Occurrence and Distribution of Nutrients, 

Suspended Sediment, and Pesticides in the 

Mobile River Basin, Alabama, Georgia, 

Mississippi, and Tennessee, 1999 – 2001 

By Ann K. McPherson, Richard S. Moreland, and J. Brian Atkins 

U.S. GEOLOGICAL SURVEY 

Water-Resources Investigations Report 03 – 4203 

NATIONAL WATER-QUALITY ASSESSMENT PROGRAM 

Montgomery, Alabama 

2003 
U.S. DEPARTMENT OF THE INTERIOR 

GALE A. NORTON, Secretary 

U.S. GEOLOGICAL SURVEY

CHARLES G. GROAT, Director 

Cover photographs 

B 

A 

E 

C 

D 

A Cypress trees found in wetlands of the Mobile River Basin (A.K. McPherson, 

USGS) 

B Tug boat and coal laden barges on the Black Warrior River (H. Zappia, USGS) 

C Rolling hills and pastureland of the Valley and Ridge Province in northwest 

Georgia (A.K. McPherson, USGS) 

D Cotton fields located in the Black Prairie Belt of Alabama (D.A. Harned, USGS) 

E Stream reach upstream from USGS streamgaging station 02458450 in 

Birmingham, Alabama (A.K. McPherson, USGS) 

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. 

For additional information write to: 

District Chief 

U.S. Geological Survey

2350 Fairlane Drive, Suite 120 

Montgomery, AL 36116 

email: dc_al@usgs.gov 

Copies of this report can be purchased from: 

U.S. Geological Survey

Branch of Information Services 

Box 25286, Federal Center 

Denver, CO 80225 

1-888-ASK-USGS (275-8747) 

Information regarding the National Water-Quality Assessment (NAWQA) Program can be obtained from the National 

Web site http://water.usgs.gov/nawqa/nawqa_home.html or the Mobile River Basin Study Unit Web site 

http://tenn.er.usgs.gov/MOBL/mobl.html. 
FOREWORD

The U.S. Geological Survey (USGS) is 

committed to serve the Nation with accurate and 

timely scientific information that helps enhance and 

protect the overall quality of life, and facilitates 

effective management of water, biological, energy, and 

mineral resources. Information on the quality of the 

Nation’s water resources is of critical interest to the 

USGS because it is so integrally linked to the 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 

Foreword III 
CONTENTS


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


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


Purpose and scope ....................................................................................................................................................... 4


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


Description of the study unit ....................................................................................................................................... 4


Description of the sampling sites ................................................................................................................................ 4


Estimated pesticide use in the study area .................................................................................................................... 9


Methods................................................................................................................................................................................. 14


Sampling frequency..................................................................................................................................................... 14


Sample collection ........................................................................................................................................................ 14


Selection of pesticide analytes .................................................................................................................................... 14


Data analysis and review ............................................................................................................................................. 15


Quality-control methods and results ................................................................................................................. 17


Nutrients ................................................................................................................................................................................ 22


Nitrogen....................................................................................................................................................................... 23


Phosphorus .................................................................................................................................................................. 27


Organic carbon ............................................................................................................................................................ 31


Loads and yields of nutrients ...................................................................................................................................... 31


Trends.......................................................................................................................................................................... 39


Suspended sediment .............................................................................................................................................................. 39


Loads and yields of suspended sediment .................................................................................................................... 42


Pesticides............................................................................................................................................................................... 44


Occurrence of pesticides by sampling site .................................................................................................................. 52


Bogue Chitto Creek near Memphis, Alabama .................................................................................................. 52


Cahaba River at Centreville, Alabama .............................................................................................................. 52


Cahaba Valley Creek at Cross Creek Road at Pelham, Alabama...................................................................... 52 


Threemile Branch at North Boulevard at Montgomery, Alabama .................................................................... 53


Alabama River at Claiborne, Alabama.............................................................................................................. 53


Black Warrior River below Bankhead Lock and Dam near Bessemer, Alabama ............................................. 53


Tombigbee River below Coffeeville Lock and Dam near Coffeeville, Alabama.............................................. 54


Occurrence of pesticides in the Mobile River Basin ................................................................................................... 54


Occurrence of pesticides in the Mobile River Basin compared to other NAWQA Study Units ................................. 58


Summary ............................................................................................................................................................................... 60


Selected references................................................................................................................................................................ 62


Appendixes............................................................................................................................................................................ 66


FIGURES 

1–3. Maps showing: 

1. Study Units of the U.S. Geological Survey’s National Water-Quality Assessment Program, 


identified by a four-letter basin code ............................................................................................................. 3


2. Physiographic provinces of the Mobile River Basin Study Unit. .................................................................... 5


3. Land use and locations of sampling sites in the Mobile River Basin Study Unit............................................ 6


4–26. Graphs showing: 


4. Land use in the watersheds of sampling sites in the Mobile River Basin........................................................ 8


5. Herbicide use in the Mobile River Basin, 1997 ............................................................................................... 10


6. Insecticide use in the Mobile River Basin, 1997 ............................................................................................. 10


7. Fungicide use in the Mobile River Basin, 1997............................................................................................... 11


8. Spike recoveries for pesticides and degradation products analyzed by the (A) GC/MS method, 


and the (B) HPLC/MS method in surface-water samples from the Mobile River Basin............................... 19


Contents V 
9. Recoveries of surrogate compounds in surface-water samples from the Mobile River Basin ......................... 21


10. Distribution of total nitrogen, nitrite plus nitrate, and total ammonia plus organic nitrogen 


concentrations at sites in the Mobile River Basin .......................................................................................... 24


11. Monthly median concentrations of nitrite plus nitrate and ammonia plus organic nitrogen 


at sites in the Mobile River Basin................................................................................................................... 25


12. Relation between total nitrogen concentrations and streamflow at sites in the Mobile River Basin ............... 26


13. Distribution of dissolved phosphorus, orthophosphate, and total phosphorus concentrations at sites 


in the Mobile River Basin............................................................................................................................... 28


14. Monthly median concentrations of suspended phosphorus and dissolved phosphorus at sites in the 


Mobile River Basin......................................................................................................................................... 29


15. Relation between total phosphorus concentrations and streamflow at sites in the Mobile River Basin .......... 30


16. Distribution of dissolved and suspended organic carbon concentrations at sites in the Mobile River Basin .. 32


17. Trends in flow-adjusted total nitrogen, total ammonia and organic nitrogen, and dissolved nitrate 


concentrations for the Alabama, Tombigbee, and Cahaba River Basins........................................................ 40


18. Trends in flow-adjusted total phosphorus, dissolved phosphorus, and dissolved orthophosphate 


concentrations for the Alabama, Tombigbee, and Cahaba River Basins........................................................ 41


19. Distribution of suspended-sediment concentrations at sites in the Mobile River Basin .................................. 42


20. Relation between suspended-sediment concentrations and streamflow at sites in the Mobile River Basin .... 43


21. Median monthly total pesticide concentrations at selected sites in the Mobile River Basin, 


January 1999–December 2001....................................................................................................................... 45


22. Atrazine concentrations and corresponding streamflow at six sites in the Mobile River Basin, 


January 1999–December 2001....................................................................................................................... 48


23. Simazine concentrations and corresponding streamflow at six sites in the Mobile River Basin, 


January 1999–December 2001....................................................................................................................... 49


24. Metolachlor concentrations and corresponding streamflow at six sites in the Mobile River Basin,


January 1999–December 2001....................................................................................................................... 50


25. Frequencies of pesticide detections in surface-water samples from the Mobile River Basin, 1999–2001 ..... 54


26. Frequencies of pesticide detections in surface-water samples from (A) agricultural, (B) urban, and 

(C) mixed land-use sites in the Mobile River Basin and at other National Water-Quality Assessment 


Study Units throughout the United States ...................................................................................................... 59


TABLES 

1. Site descriptions and sampling frequency of selected constituents at sites in the Mobile River Basin, 


Alabama, 1999–2001 ............................................................................................................................................ 7


2. Laboratory reporting levels and minimum reporting levels of pesticides and pesticide metabolites sampled 


in the Mobile River Basin ...................................................................................................................................... 11


3. Nutrient criteria recommended by the U.S. Environmental Protection Agency for ecoregions 


in the Mobile River Basin ...................................................................................................................................... 22


4. Regression summary for the seven-parameter, log-linear regression model used to estimate nutrient 


concentrations at sites in the Mobile River Basin.................................................................................................. 33


5. Flow-weighted mean nutrient concentrations at sites in the Mobile River Basin .................................................... 38


6. Water-quality standards, guidelines, and maximum concentrations of pesticides detected in surface-water 


samples from the Mobile River Basin ................................................................................................................... 51


7. Agricultural production in the Mobile River Basin, 2001........................................................................................ 55


8. Selected herbicides, insecticides, and fungicides applied to crops in Alabama, 1997............................................. 56


VI Contents 
APPENDIX TABLES 

APPENDIX 1 Quality Control 

Concentrations and relative percentage differences for pesticides detected in 46 replicate 

samples from the Mobile River Basin, 1999–2001 ...................................................................................... 66 

APPENDIX 2 Summary statistics for nutrients, organic carbon, and suspended sediment 

Summary statistics for nutrients, organic carbon, and suspended sediment in surface-water 

samples collected from the Mobile River Basin, 1999–2001 ....................................................................... 75 

APPENDIX 3 Summary statistics for pesticides 

Summary statistics for pesticides in surface-water samples collected 

from the Mobile River Basin, 1999–2001 .................................................................................................... 81 

CONVERSION FACTORS, ABBREVIATIONS, and ACRONYMS 

Multiply by To obtain 

Length 

inch (in.) 25.4 millimeter (mm) 

foot (ft) 

mile (mi) 

0.3048 

1.609 

meter (m) 

kilometer (km2

) 

Area 

acre 

square mile (mi2) 

0.4047 

2.590 

hectare (ha) 

square kilometer (km2

) 

Volume 

gallon (gal) 

acre-foot (acre-ft) 

3.785 

1,223 

liter (L) 

cubic meter (m3

) 

Flow 

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s) 

Mass 

pound, avoirdupois (lb) 0.4536 kilogram (kg) 

ABBREVIATIONS 

kg/d 

(kg/d)/mi2 

mg/L 

ton/d 

(ton/d)/mi2 

μg/L 

μm 

< 

kilograms per day 

kilograms per day per square mile 

milligrams per liter 

tons per day 

tons per day per square mile 

micrograms per liter 

micron 

less than 

Contents VII 
ACRONYMS 

ADEM Alabama Department of Environmental Management 

AMLE adjusted maximum likelihood estimator 

ANOVA analysis of variance 

alpha-HCH alpha-Hexachlorocyclohexane 

DCPA Dacthal – dimethyl 2,3,5,6-tetrachloro-1,4-benzenedicarboxylate 

DSMA disodium methanearsonate 

E concentration is estimated 

EPTC 5-ethyl dipropylthiocarbamate 

GC/MS gas chromatography/mass spectrometry 

HPLC/MS high-performance liquid chromatography/mass spectrometry 

LOWESS locally weighted scatterplot smoothing 

LRL laboratory reporting level 

LRS laboratory reagent spike 

LT-MDL long-term method detection level 

MCL maximum contaminant level 

MCPA (4-chloro-2-methyl)phenoxyacetic acid 

MCPB 4-(4-chloro-2-methylphenoxy)butanoic acid 

MOBL Mobile River Basin NAWQA Study Unit 

MRL minimum reporting level 

MRLC multi-resolution land characteristics 

MSMA monosodium methanearsonate 

MVUE minimum variance unbiased estimator 

NAS/NAE National Academy of Sciences and National Academy of Engineering 

NAWQA National Water-Quality Assessment 

NWQL National Water Quality Laboratory 

THM trihalomethane 

USEPA U.S. Environmental Protection Agency 

USGS U.S. Geological Survey 

WY Water year is the period October 1 through September 30, and is identified by the 

year in which it ends. 

VIII Contents 
Occurrence and Distribution of Nutrients, Suspended Sediment, 

and Pesticides in the Mobile River Basin, Alabama, Georgia, 

Mississippi, and Tennessee, 1999 –2001 

By Ann K. McPherson, Richard S. Moreland, and J. Brian Atkins 

ABSTRACT 

The Mobile River Basin is one of more than 

50 river basins and aquifer systems being investigated 

as part of the U.S. Geological Survey’s National WaterQuality Assessment (NAWQA) Program. This basin is 

the sixth largest river basin in the United States and the 

fourth largest in terms of streamflow. The Mobile River 

Basin encompasses parts of Alabama, Georgia, 

Mississippi, and Tennessee, and almost two-thirds of 

the 44,0000-square-mile basin is located in Alabama. 

The extensive water resources of the Mobile River 

Basin are influenced by an array of natural and cultural 

factors, which impart unique and variable qualities to 

the streams, rivers, and aquifers and provide abundant 

habitat to sustain the diverse aquatic life in the basin. 

From January 1999 to December 2001, a study 

was conducted of the occurrence and distribution of 

nutrients, suspended sediment, and pesticides in 

surface water of the Mobile River Basin. Nine 

sampling sites were selected on the basis of land use. 

The nine sites included two streams draining 

agricultural areas, two urban streams, and five large 

rivers with mixed land use. Surface-water samples 

were collected from one to four times each month to 

characterize the spatial and temporal variation in 

nutrient and pesticide concentrations. 

Nutrient and suspended-sediment concentrations 

were highest in watersheds dominated by urban or 

agricultural land uses. Forty-two percent of the total 

phosphorus concentrations at all nine sites exceeded 

the U.S. Environmental Protection Agency’s 

recommended maximum concentration of 

0.1 milligram per liter. Flow-weighted mean 

concentrations at the Mobile River Basin sites 

generally were in the lower to middle percentile ranges 

compared with data from other NAWQA studies across 

the Nation. However, flow-weighted mean concentrations of ammonia, total nitrogen, orthophosphate, and 

total phosphorus at Bogue Chitto Creek, an agricultural 

watershed, ranked in the upper 20th percentile of 

agricultural sites sampled across the Nation as part of 

the NAWQA Program. Nutrient loads in the 

Tombigbee River were nearly twice as high compared 

with nutrient loads in the Alabama River. Nutrient 

yields were highest in Bogue Chitto Creek, Cahaba 

Valley Creek, and Threemile Branch because of 

agricultural and urban land uses in these watersheds. 

Of the 104 pesticides and degradation products 

analyzed in the stream samples, 69 were detected in 

one or more samples. Of the 69 detected pesticides, 

51 were herbicides, 15 were insecticides, and 3 were 

fungicides. A relatively small number of heavily used 

herbicides accounted for most of the detections, 

including atrazine and its metabolites (deethylatrazine, 

2-hydroxyatrazine, deisopropylatrazine, and 

deethyldeisopropylatrazine), simazine, metolachlor, 

tebuthiuron, prometon, diuron, and 2,4-D. Diazinon, 

chlorpyrifos, and carbaryl were the most frequently 

detected insecticides; metalaxyl was the most 

frequently detected fungicide in the Mobile River 

Basin. 

Concentrations of pesticides detected in surface 

water of the Mobile River Basin were among the 

highest concentrations recorded nationally by the 

NAWQA Program during 1991 to 2001. The three 

highest concentrations of atrazine detected at sites 

across the country were recorded at Bogue Chitto 

Creek; the highest concentrations of 2,4-D, imazaquin, 

and malathion recorded nationally were detected at 

Abstract 1 
Threemile Branch. Aquatic-life criteria were exceeded 

by concentrations of five herbicides (2,4-D, atrazine, 

cyanazine, diuron, and metolachlor), six insecticides 

(carbaryl, chlorpyrifos, diazinon, dieldrin, malathion, 

and p,p '-DDE), and one fungicide (chlorothalonil). 

Drinking-water standards were exceeded by 

concentrations of four herbicides (2,4-D, atrazine, 

cyanazine, and simazine), three insecticides (alphaHCH, diazinon, and dieldrin), and one fungicide 

(chlorothalonil). 

The types and concentrations of pesticides found 

in surface water are linked to land use and to the types 

of pesticides used in each setting. Herbicides were 

detected more frequently and usually at higher 

concentrations in the agricultural stream, Bogue Chitto 

Creek. Insecticides, however, were detected more 

frequently and usually at higher concentrations in 

urban streams (Cahaba Valley Creek, Threemile 

Branch). Concentrations of pesticides varied 

seasonally in streams in response to the timing and 

amount of pesticides used and the frequency and 

magnitude of runoff from precipitation and irrigation. 

At Bogue Chitto Creek, the highest concentrations of 

atrazine were observed in April, May, and June, which 

coincide with its use as a preemergent herbicide on 

corn; the highest concentrations of cyanazine were 

observed in July and August, which coincide with its 

use as a postemergent herbicide on cotton. Seasonal 

patterns were less evident in urban streams, where 

concentrations of herbicides and insecticides remained 

relatively constant throughout the year. 

Concentrations of pesticides in the large rivers 

generally were much lower than in their corresponding 

tributaries because of dilution and runoff from other 

land-use areas within the larger, more integrated 

basins. However, marked similarities were noted 

between the small streams with one primary land use 

and the large rivers draining basins encompassing these 

small streams. For example, the agricultural pesticides 

found in the Tombigbee River reflected those 

compounds present in its tributary, Bogue Chitto 

Creek, and the urban pesticides found in the Cahaba 

River reflected those compounds found in its tributary, 

Cahaba Valley Creek. 

INTRODUCTION 

The goal of the National Water-Quality 

Assessment (NAWQA) Program is to assess the status 

and trends in the quality of the Nation’s ground- and 

surface-water resources on a regional or national scale, 

and to relate the status and trends with an understanding of the natural and human factors that affect the 

quality of water (Gilliom and others, 1995). In 1997, 

the U.S. Geological Survey (USGS) began an assessment of water quality in the Mobile River Basin. The 

Mobile River Basin (MOBL) is one of more than 

50 river basins and aquifer systems (Study Units) being 

studied as part of the NAWQA Program (fig. 1). These 

Study Units represent the diverse geography, water 

resources, and land and water uses of the Nation. 

In the NAWQA Program, an integrated approach 

is used to assess water quality. Physical, chemical, and 

biological data are collected over a wide range of 

conditions and used to determine water quality. As part 

of the NAWQA Program, a 3-year period of intensive 

data collection at each of the Study Units is followed by 

a 6-year low-intensity phase, in which fewer sites are 

sampled less frequently. This cycling of high-intensity 

and low-intensity data collection is repeated over time 

to assess trends in water quality. The results of this 

study, when combined with other NAWQA studies 

across the Nation, will provide resource managers and 

interested partners with a better understanding of how 

ecosystems respond to land-use changes and how these 

responses vary across a range of environmental 

settings. 

This report focuses on the occurrence and 

distribution of nutrients, suspended sediment, and 

pesticides in the Mobile River Basin. Nutrients are 

chemical elements that are essential to plants and 

animals (Mueller and Helsel, 1996). These elements 

include various forms of reduced or oxidized nitrogen 

and phosphorus and, to a lesser extent, organic carbon. 

While nitrogen and phosphorus are natural and 

important elements in a healthy aquatic environment, 

excessive levels can be detrimental to aquatic 

ecosystems and the health of organisms using the 

water. Nonpoint nutrient sources include atmospheric 

deposition, biological fixation, animal manure, and 

applications of fertilizers; point nutrient sources 

include faulty septic tanks, outfall from industrial 

sources, and wastewater-treatment plants. 

Pesticides are substances or mixtures of 

substances that are used to control pests, such as insects 

(insecticides), weeds (herbicides), and fungi 

(fungicides). Pesticides have been used in agricultural 

areas for many years, and their use in urban and 

undeveloped areas has increased in recent decades 

(Barbash and Resek, 1996). Because of their 

2 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999– 2001 
Introduction 3 Figure 1. Study Units of the U.S. Geological Survey’s National Water-Quality Assessment Program, identified by a four-letter basin c
widespread use, pesticides commonly are detected in 

streams and lakes (Larson and others, 1997). Many 

pesticides break down slowly in the environment; 

therefore, pesticide residuals or breakdown products 

also are found frequently in streams (Maluk, 2000). 

Possible human health effects from overexposure to 

some pesticides include cancer, reproductive or 

nervous-system disorders, and acute toxicity. In 

relation to the health of aquatic life, recent studies 

indicate that some pesticides may disrupt endocrine 

systems and affect reproduction by interfering with 

natural hormones (U.S. Geological Survey, 1999). 

Purpose and Scope 

The purpose of this report is to describe the 

spatial and seasonal variability in nutrient, suspendedsediment, and pesticide concentrations at nine surfacewater sites and to relate these concentrations to 

streamflow conditions and land-use activities in the 

Mobile River Basin, 1999–2001. The nine sites 

included two streams draining agricultural areas, two 

urban streams, and five large rivers with mixed land 

use. Surface-water samples were collected from one to 

four times each month, from January 1999 to 

December 2001, and analyzed for a suite of nutrient 

species and pesticide compounds. This report also 

presents the results of load and yield estimates for 

nitrogen, phosphorus, and suspended sediment at the 

nine sites in the basin. 

Acknowledgments 

The authors gratefully appreciate the 

contributions of Richard H. Coupe, hydrologist with 

the USGS in Pearl, Mississippi, and Douglas A. 

Harned, hydrologist with the USGS in Raleigh, North 

Carolina, for their technical assistance during the 

preparation and review of this report. 

Description of the Study Unit 

The Mobile River Basin is the sixth largest river 

basin in the Nation, encompassing nearly 44,000 

square miles (mi2) and draining portions of 

Mississippi, Tennessee, Georgia, and Alabama (fig. 2; 

Lamb, 1979). The Alabama and Tombigbee Rivers join 

to form the Mobile River, which then flows into Mobile 

Bay and discharges into the Gulf of Mexico. 

Approximately 70 percent of the basin lies in Alabama, 

14 percent in Mississippi, 13 percent in Georgia, and 

2 percent in Tennessee. The major land use in the 

Mobile River Basin is forested land, which covers 

approximately 70 percent of the basin. Agricultural 

land, including livestock and pastureland, covers 

approximately 26 percent of the basin, and urban areas 

account for only 3 percent of the total land use (fig. 3; 

Johnson and others, 2002). Agricultural activities 

include row crops, such as corn, soybeans, cotton, 

wheat, and sorghum; aquaculture; and poultry, swine, 

and cattle production. Major industries in the basin 

include silviculture and the production of chemicals, 

pulp and paper, iron and steel, coal, and textiles 

(Atkins, 1998). More detailed descriptions of the 

geographic setting, including physiography, geology, 

soils, climate, hydrology, and ecoregions, are described 

by Johnson and others (2002). 

Description of the Sampling Sites

 Major components of the site-selection process 

were to target specific watersheds that are influenced 

primarily by a dominant land use and to investigate the 

occurrence and distribution of nutrients and pesticides 

in the watersheds. Surface-water quality was monitored 

at two types of sites—basic fixed sites and intensive 

fixed sites. Basic fixed sites were sampled monthly for 

a period of 2 years. Intensive fixed sites were sampled 

more frequently for at least 1 year to characterize shortterm variations in water quality. Both basic and 

intensive fixed sites are further classified as either 

indicator or integrator sites. Indicator sites represent 

relatively homogeneous and usually small basins 

associated with specific environmental settings. 

Integrator sites are established at downstream points in 

large drainage basins and represent the effects of 

multiple land uses in the basin (Gilliom and others, 

1995). 

Three intensive fixed sites and six basic fixed 

sites were selected for study in the Mobile River Basin 

(table 1; fig. 3). The three intensive fixed sites include 

an urban indicator site (Cahaba Valley Creek) at 

Pelham, Ala.; an agricultural indicator site (Bogue 

Chitto Creek) near Memphis, Ala.; and an integrator 

site (Cahaba River) at Centreville, Ala. The six basic 

fixed sites include two indicator sites and four 

integrator sites. The two basic indicator sites include a 

livestock agricultural area in the Black Prairie Belt 

(Pintlalla Creek) and an urban area (Threemile Branch) 

in Montgomery, Ala. The four basic integrator sites 

4 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999– 2001 
Description of the Sampling Sites 5

Figure 2. Physiographic provinces of the Mobile River Basin Study Unit.
6 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999 – 2001

Figure 3. Land use and locations of sampling sites in the Mobile River Basin Study Unit.
Table 1. Site descriptions and sampling frequency of selected constituents at sites in the Mobile River Basin, Alabama, 1999–2001 

[mi2, square miles; GC/MS, gas chromatography/mass spectrometry; HPLC/MS, high-performance liquid chromatography/mass spectrometry] 

Site 

number 

(fig. 3) 

Station 

number Station name 

Type of 

fixed 

site 

Site 

classification 

Drainage 

area 

(mi2) 

Sampling period Nutrients S

s

1 02398300 Chattooga River above Gaylesville, Ala. Basic Integrator 366 01/1999 –12/2000 25 2 02419977 Threemile Branch at North Boulevard at Basic Urban 8.79 01/1999 –09/2001 35 

Montgomery, Ala. indicator 

3 02421115 Pintlalla Creek at Liberty Church Road Basic Agricultural 59.3 01/1999 –12/2000 24 

near Pintlalla, Ala. indicator 

4 0242354750 Cahaba Valley Creek at Cross Creek Intensive Urban 25.6 01/1999 –12/2001 74 

Road at Pelham, Ala. indicator 

5 02424000 Cahaba River at Centreville, Ala. Intensive Integrator 1,027 01/1999 –09/2001 41 6 02429500 Alabama River at Claiborne, Ala. Basic Integrator 21,967 01/1999 –12/2001 34 7 02444490 Bogue Chitto Creek near Memphis, Ala. Intensive Agricultural 52.6 01/1999 –12/2001 55 

indicator 

8 02462501 Black Warrior River below Bankhead Basic Integrator 3,979 01/1999 –12/2000 24 

Lock and Dam near Bessemer, Ala. 

9 02469762 Tombigbee River below Coffeeville Basic Integrator 18,417 01/1999 –12/2001 34 

Description of the Lock and Dam near Coffeeville, Ala. Sampling Sites 7 
represent drainage from an area of mixed land use 

typical of the Valley and Ridge (Chattooga River); 

drainage from the Cumberland Plateau stratum (Black 

Warrior River); and drainage from the entire Study Unit 

(Alabama and Tombigbee Rivers). 

The 1992 multi-resolution land characteristics 

(MRLC) map was used to quantify land-use 

characteristics in the watersheds of each of the sites 

(fig. 4). The MRLC is a digital LANDSAT satellite 

image (30-meter resolution) of major land use and land 

cover (U.S. Environmental Protection Agency, 1992a). 

A brief description of relevant characteristics at each of 

the nine sites is presented in the following paragraphs. 

The Bogue Chitto Creek Basin is located 

primarily in Noxubee County, Miss., and drains the 

western part of the Black Prairie Belt, which extends in 

a wide arc through the Mobile River Basin (figs. 2, 3). 

The Black Prairie Belt is distinguished by rich 

vertisols—soils that shrink, swell, and crack (Johnson 

and others, 2002). Land use in the western part of the 

Black Prairie Belt is dominated by row crops, including 

soybeans, corn, cotton, and hay. Land use in the eastern 

part of the Black Prairie Belt is dominated by 

pastureland, with some interspersed areas of row crops. 

Approximately 67 percent of the 53-mi2

 basin consists 

of row crops, and 22 percent is used for pasture or hay 

(fig. 4). Zero-flow conditions were recorded frequently 

at Bogue Chitto Creek during the summer and fall, due 

to the lack of ground-water discharge to the creek 

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

 The Pintlalla Creek Basin, located in 

Montgomery County, lies in the eastern part of the 

Black Prairie Belt. Land use in this basin is dominated 

by forested land and pastureland, with some 

interspersed areas of row crops and hay fields. 

Montgomery County ranks fifth in Alabama in cattle 

and calf production (Vanderberry and Placke, 2002). 

The streams in this basin have little vegetative buffer 

and livestock have access to the headwaters of these 

streams. These factors may promote erosion in the 

Pintlalla Creek Basin. Increased sediment from erosion 

and runoff is considered to be one of the leading 

sources of stream impairment in Alabama (Alabama 

Department of Environmental Management, 2000a). 

Approximately 14 percent of the 59-mi2 basin consists 

of row crops, and 10 percent contains pasture or hay 

(fig. 4). Zero-flow conditions were recorded at Pintlalla 

Creek during periods of drought in the summer and fall 

of 2000 (Pearman and others, 2001, 2002). 

The Chattooga River Basin is located in the 

northeastern section of the Mobile River Basin and 

drains an area that is characteristic of the Valley and 

Figure 4. Land use in the watersheds of sampling sites in the Mobile River Basin. 

8 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999– 2001 
Ridge Province. Agriculture in the Chattooga River 

Basin is typical of the Valley and Ridge—small areas 

of row cropping are in the flat lands of the valleys and 

pasturelands are found in the more rolling terrain. 

Crops are grown in approximately 21 percent of the 

366-mi2 basin (fig. 4) and include corn, soybeans, 

wheat, cotton, and hay (Vanderberry and Placke, 2002). 

Threemile Branch is located in northern 

Montgomery in a suburban area. The stream channel 

contains natural and channelized segments and drains 

an area of 8.79 mi2

 (table 1). The land use of 

approximately 59 percent of the basin is urban and 

includes light industrial activities (fig. 4). 

The Cahaba Valley Creek Basin is located in a 

rapidly developing area in the southeastern part of 

Birmingham. The drainage area of Cahaba Valley 

Creek is approximately 26 mi2 (table 1), and the land 

use in the basin is approximately 9 percent urban and 

78 percent forested (fig. 4). 

The Cahaba River at Centreville drains an area of 

about 1,000 mi2 (table 1) and is one of the drinkingwater sources for the city of Birmingham. 

Approximately 10 percent of the basin is used for the 

cultivation of row crops, pasture, or hay, and about 

81 percent is forested (fig. 4). The Cahaba River is 

home to several endangered species. 

The Black Warrior River below Bankhead Lock 

and Dam is located at the southern edge of the 

Cumberland Plateau and drains an area of 3,979 mi2 

(table 1), integrating various land-use conditions over 

the entire plateau. Intensive agriculture is present in the 

northern part of the Cumberland Plateau; urban areas 

influenced by the city of Birmingham can be seen in the 

east-central part; and active surface and underground 

coal mining is present in the southern part of the 

Cumberland Plateau (Johnson and others, 2002). 

Approximately 17 percent of the basin is used for the 

cultivation of row crops or pasture and hay (fig. 4). 

The Alabama River at Claiborne is located on the 

southeastern rim of the Mobile River Basin and drains 

an area of 21,967 mi2 (table 1). This site is the farthest 

downstream location on the Alabama River within the 

Mobile River Basin that is not affected tidally. 

Approximately 17 percent of the Alabama River Basin 

is used for the cultivation of row crops, pasture, or hay 

(fig. 4). 

The Tombigbee River below Coffeeville Lock 

and Dam is located on the southwestern rim of the 

Mobile River Basin and drains an area of 18,417 mi2 

(table 1). This site is the farthest downstream location 

on the Tombigbee River within the Mobile River Basin 

that is not affected tidally. Approximately 22 percent of 

the Tombigbee River Basin is used for the cultivation of 

row crops, pasture, or hay (fig. 4). 

Estimated Pesticide Use in the Study Area 

The quantities of active ingredients for the top 

20 herbicides used in the study area were determined 

from crop-acreage data compiled from the 1997 

Census of Agriculture (U.S. Department of 

Agriculture, 1999) and from pesticide-use rates 

compiled by the National Center for Food and 

Agricultural Policy (Gianessi and Marcelli, 2000; 

fig. 5). The quantities of active ingredients for the top 

20 insecticides and top 16 fungicides used in the study 

area, which were compiled from the same data sources 

as the herbicides, are shown in figures 6 and 7, 

respectively. Methods used to estimate pesticide use in 

the NAWQA Study Units are described in Thelin and 

Gianessi (2000). The pesticides for which surfacewater samples were analyzed in this study are listed in 

table 2. 

Surface-water samples collected for this study 

were not analyzed for some of the most common 

herbicides (glyphosate, monosodium methanearsonate 

[MSMA], disodium methanearsonate [DSMA], 

paraquat, clomazone, prometryn, and fomesafen) or 

insecticides (oil, acephate, profenofos, thiodicarb, 

phosmet, dicrotophos, sulprofos, lambdacyhalothrin, 

and methamidophos) applied in the Mobile River 

Basin. The pesticide schedules developed by the 

National Water Quality Laboratory and used by 

personnel in the Mobile River Basin Study Unit did not 

include these compounds. Glyphosate, commonly 

known by the brand name Roundup®, is an herbicide 

used widely across the United States (Larson and 

others, 1997) and used frequently on soybeans, cotton, 

and pastureland in the Mobile River Basin (Alabama 

Cooperative Extension System, 1998). MSMA and 

DSMA are herbicides that are used frequently on 

cotton in the Mobile River Basin (Alabama 

Cooperative Extension System, 1998). Other 

compounds, including fungicides and compounds not 

easily categorized as herbicides or insecticides, also are 

applied frequently in the Mobile River Basin (fig. 7). 

Annual use of these other compounds is in the same 

range as the use of herbicides and insecticides, but 

water samples were not analyzed for many of these 

compounds during this study (fig. 7; table 2). 

Estimated Pesticide Use in the Study Area 9 
Figure 5. Herbicide use in the Mobile River Basin, 1997. 

Figure 6. Insecticide use in the Mobile River Basin, 1997. 

10 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999– 2001

Figure 7. Fungicide use in the Mobile River Basin, 1997. 

Table 2. Laboratory reporting levels and minimum reporting levels of pesticides and 

pesticide metabolites sampled in the Mobile River Basin 

[NWIS, National Water Information System; μg/L, micrograms per liter; ND, not detected in any sample; Type: H, herbicide; M, metabolite; I, insecticide; N, nematocide; Ac, acaricide; F, fungicide; Mo, 

molluscicide; PGR, plant growth regulator] 

NWIS 

parameter 

code 

Pesticide Type 

Laboratory 

reporting 

level 

(μg/L) 

82660 2,6-diethylaniline (ND) H, M 0.0017 

49260 Acetochlor H 0.0041 

46342 Alachlor H 0.0024 

34253 Alpha-HCH I 0.0253 

39632 Atrazine H 0.007 

82673 Benfluralin H 0.01 

04028 Butylate (ND) H 0.002 

82680 Carbaryl I 0.041 

82674 Carbofuran I, N 0.02 

38933 Chlorpyrifos I 0.005 

04041 Cyanazine H 0.018 

82682 Dacthal (DCPA) H 0.003 

34653 p,p '-DDE I, M 0.0025 

04040 Deethylatrazine H, M 0.006 

39572 Diazinon I, N 0.005 

39381 Dieldrin I 0.0048 

82677 Disulfoton (ND) I 0.021 

82668 EPTC H 0.002 

82663 Ethalfluralin (ND) H 0.009 

Dissolved pesticides analyzed by gas chromatography/mass spectrometry (GC/MS) 

Estimated Pesticide Use in the Study Area 11 
Table 2. Laboratory reporting levels and minimum reporting levels of pesticides and 

pesticide metabolites sampled in the Mobile River Basin — Continued 

[NWIS, National Water Information System; μg/L, micrograms per liter; ND, not detected in any sample; Type: H, herbicide; M, metabolite; I, insecticide; N, nematocide; Ac, acaricide; F, fungicide; Mo, 

molluscicide; PGR, plant growth regulator] 

Laboratory NWIS 

parameter Pesticide Type reporting 

level code (μg/L) 

Dissolved pesticides analyzed by gas chromatography/mass spectrometry (GC/MS) (Continued)

82672 

04095 

39341 

82666 

39532 

82686 

82667 

39415 

82630 

82671 

82684 

39542 

82669 

82683 

82687 

82664 

04037 

82676 

04024 

82679 

82685 

04035 

82670 

82665 

82675 

82681 

82678 

82661 

Ethoprop 

Fonofox (ND) 

Lindane 

Linuron (ND) 

Malathion 

Methyl azinphos (ND) 

Methyl parathion (ND) 

Metolachlor 

Metribuzin 

Molinate 

Napropamide (ND) 

Parathion (ND) 

Pebulate (ND) 

Pendimethalin 

cis-Permethrin (ND) 

Phorate 

Prometon 

Pronamide 

Propachlor (ND) 

Propanil 

Propargite (ND) 

Simazine 

Tebuthiuron 

Terbacil 

Terbufos (ND) 

Thiobencarb (ND) 

Triallate 

Trifluralin 

I, N 0.005 

I 0.0027 

I 0.004 

H 0.035 

I 0.027 

I 0.05 

I 0.006 

H 0.013 

H 0.006 

H 0.0016 

H 0.007 

I 0.007 

H 0.0016 

H 0.01 

I 0.006 

I 0.011 

H 0.015 

H 0.0041 

H 0.01 

H 0.011 

I, Ac 0.023 

H 0.011 

H 0.016 

H 0.034 

I, N 0.017 

H 0.0048 

H 0.0023 

H 0.009 

Dissolved pesticides analyzed by high-performance liquid chromatography/mass spectrometry 

(HPLC/MS) 

39732 2,4-D H 0.021 

50470 2,4-D methyl ester H 0.0086 

38746 2,4-DB H 0.016 

50355 2-hydroxyatrazine H, M 0.008 

61692 3,4-chlorophenyl-1-methyl urea H 0.024 

49308 3-hydroxycarbofuran (ND) I, M 0.0058 

50295 3-ketocarbofuran (ND) I, M 1.5 

49315 Acifluorfen H 0.0066 

49312 Aldicarb (ND) I, Ac, N 0.04 

49313 Aldicarb sulfone (ND) I, N, M 0.02 

49314 Aldicarb sulfoxide (ND) I, M 0.0082 

50299 Bendiocarb I 0.025 

50300 Benomyl F 0.0038 

61693 Bensulfuron-methyl H 0.015 

38711 Bentazon H 0.011 

04029 Bromacil H 0.033 

12 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999 – 2001 
Table 2. Laboratory reporting levels and minimum reporting levels of pesticides and 

pesticide metabolites sampled in the Mobile River Basin — Continued 

[NWIS, National Water Information System; μg/L, micrograms per liter; ND, not detected in any sample; Type: H, herbicide; M, metabolite; I, insecticide; N, nematocide; Ac, acaricide; F, fungicide; Mo, 

molluscicide; PGR, plant growth regulator] 

Laboratory NWIS 

parameter Pesticide Type reporting 

level code (μg/L) 

Dissolved pesticides analyzed by high-performance liquid chromatography/mass spectrometry 

(HPLC/MS) (Continued) 

49311 Bromoxynil (ND) H 0.017 

49310 Carbaryl I 0.028 

49309 Carbofuran (ND) I, N 0.0056 

61188 Chloramben, methyl ester H 0.018 

50306 Chlorimuron, ethyl (ND) H 0.0096 

49306 Chlorothalonil F 0.035 

49305 Clopyralid H 0.013 

04031 Cycloate (ND) H 0.013 

49304 Dacthal mono-acid H, M 0.011 

04039 Deethyldeisopropylatrazine H, M 0.01 

04038 Deisopropylatrazine H, M 0.044 

38442 Dicamba H 0.012 

49302 Dichlorprop H 0.013 

49301 Dinoseb H 0.012 

04033 Diphenamid H 0.026 

49300 Diuron H 0.015 

49297 Fenuron (ND) H 0.031 

61694 Flumetsulam H 0.011 

38811 Fluometuron H 0.031 

50356 Imazaquin H 0.016 

50407 Imazethapyr H 0.017 

61695 Imidacloprid I 0.0068 

38478 Linuron (ND) H 0.014 

38482 MCPA H 0.016 

38487 MCPB (ND) H 0.015 

50359 Metalaxyl F 0.02 

38501 Methiocarb (ND) I, Ac, Mo 0.008 

49296 Methomyl I 0.0044 

61696 Methomyl oxime (ND) I 0.011 

61697 Metsulfuron-methyl H 0.025 

49294 Neburon H 0.012 

50364 Nicosulfuron H 0.013 

49293 Norflurazon (ND) H 0.016 

49292 Oryzalin H 0.017 

38866 Oxamyl (ND) I, N, Ac 0.012 

50410 Oxamyl oxime (ND) I, N, Ac 0.013 

49291 Picloram (ND) H 0.019 

49236 Propham (ND) H, PGR 0.0096 

50471 Propiconazole (ND) F 0.021 

38538 Propoxur I 0.008 

38548 Siduron H 0.016 

50337 Sulfometuron-methyl H 0.0088 

04032 Terbacil H 0.0098 

61159 Tribenuron-methyl (ND) H 0.0088 

49235 Triclopyr H 0.022 

Estimated Pesticide Use in the Study Area 13 
METHODS 

The data-collection methods used during this 

investigation conform to standard USGS protocols 

(Wilde and others, 1999). The analytical tools and 

reporting levels used to interpret the water-quality data 

in the Mobile River Basin are consistent with current 

water-quality standards and guidelines. 

Sampling Frequency 

Surface-water samples were collected in the 

Mobile River Basin from January 5, 1999, through 

December 20, 2001. Each surface-water sample was 

analyzed for nutrients, major ions, dissolved organic 

carbon, suspended organic carbon, and suspended 

sediment. Sampling for other constituents, such as 

pesticides, was less frequent (table 1) and varied 

annually, seasonally, and between sites, depending on 

the sampling objectives, the expected variability, and 

the resources available to conduct sampling at each 

site. Bogue Chitto Creek and Cahaba Valley Creek 

were sampled each week between March and October 

1999. Samples were collected twice each month at the 

Cahaba River between January and December 1999 

and at Cahaba Valley Creek between November 1999 

and April 2000. Otherwise, samples generally were 

collected monthly for a 2-year period or for the 

duration of the sampling period (3 years). 

Sample Collection 

The data-collection procedures used during this 

investigation included equal-width increment sampling 

(Shelton, 1994). Equal-width increment sampling 

produces a composite sample that is representative of 

flow in a cross section. Most surface-water samples 

were collected by using a DH-81 sampler (Edwards 

and Glysson, 1999). Samples from the Alabama River, 

Tombigbee River, and Black Warrior River were 

collected by using either the D-95 or the D-77 sampler 

(Edwards and Glysson, 1999). Storm samples were not 

flow-weighted composite samples taken at specific 

intervals, as described in the U.S. Environmental 

Protection Agency (USEPA) sampling guide (U.S. 

Environmental Protection Agency, 1992b); instead, the 

storm samples were discrete samples collected using 

equal-width increment sampling. Field measurements 

of stream discharge, air temperature, water 

temperature, pH, dissolved oxygen, and specific 

conductance were made at the time of sampling. 

A Teflon cone splitter and bottles were used to 

split the water samples into aliquots for analyses. After 

splitting, water samples for dissolved nutrients and 

major ions were filtered by using a 0.45-micron (μm) 

pore size filter that was pre-rinsed with deionized water 

and native streamwater. Samples for pesticide analyses 

were filtered by using a 0.7-μm pore size, baked, glassfiber filter. Nutrient, pesticide, and organic carbon 

samples were preserved and chilled immediately after 

filtration and shipped overnight to the USGS National 

Water Quality Laboratory (NWQL) in Denver, Colo. 

Suspended-sediment samples were shipped to the 

USGS sediment laboratory in Louisville, Ky. Pesticide 

samples were analyzed by using gas chromatography/ 

mass spectrometry (GC/MS; Zaugg and others, 1995) 

or by using high-performance liquid chromatography/ 

mass spectrometry (HPLC/MS; Furlong and others, 

2001). Equipment used to process organic carbon 

samples was cleaned with a 0.2-percent nonphosphate 

detergent and rinsed with pesticide-grade or volatileorganic-compound grade blank water obtained from 

the NWQL. All other equipment that was used to 

collect and process samples was cleaned with a 0.2-

percent nonphosphate detergent and rinsed with tap 

water and deionized water. Equipment was rinsed with 

a solution of 5-percent hydrochloric acid followed by 

deionized water for metals sampling. A rinse of 

pesticide-grade methanol was added when pesticides 

were sampled. 

Selection of Pesticide Analytes 

Pesticides were selected for analysis from a list 

of nearly 400 most commonly used pesticides in the 

United States (Gianessi and Puffer, 1990, 1992). The 

pesticides were prioritized according to the following 

factors: a national use of more than 8,000 pounds (lbs) 

of active ingredient per year, inclusion in the analytical 

schedules of other Federal monitoring or assessment 

programs, toxicity, leachability, and the ability to trap 

and extract the analyte from the appropriate solidphase concentration matrix (Gilliom and others, 1995). 

The final target analyte list (table 2) is a broad spectrum 

of pesticides that were analyzed by using either GC/MS 

(Zaugg and others, 1995) or HPLC/MS (Furlong and 

others, 2001). Most of the water samples analyzed by 

using HPLC/MS in 1999 exceeded the holding times 

for the method; consequently, the HPLC/MS data 

from 1999 were not included in this report. There 

were seven pesticides in common between the two 

14 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999– 2001 
methods: atrazine, carbaryl, carbofuran, deethylatrazine, linuron, tebuthiuron, and terbacil. The 

laboratory reporting level (LRL) for the HPLC/MS 

method generally was higher than the GC/MS method; 

therefore, the results sometimes were not identical 

between methods for these compounds. Forty-seven 

pesticides and metabolites were analyzed by using 

GC/MS, and 64 pesticides and metabolites were 

analyzed by using HPLC/MS. 

Data Analysis and Review 

Methods used to interpret water-quality results in 

this report include various graphical tools and statistical 

methods. Graphical tools include the use of bar charts, 

which illustrate the speciation of certain nutrients 

(nitrogen and phosphorus), monthly median 

concentrations (nutrients and pesticides), and the most 

frequently detected pesticides. Box plots display the 

variability in nutrient concentrations. 

The NWQL has implemented new procedures 

for interpreting and reporting low-concentration data in 

water-quality samples (Childress and others, 1999). 

Concentrations of analytes that either were not detected 

or were not identified are reported as less than (<) the 

LRL and are considered to be nondetections. Analytes 

that were detected at concentrations between the LRL 

and the long-term method detection level (LT-MDL), 

which usually is one-half the LRL, and that pass 

identification criteria were estimated. Estimated 

concentrations are noted with the remark code E. The 

uncertainty associated with the magnitude of estimated 

concentrations is greater than that associated with 

values that were not estimated (Martin and others, 

1999). The sample matrix and the instrument condition 

can limit the reliable measurement of an analyte in the 

laboratory. 

The NWQL specifies the minimum reporting 

level (MRL) and(or) LRL for organic compounds. 

Quality-control data are collected by the NWQL on a 

continuing basis to determine the MRLs, LT-MDLs, 

and LRLs; these values are re-evaluated each year and, 

consequently, may change from year to year. The LRLs 

for pesticides analyzed by using GC/MS were updated 

by the NWQL for water year1 2001 (table 2). The LRLs 

for pesticides analyzed by using HPLC/MS were those 

in effect on October 1, 2001 (table 2). 

1

 Water year is the period October 1 through September 30, and is 

identified by the year in which it ends. 

Sensitive analytical methods used in this study 

resulted in low detection limits for many pesticides. 

Comparison of detection frequencies among pesticides 

can be misleading because of the different detection 

limits associated with each of the pesticides. For 

example, atrazine has an LRL of 0.007 microgram per 

liter (μg/L) and prometon has an LRL of 0.015 μg/L. 

Atrazine was detected more frequently than prometon 

in this study; however, it is unknown whether that 

conclusion would hold true if the LRL of prometon also 

were 0.007 μg/L. Pesticide data are frequently adjusted 

by censoring to a common threshold, such as 0.01 μg/L 

(values less than 0.01 μg/L are not considered 

detections), to reduce this type of bias. In this 

report, however, uncensored data were used when 

calculating detection frequencies for pesticides in 

the Mobile River Basin and nationwide in the 

NAWQA Program. 

The USEPA and the Alabama Department of 

Environmental Management (ADEM) have waterquality standards and guidelines for some compounds 

that can have adverse effects on human health, aquatic 

organisms, and wildlife. Although the maximum 

contaminant levels (MCL) established by the USEPA 

and the ADEM pertain to finished drinking water 

supplied by a community water supply, these levels 

provide values for comparison with the sampled 

concentrations (Alabama Department of Environmental 

Management, 2000b; U.S. Environmental Protection 

Agency, 2000c, 2001). The USEPA also has developed 

guidelines for surface water that are intended to 

represent background concentrations of selected 

nutrients in individual ecoregions (U.S. Environmental 

Protection Agency, 2000a, 2000b). Aquatic-life criteria 

(U.S. Environmental Protection Agency, 1999; 

Alabama Department of Environmental Management, 

2000c) provide for the protection of aquatic organisms 

for short-term (acute) and long-term (chronic) 

exposures to chemical compounds. In some instances, 

Canadian guidelines were used for comparisons when 

other criteria were not available (International Joint 

Commission United States and Canada, 1978; 

Canadian Council of Ministers of the Environment, 

2001). 

The Kruskal-Wallis test and the Tukey multiplecomparison test were used to evaluate whether nutrient 

concentrations for each land-use category were 

significantly different or whether nutrient 

concentrations at one site were significantly different 

from nutrient concentrations at other sites (SAS 

Methods 15 
Institute, Inc., 1989). The Kruskal-Wallis test is a oneway nonparametric analysis of variance (ANOVA) that 

was used to determine whether significant differences 

existed between land-use categories. The Tukey 

multiple-comparison test was then used to compare the 

differences in concentrations between the individual 

sites. The simplest procedures for performing 

nonparametric multiple comparisons are rank 

transformation tests (Helsel and Hirsch, 1992). Ranks 

were substituted for the original data and the Tukey 

multiple-comparison test was performed on the ranks. 

Spearman’s rho was used to measure the strength 

of association between nutrient concentrations and 

streamflow. Spearman’s rho is the linear correlation 

coefficient computed on the ranks of the data (Helsel 

and Hirsch, 1992) and was computed based on the 

ranks of nutrient concentrations and streamflow. Values 

of rho range from -1.0 to 1.0 and the closer the value is 

to -1.0 or 1.0, the stronger the association between the 

two variables. 

Trends in concentrations of total nitrogen and 

phosphorus, total ammonia and organic nitrogen, and 

dissolved nitrate, phosphorus, and orthophosphate 

were analyzed for the period of record at each site 

through 2001. Because at least 5 years of record are 

required for statistical trend testing (Schertz and others, 

1991), data from only three of the nine sites were 

analyzed because these sites have periods of record 

prior to the period 1999–2001: the Cahaba River 

(1990–94), the Alabama River (1971–96), and the 

Tombigbee River (1975–96). Trends were analyzed for 

the entire period of record at each of these sites for 

long-term trends (decadal variations) and for 1988– 

2001 for short-term trends (annual variations). 

Trend analyses were performed on 

concentrations adjusted for streamflow using a 

statistical technique known as locally weighted 

scatterplot smoothing (LOWESS; Cleveland, 1979; 

Helsel and Hirsch, 1992). The LOWESS trend lines 

illustrate relations between concentrations and 

streamflow that are difficult to discern in a simple 

scatterplot. The LOWESS trend line is computed by 

fitting a weighted least-squares equation to the 

concentration and streamflow data (Helsel and Hirsch, 

1992). The smoothing technique used to calculate the 

LOWESS trend line is particularly useful because no 

assumptions regarding linearity of the data are 

required. The smoothing algorithm uses nearby data 

points to calculate a smoothed value for every data 

point. Each nearby data point is weighted so that the 

more distant points affect the smoothed value less than 

points that are close. A line is then drawn through the 

smoothed values. The number of nearby points used to 

calculate a smoothed value is controlled by the 

smoothness factor. A smoothness factor of 0.5 means 

that the closest 50 percent of all the data points were 

used to calculate each smoothed value. Residuals 

(differences between the LOWESS-fitted 

concentrations and measured concentrations) were 

computed and referred to as flow-adjusted nutrient 

concentrations. Changes in the flow-adjusted 

concentrations indicate changes in concentration over 

time that are independent of changes in streamflow. 

Time-series flow-adjusted concentration plots 

were tested by using the seasonal Kendall test to detect 

the presence of trends (Hirsch and others, 1982). The 

seasonal Kendall test can be used to detect long-term 

changes in concentration, which may indicate longterm improvement or deterioration in stream quality. 

The seasonal Kendall test is based on the 

nonparametric Kendall’s tau test (Kendall, 1975), 

which compares the relative values of all possible data 

values in a time series. In the seasonal Kendall test, 

comparisons between data values are restricted to pairs 

of data that are from the same time period annually; this 

period is defined as a season. 

The seasonal Kendall test also was used for 

testing a null hypothesis of no trend (the nutrient 

concentration and its date of observation are 

independent of one another). A statistically significant 

trend is indicated when the null hypothesis obtained 

from the seasonal Kendall test has a probability level 

(p-value) of 0.05 or less. For example, a p-value of 0.05 

means that there is a 5-percent chance of making an 

error when rejecting the null hypothesis. In this report, 

p-values less than or equal to 0.05 were considered 

statistically significant in indicating increasing or 

decreasing trends in nutrient concentrations. 

Annual and monthly instream loads of total 

nitrogen and total phosphorus were calculated as the 

product of daily streamflow and estimated daily 

concentration using Cohn’s ESTIMATOR model 

(Cohn and others, 1989; Gilroy and others, 1990; Cohn 

and others, 1992). This model includes a sevenparameter log-linear regression analysis of constituent 

concentrations against measured environmental 

variables: 

16 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999– 2001 
ln ( ) C = β – – 0 + β1[ln (Q Q')] + β2[ln (Q Q')]2 (1) 

+ β – – 3(t t') + β4 (t t')

2 

+ β5 sin (2πt) 

+ β6 cos (2πt) + ε , 

where 

ln = natural logarithm function, 

C = concentration (in milligrams per liter), 

Q = instantaneous discharge (in cubic feet per 

second), 

t = time (in decimal years),


sin = sine function,


cos = cosine function,


π = 3.14169, 

β0 to β6 = coefficients of the regression model, 

ε = model errors, 

Q' = centering variable defined so thatβ1 and β2 

are statistically independent, and 

t' = centering variable defined so thatβ3 and β4 

are statistically independent. 

The regression analysis assumes that model 

errors (ε) are independent and normally distributed, 

with zero mean and variance. The minimum variance 

unbiased estimator (MVUE; Bradu and Mundlak, 

1970) was included in the model to correct for the 

retransformation bias associated with log-linear 

regression models; the model also employs the adjusted 

maximum likelihood estimator (AMLE; Cohn, 1988), 

which statistically adjusts for censored data and 

multiple reporting limits. 

Equation 1 results in an estimate of the daily 

logarithmic constituent concentrations. The estimated 

daily constituent concentrations are then multiplied by 

the daily mean discharge to produce a daily mean load 

by using the following equation: 

Li ln [ ] = Q × ln [ ] × K , (2) i Ci

where 

ln = the natural logarithm function, 

Li = the daily mean load (in kilograms per day), 

i = any interval, 

Qi = the daily mean discharge for that interval 

(in cubic feet per second), 

Ci = the mean concentration (in milligrams per 

liter), and 

K = 0.203, the correction factor for unit conversion to tons per day. 

Yields, which allow for easy comparison among 

sites with different drainage areas, were computed by 

dividing the estimated load by the drainage area of the 

basin. 

Quality-Control Methods and Results 

Quality-assurance and quality-control measures 

were practiced throughout the study according to 

established USGS guidelines (Mueller and others, 

1997). Laboratory and field blank samples were 

processed by using water certified to contain 

undetectable concentrations of constituents to be 

analyzed. Data from blank samples were used to 

determine the extent of contamination introduced 

during sampling, sample processing, shipping, or 

laboratory analysis. Blank water used for the inorganic 

constituent sample was distilled, deionized water 

obtained from the USGS Ocala Water Quality Research 

Laboratory in Ocala, Fla. Blank water used for the 

organic constituent sample was either pesticide-grade 

or volatile-organic-compound-grade blank water 

obtained from the NWQL. 

Eighteen blank samples were analyzed for 

nutrients. Nitrogen species were detected in 10 of the 

blanks, and 4 of these detections were greater than the 

corresponding LRL. Concentrations of dissolved 

ammonia and dissolved ammonia plus organic nitrogen 

were detected in one blank sample each in amounts that 

exceeded the 75th percentile for environmental samples 

for these two constituents. All other nitrogen detections 

were lower than the 10th percentile of environmental 

samples. There were no detections of nitrite or nitrite 

plus nitrate in the blank samples. Phosphorus species 

were detected in four blank samples, and two of these 

detections were greater than the corresponding LRL. 

Two estimated detections of dissolved phosphorus 

were equal to or less than the 5th percentile for this 

constituent in all environmental samples. Orthophosphate and total phosphorus were detected 

once—concentrations were estimated and less than 

the corresponding LRL. 

Dissolved organic carbon was detected in 3 of 

18 blank samples—two of the detections were 

estimated and less than the LRL. All dissolved organic 

carbon detections were less than the minimum 

concentration for environmental samples. Suspended 

organic carbon was detected in 2 of 14 blank samples, 

and concentrations were equal to or less than the 

median concentration of this constituent in all 

environmental samples. Fourteen blank samples were 

Data Analysis and Review 17 
analyzed for pesticides using the GC/MS method, and 

7 additional blank samples were analyzed for 

pesticides using the HPLC/MS method. No pesticides 

were detected in any of the blank samples. 

Replicate samples were used to assess variability 

as a result of sample processing and laboratory 

analysis. The relative percentage difference (relative 

percentage difference = |A – B| / [(A + B)/2]) between 

the environmental samples and the corresponding 

replicate samples for nutrients ranged from 0 to 

147.3 percent, with a median of 1.6 percent. Replicate 

results for nutrients indicated good reproducibility (less 

than 10 percent difference) of the data in 83 percent of 

the detections (126 of 152 pairs). For dissolved organic 

carbon, the relative percentage difference ranged from 

0 to 51.1 percent, with a median of 2.7 percent, and 

good reproducibility in 67 percent of the detections 

(12 of 18 pairs). For suspended organic carbon, the 

relative percentage difference ranged from 0 to 

58.8 percent, with a median of 13.9 percent, and good 

reproducibility in 29 percent of the detections (4 of 

14 pairs). For pesticides, the relative percentage 

difference ranged from 0 to 118.6 percent, with a 

median of 7.2 percent. Replicate results from pesticides 

indicated good reproducibility of data in 53.8 percent 

of the detections (189 of 351 pairs; appendix 1). In 

approximately 11.4 percent of the pesticide detections 

(40 of 351 pairs), a compound was detected in one 

sample but not detected in the other (appendix 1). 

Recovery data were obtained from sets of fieldmatrix spikes and laboratory spikes. A spike set 

consisted of an environmental sample, a replicate, and 

two spiked replicates. Eleven samples were analyzed 

for field-matrix spikes using the GC/MS method; 

5 samples were analyzed for laboratory spikes using 

the HPLC/MS method. Water samples were collected, 

filtered, and spiked (if appropriate) prior to shipping to 

the NWQL for analysis. Field matrix spikes were 

added to the filtered pesticide sample while in the field; 

laboratory spikes were added to the filtered pesticide 

sample at the NWQL. The results for the spiked data 

are shown in figure 8. 

Most recoveries for the GC/MS method fell 

within the expected range of 60 to 140 percent; the 

median recovery was 103.5 percent (fig. 8A). Median 

recoveries of four compounds (carbaryl, carbofuran, 

methyl-azinphos, and terbacil) exceeded 140 percent. 

Median recoveries of two compounds (p,p '-DDE and 

cis-permethrin) were less than 60 percent. Five 

pesticides (carbaryl, carbofuran, deethylatrazine, 

methyl-azinphos, and terbacil) were identified in the 

GC/MS method development (Zaugg and others, 1995) 

as having highly variable recoveries and were reported 

as estimated regardless of concentration. Detections of 

these compounds were highly reliable, but the 

numerical concentrations associated with the 

detections were not reliable (Coupe, 2000). 

Nondetections of these five compounds were unreliable 

because the poor recovery results indicated a high 

potential for false nondetections (Coupe, 2000). Small 

recoveries of deethylatrazine occurred in all samplematrix types, and the results were reported as estimated 

(Zaugg and others, 1995). 

Most recoveries for the HPLC/MS method also 

fell within the range of 60 to 140 percent; the median 

recovery was 101.1 percent (fig. 8B). Median 

recoveries of six compounds (ethyl-chlorimuron, 

imazaquin, imazethapyr, imidacloprid, nicosulfuron, 

and methyl-sulfometuron) exceeded 140 percent; 

median recoveries of six compounds ranged between 

120 and 140 percent (flumetsulam, linuron, neburon, 

propham, propiconazole, and siduron); and median 

recoveries of nine compounds (aldicarb, aldicarb 

sulfone, 3-ketocarbofuran, clopyralid, methylchloramben, deethyldeisopropylatrazine, methomyl 

oxime, oxamyl oxime, and methyl-tribenuron) were 

less than 60 percent. 

The method development for the HPLC/MS 

method (Furlong and others, 2001) indicated that the 

HPLC/MS method had recoveries in organic-free water 

ranging from 28 to 175 percent, with elevated 

recoveries reflecting apparent matrix enhancement. 

Two statistics were used by the NWQL to determine if 

the reported concentration of any compound required 

qualification. Median recoveries calculated from longterm laboratory reagent spike (LRS) data were used to 

estimate the accuracy of concentrations. A 

nonparametric statistic, f-pseudosigma (Hoaglin, 1983) 

was calculated to determine the variation of LRS 

recoveries. The average median recovery for all 

compounds was 73.4 percent, and the average 

f-pseudosigma of recovery was 21.4 percent. Median 

recoveries had to fall within 60 to 120 percent for a 

compound to be considered reportable without 

qualification. In addition, the f-pseudosigma statistic 

had to be less than 25 percent for a compound to be 

reported without qualification. Nineteen compounds 

(2,4-DB, 3-ketocarbofuran, aldicarb, aldicarb sulfone, 

aldicarb sulfoxide, bentazon, bromoxynil, chloramben 

methyl ester, chlorothalonil, cycloate, flumetsulam, 

18 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999– 2001 
Data Analysis and Review 19 Figure 8A. Spike recoveries for pesticides and degradation products analyzed by the GC/MS method in surface-water samples from the Mob
20 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999 – 2001

Figure 8B. Spike recoveries for pesticides and degradation products analyzed by the HPLC/MS method in surface-water samples from the M
imazaquin, MCPB, methiocarb, methomyl, methomyl 

oxime, methyl-metsulfuron, oxamyl oxime, and 

methyl-tribenuron) were reported as estimated because 

recoveries were outside the acceptable range (median 

recovery less than 60 percent or greater than 

120 percent). Concentrations of eight compounds 

(2-hydroxyatrazine, bromacil, deethylatrazine, 

deethyldeisopropylatrazine, deisopropylatrazine, 

imazethapr, norflurazon, and terbacil) were reported as 

estimated because variation was outside the acceptable 

range (f-pseudosigma greater than 25 percent). The 

remaining 38 compounds met recovery performance 

criteria and were reported without qualification 

(Furlong and others, 2001). 

The data from the HPLC/MS method should be 

used with care and with the understanding that there 

likely will be more frequent detections at comparable 

or lower concentrations than the HPLC method of 

Werner and others (1996), given that HPLC/MS offers 

more specific detection in the presence of matrix 

interferences than does HPLC with ultraviolet 

detection (Furlong and others, 2001). 

Surrogate compounds were added to the samples 

at the NWQL. These surrogate compounds were not 

expected to be present in the environment but were 

expected to behave similarly to selected target analytes 

in the environment (Coupe, 2000). The GC/MS method 

called for the addition of two compounds— alphaHCH-d6, an organochlorine compound, and diazinond10, an organophosphorus compound. The HPLC/MS 

method called for the addition of three surrogates— 

barban, C-13 caffeine, and 2,4,5-T. These surrogates 

were used to assess the recoveries for the targeted 

analytes (fig. 9). The median overall recoveries for 

these compounds were 105, 102, 84, 68, and 

85 percent, respectively. For the GC/MS method, all of 

the recovery data were within the expected range of 

60 to 140 percent (fig. 9); for the HPLC/MS method, 

85 percent of the recovery data were within the 

expected range of 60 to 140 percent (fig. 9). 

Figure 9. Recoveries of surrogate compounds in surface-water samples from the Mobile 

River Basin. 

Data Analysis and Review 21 
NUTRIENTS 

Nutrients are chemical elements essential to 

plants and animals and include various forms of 

reduced or oxidized nitrogen, phosphorus, and organic 

carbon. Several species of nitrogen were measured 

during this study, including dissolved ammonia, nitrite, 

nitrite plus nitrate, organic nitrogen plus ammonia, and 

total ammonia plus organic nitrogen. Total nitrogen 

was computed as the sum of dissolved nitrite plus 

nitrate and total ammonia plus organic nitrogen. 

Organic nitrogen and nitrate usually are the 

predominant components of the total nitrogen 

concentration (appendix 2), because nitrite and 

ammonia generally are unstable in aerated waters 

(Hem, 1985). High levels of nitrate in drinking water 

have been linked to methemoglobinemia (blue baby 

syndrome) and also have been linked to certain types of 

cancer (Weyer and others, 2001). 

Phosphorus species analyzed during this study 

were dissolved phosphorus, orthophosphate, and total 

phosphorus. Dissolved phosphorus generally is 

unstable and usually converts to orthophosphate (Hem, 

1985). Eutrophication, the presence of excess nutrients, 

including phosphorus, can lead to nuisance plant 

growth and algal blooms, which in turn can cause 

reduced light penetration and dissolved oxygen levels, 

fouled water intakes, and taste and odor problems in 

drinking water. 

Organic carbon was analyzed as both suspended 

organic carbon and dissolved organic carbon. While 

organic carbon is a minor nutrient, it is a concern 

because of its interaction with other compounds. 

Dissolved organic carbon forms trihalomethane (THM) 

compounds, which are suspected carcinogens, when 

treated with chlorine to disinfect drinking-water 

Table 3. Nutrient criteria recommended by the U.S. Environmental 

[mg/L, milligrams per liter] 

supplies. Organic carbon also can increase the 

solubility of certain pesticides and the mobility and 

bioavailability of heavy metals, such as mercury. 

Several guidelines and standards have been 

established for nutrients in water (table 3). Current 

drinking-water standards, which are enforceable and 

apply to drinking-water supply systems, set maximum 

nitrite plus nitrate levels at 10 milligrams per liter 

(mg/L), maximum nitrate levels at 10 mg/L, and 

maximum nitrite levels at 1 mg/L (U.S. Environmental 

Protection Agency, 2002). The USEPA also has 

developed nutrient guidelines for surface water, which 

are intended to represent background concentrations of 

selected nutrients (U.S. Environmental Protection 

Agency, 2000a; 2000b). In order to account for regional 

and local influences, these guidelines are established 

for streams in individual ecoregions. Ecoregions are 

land divisions based on a combination of causal and 

integrative factors, including land use, land-surface 

form, potential natural vegetation, and soils (Omernik, 

1987). The Mobile River Basin includes parts of the 

Southern Coastal Plain, Southeastern Plains, 

Southwestern Appalachians, Ridge and Valley, 

Piedmont, and Blue Ridge Mountains ecoregions 

(Johnson and others, 2002). The ecoregion nutrient 

criteria are not intended to be enforceable standards but 

rather serve as guidelines for certain nutrient 

concentrations within the ecoregions. Nutrient species 

sampled during this study with applicable ecoregion 

criteria are total nitrogen, nitrite plus nitrate, total 

organic nitrogen plus ammonia (total Kjeldahl 

nitrogen), and total phosphorus. The USEPA also 

recommends that total phosphorus concentrations not 

exceed 0.10 mg/L in streams not entering lakes or 

impoundments in order to prevent nuisance aquatic 

Protection Agency for ecoregions in the Mobile River Basin 

Total Kjeldahl Nitrite plus Total Total 

Ecoregiona Site name nitrogen nitrate nitrogen phosphorus 

(mg/L) (mg/L) (mg/L) (mg/L) 

Ridge and Valley Chattooga River, Cahaba River, 0.3 0.095 0.214 0.01 

Cahaba Valley Creek 

Southwestern Appalachians Black Warrior River .1 .059 .3 .006 

Southeastern Plains Threemile Branch, Pintlalla Creek, .3 .095 .618 .0225 

Bogue Chitto Creek, Tombigbee 

River, Alabama River 

a

 U.S. Environmental Protection Agency (2000a; 2000b). 

22 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999– 2001 
plant growth (U.S. Environmental Protection Agency, 

1986). 

Nitrogen 

Nitrogen concentrations among the Mobile River 

Basin sites exhibited patterns associated with land use. 

Statistical descriptions of the concentration of nitrogen 

species are given by site in appendix 2. Total nitrogen 

concentrations ranged from 0.2 to 10 mg/L. Results of 

the Kruskal-Wallis test indicated that agricultural and 

urban indicator sites had significantly higher (p < 0.05) 

concentrations of total nitrogen than the integrator 

sites, which are composed of mixed land use (fig. 10). 

Additional analysis of the data using Tukey’s test 

shows six tiers of data groups shown on figure 10 as 

multiple comparison groups A, B, BC, C, CD, and D. 

Letters were assigned to each site based on statistically 

significant similarities. Sites with different letter 

designations were significantly different (p < 0.05), 

whereas sites with the same letter were considered to 

be similar (Helsel and Hirsch, 1992). Sites can have 

multiple letter designations meaning they were similar 

to other sites but the other sites were not necessarily 

similar to each other. For example, for total nitrogen, 

Threemile Branch (multiple comparison group B) was 

similar to the Black Warrior River (multiple 

comparison group BC), but the Black Warrior River 

was also similar to the Cahaba River, Chattooga River, 

and Tombigbee River. Bogue Chitto Creek, primarily a 

row-crop agricultural indicator watershed, had the 

highest maximum and median concentrations of total 

nitrogen. Pintlalla Creek, primarily a pasture and 

grazing agricultural indicator watershed, had lower 

concentrations of nitrogen, which may be a result of 

differences in agricultural practices. The median 

concentrations of total nitrogen at all sites, except 

Pintlalla Creek and the Alabama River, exceeded the 

nutrient criteria for the respective ecoregion. 

Nitrate concentrations showed a similar relation 

to land use as total nitrogen; however, values were 

significantly different (p < 0.05) for each land-use 

category. Nitrate concentrations ranged from 0.03 to 

7.94 mg/L. The highest median concentrations of 

nitrate were from the urban indicator sites, Cahaba 

Valley Creek and Threemile Branch; the highest 

maximum concentration of nitrate was from Bogue 

Chitto Creek (fig. 10). At Cahaba Valley Creek, an 

average of 81 percent of the total nitrogen 

concentrations consisted of nitrate nitrogen (fig. 11). 

Nitrate concentrations at Cahaba Valley Creek 

(multiple comparison group A) also were significantly 

higher (p < 0.05) than all other sites. The Black Warrior 

River had the highest median nitrate concentration of 

the integrator sites, which also was higher than the 

median concentrations at both agricultural indicator 

sites. At the Black Warrior River, an average of 

71 percent of the total nitrogen concentrations 

consisted of nitrate nitrogen (fig. 11). The upper part of 

the Black Warrior River Basin has some of the most 

concentrated poultry production in Alabama (Alabama 

Agricultural Statistics Service, 2002), and the lower 

part includes a large part of the Birmingham 

metropolitan area (fig. 3). Both of these factors may 

influence the nitrate concentrations at this site, as 

elevated nitrate levels are indicators of anthropogenic 

activities (U.S. Geological Survey, 1999). No samples 

had concentrations that exceeded the drinking-water 

standard of 10 mg/L for nitrate. Median nitrate 

concentrations exceeded the USEPA ecoregion criteria 

at all sites except Pintlalla Creek, Alabama River, and 

Tombigbee River (fig. 10). 

Organic nitrogen plus ammonia concentrations 

ranged from 0.05 to 3.2 mg/L for dissolved species and 

0.06 to 4.2 mg/L for total species and were significantly 

different (p < 0.05) among land-use categories. 

Concentrations of organic nitrogen plus ammonia, both 

dissolved and total, were highest at Bogue Chitto Creek 

and Pintlalla Creek, constituting 61 and 85 percent, 

respectively, of the total nitrogen concentrations. 

Organic nitrogen plus ammonia concentrations also 

were significantly higher (p < 0.05) at Bogue Chitto 

Creek (multiple comparison group A) than all other 

sites. Several samples at all sites exceeded the USEPA 

ecoregion nutrient criteria, and the median 

concentration of total organic nitrogen plus ammonia 

exceeded the ecoregion nutrient criteria at all sites 

except Threemile Branch (fig. 10). 

Increases in streamflow resulted in no change or 

only slight increases in total nitrogen concentrations at 

integrator sites (fig. 12). Spearman’s rho values for 

total nitrogen and streamflow ranged from 0.22 to 0.76. 

Cahaba Valley Creek was the only site where total 

nitrogen concentrations decreased as streamflow 

increased, which may indicate a point source for total 

nitrogen that is being diluted as streamflow increases 

(fig. 12). 

Seasonal variations in nitrogen concentration 

occurred in relation to site and species of nitrogen 

(fig. 11), and are related to streamflow and nutrient 

Nutrients 23 
Figure 10. Distribution of total nitrogen, nitrite plus nitrate, and total ammonia plus organic nitrogen concentrations at sites in the Mobile 

River Basin. 

24 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999 – 2001 
Figure 11. Monthly median concentrations of nitrite plus nitrate and ammonia plus organic nitrogen at sites in the Mobile River 

Basin. 

Nitrogen 25 
26 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999 – 2001

Figure 12. Relation between total nitrogen concentrations and streamflow at sites in the Mobile River Basin.
inputs including fertilizer application and outfalls. 

Nitrate values varied the most for the urban and 

agricultural indicator sites, reflecting the influences of 

both streamflow and fertilizer applications. Bogue 

Chitto Creek had higher values of nitrate during both 

periods of increased streamflow, late fall and winter, 

and during periods of fertilizer application, spring and 

summer. Cahaba Valley Creek had increased nitrate 

concentrations during the summer and fall months 

during periods of decreased streamflow. Nitrate 

concentrations in the Black Warrior River were higher 

during months with higher streamflow. Organic 

nitrogen plus ammonia concentrations remained fairly 

constant in all seasons at all sites. 

Phosphorus 

Phosphorus concentrations also were variable 

among the sites in the Mobile River Basin, with 

patterns associated more with land use than with 

physiography or natural setting. Statistical descriptions 

of the phosphorus species at each site are provided in 

appendix 2. Total phosphorus concentrations at all sites 

ranged from 0.008 to 2.22 mg/L. Results of the 

Kruskal-Wallis test indicated that the total phosphorus 

concentrations at the urban and agricultural indicator 

sites were significantly (p < 0.05) higher than the 

mixed land-use sites. Tukey’s multiple comparison test 

showed seven groups of data; multiple comparison 

groups A, AB, B, BC, C, CD, and D (fig. 13). Bogue 

Chitto Creek had the highest maximum concentration 

of total phosphorus and Cahaba Valley Creek had the 

highest median concentration of total phosphorus of 

the indicator sites, and both are in multiple comparison 

group A (fig. 13). The Chattooga River had the highest 

concentrations (maximum and median) of total 

phosphorus of the integrator sites and had magnitudes 

and ranges in concentrations similar to the highest 

indicator sites; Chattooga River is in multiple 

comparison group A. Phosphorus concentrations are of 

particular interest because the Chattooga River flows 

into Weiss Lake, which has eutrophication problems 

(Alabama Department of Environmental Management, 

2000a). The remaining sites were distributed among 

multiple comparison groups B, BC, C, CD, and D. 

Ecoregion nutrient criteria (table 3) for total 

phosphorus were exceeded at all sites in nearly all 

samples. Only two sites, Cahaba River and Chattooga 

River, had one sample each below the ecoregion 

nutrient criteria for total phosphorus. Forty-two percent 

of total phosphorus concentrations at all nine fixed sites 

exceeded the USEPA goal of 0.1 mg/L to prevent 

nuisance aquatic plant growth in streams (U.S. 

Environmental Protection Agency, 1986). Median total 

phosphorus concentrations at Bogue Chitto Creek, 

Cahaba Valley Creek, and the Chattooga River 

exceeded this goal. 

Dissolved phosphorus ranged from 0.004 to 

0.54 mg/L and dissolved orthophosphate 

concentrations ranged from 0.01 to 0.43 mg/L. The 

highest maximum and median concentrations for both 

dissolved phosphorus and orthophosphate were at the 

Chattooga River. The range and magnitude of 

concentrations at the Chattooga River were similar to 

those at Cahaba Valley Creek, an urban indicator site, 

and both sites are in multiple comparison group A 

(fig. 13). While the predominant land use in the 

Chattooga River Basin is forested, the similarity of 

phosphorus concentrations to those in the Cahaba 

Valley Creek Basin may indicate that other land uses or 

sources may influence phosphorus concentrations in 

the Chattooga River Basin. An average of 99 percent of 

the total phosphorus concentrations in the Chattooga 

River Basin consisted of dissolved phosphorus and 

orthophosphate; an average of 81 percent of the total 

phosphorus concentrations at Cahaba Valley Creek 

consisted of dissolved phosphorus and orthophosphate 

(fig. 14). 

Total phosphorus concentrations at the Mobile 

River Basin sites generally increased as streamflow 

increased (fig. 15). This association is related to the 

affinity of phosphorus to bind to sediment. Correlation 

coefficients for total phosphorus and streamflow 

ranged from -0.85 at the Chattooga River to 0.22 at 

Pintlalla Creek. The urban indicator sites had 

distinctly different patterns from each other in 

that a positive correlation of orthophosphate with 

streamflow occurred at Threemile Branch (Spearman’s 

Rho = 0.50), and a negative correlation of orthophosphate with streamflow occurred at Cahaba Valley 

Creek (Spearman’s Rho = -0.58). 

The distribution of monthly medians (fig. 14) 

indicates that most sites had relatively constant 

concentrations of all species of phosphorus in all 

months. Cahaba Valley Creek and Chattooga River had 

lower median concentrations of phosphorus during 

higher streamflow periods, January through May, with 

higher median concentrations during the remainder of 

the year. Bogue Chitto Creek had higher median 

phosphorus concentrations during periods of fertilizer 

Phosphorus 27 
Figure 13. Distribution of dissolved phosphorus, orthophosphate, and total phosphorus concentrations at sites in the Mobile River Basin. 

28 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999 – 2001 
Figure 14. Monthly median concentrations of suspended phosphorus and dissolved phosphorus at sites in the Mobile River Basin. 

Phosphorus 29 
30 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999 – 2001

Figure 15. Relation between total phosphorus concentrations and streamflow at sites in the Mobile River Basin.
application, late spring and summer, and in late fall 

when streamflow increases. The decrease in 

phosphorus concentrations at Bogue Chitto in late 

summer may be attributed to the lack of streamflow and 

the lack of samples collected because of the ephemeral 

nature of the stream. The median phosphorus 

concentrations for Pintlalla Creek during August were 

much higher than normal because of a storm sample 

collected on August 25, 1999. The creek was dry in 

July and August 2000; therefore, the median values for 

July and August were equal to the July and August 

1999 sample concentrations. It is likely that the 

monthly median concentrations for August would be 

similar to the phosphorus concentrations during the 

other summer months. 

Organic Carbon 

Dissolved organic carbon concentrations ranged 

from 0.9 to 17.8 mg/L and suspended organic carbon 

concentrations ranged from 0.2 to 6.0 mg/L. Median 

concentrations of dissolved organic carbon were 

highest at Bogue Chitto Creek and Pintlalla Creek 

(fig. 16). Results of the Kruskal-Wallis test show a 

significant difference in dissolved organic carbon 

concentrations between land-use groups. Results from 

Tukey’s multiple comparison test show five tiers of 

multiple comparison groups: A, B, C, CD, and D 

(fig. 16). In the Bogue Chitto Creek Basin, land use 

primarily is row crops and pastureland; in the Pintlalla 

Creek Basin, land use primarily is forested, with some 

row crops and pastureland. The drainage basins of both 

sites are underlain primarily by chalk. The elevated 

concentrations of dissolved organic carbon in these 

basins may be more indicative of natural environmental 

influences than the agricultural practices in the two 

basins. Suspended organic carbon concentrations were 

significantly different (p < 0.05) among land-use 

groups. Tukey’s multiple comparison test showed a 

slightly different pattern for dissolved organic carbon, 

resulting in multiple comparison groups A, B, BC, and 

C. Bogue Chitto Creek had significantly higher 

suspended organic carbon concentrations than all other 

sites (fig. 16). 

Loads and Yields of Nutrients 

Mean annual instream loads were calculated for 

each of the sites for total nitrogen, nitrate, total 

phosphorus, and dissolved orthophosphate. Results of 

these calculations and a summary of regression 

coefficients are shown in table 4. Analyses of instream 

loads can provide insight into the relative influence of 

seasons, temporal trends, and point and nonpoint 

sources on nutrient loads (Journey and Gill, 2001). 

Instream loads also can provide a means for comparing 

nutrients at sites with different drainage basin sizes or 

streamflow magnitudes by calculating yields and flowweighted concentrations. 

The ESTIMATOR model provides several 

diagnostic statistics for each constituent’s load 

regression including the coefficient of determination 

(R2), the variance (s), model variables, and the 

regression model coefficients (β0– β6). The R2 values 

indicate how well the regression model explains 

variability in the estimated concentration and are 

expressed as a percentage of the variation. For 

example, an R2 of 0.80 indicates that 80 percent of the 

variability is accounted for in the model. In general, 

higher R2

 values are more desirable, but no load 

regressions were excluded because of low R2 values. 

The ESTIMATOR model also provides T values for 

each regression coefficient, which is a measure of the 

significance of the coefficients in the regression model 

(Cohn and others, 1992). Regression coefficients with 

T values greater than 2 were considered to be 

statistically significant (Journey and Gill, 2001) and are 

shown in bold in table 4. Variables that are considered 

to be statistically significant indicate a relation to a 

constituent’s concentration. Streamflow is considered 

to be a good predictor of concentration when the 

coefficient β1 is statistically significant. Seasonal 

influences or variation are indicated by a statistically 

significant sine or cosine coefficient, β5 and β6, 

because they both represent seasonal influences—if 

either variable was statistically significant, then they 

were both considered to be significant. 

Point sources are likely to be the dominant 

nutrient input source at sites with statistically 

significant negative streamflow coefficients, β1, 

whereas sites with statistically significant positive 

streamflow coefficients have nonpoint sources as the 

dominant nutrient input source. Sites with significant 

negative streamflow coefficients were the Chattooga 

River (orthophosphate), Threemile Branch (nitrate), 

and Cahaba Valley Creek (total nitrogen, nitrate, 

orthophosphate) (table 4). Sites with significant 

positive streamflow coefficients were the Tombigbee 

River (total phosphorus), Alabama River (total 

nitrogen, nitrate, total phosphorus), Cahaba River (total 

Loads and Yields of Nutrients 31 
Figure 16. Distribution of dissolved and suspended organic carbon concentrations at sites in the Mobile River Basin. 

32 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999 – 2001

Table 4. Regression summary for the seven-parameter, log-linear regression model used to estimate nutrient concentrations at sites in the Mobile 

[s, standard deviation of the residuals from ordinary least-squares fit, in log units; R2, coefficient of determination; B0, constant; B1, coefficient of natural logarithm o

rithm of streamflow, squared; B3, coefficient of time; B4, coefficient of time, squared; B5, coefficient of sine (time); B6, coefficient of cosine (time); bold indicates coef

2, which indicates statistical significance; —, no regression results because of insufficient data] 

Constituent s R2 β0 β1 β2 β3 β4 β5 β6 

Annual nutri

in tons pe

1999 2000 

Alabama River at Claiborne, Alabama 

Total nitrogen 0.12 0.52 -0.5214 0.0682 -0.0087 0.0027 -0.0136 0.0603 0.0365 2,550 1,69Dissolved nitrite- .36 .67 -1.8380 .2411 -.1937 -.0690 .0689 .3490 .3279 848 43

plus-nitrate nitrogen 

Total phosphorus .20 .56 -2.607 .1786 .1071 -.0492 -.0397 -.0213 .0242 368 23Dissolved .45 .24 -4.213 -.1488 .0546 -.1821 -.0475 -.0395 .1081 80 5

orthophosphate 

Suspended sediment .46 .81 3.225 .7934 -.0393 .1038 .1584 .116 -.1806 184,000 94,60

Black Warrior River below Bankhead Lock and Dam near Bessemer, Alabama 

Total nitrogen 0.20 0.79 -0.5028 0.0126 0.0042 0.0197 0.1387 0.3157 0.2329 1,390 1,30Dissolved nitrite- .49 .74 -.7663 -.0002 -.0011 -.1274 .0741 .7576 .5863 1,130 81

plus-nitrate nitrogen 

Total phosphorus .40 .59 -4.9088 .0366 .0245 .0834 -.0444 -.0999 .3333 71 9Dissolved — — — — — — — — — — — 

orthophosphate 

Suspended sediment .69 .36 1.1439 .0502 .0454 -.4065 .4314 .2130 .1341 11,700 11,80

Loads and Yields of Nutrients 33 
Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999 – 2001 Table 4. Regression summary for the seven-parameter, log-linear regression model used to estimate nutrient concentrations at sites in the Mobile 

[s, standard deviation of the residuals from ordinary least-squares fit, in log units; R2, coefficient of determination; 

B0, constant; 

B1, coefficient of natural logarithm o

rithm of streamflow, squared; 

B3, coefficient of time; 

B4, coefficient of time, squared; 

B5, coefficient of sine (time); 

B6, coefficient of cosine (time); bold indicates coef

2, which indicates statistical significance; —, no regression results because of insufficient data] 

Constituent s R2 β0 β1 β2 β3 β4 β5 β6 

Annual nutri

in tons pe

1999 2000 

Bogue Chitto Creek near Memphis, Alabama 

Total nitrogen 0.62 0.35 0.9518 0.1169 0.0050 -0.0190 -0.0723 -0.4359 -0.2017 57 2Dissolved nitrite- 2.10 .31 -1.9861 .3641 .0077 -.3386 .0620 -.1863 .3295 194 6

plus-nitrate nitrogen 

Total phosphorus .54 .72 -2.2521 .1931 .0287 -.0987 -.1806 -.0637 .0037 14 Dissolved .98 .58 -4.4214 .2873 .0142 -.4216 .1330 -.4553 .3913 4.8 

orthophosphate 

Suspended sediment .96 .71 3.1245 .3349 .0426 .0194 -.4499 .0155 .0137 11,300 14,60

Cahaba River at Centreville, Alabama 

Total nitrogen 0.29 0.51 -0.2163 0.2305 -0.0378 0.2711 0.0455 -0.0794 0.0029 184 17Dissolved nitrite- .67 .46 -0.7924 .1496 -.2078 .1463 .1332 -.0379 .3675 116 7

plus-nitrate nitrogen 

Total phosphorus .55 .56 -2.5746 .5435 -.0315 .3090 .3709 -.3649 .0515 27 2Dissolved .59 .49 -3.6079 .0697 -.2296 .1505 .3674 -.1204 .2821 7 

orthophosphate 

Suspended sediment .62 .79 3.5701 1.0095 -.0194 .3520 -.1383 -.3049 -.3592 16,500 31,30

34 
Table 4. Regression summary for the seven-parameter, log-linear regression model used to estimate nutrient concentrations at sites in the Mobile 

[s, standard deviation of the residuals from ordinary least-squares fit, in log units; R2, coefficient of determination; B0, constant; B1, coefficient of natural logarithm o

rithm of streamflow, squared; B3, coefficient of time; B4, coefficient of time, squared; B5, coefficient of sine (time); B6, coefficient of cosine (time); bold indicates coef

2, which indicates statistical significance; —, no regression results because of insufficient data] 

Constituent s R2 β0 β1 β2 β3 β4 β5 β6 

Annual nutri

in tons pe

1999 2000 

Cahaba Valley Creek at Cross Creek Road at Pelham, Alabama 

Total nitrogen 0.36 0.49 0.3502 -0.2265 0.0329 0.0631 -0.1170 -0.0218 -0.0440 8 Dissolved nitrite- .34 .77 -.1567 -.501 .0193 .1063 -.0675 .0453 -.0123 5.2 

plus-nitrate nitrogen 

Total phosphorus .44 .55 -1.7401 -.0706 .0481 -.2159 -.471 -.2316 -.0445 .9 Dissolved .50 .75 -2.5645 -.5323 .0276 -.28 -.4989 -.0819 .0852 .5 

orthophosphate 

Suspended sediment .68 .64 3.3777 .9537 -.0455 -.0746 -.1086 -.6077 -.3410 293 49

Chattooga River above Gaylesville, Alabama 

Total nitrogen 0.21 0.36 -0.1388 0.1005 -0.0919 0.1675 0.0308 -0.0679 -0.1112 68 5Dissolved nitrite- .42 .47 -1.0541 -.0591 -.1227 .1718 .3699 .3036 -.2369 38 2

plus-nitrate nitrogen 

Total phosphorus .75 .50 -1.9321 .0982 -.0276 -.2094 -.1434 -1.0236 .1281 23 1Dissolved .32 .90 -1.9897 -.5542 -.0374 -.0933 -.3588 -.3617 .0335 11 

orthophosphate 

Suspended sediment .59 .68 3.9187 .9545 -.3282 .3565 -.8726 -.7031 -.3333 2,110 2,06

Loads and Yields of Nutrients 35 
Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999 – 2001 Table 4. Regression summary for the seven-parameter, log-linear regression model used to estimate nutrient concentrations at sites in the Mobile 

[s, standard deviation of the residuals from ordinary least-squares fit, in log units; R2, coefficient of determination; 

B0, constant; 

B1, coefficient of natural logarithm o

rithm of streamflow, squared; 

B3, coefficient of time; 

B4, coefficient of time, squared; 

B5, coefficient of sine (time); 

B6, coefficient of cosine (time); bold indicates coef

2, which indicates statistical significance; —, no regression results because of insufficient data] 

Constituent s R2 β0 β1 β2 β3 β4 β5 β6 

Annual nutri

in tons pe

1999 2000 

Pintlalla Creek at Liberty Church Road near Pintlalla, Alabama 

Total nitrogen — — — — — — — — — — — Dissolved nitrite- — — — — — — — — — — — 

plus-nitrate nitrogen 

Total phosphorus 0.44 0.55 -2.0187 0.1970 0.0045 0.1458 -0.2824 -0.5120 -0.1353 1.4 Dissolved — — — — — — — — — — — 

orthophosphate 

Suspended sediment .51 .72 2.8225 0.2557 0.0107 -0.3743 -0.5202 0.2045 -0.1057 360 28

Threemile Branch at North Boulevard at Montgomery, Alabama 

Total nitrogen 0.31 0.52 0.3021 0.1201 -0.0745 -0.0309 -0.0024 0.0874 0.2709 2.7 Dissolved nitrite- .44 .54 -0.6907 -0.2387 -0.0927 -0.2293 0.1952 0.0905 0.2927 1.2 

plus-nitrate nitrogen 

Total phosphorus .75 .57 -1.9639 0.6709 -0.125 0.2183 -0.1788 -0.2334 -0.1308 .33 Dissolved — — — — — — — — — — — 

orthophosphate 

Suspended sediment 1.10 .63 3.2539 1.0873 -0.0711 0.4911 -0.1328 -0.1882 0.2899 141 18

36 
Table 4. Regression summary for the seven-parameter, log-linear regression model used to estimate nutrient concentrations at sites in the Mobile 

[s, standard deviation of the residuals from ordinary least-squares fit, in log units; R2, coefficient of determination; B0, constant; B1, coefficient of natural logarithm o

rithm of streamflow, squared; B3, coefficient of time; B4, coefficient of time, squared; B5, coefficient of sine (time); B6, coefficient of cosine (time); bold indicates coef

2, which indicates statistical significance; —, no regression results because of insufficient data] 

Constituent s R2 β0 β1 β2 β3 β4 β5 β6 

Annual nutri

in tons pe

1999 2000 

Tombigbee River below Coffeeville Lock and Dam near Coffeeville, Alabama 

Total nitrogen 0.34 0.51 -0.3761 0.0370 -0.0317 -0.0709 0.1501 0.2689 0.0435 5,250 2,56Dissolved nitrite- .48 .63 -1.2628 .0975 -.1489 -.0628 .0445 .3604 .2236 1,730 97

plus-nitrate nitrogen 

Total phosphorus .32 .65 -2.5005 .2363 .0802 -.0227 -.0638 -.0043 .1057 660 43Dissolved .53 .20 -3.9985 -.0718 -.0471 -.0840 -.1250 -.0998 .2356 71 5

orthophosphate 

Suspended sediment .61 .77 3.6137 .7695 .1087 .0955 -.1880 -.2630 -.0374 505,000 459,00

Loads and Yields of Nutrients 37 
nitrogen), Bogue Chitto Creek (total nitrogen, nitrate, 

total phosphorus, orthophosphate), Pintlalla Creek 

(total phosphorus), and Threemile Branch (total 

nitrogen, total phosphorus). 

Nutrient yields are useful for comparing nutrient 

loads from sites with different drainage basin sizes. 

Normalizing the nutrient load to basin size eliminates 

the effect of basin size. For example, the Tombigbee 

River had a mean annual nitrogen load of 4,610 tons 

per day (tons/d), and Bogue Chitto Creek had a mean 

annual total nitrogen load of 64 tons/d (table 4); 

however, the yield for the Tombigbee River and Bogue 

Chitto Creek was 0.25 tons per day per square mile 

([tons/d]/mi2) and 1.2 (tons/d)/mi2, respectively, 

indicating higher total nitrogen inputs per square mile 

in the Bogue Chitto Creek Basin. Total nitrogen yields 

at Bogue Chitto Creek were almost five times higher 

than at the Tombigbee River, and Bogue Chitto Creek 

had the highest yields for all constituents for all sites. 

Nutrient yields were nearly twice as high in the 

Tombigbee River compared to the Alabama River for 

total nitrogen, nitrate, and total phosphorus, reflecting 

more agricultural and urban influences in the 

Tombigbee River Basin (table 4). Nutrient yields in 

Bogue Chitto Creek were higher than the other 

indicator sites. Nutrient yields were highest in Bogue 

Chitto Creek, Cahaba Valley Creek, and Threemile 

Branch due to the agricultural and urban land-use 

influences in those watersheds. 

Flow-weighted mean concentrations also are 

helpful in comparing nutrient loads from sites with 

differing streamflow regimes by eliminating the 

influence of streamflow. Flow-weighted mean 

concentrations were computed by dividing the 

estimated annual load by the mean annual streamflow 

for the load computation period. Clark and others 

(2000) calculated flow-weighted mean concentrations 

for selected nutrients in undeveloped basins around the 

United States to estimate background nutrient levels. 

Flow-weighted mean concentrations for the nine 

Mobile River Basin sites equaled or exceeded median 

flow-weighted means representing background 

concentrations of 0.02 mg/L of ammonia, 0.087 mg/L 

of nitrate, 0.26 mg/L of total nitrogen, 0.01 mg/L of 

orthophosphate, and 0.022 mg/L of total phosphorus 

(table 5). 

Flow-weighted mean concentrations also were 

computed for ammonia, nitrate, total nitrogen, 

orthophosphate, and total phosphorus for all NAWQA 

Study Units, including the Mobile River Basin Study 

Unit, from the period 1999 to 2001, and sites from this 

study unit were ranked against these values according 

to land-use category (table 5). Flow-weighted mean 

concentrations for the Mobile River Basin sites 

generally were in the lower to middle percentile ranges 

compared to data from other NAWQA studies across 

the Nation. However, Bogue Chitto Creek’s flowweighted mean concentrations of ammonia, total 

Table 5. Flow-weighted mean nutrient concentrations at sites in the Mobile River Basin 

[ft3/s, cubic feet per second; mg/L, milligrams per liter; —, not estimated] 

Total Ortho- Total Ammonia Nitrate nitrogen phosphate phosphorus 

Mean


Land-use annual
 Site name Years category streamflow


(ft3

/s)


Flow-weighted mean 

concentration (mg/L)

Percentile

Flow-weighted mean 

concentration (mg/L)

Percentile

Flow-weighted mean 

concentration (mg/L)

Percentile

Flow-weighted mean 

concentration (mg/L)

Percentile

Flow-weighted mean 

concentration (mg/L)

Percentile 

Alabama River Mixed 2 21,549 — — 0.16 22 0.62 25 0.02 33 0.09 40 

Black Warrior River Mixed 2 5,933 — — .74 53 1.41 52 — — .80 94 

Bogue Chitto Creek Agriculture 2 45 0.21 90 .14 19 4.19 83 .14 82 1.07 95 

Cahaba River Mixed 2 1,160 — — .45 42 1.11 43 .03 49 .21 65 

Cahaba Valley Creek Urban 2 33 .03 40 .83 56 1.42 52 .03 49 .14 53 

Chattooga River Mixed 2 380 — — .61 48 .88 36 .08 70 .14 52 

Pintlalla Creek Agriculture 2 53 — — — — — — — — .15 53 

Threemile Branch Urban 2 9 — — .41 38 1.31 51 — — .22 65 

Tombigbee River Mixed 2 21,133 .03 39 .31 34 .85 34 .02 33 .14 52 

38 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999– 2001 
nitrogen, orthophosphate, and total phosphorus were in 

the upper 20th percentiles of agricultural sites. The 

Chattooga River’s orthophosphate concentration 

ranked in the 70th percentile, and the Black Warrior 

River’s total phosphorus concentration was in the 94th 

percentile of integrator sites. 

Trends 

No significant long-term trends were detected to 

be statistically significant for the Alabama, Cahaba, or 

Tombigbee Rivers except for a general decrease in 

nitrate at the Alabama River (figs. 17, 18). The 

decrease in nitrate could be due to improved 

wastewater-treatment practices as well as decreases in 

the amount of row-crop agricultural activities in the 

watershed (Alabama Agricultural Statistics Service, 

2002). No short-term trends were detected at any of the 

three sites. 

An examination of time-series plots of the flowadjusted concentrations for the Alabama and 

Tombigbee Rivers indicated a general pattern of 

increases in total nitrogen and total ammonia and 

organic nitrogen from the mid-1970’s to the mid1980’s followed by slight decreases or very little 

change from the mid-1980’s to 2001 (fig. 17). The 

time-series plots also indicated that nitrate 

concentrations generally decreased from 1980 to 2001 

at both sites. Total phosphorus remained unchanged or 

decreased slightly from the early 1970’s to the mid1980’s followed by slight increases from the late 

1980’s to 2001, although no trends were detected to be 

statistically significant (fig. 18). A similar pattern was 

observed for dissolved phosphorus at both sites, but no 

trends were detected to be statistically significant. The 

presence of trends at the Cahaba River proved to be 

inconclusive because the analyses consisted primarily 

of comparing two clusters of data to each other 

(figs. 17, 18). 

SUSPENDED SEDIMENT 

Suspended sediment is all particulate matter 

suspended in the water column resulting from 

streambed resuspension and erosion (Guy and Norman, 

1970). Suspended sediment is measured as total 

concentration in milligrams per liter and as the 

percentage of total material finer than 0.062 millimeters (mm) (appendix 2). Natural conditions and 

anthropogenic activities can influence suspendedsediment concentration. Natural conditions 

contributing to increased sediment concentrations 

include steep terrain, areas burned by forest fires, and 

soil erosion. Anthropogenic activities that impact 

sediment concentrations include activities such as 

construction, mining, and timber harvesting. High 

suspended-sediment concentrations can cause habitat 

destruction, reduced light penetration in the water 

column, loss of reservoir storage, and increased 

concentrations of hydrophobic compounds that 

commonly bind to sediment. 

Suspended-sediment concentrations ranged from 

1.0 to 2,450 mg/L and were significantly different 

(p < 0.05) among land-use categories. Multiple 

comparison tests resulted in four tiers of groups—A, 

AB, B, and C (fig. 19). Bogue Chitto Creek had the 

highest maximum and median concentrations of 

suspended sediment. The median value of percent 

sediment finer than 0.062 mm was 88 percent for all 

sites, indicating the majority of suspended sediment 

was finer than sand-sized particles. 

Suspended Sediment 39 
40 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999 – 2001

Figure 17. Trends in flow-adjusted total nitrogen, total ammonia and organic nitrogen, and dissolved nitrate concentrations for the Alabama, 

Tombigbee, and Cahaba River Basins.
Suspended Sediment 41

Figure 18. Trends in flow-adjusted total phosphorus, dissolved phosphorus, and dissolved orthophosphate concentrations for the Alabama, 

Tombigbee, and Cahaba River Basins.
Figure 19. Distribution of suspended-sediment concentrations at sites in the Mobile River Basin. 

 Concentrations of suspended sediment 

were closely related to streamflow (fig. 20). 

Sediment concentrations had a significant (p < 0.05) 

positive correlation as streamflow increased for all 

sites and Spearman’s rho values ranged from 0.47 to 

0.81. 

Loads and Yields of Suspended Sediment 

Mean annual instream sediment loads and yields 

were calculated for each site in the Mobile River Basin 

(table 4). Mean annual sediment loads ranged from 

685,000 tons/d at the Tombigbee River to 163 tons/d at 

Threemile Branch. Significant regression coefficients 

can suggest possible insight into sources and influences 

of sediment loads. A significant positive streamflow 

coefficient indicates that sediment inputs were from 

nonpoint sources for all sites except the Black Warrior 

River and Chattooga River (table 4). However, the lack 

of a significant positive streamflow coefficient does not 

imply that there is a point source of sediment at these 

two sites. Suspended-sediment loads were significantly 

influenced by seasonal variations at the Chattooga 

River, Cahaba River, and Cahaba Valley Creek. 

Yields of suspended sediment ranged from 

3 (tons/d)/mi2

 at the Black Warrior River to 

298 (tons/d)/mi2 at Bogue Chitto Creek (table 4). 

Suspended-sediment yields at Pintlalla Creek were 

significantly lower than Bogue Chitto Creek, which 

may be a reflection of the differences in agricultural 

practices in the Pintlalla Creek Basin, which is 

predominantly pasture and forestland, compared to the 

Bogue Chitto Creek Basin, which is predominantly row 

crops. The relatively low suspended-sediment yield for 

the Black Warrior River reflects the influence of 

impoundments upstream from the site. 

42 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999– 2001 
Suspended Sediment 43 Figure 20. Relation between suspended-sediment concentrations and streamflow at sites in the Mobile River Basin.
PESTICIDES 

From January 1999 through December 2001, a 

total of 234 surface-water samples were collected at 

nine sites in the Mobile River Basin and analyzed for 

104 pesticides and degradation products. Of the 104 

compounds, 69 were detected in one or more stream 

samples (table 2). Of the 69 detected pesticides, 

51 were herbicides, 15 were insecticides, and 3 were 

fungicides (table 2). Atrazine, simazine, metolachlor, 

tebuthiuron, prometon, diuron, and 2,4-D were the 

most frequently detected herbicides in the Mobile 

River Basin. Diazinon, chlorpyrifos, and carbaryl were 

the most frequently detected insecticides; metalaxyl 

was the most frequently detected fungicide in the 

Mobile River Basin. 

Statistical summaries of pesticide concentrations 

are shown by site in appendix 3. The majority of 

pesticides used for agricultural purposes in the Mobile 

River Basin are applied seasonally, and higher 

concentrations of pesticides often are related to 

rainfall-runoff events. In order to better define the 

occurrence of the pesticides in the streams, sampling 

was concentrated during storms and during the spring 

and summer. Therefore, the statistics shown in 

appendix 3 may not be representative of ambient 

conditions or commonly occurring conditions during 

other seasons because sampling was more frequent 

during these other periods. Median monthly total 

pesticide concentrations at six sites are shown in 

figure 21. Concentrations of the most frequently 

detected herbicides and insecticides are delineated 

individually; the rest are grouped together in the 

category “other.” Streamflow and selected pesticide 

concentrations (atrazine, simazine, and metolachlor) at 

six of the study sites for the 1999–2001 sampling 

period are shown in figures 22–24, respectively. 

A relatively small number of herbicides 

accounted for most of the pesticide detections in the 

Mobile River Basin. These herbicides included 

atrazine and its metabolites (deethylatrazine, 

2-hydroxyatrazine, deisopropylatrazine, and 

deethyldeisopropylatrazine), simazine, metolachlor, 

tebuthiuron, prometon, diuron, and 2,4-D. Atrazine 

was detected in nearly 99 percent of the surface-water 

samples. Atrazine is used primarily as a preemergent 

herbicide on corn in agricultural areas and on lawns and 

golf courses in urban areas. Simazine, tebuthiuron, and 

prometon are used in urban areas for weed control 

along roadways and railways, along fences, and in 

other public areas (Hoffman and others, 2000). Diuron 

and simazine are used to control broadleaf weeds and 

grasses in peach and pecan orchards and vineyards; 

2,4-D is used as a postemergent herbicide to control 

broadleaf weeds in pastures, small grains, and forage 

crops (Alabama Cooperative Extension System, 1998). 

Metolachlor frequently is used as a preemergent 

herbicide on peanuts, soybeans, corn, and some 

vegetables (Alabama Cooperative Extension System, 

1998). 

Water-quality standards and guidelines have 

been developed for many pesticides to protect human 

health and aquatic life. Thirty-four of the pesticides 

detected in this study have recommended maximum 

concentration levels established by the USEPA (U.S. 

Environmental Protection Agency, 1999, 2000c, 2001); 

the ADEM (Alabama Department of Environmental 

Management, 2000b, 2000c); the International Joint 

Commission United States and Canada (1978); or the 

Canadian Council of Ministers of the Environment 

(2001; table 6). Thirty-two of the pesticides detected in 

this study have drinking-water standards, guidelines, or 

health advisories (table 6). The advisory levels were 

exceeded in concentrations of four herbicides 

(2,4-D, atrazine, cyanazine, and simazine), three 

insecticides (alpha-HCH, diazinon, and dieldrin), and 

one fungicide (chlorothalonil; table 6). Aquatic-life 

criteria have been established for 23 of the 

70 pesticides detected in this study (table 6). These 

criteria were exceeded in concentrations of five 

herbicides (2,4-D, atrazine, cyanazine, diuron, and 

metolachlor), six insecticides (carbaryl, chlorpyrifos, 

diazinon, dieldrin, malathion, and p,p'-DDE), and one 

fungicide (chlorothalonil; table 6). 

44 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999– 2001 
Figure 21. Median monthly total pesticide concentrations at selected sites in the Mobile River Basin, January 1999 – 

December 2001. 

Pesticides 45 
Figure 21. (Continued) Median monthly total pesticide concentrations at selected sites in the Mobile River Basin, 

January 1999 – December 2001. 

46 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999 – 2001 
Figure 21. (Continued) Median monthly total pesticide concentrations at selected sites in the Mobile River Basin, 

January 1999 – December 2001. 

Pesticides 47 
48 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999 – 2001

Figure 22. Atrazine concentrations and corresponding streamflow at six sites in the Mobile River Basin, January 1999 – December 2001.
Pesticides 49

Figure 23. Simazine concentrations and corresponding streamflow at six sites in the Mobile River Basin, January 1999 – December 2001.
50 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999 – 2001

Figure 24. Metolachlor concentrations and corresponding streamflow at six sites in the Mobile River Basin, January 1999 – December 200
Table 6. Water-quality standards, guidelines, and maximum concentrations of pesticides detected in surface-water samples from the 

Mobile River Basin 

[Concentrations in micrograms per liter; MCL, maximum contaminant level; HAL, health advisory level; USEPA, U.S. Environmental Protection Agency; 

NAS/NAE, National Academy of Sciences and National Academy of Engineering; —, no standard or guideline has been established] 

Pesticide Maximum 

MCLa 

lifetime a 

a aquatic lifeb aquatic lifec 

NAS/NAE 

maximum 

d 

2,4-D 74.6 70 — — 4 3 

2,4-DB 0.02 — — — — 4 — 

0.046 — — 1 — — — 

Alachlor 0.018 2 — .4 — — — 

Atrazine 201 3 200 — — 1.8 — 

Bentazon 0.053 — 200 — — — — 

Bromacil 0.15 — 90 — — 5 — 

0.045 — 100 — — — — 

Cyanazine 5.54 — 1 — — 2 — 

Dacthal 0.002 — 70 — — — — 

Dicamba 0.638 — 200 — — 10 200 

Dinoseb 0.004 7 7 — — .05 — 

Diuron 2.19 — 10 — — — 1.6 

Fluometuron 0.156 — 90 — — — — 

0.634 — 4 — — 2.6 — 

9.21 — 100 — — 7.8 — 

0.319 — 200 — — 1 — 

Prometon 0.044 — 100 — — — — 

Pronamide 0.066 — 50 — — — — 

7.13 4 4 — — 10 10 

0.489 — 500 — — 1.6 — 

0.036 — 90 — — — — 

0.002 — — — — .24 — 

0.039 — 5 5 — .2 — 

Insecticides 

-HCH 0.02 — — 0.006 e — — — 

0.422 — 700 — — 0.2 0.02 

Carbofuran 0.017 40 40 — — 1.8 — 

0.213 — 20 — f g .0035 .001 

Diazinon 1.01 — 0.6 — .08h .009 

Dieldrin 0.0241 — — .002 f g — .005 

9.58 — 100 — 0.1g — .008 

Methomyl 0.004 — 200 — — — — 

p,p 0.004 — — .1 f g — — 

Fungicide 

Chlorothalonil 1.84 — — 1.5 — 0.18 — 

Drinking water Ambient surface water 

concentration 

USEPA 

drinkingwater 

standard or 

USEPA 

HAL

USEPA risk 

specific dose 

at 10E-6 

cancer risk 

(RSD6)

USEPA 

water-quality 

criteria— 

Canadian 

water-quality 

guideline— recommended 

concentration

Herbicides 

Acifluorfen 

Chloramben, methyl ester 

MCPA 

Metolachlor 

Metribuzin 

Simazine 

Tebuthiuron 

Terbacil 

Triallate 

Trifluralin 

alpha

Carbaryl 

Chlorpyrifos 0.083 , 0.041

(0.1) draft 

0.24 , 0.056

Malathion 

'-DDE 1.1 , 0.001

(total DDT) 

a U.S. Environmental Protection Agency (2000c; 2002).


b U.S. Environmental Protection Agency (1999).


c

 Canadian Council of Ministers of the Environment (2001).


d

 National Academy of Sciences and National Academy of Engineering (1973).


e

 Integrated Risk Information System (U.S. Environmental Protection Agency, 2003).
 f

 Criterion maximum concentration for aquatic life (U.S. Environmental Protection Agency, 1999).
 g

 Criterion continuous concentration for aquatic life (U.S. Environmental Protection Agency, 1999).
 h

 International Joint Commission United States and Canada (1978).


Pesticides 51 
Occurrence of Pesticides by Sampling Site 

Pesticide samples were collected at all nine sites 

in the Mobile River Basin and statistical summaries of 

pesticide concentrations are shown by site in 

appendix 3. Sampling, however, was concentrated at 

the three intensive fixed sites (Bogue Chitto Creek, 

Cahaba River, and Cahaba Valley Creek), an urban 

indicator site (Threemile Branch), and the three largest 

integrator sites (Alabama River, Black Warrior River, 

and Tombigbee River). A detailed description of the 

pesticides detected at these seven sites is included in 

the following paragraphs. 

Bogue Chitto Creek near Memphis, Alabama 

The Bogue Chitto Creek Basin was selected as 

an agricultural indicator site—approximately 

89 percent of the 53-mi2 basin consists of row crops, 

pasture, or hay (fig. 4). The pesticides detected in the 

highest concentrations at Bogue Chitto Creek were 

atrazine (201 μg/L), molinate (13.9 μg/L), metolachlor 

(9.21 μg/L), cyanazine (5.54 μg/L), 2-hydroxyatrazine 

(3.42 μg/L), 2,4-D (2.29 μg/L), and deethylatrazine 

(2.33 μg/L; appendix 3). The herbicide, atrazine, and 

its metabolite, deethylatrazine, were detected in every 

pesticide sample collected from Bogue Chitto Creek. 

Fluometuron, metolachlor, and 2-hydroxyatrazine 

were detected in more than 84 percent of the samples 

collected from Bogue Chitto Creek. 

A total of 17,217 surface-water samples were 

collected nationally by the 1991, 1994, and 1997 

NAWQA Study Units and analyzed for atrazine. The 

three highest atrazine concentrations detected at sites 

across the country were recorded at Bogue Chitto 

Creek (U.S. Geological Survey, 2003). Concentrations 

of atrazine exceeded 100 μg/L during low flow 

(184 μg/L at 11 cubic feet per second [ft3

/s]) in April 

1999 and during high flow (201 μg/L at 1,140 ft3

/s in 

May 1999 and 136 μg/L at 2,520 ft3/s in April 2000) 

(fig. 22). Concentrations of atrazine exceeded 20 μg/L 

in four other samples collected in May and June 1999 

and in March 2000 (fig. 22). The highest median 

monthly concentrations of atrazine occurred in April, 

May, and June, which coincide with applications as a 

preemergent herbicide on corn (fig. 21). Concentrations of atrazine exceeded Canadian aquatic life 

guidelines in 18 of 52 samples (35 percent); all 

18 samples were collected from March through June 

(1999–2001). 

The highest median monthly concentrations of 

cyanazine occurred in July and August, which coincide 

with its use as a postemergent herbicide on cotton 

(fig. 21). Concentrations of cyanazine and metolachlor 

exceeded the Canadian aquatic life guidelines once 

each; chlorpyrifos exceeded the USEPA aquatic criteria 

in 5 of 52 samples (10 percent) and the Canadian 

aquatic life guidelines in 14 of 52 samples (27 percent). 

Carbaryl exceeded the National Academy of Sciences 

and National Academy of Engineering (NAS/NAE) 

standards in one sample, and malathion exceeded the 

NAS/NAE standards in 4 of 52 samples (8 percent; 

National Academy of Sciences and National Academy 

of Engineering, 1973). 

Cahaba River at Centreville, Alabama 

The Cahaba River at Centreville was selected as 

an intensive integrator site. The pesticide detected in 

the highest concentration at this site was simazine 

(1.14 μg/L; appendix 3). Atrazine was detected in 

every pesticide sample collected from the Cahaba 

River. Deethylatrazine and simazine were detected in 

more than 92 percent of the pesticide samples. 

Concentrations of diazinon exceeded the NAS/NAE 

standards in 11 of 40 samples (28 percent); 

chlorpyrifos concentrations exceeded the NAS/NAE 

standards in 19 of 40 samples (48 percent) and the 

Canadian aquatic life guidelines in 13 of 40 samples 

(32 percent). Concentrations of carbaryl exceeded the 

NAS/NAE standards in 1 of 40 samples (2 percent). 

Cahaba Valley Creek at Cross Creek Road at Pelham, 

Alabama 

The 25.6-mi2 Cahaba Valley Creek Basin was 

selected as an urban indicator site and is located in a 

rapidly developing area in the southeast part of 

Birmingham, Ala. (fig. 3). Approximately 9 percent of 

the basin is residential and commercial, and 78 percent 

is forested land. The pesticides detected in the highest 

concentrations at Cahaba Valley Creek were simazine 

(1.99 μg/L) and deisopropylatrazine (1.03 μg/L; 

appendix 3). Simazine was detected in every pesticide 

sample collected at Cahaba Valley Creek. Atrazine, 

deethylatrazine, and diazinon were detected in more 

than 81 percent of the pesticide samples collected from 

Cahaba Valley Creek. Concentrations of carbaryl 

exceeded the Canadian aquatic life guidelines in 2 of 

63 samples (3 percent) and the NAS/NAE standards in 

6 of 63 samples (10 percent). Concentrations of 

52 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999– 2001 
chlorpyrifos exceeded the Canadian aquatic life 

guidelines in 12 of 63 samples (19 percent) and the 

NAS/NAE standards in 21 of 63 samples (33 percent). 

Concentrations of diazinon exceeded the Canadian 

aquatic life guidelines in 2 of 63 samples (3 percent) 

and the NAS/NAE standards in 30 of 63 samples 

(48 percent). Malathion concentrations exceeded the 

NAS/NAE standards in 1 of 63 samples (2 percent). 

Threemile Branch at North Boulevard at Montgomery, 

Alabama 

The Threemile Branch Basin was selected as an 

urban indicator site and is located in northern 

Montgomery in a suburban area (fig. 3). Approximately 59 percent of the 8.79-mi2 basin is urban and 

includes light industrial activities (fig. 4). The stream 

channel contains both natural and channelized sections. 

The pesticides detected in the highest concentrations at 

Threemile Branch were 2,4-D (74.6 μg/L), malathion 

(9.58 μg/L), simazine (7.13 μg/L), imazaquin 

(5.89 μg/L), atrazine (4.83 μg/L), diuron (2.19 μg/L), 

chlorothalonil (1.84 μg/L), and diazinon (1.01 μg/L; 

appendix 3). The highest concentrations of 2,4-D, 

imazaquin, and malathion recorded nationally by the 

1991, 1994, and 1997 NAWQA Study Units were 

detected at Threemile Branch (U.S. Geological Survey, 

2003). The insecticide chlorpyrifos was detected in 

every pesticide sample (28 of 28) collected from 

Threemile Branch. Atrazine, deethylatrazine, 

simazine, metolachlor, and diazinon were detected in 

more than 86 percent of the pesticide samples collected 

from Threemile Branch; dieldrin and bromacil were 

detected in more than 75 percent of the samples. 

 Concentrations of atrazine and chlorothalonil 

exceeded the Canadian guidelines for aquatic life in 

1 of 28 and 1 of 14 samples, respectively. 

Concentrations of simazine exceeded the USEPA 

drinking-water standards once, and diuron 

concentrations exceeded the NAS/NAE standards 

twice. Concentrations of 2,4-D and diazinon each 

exceeded the USEPA lifetime health advisories once 

during the study period, and carbaryl concentrations 

exceeded the NAS/NAE standards in 8 of 28 samples 

(29 percent). Concentrations of malathion exceeded the 

USEPA aquatic-life criteria in 6 of 28 samples 

(21 percent) and the NAS/NAE standards in 16 of 

28 samples (57 percent). Concentrations of 

chlorpyrifos exceeded the USEPA aquatic-life criteria 

in 3 of 28 samples (11 percent) and the Canadian 

aquatic life guidelines in 27 of 28 samples (96 percent). 

Although dieldrin has been banned since the 

mid-1980’s (Barbash and Resek, 1996), concentrations 

of dieldrin were detected in 21 of 28 surface-water 

samples (75 percent) at Threemile Branch. Twenty of 

these concentrations exceeded the NAS/NAE 

standards. Dieldrin also was detected in the ground 

water at 7 of 30 wells (23 percent) in the Montgomery 

area (Robinson, 2002). Ground-water contributions to 

streams are most significant in geologic settings that 

allow the exchange of water between ground-water and 

surface-water systems, such as in the alluvial and 

terrace deposits underlying Threemile Branch. The 

median age of the ground water in the alluvial and 

terrace deposits underlying Threemile Branch is 

approximately 12 years (Robinson, 2002). Dieldrin 

also was detected in the streambed sediment and fishtissue samples at Threemile Branch (Zappia, 2002). 

Alabama River at Claiborne, Alabama 

The Alabama River site is located on the 

southeastern rim of the Mobile River Basin and drains 

an area of 21,967 mi2

. This site was selected as a basic 

integrator site and is the farthest downstream location 

on the Alabama River that is not tidally affected. 

Atrazine and simazine were detected in every pesticide 

sample collected from the Alabama River. 

Deethylatrazine, metolachlor, and diuron were detected 

in more than 78 percent of the pesticide samples. 

Concentrations of chlorpyrifos exceeded the Canadian 

aquatic life guidelines in 1 of 18 samples (5 percent). 

Concentrations of diazinon exceeded the NAS/NAE 

standards in 2 of 18 samples (11 percent). 

Black Warrior River below Bankhead Lock and Dam near 

Bessemer, Alabama 

The Black Warrior River site is located at the 

southern edge of the Cumberland Plateau and drains an 

area of 3,979 mi2, integrating various land-use 

conditions over the entire plateau. Atrazine, 

deethylatrazine, simazine, and metolachlor were 

detected in each of the nine pesticide samples collected 

from the Black Warrior River. Prometon was detected 

in over 78 percent of the pesticide samples. 

Concentrations of diazinon exceeded the NAS/NAE 

standards in 1 of 9 samples (11 percent). 

Occurrence of Pesticides by Sampling Site 53 
Tombigbee River below Coffeeville Lock and Dam near 

Coffeeville, Alabama 

The Tombigbee River below Coffeeville Lock 

and Dam is located on the southwestern rim of the 

Mobile River Basin and drains an area of 18,417 mi2. 

This site was selected as a basic integrator site and is 

the farthest downstream location on the Tombigbee 

River that is not tidally affected. The pesticide detected 

at this site in the highest concentration was atrazine 

(2.86 μg/L; appendix 3). The herbicides atrazine and 

metolachlor were detected in every pesticide sample 

collected from the Tombigbee River. Deethylatrazine, 

simazine, and diuron were detected in over 84 percent 

of the pesticide samples. The highest median monthly 

concentrations of atrazine occurred in April, May, and 

June, which coincide with applications of atrazine as a 

preemergent herbicide on corn in the Tombigbee River 

Basin (fig. 21). Concentrations of atrazine exceeded the 

Canadian guidelines for aquatic life in 1 of 19 samples 

(5 percent); chlorpyrifos concentrations exceeded the 

Canadian guidelines for aquatic life in 1 of 19 samples 

(5 percent) and the NAS/NAE standards in 2 of 

19 samples (10 percent). 

Occurrence of Pesticides in the Mobile River 

Basin 

Pesticide occurrence in water is related to the 

physical properties of the compound as well as the 

method of pesticide application. The types and 

concentrations of pesticides found in surface water are 

linked to land use and to the types of pesticides used in 

each setting. Each site described in the previous section 

was categorized according to land use—agricultural, 

mixed, and urban. The most frequently detected 

pesticides, based on land use, are shown in figure 25. 

Some pesticides were detected more frequently in 

basins draining specific land uses. Herbicides, for 

example, were detected more frequently and usually at 

higher concentrations in Bogue Chitto Creek, the 

agricultural stream (fig. 25). Fluometuron and 

cyanazine were detected in 84 and 60 percent of the 

water samples, respectively, at this site; however, they 

were detected in less than 12 percent of the samples 

from urban or mixed land-use sites. Thirteen of 

21 herbicides (atrazine, deethylatrazine, 2-

hydroxyatrazine, 2,4-D, deisopropylatrazine, 

deethyldeisopropylatrazine, metolachlor, imazaquin, 

pendimethalin, trifluralin, fluometuron, bentazon, and 

Figure 25. Frequencies of pesticide detections in surface-water samples from the Mobile River Basin, 1999 – 2001. 

54 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999– 2001 
cyanazine) were detected more frequently at the 

agricultural basin than at the urban or mixed land-use 

basins (fig. 25). Insecticides, however, were detected 

more frequently and usually at higher concentrations in 

the urban streams (Cahaba Valley Creek, Threemile 

Branch) than at the agricultural or mixed land-use sites 

(fig. 25). Diuron, tebuthiuron, and prometon were 

detected more frequently in streams draining mixed 

land use (Alabama River, Cahaba River, Black Warrior 

River, and the Tombigbee River; fig. 25). 

Concentrations of pesticides varied seasonally in 

streams, mainly as a result of the timing and amount of 

pesticide use and the frequency and magnitude of 

runoff from precipitation and irrigation. 

Concentrations of herbicides generally were higher in 

agricultural streams and varied according to season and 

the frequency and magnitude of runoff (figs. 22–24). 

For example, the highest concentrations of atrazine 

were at Bogue Chitto Creek and generally occurred in 

April and May, corresponding to its application on corn 

(figs. 21, 22). Seasonal patterns were less evident in 

urban streams, where concentrations of herbicides and 

insecticides remained relatively constant throughout 

the year. One exception was simazine, which was 

detected at elevated concentrations during the fall and 

winter months, November through March, at Cahaba 

Valley Creek (figs. 21, 23). Simazine is applied during 

the fall to control winter weeds and during late winter 

to control summer annual weeds (Alabama 

Cooperative Extension System, 1997). 

The occurrence and timing of pesticides found in 

streams is largely determined by crop type(s) in 

agricultural basins. Agricultural production in each of 

the nine basins is shown in table 7 (U.S. Department of 

Agriculture, 1999, 2002). The primary herbicides, 

insecticides, and fungicides applied to agricultural land 

in Alabama are listed in table 8, along with the types of 

crops on which the pesticides are used most frequently 

(Gianessi and Marcelli, 2000; National Center for Food 

and Agricultural Policy, 2000). Many pesticides are 

applied at specific stages of the crop growth cycle. 

Pesticide applications commonly include preplant, 

preemergent, and postemergent applications. Atrazine, 

for example, is a triazine herbicide used to control 

weeds in corn and grain sorghum in the Mobile River 

Basin (Alabama Cooperative Extension System, 1998). 

Atrazine is applied as a preemergent herbicide on corn, 

which is one of the major crops grown in the Mobile 

River Basin (table 7). Planting of corn generally begins 

in mid-March and continues through early June 

(Vanderberry and Placke, 2002). In basins where corn 

production is high, atrazine concentrations would be 

expected to peak shortly after planting has occurred. 

Corn production in the Bogue Chitto Creek Basin 

exceeded 445,000 bushels in 2001 (table 7). The 

highest concentrations of atrazine in the Mobile River 

Basin were detected in water samples collected from 

Bogue Chitto Creek during May (figs. 21, 22). Corn 

production in the Tombigbee River Basin exceeded 

9,783,000 bushels in 2001 (table 7). The highest 

concentrations of atrazine at the Tombigbee River also 

were detected during May (figs. 21, 22). 

Cyanazine is a triazine herbicide used 

extensively in the Midwest as a preemergent herbicide 

on corn; however, in the Mobile River Basin, cyanazine 

is used primarily as a postemergent herbicide on cotton 

(Alabama Cooperative Extension System, 1998). In 

basins where cotton production is high, cyanazine 

concentrations would be expected to peak well after 

planting has occurred. In the Mobile River Basin, 

Table 7. Agricultural production in the Mobile River Basin, 2001 (U.S. Department of Agriculture, 1999; 2002) 

Site 

number 

(fig. 3) 

Site name Drainage area 

(square miles) 

Corn 

(bushels) 

Cotton 

(bails) 

Hay 

(tons) 

Oats 

(bushels)

Peanuts 

(pounds) 

Sorghum

 (bushels)

Soybeans 

(bushels) 

Wheat 

(bushels) 

1 Chattooga River 366 87,820 2,859 2,053 0 0 0 44,129 29,388 

2 Threemile Branch 8.79 95 5 58 0 0 0 0 0 

3 Pintlalla Creek 59.3 3,786 211 2,534 0 53,396 0 0 0 

4 Cahaba Valley Creek 25.6 130 198 651 0 0 0 0 0 

5 Cahaba River 1,027 10,779 2,557 23,989 0 0 0 0 2,054 

6 Alabama River 21,967 2,642,034 165,532 715,208 0 990,181 0 862,626 648,707 

7 Bogue Chitto Creek 52.6 445,714 2,066 891 0 0 0 73,250 12,956 

8 Black Warrior River 3,979 509,023 11,249 300,604 0 0 0 191,295 33,956 

9 Tombigbee River 18,417 9,783,666 84,650 549,742 0 0 0 4,575,821 394,642 

Occurrence of Pesticides in the Mobile River Basin 55 
Table 8. Selected herbicides, insecticides, and fungicides applied to crops in Alabama, 1997 (National Center for Food and Agricult

56 

Herbicides ce a Occurren Main crop(s) treated Insecticides Main crop(s) treated Fungicides 

2,4-D

nd DPasture, corn, hay, wheat Acephate Cotton, peanuts Azoxystrobin 

2,4-DB

istrPeanuts, soybeans Aldicarb Cotton, peanuts Captan 

Acifluorfen

ibutPeanuts, soybeans Carbaryl Hay, corn, peaches, pecans Chlorothalon

Alachlor

ionSoybeans, corn Carbofuran Alfalfa, watermelons Copper 

Atrazine

of NCorn Chlorpyrifos Peanuts, pecans, corn Etridiazole 

Bentazon 

utriePeanuts, soybeans Dicrotophos Cotton Fenbuconazo

Chlorimuron 

nts,Soybeans, peanuts Disulfoton Cotton, peanuts, pecans Ferbam 

Clomazone 

SusCotton Imidacloprid Cotton, pecans Flutolanil 

Cyanazine 

penCotton Lambdacyhalothrin Cotton, wheat Mancozeb 

Diuron

dedCotton, pecans, peaches Malathion Cotton, hay, wheat Maneb 

DSMA

SedCotton Methamidophos Cotton, potatoes Metalaxyl 

Flumetsalem 

imeSoybeans, corn Methomyl Cotton, soybeans, hay, corn, peanuts PCNB 

Fluometuron 

nt, aCotton Methyl parathion Cotton, corn, soybeans Propiconazol

Fomesafen 

nd PSoybeans Oil Cotton, peaches Sulfur 

Glyphosate

estiSoybeans, cotton, pasture, pecans, corn Oxamyl Cotton Tebuconazole 

Imazaquin 

cideSoybeans Phorate Cotton, peanuts 

Imazathapyr s in Peanuts, soybeans Phosmet Pecans, sweet potatoes MCPA 

theWheat, oats Profenos Cotton 

Metolachlor 

MobPeanuts, soybeans, corn Spinosad Cotton 

Metribuzin 

ileSoybeans Sulprofos Cotton 

MSMA

RiveCotton, sod Terbufos Corn 

Nicosulforon

r BaCorn Thiodicarb Cotton 

Norflurazon 

sin,Cotton 

Paraquat 

 1999 Peanuts, cotton, corn, soybeans 

Pendimethalin Cotton, peanuts, soybeans 

– 2001 Prometryn Cotton 

Sethoxydim Cotton, soybeans, peanuts Simazine Corn, pecans, peaches Trifluralin Cotton, soybeans 
cotton generally is planted in early April to mid-June 

(Vanderberry and Placke, 2002). Although cotton is 

grown in several basins (table 7), cyanazine was 

detected at only two sites—Bogue Chitto Creek and 

the Tombigbee River (fig. 21; appendix 3). Cyanazine 

was detected most frequently at Bogue Chitto Creek 

(31 of 52 samples, 60 percent), and peak concentrations 

were recorded during July and August (fig. 21). 

The types, concentrations, and timing of 

pesticides found in streams are related to the proportion 

of urban and agricultural land in the drainage basin and 

the hydrology and basin characteristics. Marked 

similarities were observed between pesticides detected 

in small streams draining one primary land-use area 

and the pesticides detected in large rivers draining 

basins encompassing these small streams. 

Concentrations of pesticides in the large rivers 

generally were much lower than in their corresponding 

tributaries because of dilution and runoff from other 

land-use areas within the larger, more integrated 

basins. For example, the agricultural pesticides in the 

Tombigbee River reflected those compounds present in 

its tributary, Bogue Chitto Creek (fig. 21). The 

highest median monthly concentrations of atrazine 

and two of its metabolites (deethylatrazine and 

2-hydroxyatrazine) were found in samples from Bogue 

Chitto Creek, with peak concentrations occurring in 

May, and decreasingly high concentrations occurring 

in April, June, and July (fig. 21). The same pattern 

occurred in the Tombigbee River, although the 

concentrations were approximately one order of 

magnitude less (fig. 21). 

Similarities also occurred in the urban pesticides 

detected in the Cahaba River and Cahaba Valley Creek 

(fig. 21). The highest median monthly concentrations 

of simazine in Cahaba Valley Creek occurred during 

November with decreasingly high concentrations 

occurring in January and February; a similar pattern 

occurred in the Cahaba River, where simazine 

concentrations also peaked in November (fig. 21). 

Imazaquin concentrations were highest at both sites in 

December, and 2,4-D concentrations were highest at 

both sites during March and April. Median monthly 

total pesticide concentrations were lowest at both sites 

during June–October (fig. 21). 

Differences also were observed between the 

large rivers draining the western half of the Mobile 

River Basin and those draining the eastern half. In 

general, pesticide concentrations in the Tombigbee 

River were dominated by the presence of atrazine and, 

to a lesser degree, 2-hydroxyatrazine, 2,4-D, and 

metolachlor (fig. 21). Total pesticide concentrations in 

the Tombigbee River exceeded those in the Alabama 

River during the growing season (April–August) and 

mirrored the type and pattern of pesticides detected at 

one of its tributaries, Bogue Chitto Creek, although 

concentrations were less in the Tombigbee River. 

Pesticide concentrations in the Alabama River were 

dominated by the presence of simazine and, to a lesser 

degree, atrazine and 2,4-D (fig. 21). 

Differences were observed in water samples 

from the two urban sites, Threemile Branch in 

Montgomery and Cahaba Valley Creek in Birmingham. 

Total pesticide concentrations generally were more 

than one order of magnitude greater at Threemile 

Branch than at Cahaba Valley Creek. Atrazine, 2,4-D, 

diuron, and imazaquin were detected in greater 

concentrations at Threemile Branch than at Cahaba 

Valley Creek; metolachlor, 2,4-D, chlorpyrifos, 

dieldrin, and bromacil were detected more frequently at 

Threemile Branch than at Cahaba Valley Creek 

(appendix 3). One explanation for this may be the 

different percentages of urban land use in each basin 

(Threemile Branch—59 percent; and Cahaba Valley 

Creek—9 percent; fig. 4). Another explanation may be 

the differences in sampling frequencies at the two sites 

(table 1). 

The number of pesticides present in a stream also 

may be important from a toxicological standpoint. At 

least one pesticide was detected in all but 2 of the 234 

stream samples collected during this study. More than 

90 percent of all the stream samples contained three or 

more pesticides; more than 50 percent contained nine 

or more compounds. Chemical breakdown products, 

which can have similar, lesser, or even greater toxicities 

than parent compounds, can be as common in the water 

as parent compounds (U.S. Geological Survey, 1999). 

Atrazine was detected in 99 percent of all stream 

samples in the Mobile River Basin, and 

deethylatrazine, a breakdown product of atrazine, was 

detected in nearly 92 percent of the samples. Generally, 

the effects of pesticide mixtures on biota or humans are 

not included in water-quality criteria, which most 

commonly are based on single-species, singlechemical toxicity tests conducted under laboratory 

conditions (Hampson and others, 2000). 

Pesticide information gathered in the Mobile 

River Basin indicates that exposure is complicated by 

lengthy periods of low concentrations that are often 

punctuated by seasonal pulses of much higher 

Occurrence of Pesticides in the Mobile River Basin 57 
concentrations, in addition to complex mixtures of 

compounds and breakdown products. Possible risks 

from these patterns of exposure have not been fully 

evaluated because drinking-water or aquatic-life 

standards have not been determined for many of the 

contaminants and their breakdown products; 

furthermore, the existing standards do not address 

exposure to mixtures or brief pulses of high 

concentrations. Some pesticides may become more 

toxic when combined with other compounds. The 

additive and synergistic effects created from low 

concentrations of multiple pesticides have yet to be 

quantified (Hoffman and others, 2000). The combined 

ecological effects of multiple pesticides in the streams 

are unknown. 

Occurrence of Pesticides in the Mobile River 

Basin Compared to Other NAWQA Study Units 

Surface-water samples were collected for 

pesticide analyses at more than 162 sites in 49 of the 

Nation’s major river basins during 1991–2001 as part 

of the NAWQA Program. The analytical results can be 

used to improve the understanding of the relation 

between water quality and land use, pesticide use, soils, 

climate, and other natural or human influences. 

Surface-water sites in the NAWQA Program were 

classified into four land-use groups: agricultural 

(78 sites), undeveloped (4 sites), urban (33 sites), and 

mixed (47 sites). Three sites in the Mobile River Basin 

were included in this aggregate data set: Bogue Chitto 

Creek, Cahaba Valley Creek, and Cahaba River. A 

1-year period of data was selected for each site 

included in the aggregate data set to describe annual 

distributions of pesticide concentrations and annual 

detection frequencies. Detections in water samples 

were time-weighted, and the pooled detection 

frequency was calculated across all sites in a land-use 

category. As a consequence, the frequency of detection 

may be interpreted as an estimate of the percentage of 

time that pesticides are detected at a NAWQA site in a 

particular land-use category (J.D. Martin, U.S. 

Geological Survey, written commun., 2003). The water 

samples in the aggregate NAWQA pesticide data were 

collected by using the same sampling procedures as 

those used in the Mobile River Basin. The aggregate 

NAWQA pesticide data are comparable to the data 

collected in the Mobile River Basin, although there 

may be slight differences in the MRLs and LRLs as a 

result of refined analytical techniques and the different 

methods used by the NWQL. 

Pesticide data from the Mobile River Basin 

included samples collected for the entire 3-year period 

(1999–2001) at the following sites: Bogue Chitto 

Creek (agricultural land use), Cahaba Valley Creek and 

Threemile Branch (urban land use), and Alabama 

River, Black Warrior River, Cahaba River, and 

Tombigbee River (mixed land use). Results 

summarized in figure 26 provide a framework for 

comparing water quality among sites with different 

types of land use. 

A comparison of the results from Bogue Chitto 

Creek with the aggregate data set for agricultural 

streams indicates some strong similarities and some 

regional differences (fig. 26A). In the aggregate data 

set, the five most frequently detected pesticides (not 

including pesticide metabolites) were atrazine 

(90 percent), metolachlor (83 percent), simazine 

(57 percent), prometon (43 percent), and cyanazine 

(40 percent). At Bogue Chitto, the five most frequently 

detected pesticides (not including pesticide 

metabolites) were atrazine (100 percent), metolachlor 

(96 percent), fluometuron (84 percent), simazine 

(73 percent), and cyanazine (60 percent). The frequent 

occurrence of fluometuron at Bogue Chitto Creek is 

indicative of the use of this pesticide on cotton in the 

basin. Fluometuron also was detected frequently in 

agricultural settings in the Lower Tennessee River 

Basin (about 65 percent; Hoos and others, 2002) and in 

the Mississippi Embayment (about 65 percent; Kleiss 

and others, 2000), both areas with extensive cotton 

production. Although prometon was the fourth most 

frequently detected pesticide (43 percent) in the 

aggregate NAWQA data set, it was not detected at 

Bogue Chitto Creek. The herbicide 2,4-D, commonly 

used on corn and wheat, also was detected more 

frequently at Bogue Chitto Creek (55 percent) than at 

other agricultural sites across the country (15 percent). 

The five most frequently detected pesticides 

in the urban aggregate data set were prometon 

(84 percent), atrazine (74 percent), diazinon 

(65 percent), simazine (64 percent), and metolachlor 

(50 percent; fig. 26B). At the two urban sites in the 

Mobile River Basin, the five most frequently detected 

pesticides were atrazine (98 percent), simazine 

(96 percent), diazinon (84 percent), prometon 

(58 percent), and chlorpyrifos (54 percent). The 

presence of prometon and metolachlor was not as 

common at the urban sites in the Mobile River Basin as 

58 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999– 2001 
Figure 26. Frequencies of pesticide detections in surface-water samples from (A) agricultural, (B) urban, and (C) mixed land-use 

sites in the Mobile River Basin and at other National Water-Quality Assessment Study Units throughout the United States. 

Occurrence of Pesticides in the Mobile River Basin Compared to Other NAWQA Study Units 59 
at the urban sites across the country. Conversely, atrazine, fluometuron, simazine, 2,4-D, tebuthiuron, diuron, chlorpyrifos, diazinon, malathion, and dieldrin 

were detected more frequently in the Mobile River 

Basin than at other urban sites across the country 

(fig. 26B). 

The five most frequently detected pesticides in 

the mixed land-use aggregate data set were atrazine 

(88 percent), metolachlor (71 percent), simazine 

(67 percent), prometon (61 percent), and diazinon 

(42 percent; fig. 26C). At the mixed land-use sites in 

the Mobile River Basin, the five most frequently 

detected pesticides were atrazine (99 percent), 

simazine (95 percent), tebuthiuron (80 percent), diuron 

(74 percent), and prometon (67 percent). Diuron was 

detected only in 9 percent of the water samples from 

the mixed land-use aggregate data set. The herbicide 

2,4-D also was detected more frequently in the Mobile 

River Basin (51 percent) than at other mixed land-use 

sites across the country (8 percent). 

SUMMARY 

In 1997, the U.S. Geological Survey began a 

study of surface-water quality in the Mobile River 

Basin as part of the National Water-Quality 

Assessment (NAWQA) Program. Surface-water 

samples were collected at nine sites in Alabama. 

Indicator sites were chosen to characterize water 

quality in smaller basins draining predominantly 

agricultural or urban land-use settings. Large rivers 

were sampled as integrator sites to characterize water 

quality in drainage areas with mixed land use. Waterquality samples were collected between January 1999 

and December 2001. More than 340 water samples 

were analyzed for nitrogen and phosphorus, and more 

than 230 water samples were collected and analyzed 

for up to 104 pesticides. 

The nine sites included two streams draining 

agricultural areas, two urban streams, and five large 

rivers with mixed land-use drainage areas. The streams 

draining primarily agricultural watersheds were Bogue 

Chitto Creek and Pintlalla Creek. The Bogue Chitto 

Creek Basin, located primarily in Noxubee County, 

Miss., drains the western part of the Black Prairie Belt 

and is intensively cropped in soybeans, corn, cotton, 

and hay. The Pintlalla Creek Basin, located in 

Montgomery County, Ala., lies in the eastern part of the 

Black Prairie Belt. Land use in this basin is dominated 

by forested land and pastureland, with some 

interspersed areas of row crops and hay fields. The two 

urban streams include Threemile Branch in 

Montgomery, Ala., and Cahaba Valley Creek, located 

in a rapidly developing area in southeast Birmingham, 

Ala. The Chattooga River Basin is located in the 

northeastern section of the Mobile River Basin, and the 

Cahaba River is located at Centreville in central 

Alabama. The Black Warrior River below Bankhead 

Lock and Dam is located at the southern edge of the 

Cumberland Plateau. The Alabama River at Claiborne 

is located on the southeastern rim of the Mobile River 

Basin, and the Tombigbee River below Coffeeville 

Lock and Dam is located on the southwestern rim of the 

Mobile River Basin. 

Nutrient concentrations varied in relation to land 

use. High nutrient concentrations generally occurred at 

agricultural and urban sites. Total nitrogen 

concentrations ranged from 0.2 to 10 mg/L, and nitrate 

concentrations ranged from 0.03 to 7.94 mg/L, which 

was lower than the U.S. Environmental Protection 

Agency’s drinking-water standard of 10 mg/L for 

nitrate. Median nitrate concentrations in the Black 

Warrior River, a large river mixed land-use site, were 

higher than in the smaller agricultural indicator 

watersheds, and likely reflects extensive poultry 

production operations in the upper part of the Black 

Warrior River Basin and urban influences from the 

Birmingham metropolitan area. 

Total phosphorus concentrations ranged from 

0.008 to 2.22 mg/L. The highest total phosphorus 

concentration occurred at Bogue Chitto Creek, and the 

highest median concentration occurred at Cahaba 

Valley Creek, an urban site. The Chattooga River had 

the highest median and maximum phosphorus 

concentrations of all the integrator sites, which is of 

particular interest because the Chattooga River flows 

into Weiss Lake, where eutrophication problems have 

been noted. Forty-two percent of total phosphorus 

concentrations at all nine sites exceeded the U.S. 

Environmental Protection Agency goal of 0.10 mg/L 

for preventing nuisance plant growth in streams. 

Median total phosphorus concentrations at Bogue 

Chitto Creek, Cahaba Valley Creek, and the Chattooga 

River exceeded this goal. Dissolved phosphorus and 

dissolved orthophosphate concentrations also were 

high at Cahaba Valley Creek and the Chattooga River. 

Flow-weighted mean concentrations for the 

Mobile River Basin sites were generally in the lower to 

middle percentile ranges compared with data from 

other NAWQA studies across the Nation. However, 

60 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999– 2001 
flow-weighted mean concentrations of ammonia, total 

nitrogen, orthophosphate, and total phosphorus at 

Bogue Chitto Creek were in the upper 20th percentiles 

of agricultural sites. The orthophosphate concentration 

at the Chattooga River ranked in the 70th percentile, 

and the total phosphorus concentration at the Black 

Warrior River was in the 94th percentile of integrator 

sites. 

Nutrient loads were nearly twice as high in the 

Tombigbee River compared to the Alabama River for 

total nitrogen, nitrate, and total phosphorus, which 

reflects the agricultural influences occurring in the 

Tombigbee River drainage basin. Nutrient loads in 

Bogue Chitto Creek were higher than loads at the other 

indicator sites. Nutrient yields were highest in Bogue 

Chitto Creek, Cahaba Valley Creek, and Threemile 

Branch as a result of the agricultural and urban land 

uses in the watersheds. No significant long-term trends 

were detected for the Alabama, Cahaba, or Tombigbee 

Rivers, except for a decrease in nitrate at the Alabama 

River. The decrease in nitrate could be a result of 

improved wastewater-treatment practices and 

decreases in the amount of row-crop agricultural 

activities in the watershed. No short-term trends were 

detected at any of the three sites. 

Organic carbon concentrations generally were 

low and ranged from 0.9 to 17.8 mg/L for dissolved 

organic carbon and from 0.2 to 6.0 mg/L for suspended 

organic carbon. Concentrations generally were highest 

in the two agricultural watersheds, Bogue Chitto Creek 

and Pintlalla Creek; however, the high concentrations 

probably are due to the natural occurrence of organic 

carbon in soils and the chalk that underlies the basins, 

rather than agricultural land uses. 

Suspended-sediment concentrations ranged from 

1 to 2,450 mg/L at all nine sites. Bogue Chitto Creek 

had the highest median and maximum concentrations. 

Sediment yields were highest in Bogue Chitto Creek 

and lowest in the Black Warrior River, likely an 

influence of reservoirs upstream. 

Of the 104 pesticides and degradation products 

analyzed in the stream samples, 69 were detected in 

one or more samples. Of the 69 detected pesticides, 

51 were herbicides, 15 were insecticides, and 3 were 

fungicides. A relatively small number of heavily used 

herbicides accounted for most of the detections, 

including atrazine and its metabolites (deethylatrazine, 

2-hydroxyatrazine, deisopropylatrazine, and 

deethyldeisopropylatrazine), simazine, metolachlor, 

tebuthiuron, prometon, diuron, and 2,4-D. Diazinon, 

chlorpyrifos, and carbaryl were the most frequently 

detected insecticides; metalaxyl was the most 

frequently detected fungicide in the Mobile River 

Basin. At least one pesticide was detected in all but two 

of the 234 stream samples. More than 90 percent of all 

the stream samples contained three or more pesticides; 

more than 50 percent contained nine or more 

compounds. 

Concentrations of pesticides detected in surface 

water of the Mobile River Basin were among the 

highest concentrations recorded nationally by the 1991, 

1994, and 1997 NAWQA Study Units. The three 

highest concentrations of atrazine detected at sites 

across the country were recorded at Bogue Chitto 

Creek; the highest concentrations of 2,4-D, imazaquin, 

and malathion recorded nationally were detected at 

Threemile Branch. 

Aquatic-life criteria have been established for 23 

of the 69 pesticides detected in this study. These criteria 

were exceeded by five herbicides (2,4-D, atrazine, 

cyanazine, diuron, and metolachlor), six insecticides 

(carbaryl, chlorpyrifos, diazinon, dieldrin, malathion, 

and p,p '-DDE), and one fungicide (chlorothalonil). 

Drinking-water standards, guidelines, or health 

advisories have been established for 32 of the 

pesticides detected in this study. These limits were 

exceeded by concentrations of four herbicides (2,4-D, 

atrazine, cyanazine, and simazine), three insecticides 

(alpha-HCH, diazinon, and dieldrin), and one 

fungicide (chlorothalonil). 

The types and concentrations of pesticides found 

in surface water are linked to land use and to the types 

of pesticides used in each setting. Herbicides were 

detected more frequently and usually at higher 

concentrations in the agricultural stream, Bogue Chitto 

Creek, than in the urban or mixed land-use streams. 

Insecticides, however, were detected more frequently 

and usually at higher concentrations in the urban 

streams (Cahaba Valley Creek, Threemile Branch). 

Concentrations of pesticides varied seasonally in 

streams in response to the timing and amount of 

pesticides used and the frequency and magnitude of 

runoff from precipitation and irrigation. At Bogue 

Chitto Creek, the highest concentrations of atrazine 

occurred in April, May, and June, which coincide with 

its use as a preemergent herbicide on corn. The highest 

concentrations of cyanazine at Bogue Chitto Creek 

occurred in July and August, when cyanazine 

frequently is used as a postemergent herbicide on 

cotton. Seasonal patterns were less evident in urban 

Summary 61 
streams, where concentrations of herbicides and 

insecticides in surface water remained relatively 

constant throughout the year. 

The types, concentrations, and timing of 

pesticides found in streams are related to the proportion 

of urban and agricultural land in the drainage basin and 

the hydrology and basin characteristics. Marked 

similarities were observed between pesticides detected 

in small streams draining one primary land-use setting 

and pesticides detected in large rivers draining basins 

encompassing these small streams. Concentrations of 

pesticides in the large rivers generally were much lower 

than in their corresponding tributaries because of 

dilution and runoff from other land-use areas within the 

larger, more integrated basins. For example, the 

agricultural pesticides found in the Tombigbee River 

reflected those compounds present in its tributary, 

Bogue Chitto Creek, and the urban pesticides in the 

Cahaba River reflected those compounds found in its 

tributary, Cahaba Valley Creek. In both cases, the types 

of pesticides detected were similar between main stem 

and tributary, but the concentrations were greater in the 

tributaries. 

Differences also were noted between the large 

rivers draining the western half of the Mobile River 

Basin and those draining the eastern half. In general, 

pesticide concentrations on the Tombigbee River were 

dominated by the presence of atrazine and, to a lesser 

degree, 2-hydroxyatrazine, 2,4-D, and metolachlor. 

Pesticide concentrations on the Alabama River were 

dominated by the presence of simazine and, to a lesser 

degree, atrazine and 2,4-D. Total pesticide 

concentrations on the Tombigbee River exceeded 

concentrations on the Alabama River during the 

growing season (April–August). Differences also were 

noted between the two urban sites, Threemile Branch 

and Cahaba Valley Creek. Total pesticide 

concentrations generally were more than one order of 

magnitude greater at Threemile Branch than at Cahaba 

Valley Creek, which may be a result of the different 

percentages of urban land use in each basin and 

differences in sampling frequencies at the two sites. 

Exposure to pesticides is complicated by lengthy 

periods of low concentrations that are often punctuated 

by seasonal pulses of much higher concentrations, and 

complex mixtures of compounds and breakdown 

products. Possible risks associated with exposure have 

not been fully evaluated because drinking-water 

standards and aquatic-life standards have not been 

determined for many of the contaminants and their 

breakdown products. Furthermore, the existing 

standards do not address exposure to mixtures or brief 

pulses of high concentrations. 

Strong similarities and some regional differences 

were observed in the results from an aggregation of 

agricultural site data collected from other NAWQA 

Study Units (1991–2001) and the agricultural indicator 

site at Bogue Chitto Creek. In the aggregate data set, 

the most frequently detected pesticides (not including 

pesticide metabolites) were atrazine, metolachlor, 

simazine, prometon, and cyanazine. At Bogue Chitto 

Creek, the most frequently detected pesticides (not 

including pesticide metabolites) were atrazine, 

metolachlor, fluometuron, simazine, and cyanazine. 

The frequent occurrence of fluometuron at Bogue 

Chitto Creek is indicative of the use of this pesticide on 

cotton in the basin. Although prometon was the fourth 

most frequently detected pesticide in the aggregate 

NAWQA data set, it was not detected at Bogue Chitto 

Creek. The five most frequently detected pesticides in 

the urban aggregate data set (NAWQA) were 

prometon, atrazine, diazinon, simazine, and 

metolachlor. Three of these pesticides (atrazine, 

diazinon, and simazine) were detected more frequently 

at urban sites in the Mobile River Basin; prometon and 

metolachlor were detected less frequently at urban sites 

in the Mobile River Basin. The five most frequently 

detected pesticides in the mixed land-use aggregate 

data set (NAWQA) were atrazine, metolachlor, 

simazine, prometon, and diazinon. At the mixed landuse sites in the Mobile River Basin, the five most 

frequently detected pesticides were atrazine, simazine, 

tebuthiuron, diuron, and prometon. 

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Selected References 65 
APPENDIX 1 Quality Control 

66 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999–2001 
Appendix 1. Concentrations and relative percentage differences for pesticides detected in 46 replicate samples from the Mobile 

River Basin, 1999 – 2001 

[μg/L, micrograms per liter; E, estimated; <, less than; NC, not calculated; GC/MS, analyzed by gas chromatography/mass spectrometry; 

HPLC/MS, analyzed by high-performance liquid chromatography/mass spectrometry] 

Pesticide 

Concentration 

in replicates 

(μg/L) 

Relative 

percent 

difference 

Pesticide 

Concentration 

in replicates 

(μg/L) 

Relative 

percent 

difference 

2,4-D 0.6285 0.2 Acifluorfen E0.0269 27.8 

0.6274 E0.0356 

0.2399 2.8 Atrazine 0.00856 0.6 

0.2333 0.00851 

0.4885 1.8 0.0051 3.4 

0.4976 0.00493 

0.1068 3.6 1.02 2.1 

0.103 0.999 

0.1267 7.8 0.0464 2.0 

0.137 0.0455 

0.4615 9.7 0.0424 8.6 

0.4187 0.0389 

0.1154 12.1 0.029 2.4 

0.1022 0.0283 

0.3367 4.7 0.017 0.6 

0.3528 0.0171 

2,4-D methyl ester E0.0813 4.3 0.0149 0.0 

E0.0849 0.0149 

E0.0225 5.2 0.682 4.7 

E0.0237 0.651 

E0.0162 1.2 0.172 26.3 

E0.016 0.224 

E0.0283 3.5 0.0171 8.4 

E0.0293 0.0186 

2-hydroxyatrazine E0.0832 22.9 0.192 5.3 

E0.1047 0.182 

E0.0221 4.6 0.032 13.4 

E0.0211 0.0366 

E0.0549 3.0 0.0155 6.3 

E0.0566 0.0165 

E0.025 0.0 0.191 3.6 

E0.025 0.198 

E3.4174 32.7 0.0937 17.8 

E4.7551 0.112 

E0.3349 4.6 0.00833 24.9 

E0.3505 0.0107 

E0.2695 2.2 0.0521 22.5 

E0.2636 0.0653 

E0.1566 3.9 0.0323 1.9 

E0.1629 0.0317 

E1.507 118.6 0.0408 5.3 

E0.3851 0.043 

E0.0309 7.7 0.0266 1.1 

E0.0286 0.0263 

Appendixes 67 
Appendix 1. Concentrations and relative percentage differences for pesticides detected in 46 replicate samples from the Mobile 

River Basin, 1999 – 2001 — Continued 

[μg/L, micrograms per liter; E, estimated; <, less than; NC, not calculated; GC/MS, analyzed by gas chromatography/mass spectrometry; 

HPLC/MS, analyzed by high-performance liquid chromatography/mass spectrometry] 

Pesticide 

Concentration 

in replicates 

(μg/L) 

Relative 

percent 

difference 

Pesticide 

Concentration 

in replicates 

(μg/L) 

Relative 

percent 

difference 

Atrazine (Continued) 0.0593 14.5 Caffeine (Continued) E0.017 20.6 

0.0513 E0.0209 

0.0556 1.6 0.1088 10.5 

0.0565 0.1208 

0.311 0.3 E0.0376 NC 

0.312 <0.0805 

E136 13.3 Carbaryl E0.00316 (GC/MS) 1.3 

E119 E0.00312 (GC/MS) 

0.166 0.6 E0.0179 (GC/MS) 9.4 

0.167 E0.0163 (GC/MS) 

0.0783 5.0 E0.0287 (GC/MS) 2.5 

0.0745 E0.028 (GC/MS) 

0.0486 1.0 E0.369 1.9 

0.0491 E0.376 (GC/MS) 

0.038 15.9 E0.0166 (GC/MS) 1.8 

0.0324 E0.0163 (GC/MS) 

2.57 7.5 E0.12 (GC/MS) 5.1 

2.77 E0.114 (GC/MS) 

1.92 8.1 E0.0195 (GC/MS) 9.8 

1.77 E0.0215 (GC/MS) 

0.0485 4.4 E0.00213 (GC/MS) 19.1 

0.0464 E0.00258 (GC/MS) 

0.0418 5.4 E0.00609 (GC/MS) 5.1 

0.0441 E0.00641 (GC/MS) 

Benfluralin E0.00101 5.1 E0.0279 (GC/MS) 21.4 

E0.00096 E0.0346 (GC/MS) 

E0.00357 3.0 E0.00764 (GC/MS) 27.7 

E0.00368 E0.0101 (GC/MS) 

E0.00377 3.2 E0.0348 (GC/MS) 32.8 

E0.00365 E0.025 (GC/MS) 

<0.002 NC E0.00774 (GC/MS) NC 

E0.00107 <0.041 (GC/MS) 

Benomyl E0.0179 17.3 E0.00371 (GC/MS) NC 

E0.0213 <0.041 (GC/MS) 

Bentazon E0.0041 19.8 E0.0078 (HPLC/MS) 0.0 

E0.005 E0.0078 (HPLC/MS) 

E0.0052 17.5 E0.0098 (HPLC/MS) 9.6 

E0.0062 E0.0089 (HPLC/MS) 

E0.028 NC 0.0651 (HPLC/MS) 1.5 

<0.0193 0.0641 (HPLC/MS) 

Caffeine E0.0684 10.7 E0.0017 (HPLC/MS) 11.1 

E0.0761 E0.0019 (HPLC/MS) 

0.1414 1.1 E0.0042 (HPLC/MS) NC 

0.1398 <0.0628 (HPLC/MS) 

0.0997 10.8 Clopyralid E0.034 39.4 

0.0895 E0.0228 

68 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999– 2001 
Appendix 1. Concentrations and relative percentage differences for pesticides detected in 46 replicate samples from the Mobile 

River Basin, 1999– 2001— Continued 

[μg/L, micrograms per liter; E, estimated; <, less than; NC, not calculated; GC/MS, analyzed by gas chromatography/mass spectrometry; 

HPLC/MS, analyzed by high-performance liquid chromatography/mass spectrometry] 

Pesticide 

Concentration 

in replicates 

(μg/L) 

Relative 

percent 

difference 

Pesticide 

Concentration 

in replicates 

(μg/L) 

Relative 

percent 

difference 

Chlorpyrifos 0.00825 14.8 Deethylatrazine E0.00539 7.3 

0.00711 E0.0058 

E0.0035 0.3 E0.00623 3.8 

E0.00349 E0.006 

0.0299 3.7 E0.0629 3.7 

0.0288 E0.0606 

0.0189 8.8 E0.00814 5.1 

0.0173 E0.00857 

E0.00442 32.7 E0.0188 4.2 

0.00615 E0.0196 

0.00473 15.2 E0.0106 10.7 

0.00551 E0.0118 

E0.00388 1.5 E0.00537 12.9 

E0.00394 E0.00611 

0.0246 1.6 E0.0523 33.6 

0.025 E0.0734 

0.00808 5.1 E0.0162 29.0 

0.0085 E0.0217 

0.0128 15.2 E0.0124 12.1 

0.0149 E0.014 

E0.00483 25.6 E0.0138 2.2 

0.00625 E0.0135 

0.00529 52.8 E0.00549 5.7 

E0.00308 E0.00581 

0.211 11.5 E0.00301 NC 

0.188 <0.002 

0.0053 5.0 E0.0205 17.4 

0.00504 E0.0244 

Cyanazine 0.0176 11.8 E0.012 20.9 

0.0198 E0.0148 

0.0116 10.0 <0.006 NC 

0.0105 E0.0049 

0.021 11.1 E0.00582 24.7 

0.0188 E0.00746 

E0.00378 1.1 E0.00636 12.5 

E0.00374 E0.00561 

E0.00636 NC E0.00891 2.2 

<0.018 E0.00872 

0.483 8.2 E0.00729 20.1 

0.445 E0.00596 

0.0213 9.9 E0.00648 12.8 

0.0193 E0.0057 

Dacthal E0.00186 NC E0.0053 0.0 

<0.002 E0.0053 

p,p'-DDE <0.006 NC E0.157 0.6 

E0.00208 E0.158 

Appendixes 69 
Appendix 1. Concentrations and relative percentage differences for pesticides detected in 46 replicate samples from the Mobile 

River Basin, 1999– 2001— Continued 

[μg/L, micrograms per liter; E, estimated; <, less than; NC, not calculated; GC/MS, analyzed by gas chromatography/mass spectrometry; 

HPLC/MS, analyzed by high-performance liquid chromatography/mass spectrometry] 

Pesticide 

Concentration 

in replicates 

(μg/L) 

Relative 

percent 

difference 

Pesticide 

Concentration 

in replicates 

(μg/L) 

Relative 

percent 

difference 

Deethylatrazine 

(Continued) 

E1.3 

E0.78 

50.0 Deethyldeisopropylatrazine (Continued) E0.0251 

E0.017 

38.5 

E0.0317 4.9 Diazinon 0.0219 2.3 

E0.0333 0.0224 

E0.0232 4.9 E0.0038 17.5 

E0.0221 0.00453 

E0.0192 29.3 0.132 3.1 

E0.0143 0.128 

E0.00466 76.2 0.305 7.3 

E0.0104 0.328 

E0.0634 22.1 0.00877 6.6 

E0.0508 0.00821 

E0.489 8.1 0.0179 4.0 

E0.451 0.0172 

E0.0125 11.0 0.0082 6.7 

E0.0112 0.00877 

E0.00971 16.0 0.0409 2.4 

E0.0114 0.0419 

Deisopropylatrazine E0.4797 4.5 0.044 8.8 

E0.5019 0.0403 

E0.0678 4.1 0.00464 17.3 

E0.0651 0.00552 

E0.0416 10.5 0.00798 14.0 

E0.0462 0.00918 

E0.0577 5.6 0.0323 3.1 

E0.061 0.0313 

E0.6403 34.5 0.0508 2.4 

E0.4518 0.0496 

E0.0217 28.5 0.0172 0.6 

E0.0289 0.0173 

<0.0737 NC 0.0137 7.7 

E0.0124 0.0148 

<0.0737 NC 0.0414 25.9 

E0.0421 0.0537 

Deethyldeisopropylatrazine 0.0775 

0.0723 

6.9 0.00573 

0.00706 

20.8 

E0.0462 0.7 0.0073 36.6 

E0.0459 0.00504 

E0.0147 14.6 0.00907 43.0 

E0.0127 0.00586 

0.0607 28.6 E0.00322 6.4 

E0.0455 E0.00302 

E0.0243 16.6 E0.00331 17.4 

E0.0287 E0.00278 

0.1268 98.7 0.00481 NC 

E0.043 <0.002 

70 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999–2001 
Appendix 1. Concentrations and relative percentage differences for pesticides detected in 46 replicate samples from the Mobile 

River Basin, 1999– 2001— Continued 

[μg/L, micrograms per liter; E, estimated; <, less than; NC, not calculated; GC/MS, analyzed by gas chromatography/mass spectrometry; 

HPLC/MS, analyzed by high-performance liquid chromatography/mass spectrometry] 

Concentration Relative Concentration Relative 

Pesticide in replicates percent Pesticide in replicates percent 

(μg/L) difference (μg/L) difference 

Diazinon (Continued) 0.00524 NC Fluometuron E0.0837 3.2 

<0.005 (Continued) E0.0811 

0.00768 NC E0.0238 7.9 

<0.005 E0.022 

E0.00295 NC E0.0111 50.8 

<0.002 E0.0066 

Dicamba 0.2124 15.0 E0.0041 5.0 

0.1828 E0.0039 

E0.0843 12.1 Imazaquin E0.0488 2.6 

E0.0747 E0.0501 

E0.0291 41.0 E0.0889 0.7 

E0.0441 E0.0895 

E0.0708 NC Imazethapyr E0.1029 27.4 

<0.096 E0.0781 

Dichlorprop 0.0565 15.6 Imidacloprid E0.0182 3.4 

E0.0483 E0.0176 

E0.0234 2.6 Lindane E0.00244 NC 

E0.0228 <0.004 

<0.05 NC Malathion 0.0863 0.1 

0.1066 0.0864 

Dieldrin 0.0132 1.5 0.0292 2.1 

0.0134 0.0286 

0.0179 15.5 0.665 1.3 

0.0209 0.674 

E0.0026 NC 0.00549 NC 

<0.001 <0.005 

0.013 6.0 E0.003 NC 

0.0138 <0.027 

Diuron E0.018 0.6 0.014 17.1 

E0.0181 0.0118 

E0.0184 2.7 0.0194 5.8 

E0.0189 0.0183 

E0.0132 10.1 MCPA 0.5944 1.9 

E0.0146 0.5835 

E0.016 13.4 E0.0379 8.1 

E0.0183 E0.0411 

E0.0486 1.6 0.258 0.7 

E0.0494 0.2598 

<0.0793 NC E0.041 4.5 

E0.013 E0.0392 

E0.0156 18.2 Metalaxyl E0.0177 5.0 

E0.013 E0.0186 

Fluometuron E0.0035 9.0 E0.0064 11.6 

E0.0032 E0.0057 

0.1558 2.3 E0.0033 3.1 

0.1595 E0.0032 

Appendixes 71 
Appendix 1. Concentrations and relative percentage differences for pesticides detected in 46 replicate samples from the Mobile 

River Basin, 1999– 2001— Continued 

[μg/L, micrograms per liter; E, estimated; <, less than; NC, not calculated; GC/MS, analyzed by gas chromatography/mass spectrometry; 

HPLC/MS, analyzed by high-performance liquid chromatography/mass spectrometry] 

Pesticide 

Concentration 

in replicates 

(μg/L) 

Relative 

percent 

difference 

Pesticide 

Concentration 

in replicates 

(μg/L) 

Relative 

percent 

difference 

Metalaxyl (Continued) E0.0044 

E0.0047 

6.6 Metolachlor 

(Continued) 

0.00514 

0.00546 

6.0 

E0.0174 11.4 Metribuzin 0.00606 1.7 

E0.0195 E0.00596 

E0.0198 2.0 0.018 1.1 

E0.0194 0.0178 

Metolachlor 0.00527 7.9 0.0072 4.3 

0.00487 0.0069 

0.00553 1.5 Pendimethalin 0.0305 3.2 

0.00545 0.0315 

0.0055 15.4 0.0132 3.0 

0.00642 0.0136 

E0.00075 25.6 0.034 18.2 

E0.00097 0.0408 

0.00672 5.1 0.0202 7.2 

0.00707 0.0188 

E0.00314 7.4 0.0101 7.6 

E0.00338 0.0109 

E0.00332 7.0 0.0246 9.7 

E0.00356 0.0271 

0.00674 13.6 E0.00835 22.8 

0.00772 0.0105 

E0.00364 27.3 0.26 20.1 

E0.00479 0.318 

0.00655 4.8 E0.0128 NC 

0.00624 <0.01 

0.0092 6.5 E0.0082 3.7 

0.00982 E0.0079 

0.0364 3.1 Prometon <0.018 NC 

0.0353 E0.00297 

1.93 65.7 E0.00956 4.7 

0.975 E0.00912 

0.0986 8.2 E0.0129 6.7 

0.107 E0.0138 

0.0913 2.8 E0.0106 16.9 

0.0888 E0.00895 

0.0321 4.0 E0.00412 1.7 

0.0334 E0.00419 

<0.013 NC E0.00836 21.7 

0.0247 E0.0104 

0.0675 7.2 E0.00304 21.7 

0.0628 E0.00378 

0.0862 5.9 E0.00352 19.5 

0.0813 E0.00428 

0.0214 2.4 <0.018 NC 

0.0209 E0.00574 

72 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999–2001 
Appendix 1. Concentrations and relative percentage differences for pesticides detected in 46 replicate samples from the Mobile 

River Basin, 1999– 2001— Continued 

[μg/L, micrograms per liter; E, estimated; <, less than; NC, not calculated; GC/MS, analyzed by gas chromatography/mass spectrometry; 

HPLC/MS, analyzed by high-performance liquid chromatography/mass spectrometry] 

Pesticide 

Concentration 

in replicates 

(μg/L) 

Relative 

percent 

difference 

Pesticide 

Concentration 

in replicates 

(μg/L) 

Relative 

percent 

difference 

Prometon (Continued) E0.0101 5.8 Simazine (Continued) 0.0554 6.7 

E0.0107 0.0518 

<0.018 NC 0.0247 2.0 

E0.00462 0.0242 

E0.00381 5.6 1.62 2.5 

E0.00403 1.58 

E0.00357 40.4 1.99 3.1 

E0.00538 1.93 

E0.00698 1.6 0.0291 29.3 

E0.00687 0.0391 

<0.018 NC 0.0208 15.5 

E0.00877 0.0243 

E0.00925 10.6 0.309 4.3 

E0.00832 0.296 

E0.0027 25.9 1.14 7.6 

E0.00208 1.23 

E0.0063 10.5 0.829 0.8 

E0.007 0.836 

E0.014 37.2 0.304 2.6 

0.0204 0.312 

E0.00717 4.6 0.0976 19.8 

E0.00685 0.119 

Pronamide 0.00547 16.4 <0.011 NC 

0.00464 E0.00715 

0.0045 5.2 0.0851 20.9 

0.00474 0.105 

0.00638 27.7 0.0423 6.8 

0.00843 0.0395 

0.00452 17.6 0.045 9.9 

E0.00379 0.0497 

0.02 NC 0.0288 4.6 

<0.0041 0.0275 

Propanil E0.00458 NC 0.0732 17.0 

<0.011 0.0617 

Propoxur E0.0054 16.0 0.0178 9.1 

E0.0046 0.0195 

Simazine 0.00763 6.4 0.0261 7.1 

0.00716 0.0243 

0.0116 1.7 0.898 NC 

0.0114 <0.011 

7.13 2.4 0.0228 7.7 

7.3 0.0211 

0.668 0.1 0.0201 8.3 

0.667 0.0185 

0.0134 23.3 Sulfometuron-methyl E0.0674 1.8 

E0.0106 E0.0662 

Appendixes 73 
Appendix 1. Concentrations and relative percentage differences for pesticides detected in 46 replicate samples from the Mobile 

River Basin, 1999– 2001— Continued 

[μg/L, micrograms per liter; E, estimated; <, less than; NC, not calculated; GC/MS, analyzed by gas chromatography/mass spectrometry; 

HPLC/MS, analyzed by high-performance liquid chromatography/mass spectrometry] 

Pesticide 

Concentration 

in replicates 

(μg/L) 

Relative 

percent 

difference 

Pesticide 

Concentration 

in replicates 

(μg/L) 

Relative 

percent 

difference 

Tebuthiuron 0.0559 6.1 Triclopyr 0.1161 25.4 

0.0594 E0.0899 

0.0531 8.4 <0.1008 NC 

0.0488 E0.0379 

0.0598 27.2 E0.0958 36.9 

0.0455 0.1391 

E0.00433 5.5 E0.0943 4.9 

E0.0041 E0.099 

E0.00961 16.2 E0.0876 10.5 

0.0113 E0.0789 

0.014 3.6 Trifluralin E0.00373 106.4 

0.0135 E0.00114 

E0.00924 6.7 E0.0012 0.0 

E0.00864 E0.0012 

<0.016 NC 0.00698 13.0 

E0.00726 0.00795 

E0.00603 3.2 E0.00363 4.8 

E0.00584 E0.00346 

E0.00827 17.9 0.00478 1.3 

E0.00691 0.00472 

E0.0065 8.0 0.0135 NC 

E0.006 <0.002 

E0.0075 23.7 E0.00507 3.7 

E0.00591 E0.00526 

0.0131 90.4 <0.009 NC 

0.0347 E0.00265 

E0.0189 23.8 <0.009 NC 

E0.024 E0.00358 

Terbuthylazine E0.00684 63.5 0.00838 NC 

E0.0132 <0.002 

Triallate E0.00201 38.2 

E0.00296 

74 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999–2001 
APPENDIX 2 Summary Statistics for Nutrients, Organic 

Carbon, and Suspended Sediment 

Appendixes 75 
76 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999–2001 Appendix 2. Summary statistics for nutrients, organic carbon, and suspended sediment in surface-water samples collected from the Mobile Riv

[NWIS, National Water Information System; <, less than; --, no value; *, value is estimated by using a log-probability regression to predict values of data below th

NWIS of samples Minimum 95% 75% 

Alabama River at Claiborne, Alabama—January 1999 to December 2001 parameter code Compound Number Maximum Mean 608 Dissolved ammonia as N, mg/L 34 0.09 <0.020 0.026* 0.08 0.03 

623 Dissolved ammonia plus organic nitrogen 31 0.34 0.16 0.225 0.334 0.26 

as N, mg/L 625 Total ammonia plus organic nitrogen as N, 34 0.62 0.28 0.432 0.605 0.49 

mg/L 631 Dissolved nitrite plus nitrate as N, mg/L 34 0.29 <0.050 0.130* 0.25 0.18 

613 Dissolved nitrite as N, mg/L 34 0.019 <0.006 0.006* 0.014 0.005 600 Total nitrogen, mg/L 29 0.87 0.4 0.574 0.825 0.59 666 Dissolved phosphorus as P, mg/L 31 0.05 0.01 0.027 0.049 0.033 671 Dissolved orthophosphate as P, mg/L 34 0.04 <0.010 0.018* 0.04 0.02 665 Total phosphorus as P, mg/L 34 0.173 0.051 0.077 0.146 0.08 681 Dissolved organic carbon, mg/L 31 7 3.3 4.413 6.16 5 689 Suspended organic carbon, mg/L 24 1.3 0.4 0.675 1.3 0.8 70331 Suspended sediment, percent finer than 34 97 35 79.971 96.25 92 

0.062 mm (percentage) 80154 Suspended sediment concentration, mg/L 34 167 2 28.882 132.5 21.75 

NWIS of samples Minimum 95% 75% 

Black Warrior River below Bankhead Lock and Dam near Bessemer, Alabama—January 1999 to D

parameter code Compound Number Maximum Mean 608 Dissolved ammonia as N, mg/L 24 0.14 <0.020 0.043* 0.12 0.06 

623 Dissolved ammonia plus organic nitrogen as N, mg/L 24 0.36 0.11 0.206 0.355 0.248 

625 Total ammonia plus organic nitrogen as N, mg/L 24 0.57 0.14 0.31 0.532 0.36 

631 Dissolved nitrite plus nitrate as N, mg/L 24 1.13 0.05 0.599 1.125 0.885 613 Dissolved nitrite as N, mg/L 24 0.03 <0.010 0.009* 0.027 0.01 600 Total nitrogen, mg/L 23 1.7 0.45 0.932 1.64 1.2 666 Dissolved phosphorus as P, mg/L 24 0.043 <0.004 0.013* 0.029 0.017 671 Dissolved orthophosphate as P, mg/L 24 0.03 <0.010 0.009* 0.02 0.01 665 Total phosphorus as P, mg/L 24 0.137 0.015 0.036 0.119 0.042 681 Dissolved organic carbon, mg/L 23 3.7 1.9 2.583 3.68 2.8 689 Suspended organic carbon, mg/L 23 0.8 0.2 0.522 0.8 0.7 70331 Suspended sediment, percent finer than 

0.062 mm (percentage) 

24 99 58 82.375 98 91.75 

80154 Suspended sediment concentration, mg/L 24 63 2 6.75 51 5 
--

Appendix 2. Summary statistics for nutrients, organic carbon, and suspended sediment in surface-water samples collected from the Mobile Riv[NWIS, National Water Information System; <, less than; --, no value; *, value is estimated by using a log-probability regression to predict values of data below th

NWIS 

of 

samples 

Minimum 95% 75% 

Bogue Chitto Creek near Memphis, Alabama—January 1999 to December 2001 

parameter 

code 

Compound 

Number 

Maximum Mean 

608 Dissolved ammonia as N, mg/L 55 1.63 <0.020 0.088* 0.47 0.07 623 Dissolved ammonia plus organic nitrogen 52 3.2 0.1 0.717 1.915 0.752 

as N, mg/L 

625 Total ammonia plus organic nitrogen as N, 55 4.2 0.45 1.16 3.14 1.2 

mg/L 

631 Dissolved nitrite plus nitrate as N, mg/L 55 7.94 <0.050 1.195* 5 1.65 613 Dissolved nitrite as N, mg/L 55 0.49 <0.006 0.044* 0.155 0.048 600 Total nitrogen, mg/L 37 10 0.81 3.082 9.55 3.95 666 Dissolved phosphorus as P, mg/L 52 0.27 0.009 0.061 0.2 0.092 671 Dissolved orthophosphate as P, mg/L 55 0.23 <0.010 0.046* 0.17 0.07 665 Total phosphorus as P, mg/L 55 2.22 0.037 0.276 1.264 0.32 681 Dissolved organic carbon, mg/L 52 11 4.9 7.754 11 8.775 689 Suspended organic carbon, mg/L 41 4.6 0.3 2.01 4 3.25 70331 Suspended sediment, percent finer than 53 99 18 80.868 99 96 

0.062 mm (percentage) 

80154 Suspended sediment concentration, mg/L 53 2450 3 171.774 933 105 

NWIS 

of 

samples 

Minimum 95% 75% 

Cahaba River at Centreville, Alabama—January 1999 to September 2001 

parameter 

code 

Compound 

Number 

Maximum Mean 

608 Dissolved ammonia as N, mg/L 41 0.05 <0.020 0.015* 0.03 <0.040 623 Dissolved ammonia plus organic nitrogen 

as N, mg/L 

41 0.52 0.07 0.151 0.28 0.17 

625 Total ammonia plus organic nitrogen as N, 

mg/L 

41 1.2 0.11 0.308 0.92 0.34 

631 Dissolved nitrite plus nitrate as N, mg/L 41 0.79 <0.050 0.335* 0.64 0.44 613 Dissolved nitrite as N, mg/L 41 0.01 <0.006 0.006 <0.010 600 Total nitrogen, mg/L 38 1.4 0.31 0.66 1.115 0.812 666 Dissolved phosphorus as P, mg/L 41 0.085 <0.004 0.026* 0.061 0.032 671 Dissolved orthophosphate as P, mg/L 41 0.07 <0.010 0.022* 0.06 0.03 665 Total phosphorus as P, mg/L 41 0.27 0.008 0.068 0.196 0.088 681 Dissolved organic carbon, mg/L 41 9.9 1.5 2.476 4.59 2.6 689 Suspended organic carbon, mg/L 36 5.6 0.2 0.944 5.345 0.975 70331 Suspended sediment, percent finer than 

0.062 mm (percentage) 

40 98 30 86.05 96 92.75 

80154 Suspended sediment concentration, mg/L 40 348 3 38.1 272.7 26.5 

Appendixes 77 
Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999–2001 

Appendix 2. Summary statistics for nutrients, organic carbon, and suspended sediment in surface-water samples collected from the Mobile Riv[NWIS, National Water Information System; <, less than; --, no value; *, value is estimated by using a log-probability regression to predict values of data below th

NWIS 

of 

samples 

Minimum 95% 75% 

Cahaba Valley Creek at Cross Creek Road at Pelham, Alabama—January 1999 to Decembe

parameter 

code 

Compound 

Number 

Maximum Mean 

608 Dissolved ammonia as N, mg/L 74 0.7 <0.020 0.033* 0.09 0.03 623 Dissolved ammonia plus organic nitrogen 71 2 0.05 0.214 0.39 0.22 

as N, mg/L 

625 Total ammonia plus organic nitrogen as N, 74 2.8 0.06 0.328 0.873 0.305 

mg/L 

631 Dissolved nitrite plus nitrate as N, mg/L 74 3.43 0.16 1.497 3.243 2.023 613 Dissolved nitrite as N, mg/L 74 0.019 <0.010 0.008* 0.016 0.008 600 Total nitrogen, mg/L 70 3.7 0.63 1.823 3.5 2.25 666 Dissolved phosphorus as P, mg/L 70 0.42 0.005 0.152 0.34 0.208 671 Dissolved orthophosphate as P, mg/L 74 0.39 0.01 0.134 0.33 0.183 665 Total phosphorus as P, mg/L 73 0.5 0.033 0.182 0.403 0.23 681 Dissolved organic carbon, mg/L 69 6 1.2 2.219 4.55 2.4 689 Suspended organic carbon, mg/L 57 6 <0.200 0.608* 2.1 0.4 70331 Suspended sediment, percent finer than 70 98 68 88.557 97 94 

0.062 mm (percentage) 

80154 Suspended sediment concentration, mg/L 71 243 2 24.732 151.8 17 

NWIS 

of 

samples 

Minimum 95% 75% 

Chattooga River above Gaylesville, Alabama—January 1999 to December 2000 

parameter 

code 

Compound 

Number 

Maximum Mean 

608 Dissolved ammonia as N, mg/L 25 0.09 <0.020 0.038* 0.08 0.06 623 Dissolved ammonia plus organic nitrogen 

as N, mg/L 

25 0.44 0.12 0.254 0.425 0.305 

625 Total ammonia plus organic nitrogen as N, 

mg/L 

25 0.67 0.2 0.366 0.64 0.41 

631 Dissolved nitrite plus nitrate as N, mg/L 25 0.75 0.06 0.377 0.711 0.46 613 Dissolved nitrite as N, mg/L 25 0.042 <0.010 0.009* 0.022 0.01 600 Total nitrogen, mg/L 25 1.1 0.4 0.742 1.07 0.86 666 Dissolved phosphorus as P, mg/L 25 0.54 0.009 0.24 0.531 0.385 671 Dissolved orthophosphate as P, mg/L 25 0.43 0.02 0.205 0.43 0.33 665 Total phosphorus as P, mg/L 24 0.53 0.008 0.257 0.515 0.403 681 Dissolved organic carbon, mg/L 25 6.6 1.7 3.208 5.97 3.95 689 Suspended organic carbon, mg/L 24 1.2 <0.200 0.420* 1.1 0.5 70331 Suspended sediment, percent finer than 

0.062 mm (percentage) 

25 97 16 81.32 97 92.5 

80154 Suspended sediment concentration, mg/L 25 88 2 20.76 87.4 20 

78 
--

Appendix 2. Summary statistics for nutrients, organic carbon, and suspended sediment in surface-water samples collected from the Mobile Riv[NWIS, National Water Information System; <, less than; --, no value; *, value is estimated by using a log-probability regression to predict values of data below th

NWIS 

of 

samples 

Minimum 95% 75% 

Pintlalla Creek at Liberty Church Road near Pintlalla, Alabama—January 1999 to Decembe

parameter 

code 

Compound 

Number 

Maximum Mean 

608 Dissolved ammonia as N, mg/L 24 0.13 <0.020 0.029* 0.07 0.03 623 Dissolved ammonia plus organic nitrogen 24 0.66 0.23 0.363 0.658 0.425 

as N, mg/L 

625 Total ammonia plus organic nitrogen as N, 24 1 0.13 0.514 0.983 0.587 

mg/L 

631 Dissolved nitrite plus nitrate as N, mg/L 24 0.35 <0.050 0.068* 0.17 0.09 613 Dissolved nitrite as N, mg/L 24 0.018 <0.006 0.015 <0.010 600 Total nitrogen, mg/L 11 1.3 0.2 0.675 1.3 0.94 666 Dissolved phosphorus as P, mg/L 24 0.36 0.01 0.05 0.304 0.045 671 Dissolved orthophosphate as P, mg/L 24 0.33 <0.010 0.036* 0.1 0.03 665 Total phosphorus as P, mg/L 24 0.5 0.045 0.115 0.428 0.118 681 Dissolved organic carbon, mg/L 24 16 4.7 8.337 15.75 9.35 689 Suspended organic carbon, mg/L 23 3.5 0.2 0.865 3.38 1 70331 Suspended sediment, percent finer than 24 99 61 87.208 99 93.75 

0.062 mm (percentage) 

80154 Suspended sediment concentration, mg/L 24 100 4 20.375 91.25 17.25 

NWIS 

of 

samples 

Minimum 95% 75% 

Threemile Branch at North Boulevard at Montgomery, Alabama—January 1999 to Septemb

parameter 

code 

Compound 

Number 

Maximum Mean 

608 Dissolved ammonia as N, mg/L 35 0.43 <0.020 0.047* 0.39 0.04 623 Dissolved ammonia plus organic nitrogen 

as N, mg/L 

35 1.3 0.08 0.248 0.892 0.26 

625 Total ammonia plus organic nitrogen as N, 

mg/L 

35 2.2 0.08 0.432 2.04 0.34 

631 Dissolved nitrite plus nitrate as N, mg/L 35 1.26 0.15 0.678 1.204 1.01 613 Dissolved nitrite as N, mg/L 35 0.038 <0.010 0.011* 0.019 0.013 600 Total nitrogen, mg/L 33 2.5 0.46 1.127 2.43 1.3 666 Dissolved phosphorus as P, mg/L 35 0.29 <0.006 0.037* 0.15 0.022 671 Dissolved orthophosphate as P, mg/L 35 0.24 <0.010 0.024* 0.13 0.02 665 Total phosphorus as P, mg/L 35 0.66 0.015 0.097 0.548 0.062 681 Dissolved organic carbon, mg/L 35 17.8 0.9 3.474 15.64 4.6 689 Suspended organic carbon, mg/L 26 2 <0.200 0.421* 1 0.4 70331 Suspended sediment, percent finer than 

0.062 mm (percentage) 

35 97 16 75.886 96.2 91 

80154 Suspended sediment concentration, mg/L 35 1940 1 92.229 821.601 7 

Appendixes 79 
Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999–2001 Appendix 2. Summary statistics for nutrients, organic carbon, and suspended sediment in surface-water samples collected from the Mobile Riv

[NWIS, National Water Information System; <, less than; --, no value; *, value is estimated by using a log-probability regression to predict values of data below th

NWIS of Maximum 95% 75% 

Tombigbee River below Coffeeville Lock and Dam near Coffeeville, Alabama—January 1999 to De

parameter code Compound Number samples Minimum Mean 608 Dissolved ammonia as N, mg/L 34 0.11 <0.020 0.032* 0.06 0.04 

623 Dissolved ammonia plus organic nitrogen as N, mg/L 31 0.66 0.16 0.256 0.468 0.27 625 Total ammonia plus organic nitrogen as N, mg/L 34 3.6 0.25 0.548 1.725 0.507 631 Dissolved nitrite plus nitrate as N, mg/L 34 0.83 <0.050 0.259* 0.56 0.32 613 Dissolved nitrite as N, mg/L 34 0.048 <0.008 0.010* 0.031 0.009 600 Total nitrogen, mg/L 31 3.8 0.4 0.838 2.48 0.85 666 Dissolved phosphorus as P, mg/L 31 0.042 0.008 0.023 0.041 0.033 671 Dissolved orthophosphate as P, mg/L 34 0.03 <0.010 0.017* 0.03 0.02 665 Total phosphorus as P, mg/L 34 0.38 0.04 0.1 0.282 0.119 681 Dissolved organic carbon, mg/L 31 6.7 2.7 4.703 6.46 5.1 689 Suspended organic carbon, mg/L 24 3.3 0.2 0.796 2.85 0.975 70331 Suspended sediment, percent finer than 0.062 mm (percentage) 33 98 53 83.152 96.6 91.5 80154 Suspended sediment concentration, mg/L 33 507 5 69.879 368.4 61.5 

80 
APPENDIX 3 Summary Statistics for Pesticides 

Appendixes 81 
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Appendix 3. Summary statistics for pesticides in surface-water samples collected from the Mobile River Basin , 1999– 2001 

[NWIS, National Water Information System; GC/MS, gas chromatography/mass spectrometry; <, less than; --, no value; *, value is estimated by using a logprobability regression to predict values of data below the detection limit; E, estimated concentration; HPLC/MS, high-performance liquid chromatography/mass 

spectrometry] 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Alabama River at Claiborne, Alabama—January 1999 to December 2001 

parameter code 

Compound (GC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

82660 2,6-diethylaniline 18 <0.003 <0.002 <0.003 <0.003 <0.002 <0.002 <0.002 

49260 Acetochlor 18 <0.004 <0.002 <0.004 <0.004 <0.002 <0.002 <0.002 

46342 Alachlor 18 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 

34253 Alpha-HCH 18 <0.005 <0.002 <0.005 <0.005 <0.002 <0.002 <0.002 

39632 Atrazine 18 0.142 0.017 0.045 0.142 0.056 0.038 0.029 0.017 

82673 Benfluralin 18 <0.010 <0.002 <0.010 <0.010 <0.002 <0.002 <0.002 

04028 Butylate 18 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 

82680 Carbaryl (E) 18 <0.041 <0.003 <0.041 <0.041 <0.003 <0.003 <0.003 

82674 Carbofuran (E) 18 <0.020 <0.003 <0.020 <0.020 <0.010 <0.003 <0.003 

38933 Chlorpyrifos 18 0.005 <0.004 0.005 <0.005 <0.005 <0.004 <0.004 

04041 Cyanazine 18 <0.018 <0.004 <0.018 <0.018 <0.009 <0.004 <0.004 

82682 Dacthal (DCPA) 18 0.002 <0.002 0.002 <0.003 <0.003 <0.002 <0.002 

04040 Deethylatrazine (E) 18 0.01 <0.006 0.006* 0.01 0.006 0.005 0.003 <0.006 

34653 p,p'-DDE 18 <0.006 <0.002 <0.006 <0.006 <0.002 <0.002 <0.002 

39572 Diazinon 18 0.01 <0.002 0.004* 0.01 0.006 0.003 <0.005 <0.002 

39381 Dieldrin 18 <0.005 <0.001 <0.005 <0.005 <0.001 <0.001 <0.001 

82677 Disulfoton 18 <0.021 <0.017 <0.021 <0.021 <0.017 <0.017 <0.017 

82668 EPTC 18 <0.030 <0.002 <0.030 <0.002 <0.002 <0.002 <0.002 

82663 Ethalfluralin 18 <0.009 <0.004 <0.009 <0.009 <0.004 <0.004 <0.004 

82672 Ethoprop 18 <0.005 <0.003 <0.005 <0.005 <0.003 <0.003 <0.003 

04095 Fonofox 18 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 

39341 Lindane 18 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 

82666 Linuron 18 <0.035 <0.002 <0.035 <0.035 <0.002 <0.002 <0.002 

39532 Malathion 18 0.014 <0.005 0.014 <0.027 <0.027 <0.005 <0.005 

82686 Methyl azinphos (E) 18 <0.050 <0.001 <0.050 <0.050 <0.001 <0.001 <0.001 

82667 Methyl parathion 18 <0.006 <0.006 <0.006 <0.006 <0.006 <0.006 <0.006 

39415 Metolachlor 18 0.022 <0.002 0.008* 0.022 0.009 0.007 0.002 <0.013 

82630 Metribuzin 18 0.006 <0.004 0.006 <0.006 <0.004 <0.004 <0.004 

82671 Molinate 18 <0.010 <0.002 <0.010 <0.004 <0.004 <0.002 <0.002 

82684 Napropamide 18 <0.007 <0.003 <0.007 <0.007 <0.003 <0.003 <0.003 

39542 Parathion 18 <0.007 <0.004 <0.007 <0.007 <0.004 <0.004 <0.004 

82669 Pebulate 18 <0.004 <0.002 <0.004 <0.004 <0.002 <0.002 <0.002 

82683 Pendimethalin 18 <0.010 <0.004 <0.010 <0.010 <0.010 <0.004 <0.004 

82687 cis-Permethrin 18 <0.006 <0.005 <0.006 <0.006 <0.005 <0.005 <0.005 

82664 Phorate 18 <0.011 <0.002 <0.011 <0.011 <0.002 <0.002 <0.002 

04037 Prometon 18 0.009 <0.015 0.005* 0.009 0.006 0.003 <0.018 <0.015 

82676 Pronamide 18 0.005 <0.003 0.005 <0.004 <0.004 <0.003 <0.003 

04024 Propachlor 18 <0.010 <0.007 <0.010 <0.010 <0.007 <0.007 <0.007 

82679 Propanil 18 <0.011 <0.004 <0.011 <0.011 <0.004 <0.004 <0.004 

82685 Propargite 18 <0.200 <0.013 <0.200 <0.023 <0.023 <0.013 <0.013 

04035 Simazine 18 0.122 0.014 0.045 0.122 0.06 0.037 0.021 0.014 

82670 Tebuthiuron 18 0.011 <0.010 0.008* 0.011 0.008 <0.016 <0.016 <0.010 

82 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999–2001 
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Appendix 3. Summary statistics for pesticides in surface-water samples collected from the Mobile River Basin , 1999– 2001—Continued 

[NWIS, National Water Information System; GC/MS, gas chromatography/mass spectrometry; <, less than; --, no value; *, value is estimated by using a logprobability regression to predict values of data below the detection limit; E, estimated concentration; HPLC/MS, high-performance liquid chromatography/mass 

spectrometry] 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Alabama River at Claiborne, Alabama—January 1999 to December 2001 (Continued) 

parameter code 

Compound (GC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

82665 Terbacil (E) 18 <0.040 <0.007 <0.040 <0.034 <0.007 <0.007 <0.007 

82675 Terbufos 18 <0.017 <0.013 <0.017 <0.017 <0.013 <0.013 <0.013 

82681 Thiobencarb 18 <0.005 <0.002 <0.005 <0.005 <0.002 <0.002 <0.002 

82678 Triallate 18 <0.010 <0.001 <0.010 <0.002 <0.002 <0.001 <0.001 

82661 Trifluralin 18 0.014 <0.002 0.014 <0.009 <0.009 <0.002 <0.002 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Alabama River at Claiborne, Alabama—January 2000 to December 2001 

parameter code Compound (HPLC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

39732 2,4-D 9 0.127 <0.077 0.068* 0.127 0.064 0.042 <0.077 <0.077 

50470 2,4-D methyl ester 9 <0.086 <0.086 <0.086 <0.086 <0.086 <0.086 <0.086 

38746 2,4-DB (E) 9 <0.054 <0.054 <0.054 <0.054 <0.054 <0.054 <0.054 

50355 2-hydroxyatrazine (E) 9 0.014 <0.193 0.014 <0.193 <0.193 <0.193 <0.193 

61692 3,4-chlorophenyl-1- 9 <0.091 <0.091 <0.091 <0.091 <0.091 <0.091 <0.091 

methyl urea 

49308 3-hydroxycarbofuran 9 <0.062 <0.062 <0.062 <0.062 <0.062 <0.062 <0.062 

50295 3-ketocarbofuran (E) 9 <0.072 <0.072 <0.072 <0.072 <0.072 <0.072 <0.072 

49315 Acifluorfen 9 <0.062 <0.062 <0.062 <0.062 <0.062 <0.062 <0.062 

49312 Aldicarb (E) 9 <0.082 <0.082 <0.082 <0.082 <0.082 <0.082 <0.082 

49313 Aldicarb sulfone (E) 9 <0.160 <0.160 <0.160 <0.160 <0.160 <0.160 <0.160 

49314 Aldicarb sulfoxide (E) 8 <0.027 <0.027 <0.027 <0.027 <0.027 <0.027 <0.027 

50299 Bendiocarb 9 <0.061 <0.061 <0.061 <0.061 <0.061 <0.061 <0.061 

50300 Benomyl 9 <0.022 <0.022 <0.022 <0.022 <0.022 <0.022 <0.022 

61693 Bensulfuron-methyl 9 <0.048 <0.048 <0.048 <0.048 <0.048 <0.048 <0.048 

38711 Bentazon (E) 9 <0.019 <0.019 <0.019 <0.019 <0.019 <0.019 <0.019 

04029 Bromacil (E) 9 <0.081 <0.081 <0.081 <0.081 <0.081 <0.081 <0.081 

49311 Bromoxynil (E) 9 <0.057 <0.057 <0.057 <0.057 <0.057 <0.057 <0.057 

50305 Caffeine 9 0.027 <0.080 0.027 0.023 <0.080 <0.080 <0.080 

49310 Carbaryl 9 <0.063 <0.063 <0.063 <0.063 <0.063 <0.063 <0.063 

49309 Carbofuran 9 <0.057 <0.057 <0.057 <0.057 <0.057 <0.057 <0.057 

61188 Chloramben, methyl 9 0.045 <0.114 0.045 <0.114 <0.114 <0.114 <0.114 

ester (E) 

50306 Chlorimuron, ethyl 9 <0.037 <0.037 <0.037 <0.037 <0.037 <0.037 <0.037 

49306 Chlorothalonil (E) 9 <0.049 <0.049 <0.049 <0.049 <0.049 <0.049 <0.049 

49305 Clopyralid 9 <0.041 <0.041 <0.041 <0.041 <0.041 <0.041 <0.041 

04031 Cycloate (E) 9 <0.054 <0.054 <0.054 <0.054 <0.054 <0.054 <0.054 

49304 Dacthal mono-acid 9 <0.072 <0.072 <0.072 <0.072 <0.072 <0.072 <0.072 

04039 Deethyldeisopropyl- 9 0.019 <0.060 0.019 <0.060 <0.060 <0.060 <0.060 

atrazine (E) 

04038 Deisopropylatrazine (E) 9 0.019 <0.074 0.019 0.008 <0.074 <0.074 <0.074 

38442 Dicamba 9 <0.096 <0.096 <0.096 <0.096 <0.096 <0.096 <0.096 

49302 Dichlorprop 9 <0.050 <0.050 <0.050 <0.050 <0.050 <0.050 <0.050 

49301 Dinoseb 9 <0.043 <0.043 <0.043 <0.043 <0.043 <0.043 <0.043 

04033 Diphenamid 9 <0.058 <0.058 <0.058 <0.058 <0.058 <0.058 <0.058 

Appendixes 83 
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Appendix 3. Summary statistics for pesticides in surface-water samples collected from the Mobile River Basin , 1999– 2001—Continued 

[NWIS, National Water Information System; GC/MS, gas chromatography/mass spectrometry; <, less than; --, no value; *, value is estimated by using a logprobability regression to predict values of data below the detection limit; E, estimated concentration; HPLC/MS, high-performance liquid chromatography/mass 

spectrometry] 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Alabama River at Claiborne, Alabama—January 2000 to December 2001 (Continued) 

parameter code 

Compound (HPLC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

49300 

49297 

61694 

38811 

50356 

50407 

61695 

38478 

38482 

38487 

50359 

38501 

49296 

61696 

61697 

49294 

50364 

49293 

49292 

38866 

50410 

49291 

49236 

50471 

38538 

38548 

50337 

04032 

61159 

49235 

Diuron 

Fenuron 

Flumetsulam (E) 

Fluometuron 

Imazaquin (E) 

Imazethapyr (E) 

Imidacloprid 

Linuron 

MCPA

MCPB (E) 

Metalaxyl 

Methiocarb (E) 

Methomyl (E) 

Methomyl oxime (E) 

Metsulfuron-methyl (E) 

Neburon 

Nicosulfuron 

Norflurazon (E) 

Oryzalin 

Oxamyl 

Oxamyl oxime (E) 

Picloram 

Propham 

Propiconazole 

Propoxur 

Siduron 

Sulfometruron-methyl 

Terbacil (E) 

Tribenuron-methyl (E) 

Triclopyr 

9 0.032 

9 <0.073 

9 <0.087 

9 0.006 

9 <0.103 

7 <0.088 

9 <0.106 

9 <0.069 

9 <0.058 

9 <0.062 

9 <0.057 

9 <0.079 

9 <0.077 

9 <0.010 

9 0.045 

9 <0.075 

9 <0.065 

9 <0.077 

9 <0.071 

9 <0.016 

9 <0.064 

9 <0.071 

9 <0.072 

9 <0.064 

9 <0.059 

9 <0.093 

9 <0.039 

9 <0.095 

8 <0.068 

9 <0.101 

<0.079 

<0.073 

<0.087 

<0.062 

<0.103 

<0.088 

<0.106 

<0.069 

<0.058 

<0.062 

<0.057 

<0.079 

<0.077 

<0.010 

<0.114 

<0.075 

<0.065 

<0.077 

<0.071 

<0.016 

<0.064 

<0.071 

<0.072 

<0.064 

<0.059 

<0.093 

<0.039 

<0.095 

<0.068 

<0.101 

0.020* 0.032 

<0.073 

<0.087 

0.006 

<0.103 

<0.088 

<0.106 

<0.069 

<0.058 

<0.062 

<0.057 

<0.079 

<0.077 

<0.010 

0.045 

<0.075 

<0.065 

<0.077 

<0.071 

<0.016 

<0.064 

<0.071 

<0.072 

<0.064 

<0.059 

<0.093 

<0.039 

<0.095 

<0.068 

<0.101 

0.021 

<0.073 

<0.087 

<0.062 

<0.103 

<0.088 

<0.106 

<0.069 

<0.058 

<0.062 

<0.057 

<0.079 

<0.077 

<0.010 

<0.114 

<0.075 

<0.065 

<0.077 

<0.071 

<0.016 

<0.064 

<0.071 

<0.072 

<0.064 

<0.059 

<0.093 

<0.039 

<0.095 

<0.068 

<0.101 

0.016 

<0.073 

<0.087 

<0.062 

<0.103 

<0.088 

<0.106 

<0.069 

<0.058 

<0.062 

<0.057 

<0.079 

<0.077 

<0.010 

<0.114 

<0.075 

<0.065 

<0.077 

<0.071 

<0.016 

<0.064 

<0.071 

<0.072 

<0.064 

<0.059 

<0.093 

<0.039 

<0.095 

<0.068 

<0.101 

0.013 

<0.073 

<0.087 

<0.062 

<0.103 

<0.088 

<0.106 

<0.069 

<0.058 

<0.062 

<0.057 

<0.079 

<0.077 

<0.010 

<0.114 

<0.075 

<0.065 

<0.077 

<0.071 

<0.016 

<0.064 

<0.071 

<0.072 

<0.064 

<0.059 

<0.093 

<0.039 

<0.095 

<0.068 

<0.101 

<0.079 

<0.073 

<0.087 

<0.062 

<0.103 

<0.088 

<0.106 

<0.069 

<0.058 

<0.062 

<0.057 

<0.079 

<0.077 

<0.010 

<0.114 

<0.075 

<0.065 

<0.077 

<0.071 

<0.016 

<0.064 

<0.071 

<0.072 

<0.064 

<0.059 

<0.093 

<0.039 

<0.095 

<0.068 

<0.101 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Black Warrior River below Bankhead Lock and Dam near Bessemer, Alabama—January 1999 to December 2000 

parameter code 

Compound (GC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

82660 2,6-diethylaniline 9 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 

49260 Acetochlor 9 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 

46342 Alachlor 9 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 

34253 Alpha-HCH 9 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 

39632 Atrazine 9 0.152 0.026 0.05 0.152 0.048 0.038 0.03 0.026 

82673 Benfluralin 9 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 

04028 Butylate 9 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 

82680 Carbaryl (E) 9 0.01 <0.003 0.01 0.007 <0.003 <0.003 <0.003 

82674 Carbofuran (E) 9 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 

38933 Chlorpyrifos 9 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 

84 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999–2001 
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Appendix 3. Summary statistics for pesticides in surface-water samples collected from the Mobile River Basin , 1999– 2001—Continued 

[NWIS, National Water Information System; GC/MS, gas chromatography/mass spectrometry; <, less than; --, no value; *, value is estimated by using a logprobability regression to predict values of data below the detection limit; E, estimated concentration; HPLC/MS, high-performance liquid chromatography/mass 

spectrometry] 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Black Warrior River below Bankhead Lock and Dam near Bessemer, Alabama— 

January 1999 to December 2000 (Continued) 

parameter code 

Compound (GC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

04041 Cyanazine 9 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 

82682 Dacthal (DCPA) 9 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 

04040 Deethylatrazine (E) 9 0.01 0.004 0.008 0.01 0.01 0.008 0.007 0.004 

34653 p,p'-DDE 9 0.004 <0.006 0.004 <0.006 <0.006 <0.006 <0.006 

39572 Diazinon 9 0.011 <0.002 0.003* 0.011 0.004 0.002 <0.002 <0.002 

39381 Dieldrin 9 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 

82677 Disulfoton 9 <0.017 <0.017 <0.017 <0.017 <0.017 <0.017 <0.017 

82668 EPTC 9 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 

82663 Ethalfluralin 9 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 

82672 Ethoprop 9 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 

04095 Fonofox 9 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 

39341 Lindane 9 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 

82666 Linuron 9 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 

39532 Malathion 9 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 

82686 Methyl azinphos (E) 9 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 

82667 Methyl parathion 9 <0.006 <0.006 <0.006 <0.006 <0.006 <0.006 <0.006 

39415 Metolachlor 9 0.022 0.001 0.006 0.022 0.006 0.005 0.003 0.001 

82630 Metribuzin 9 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 

82671 Molinate 9 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 

82684 Napropamide 9 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 

39542 Parathion 9 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 

82669 Pebulate 9 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 

82683 Pendimethalin 9 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 

82687 cis-Permethrin 9 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 

82664 Phorate 9 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 

04037 Prometon 9 0.01 <0.018 0.007* 0.01 0.008 0.007 0.005 <0.018 

82676 Pronamide 9 0.003 <0.003 0.003 <0.003 <0.003 <0.003 <0.003 

04024 Propachlor 9 <0.007 <0.007 <0.007 <0.007 <0.007 <0.007 <0.007 

82679 Propanil 9 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 

82685 Propargite 8 <0.100 <0.013 <0.100 <0.013 <0.013 <0.013 <0.013 

04035 Simazine 9 0.03 0.008 0.017 0.03 0.022 0.015 0.011 0.008 

82670 Tebuthiuron 9 0.03 0.01 0.017 0.03 0.019 0.016 0.014 0.01 

82665 Terbacil (E) 9 <0.007 <0.007 <0.007 <0.007 <0.007 <0.007 <0.007 

82675 Terbufos 9 <0.013 <0.013 <0.013 <0.013 <0.013 <0.013 <0.013 

82681 Thiobencarb 9 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 

82678 Triallate 9 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 

82661 Trifluralin 9 0.003 <0.002 0.003 <0.002 <0.002 <0.002 <0.002 

Appendixes 85 
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Appendix 3. Summary statistics for pesticides in surface-water samples collected from the Mobile River Basin , 1999– 2001—Continued 

[NWIS, National Water Information System; GC/MS, gas chromatography/mass spectrometry; <, less than; --, no value; *, value is estimated by using a logprobability regression to predict values of data below the detection limit; E, estimated concentration; HPLC/MS, high-performance liquid chromatography/mass 

spectrometry] 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Bogue Chitto Creek near Memphis, Alabama—January 1999 to December 2001 

parameter code 

Compound (GC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

82660 2,6-diethylaniline 52 <0.003 <0.002 <0.003 <0.003 <0.003 <0.002 <0.002 

49260 Acetochlor 52 <0.007 <0.002 <0.004 <0.004 <0.002 <0.002 <0.002 

46342 Alachlor 52 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 

34253 Alpha-HCH 52 <0.005 <0.002 <0.005 <0.005 <0.002 <0.002 <0.002 

39632 Atrazine 52 201 0.038 13.415 152.8 3.715 0.535 0.105 0.047 

82673 Benfluralin 52 0.001 <0.002 <0.010 <0.010 <0.002 <0.002 <0.002 

04028 Butylate 52 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 

82680 Carbaryl (E) 52 0.035 <0.003 0.002* 0.008 <0.041 <0.003 <0.003 <0.003 

82674 Carbofuran (E) 52 <0.040 <0.003 <0.020 <0.020 <0.003 <0.003 <0.003 

38933 Chlorpyrifos 52 0.213 <0.004 0.017* 0.182 0.005 <0.005 <0.004 <0.004 

04041 Cyanazine 52 5.54 <0.004 0.249* 1.03 0.082 0.008 <0.018 <0.004 

82682 Dacthal (DCPA) 52 0.002 <0.002 <0.003 <0.003 <0.002 <0.002 <0.002 

04040 Deethylatrazine (E) 52 2.33 0.005 0.398 1.858 0.449 0.123 0.036 0.022 

34653 p,p'-DDE 52 <0.006 <0.002 <0.006 <0.006 <0.006 <0.002 <0.002 

39572 Diazinon 52 0.011 <0.002 0.001* 0.005 <0.005 <0.002 <0.002 <0.002 

39381 Dieldrin 52 <0.005 <0.001 <0.005 <0.005 <0.001 <0.001 <0.001 

82677 Disulfoton 52 <0.021 <0.017 <0.021 <0.021 <0.017 <0.017 <0.017 

82668 EPTC 52 <0.040 <0.002 <0.013 <0.002 <0.002 <0.002 <0.002 

82663 Ethalfluralin 52 <0.009 <0.004 <0.009 <0.009 <0.004 <0.004 <0.004 

82672 Ethoprop 52 <0.005 <0.003 <0.005 <0.005 <0.003 <0.003 <0.003 

04095 Fonofox 52 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 

39341 Lindane 52 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 

82666 Linuron 52 <0.035 <0.002 <0.035 <0.035 <0.002 <0.002 <0.002 

39532 Malathion 52 0.025 <0.005 0.015 <0.027 <0.005 <0.005 <0.005 

82686 Methyl azinphos (E) 52 <0.050 <0.001 <0.050 <0.050 <0.001 <0.001 <0.001 

82667 Methyl parathion 52 <0.006 <0.006 <0.006 <0.006 <0.006 <0.006 <0.006 

39415 Metolachlor 52 9.21 0.002 0.438 1.845 0.343 0.046 0.024 0.01 

82630 Metribuzin 52 0.319 <0.004 0.089 <0.006 <0.004 <0.004 <0.004 

82671 Molinate 52 13.9 <0.002 <0.020 <0.004 <0.004 <0.004 <0.002 

82684 Napropamide 52 <0.007 <0.003 <0.007 <0.007 <0.003 <0.003 <0.003 

39542 Parathion 52 <0.007 <0.004 <0.007 <0.007 <0.004 <0.004 <0.004 

82669 Pebulate 52 <0.021 <0.002 <0.004 <0.004 <0.004 <0.002 <0.002 

82683 Pendimethalin 52 0.26 <0.004 0.014* 0.069 <0.011 <0.004 <0.004 <0.004 

82687 cis-Permethrin 52 <0.030 <0.005 <0.006 <0.006 <0.005 <0.005 <0.005 

82664 Phorate 52 0.017 <0.002 <0.011 <0.011 <0.002 <0.002 <0.002 

04037 Prometon 52 <0.018 <0.015 <0.018 <0.018 <0.018 <0.015 <0.015 

82676 Pronamide 52 0.02 <0.003 <0.004 <0.004 <0.003 <0.003 <0.003 

04024 Propachlor 52 <0.010 <0.007 <0.010 <0.010 <0.007 <0.007 <0.007 

82679 Propanil 52 0.005 <0.004 <0.011 <0.011 <0.004 <0.004 <0.004 

82685 Propargite 51 <0.130 <0.013 <0.090 <0.023 <0.013 <0.013 <0.013 

04035 Simazine 51 0.898 <0.005 0.045* 0.081 0.033 0.023 <0.011 <0.005 

82670 Tebuthiuron 52 0.087 <0.010 0.009* 0.013 0.007 <0.016 <0.010 <0.010 

82665 Terbacil (E) 52 0.023 <0.007 <0.034 <0.034 <0.007 <0.007 <0.007 

86 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999–2001 
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Appendix 3. Summary statistics for pesticides in surface-water samples collected from the Mobile River Basin , 1999– 2001—Continued 

[NWIS, National Water Information System; GC/MS, gas chromatography/mass spectrometry; <, less than; --, no value; *, value is estimated by using a logprobability regression to predict values of data below the detection limit; E, estimated concentration; HPLC/MS, high-performance liquid chromatography/mass 

spectrometry] 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Bogue Chitto Creek near Memphis, Alabama—January 1999 to December 2001 (Continued) 

parameter code 

Compound (GC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

82675 Terbufos 52 <0.017 <0.013 <0.017 <0.017 <0.013 <0.013 <0.013 

82681 Thiobencarb 52 <0.005 <0.002 <0.005 <0.005 <0.002 <0.002 <0.002 

82678 Triallate 52 <0.002 <0.001 <0.002 <0.002 <0.001 <0.001 <0.001 

82661 Trifluralin 52 0.039 <0.002 0.004* 0.021 <0.009 <0.002 <0.002 <0.002 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Bogue Chitto Creek near Memphis, Alabama—January 2000 to December 2001 

parameter code 

Compound (HPLC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

39732 2,4-D 20 2.29 <0.022 0.216* 0.529 0.097 0.028 <0.077 <0.022 

50470 2,4-D methyl ester 20 0.388 <0.009 0.069 <0.086 <0.086 <0.086 <0.009 

38746 2,4-DB (E) 20 <0.054 <0.016 <0.054 <0.054 <0.054 <0.054 <0.016 

50355 2-hydroxyatrazine (E) 20 3.42 <0.193 0.800* 2.085 1.048 0.46 0.162 <0.193 

61692 3,4-chlorophenyl-1- 20 0.037 <0.024 <0.091 <0.091 <0.091 <0.091 <0.024 

methyl urea 

49308 3-hydroxycarbofuran 20 <0.062 <0.006 <0.062 <0.062 <0.062 <0.062 <0.006 

50295 3-ketocarbofuran (E) 20 <1.500 <0.072 <1.500 <0.072 <0.072 <0.072 <0.072 

49315 Acifluorfen 20 0.046 <0.007 0.027 <0.062 <0.062 <0.062 <0.007 

49312 Aldicarb (E) 20 <0.082 <0.040 <0.082 <0.082 <0.082 <0.082 <0.040 

49313 Aldicarb sulfone (E) 20 <0.160 <0.020 <0.160 <0.160 <0.160 <0.160 <0.020 

49314 Aldicarb sulfoxide (E) 20 <0.027 <0.008 <0.027 <0.027 <0.027 <0.027 <0.008 

50299 Bendiocarb 20 0.01 <0.025 <0.061 <0.061 <0.061 <0.061 <0.025 

50300 Benomyl 20 <0.022 <0.004 <0.022 <0.022 <0.022 <0.022 <0.004 

61693 Bensulfuron-methyl 20 <0.048 <0.016 <0.048 <0.048 <0.048 <0.048 <0.016 

38711 Bentazon (E) 20 0.053 <0.011 0.010* 0.016 <0.019 <0.019 <0.019 <0.011 

04029 Bromacil (E) 20 <0.081 <0.033 <0.081 <0.081 <0.081 <0.081 <0.033 

49311 Bromoxynil (E) 20 <0.057 <0.017 <0.057 <0.057 <0.057 <0.057 <0.017 

50305 Caffeine 20 0.039 <0.010 0.038 <0.080 <0.080 <0.080 <0.010 

49310 Carbaryl 20 0.004 <0.028 <0.063 <0.063 <0.063 <0.063 <0.028 

49309 Carbofuran 20 <0.057 <0.006 <0.057 <0.057 <0.057 <0.057 <0.006 

61188 Chloramben, methyl 20 0.036 <0.018 <0.114 <0.114 <0.114 <0.114 <0.018 

ester (E) 

50306 Chlorimuron, ethyl 20 <0.037 <0.010 <0.037 <0.037 <0.037 <0.037 <0.010 

49306 Chlorothalonil (E) 20 <0.049 <0.035 <0.049 <0.049 <0.049 <0.049 <0.035 

49305 Clopyralid 20 <0.041 <0.014 <0.041 <0.041 <0.041 <0.041 <0.014 

04031 Cycloate (E) 20 <0.054 <0.013 <0.054 <0.054 <0.054 <0.054 <0.013 

49304 Dacthal mono-acid 20 0.107 <0.012 <0.072 <0.072 <0.072 <0.072 <0.012 

04039 Deethyldeisopropyl- 20 0.127 <0.010 0.043* 0.078 0.049 <0.060 <0.060 <0.010 

atrazine (E) 

04038 Deisopropylatrazine (E) 20 0.64 <0.074 0.108* 0.391 0.103 0.018 <0.074 <0.074 

38442 Dicamba 20 0.071 <0.013 <0.096 <0.096 <0.096 <0.096 <0.013 

49302 Dichlorprop 20 <0.050 <0.014 <0.050 <0.050 <0.050 <0.050 <0.014 

49301 Dinoseb 20 <0.043 <0.012 <0.043 <0.043 <0.043 <0.043 <0.012 

04033 Diphenamid 20 <0.058 <0.026 <0.058 <0.058 <0.058 <0.058 <0.026 

49300 Diuron 20 0.156 <0.015 0.022* 0.049 <0.079 <0.079 <0.079 <0.015 

49297 Fenuron 20 <0.073 <0.032 <0.073 <0.073 <0.073 <0.073 <0.032 

Appendixes 87 
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Appendix 3. Summary statistics for pesticides in surface-water samples collected from the Mobile River Basin , 1999– 2001—Continued 

[NWIS, National Water Information System; GC/MS, gas chromatography/mass spectrometry; <, less than; --, no value; *, value is estimated by using a logprobability regression to predict values of data below the detection limit; E, estimated concentration; HPLC/MS, high-performance liquid chromatography/mass 

spectrometry] 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Bogue Chitto Creek near Memphis, Alabama—January 2000 to December 2001 (Continued) 

parameter code 

Compound (HPLC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

61694 Flumetsulam (E) 20 0.056 <0.011 0.01 <0.087 <0.087 <0.087 <0.011 

38811 Fluometuron 19 0.156 <0.031 0.039* 0.156 0.042 0.015 0.007 <0.062 

50356 Imazaquin (E) 19 0.571 <0.016 0.051* 0.571 0.003 <0.103 <0.103 <0.016 

50407 Imazethapyr (E) 18 0.103 <0.017 0.103 <0.088 <0.088 <0.088 <0.017 

61695 Imidacloprid 20 <0.106 <0.007 <0.106 <0.106 <0.106 <0.106 <0.007 

38478 Linuron 20 <0.069 <0.014 <0.069 <0.069 <0.069 <0.069 <0.014 

38482 MCPA 20 <0.058 <0.016 <0.058 <0.058 <0.058 <0.058 <0.016 

38487 MCPB (E) 20 <0.062 <0.015 <0.062 <0.062 <0.062 <0.062 <0.015 

50359 Metalaxyl 20 0.039 <0.020 0.014* 0.02 0.005 <0.057 <0.057 <0.020 

38501 Methiocarb (E) 20 <0.079 <0.008 <0.079 <0.079 <0.079 <0.079 <0.008 

49296 Methomyl (E) 20 0.004 <0.004 <0.077 <0.077 <0.077 <0.077 <0.004 

61696 Methomyl oxime (E) 20 <0.200 <0.010 <0.011 <0.010 <0.010 <0.010 <0.010 

61697 Metsulfuron-methyl (E) 20 0.007 <0.025 <0.114 <0.114 <0.114 <0.114 <0.025 

49294 Neburon 20 <0.075 <0.012 <0.075 <0.075 <0.075 <0.075 <0.012 

50364 Nicosulfuron 20 0.216 <0.013 0.012 <0.065 <0.065 <0.065 <0.013 

49293 Norflurazon (E) 20 <0.077 <0.016 <0.077 <0.077 <0.077 <0.077 <0.016 

49292 Oryzalin 20 <0.071 <0.018 <0.071 <0.071 <0.071 <0.071 <0.018 

38866 Oxamyl 20 <0.016 <0.012 <0.016 <0.016 <0.016 <0.016 <0.012 

50410 Oxamyl oxime (E) 19 <0.064 <0.013 <0.064 <0.064 <0.064 <0.064 <0.013 

49291 Picloram 20 <0.071 <0.020 <0.071 <0.071 <0.071 <0.071 <0.020 

49236 Propham 20 <0.072 <0.010 <0.072 <0.072 <0.072 <0.072 <0.010 

50471 Propiconazole 20 <0.064 <0.002 <0.064 <0.064 <0.064 <0.064 <0.002 

38538 Propoxur 20 <0.059 <0.008 <0.059 <0.059 <0.059 <0.059 <0.008 

38548 Siduron 20 <0.093 <0.017 <0.093 <0.093 <0.093 <0.093 <0.017 

50337 Sulfometruron-methyl 20 <0.039 <0.009 <0.039 <0.039 <0.039 <0.039 <0.009 

04032 Terbacil (E) 20 <0.095 <0.010 <0.095 <0.095 <0.095 <0.095 <0.010 

61159 Tribenuron-methyl (E) 19 <0.068 <0.009 <0.068 <0.068 <0.068 <0.068 <0.009 

49235 Triclopyr 20 0.094 <0.022 0.088 <0.101 <0.101 <0.101 <0.022 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Cahaba River at Centreville, Alabama—January 1999 to September 2001 

parameter code 

Compound (GC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

82660 2,6-diethylaniline 40 <0.003 <0.002 <0.003 <0.003 <0.003 <0.003 <0.002 

49260 Acetochlor 40 <0.004 <0.002 <0.004 <0.002 <0.002 <0.002 <0.002 

46342 Alachlor 40 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 

34253 Alpha-HCH 40 <0.005 <0.002 <0.005 <0.002 <0.002 <0.002 <0.002 

39632 Atrazine 41 0.364 0.007 0.052 0.324 0.058 0.02 0.012 0.008 

82673 Benfluralin 40 0.003 <0.002 <0.010 <0.002 <0.002 <0.002 <0.002 

04028 Butylate 40 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 

82680 Carbaryl (E) 40 0.028 <0.003 0.004* 0.008 <0.041 <0.003 <0.003 <0.003 

82674 Carbofuran (E) 40 <0.020 <0.003 <0.020 <0.003 <0.003 <0.003 <0.003 

38933 Chlorpyrifos 40 0.025 <0.004 0.005* 0.017 0.005 <0.005 <0.004 <0.004 

04041 Cyanazine 40 <0.018 <0.004 <0.018 <0.004 <0.004 <0.004 <0.004 

82682 Dacthal (DCPA) 40 <0.003 <0.002 <0.003 <0.002 <0.002 <0.002 <0.002 

88 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999–2001 
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Appendix 3. Summary statistics for pesticides in surface-water samples collected from the Mobile River Basin , 1999– 2001—Continued 

[NWIS, National Water Information System; GC/MS, gas chromatography/mass spectrometry; <, less than; --, no value; *, value is estimated by using a logprobability regression to predict values of data below the detection limit; E, estimated concentration; HPLC/MS, high-performance liquid chromatography/mass 

spectrometry] 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Cahaba River at Centreville, Alabama—January 1999 to September 2001 (Continued) 

parameter code 

Compound (GC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

04040 Deethylatrazine (E) 40 0.021 <0.006 0.007* 0.017 0.008 0.005 0.004 <0.006 

34653 p,p'-DDE 40 0.003 <0.002 <0.007 <0.006 <0.006 <0.006 <0.002 

39572 Diazinon 40 0.051 <0.002 0.008* 0.025 0.01 0.003 <0.002 <0.002 

39381 Dieldrin 40 <0.005 <0.001 <0.005 <0.001 <0.001 <0.001 <0.001 

82677 Disulfoton 40 <0.021 <0.017 <0.021 <0.017 <0.017 <0.017 <0.017 

82668 EPTC 40 <0.025 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 

82663 Ethalfluralin 40 <0.009 <0.004 <0.009 <0.004 <0.004 <0.004 <0.004 

82672 Ethoprop 40 <0.005 <0.003 <0.005 <0.003 <0.003 <0.003 <0.003 

04095 Fonofox 40 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 

39341 Lindane 40 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 

82666 Linuron 40 <0.035 <0.002 <0.035 <0.002 <0.002 <0.002 <0.002 

39532 Malathion 40 0.223 <0.005 <0.027 <0.005 <0.005 <0.005 <0.005 

82686 Methyl azinphos (E) 40 <0.050 <0.001 <0.050 <0.001 <0.001 <0.001 <0.001 

82667 Methyl parathion 40 <0.006 <0.006 <0.006 <0.006 <0.006 <0.006 <0.006 

39415 Metolachlor 40 0.013 <0.002 0.002* 0.007 <0.013 <0.002 <0.002 <0.002 

82630 Metribuzin 40 <0.006 <0.004 <0.006 <0.004 <0.004 <0.004 <0.004 

82671 Molinate 40 0.003 <0.002 <0.004 <0.004 <0.004 <0.004 <0.002 

82684 Napropamide 40 <0.007 <0.003 <0.007 <0.003 <0.003 <0.003 <0.003 

39542 Parathion 40 <0.007 <0.004 <0.007 <0.004 <0.004 <0.004 <0.004 

82669 Pebulate 40 <0.004 <0.002 <0.004 <0.004 <0.004 <0.004 <0.002 

82683 Pendimethalin 40 0.025 <0.004 0.004* 0.012 <0.010 <0.004 <0.004 <0.004 

82687 cis-Permethrin 40 <0.006 <0.005 <0.006 <0.005 <0.005 <0.005 <0.005 

82664 Phorate 40 <0.011 <0.002 <0.011 <0.002 <0.002 <0.002 <0.002 

04037 Prometon 40 0.011 <0.015 0.006* 0.008 0.006 0.004 <0.018 <0.015 

82676 Pronamide 40 0.033 <0.003 0.004* 0.01 0.004 <0.003 <0.003 <0.003 

04024 Propachlor 40 <0.010 <0.007 <0.010 <0.007 <0.007 <0.007 <0.007 

82679 Propanil 40 <0.011 <0.004 <0.011 <0.004 <0.004 <0.004 <0.004 

82685 Propargite 37 <0.090 <0.013 <0.040 <0.023 <0.013 <0.013 <0.013 

04035 Simazine 40 1.14 0.008 0.15 0.821 0.161 0.038 0.021 0.01 

82670 Tebuthiuron 41 0.023 <0.010 0.010* 0.019 0.011 0.01 0.007 <0.010 

82665 Terbacil (E) 40 <0.034 <0.007 <0.034 <0.007 <0.007 <0.007 <0.007 

82675 Terbufos 40 <0.017 <0.013 <0.017 <0.013 <0.013 <0.013 <0.013 

82681 Thiobencarb 40 <0.005 <0.002 <0.005 <0.002 <0.002 <0.002 <0.002 

82678 Triallate 40 <0.002 <0.001 <0.002 <0.001 <0.001 <0.001 <0.001 

82661 Trifluralin 40 0.005 <0.002 0.001 <0.009 <0.002 <0.002 <0.002 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Cahaba River at Centreville, Alabama—January 2000 to September 2001 

parameter code 

Compound (HPLC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

39732 2,4-D 18 0.444 <0.022 0.074* 0.444 0.067 <0.077 <0.077 <0.077 

50470 2,4-D methyl ester 18 0.016 <0.009 0.016 <0.086 <0.086 <0.086 <0.086 

38746 2,4-DB (E) 18 <0.054 <0.016 <0.054 <0.054 <0.054 <0.054 <0.054 

50355 2-hydroxyatrazine (E) 18 0.057 <0.193 0.016* 0.057 0.012 <0.193 <0.193 <0.193 

61692 3,4-chlorophenyl-1- 18 <0.091 <0.024 <0.091 <0.091 <0.091 <0.091 <0.091 

methyl urea 

Appendixes 89 
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Appendix 3. Summary statistics for pesticides in surface-water samples collected from the Mobile River Basin , 1999– 2001—Continued 

[NWIS, National Water Information System; GC/MS, gas chromatography/mass spectrometry; <, less than; --, no value; *, value is estimated by using a logprobability regression to predict values of data below the detection limit; E, estimated concentration; HPLC/MS, high-performance liquid chromatography/mass 

spectrometry] 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Cahaba River at Centreville, Alabama—January 2000 to September 2001 (Continued) 

parameter code 

Compound (HPLC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

49308 3-hydroxycarbofuran 18 <0.062 <0.006 <0.062 <0.062 <0.062 <0.062 <0.062 

50295 3-ketocarbofuran (E) 18 <1.500 <0.072 <1.500 <0.072 <0.072 <0.072 <0.072 

49315 Acifluorfen 18 <0.062 <0.007 <0.062 <0.062 <0.062 <0.062 <0.062 

49312 Aldicarb (E) 18 <0.082 <0.040 <0.082 <0.082 <0.082 <0.082 <0.082 

49313 Aldicarb sulfone (E) 18 <0.160 <0.020 <0.160 <0.160 <0.160 <0.160 <0.160 

49314 Aldicarb sulfoxide (E) 17 <0.027 <0.008 <0.027 <0.027 <0.027 <0.027 <0.027 

50299 Bendiocarb 18 <0.061 <0.025 <0.061 <0.061 <0.061 <0.061 <0.061 

50300 Benomyl 18 0.009 <0.004 0.009 <0.022 <0.022 <0.022 <0.022 

61693 Bensulfuron-methyl 18 <0.048 <0.016 <0.048 <0.048 <0.048 <0.048 <0.048 

38711 Bentazon (E) 18 0.003 <0.011 0.003 <0.019 <0.019 <0.019 <0.019 

04029 Bromacil (E) 18 0.011 <0.081 0.011 <0.081 <0.081 <0.081 <0.081 

49311 Bromoxynil (E) 18 <0.057 <0.017 <0.057 <0.057 <0.057 <0.057 <0.057 

50305 Caffeine 17 0.109 <0.080 0.041* 0.109 0.045 0.017 <0.080 <0.080 

49310 Carbaryl 18 0.004 <0.028 0.004 <0.063 <0.063 <0.063 <0.063 

49309 Carbofuran 18 <0.057 <0.006 <0.057 <0.057 <0.057 <0.057 <0.057 

61188 Chloramben, methyl 18 <0.114 <0.018 <0.114 <0.114 <0.114 <0.114 <0.114 

ester (E) 

50306 Chlorimuron, ethyl 18 <0.037 <0.010 <0.037 <0.037 <0.037 <0.037 <0.037 

49306 Chlorothalonil (E) 18 0.627 <0.035 0.627 <0.049 <0.049 <0.049 <0.049 

49305 Clopyralid 18 0.019 <0.014 0.019 <0.041 <0.041 <0.041 <0.041 

04031 Cycloate (E) 18 <0.054 <0.013 <0.054 <0.054 <0.054 <0.054 <0.054 

49304 Dacthal mono-acid 18 <0.072 <0.012 <0.072 <0.072 <0.072 <0.072 <0.072 

04039 Deethyldeisopropyl- 18 0.038 <0.010 0.020* 0.038 0.021 <0.150 <0.060 <0.060 

atrazine (E) 

04038 Deisopropylatrazine (E) 18 0.058 <0.044 0.021* 0.058 0.025 0.01 <0.074 <0.074 

38442 Dicamba 18 0.029 <0.013 0.029 <0.096 <0.096 <0.096 <0.096 

49302 Dichlorprop 18 0.016 <0.014 0.016 <0.050 <0.050 <0.050 <0.050 

49301 Dinoseb 18 <0.043 <0.012 <0.043 <0.043 <0.043 <0.043 <0.043 

04033 Diphenamid 18 <0.058 <0.026 <0.058 <0.058 <0.058 <0.058 <0.058 

49300 Diuron 18 0.361 <0.079 0.057* 0.361 0.071 0.014 <0.079 <0.079 

49297 Fenuron 18 <0.073 <0.032 <0.073 <0.073 <0.073 <0.073 <0.073 

61694 Flumetsulam (E) 18 <0.087 <0.011 <0.087 <0.087 <0.087 <0.087 <0.087 

38811 Fluometuron 18 <0.062 <0.031 <0.062 <0.062 <0.062 <0.062 <0.062 

50356 Imazaquin (E) 16 0.153 <0.016 0.153 <0.103 <0.103 <0.103 <0.103 

50407 Imazethapyr (E) 14 0.041 <0.017 0.041 <0.088 <0.088 <0.088 <0.088 

61695 Imidacloprid 18 0.014 <0.007 0.014 <0.106 <0.106 <0.106 <0.106 

38478 Linuron 18 <0.069 <0.014 <0.069 <0.069 <0.069 <0.069 <0.069 

38482 MCPA 18 0.092 <0.016 0.032* 0.092 0.032 <0.058 <0.058 <0.058 

38487 MCPB (E) 18 <0.062 <0.015 <0.062 <0.062 <0.062 <0.062 <0.062 

50359 Metalaxyl 17 0.004 <0.057 0.004 <0.057 <0.057 <0.057 <0.057 

38501 Methiocarb (E) 18 <0.079 <0.008 <0.079 <0.079 <0.079 <0.079 <0.079 

49296 Methomyl (E) 18 <0.077 <0.004 <0.077 <0.077 <0.077 <0.077 <0.077 

61696 Methomyl oxime (E) 18 <0.200 <0.010 <0.200 <0.010 <0.010 <0.010 <0.010 

61697 Metsulfuron-methyl (E) 18 <0.114 <0.025 <0.114 <0.114 <0.114 <0.114 <0.114 

90 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999–2001 
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Appendix 3. Summary statistics for pesticides in surface-water samples collected from the Mobile River Basin , 1999– 2001—Continued 

[NWIS, National Water Information System; GC/MS, gas chromatography/mass spectrometry; <, less than; --, no value; *, value is estimated by using a logprobability regression to predict values of data below the detection limit; E, estimated concentration; HPLC/MS, high-performance liquid chromatography/mass 

spectrometry] 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Cahaba River at Centreville, Alabama—January 2000 to September 2001 (Continued) 

parameter code 

Compound (HPLC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

49294 Neburon 18 <0.075 <0.012 <0.075 <0.075 <0.075 <0.075 <0.075 

50364 Nicosulfuron 18 <0.065 <0.013 <0.065 <0.065 <0.065 <0.065 <0.065 

49293 Norflurazon (E) 18 <0.077 <0.016 <0.077 <0.077 <0.077 <0.077 <0.077 

49292 Oryzalin 18 0.067 <0.018 0.067 <0.071 <0.071 <0.071 <0.071 

38866 Oxamyl 18 <0.016 <0.012 <0.016 <0.016 <0.016 <0.016 <0.016 

50410 Oxamyl oxime (E) 18 <0.064 <0.013 <0.064 <0.064 <0.064 <0.064 <0.064 

49291 Picloram 18 <0.071 <0.020 <0.071 <0.071 <0.071 <0.071 <0.071 

49236 Propham 18 <0.072 <0.010 <0.072 <0.072 <0.072 <0.072 <0.072 

50471 Propiconazole 18 <0.064 <0.021 <0.064 <0.064 <0.064 <0.064 <0.064 

38538 Propoxur 18 <0.059 <0.008 <0.059 <0.059 <0.059 <0.059 <0.059 

38548 Siduron 18 0.004 <0.017 0.004 <0.093 <0.093 <0.093 <0.093 

50337 Sulfometruron-methyl 18 0.02 <0.009 0.02 <0.039 <0.039 <0.039 <0.039 

04032 Terbacil (E) 18 <0.095 <0.010 <0.095 <0.095 <0.095 <0.095 <0.095 

61159 Tribenuron-methyl (E) 18 <0.068 <0.009 <0.068 <0.068 <0.068 <0.068 <0.068 

49235 Triclopyr 18 0.12 <0.022 0.062* 0.12 0.053 <0.101 <0.101 <0.101 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Cahaba Valley Creek at Cross Creek Road at Pelham, Alabama—January 1999 to December 2001 

parameter code Compound (GC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

82660 2,6-diethylaniline 63 <0.003 <0.002 <0.003 <0.003 <0.003 <0.003 <0.002 

49260 Acetochlor 63 <0.004 <0.002 <0.004 <0.002 <0.002 <0.002 <0.002 

46342 Alachlor 63 0.018 <0.002 0.004 <0.002 <0.002 <0.002 <0.002 

34253 Alpha-HCH 63 <0.005 <0.002 <0.005 <0.002 <0.002 <0.002 <0.002 

39632 Atrazine 65 0.682 0.007 0.047 0.165 0.035 0.026 0.017 0.009 

82673 Benfluralin 63 0.004 <0.002 <0.010 <0.010 <0.002 <0.002 <0.002 

04028 Butylate 63 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 

82680 Carbaryl (E) 63 0.369 <0.003 0.017* 0.08 0.005 <0.003 <0.003 <0.003 

82674 Carbofuran (E) 63 <0.020 <0.003 <0.020 <0.003 <0.003 <0.003 <0.003 

38933 Chlorpyrifos 63 0.03 <0.004 0.004* 0.006 0.003 <0.004 <0.004 <0.004 

04041 Cyanazine 63 <0.018 <0.004 <0.018 <0.004 <0.004 <0.004 <0.004 

82682 Dacthal (DCPA) 63 <0.003 <0.002 <0.003 <0.002 <0.002 <0.002 <0.002 

04040 Deethylatrazine (E) 64 0.093 0.005 0.014 0.046 0.012 0.011 0.009 0.006 

34653 p,p'-DDE 63 <0.006 <0.002 <0.006 <0.006 <0.006 <0.006 <0.002 

39572 Diazinon 63 0.087 <0.002 0.015* 0.046 0.015 0.008 0.005 <0.002 

39381 Dieldrin 63 <0.005 <0.001 <0.005 <0.001 <0.001 <0.001 <0.001 

82677 Disulfoton 63 <0.021 <0.017 <0.021 <0.017 <0.017 <0.017 <0.017 

82668 EPTC 63 <0.005 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 

82663 Ethalfluralin 63 <0.009 <0.004 <0.009 <0.004 <0.004 <0.004 <0.004 

82672 Ethoprop 63 0.003 <0.003 <0.005 <0.003 <0.003 <0.003 <0.003 

04095 Fonofox 63 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 

39341 Lindane 63 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 

82666 Linuron 63 <0.035 <0.002 <0.035 <0.002 <0.002 <0.002 <0.002 

39532 Malathion 63 0.027 <0.005 0.004* 0.004 <0.027 <0.005 <0.005 <0.005 

82686 Methyl azinphos (E) 63 <0.050 <0.001 <0.050 <0.001 <0.001 <0.001 <0.001 

Appendixes 91 
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Appendix 3. Summary statistics for pesticides in surface-water samples collected from the Mobile River Basin , 1999– 2001—Continued 

[NWIS, National Water Information System; GC/MS, gas chromatography/mass spectrometry; <, less than; --, no value; *, value is estimated by using a logprobability regression to predict values of data below the detection limit; E, estimated concentration; HPLC/MS, high-performance liquid chromatography/mass 

spectrometry] 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Cahaba Valley Creek at Cross Creek Road at Pelham, Alabama—January 1999 to December 2001 (Continued) 

parameter code 

Compound (GC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

82667 Methyl parathion 63 <0.006 <0.006 <0.006 <0.006 <0.006 <0.006 <0.006 

39415 Metolachlor 63 0.012 <0.002 0.002* 0.005 <0.013 <0.002 <0.002 <0.002 

82630 Metribuzin 63 <0.006 <0.004 <0.006 <0.004 <0.004 <0.004 <0.004 

82671 Molinate 63 0.006 <0.002 <0.004 <0.004 <0.004 <0.004 <0.002 

82684 Napropamide 63 <0.007 <0.003 <0.007 <0.003 <0.003 <0.003 <0.003 

39542 Parathion 63 <0.007 <0.004 <0.007 <0.004 <0.004 <0.004 <0.004 

82669 Pebulate 63 <0.004 <0.002 <0.004 <0.004 <0.004 <0.004 <0.002 

82683 Pendimethalin 63 0.045 <0.004 0.007* 0.029 <0.010 <0.004 <0.004 <0.004 

82687 cis-Permethrin 63 <0.006 <0.005 <0.006 <0.005 <0.005 <0.005 <0.005 

82664 Phorate 63 <0.011 <0.002 <0.011 <0.002 <0.002 <0.002 <0.002 

04037 Prometon 63 0.014 <0.015 0.006* 0.01 0.006 0.003 <0.018 <0.015 

82676 Pronamide 63 0.066 <0.003 <0.015 <0.004 <0.003 <0.003 <0.003 

04024 Propachlor 63 <0.010 <0.007 <0.010 <0.007 <0.007 <0.007 <0.007 

82679 Propanil 63 0.008 <0.004 <0.011 <0.004 <0.004 <0.004 <0.004 

82685 Propargite 55 <0.130 <0.013 <0.040 <0.023 <0.013 <0.013 <0.013 

04035 Simazine 63 1.99 0.018 0.232 1.498 0.188 0.062 0.029 0.02 

82670 Tebuthiuron 64 0.032 <0.006 0.006* 0.014 <0.077 <0.010 <0.010 <0.010 

82665 Terbacil (E) 63 <0.034 <0.007 <0.034 <0.007 <0.007 <0.007 <0.007 

82675 Terbufos 63 <0.017 <0.013 <0.017 <0.013 <0.013 <0.013 <0.013 

82681 Thiobencarb 63 <0.005 <0.002 <0.005 <0.002 <0.002 <0.002 <0.002 

82678 Triallate 63 <0.002 <0.001 <0.002 <0.001 <0.001 <0.001 <0.001 

82661 Trifluralin 63 0.007 <0.002 0.002* 0.005 <0.009 <0.002 <0.002 <0.002 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Cahaba Valley Creek at Cross Creek Road at Pelham, Alabama—January 2000 to December 2001 

parameter code Compound (HPLC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

39732 2,4-D 25 0.628 <0.022 0.105* 0.488 0.05 <0.077 <0.077 <0.022 

50470 2,4-D methyl ester 25 0.081 <0.009 0.023 <0.086 <0.086 <0.086 <0.009 

38746 2,4-DB (E) 25 <0.054 <0.016 <0.054 <0.054 <0.054 <0.054 <0.016 

50355 2-hydroxyatrazine (E) 25 0.083 <0.193 0.021* 0.055 0.022 0.009 <0.193 <0.193 

61692 3,4-chlorophenyl-1- 25 <0.091 <0.024 <0.091 <0.091 <0.091 <0.091 <0.024 

methyl urea 

49308 3-hydroxycarbofuran 25 <0.062 <0.006 <0.062 <0.062 <0.062 <0.062 <0.006 

50295 3-ketocarbofuran (E) 25 <1.500 <0.072 <1.500 <0.072 <0.072 <0.072 <0.072 

49315 Acifluorfen 25 <0.062 <0.007 <0.062 <0.062 <0.062 <0.062 <0.007 

49312 Aldicarb (E) 25 <0.100 <0.040 <0.082 <0.082 <0.082 <0.082 <0.040 

49313 Aldicarb sulfone (E) 25 <0.160 <0.020 <0.160 <0.160 <0.160 <0.160 <0.020 

49314 Aldicarb sulfoxide (E) 24 <0.027 <0.008 <0.027 <0.027 <0.027 <0.027 <0.008 

50299 Bendiocarb 25 <0.061 <0.025 <0.061 <0.061 <0.061 <0.061 <0.025 

50300 Benomyl 25 0.039 <0.004 0.018 <0.022 <0.022 <0.022 <0.004 

61693 Bensulfuron-methyl 25 <0.048 <0.016 <0.048 <0.048 <0.048 <0.048 <0.016 

38711 Bentazon (E) 24 <0.019 <0.011 <0.019 <0.019 <0.019 <0.019 <0.011 

04029 Bromacil (E) 25 0.031 <0.033 <0.081 <0.081 <0.081 <0.081 <0.033 

49311 Bromoxynil (E) 25 <0.057 <0.017 <0.057 <0.057 <0.057 <0.057 <0.017 

92 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999–2001 
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Appendix 3. Summary statistics for pesticides in surface-water samples collected from the Mobile River Basin , 1999– 2001—Continued 

[NWIS, National Water Information System; GC/MS, gas chromatography/mass spectrometry; <, less than; --, no value; *, value is estimated by using a logprobability regression to predict values of data below the detection limit; E, estimated concentration; HPLC/MS, high-performance liquid chromatography/mass 

spectrometry] 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Cahaba Valley Creek at Cross Creek Road at Pelham, Alabama—January 2000 to December 2001 (Continued) 

parameter code 

Compound (HPLC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

50305 Caffeine 25 0.392 <0.010 0.085* 0.289 0.141 0.038 0.011 <0.010 

49310 Carbaryl 25 0.065 <0.003 0.008* 0.01 <0.063 <0.063 <0.063 <0.028 

49309 Carbofuran 25 <0.057 <0.006 <0.057 <0.057 <0.057 <0.057 <0.006 

61188 Chloramben, methyl 25 <0.114 <0.018 <0.114 <0.114 <0.114 <0.114 <0.018 

ester (E) 

50306 Chlorimuron, ethyl 25 <0.037 <0.010 <0.037 <0.037 <0.037 <0.037 <0.010 

49306 Chlorothalonil (E) 25 <0.049 <0.035 <0.049 <0.049 <0.049 <0.049 <0.035 

49305 Clopyralid 25 0.04 <0.014 0.034 <0.041 <0.041 <0.041 <0.014 

04031 Cycloate (E) 25 <0.054 <0.013 <0.054 <0.054 <0.054 <0.054 <0.013 

49304 Dacthal mono-acid 25 <0.072 <0.012 <0.072 <0.072 <0.072 <0.072 <0.012 

04039 Deethyldeisopropyl- 25 0.078 <0.010 0.025* 0.061 0.021 <0.060 <0.060 <0.010 

atrazine (E) 

04038 Deisopropylatrazine (E) 25 1.027 <0.044 0.090* 0.48 0.041 0.011 <0.074 <0.044 

38442 Dicamba 25 0.212 <0.013 0.091 <0.096 <0.096 <0.096 <0.013 

49302 Dichlorprop 25 0.056 <0.014 0.03 <0.050 <0.050 <0.050 <0.014 

49301 Dinoseb 25 <0.043 <0.012 <0.043 <0.043 <0.043 <0.043 <0.012 

04033 Diphenamid 25 0.007 <0.002 <0.058 <0.058 <0.058 <0.058 <0.026 

49300 Diuron 25 0.065 <0.015 0.027* 0.06 0.02 <0.079 <0.079 <0.015 

49297 Fenuron 25 <0.073 <0.032 <0.073 <0.073 <0.073 <0.073 <0.032 

61694 Flumetsulam (E) 25 <0.087 <0.011 <0.087 <0.087 <0.087 <0.087 <0.011 

38811 Fluometuron 25 0.005 <0.031 0.005 <0.062 <0.062 <0.062 <0.031 

50356 Imazaquin (E) 23 0.215 <0.009 0.038* 0.157 <0.103 <0.103 <0.103 <0.016 

50407 Imazethapyr (E) 21 <0.088 <0.017 <0.088 <0.088 <0.088 <0.088 <0.017 

61695 Imidacloprid 25 0.04 <0.007 0.024* 0.036 <0.106 <0.106 <0.106 <0.007 

38478 Linuron 25 <0.069 <0.014 <0.069 <0.069 <0.069 <0.069 <0.014 

38482 MCPA 25 0.594 <0.016 0.063* 0.258 0.034 <0.058 <0.058 <0.016 

38487 MCPB (E) 25 <0.062 <0.015 <0.062 <0.062 <0.062 <0.062 <0.015 

50359 Metalaxyl 25 0.018 <0.002 0.007* 0.012 0.003 <0.057 <0.057 <0.020 

38501 Methiocarb (E) 25 <0.079 <0.008 <0.079 <0.079 <0.079 <0.079 <0.008 

49296 Methomyl (E) 25 <0.077 <0.004 <0.077 <0.077 <0.077 <0.077 <0.004 

61696 Methomyl oxime (E) 25 <0.200 <0.010 <0.011 <0.010 <0.010 <0.010 <0.010 

61697 Metsulfuron-methyl (E) 25 <0.200 <0.025 <0.114 <0.114 <0.114 <0.114 <0.025 

49294 Neburon 25 0.003 <0.012 <0.075 <0.075 <0.075 <0.075 <0.012 

50364 Nicosulfuron 25 <0.065 <0.013 <0.065 <0.065 <0.065 <0.065 <0.013 

49293 Norflurazon (E) 25 <0.077 <0.016 <0.077 <0.077 <0.077 <0.077 <0.016 

49292 Oryzalin 25 0.127 <0.018 0.111 <0.071 <0.071 <0.071 <0.018 

38866 Oxamyl 25 <0.016 <0.012 <0.016 <0.016 <0.016 <0.016 <0.012 

50410 Oxamyl oxime (E) 24 <0.064 <0.013 <0.064 <0.064 <0.064 <0.064 <0.013 

49291 Picloram 25 <0.071 <0.020 <0.071 <0.071 <0.071 <0.071 <0.020 

49236 Propham 25 <0.072 <0.010 <0.072 <0.072 <0.072 <0.072 <0.010 

50471 Propiconazole 25 <0.064 <0.004 <0.064 <0.064 <0.064 <0.064 <0.009 

38538 Propoxur 25 0.005 <0.003 0.004 <0.059 <0.059 <0.059 <0.008 

38548 Siduron 25 0.007 <0.017 0.003 <0.093 <0.093 <0.093 <0.017 

50337 Sulfometruron-methyl 25 0.067 <0.009 0.02 <0.039 <0.039 <0.039 <0.009 

Appendixes 93 
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Appendix 3. Summary statistics for pesticides in surface-water samples collected from the Mobile River Basin , 1999– 2001—Continued 

[NWIS, National Water Information System; GC/MS, gas chromatography/mass spectrometry; <, less than; --, no value; *, value is estimated by using a logprobability regression to predict values of data below the detection limit; E, estimated concentration; HPLC/MS, high-performance liquid chromatography/mass 

spectrometry] 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Cahaba Valley Creek at Cross Creek Road at Pelham, Alabama—January 2000 to December 2001 (Continued) 

parameter code 

Compound (HPLC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

04032 Terbacil (E) 25 <0.100 <0.010 <0.095 <0.095 <0.095 <0.095 <0.010 

61159 Tribenuron-methyl (E) 24 <0.068 <0.009 <0.068 <0.068 <0.068 <0.068 <0.009 

49235 Triclopyr 25 0.116 <0.022 0.038 <0.101 <0.101 <0.101 <0.022 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Chattooga River above Gaylesville, Alabama—January 1999 to December 2000 

parameter code 

Compound (GC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

82660 2,6-diethylaniline 2 <0.003 <0.003 

49260 Acetochlor 2 <0.002 <0.002 

46342 Alachlor 2 <0.002 <0.002 

34253 Alpha-HCH 2 <0.002 <0.002 

39632 Atrazine 2 0.011 0.01 

82673 Benfluralin 2 <0.002 <0.002 

04028 Butylate 2 <0.002 <0.002 

82680 Carbaryl (E) 2 0.005 <0.003 

82674 Carbofuran (E) 2 <0.003 <0.003 

38933 Chlorpyrifos 2 <0.004 <0.004 

04041 Cyanazine 2 <0.004 <0.004 

82682 Dacthal (DCPA) 2 <0.002 <0.002 

04040 Deethylatrazine (E) 2 0.005 0.004 

34653 p,p'-DDE 2 <0.006 <0.006 

39572 Diazinon 2 0.006 <0.002 

39381 Dieldrin 2 <0.001 <0.001 

82677 Disulfoton 2 <0.017 <0.017 

82668 EPTC 2 <0.002 <0.002 

82663 Ethalfluralin 2 <0.004 <0.004 

82672 Ethoprop 2 <0.003 <0.003 

04095 Fonofox 2 <0.003 <0.003 

39341 Lindane 2 <0.004 <0.004 

82666 Linuron 2 <0.002 <0.002 

39532 Malathion 2 <0.005 <0.005 

82686 Methyl azinphos (E) 2 <0.001 <0.001 

82667 Methyl parathion 2 <0.006 <0.006 

39415 Metolachlor 2 0.004 <0.007 

82630 Metribuzin 2 <0.004 <0.004 

82671 Molinate 2 <0.004 <0.004 

82684 Napropamide 2 <0.003 <0.003 

39542 Parathion 2 <0.004 <0.004 

82669 Pebulate 2 <0.004 <0.004 

82683 Pendimethalin 2 <0.004 <0.004 

82687 cis-Permethrin 2 <0.005 <0.005 

82664 Phorate 2 <0.002 <0.002 

04037 Prometon 2 0.007 0.006 

82676 Pronamide 2 <0.003 <0.003 

94 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999–2001 
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Appendix 3. Summary statistics for pesticides in surface-water samples collected from the Mobile River Basin , 1999– 2001—Continued 

[NWIS, National Water Information System; GC/MS, gas chromatography/mass spectrometry; <, less than; --, no value; *, value is estimated by using a logprobability regression to predict values of data below the detection limit; E, estimated concentration; HPLC/MS, high-performance liquid chromatography/mass 

spectrometry] 

December

NWIS 

of 

Minimum 95% 75% 50% 5% 

Chattooga River above Gaylesville, Alabama—January 1999 to 2000 (Continued) 

parameter code 

Compound (GC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

04024 Propachlor 2 <0.007 <0.007 

82679 Propanil 2 <0.004 <0.004 

82685 Propargite 2 <0.030 <0.013 

04035 Simazine 2 0.02 <0.005 

82670 Tebuthiuron 2 0.011 <0.010 

82665 Terbacil (E) 2 <0.007 <0.007 

82675 Terbufos 2 <0.013 <0.013 

82681 Thiobencarb 2 <0.002 <0.002 

82678 Triallate 2 <0.001 <0.001 

82661 Trifluralin 2 <0.002 <0.002 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Pintlalla Creek at Liberty Church Road near Pintlalla, Alabama—January 1999 to December 2000 

parameter code 

Compound (GC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

82660 2,6-diethylaniline 3 <0.003 <0.003 

49260 Acetochlor 3 <0.002 <0.002 

46342 Alachlor 3 <0.002 <0.002 

34253 Alpha-HCH 3 <0.002 <0.002 

39632 Atrazine 3 0.006 <0.001 

82673 Benfluralin 3 <0.002 <0.002 

04028 Butylate 3 <0.002 <0.002 

82680 Carbaryl (E) 3 0.004 <0.003 

82674 Carbofuran (E) 3 <0.003 <0.003 

38933 Chlorpyrifos 3 <0.004 <0.004 

04041 Cyanazine 3 <0.004 <0.004 

82682 Dacthal (DCPA) 3 <0.002 <0.002 

04040 Deethylatrazine (E) 3 <0.002 <0.002 

34653 p,p'-DDE 3 <0.006 <0.006 

39572 Diazinon 3 <0.002 <0.002 

39381 Dieldrin 3 <0.001 <0.001 

82677 Disulfoton 3 <0.017 <0.017 

82668 EPTC 3 <0.002 <0.002 

82663 Ethalfluralin 3 <0.004 <0.004 

82672 Ethoprop 3 <0.003 <0.003 

04095 Fonofox 3 <0.003 <0.003 

39341 Lindane 3 <0.004 <0.004 

82666 Linuron 3 <0.002 <0.002 

39532 Malathion 3 <0.005 <0.005 

82686 Methyl azinphos (E) 3 <0.001 <0.001 

82667 Methyl parathion 3 <0.006 <0.006 

39415 Metolachlor 3 <0.002 <0.002 

82630 Metribuzin 3 <0.004 <0.004 

82671 Molinate 3 <0.004 <0.004 

82684 Napropamide 3 <0.003 <0.003 

Appendixes 95 
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Appendix 3. Summary statistics for pesticides in surface-water samples collected from the Mobile River Basin , 1999 – 2001—Continued 

[NWIS, National Water Information System; GC/MS, gas chromatography/mass spectrometry; <, less than; --, no value; *, value is estimated by using a logprobability regression to predict values of data below the detection limit; E, estimated concentration; HPLC/MS, high-performance liquid chromatography/mass 

spectrometry] 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Pintlalla Creek at Liberty Church Road near Pintlalla, Alabama—January 1999 to December 2000 (Continued) 

parameter code 

Compound (GC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

39542 Parathion 3 <0.004 <0.004 

82669 Pebulate 3 <0.004 <0.004 

82683 Pendimethalin 3 <0.004 <0.004 

82687 cis-Permethrin 3 <0.005 <0.005 

82664 Phorate 3 <0.002 <0.002 

04037 Prometon 3 <0.018 <0.018 

82676 Pronamide 3 <0.003 <0.003 

4024 Propachlor 3 <0.007 <0.007 

82679 Propanil 3 <0.004 <0.004 

82685 Propargite 3 <0.013 <0.013 

04035 Simazine 3 <0.005 <0.005 

82670 Tebuthiuron 3 <0.010 <0.010 

82665 Terbacil (E) 3 <0.007 <0.007 

82675 Terbufos 3 <0.013 <0.013 

82681 Thiobencarb 3 <0.002 <0.002 

82678 Triallate 3 <0.001 <0.001 

82661 Trifluralin 3 <0.002 <0.002 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Threemile Branch at North Boulevard at Montgomery, Alabama—January 1999 to September 2001 

parameter code 

Compound (GC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

82660 2,6-diethylaniline 28 <0.003 <0.002 <0.003 <0.003 <0.003 <0.002 <0.002 

49260 Acetochlor 28 <0.004 <0.002 <0.004 <0.004 <0.002 <0.002 <0.002 

46342 Alachlor 28 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 

34253 Alpha-HCH 28 0.02 <0.002 0.001 <0.005 <0.002 <0.002 <0.002 

39632 Atrazine 28 4.83 0.004 0.346 3.286 0.122 0.035 0.006 0.004 

82673 Benfluralin 28 0.003 <0.002 0.001 <0.010 <0.010 <0.002 <0.002 

04028 Butylate 28 <0.150 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 

82680 Carbaryl (E) 28 0.422 <0.003 0.039* 0.275 0.024 <0.041 <0.041 <0.003 

82674 Carbofuran (E) 28 0.017 <0.003 0.003 <0.020 <0.010 <0.003 <0.003 

38933 Chlorpyrifos 28 0.127 0.004 0.018 0.1 0.019 0.007 0.005 0.004 

04041 Cyanazine 28 <0.018 <0.004 <0.018 <0.018 <0.004 <0.004 <0.004 

82682 Dacthal (DCPA) 28 <0.003 <0.002 <0.003 <0.003 <0.002 <0.002 <0.002 

04040 Deethylatrazine (E) 28 0.214 <0.006 0.020* 0.084 0.008 0.006 0.004 <0.006 

34653 p,p'-DDE 28 <0.006 <0.002 <0.006 <0.006 <0.006 <0.002 <0.002 

39572 Diazinon 28 1.01 <0.002 0.098* 0.364 0.064 0.022 0.008 <0.005 

39381 Dieldrin 28 0.024 <0.001 0.012* 0.022 0.015 0.012 <0.020 <0.001 

82677 Disulfoton 28 <0.021 <0.017 <0.021 <0.021 <0.017 <0.017 <0.017 

82668 EPTC 28 <0.025 <0.002 <0.010 <0.002 <0.002 <0.002 <0.002 

82663 Ethalfluralin 28 <0.009 <0.004 <0.009 <0.009 <0.004 <0.004 <0.004 

82672 Ethoprop 28 <0.005 <0.003 <0.005 <0.005 <0.003 <0.003 <0.003 

04095 Fonofox 28 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 

39341 Lindane 28 0.009 <0.004 0.003* 0.005 <0.004 <0.004 <0.004 <0.004 

82666 Linuron 28 <0.035 <0.002 <0.035 <0.035 <0.002 <0.002 <0.002 

96 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999–2001 
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Appendix 3. Summary statistics for pesticides in surface-water samples collected from the Mobile River Basin , 1999 – 2001—Continued 

[NWIS, National Water Information System; GC/MS, gas chromatography/mass spectrometry; <, less than; --, no value; *, value is estimated by using a logprobability regression to predict values of data below the detection limit; E, estimated concentration; HPLC/MS, high-performance liquid chromatography/mass 

spectrometry] 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Threemile Branch at North Boulevard at Montgomery, Alabama—January 1999 to September 2001 (Continued) 

parameter code 

Compound (GC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

39532 Malathion 28 9.58 <0.005 0.430* 0.665 0.076 0.014 <0.027 <0.005 

82686 Methyl azinphos (E) 28 <0.050 <0.001 <0.050 <0.050 <0.001 <0.001 <0.001 

82667 Methyl parathion 28 <0.006 <0.006 <0.006 <0.006 <0.006 <0.006 <0.006 

39415 Metolachlor 28 0.014 <0.013 0.005* 0.012 0.006 0.004 0.002 <0.013 

82630 Metribuzin 28 <0.006 <0.004 <0.006 <0.006 <0.004 <0.004 <0.004 

82671 Molinate 28 0.01 <0.002 <0.020 <0.004 <0.004 <0.002 <0.002 

82684 Napropamide 28 <0.007 <0.003 <0.007 <0.007 <0.003 <0.003 <0.003 

39542 Parathion 28 <0.007 <0.004 <0.007 <0.007 <0.004 <0.004 <0.004 

82669 Pebulate 28 <0.020 <0.002 <0.004 <0.004 <0.004 <0.002 <0.002 

82683 Pendimethalin 28 0.365 <0.004 0.030* 0.284 0.013 <0.010 <0.004 <0.004 

82687 cis-Permethrin 28 <0.006 <0.005 <0.006 <0.006 <0.005 <0.005 <0.005 

82664 Phorate 28 <0.011 <0.002 <0.011 <0.011 <0.002 <0.002 <0.002 

04037 Prometon 28 0.044 <0.015 0.012* 0.029 0.018 0.005 <0.018 <0.015 

82676 Pronamide 28 <0.008 <0.003 <0.004 <0.004 <0.003 <0.003 <0.003 

04024 Propachlor 28 <0.010 <0.007 <0.010 <0.010 <0.007 <0.007 <0.007 

82679 Propanil 28 <0.011 <0.004 <0.011 <0.011 <0.004 <0.004 <0.004 

82685 Propargite 27 <0.040 <0.013 <0.023 <0.023 <0.023 <0.013 <0.013 

04035 Simazine 28 7.13 <0.005 0.405* 1.06 0.129 0.013 0.007 <0.011 

82670 Tebuthiuron 28 0.489 <0.010 0.065* 0.091 0.06 0.051 0.032 <0.010 

82665 Terbacil (E) 28 0.036 <0.007 <0.034 <0.034 <0.007 <0.007 <0.007 

82675 Terbufos 28 <0.017 <0.013 <0.017 <0.017 <0.013 <0.013 <0.013 

82681 Thiobencarb 28 <0.005 <0.002 <0.005 <0.005 <0.002 <0.002 <0.002 

82678 Triallate 28 0.002 <0.001 <0.002 <0.002 <0.001 <0.001 <0.001 

82661 Trifluralin 28 0.004 <0.002 0.002* 0.003 <0.009 <0.009 <0.002 <0.002 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Threemile Branch at North Boulevard at Montgomery, Alabama—January 2000 to September 2001 

parameter code Compound (HPLC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

39732 2,4-D 14 74.6 <0.077 5.759* 74.572 0.568 0.308 <0.077 <0.077 

50470 2,4-D methyl ester 14 0.266 <0.009 0.093* 0.266 0.067 <0.086 <0.086 <0.086 

38746 2,4-DB (E) 14 0.02 <0.054 0.02 <0.054 <0.054 <0.054 <0.054 

50355 2-hydroxyatrazine (E) 14 0.418 <0.008 0.080* 0.418 0.048 <0.193 <0.193 <0.193 

61692 3,4-chlorophenyl-1- 14 <0.091 <0.024 <0.091 <0.091 <0.091 <0.091 <0.091 

methyl urea 

49308 3-hydroxycarbofuran 14 <0.062 <0.006 <0.062 <0.062 <0.062 <0.062 <0.062 

50295 3-ketocarbofuran (E) 14 <1.500 <0.072 <1.500 <0.072 <0.072 <0.072 <0.072 

49315 Acifluorfen 14 0.008 <0.007 0.008 <0.062 <0.062 <0.062 <0.062 

49312 Aldicarb (E) 14 <0.082 <0.040 <0.082 <0.082 <0.082 <0.082 <0.082 

49313 Aldicarb sulfone (E) 14 <0.160 <0.020 <0.160 <0.160 <0.160 <0.160 <0.160 

49314 Aldicarb sulfoxide (E) 14 <0.027 <0.008 <0.027 <0.027 <0.027 <0.027 <0.027 

50299 Bendiocarb 14 0.006 <0.025 0.006 <0.061 <0.061 <0.061 <0.061 

50300 Benomyl 14 <0.022 <0.004 <0.022 <0.022 <0.022 <0.022 <0.022 

61693 Bensulfuron-methyl 14 <0.048 <0.016 <0.048 <0.048 <0.048 <0.048 <0.048 

38711 Bentazon (E) 14 0.005 <0.011 0.005 <0.019 <0.019 <0.019 <0.019 

Appendixes 97 
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Appendix 3. Summary statistics for pesticides in surface-water samples collected from the Mobile River Basin , 1999 – 2001—Continued 

[NWIS, National Water Information System; GC/MS, gas chromatography/mass spectrometry; <, less than; --, no value; *, value is estimated by using a logprobability regression to predict values of data below the detection limit; E, estimated concentration; HPLC/MS, high-performance liquid chromatography/mass 

spectrometry] 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Threemile Branch at North Boulevard at Montgomery, Alabama—January 2000 to September 2001 (Continued) 

parameter code 

Compound (HPLC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

04029 Bromacil (E) 14 0.15 <0.081 0.098* 0.15 0.119 0.093 0.053 <0.081 

49311 Bromoxynil (E) 14 <0.057 <0.017 <0.057 <0.057 <0.057 <0.057 <0.057 

50305 Caffeine 14 5.25 <0.080 0.660* 5.247 0.562 0.064 <0.080 <0.080 

49310 Carbaryl 14 0.093 <0.028 0.019* 0.093 0.009 <0.063 <0.063 <0.063 

49309 Carbofuran 14 <0.057 <0.006 <0.057 <0.057 <0.057 <0.057 <0.057 

61188 Chloramben, methyl 14 <0.114 <0.018 <0.114 <0.114 <0.114 <0.114 <0.114 

ester (E) 

50306 Chlorimuron, ethyl 14 <0.037 <0.010 <0.037 <0.037 <0.037 <0.037 <0.037 

49306 Chlorothalonil (E) 14 1.84 <0.035 1.839 <0.049 <0.049 <0.049 <0.049 

49305 Clopyralid 14 <0.041 <0.014 <0.041 <0.041 <0.041 <0.041 <0.041 

04031 Cycloate (E) 14 <0.054 <0.013 <0.054 <0.054 <0.054 <0.054 <0.054 

49304 Dacthal mono-acid 14 <0.072 <0.012 <0.072 <0.072 <0.072 <0.072 <0.072 

04039 Deethyldeisopropyl- 14 0.062 <0.010 0.018* 0.062 0.01 <0.060 <0.060 <0.060 

atrazine (E) 

04038 Deisopropylatrazine (E) 14 0.359 <0.044 0.359 <0.074 <0.074 <0.074 <0.074 

38442 Dicamba 14 0.638 <0.096 0.638 <0.096 <0.096 <0.096 <0.096 

49302 Dichlorprop 14 <0.050 <0.014 <0.050 <0.050 <0.050 <0.050 <0.050 

49301 Dinoseb 14 0.004 <0.012 0.004 <0.043 <0.043 <0.043 <0.043 

04033 Diphenamid 14 <0.058 <0.026 <0.058 <0.058 <0.058 <0.058 <0.058 

49300 Diuron 14 2.19 <0.015 0.344* 2.188 0.032 <0.079 <0.079 <0.079 

49297 Fenuron 14 <0.073 <0.032 <0.073 <0.073 <0.073 <0.073 <0.073 

61694 Flumetsulam (E) 14 <0.087 <0.011 <0.087 <0.087 <0.087 <0.087 <0.087 

38811 Fluometuron 14 0.025 <0.031 0.025 <0.062 <0.062 <0.062 <0.062 

50356 Imazaquin (E) 14 5.89 <0.016 5.891 0.094 <0.103 <0.103 <0.103 

50407 Imazethapyr (E) 14 <0.088 <0.017 <0.088 <0.088 <0.088 <0.088 <0.088 

61695 Imidacloprid 14 0.237 <0.007 0.237 <0.106 <0.106 <0.106 <0.106 

38478 Linuron 14 <0.069 <0.014 <0.069 <0.069 <0.069 <0.069 <0.069 

38482 MCPA 14 0.634 <0.016 0.132* 0.634 0.14 <0.058 <0.058 <0.058 

38487 MCPB (E) 14 <0.062 <0.015 <0.062 <0.062 <0.062 <0.062 <0.062 

50359 Metalaxyl 14 <0.057 <0.020 <0.057 <0.057 <0.057 <0.057 <0.057 

38501 Methiocarb (E) 14 <0.079 <0.008 <0.079 <0.079 <0.079 <0.079 <0.079 

49296 Methomyl (E) 14 <0.077 <0.004 <0.077 <0.077 <0.077 <0.077 <0.077 

61696 Methomyl oxime (E) 14 <0.011 <0.010 <0.011 <0.010 <0.010 <0.010 <0.010 

61697 Metsulfuron-methyl (E) 14 <0.114 <0.025 <0.114 <0.114 <0.114 <0.114 <0.114 

49294 Neburon 14 <0.075 <0.012 <0.075 <0.075 <0.075 <0.075 <0.075 

50364 Nicosulfuron 14 <0.065 <0.013 <0.065 <0.065 <0.065 <0.065 <0.065 

49293 Norflurazon (E) 14 <0.077 <0.016 <0.077 <0.077 <0.077 <0.077 <0.077 

49292 Oryzalin 14 0.089 <0.018 0.089 <0.071 <0.071 <0.071 <0.071 

38866 Oxamyl 14 <0.016 <0.012 <0.016 <0.016 <0.016 <0.016 <0.016 

50410 Oxamyl oxime (E) 14 <0.064 <0.013 <0.064 <0.064 <0.064 <0.064 <0.064 

49291 Picloram 14 <0.071 <0.020 <0.071 <0.071 <0.071 <0.071 <0.071 

49236 Propham 14 <0.072 <0.010 <0.072 <0.072 <0.072 <0.072 <0.072 

50471 Propiconazole 14 <0.064 <0.021 <0.064 <0.064 <0.064 <0.064 <0.064 

38538 Propoxur 14 0.03 <0.008 0.03 <0.059 <0.059 <0.059 <0.059 

98 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999–2001 
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Appendix 3. Summary statistics for pesticides in surface-water samples collected from the Mobile River Basin , 1999 – 2001—Continued 

[NWIS, National Water Information System; GC/MS, gas chromatography/mass spectrometry; <, less than; --, no value; *, value is estimated by using a logprobability regression to predict values of data below the detection limit; E, estimated concentration; HPLC/MS, high-performance liquid chromatography/mass 

spectrometry] 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Threemile Branch at North Boulevard at Montgomery, Alabama—January 2000 to September 2001 (Continued) 

parameter code 

Compound (HPLC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

38548 Siduron 

50337 Sulfometruron-methyl 

04032 Terbacil 

61159 Tribenuron-methyl (E) 

49235 Triclopyr 

14 

14 

14 

14 

14 

<0.093 

0.051 

<0.095 

<0.068 

0.088 

<0.017 

<0.009 

<0.010 

<0.009 

<0.022 

-- <0.093 

-- 0.051 

-- <0.095 

-- <0.068 

-- 0.088 

<0.093 

0.017 

<0.095 

<0.068 

<0.101 

<0.093 

<0.039 

<0.095 

<0.068 

<0.101 

<0.093 

<0.039 

<0.095 

<0.068 

<0.101 

<0.093 

<0.039 

<0.095 

<0.068 

<0.101 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Tombigbee River below Coffeeville Lock and Dam near Coffeeville, Alabama—January 1999 to December 2001 

parameter code Compound (GC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

82660 2,6-diethylaniline 19 <0.003 <0.002 <0.003 <0.003 <0.003 <0.002 <0.002 

49260 Acetochlor 19 0.016 <0.002 0.016 <0.004 <0.002 <0.002 <0.002 

46342 Alachlor 19 0.013 <0.002 0.013 <0.002 <0.002 <0.002 <0.002 

34253 Alpha-HCH 19 <0.005 <0.002 <0.005 <0.005 <0.002 <0.002 <0.002 

39632 Atrazine 19 2.86 0.018 0.295 2.86 0.225 0.102 0.042 0.018 

82673 Benfluralin 19 <0.010 <0.002 <0.010 <0.010 <0.002 <0.002 <0.002 

04028 Butylate 19 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 

82680 Carbaryl (E) 19 0.025 <0.003 0.025 <0.041 <0.041 <0.003 <0.003 

82674 Carbofuran (E) 19 <0.020 <0.003 <0.020 <0.020 <0.003 <0.003 <0.003 

38933 Chlorpyrifos 19 0.007 <0.004 0.007 <0.005 <0.005 <0.004 <0.004 

04041 Cyanazine 19 0.021 <0.004 0.021 <0.018 <0.018 <0.004 <0.004 

82682 Dacthal (DCPA) 19 <0.003 <0.002 <0.003 <0.003 <0.002 <0.002 <0.002 

04040 Deethylatrazine (E) 19 0.073 <0.006 0.013* 0.073 0.014 0.011 0.003 <0.006 

34653 p,p'-DDE 19 0.001 <0.002 0.001 <0.006 <0.006 <0.002 <0.002 

39572 Diazinon 19 0.018 <0.002 0.006* 0.018 0.008 0.004 <0.002 <0.002 

39381 Dieldrin 19 <0.005 <0.001 <0.005 <0.005 <0.001 <0.001 <0.001 

82677 Disulfoton 19 <0.021 <0.017 <0.021 <0.021 <0.017 <0.017 <0.017 

82668 EPTC 19 0.009 <0.002 0.009 <0.002 <0.002 <0.002 <0.002 

82663 Ethalfluralin 19 <0.009 <0.004 <0.009 <0.009 <0.004 <0.004 <0.004 

82672 Ethoprop 19 <0.005 <0.003 <0.005 <0.005 <0.003 <0.003 <0.003 

04095 Fonofox 19 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 <0.003 

39341 Lindane 19 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 <0.004 

82666 Linuron 19 <0.035 <0.002 <0.035 <0.035 <0.002 <0.002 <0.002 

39532 Malathion 19 <0.027 <0.005 <0.027 <0.027 <0.005 <0.005 <0.005 

82686 Methyl azinphos (E) 19 <0.050 <0.001 <0.050 <0.050 <0.001 <0.001 <0.001 

82667 Methyl parathion 19 <0.006 <0.006 <0.006 <0.006 <0.006 <0.006 <0.006 

39415 Metolachlor 19 0.634 0.003 0.052 0.634 0.039 0.013 0.006 0.003 

82630 Metribuzin 19 0.012 <0.004 0.012 <0.006 <0.006 <0.004 <0.004 

82671 Molinate 19 <0.004 <0.002 <0.004 <0.004 <0.004 <0.002 <0.002 

82684 Napropamide 19 <0.007 <0.003 <0.007 <0.007 <0.003 <0.003 <0.003 

39542 Parathion 19 <0.007 <0.004 <0.007 <0.007 <0.004 <0.004 <0.004 

82669 Pebulate 19 <0.004 <0.002 <0.004 <0.004 <0.004 <0.002 <0.002 

82683 Pendimethalin 19 0.01 <0.004 0.01 <0.010 <0.010 <0.004 <0.004 

82687 cis-Permethrin 19 <0.006 <0.005 <0.006 <0.006 <0.005 <0.005 <0.005 

82664 Phorate 19 <0.011 <0.002 <0.011 <0.011 <0.002 <0.002 <0.002 

Appendixes 99 
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Appendix 3. Summary statistics for pesticides in surface-water samples collected from the Mobile River Basin , 1999 – 2001—Continued 

[NWIS, National Water Information System; GC/MS, gas chromatography/mass spectrometry; <, less than; --, no value; *, value is estimated by using a logprobability regression to predict values of data below the detection limit; E, estimated concentration; HPLC/MS, high-performance liquid chromatography/mass 

spectrometry] 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Tombigbee River below Coffeeville Lock and Dam near Coffeeville, Alabama— 

January 1999 to December 2001 (Continued) 

parameter code 

Compound (GC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

04037 Prometon 19 

82676 Pronamide 19 

04024 Propachlor 19 

82679 Propanil 19 

82685 Propargite 18 

04035 Simazine 19 

82670 Tebuthiuron 19 

82665 Terbacil (E) 19 

82675 Terbufos 19 

82681 Thiobencarb 19 

82678 Triallate 19 

82661 Trifluralin 19 

0.014 

<0.004 

<0.010 

<0.011 

<0.023 

0.037 

0.026 

<0.034 

<0.017 

<0.005 

<0.002 

0.008 

<0.015 

<0.003 

<0.007 

<0.004 

<0.013 

<0.005 

<0.016 

<0.007 

<0.013 

<0.002 

<0.001 

<0.002 

0.007* 

0.015* 

0.013* 

0.014 

<0.004 

<0.010 

<0.011 

<0.023 

0.037 

0.026 

<0.034 

<0.017 

<0.005 

<0.002 

0.008 

0.009 

<0.004 

<0.010 

<0.011 

<0.023 

0.021 

0.013 

<0.034 

<0.017 

<0.005 

<0.002 

<0.009 

0.005 

<0.003 

<0.007 

<0.004 

<0.013 

0.013 

0.011 

<0.020 

<0.013 

<0.002 

<0.001 

<0.009 

<0.018 

<0.003 

<0.007 

<0.004 

<0.013 

0.008 

0.008 

<0.007 

<0.013 

<0.002 

<0.001 

<0.002 

<0.015 

<0.003 

<0.007 

<0.004 

<0.013 

<0.010 

<0.016 

<0.007 

<0.013 

<0.002 

<0.001 

<0.002 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Tombigbee River below Coffeeville Lock and Dam near Coffeeville, Alabama—January 2000 to December 2001 

parameter code 

Compound (HPLC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

39732 2,4-D 8 0.089 <0.077 0.089 0.048 <0.077 <0.077 <0.077 

50470 2,4-D methyl ester 8 <0.086 <0.086 <0.086 <0.086 <0.086 <0.086 <0.086 

38746 2,4-DB (E) 8 <0.054 <0.054 <0.054 <0.054 <0.054 <0.054 <0.054 

50355 2-hydroxyatrazine (E) 8 0.058 <0.193 0.032* 0.058 0.031 0.018 <0.193 <0.193 

61692 3,4-chlorophenyl-1- 8 <0.091 <0.091 <0.091 <0.091 <0.091 <0.091 <0.091 

methyl urea 

49308 3-hydroxycarbofuran 8 <0.062 <0.062 <0.062 <0.062 <0.062 <0.062 <0.062 

50295 3-ketocarbofuran (E) 8 <0.072 <0.072 <0.072 <0.072 <0.072 <0.072 <0.072 

49315 Acifluorfen 8 <0.062 <0.062 <0.062 <0.062 <0.062 <0.062 <0.062 

49312 Aldicarb (E) 8 <0.082 <0.082 <0.082 <0.082 <0.082 <0.082 <0.082 

49313 Aldicarb sulfone (E) 8 <0.160 <0.160 <0.160 <0.160 <0.160 <0.160 <0.160 

49314 Aldicarb sulfoxide (E) 7 <0.027 <0.027 <0.027 <0.027 <0.027 <0.027 <0.027 

50299 Bendiocarb 8 <0.061 <0.061 <0.061 <0.061 <0.061 <0.061 <0.061 

50300 Benomyl 8 <0.022 <0.022 <0.022 <0.022 <0.022 <0.022 <0.022 

61693 Bensulfuron-methyl 8 <0.048 <0.048 <0.048 <0.048 <0.048 <0.048 <0.048 

38711 Bentazon (E) 8 0.028 <0.019 0.028 <0.019 <0.019 <0.019 <0.019 

04029 Bromacil (E) 8 <0.081 <0.081 <0.081 <0.081 <0.081 <0.081 <0.081 

49311 Bromoxynil (E) 8 <0.057 <0.057 <0.057 <0.057 <0.057 <0.057 <0.057 

50305 Caffeine 8 0.021 <0.080 0.021 0.015 <0.080 <0.080 <0.080 

49310 Carbaryl 8 <0.063 <0.063 <0.063 <0.063 <0.063 <0.063 <0.063 

49309 Carbofuran 8 <0.057 <0.057 <0.057 <0.057 <0.057 <0.057 <0.057 

61188 Chloramben, methyl 8 <0.114 <0.114 <0.114 <0.114 <0.114 <0.114 <0.114 

ester (E) 

50306 Chlorimuron, ethyl 8 <0.037 <0.037 <0.037 <0.037 <0.037 <0.037 <0.037 

49306 Chlorothalonil (E) 8 <0.049 <0.049 <0.049 <0.049 <0.049 <0.049 <0.049 

49305 Clopyralid 8 <0.041 <0.041 <0.041 <0.041 <0.041 <0.041 <0.041 

04031 Cycloate (E) 8 <0.054 <0.054 <0.054 <0.054 <0.054 <0.054 <0.054 

100 Occurrence and Distribution of Nutrients, Suspended Sediment, and Pesticides in the Mobile River Basin, 1999–2001 
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Appendix 3. Summary statistics for pesticides in surface-water samples collected from the Mobile River Basin , 1999 – 2001—Continued 

[NWIS, National Water Information System; GC/MS, gas chromatography/mass spectrometry; <, less than; --, no value; *, value is estimated by using a logprobability regression to predict values of data below the detection limit; E, estimated concentration; HPLC/MS, high-performance liquid chromatography/mass 

spectrometry] 

NWIS 

of 

Minimum 95% 75% 50% 5% 

Tombigbee River below Coffeeville Lock and Dam near Coffeeville, Alabama— 

January 2000 to December 2001 (Continued) 

parameter code 

Compound (HPLC/MS) 

Number 

samples 

Concentration, in micrograms per liter 

Maximum Mean 25% 

49304 Dacthal mono-acid 8 <0.072 <0.072 <0.072 <0.072 <0.072 <0.072 <0.072 

04039 Deethyldeisopropyl- 8 0.016 <0.060 0.016 <0.060 <0.060 <0.060 <0.060 

atrazine (E) 

04038 Deisopropylatrazine (E) 8 0.011 <0.074 0.011 <0.074 <0.074 <0.074 <0.074 

38442 Dicamba 8 <0.096 <0.096 <0.096 <0.096 <0.096 <0.096 <0.096 

49302 Dichlorprop 8 <0.050 <0.050 <0.050 <0.050 <0.050 <0.050 <0.050 

49301 Dinoseb 8 <0.043 <0.043 <0.043 <0.043 <0.043 <0.043 <0.043 

04033 Diphenamid 8 <0.058 <0.058 <0.058 <0.058 <0.058 <0.058 <0.058 

49300 Diuron 8 0.034 <0.079 0.023* 0.034 0.03 0.016 0.011 0.011 

49297 Fenuron 8 <0.073 <0.073 <0.073 <0.073 <0.073 <0.073 <0.073 

61694 Flumetsulam (E) 8 <0.087 <0.087 <0.087 <0.087 <0.087 <0.087 <0.087 

38811 Fluometuron 8 0.024 <0.062 0.024 <0.062 <0.062 <0.062 <0.062 

50356 Imazaquin (E) 8 <0.103 <0.103 <0.103 <0.103 <0.103 <0.103 <0.103 

50407 Imazethapyr (E) 6 <0.088 <0.088 <0.088 <0.088 <0.088 <0.088 <0.088 

61695 Imidacloprid 8 <0.106 <0.106 <0.106 <0.106 <0.106 <0.106 <0.106 

38478 Linuron 8 <0.069 <0.069 <0.069 <0.069 <0.069 <0.069 <0.069 

38482 MCPA 8 <0.058 <0.058 <0.058 <0.058 <0.058 <0.058 <0.058 

38487 MCPB (E) 8 <0.062 <0.062 <0.062 <0.062 <0.062 <0.062 <0.062 

50359 Metalaxyl 8 <0.057 <0.057 <0.057 <0.057 <0.057 <0.057 <0.057 

38501 Methiocarb (E) 8 <0.079 <0.079 <0.079 <0.079 <0.079 <0.079 <0.079 

49296 Methomyl (E) 8 <0.077 <0.077 <0.077 <0.077 <0.077 <0.077 <0.077 

61696 Methomyl oxime (E) 8 <0.010 <0.010 <0.010 <0.010 <0.010 <0.010 <0.010 

61697 Metsulfuron-methyl (E) 8 <0.114 <0.114 <0.114 <0.114 <0.114 <0.114 <0.114 

49294 Neburon 8 <0.075 <0.075 <0.075 <0.075 <0.075 <0.075 <0.075 

50364 Nicosulfuron 8 <0.065 <0.065 <0.065 <0.065 <0.065 <0.065 <0.065 

49293 Norflurazon (E) 8 <0.077 <0.077 <0.077 <0.077 <0.077 <0.077 <0.077 

49292 Oryzalin 8 <0.071 <0.071 <0.071 <0.071 <0.071 <0.071 <0.071 

38866 Oxamyl 8 <0.016 <0.016 <0.016 <0.016 <0.016 <0.016 <0.016 

50410 Oxamyl oxime (E) 8 <0.064 <0.064 <0.064 <0.064 <0.064 <0.064 <0.064 

49291 Picloram 8 <0.071 <0.071 <0.071 <0.071 <0.071 <0.071 <0.071 

49236 Propham 8 <0.072 <0.072 <0.072 <0.072 <0.072 <0.072 <0.072 

50471 Propiconazole 8 <0.064 <0.064 <0.064 <0.064 <0.064 <0.064 <0.064 

38538 Propoxur 8 <0.059 <0.059 <0.059 <0.059 <0.059 <0.059 <0.059 

38548 Siduron 8 <0.093 <0.093 <0.093 <0.093 <0.093 <0.093 <0.093 

50337 Sulfometruron-methyl 8 0.021 <0.039 0.021 <0.039 <0.039 <0.039 <0.039 

04032 Terbacil 8 0.026 <0.095 0.026 <0.095 <0.095 <0.095 <0.095 

61159 Tribenuron-methyl (E) 7 <0.068 <0.068 <0.068 <0.068 <0.068 <0.068 <0.068 

49235 Triclopyr 8 <0.101 <0.101 <0.101 <0.101 <0.101 <0.101 <0.101 

Appendixes 101