- to 1/4-acre 

lot. 

Ground-water samples were collected from 

29 wells in the agricultural area, 30 wells in the urban 

area, and a reference well located in a predominately 

forested area. The median depth to the screens of the 

agricultural and urban wells was 22.5 and 29 feet, 

respectively. Ground-water samples were analyzed for 

physical properties, major ions, nutrients, and 

pesticides. Samples from 8 of the agricultural wells and 

all 30 urban wells were age dated using analyses of 

chlorofluorocarbon, sulfur hexafluoride, and dissolved 

gases. Ground water sampled from the agricultural 

wells ranged in age from about 14 to 34 years, with a 

median age of about 18.5 years. Ground water sampled 

from the urban wells ranged in age from about 1 to 

45 years, with a median age of about 12 years. The ages 

estimated for the ground water are consistent with the 

geology and hydrology of the study area and the design 

of the wells.

All of the agricultural and urban wells sampled 

for this study produce water from the shallow aquifer 

that overlies and recharges the Black Warrior River 

aquifer, or from the uppermost unit of the Black 

Warrior River aquifer. The wells are located in the same 

physiographic setting, have similar depths, and the 

water collected from the wells had a similar range in 

age. Statistically significant differences in groundwater quality beneath the agricultural and urban areas 

can reasonably be attributed to the effects of land use. 

Ground water from the agricultural wells 

typically had acidic pH values and low specific 

conductance and alkalinity values. The water contained 

few dissolved solids, and typically had small 

concentrations of ions. Some of the agricultural 

ground-water contained concentrations of ammonia, 

nitrite plus nitrate, phosphorus, orthophosphate, and 
2 Comparison Between Agricultural and Urban Ground-Water Quality in the Mobile River Basin, 1999 – 2001

dissolved organic carbon in concentrations that 

exceeded those typically found in ground water. 

Pesticides were detected in ground water collected 

from 25 of the 29 agricultural wells. Nineteen different 

pesticide compounds were detected a total of 83 times. 

Herbicides were the most frequently detected class of 

pesticides. The greatest concentration of any pesticide 

was an estimated value of 1.4 microgram per liter of 

fluometuron.

The Wilcoxan rank sum test was used to 

determine statistically significant differences in water 

quality between the agricultural and urban ground 

water. Ground water from the agricultural and urban 

areas had a similar range of values for most physical 

properties, major ions, and age. Ground water from the 

agricultural area contained statistically greater 

concentrations of magnesium than ground water from 

the urban area. Fewer pesticide compounds were 

detected in the agricultural ground water than in the 

urban ground water. The total number of pesticide 

detections also was less in the agricultural ground 

water than in the urban ground water. Atrazine was the 

only manmade compound detected frequently enough 

in both data sets to allow statistical comparison. There 

was no statistical difference in atrazine concentrations 

between ground water from the agricultural and urban 

areas.

The Spearman rho and Kendall tau tests were 

used to test for statistically significant covariance 

among selected constituents in the agricultural ground 

water and for crop type. The concentration of nitrite 

plus nitrate increased as the concentration of 

magnesium and the number of pesticides detected 

increased. This correlation is attributed to land 

application of nitrogen-based fertilizer to enhance 

yield, crushed limestone and dolomite (which contain 

magnesium) to raise the acidic pH of the soil, and to the 

application pesticides. No correlation was found 

between crop type and ground-water quality, the 

concentrations of pesticides, or the number of 

pesticides detected in the agricultural ground water.

This lack of correlation probably is a result of such 

practices as crop rotation and the simultaneous 

cultivation of a variety of crops.

INTRODUCTION

Ground water is the source of drinking water for 

approximately 50 percent of the Nation (U.S. 

Geological Survey, 1999a). Degradation of groundwater quality as a result of various land-use practices is 

a major concern, not only because of its use for public 

water supply, but also because of the potential for 

ground water to affect surface-water quality. This study 

examined the effects of agricultural and urban land use 

on shallow ground-water quality in the Mobile River 

Basin (fig. 1).

 Agriculture in the Mobile River Basin is 

concentrated in the flood plains of the major rivers and 

their tributaries. The primary row crops include corn, 

soybeans, cotton, wheat, and sorghum (Johnson and 

others, 2002). Land use in the urban area, which is 

located in eastern Montgomery, Alabama, is primarily 

a mixture of high- to low-density residential, 

commercial, light industry, and forested areas. The 

agricultural and urban wells sampled for this study 

produce water from the same aquifers, are located in 

the same physiographic settings, and have similar 

ranges and median values for depth.

The U.S. Geological Survey (USGS) National 

Water-Quality Assessment (NAWQA) Program was 

designed to assess the status and trends in the quality of 

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

major river basins (also referred to as Study Units); and 

to link the status and trends in order to better 

understand the natural and human factors that affect the 

quality of water (Gilliom and others, 1995). The study 

described in this report is part of the NAWQA Program 

investigation of the Mobile River Basin in Alabama, 

Georgia, Mississippi, and Tennessee (fig. 1). 

Purpose and Scope

The purposes of this report are to describe and 

compare ground-water quality in a shallow aquifer and 

the shallow subcrop of the Black Warrior River aquifer 

beneath agricultural and urban land-use areas of the 

Mobile River Basin. Hydrologic and geologic data 

collected during the drilling of 60 wells were used to 

describe the hydrogeology of the shallow aquifers. 

Water-quality samples were collected from 29 

agricultural wells, 30 urban wells, and 1 reference well 

located in a forested area. All ground-water samples 

were analyzed for physical properties, major ions, 

nutrients, and pesticides. Samples from 8 agricultural 

wells and 30 urban wells were analyzed for 

chlorofluorocarbons, dissolved gases, and sulfur 

hexafluoride to estimate the recharge date (age) of the 

water. Ground-water samples were collected from the 

urban wells from October 1999 through January 2000, 
Introduction 3

Figure 1. Locations of major rivers and cities in the Mobile River Basin (from Robinson, 2002).
4 Comparison Between Agricultural and Urban Ground-Water Quality in the Mobile River Basin, 1999 – 2001

and from the agricultural and reference wells from June 

through December 2001. Nonparametric statistical 

analysis was used to check for significant differences 

between agricultural and urban ground-water quality. 

Correlation analysis was used to determine covariance 

between selected factors, such as land use, well depth, 

crop type, and ground-water quality.

Previous Investigations

Reports that describe the geology of the study 

area date back approximately 140 years when Tuomey 

(1858) included a report on part of the Cretaceous 

Formations of Alabama in the second biennial report of 

the Geological Survey of Alabama. Osborne and others 

(1989) prepared the current geologic map of Alabama; 

and King and Biekman (1974) prepared a geologic map 

of the conterminous United States, from which the 

geologic map for the Mobile River Basin (fig. 2) was 

derived. 

Reports describing the ground-water resources 

for the agricultural and urban land-use areas date back 

to Smith (1907). Scott (1957, 1960a, 1960b) describes 

the ground-water resources of Lowndes, Autauga, and 

Macon Counties, respectively. Gillett and Hunter 

(1990) prepared a report describing the water resources 

of Lowndes County. Knowles and others (1960, 1963) 

published the results of an exhaustive study of the 

geology and ground-water resources of Montgomery 

County. A report by Paulson and others (1962) 

summarizes the ground-water resources and geology of 

Tuscaloosa County, Alabama. Lines (1975) describes 

the water resources of Elmore County, Alabama. 

DeJarnette and Crownover (1987) and Scott and others 

(1987) prepared reports describing the geohydrology 

and susceptibility of major aquifers to surface 

contamination for areas encompassing the agricultural 

land-use area. Water quality of the Black Warrior River 

aquifer (BWRA) in rural areas, and in a residential and 

commercial area of Montgomery, Alabama, was 

summarized in Robinson (2002). The results of 

analyses of ground water collected from the rural, 

urban, and agricultural wells were published in 

Pearman and others (2000, 2001, 2002, 2003). The 

nomenclature documented by Miller (1990) and 

Renken (1998) for the ground-water aquifer systems in 

the Mobile River Basin is used herein. 

Acknowledgments 

The author gratefully acknowledges the 

cooperation and assistance provided by the many 

private citizens of Alabama who allowed access to their 

property for data collection. W.T. Dozier, Clifford W. 

Cleveland, II, Milton A. Wendland, Lloyd Emfinger, 

Jr., Paul Taylor, and Tony Cofer of the Alabama 

Department of Agricultural and Industries; Charles 

Mitchell and James Bannon of Auburn University; Pam 

Mason, David Barrow, and John Harris of the U.S. 

Department of Agriculture-Natural Resources 

Conservation Service; and Andrew Farqhuer of the 

Alabama Department of Corrections all deserve special 

thanks for their help. 

ENVIRONMENTAL SETTING OF THE MOBILE 

RIVER BASIN

 The Mobile River Basin encompasses about 

44,000 square miles (mi2

) in Alabama, Georgia, 

Mississippi, and Tennessee (fig. 1). The major surfacewater systems are the Cahaba, Coosa, and Tallapoosa, 

which are tributary to the Alabama River; and the 

Black Warrior River, which is tributary to the 

Tombigbee River (fig. 1). The Alabama and Tombigbee 

Rivers join to form the Mobile River in the southern 

part of the basin. The Mobile River Basin has diverse 

geology (fig. 2) and physiography (fig. 3). A detailed 

discussion of the Mobile River Basin environmental 

setting is presented by Johnson and others (2002).

Ground water is an important resource in the 

Mobile River Basin. Total ground-water use in 1995 

was estimated to be about 328 million gallons per day 

(Mgal/d) [table 1; Strom and Mallory (1995), Fanning 

(1997), and Mooty and Richardson (1998)], which 

accounted for about 24 percent of the total water use in 

the basin. Ground-water withdrawals are concentrated 

in the Black Warrior River aquifer (166 Mgal/d), which 

is composed of clastic sediments of Cretaceous age, 

and in the Valley and Ridge aquifers (83 Mgal/d), 

which are solution-conduit aquifers developed in 

carbonate rocks of Devonian through Cambrian age 

(fig. 2). Fifty-one percent of the ground water used for 

public water supply in the Mobile River Basin is 

withdrawn from the Black Warrior River aquifer 

(table 1). In the outcrop and shallow subcrop areas, the 

Black Warrior River aquifer is susceptible to 

contamination due to the effects of land use.
Environmental Setting of the Mobile River Basin 5

Figure 2. Generalized geology of the Mobile River Basin (from Robinson, 2002).
6 Comparison Between Agricultural and Urban Ground-Water Quality in the Mobile River Basin, 1999 – 2001

Figure 3. Physiographic units of the Mobile River Basin (from Robinson, 2002).
Environmental Setting of the Mobile River Basin 7

Table 2. Selected 1992 and 1997 statistics for agricultural study area, by county 

[Data from the U.S. Department of Agriculture, www.nass.usda.gov/census/census97/highlights/ag-state.htm, accessed January 2003] 

County Average farm size 

(acres)

Acres of

cotton

Acres of corn for 

grain or seed

Acres of 

soybeans

Acres of wheat 

for grain

Autauga 301 9,956 1,035 1,381 1,340

Elmore 222 19,393 2,167 1,371 640

Lowndes 524 7,725a 2,575 4,126a

a

 1997 data not reported, data from 1992 were used.

 no data

Macon 424 5,964 1,045 455 330

Montgomery 368 1,372 975 2,241 722

Tuscaloosa 196 4,313 4,464 2,118 1,162

Total acres 48,723 12,261 11,692 4,194

Description of the Study Area

The study area lies within the flood plains of the 

Alabama, Coosa, Tallapoosa, and Black Warrior Rivers 

and their tributaries in the Alluvial-Deltaic Plain and 

Black Prairie Belt Physiographic Districts of the 

Coastal Plain Physiographic Province in central 

Alabama (fig. 3). Land-surface gradients generally are 

low to very low. Mixed deciduous and evergreen forests 

grow on the sandy, silty loam soil. Open pit sand and 

gravel mines operate near the major rivers. Abandoned 

pits fill with water and are sometimes used to irrigate 

crops.

 The agricultural area lies within six counties: 

Autauga, Elmore, Lowndes, Macon, Montgomery, and 

Tuscaloosa (fig. 4). In Alabama, row cropping occurs 

primarily within the flood plains of the major rivers and 

their tributaries. The primary row crops grown in the 

Mobile River Basin include cotton, corn, soybeans, 

wheat, and sorghum (Johnson and others, 2002). 

The urban area is located in eastern 

Montgomery, Alabama (fig. 4). The population of the 

Montgomery metropolitan area in 1998 was 

approximately 321,000 (U.S. Census Bureau, 2000). 

Land use in eastern Montgomery is primarily a mixture 

of high- to low-density residential, commercial, light 

industry, and forested areas. 

Mixed agriculture is typical, and multiple crop 

types are grown on many farms. Farming practices 

include no-till planting, rotating cotton and corn, and 

leaving fields fallow for a season. Many farmers also 

maintain pasture for cattle. Many of the farms are 

operated by second- or third-generation descendants of 

the original owners. This made it possible to determine 

that land use in the vicinity of most of the agricultural 

wells has not changed substantially in 25 to 50 years. 

Average farm size ranged from 196 to 524 acres 

Table 1. Ground-water resources of the Mobile River Basin

[Modified from Miller, 1990; Strom and Mallory, 1995; Fanning, 1997; Mooty and Richardson, 1998; and Renken, 1998; Mgal/d, million 

gallons per day]

Regional 

aquifer subunit

Physiographic

districts

(fig. 3)

Primary 

geology

(fig. 2)

Total 

population 

served (1995), 

in thousands

Total 

withdrawals 

(1995), 

in Mgal/d

Black Warrior River aquifer Fall Line Hills, 

Alluvial-Deltaic Plain, 

Black Prairie Belt

Cretaceous clastic sediments overlain 

by clastic sediments of the AlluvialDeltaic and Coastal Plain

 885 166

Valley and Ridge aquifers Valley and Ridge Devonian through Cambrian 

carbonate rocks

 429 83

Pearl River, Chickasawhay River, 

surficial aquifers

Southern Hills, 

Alluvial-Deltaic Plain

Oligocene, Eocene, and Paleocene 

clastic sediments and carbonate 

rocks

 179 41

 Piedmont and Blue Ridge 

aquifers

Piedmont and Blue 

Ridge

Igneous and metamorphic rocks of 

various and uncertain age

 192 21

Appalachian Plateaus aquifers Cumberland Plateaus Pennsylvanian and Mississippian 

sandstone and carbonate rocks

 130 17
8 Comparison Between Agricultural and Urban Ground-Water Quality in the Mobile River Basin, 1999 – 2001

Figure 4. Location of agricultural and urban study areas in the Mobile River Basin.
Study Design and Methods 9

Figure 5. Generalized section of stratigraphic and hydrogeologic units underlying the agricultural and urban study areas in 

the Mobile River Basin (after Scott, 1960b; Paulson and others, 1962; Knowles and others, 1963; Scott and others, 1987; Gillett

and Hunter, 1990; Miller, 1990).

(table 2). Selected agricultural statistics for 1992 and 

1997, published by the U.S. Department of 

Agriculture, show extensive row cropping for cotton, 

corn, soybeans, and wheat in the agricultural study area 

(table 2).

Hydrogeology of the Study Area

The study area is underlain, north to south, by 

alluvial and terrace deposits of gravel, sand, and clay; 

and by sands and clays of the uppermost part of the 

Black Warrior River aquifer (figs. 5 and 6). The alluvial 

and terrace deposits range from about 5 feet (ft) to more 

than 100 ft thick and form a shallow aquifer (figs. 5 and 

6) that overlies the uppermost part of the Black Warrior 

River aquifer with little or no hydraulic separation 

(DeJarnette and Crownover, 1987; Scott and others, 

1987).

Average annual rainfall in central Alabama 

ranges from about 51 to 57 inches (in.) (National 

Oceanic and Atmospheric Administration, 1999). 

Rainfall is seasonally distributed, with the greatest 

rainfall amounts occurring during the months of 

December through March [about 5–6 inches per 

month, (in/mo)]; and the smallest rainfall amounts 

occurring during the months of August through 

October (about 2–4 in/mo). Surface water drains to the 

Alabama, Coosa, Black Warrior, and Tallapoosa 

Rivers. North of the Cretaceous chalk (figs. 2, 5, and 6), 

the Black Warrior River aquifer receives recharge 

directly from precipitation where the aquifer is exposed 

at land surface or is overlain by permeable sand and 

gravel with no intervening unit of low permeability 

(Hinkle and others, 1983; Scott and others, 1987). 

STUDY DESIGN AND METHODS 

This study was designed by following national 

guidelines (Gilliom and others, 1995; Squillace and 

Price, 1996), and ground-water sampling protocols 

(Lapham and others, 1997; Koterba and others, 1995) 

for NAWQA. Standardization of data-collection 

System Stratigraphic unit Major

lithology

Thickness

(feet)

Hydrogeologic

unit

Regional

aquifer

system

Quaternary Alluvial and 

 terrace deposits

Sand, gravel,

silt, and clay

 5 – 100 + Shallow

aquifer

Cretaceous

 Selma Chalk Chalk 0 – 200 + Confining unit

 Southeastern Coastal Plain Aquifer System

 

 Eutaw 

 Formation

Upper and lower

marine sand separated

by clay; consists of

glauconitic sand 

interbedded with 

calcareous sandstone 

and sandy limestone

 0 – 100 +

 Tuscaloosa Group Black Warrior River aquifer

 

 Gordo 

 Formation

Basal zone of gravel and

sand overlain by 

lenticular beds of sand

and clay

 0 – 200 +

 

 Coker 

 Formation

Basal zone of 

non-marine sand, gravel,

and clay;

upper zone of marine

sand and clay

 500 +

 

 Pre-Cretaceous

Schist, gneiss 1,000 + Base of freshwater flow 

system
10 Comparison Between Agricultural and Urban Ground-Water Quality in the Mobile River Basin, 1999 – 2001

Figure 6. Diagram showing generalized hydrogeologic sections A-A’ and B-B’ in the agricultural and urban study areas of the 

Mobile River Basin (from fig. 7).
Study Design and Methods 11

procedures is intended to produce a nationally 

consistent data base that can be used to produce 

statistically valid interpretations. Modification of 

national protocols is sometimes necessary, however, 

because of local conditions. The following sections 

describe how these national protocols were applied 

and, when necessary, modified for this study.

Land Use and Land Cover

The criteria used to select well locations in the 

agricultural area (fig. 7) are outlined in Gilliom and 

others (1995). The two primary considerations for the 

placement of the agricultural wells were that (1) ground 

water sampled from the wells should be recently 

recharged (generally less than 10 years old), and 

(2) row cropping be the predominant land use in the 

vicinity of sampled wells (table 3). This enabled direct 

assessment of relations between land-use activity and 

ground-water quality (Gilliom and others, 1995). 

Where row cropping was not the predominant land use 

surrounding the well, the well was located 

downgradient from a row cropping area. 

Well locations for the urban area (fig. 7) were 

selected based on the criteria outlined in Squillace and 

Price (1996). Of primary concern were the criteria 

specifying that (1) the shallow aquifer in the study area 

be used as a source of drinking water, a potential source 

of drinking water, or hydraulically connected to surface 

water or deeper ground water that is used as a source of 

drinking water, and (2) land use within the study area 

be residential and commercial developed between 1970 

and the 1990’s. The urban study area in eastern 

Montgomery met these criteria; however, the last 

criterion was modified to extend the period of 

residential development in the study area from 1960 to 

1998.

Monitoring Well Network

 The wells used for this study were designed to 

sample shallow ground water. Of the 30 agricultural 

wells, 29 were installed by the USGS in accordance 

with NAWQA protocols (Lapham and others, 1995, 

1997; Koterba, 1998). One existing well (LUSCR1-15) 

that met NAWQA well-design protocols also was 

sampled. One well (LUSCR1-8) could not be sampled 

during the study because it remained dry (table 3; 

fig. 7). A reference well (LUSCR1-21) was installed in 

the flood plain of the Alabama River (fig. 7) at 

approximately the same depth as the wells located in 

the agricultural and urban areas. The reference well 

was located in a predominately forested area to obtain 

a sample of ground water that is relatively unaffected 

by man. 

The agricultural wells were completed in the 

alluvial deposits (19 wells), the terrace deposits 

(7 wells), and the Eutaw Formation (4 wells). The 

urban wells were completed in the alluvial deposits 

(8 wells), terrace deposits (6 wells), and the Eutaw 

Formation (16 wells). Detailed information about the 

urban wells used to sample water beneath the 

Montgomery, Alabama, area is documented in 

Robinson (2002). 

Water flows into a well through the well screens. 

In general, the less the depth to the well screen, the 

greater the susceptibility of the well to contamination 

from sources at land surface. The depth to the well 

screens of the agricultural wells ranged from about 

11 to 46 ft, with a median depth of 22.5 ft. The depth to 

the well screens of the urban wells was slightly greater, 

ranging from about 8 to 88 ft, with a median depth of 

29 ft.

A variety of physical and hydraulic data were 

collected during the installation of the agricultural and 

urban wells. Representative samples of the alluvial and 

terrace deposits and the Eutaw Formation were 

collected during installation of the agricultural and 

urban wells. Lithologic descriptions of the sediments 

were prepared. Sediment cores were collected from 

each lithologic unit. Representative samples of each 

lithology were chilled and sent to the USGS National 

Water Quality Laboratory (NWQL) in Denver, 

Colorado, for organic carbon analyses. A slug test was 

performed in well LUSCR1-6, which is located about 

1,100 ft south of the Tallapoosa River near Milstead, 

Alabama (figs. 6 and 7). The results of the slug test 

were used to estimate the hydraulic conductivity of the 

alluvial deposits in which the well is completed.

Water-Quality Samples

Ground-water samples were analyzed for 

physical properties, major ions, nutrients, pesticides, 

chlorofluorocarbons (CFCs), sulfur hexafluoride 

(SF6), and dissolved gases. The laboratory analytical 

methods used are listed in table 4. Sampling procedures 

and field methods were consistent with NAWQA 

ground-water sampling protocols (Koterba and others, 

1995) and standard USGS procedures. Ground-water 
12 Comparison Between Agricultural and Urban Ground-Water Quality in the Mobile River Basin, 1999 – 2001

Figure 7. Locations of agricultural and urban wells sampled in the Mobile River Basin, and lines of sections A-A’ and B-B’.

1 2 3 MILES

0 1 2 3 KILOMETERS

0

331

231

152

65

1

2

3

4 5

7 6

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

31 30

1

ALLUVIAL-DELTAIC PLAIN DISTRICT AGRICULTURAL STUDY WELL AND NUMBER REFERENCE WELL URBAN STUDY WELLS

EXPLANATION

TUSCALOOSA

TUSCALOOSA

Tuscaloosa

Tallapoosa 

River

Coosa River

B'

B

LOWNDES

MONTGOMERY

ELMORE

ELMORE

MACON

Montgomery

Alabama 

River

MACON

86 ̊18'

32 ̊24'

86 ̊14' 

32 ̊22'

32 ̊20'

Vaughn

McGehee 

Rd.

Eastern

Blvd.
Study Design and Methods 13

Table 3. Predominant crop and land-use types within a 0.3-mile radius of the agricultural wells in the 

Mobile River Basin

Well 

(fig. 7)

Cotton, 

in percent

Corn, 

in percent

Other 

cropsa

in percent

a

 Soybeans, sorghum, or wheat. 

Pasture, 

in percent

Fallow 

fields,

in percent

Otherb, 

in percent

b Open water, forested, roads, drainages, utility rights-of-way, housing, mining.

LUSCR1-1 93.5 6.5

LUSCR1-2 86.5 13.5

LUSCR1-3 37.5 62.5

LUSCR1-4 39 3.8 57.2

LUSCR1-5 10 25.2 64.8

LUSCR1-6 25.3 12.6 11.2 50.9

LUSCR1-7 6.5 26 4.3 63.2

LUSCR1-8c

c

 Dry well, not sampled for this study.

4.6 13.3 14.7 67.4

LUSCR1-9 30.8 69.2

LUSCR1-10 91.5 8.5

LUSCR1-11 37.1 26.6 24.8 11.5

LUSCR1-12 66.4 33.6

LUSCR1-13 49.1 20.1 3.9 26.9

LUSCR1-14 71.9 28.1

LUSCR1-15 34.1 65.9

LUSCR1-16 20.4 79.6

LUSCR1-17 19.1 22.4 5.4 53.1

LUSCR1-18 90.3 9.7

LUSCR1-19 43.8 56.2

LUSCR1-20 12.4 87.6

LUSCR1-21d

d Reference well.

100

LUSCR1-22 40.1 59.9

LUSCR1-23 59.5 3.1 10 27.4

LUSCR1-24 47.9 12 27.5 12.6

LUSCR1-25 24.5 6.1 69.4

LUSCR1-26 45.7 54.3

LUSCR1-27 80.1 19.9

LUSCR1-28 69.4 30.6

LUSCR1-29 51.2 48.8

LUSCR1-30 57.2 3.9 38.9

LUSCR1-31 41.7 58.3
14 Comparison Between Agricultural and Urban Ground-Water Quality in the Mobile River Basin, 1999 – 2001

samples analyzed for CFCs, SF6, and dissolved gases 

were hand delivered to the CFC laboratory in Reston, 

Virginia. All other ground-water samples were chilled 

and shipped overnight to the NWQL in Denver, 

Colorado.

Physical properties of water samples that are 

commonly measured in the field include pH, specific 

conductance, alkalinity, and dissolved oxygen. These 

measurements are made on site, because values or 

concentrations may change once the water is removed 

from the source. For comparison of sample stability, 

these measurements were made at the time of 

sampling, and again by the NWQL. The difference 

between the two measurements for each property 

ranged from less than 1 to 10 percent, but was typically 

less than 5 percent. Measurements for physical 

properties made at the NWQL are listed in table 7.

Ground water collected from the agricultural and 

urban wells was analyzed for 109 different pesticides 

and pesticide degradation products. These compounds 

are grouped into two NWQL schedules—2001 and 

2060—for testing by a specific set of preparation 

techniques, equipment, and analytical procedures. The 

urban ground water was analyzed for the compounds 

listed on NWQL schedule 2060 (Appendix table 1 and 

2); but these data were not published in Robinson 

(2002) because the 2060 analytical method, then 

classified as NWQL Lab Code 9060, was an 

experimental method prior to August 2001, and results 

of analyses were considered to be conditional. 

The NWQL reports analyte concentrations as 

measured, estimated (censored), or less than a 

reporting value. These terms indicate the confidence 

the laboratory places in the accuracy of the 

measurement and are based on the long-term accuracy 

of the methods used. The method detection level 

(MDL) is the minimum concentration of a substance 

that can be measured and reported with 99-percent 

confidence that the analyte concentration is greater 

than zero. The long-term method detection level 

(LTMDL) is derived by determining the MDL for a 

minimum of 24 MDL spike-sample measurements over 

an extended period of time. The laboratory reporting 

level (LRL) generally is equal to twice the yearly 

determined LTMDL. 

Measured values are reported for concentrations 

above the LRL and within the calibration range of the 

apparatus. Estimated values are reported for 

concentrations less than the LRL but above the 

LTMDL (Childress and others, 1999) or for 

concentrations greater than the calibrated range of the 

apparatus. The value of the LRL is reported with a "less 

than" remark code for samples in which the analyte was 

not detected.

Table 4. Constituents analyzed and analytical methods used for agricultural ground-water samples 

collected in the Mobile River Basin 

[UV, ultraviolet; C-18, octadecyl; CFC, chlorofluorocarbons; ECD, electron capture detector; SF6, sulfur hexafluoride]

Constituent Number of 

samples Analysis method Reference

Major ions 28a

a

 One sample was filtered to remove flocculants that formed after sampling; no dissolved ion data are available 

for this sample.

Atomic absorption 

spectrometric

Fishman (1993)

Nutrients 29 Various methods Fishman (1993)

Organic carbon 29 UV-promoted persulfate 

oxidation and infrared 

spectrometry

Brenton and Arnett (1993)

Pesticides 29 Solid-phase extraction using a 

C-18 cartridge and gas 

chromatography/mass 

spectrometry

Zaugg and others (1995) 

Furlong and others (2001)

CFC 8 Gas chromatography with 

ECD detector

Busenberg and Plummer 

(1992)

SF6 8 Gas chromatography with 

ECD detector

Busenberg and Plummer 

(2000)
Study Design and Methods 15

The laboratory reporting levels of the analytical 

methods used by the NWQL vary with time. 

Comparison of detection frequencies among sample 

sets can be misleading because of the different LRLs. 

Pesticide data are sometimes adjusted by censoring to a 

common threshold (values less than the threshold are 

not considered detections) to reduce this type of bias. 

Pesticide data for the agricultural and urban areas were 

censored to a common threshold for this report so that 

detection frequencies between the two study areas 

could be compared.

Quality-Assurance and Quality-Control 

Procedures

Quality-assurance (QA) procedures developed 

for NAWQA investigations were followed for this 

study. Well selection and well installation procedures 

were based on the standards documented by Lapham 

and others (1995, 1997). Description and classification 

of land use in the vicinity of the agricultural wells 

followed the procedures of Koterba (1998). Waterquality samples were collected and documented using 

the protocols and procedures of Koterba and others 

(1995).

Three types of quality-control (QC) samples 

were collected during the study—blanks, spikes, and 

replicates (table 5). A blank sample is a water sample 

that contains no analytes of interest. A blank sample is 

analyzed to determine if contamination has occurred 

during (1) sample collection and processing, (2) sample 

handling and transportation, and (or) (3) sample 

analysis (Mueller and others, 1997). Spiked samples are 

injected with a known mass of an analyte of interest for 

use in determining (1) the accuracy and precision of 

organic analyses, (2) the stability of analytes during 

typical holding times, and (3) whether characteristics of 

the environmental sample may interfere with the 

analysis for analytes (Mueller and others, 1997). 

Replicates are two or more samples that are either split, 

collected in sequence, or collected concurrently; 

replicates are considered to have identical composition. 

Replicates provide a measure of the variability resulting 

from sample collection, processing, and analysis 

(Mueller and others, 1997). Analyses of blanks, spikes, 

and replicates are evaluated to detect systematic bias in 

sample analyses results. 

The QC samples collected during sampling of the 

agricultural wells included four inorganic and organic 

blank samples, three pesticide spikes and three 

pesticide spike-replicates, four inorganic and organic 

replicates, and six pesticide replicate samples. 

Robinson (2002) summarized QC sample collection 

during sampling of the urban wells. Interpretation of the 

data provided by the blank samples collected during the 

agricultural land-use study indicated no systematic bias 

or source of contamination attributable to the sampling 

equipment or procedures used to collect the groundwater samples. Evaluation of the results of pesticide 

spike and environmental sample replicates, however, 

indicated a problem with NWQL pesticide schedule 

2060. Mean recovery of pesticides from the spike and 

spike-replicate samples ranged from 58 to 83 percent 

(table 6). The mean difference in recovery between the 

spike and the spike-replicate samples ranged from 12.7 

to 49 percent. The mean difference between 

concentrations of analytes for replicate samples ranged 

from 0 to 10.2 percent (table 6). 

The small mean-recovery percentage for NWQL 

schedule 2060 pesticide-spiked samples (table 6) 

indicates that the analytical method for schedule 2060 

underestimated the concentration of pesticides in the 

spiked samples. The large mean difference in recovery 

percentages for the schedule 2060 spike and spikereplicate samples indicates that the analytical method 

for schedule 2060 had poor accuracy. The large mean 

difference in analyte concentration for the schedule 

2060 environmental replicate samples indicates poor 

precision. More information pertaining to NWQL 

schedules 2001 and 2060 is presented in appendix A. 

None of the environmental data were adjusted based on 

interpretation of the results of the QC samples; for the 

purposes of this report, the results of the schedule 2060 

pesticide analyses are considered to be conservative.

Table 5. Summary of quality-control samples collected during 

sampling of the agricultural wells in the Mobile River Basin

Quality-control 

sample type

Analytical 

coverage

Number of 

samples

Blank Inorganic compounds 4

Blank Organic compounds 4

Spike Pesticides 3

Spike-replicate Pesticides 3

Replicate Inorganic compounds

Organic compounds

Pesticides

 4

 4

 6
16 Comparison Between Agricultural and Urban Ground-Water Quality in the Mobile River Basin, 1999 – 2001

Table 6. Descriptive statistics for quality-control samples collected for pesticide 

analysis during sampling of the agricultural wells in the Mobile River Basin 

[NWQL, National Water Quality Laboratory]

Sample type Date 

sampled

Mean 

recovery 

(percent)

Mean difference 

in recovery 

(percent)

Mean 

difference in 

concentration 

(percent)

NWQL Schedule 2001 

spike 07/19/2001 82

spike-replicate 07/19/2001 93 3.9

spike 09/10/2001 107

spike-replicate 09/10/2001 116 2.4

spike 09/20/2001 89

spike-replicate 09/20/2001 90 0.7

NWQL Schedule 2060

spike 07/19/2001 83

spike-replicate 07/19/2001 58 49.0

spike 09/10/2001 79

spike-replicate 09/10/2001 70 23.4

spike 09/20/2001 83

spike-replicate 09/20/2001 79 12.7

NWQL Schedule 2001

environmental 06/25/2001 0.1

replicate sample 06/25/2001

environmental 07/19/2001 0.5

replicate sample 07/19/2001

environmental 07/24/2001 3.7

replicate sample 07/24/2001

environmental 08/08/2001 0.0

replicate sample 08/08/2001

environmental 09/20/2001 0.0

replicate sample 09/20/2001

NWQL Schedule 2060 

environmental 07/19/2001 5.3

replicate sample 07/19/2001

environmental 07/24/2001 10.2

replicate sample 07/24/2001

environmental 08/08/2001 0.5

replicate sample 08/08/2001

environmental 09/10/2001 0.3

replicate sample 09/10/2001

environmental 09/20/2001 0.0

replicate sample 09/20/2001
Chemical and Physical Properties of the Shallow Sediments 17

Graphical and Statistical Methods

Two common graphical techniques were used to 

present and analyze the results of water-quality 

sampling—the Piper (1944) trilinear diagram and 

boxplots (Tukey, 1977). A Piper diagram plots the ionic 

content of many samples on a single graph. The 

dominant ion type in each sample is easily determined 

by where the sample plots on the diagram. However, 

because ion concentrations are converted to total 

composition percentages before plotting, water 

samples with very different total concentrations may 

plot closely together. Alley (1993) lists three ways 

boxplots illustrate the distribution of data: (1) the 

sample median, which is a robust measure of the 

central tendency of the data and is not influenced by 

outliers; (2) the difference between the top and bottom 

of the rectangle, the interquartile range, which is a 

robust measure of the spread of the data; and (3) the 

distance from the top of the rectangle to the median 

compared to the distance from the bottom of the 

rectangle to the median, which is a measure of the 

skewness of the data. Boxplots are useful in presenting 

data for individual constituents in large numbers of 

samples. Different groups of data can be compared and 

contrasted by placing boxplot analyses side by side.

 Descriptive statistics, such as the range, 

maximum, minimum, and median, were used to 

summarize the distribution of chemical data for 

ground-water sample sets. Chemical constituents with 

large differences in median values in the two data sets 

were further evaluated using nonparametric hypothesis 

testing. Nonparametric statistical methods were chosen 

because environmental data typically are non-normally 

distributed, and significant percentages of the data are 

less than laboratory reporting levels.

Nonparametric hypothesis tests represent 

censored data by ranking the data; estimation of data 

values below reporting levels is not necessary. The 

Wilcoxon rank-sum test was used to test the null 

hypothesis that independent, random ground-water 

samples from two populations were identical. 

Rejection of the null hypothesis, at a confidence level 

of 95 percent, supported the alternative hypothesis that 

the samples were drawn from different populations.

 Correlation analysis was used to examine the 

relations between selected physical properties and 

chemical constituents in ground water collected from 

the agricultural wells and the land use surrounding the 

wells. Correlation analysis is a means to assess not only 

the relation between two variables, but also the strength 

of the relation (Ott, 1988, p. 319). The Spearman rho 

rank correlation test was used to evaluate the 

correlation between water quality and land use since 

the number of samples was greater than 20 (Helsel and 

Hirsch, 1992, p. 217–218). The Kendall tau rank 

correlation test was used to evaluate the correlation 

among ground-water age, water quality, and land use 

since the number of samples was less than 10 (Helsel 

and Hirsch, 1992, p. 212). Scatterplots of all correlated 

variables were made to ensure that the variables 

possessed a monotonic correlation (Helsel and Hirsh, 

1992, p. 209–211).

CHEMICAL AND PHYSICAL PROPERTIES OF THE 

SHALLOW SEDIMENTS

The chemical and physical properties of 

sediments through which ground water flows can affect 

ground-water quality. Soils with low organic carbon 

content may increase the potential for nitrate (U.S. 

Geological Survey, 1999b) and pesticides (Barbash and 

Resek, 1996) to enter ground water. Soils with low pH 

contribute to low pH conditions in ground water, which 

has been correlated with increased nitrate and trace 

element concentrations (van Duijvenbooden, 1993). 

Coarse-grained sediments permit more rapid 

infiltration of water than fine-grained sediments; as a 

result, aquifers overlain by coarse-grained sediments 

may be more vulnerable to surface contamination than 

aquifers overlain by fine-grained sediments. The 

chemical and physical properties of the shallow 

sediments that agricultural and urban wells are 

completed in were determined by field and laboratory 

testing.

Soil Characteristics

The study area is underlain by soils developed 

from the alluvial and terrace deposits, the Eutaw 

Formation, and the Selma Chalk. Sandy, silty loam 

developed from the alluvial and terrace deposits and the 

Eutaw Formation have soil pH values ranging from 3.6 

to 6.5, and an organic carbon content ranging from 0 to 

4 percent (Hearn, 1944, 1955; Hajek and others, 1975; 

Harris and Stubbs, 1977). Clayey loam developed from 

the Selma Chalk is very poorly drained, has soil pH 

values ranging from 4.5 to 8.5, and organic carbon 

content ranging from 0 to 7 percent (Burgess and 

others, 1960). The relatively high organic carbon 

content and more moderate pH of soils developed from 
18 Comparison Between Agricultural and Urban Ground-Water Quality in the Mobile River Basin, 1999 – 2001

the chalk may reduce the potential for pesticides, 

nitrate, and trace elements to enter the ground water. 

The lower soil pH and organic carbon content of soils 

developed from the alluvial and terrace deposits may 

increase the potential for pesticides, nitrate, and trace 

elements to enter the ground water.

Sediment Core Analyses

 Sediment cores collected from the alluvial and 

terrace deposits and the Eutaw Formation had soil pH 

values ranging from 4.2 to 6.7, with a median value of 

4.8. Organic carbon content ranged from less than 

0.02 to 0.33 percent with a median value of 

0.03 percent. The low pH and low organic carbon 

content of the aquifer materials may increase the 

mobility of trace elements, nitrates, and pesticides in 

the ground-water system.

Lithology of the Shallow Sediments

Samples of the alluvial deposits typically were 

composed of very fine- to very coarse-grained quartz 

sand that was clear, white, red, and yellow in color. 

Pebbles were present in some samples, and muscovite 

was common. Red, brown, and gray silt and clay were 

mixed with the sand, and also were present as separate 

layers. The lithology of the terrace deposit samples was 

similar to the alluvial deposits, but quartz gravel up to 

100 millimeters in diameter also was present. Samples 

of the Eutaw Formation were composed of very fine- to 

medium-grained quartz sand, glauconite, calcium 

carbonate, and trace amounts of muscovite and pyrite. 

Gravel was not found in any of the Eutaw Formation 

samples. 

Shallow Aquifer Properties

A slug test was performed in well LUSCR1-6, 

which is located about 1,100 ft south of the Tallapoosa 

River near Milstead, Alabama (figs. 6 and 7). The well 

is completed in alluvial sediments composed of very 

coarse-grained sand and gravel. These sediments form 

a shallow aquifer that overlies and recharges the Black 

Warrior River aquifer. The results of the test indicate a 

hydraulic conductivity of 90 feet per day (ft/d) for the 

material directly surrounding the well. Despite the 

great permeability indicated by the slug test, it is 

possible that water does not move quickly over long 

distances through the shallow aquifer. Sand and gravel 

deposits in flood plains occur as lenses of limited 

geographic extent and may not be physically connected 

to the surface-water drainage. Silts and clays of low 

permeability also are deposited in flood plains and may 

separate sand and gravel deposits from the surfacewater drainage. In such a system, the primary direction 

of ground-water flow is horizontal through the aquifer 

material, and almost vertically downward through the 

silts and clays (Freeze and Cherry, 1979).

GROUND-WATER QUALITY

 Agricultural ground-water quality was 

determined using samples collected from 29 wells. All 

of the wells in the agricultural area either produce water 

from the shallow aquifer that overlies and recharges the 

uppermost unit of the Black Warrior River aquifer or 

from the Black Warrior River aquifer. Ground water 

was collected from 29 agricultural wells and the 

reference well during June through December 2001. 

The ground water was analyzed at the NWQL for 

physical properties, major ions, nutrients (table 7), and 

pesticides. Agricultural ground-water quality was 

compared to the water quality of urban ground water 

collected in Montgomery, Alabama, during 

1999–2000 (Robinson, 2002). Because the ground 

water collected from the agricultural and urban wells 

was taken from the same geologic units and 

physiographic setting, and at about the same depth, it is 

valid to compare and contrast the water quality of the 

two sample sets. Statistically significant differences in 

ground-water quality beneath the two land-use areas 

can reasonably be attributed to the effects of land use. 

Physical Properties

Ground water collected from the agricultural 

wells typically had acidic pH values, low specific 

conductance and alkalinity values, and contained few 

dissolved solids. Comparison of the agricultural and 

urban ground-water quality indicates that agricultural 

ground water had approximately equal or slightly 

greater median values for physical properties but a 

smaller range of values for alkalinity, pH, total 

dissolved solids, and specific conductance compared to 

urban ground water (fig. 8). The Wilcoxon rank-sum 

test indicated no statistically significant difference in 

physical properties between urban and agricultural 

ground water. The values measured were consistent 
Ground-Water Quality 19

Table 7. Minimum, median, and maximum values of selected physical properties and chemical constituents in ground water 

collected from agricultural and urban wells in the Mobile River Basin 

[Min, minimum; Med, median; Max, maximum; μS/cm at 25 °C, microseimen per centimeter at 25 degrees Celsius; mg/L, milligram per liter; 

C, carbon; N, nitrogen; P, phosphorus; *, value is estimated by using a log-probability regression to predict the values of data below the method detection level 

(Maddy and others, 1990); none, no drinking-water standard; μg/L, microgram per liter; —, too few detections to estimate statistics; <, less than; 

E, concentration less than the reporting level but above the long-term method detection level]

Property or constituent

Drinkingwater 

guideline

Reference 

well 

average 

value 

(2 samples)

Values for agricultural wells 

(29 samples) 

Values for urban wells 

(30 samples) 

Min Med Max Min Med Max

Physical propertiesa

a

 Twenty-eight agricultural samples were analyzed for physical properties and major ions. One sample was filtered to remove flocculants that formed 

after sampling. No physical properties or major ion data are available for this sample.

pH (standard units) 6.5–8.5b

b

 Secondary drinking-water standard, established by the U.S. Environmental Protection Agency.

 5.3 4.7 5.6 6.9 4.6 5.6 7.7

Specific conductance (μS/cm at 

25 °C)

none 22 30 107 330 28 74 2,670

Alkalinity (mg/L) none 4 <1 10 107 2 8 380

Dissolved solids residue 180 °C 

(mg/L)

500b 29 18 75 197 27 48 2,240

Dissolved oxygen (mg/L) none 5 .1 2 7 .1 4 7

Major ionsa

Calcium (mg/L) none 1 0.2 5.8 33 1.2 3.4 520

Magnesium (mg/L) none .2 .4 3 10 .3 1.4 9

Potassium (mg/L) none .1 .3 1.3 3 .2 1.4 2.8

Sodium (mg/L) none 1.8 1.4 5.9 29 .9 4.6 228

Bromide (mg/L) none .02 < .01 .06 .36 < .01 *.03 1

Chloride (mg/L) 250b 2.1 2.1 8.1 68 1.3 6.8 120

Fluoride (mg/L) 2b < .1 < .2 — < .2 < .1 *.09 .9

Silica (mg/L) none 15 8.3 18 33 8.2 14 42

Sulfate (mg/L) 250b .7 .1 1.5 20 < .1 *.6 1,100

Iron (μg/L) 300b <10 <10 — 10,200 <10 16 2,500

Manganese (μg/L) 50b 4.6 1.8 59 7,200 10 80 382

Nutrients

Ammonia (mg/L) as N none < 0.04 < 0.04 — 3.1 < 0.02 *0.005 0.14

Ammonia plus organic (mg/L) 

as N

none < .1 < .1 — 3.5 < .1 *.07 .15

Nitrite plus nitrate (mg/L) as N 10c

c

 Maximum contaminant level for drinking water, established by the U.S. Environmental Protection Agency.

 .30 < .05 3 17.6 < .05 *1.3 15

Phosphorus (mg/L) as P none < .006 < .006 — .3 < .006 *.005 .2

Phosphorus, ortho (mg/L) as P none < .02 < .02 — .2 < .01 *.002 .2

Dissolved organic carbon (mg/L) 

as C

none E .2 < .33 .2 6 < .33 *.28 1.2
20 Comparison Between Agricultural and Urban Ground-Water Quality in the Mobile River Basin, 1999 – 2001

Figure 8. Concentrations of selected water-quality constituents in ground water collected from agricultural and 

urban wells in the Mobile River Basin.

with shallow ground water that has been recently 

recharged (Robinson, 2002).

Major Ions

Ground water collected from the agricultural 

wells typically had small concentrations of major ions, 

but a few samples had large concentrations of iron and 

manganese. The major ion composition of ground 

water collected from the reference well and the 

agricultural wells is illustrated in a Piper diagram 

(fig. 9). 

The major ion content of water collected from 

the reference well plots near the lower right center of 

the cation and anion triangles, indicating water slightly 

more influenced by sodium, potassium, chloride, and 

nitrite-plus-nitrate ions (table 7; fig. 9). The major ion 

content of ground water from the agricultural wells 

plots near the center of the cation triangle, indicating no 

dominant cation; however, the major ion content is 

clustered near the lower right corner of the anion 

triangle, indicating water quality dominated by 

chloride and nitrite plus nitrate. A subset of six groundwater samples plot near the lower left corner of the 

anion triangle, indicating water quality dominated by 

carbonate and bicarbonate anions. Four of these 

samples were collected from wells completed in the 

Eutaw Formation, and two of the samples were 

collected from wells completed in the alluvial deposits. 

The distinct separation of the agricultural wells from 

the reference well on the Piper plot indicates either a 

different source for the water (alluvial and terrace 

deposits compared to the Eutaw Formation) or a 

change in water quality, possibly as a result of different 

land uses, or both. 

Comparison of agricultural and urban groundwater quality indicated that ground water collected 

from agricultural wells had approximately equal or 

slightly greater median values for major ions, but 

typically had a smaller range of values compared to 
Ground-Water Quality 21

Figure 10. Concentrations of magnesium in ground water 

collected from agricultural and urban wells in the Mobile River 

Basin.

Figure 9. Piper trilinear diagram showing major ion composition of ground water collected from 

agricultural wells and the reference well.

ground water collected from the urban wells (table 7). 

The exceptions were the ranges in concentrations of 

iron, manganese, and potassium, which were greater 

in the samples collected from the agricultural wells. 

The median concentration of magnesium was greater 

in ground water collected from the agricultural wells 

than in ground water collected from the urban wells 

(fig. 10). The Wilcoxon rank-sum test indicated that 

magnesium was the only major ion present at 

statistically different concentrations in the two data 

sets.

Nutrients and Dissolved Organic Carbon

Some of the ground-water samples collected 

from the agricultural wells contained greater 

concentrations of nutrients than typically found in 

ground water. Ammonia concentrations in ground 

water generally are less than 0.1 milligram per liter 

(mg/L; Mueller and Helsel, 1996); however, five 

agricultural ground-water samples contained 
22 Comparison Between Agricultural and Urban Ground-Water Quality in the Mobile River Basin, 1999 – 2001

ammonia concentrations ranging from 0.16 to 

3.5 mg/L. Total nitrate concentrations in ground water 

generally are less than 2 mg/L (Mueller and Helsel, 

1996); however, 19 agricultural ground-water samples 

contained nitrite-plus-nitrate concentrations ranging 

from 2.6 to 17.6 mg/L. Ground-water samples from 

two agricultural wells and one urban well contained 

nitrite-plus-nitrate concentrations that exceeded the 

U.S. Environmental Protection Agency’s drinkingwater maximum contaminant level of 10 mg/L. 

Phosphorus and orthophosphate concentrations 

generally are less than 0.1 and 0.02 mg/L, respectively 

(Mueller and Helsel, 1996), but six agricultural groundwater samples contained phosphorus or 

orthophosphate concentrations greater than these 

values. Most ground water contains dissolved organic 

carbon at concentrations less than 0.7 mg/L (James 

Kingsbury, U.S. Geological Survey, oral commun., 

2002), but three agricultural ground-water samples 

contained dissolved organic carbon concentrations 

ranging from 1.1 to 6 mg/L. 

Samples of ground water collected from the 

agricultural wells typically had a greater range of 

values and equal or slightly greater median values for 

nutrients than ground water collected from urban wells. 

The median value of nitrite plus nitrate (table 7; fig. 11) 

in the agricultural ground water was more than twice 

the median value in the urban ground water; however, 

the range of values was similar. The Wilcoxon ranksum test indicated no statistically significant difference 

in nutrient concentrations between the urban and 

agricultural ground water.

Pesticides

Ground water collected from the agricultural and 

urban wells was analyzed for 109 different pesticides 

and pesticide degradation products. Pesticides were 

detected in ground water collected from 25 of the 29 

agricultural wells. Nineteen different pesticide 

compounds were detected a total of 83 times. The most 

frequently detected compounds, in order, were 

fluometuron, deethylatrazine, norflurazon, atrazine, 

aldicarb sulfoxide, aldicarb sulfone, diuron, and 

metolachlor. Herbicides and their degradation products 

were the most frequently detected class of pesticides 

(table 8; fig. 12). The range and distribution of 

concentrations of selected pesticides are shown in 

figure 13; many of the concentrations are similar, 

however, and do not appear as individual points on the 

graph when plotted. The greatest concentration of any 

pesticide was an estimated value of 1.4 microgram per 

liter (μg/L) of fluometuron (fig. 13; table 8). 

Pesticide data for the agricultural and urban 

areas were censored to a common threshold so that 

detection frequencies between the two study areas 

could be compared (table 9). Pesticides were detected 

in a lesser percentage of the agricultural ground-water 

samples (14 of 29 wells) than in the urban groundwater samples (16 of 30 wells). Fewer total pesticides 

were detected in agricultural ground water than in 

urban ground water (26 and 44 detections, 

respectively), and fewer compounds were detected 

in agricultural ground water than in urban ground 

water (12 and 14 compounds, respectively). Atrazine 

was the only compound detected frequently enough 

in both agricultural and urban ground water to allow 

statistical testing. Results of the Wilcoxon rank-sum 

test indicated no statistically significant difference in 

atrazine concentrations in ground water collected 

from the agricultural and urban wells.

Age of Ground Water

Ground water collected from eight 

agricultural wells was analyzed for the 

environmental tracers CFCs and SF6. Ground-water 

age is estimated by relating the measured 

concentration of the environmental tracer in the 

Figure 11. Concentrations of nitrite plus nitrate in ground water collected ground water to the reconstructed historical 

from agricultural and urban wells in the Mobile River Basin.
Ground-Water Quality 23

Figure 12. Detection frequencies of selected pesticides in ground water collected from 

agricultural wells in the Mobile River Basin.

Table 8. Maximum concentrations of selected pesticides in ground water collected from agricultural wells in 

the Mobile River Basin 

[μg/L, microgram per liter; H, herbicide; I, insecticide; E, concentration less than the laboratory reporting level but greater 

than the long-term method detection level]

Pesticide Type Drinking-water

guidelines

Agricultural wells

(29 samples)

Frequency

of

detection

(percent)

Maximum

value

a Fluometuron (μg/L)

a

 Constituent analyzed using NWQL Schedule 2060 procedure; results of analyses may be conservative.

 H b90

b

 Human health guideline established by the U.S. Environmental Protection Agency, 2000.

58.6 E 1.4

Deethylatrazine (μg/L) H none 34.5 E .06

a Norflurazon (μg/L) H none 24.1 E .4

Atrazine (μg/L) H c3

c

 Maximum contaminant level for drinking water established by the U.S. Environmental Protection Agency, 2000.

 24.1 .15

a Aldicarb sulfoxide (μg/L) I d4

d Draft maximum contaminant level for drinking water established by the U.S. Environmental Protection Agency, 2000.

24.1 E .06

a Aldicarb sulfone (μg/L) I d4 17.2 E .14

a Deisopropyl atrazine (μg/L) H none 13.8 E .08

a Diuron (μg/L) H b10 13.8 .04

a Hydroxy atrazine (μg/L) H none 13.8 E .13

Metolachlor (μg/L) H b70 13.8 .16

a Deethyl deisopropyl atrazine (μg/L) H none 10.3 E .008
24 Comparison Between Agricultural and Urban Ground-Water Quality in the Mobile River Basin, 1999 – 2001

Figure 13. Range and distribution of concentrations of selected pesticides in ground 

water collected from agricultural wells in the Mobile River Basin.

Table 9. Detection frequencies of selected pesticides in ground water from agricultural and urban 

wells collected using common laboratory reporting levels 

[LRL, laboratory reporting level; μg/L, microgram per liter; H, herbicide; I, insecticide]

Pesticide Type

Agricultural wells Urban wells

 Common LRL 

(μg/L)

 Frequency of

detection

(percent)

Frequency of

detection

(percent)

a Fluometuron 

a

 Constituent analyzed using NWQL Lab Code 9060 or Schedule 2060 procedure; results of analyses may be 

conservative.

 H 20.7 3.3 0.0617

Atrazine H 17.2 20.0 .007

Deethylatrazine H 6.9 33.3 .006

a Aldicarb sulfoxide I 10.3 .0 .027

a Norflurazon H 6.9 .0 .0774

Metolachlor H 6.9 .0 .013

a Deisopropyl atrazine H 3.4 3.3 .0737

a Deethyl deisopropyl atrazine H .0 10.0 .0599
Relations Among Ground-Water Quality, Ground-Water Age, and Land Use 25

atmospheric concentration and(or) calculated 

concentrations expected in water in equilibrium with air 

(Busenberg and Plummer, 1992, 2000). The estimated 

age of the water refers to the date of the introduction of 

chemicals to the water, which is assumed to be from the 

atmosphere and prior to the water entering the aquifer. 

Environmental processes, such as microbial 

degradation, sorption, and excess dissolved gasses, may 

affect the concentration of environmental tracers in the 

water.

Chlorofluorocarbons (CFCs) are synthetic 

compounds first produced in the early 1930’s (Cook 

and Herczeg, 2000). The presence of measurable 

concentrations of CFCs in a water sample indicates that 

the sample contains some post-1940 water. Ground 

water collected from the agricultural land-use study 

wells was analyzed for CFC-11 (trichlorofluoromethane or CFCl3), CFC-12 (dichlorodifluoromethane 

or CF2Cl2), and CFC-113 (trichlorotrifluoroethane or 

C2F3Cl3). Sulfur hexafluoride (SF6) is a trace 

atmospheric gas that occurs naturally in some minerals, 

igneous rocks, and in volcanic and igneous fluids; 

however, SF6 is primarily of anthropogenic origin. 

Large-scale production of SF6 began in the 1960’s, and 

dating is possible from about 1970 (Busenberg and 

Plummer, 1997).

Ground water sampled from the agricultural 

wells ranged in age from about 14 to about 34 years, 

with a median age of about 18.5 years (table 10). The 

ages estimated for the ground water are consistent with 

the geology and hydrology of the study area and the 

design of the wells. The median age of the agricultural 

ground water is only slightly greater than the median 

age of the urban ground water collected from beneath 

eastern Montgomery, Alabama (table 10).

RELATIONS AMONG GROUND-WATER QUALITY, 

GROUND-WATER AGE, AND LAND USE

Results of applying the Spearman rho and 

Kendall tau correlation tests to determine statistically 

significant covariance among ground-water quality, 

ground-water age, and land use are provided in table 11. 

The tests are based on ranks. Concentrations of waterquality constituents less than the reporting level were 

assigned a value of one-half the smallest reported 

concentration to ensure that their rank was not equal to 

the rank of a measured value at or near the reporting 

level.

Some of the correlations listed in table 11 reflect 

the natural geochemical evolution of ground water as it 

ages. The pH, alkalinity, and concentration of iron in 

agricultural ground water increased as ground-water 

age increased. The concentration of dissolved oxygen 

and nitrite plus nitrate decreased as ground-water age 

increased. These correlations reflect common changes 

in ground-water quality that occur with time (Robinson, 

2002) and support the accuracy of the ground-water age 

estimates in the agricultural land-use area. 

A Piper diagram was constructed to illustrate the 

change in major ion composition of ground water as it 

ages (fig. 14). As ground-water age increases, the major 

ion composition moves away from magnesium-calcium 

and nitrite-plus-nitrate-dominated water quality to a 

more mixed composition. Water flowing through the 

subsurface and away from the original sources of 

magnesium and nitrite plus nitrate (land applications) 

dissolves minerals from the aquifer matrix and places 

ions from those minerals in solution. In addition, 

nitrates may be removed from solution by natural 

processes such as denitrification. These processes 

Table 10. Depths to well screens and ages of ground water collected from agricultural and urban wells in 

the Mobile River Basin 

[~, approximately; >, greater than]

Study area Depths to well screens, in feet a

Ground-water age, in years

a

 Age of ground water was determined for 30 urban samples and 8 agricultural samples.

Minimum Median Maximum Minimum Median Maximum

Agricultural (29 wells) 11 22.5 46 14 18.5 34

Urban (30 wells) 8 29 88 ~ 1 12 > 45
26 Comparison Between Agricultural and Urban Ground-Water Quality in the Mobile River Basin, 1999 – 2001

Figure 14. Piper trilinear diagram showing major ion composition and age of selected ground 

water collected from agricultural wells.

Table 11. Correlation coefficients for selected physical properties and constituents in ground water collected from 

agricultural wells in the Mobile River Basin

[<, less than]

Variables

Number of 

sample 

pairs

Correlation 

coefficient

Probability

statistic

a Ground-water age and pH

a

 Kendall tau rank correlation test.

8 0.71 0.01

a Ground-water age and alkalinity 8 .64 .026

a Ground-water age and concentration of dissolved oxygen 8 - .57 .048

a Ground-water age and concentration of nitrite plus nitrate 8 - .91 .002

a Ground-water age and concentration of iron 8 .88 .003

b Concentrations of dissolved oxygen and nitrite plus nitrate

b Spearman rho rank correlation test.

29 .81 < .001

b Concentrations of magnesium and nitrite plus nitrate 28 .58 .001

b Concentrations of nitrite plus nitrate and number of pesticides detected 29 .44 .018
Summary 27

change the composition of the water, and the resulting 

ionic composition plots closer to the center of the Piper 

diagram. A similar pattern was found for urban ground 

water (Robinson, 2002).

Some correlations listed in table 11 may reflect 

the influence of agricultural practices on ground-water 

quality. The concentration of nitrite plus nitrate in 

agricultural ground water increased as the 

concentration of magnesium and the number of 

pesticides detected increased. This correlation likely 

reflects the application of pesticides, nitrogen-based 

fertilizer, and crushed limestone and dolomite 

containing magnesium. 

Land use was associated with the distribution 

and occurrence of pesticides in ground water. The 

herbicides fluometuron, norflurazon, metolachlor, and 

diuron were found only in ground water collected from 

the agricultural area, except for one detection of 

fluometuron in an urban sample collected near a cotton 

field. Aldicarb, or its degradation products, was found 

only in the agricultural area. Dieldrin, simazine, and 

terbacil were detected only in urban ground water 

(Robinson, 2002). Atrazine and deethylatrazine were 

found in ground water beneath both agricultural and 

urban areas. 

No correlation was found between crop type and 

ground-water quality in the agricultural area. The lack 

of correlation may be due to agricultural practices, such 

as crop rotation and the cultivation of a variety of crops. 

The lack of correlation also could indicate that the 

recharge area of the ground water was not influenced 

by row cropping; however, ground water probably does 

not flow long distances from the recharge area because 

the shallow sediments occur as lenses of limited 

geographic extent.

SUMMARY

Ground-water quality in a shallow aquifer and 

the underlying Black Warrior River aquifer was 

evaluated beneath an agricultural area and compared to 

ground-water quality in the same aquifers beneath an 

urban area. The agricultural and urban areas are located 

in the flood plains of the Alabama, Black Warrior, 

Coosa, and Tallapoosa Rivers and their tributaries in 

central Alabama. Row cropping has been practiced in 

some of the fields where the agricultural wells were 

drilled for nearly 100 years. Major crops grown in these 

flood plains include cotton, corn, and beans. Crop 

rotation and no-till planting are practiced, and a variety 

of crops are grown on about one-third of the farms. The 

urban wells were drilled in a residential and 

commercial area of eastern Montgomery, Alabama, 

where development began about 1965 and continued in 

some areas through 1995.

All of the wells sampled either produce water 

from the shallow aquifer that overlies and recharges the 

Black Warrior River aquifer or from the uppermost unit 

of the Black Warrior River aquifer. Ground water was 

collected from 29 wells located in the agricultural area 

and from 30 wells located in the urban area. The wells 

were completed in the same geologic units and have 

approximately the same range and median values of 

depth; the age range of ground water collected from the 

wells was similar. Statistically significant differences 

in water quality between the two sample sets could 

reasonably be attributed to differences in land use. 

Ground-water samples were analyzed for physical 

properties, major ions, nutrients, pesticides, 

chlorofluorocarbons, sulfur hexafluoride, and 

dissolved gases.

There were no statistical differences in the 

median concentrations of most major ions and nutrients 

in ground water collected from beneath the agricultural 

and the urban areas. The median concentration of 

magnesium, however, was statistically greater in the 

agricultural ground water. The greater median 

concentration of magnesium in the agricultural ground 

water is attributed to applications of crushed limestone 

and dolomite, containing magnesium, that are used to 

moderate the pH of the acidic soils. Concentrations of 

ammonia, nitrite plus nitrate, phosphorus and 

orthophosphate, and dissolved organic carbon in 

ground water collected from many of the agricultural 

wells were greater than concentrations typically found 

in ground water, but not statistically greater than the 

concentrations measured in ground water collected 

from the urban wells.

Pesticides were detected in a lesser percentage of 

agricultural ground-water samples than in urban 

ground-water samples, and the total number of 

pesticide detections was greater in the urban ground 

water. The number of pesticide compounds detected in 

urban ground water also was greater than in 

agricultural ground water. The results of the Wilcoxon 

rank-sum test indicated no statistical difference in 

concentrations of atrazine between samples of 

agricultural and urban ground water.

The Spearman rho and Kendall tau tests were 

used to check for statistically significant covariance 
28 Comparison Between Agricultural and Urban Ground-Water Quality in the Mobile River Basin, 1999 – 2001

between agricultural ground-water quality, groundwater age, and land use. The pH, alkalinity, and 

concentration of iron in agricultural ground water 

increased as ground-water age increased. The 

concentration of nitrite plus nitrate decreased as 

ground-water age increased and as the concentration of 

dissolved oxygen decreased. These correlations 

possibly indicate the consumption of nitrogen-based 

compounds by natural processes such as 

denitrification. The concentration of nitrite plus nitrate 

increased as the concentration of magnesium and the 

numbers of pesticide detections increased. These 

correlations are attributed to land application of 

nitrogen-based fertilizer, crushed limestone and 

dolomite containing magnesium, and pesticides. No 

correlation was found between water quality and land 

use or crop type, probably as a result of agricultural 

practices, such as crop rotation and the cultivation of a 

variety of crops.

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Ground-water resources and geology of Tuscaloosa 

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County Report 6, 97 p.

Pearman, J.L., Stricklin, V.E., and Psinakis, W.L., 2000, 

Water resources data, Alabama, water year 1999: U.S. 

Geological Survey Water-Data Report AL-99-1, 604 p.

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2000: U.S. Geological Survey Water-Data Report 

AL-00-1, 712 p.

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2001: U.S. Geological Survey Water-Data Report 

AL-01-1, 669 p.

———2003, Water resources data, Alabama, water year 

2002: U.S. Geological Survey Water-Data Report 

AL-02-1, 511 p.

Piper, A.M., 1944, A graphical procedure in the geochemical 

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American Geophysical Union, v. 25, p. 914–923.

Renken, R.A., 1998, Ground water atlas of the United States, 

segment 5—Arkansas, Louisiana, and Mississippi: 

U.S. Geological Survey Hydrologic Investigations 

Atlas 730-F, 28 p.
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urban residential and commercial area, Montgomery, 

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Special Map 168, 1 sheet.

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Alabama, a reconnaissance report: Geological Survey 

of Alabama Information Series 21, 92 p.

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Alabama, a reconnaissance report: Geological Survey 

of Alabama Information Series 16, 97 p.

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Geohydrology and susceptibility of major aquifers to 

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Geological Survey Water-Resources Investigations 

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83 p.

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Appendix 31

APPENDIX

NWQL SCHEDULE 2060

The NWQL Lab Code 9060 was an experimental method until approved as the Schedule 2060 analytical 

method in August 2001. The urban ground water samples collected during 1999 and 2000 were analyzed for the 

compounds listed on NWQL Lab Code 9060; but these data were not published in Robinson (2002) because the 

results of analyses using experimental methods are considered to be conditional. During the time before March 1, 

2000, the holding times for some samples that were analyzed for the compounds listed in NWQL Lab Code 9060 

exceeded the median half-life of some of the compounds. The median half-life for each compound was determined 

based on an analyses of matrix spike samples held for known time periods (Furlong and others, 2001). The results 

of analyses of the urban ground water for the compounds listed in Lab Code 9060 are included in this report 

(Appendix table 2). However, due to the low mean-recovery percentage for spiked samples and the large variance 

between results of replicate samples for NWQL Schedule 2060 (table 4), in addition to excessive holding times for 

some samples collected before March 1, 2000; the analyses for compounds listed in NWQL Lab Code 9060 are 

considered to be conservative.
Compound CAS number

Minimum 

reporting 

level 

(μg/L)

2,4-D 94-75-7 0.021

2,4-D methyl ester 1928-38-7 0.0086 

2,4-DB 94-82-6 0.016 

2-Hydroxyatrazine 2163-68-0 0.008 

3(4-Chlorophenyl)-1-methyl 

urea

5352-88-5 0.024 

3-Hydroxycarbofuran 16655-82-6 0.0058 

3-Ketocarbofuran 6709-30-1 1.5 

Acifluorfen 50594-66-6 0.0066 

Aldicarb 116-06-3 0.04 

Aldicarb sulfone 1646-88-4 0.02 

Aldicarb sulfoxide 1646-87-3 0.0082 

Atrazine 1912-24-9 0.009 

Bendiocarb 22781-23-3 0.025 

Benomyl 17804-35-2 0.0038 

Bensulfuron-methyl 83055-99-6 0.015 

Bentazon 25057-89-0 0.011 

Bromacil 314-40-9 0.033

Bromoxynil 1689-84-5 0.017 

Caffeine 58-08-2 0.0096 

Carbaryl 63-25-2 0.028 

Carbofuran 1563-66-2 0.0056 

Chloramben, methyl ester 7286-84-2 0.018 

Chlorimuron-ethyl 90982-32-4 0.0096 

Chlorothalonil 1897-45-6 0.035 

Clopyralid 1702-17-6 0.013 

Cycloate 134-23-2 0.013 

Dacthal monoacid 887-54-7 0.011 

Deethyl atrazine 6190-65-4 0.028 

Deethyl deisopropyl atrazine 3397-62-4 0.01 

Deisopropylatrazine 1007-28-9 0.044 

Dicamba 1918-00-9 0.012 

Dichlorprop 120-36-5 0.013 

Dinoseb 88-85-7 0.012 

Diphenamid 957-51-7 0.026 

Diuron 330-54-1 0.015 

Fenuron 101-42-8 0.031 

Flumetsulam 98967-40-9 0.011 

Fluometuron 2164-17-2 0.031 

Imazaquin 81335-37-7 0.016

Imazethapyr 81335-77-5 0.017 

Imidacloprid 138261-41-3 0.0068 

Linuron 330-55-2 0.014 

Sampling Requirements

Description: 1 liter glass bottle, amber 

Treatment and preservation: Bottle baked at 450 

degrees Celsius by laboratory. DO NOT RINSE BOTTLE. Do not fill bottle beyond shoulder, as reagents 

must be added to the sample at the NWQL before analyses. Chill sample and maintain at 4 degrees Celsius; 

ship immediately. 

MCPA 94-74-6 0.016 

MCPB 94-81-5 0.015 

Metalaxyl 57837-19-1 0.02 

Methiocarb 2032-65-7 0.008 

Methomyl 16752-77-5 0.0044 

Methomyl-oxime 13749-94-5 0.011

Metsulfuron methyl 74223-64-6 0.025 

Neburon 555-37-3 0.012 

Nicosulfuron 111991-09-4 0.013 

Norflurazon 27314-13-2 0.016 

Oryzalin 19044-88-3 0.017 

Oxamyl 23135-22-0 0.012 

Oxamyl-oxime 30558-43-1 0.013

Picloram 1918-02-1 0.019 

Propham 122-42-9 0.0096 

Propiconazole 60207-90-1 0.021 

Propoxur 114-26-1 0.008 

Siduron 1982-49-6 0.016 

Sulfometuron-methyl 74222-97-2 0.0088 

Tebuthiuron 34014-18-1 0.0062 

Terbacil 5902-51-2 0.0098 

Tribenuron-methyl 101200-48-0 0.0088 

Triclopyr 55335-06-3 0.022 

Compound CAS number

Minimum 

reporting 

level 

(μg/L)

Appendix table 1. List of chemical compounds and analytical methods for National Water Quality Laboratory Schedule 2060 (Lab Code 9060 

prior to August 2001), high performance liquid chromatography/mass spectrometric - solid phase extraction 

[CAS, chemical abstract service; NWQL, National Water Quality Laboratory]

32 Comparison Between Agricultural and Urban Ground-Water Quality in the Mobile River Basin, 1999–2001
Appendix 33

Appendix table 2. Results of analyses of urban ground water for constituents of NWQL Lab Code 9060[μg/L, microgram per liter; <, less than; E, estimated value; M, presence verified but not quantified]

Well

2,4-D

 Methyl ester

 (μg/L)

2,4-D 

Dissolved

(μg/L)

2,4-DB

(μg/L)

3 Hydrxy 

carbofuran

(μg/L)

3-Keto 

carbofurab

(μg/L)

Acifluorfe

(μg/L)

Aldicarb 

sulfone

(μg/L)

Aldicarb 

sulfoxide

(μg/L)

Aldicar

(μg/L)

LUSCR1-1 <0.09 <0.08 <0.05 <0.06 <0.07 <0.06 <0.2 <0.03 <0.08 LUSRC1-2 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 LUSRC1-3 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 LUSRC1-4 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 LUSRC1-5 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 LUSRC1-6 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 LUSRC1-7 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.10 LUSRC1-8 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.10 LUSRC1-9 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 LUSRC1-10 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.10 LUSRC1-11 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 LUSRC1-12 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 LUSRC1-13 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 LUSRC1-14 E.01 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 LUSRC1-15 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 LUSRC1-16 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 LUSRC1-17 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 LUSRC1-18 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 LUSRC1-19 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 LUSRC1-20 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.10 LUSRC1-21 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 LUSRC1-22 E.01 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 LUSRC1-23 <.09 <.08 <.05 <.06 <.07 <.06 <.2 -- <.08 LUSRC1-24 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 LUSRC1-25 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 LUSRC1-26 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 LUSRC1-27 E.01 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 LUSRC1-28 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 LUSRC1-29 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 LUSRC1-30 <.09 <.08 <.05 <.06 <.07 <.06 <.2 <.03 <.08 
34 Comparison Between Agricultural and Urban Ground-Water Quality in the Mobile River Basin, 1999–2001 Appendix table 2. Results of analyses of urban ground water for constituents of NWQL Lab Code 9060—Continued

[μg/L, microgram per liter; <, less than; E, estimated value; M, presence verified but not quantified]

WELL Benomyl (μg/L) Bensulfuron methly (μg/L) Bentazon 

(μg/L)

Bromacil 

(μg/L)

Bromoxynil 

(μg/L)

Cafeine

 (μg/L)

Carbaryl

 (μg/L)

Carbofuran 

(μg/L)

Chloramb

methyl es

(μg/L)

LUSCR1-1 <0.02 <0.05 <0.02 <0.08 <0.06 <0.08 <0.06 <0.06 <0.1 LUSRC1-2 <.02 <.05 <.02 -- <.06 <.08 <.06 <.06 <.1 LUSRC1-3 <.02 <.05 <.02 E.02 <.06 <.08 <.06 <.06 <.1 LUSRC1-4 <.02 <.05 <.02 <.08 <.06 <.08 <.06 <.06 <.1 LUSRC1-5 <.02 <.05 <.02 <.08 <.06 <.08 <.06 <.06 <.1 LUSRC1-6 <.02 <.05 <.02 E.02 <.06 <.08 <.06 <.06 <.1 LUSRC1-7 <.02 <.05 <.02 <.08 <.06 <.08 <.06 <.06 <.1 LUSRC1-8 <.02 <.05 <.02 E.03 <.06 <.08 <.06 <.06 <.1 LUSRC1-9 <.02 <.05 <.02 E.11 <.06 <.08 <.06 <.06 <.1 LUSRC1-10 <.02 <.05 <.02 E.05 <.06 <.08 <.06 <.06 <.1 LUSRC1-11 <.02 <.05 <.02 <.08 <.06 <.08 <.06 <.06 <.1 LUSRC1-12 <.02 <.05 <.02 E.03 <.06 <.08 <.06 <.06 <.1 LUSRC1-13 <.02 <.05 E.01 E.02 <.06 <.08 <.06 <.06 <.1 LUSRC1-14 <.02 <.05 <.02 <.08 <.06 <.08 <.06 <.06 <.1 LUSRC1-15 <.02 <.05 <.02 <.08 <.06 <.08 <.06 <.06 <.1 LUSRC1-16 <.02 <.05 <.02 <.08 <.06 <.08 <.06 <.06 <.1 LUSRC1-17 <.02 <.05 <.02 <.08 <.06 <.08 <.06 <.06 <.1 LUSRC1-18 <.02 <.05 <.02 <.08 <.06 <.08 <.06 <.06 <.1 LUSRC1-19 <.02 <.05 <.02 <.08 <.06 <.08 <.06 <.06 <.1 LUSRC1-20 <.02 <.05 <.02 <.08 <.06 <.08 <.06 <.06 <.1 LUSRC1-21 <.02 <.05 <.02 <.08 <.06 <.08 <.06 <.06 <.1 LUSRC1-22 <.02 <.05 <.02 <.08 <.06 <.08 <.06 <.06 <.1 LUSRC1-23 <.02 <.05 <.02 <.08 <.06 <.08 <.06 <.06 <.1 LUSRC1-24 <.02 <.05 <.02 <.08 <.06 <.08 <.06 <.06 <.1 LUSRC1-25 <.02 <.05 <.02 <.08 <.06 <.08 <.06 <.06 <.1 LUSRC1-26 <.02 <.05 <.02 <.08 <.06 <.08 <.06 <.06 <.1 LUSRC1-27 <.02 <.05 <.02 <.08 <.06 <.08 <.06 <.06 <.1 LUSRC1-28 <.02 <.05 <.02 <.08 <.06 <.08 <.06 <.06 <.1 LUSRC1-29 <.02 <.05 <.02 <.08 <.06 <.08 <.06 <.06 <.1 LUSRC1-30 <.02 <.05 <.02 <.08 <.06 <.08 <.06 <.06 <.1 
Appendix 35

Appendix table 2. Results of analyses of urban ground water for constituents of NWQL Lab Code 9060—Continued[μg/L, microgram per liter; <, less than; E, estimated value; M, presence verified but not quantified]

WELL Clopyralid (μg/L) Cycloate (μg/L) Dacthal monoacid (μg/L) Deethyl atrazine (μg/L) Deethyl deisopropyl atrazine (μg/L) Deisopropyl atrazine (μg/L) Dicamba (μg/L) Dichlor prop (μg/L) Dinose

 (μg/L

LUSCR1-1 <0.04 <0.05 <0.07 E0.112 E0.06 E0.02 <0.10 <0.05 <0.04 LUSRC1-2 <.04 -- <.07 <.002 -- -- <.10 <.05 <.04 LUSRC1-3 <.04 <.05 <.07 E.301 E.03 <.07 <.10 <.05 <.04 LUSRC1-4 <.04 <.05 <.07 E.004 <.06 <.07 <.10 <.05 <.04 LUSRC1-5 <.04 <.05 <.07 E.004 <.06 <.07 <.10 <.05 <.04 LUSRC1-6 <.04 <.05 <.07 E.004 <.06 <.07 <.10 <.05 <.04 LUSRC1-7 <.04 <.05 <.07 <.002 <.06 <.07 <.10 <.05 <.04 LUSRC1-8 <.04 <.05 <.07 E.031 M <.07 <.10 <.05 <.04 LUSRC1-9 <.04 <.05 <.07 E.009 <.06 <.07 <.10 <.05 <.04 LUSRC1-10 <.04 <.05 <.07 E.365 E.13 E.01 <.10 <.05 <.04 LUSRC1-11 <.04 <.05 <.07 E.074 E.06 E.07 <.10 <.05 <.04 LUSRC1-12 <.04 <.05 <.07 E.206 E.04 <.07 <.10 <.05 <.04 LUSRC1-13 <.04 <.05 <.07 E.024 E.01 <.07 <.10 <.05 <.04 LUSRC1-14 <.04 <.05 <.07 <.002 <.06 <.07 <.10 <.05 <.04 LUSRC1-15 <.04 <.05 <.07 <.002 <.06 <.07 <.10 <.05 <.04 LUSRC1-16 <.04 <.05 <.07 <.002 <.06 <.07 <.10 <.05 <.04 LUSRC1-17 <.04 <.05 <.07 E.112 .07 E.05 <.10 <.05 <.04 LUSRC1-18 <.04 <.05 <.07 <.002 <.06 <.07 <.10 <.05 <.04 LUSRC1-19 <.04 <.05 <.07 E.003 E.01 <.07 <.10 <.05 <.04 LUSRC1-20 <.04 <.05 <.07 E.045 E.09 E.11 <.10 <.05 <.04 LUSRC1-21 <.04 <.05 <.07 <.002 <.06 <.07 <.10 <.05 <.04 LUSRC1-22 <.04 <.05 <.07 <.002 <.06 <.07 <.10 <.05 <.04 LUSRC1-23 <.04 <.05 <.07 <.002 <.06 <.07 <.10 <.05 <.04 LUSRC1-24 <.04 <.05 <.07 <.002 <.06 <.07 <.10 <.05 <.04 LUSRC1-25 <.04 <.05 <.07 <.002 <.06 <.07 <.10 <.05 <.04 LUSRC1-26 <.04 <.05 <.07 <.002 <.06 <.07 <.10 <.05 <.04 LUSRC1-27 <.04 <.05 <.07 <.002 <.06 <.07 <.10 <.05 <.04 LUSRC1-28 <.04 <.05 <.07 E.004 <.06 <.07 <.10 <.05 <.04 LUSRC1-29 <.04 <.05 <.07 E.004 M <.07 <.10 <.05 <.04 LUSRC1-30 <.04 <.05 <.07 <.002 <.06 <.07 <.10 <.05 <.04 
36 Comparison Between Agricultural and Urban Ground-Water Quality in the Mobile River Basin, 1999–2001 Appendix table 2. Results of analyses of urban ground water for constituents of NWQL Lab Code 9060—Continued

[μg/L, microgram per liter; <, less than; E, estimated value; M, presence verified but not quantified]

WELL Fenuron (μg/L) Flumetsulam 

(μg/L)

Fluometuron 

(μg/L)

Hydroxy 

atrazine 

(μg/L)

Imazaquin 

(μg/L)

Imazethapyr 

(μg/L)

Imidacloprid 

(μg/L)

Linuron 

(μg/L)

MCPA 

 (μg/L)

LUSCR1-1 <0.07 <0.09 <0.06 E0.1 <0.1 <0.09 <0.1 <0.07 <0.06 LUSRC1-2 <.07 <.09 <.06 <.2 <.1 <.09 <.1 <.07 <.06 LUSRC1-3 <.07 <.09 <.06 <.2 <.1 <.09 <.1 <.07 <.06 LUSRC1-4 <.07 <.09 <.06 <.2 <.1 E.03 <.1 <.07 <.06 LUSRC1-5 <.07 <.09 <.06 <.2 <.1 <.09 <.1 <.07 <.06 LUSRC1-6 <.07 <.09 <.06 <.2 <.1 <.09 <.1 <.07 <.06 LUSRC1-7 <.07 <.09 <.06 <.2 <.1 -- <.1 <.07 <.06 LUSRC1-8 <.07 <.09 <.06 E.1 <.1 -- <.1 <.07 <.06 LUSRC1-9 <.07 <.09 <.06 <.2 <.1 <.09 <.1 <.07 <.06 LUSRC1-10 <.07 <.09 .07 <.2 <.1 -- <.1 <.07 <.06 LUSRC1-11 <.07 <.09 <.06 M <.1 <.09 .1 <.07 <.06 LUSRC1-12 <.07 <.09 <.06 <.2 <.1 <.09 <.1 <.07 <.06 LUSRC1-13 <.07 <.09 <.06 <.2 <.1 <.09 <.1 <.07 <.06 LUSRC1-14 <.07 <.09 <.06 <.2 <.1 <.09 <.1 <.07 <.06 LUSRC1-15 <.07 <.09 <.06 <.2 <.1 <.09 <.1 <.07 <.06 LUSRC1-16 <.07 <.09 <.06 <.2 <.1 <.09 <.1 <.07 <.06 LUSRC1-17 <.07 <.09 <.06 E.1 M <.09 <.1 <.07 <.06 LUSRC1-18 <.07 <.09 <.06 <.2 <.1 <.09 <.1 <.07 <.06 LUSRC1-19 <.07 <.09 <.06 <.2 <.1 -- <.1 <.07 <.06 LUSRC1-20 <.07 <.09 <.06 <.2 <.1 -- <.1 <.07 <.06 LUSRC1-21 <.07 <.09 <.06 <.2 <.1 <.09 <.1 <.07 <.06 LUSRC1-22 <.07 <.09 <.06 <.2 <.1 <.09 <.1 <.07 <.06 LUSRC1-23 <.07 <.09 <.06 <.2 <.1 -- <.1 <.07 <.06 LUSRC1-24 <.07 <.09 <.06 <.2 <.1 <.09 <.1 <.07 <.06 LUSRC1-25 <.07 <.09 <.06 <.2 <.1 <.09 <.1 <.07 <.06 LUSRC1-26 <.07 <.09 <.06 <.2 <.1 <.09 <.1 <.07 <.06 LUSRC1-27 <.07 <.09 <.06 <.2 <.1 <.09 <.1 <.07 <.06 LUSRC1-28 <.07 <.09 <.06 <.2 <.1 <.09 <.1 <.07 <.06 LUSRC1-29 <.07 <.09 <.06 <.2 <.1 -- <.1 <.07 <.06 LUSRC1-30 <.07 <.09 <.06 <.2 <.1 <.09 <.1 <.07 <.06 
Appendix 37

Appendix table 2. Results of analyses of urban ground water for constituents of NWQL Lab Code 9060—Continued[μg/L, microgram per liter; <, less than; E, estimated value; M, presence verified but not quantified]

WELL Methiocarb (μg/L) Methomyl oxime (μg/L) Methomyl (μg/L) Metsulfuron methyl (μg/L) Neburon (μg/L) Nico sulfuron (μg/L) Norflurazon (μg/L) Oryzalin (μg/L) Oxamy

oxime (μg/L

LUSCR1-1 <0.08 <0.01 <0.08 <0.1 <0.07 <0.07 <0.08 <0.07 <0.06 LUSRC1-2 <.08 <.01 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-3 <.08 <.01 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-4 <.08 <.01 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-5 <.08 <.01 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-6 <.08 <.01 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-7 <.08 <.20 <.08 <.2 <.07 <.07 <.08 <.07 <.06 LUSRC1-8 <.08 <.20 <.08 <.2 <.07 <.07 <.08 <.07 <.06 LUSRC1-9 <.08 <.01 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-10 <.08 <.20 <.08 <.2 <.07 <.07 E.02 <.07 <.06 LUSRC1-11 <.08 <.01 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-12 <.08 <.01 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-13 <.08 <.01 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-14 <.08 <.01 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-15 <.08 <.01 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-16 <.08 <.01 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-17 <.08 <.01 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-18 <.08 <.01 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-19 <.08 <.20 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-20 <.08 <.20 <.08 <.2 <.07 <.07 <.08 <.07 <.06 LUSRC1-21 <.08 <.01 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-22 <.08 <.01 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-23 <.08 <.01 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-24 <.08 <.01 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-25 <.08 <.01 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-26 <.08 <.01 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-27 <.08 <.01 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-28 <.08 <.01 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-29 <.08 <.20 <.08 <.1 <.07 <.07 <.08 <.07 <.06 LUSRC1-30 <.08 <.01 <.08 <.1 <.07 <.07 <.08 <.07 <.06 
38 Comparison Between Agricultural and Urban Ground-Water Quality in the Mobile River Basin, 1999–2001 Appendix table 2. Results of analyses of urban ground water for constituents of NWQL Lab Code 9060—Continued

[μg/L, microgram per liter; <, less than; E, estimated value; M, presence verified but not quantified]

WELL Propham 

(μg/L)

Pro

piconazole 

(μg/L)

Propoxur 

(μg/L)

Siduron 

 (μg/L)

Sulfo

metruron 

methyl 

(μg/L)

Tebuthiuron 

(μg/L)

Terbacil

 (μg/L)

Tribenuron 

methyl 

 (μg/L)

LUSCR1-1 <0.07 <0.06 <0.06 <0.09 <0.04 <0.01 <0.10 <0.07 LUSRC1-2 <.07 <.06 <.06 <.09 <.04 <.01 -- <.07 LUSRC1-3 <.07 <.06 <.06 <.09 <.04 <.01 <.10 <.07 LUSRC1-4 <.07 <.06 <.06 <.09 <.04 <.01 <.10 <.07 LUSRC1-5 <.07 <.06 <.06 <.09 <.04 <.01 E.03 <.07 LUSRC1-6 <.07 <.06 <.06 <.09 <.04 <.01 <.10 <.07 LUSRC1-7 <.07 <.06 <.06 <.09 <.04 <.01 <.10 <.07 LUSRC1-8 <.07 <.06 <.06 <.09 <.04 <.01 <.10 <.07 LUSRC1-9 <.07 <.06 <.06 <.09 <.04 <.01 <.10 <.07 LUSRC1-10 <.07 <.06 <.06 <.09 <.04 <.01 <.10 <.07 LUSRC1-11 <.07 <.06 <.06 <.09 <.04 M <.10 <.07 LUSRC1-12 <.07 <.06 E.04 <.09 M <.01 <.10 <.07 LUSRC1-13 <.07 <.06 <.06 <.09 <.04 <.01 <.10 <.07 LUSRC1-14 <.07 <.06 <.06 <.09 <.04 <.01 <.10 <.07 LUSRC1-15 <.07 <.06 <.06 <.09 <.04 <.01 <.10 <.07 LUSRC1-16 <.07 <.06 <.06 <.09 <.04 <.01 <.10 <.07 LUSRC1-17 <.07 <.06 <.06 <.09 <.04 <.01 <.10 <.07 LUSRC1-18 <.07 <.06 <.06 <.09 <.04 <.01 <.10 <.07 LUSRC1-19 <.07 <.06 <.06 <.09 <.04 <.01 <.10 <.07 LUSRC1-20 M <.06 <.06 <.09 <.04 <.01 <.10 <.07 LUSRC1-21 <.07 <.06 <.06 <.09 <.04 <.01 <.10 <.07 LUSRC1-22 <.07 <.06 <.06 <.09 <.04 <.01 <.10 <.07 LUSRC1-23 <.07 <.06 <.06 <.09 <.04 <.01 <.10 <.07 LUSRC1-24 <.07 <.06 <.06 <.09 <.04 <.01 <.10 <.07 LUSRC1-25 <.07 <.06 <.06 <.09 <.04 <.01 <.10 <.07 LUSRC1-26 <.07 <.06 <.06 <.09 <.04 <.01 <.10 <.07 LUSRC1-27 <.07 <.06 <.06 <.09 <.04 <.01 E.02 <.07 LUSRC1-28 <.07 <.06 <.06 <.09 <.04 <.01 <.10 <.07 LUSRC1-29 <.07 <.06 <.06 <.09 <.04 <.01 <.10 <.07 LUSRC1-30 <.07 <.06 <.06 <.09 <.04 <.01 <.10 <.07