This fact sheet introduces a study of

the nonpoint-source occurrence of

pesticides in water of the cotton-growing

areas of the Southern United States with

special emphasis on the Mississippi

Embayment (fig. 1). This study is being

conducted by the U.S. Geological Survey

(USGS) Organic Geochemistry Research

Group, which investigates the fate and

transport of agricultural chemicals in the

environment. The purpose of this fact

sheet is to give an overview of the cottongrowing areas of the United States, to

provide usage data for cotton pesticides

in the United States, to present

information on the types of pesticide

compounds and concentrations that have

been found thus far in the Mississippi

Embayment, and to discuss current areas

of cotton pesticide research.

Introduction

Contamination of water in the

Midcontinental United States from

pesticide application to row crops (corn

and soybeans) has been a major waterquality issue during the past decade.

Perhaps equally important to water

quality in the Southern United States is

the application of pesticides to cotton,

which receives three to five times greater

application of pesticides per acre than

does corn or soybeans. In spite of the

greater use of pesticides, few regional

water-quality studies have addressed

pesticide occurrence in water of the

Southern United States.

Cotton-growing areas of the United

States (fig. 1) extend from the East Coast

(The Carolinas) to the Mississippi

Embayment, the Texas High Plains, and

the arid deserts of the Southwest

(Arizona and California). These areas of

the country have different climate,

precipitation, and soil types, which result

in different weed and insect pressures, as

well as different runoff potentials;

therefore, pesticide-usage, runoff, and

leaching patterns are often different.

Because of these considerations, the

types and amounts of pesticides applied

may vary considerably throughout the

cotton-growing areas. For example,

fluometuron is a cotton herbicide used

primarily in Mississippi and in the

eastern coastal plain (fig. 2; Battaglin and

Goolsby, 1995) but is little used in other

cotton-growing areas.

The geographic usage information

displayed in figure 2 can be useful for

designing regional water-quality surveys

and for methods-development strategies

for a compound such as fluometuron.

Another method to visualize cotton

pesticide usage in the United States is the

bar graph shown in figure 3. The

compounds shown account for nearly all

of the pesticides used in cotton-growing

areas (Gianessi and Anderson, 1995).

The three most-used pesticides are

herbicides (monosodium methylarsonate,

trifluralin, and fluometuron).

Study Area

A major area for cotton production in

the United States is the Mississippi

Embayment (fig. 4). The area consists of

parts of Arkansas, Kentucky, Louisiana,

Mississippi, Missouri, and Tennessee.

Rainfall amounts of as much as 60 inches

per year and relatively flat, only slightly

permeable soils characterized by large

runoff volumes and low relief are typical

of this area. Major pesticides used in the

Index map

Mississippi

T ennessee

K entucky

Arkansas

Missouri

Louisiana

S tates encompassing the

Mississippi Embayment

No data or 0

1 – 2,500

2,501 – 10,000

10,001 – 30,000

30,001 – 70,000

More than 70,000

E stimated harvested

cotton, in acres

EX PLANAT ION

0 50 100 KILOMETERS

0 50 100 MILES

Figure 1. Estimated harvested cotton in the United States, 1987 (data from Battaglin and Goolsby, 1995)

U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet FS–022–98

May 1998

—E. Michael Thurman, Lisa R. Zimmerman, Elisabeth A. Scribner, and Richard H. Coupe Jr.

Occurrence of Cotton Pesticides in Surface Water of

The Mississippi Embayment
area include monosodium methylarsonate,

fluometuron, cyanazine, pendimethalin,

methyl parathion, and trifluralin.

Methods of Study

Surface-water samples were collected

at 64 sites in the Mississippi Embayment

from January-December 1996 in

conjunction with the USGS National

Water-Quality Assessment (NAWQA)

Program. The location of the sampling

sites is shown in figure 4. Fixed sites were

sampled weekly for 1 year, and

reconnaissance sites were sampled one

time. Samples were filtered through glassfiber filters (1.0 micron) and stored on ice

until analyzed at the USGS laboratory in

Lawrence, Kansas.

Water samples were extracted and

analyzed by gas chromatography/mass

spectrometry (GC/MS) for the detection

and quantitation of the major cotton

pesticides. The method consists of using

solid-phase extraction (SPE) for the

isolation of the compounds followed by

elution with ethyl acetate (an organic

solvent) and analysis by gas

chromatography with identification by

mass spectrometry using selected ion

detection (Thurman and others, 1990).

The detection limit was 0.05 μg/L

(micrograms per liter) for all herbicides

and 0.01 μg/L for all insecticides.

In addition to the standard approach of

GC/MS for chemical analyses, other

methods for the evaluation of pesticides

in the aquatic environment are being

used. Enzyme-linked immunosorbent

assay (ELISA) has been developed for

fluometuron (Strategic Diagnostics, Inc.,

Newark, Delaware). This immunoassay

is portable, provides rapid results, and is

less expensive than conventional

methods. Initial analyses have shown

very good correlation between GC/MS

and ELISA.

Three general factors are important in

defining transport, fate, and toxicity of

pesticides in the aquatic environment (fig.

5). Pesticide usage, such as illustrated in

figures 2 and 3, provides basic sources

information. Chemical structure affects

the physical properties and, thus, the

persistence and mobility of the pesticides.

Site hydrology determines runoff and

leaching potentials. Evaluation of all

factors will enable improved

understanding of the processes of

nonpoint-source contamination and of the

occurrence of cotton pesticides in surface

and ground water.

Occurrence of Cotton Pesticides

in Surface Water

The major herbicides and their

metabolites that have been detected in

surface water of the Mississippi

Embayment are shown in figure 6. The

most-detected compound was

fluometuron with a mean concentration

of 2.1 μg/L a median of 0.40 μg/L, and a

No data or 0

1 – 1,000

1,001 – 3,500

3,501 – 10,000

10,001 – 50,000

More than 50,000

Fluometuron use, in pounds

of active ingredient

EX PLANAT ION

Mississippi

Embayment

Figure 3. Cotton pesticide usage in the United States, 1990-93 (data from Gianessi and Anderson, 1995).

Figure 2. Fluometuron use in cotton-growing areas of the United States, 1987 (data from Battaglin and

Goolsby, 1995).

0

1,000,000

2,000,000

3,000,000

4,000,000

5,000,000

Herbicide

Insecticide

6,000,000

M onosodium

methylarsonate

Trifluralin

Fluometuron

M ethyl parathion

Cyanazine

Pendimethalin

Profenofos

Aldicarb

Norflurazon

M alathion

Thiodicarb

Disodium

mono- methanearsonate

Acephate

Glyphosate

Diuron

S ulprofos

Chlorpyrifos

Paraquat

Dicofol

Azinphos-methyl

Dicrotophos

Oxamyl

M etholachlor

Prometryn

Amount of active ingredients

applied annually, in pounds

Pesticide

33

35

37

92 90 88

B oundary of Mississippi

Embatment study unit of

the National Water-Quality

Assessment Program

Fixed sampling site

R econnaissance sampling

site

EX PLANAT ION

MIS SOUR I

AR K ANSAS

LOUIS IANA

MIS S IS S IPPI

T ENNE S S E E

K ENT UC K Y

0 25 50 75 100 KILOMETERS

0 25 50 75 100 MILES

Mississippi R iver Figure 4. Location of surface-water sampling sites in

the Mississippi Embayment.
maximum of 50 μg/L (fig. 6). The 

demethyl metabolites, demethylfluometuron and demethylnorflurazon, were 

also commonly detected. 

In general, cotton pesticides are 

slightly soluble in water, from 0.3 to 

1,000 mg/L (milligrams per liter). 

Experience from studies in the corn- and 

soybean-growing areas of the United 

States indicates that at a water solubility 

greater than 5 mg/L compounds are 

readily carried by surface runoff and 

occur in surface water. Cyanazine, 

fluometuron, and norflurazon have water 

solubilites greater than 5 mg/L. On the 

other hand, pesticides such as 

pendimethalin and trifluralin (fig. 3) have 

a solubility less than 1 mg/L and 

generally are not detected in surface 

runoff in the Mississippi Embayment. 

These low-solubility compounds are 

tightly bound to soil and are not readily 

transported to ground water. The 

pesticide-contaminated soil may be 

eroded at a later time and may be carried 

by streams as part of the suspended load 

along with the pesticides bound to the 

sediment. Analytical methods are 

currently (1998) being developed by the 

USGS to determine how pendimethalin 

and trifluralin are bound to soil. 

The seasonal distribution of total 

herbicides is shown in figure 7. Cotton 

has a long growing season, almost 6 

months, and herbicides may be applied 

throughout that period. Total 

concentrations are highest from May to 

August when they may reach 100 μg/L. 

During\x11the nongrowing season, total 

herbicide concentrations average 

approximately 11 μg/L. 

Insecticides were also detected in the 

surface water of the Mississippi 

Embayment, although not as frequently 

and at much lower concentrations than 

the herbicides. Figure 8 shows the 

detections of the insecticides monitored. 

Dicrotophos was the most frequently 

detected (35 percent). It is a highly 

soluble (1,000 mg/L water solubility) 

organophosphate insecticide that is used 

extensively (nearly 0.7 million pounds 

annually in the cotton-growing areas, see 

fig. 3). Methyl parathion was detected 

next most frequently, with 18 percent 

detections. It is the most-used insecticide 

in the cotton-growing areas, with more 

than 3.3 million pounds applied annually 

(fig. 3). However, because it is a volatile 

insecticide, it is detected less frequently 

and at lower concentrations in surface 

water than dicrotophos, which is much 

less volatile. The third most-detected 

compound was profenofos at 12 percent 

detections. This organophosphate 

insecticide is used nearly three times as 

much as dicrotophos, yet it is found in 

lower concentrations and less frequently. 

Apparently the shorter half-life of 

profenofos (about 7 days versus 10 to 15 

days for dicrotophos) permits it to be 

more rapidly decomposed in soil, and as 

a result, the parent compound occurs less 

frequently in surface water. 

Of the organochlorine insecticdes that 

were detected (fig. 8), endosulfan was 

detected most frequently (3 percent) and 

in the highest concentrations. This result 

is consistent with the fact that endosulfan 

is the only organochlorine that is still 

used legally in cotton-growing areas. 

Organochlorine insecticides, especially 

DDT, were used intensively on cotton 

during past years; therefore, more 

detailed monitoring by the USGS is 

underway for DDT and its metabolites 

using passive sampling methods, such as 

semipermeable membrane devices 

(SPMDs). Work with SPMDs shows that 

DDT and other organochlorine 

insecticides are present in surface water 

at detectable levels (Bastian and others, 

1997). 

Current Research 

Additional research by the USGS in 

the cotton-growing areas includes 

development of a bacterial-growth assay 

using the luminescent organism Vibrio 

fischeri. Results from this analytical 

F a te, 

tr a n s por t, 

a n d tox i ci ty 

P es ti ci de 

u s a ge 

S i te 

h ydrol ogy 

C h em i ca l 

s tr u ctu re 

Figure 5. Critical factors affecting the fate, transport, 

and toxicity of pesticides in the environment. 

9 0 th percentile 

1 0 th percentile 

P ercent detections 

7 5 th percentile 

M ean 

2 5 th percentile 

5 0 th percentile 

(median) 

66 

49 49

<1 

38 14 

57 

N um ber of s a m ples = 330 

<, les s than 

36 

46 

30 3 

C oncentration, in m icrogram s per liter 

C y ana zine 

0 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

C y anazineam ide 

Fluom eturon 

T rifluorom ethyla niline 

Dem ethylfluom eturon 

T rifluorom ethy l 

phenyl urea 

N orflurazon 

Dem ethylnorflurazon 

Prom etryn 

Deis opropylprom etryn 

T otal 

Figure 6. Distribution of detectable concentrations of major cotton herbicides and metabolites in 

surface-water samples from the Mississippi Embayment, January-December 1996. 

Figure 7. Concentrations of total cotton herbicides in all samples from the Mississippi Embayment, 

January-December 1996. 

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20 

40 

60 

80 

100 

120 

C oncentra tion, in m icrogram s per liter 

J an. Feb. M ar. A pr. 

C otton-grow ing s eas on 

N um ber of s am ples = 330 

M a y J une J uly 

1996 

A ug. S ept. O ct. N ov. Dec. 
method are being compared with 

pesticide concentrations determined by 

chemical analysis to identify the relations 

among chemical application and spatial 

and temporal variations in water quality. 

These bacterial-growth assays also have 

the potential to identify interactions 

between the many organic compounds 

found in surface and ground water of 

cotton-growing areas. 

Also, passive samplers are being tested 

by the USGS for the determination of 

some of the most insoluble insecticides, 

including DDT and its metabolites and 

the pyrethroids. The passive samplers 

include SPMDs and SPE disks. These 

methods are being used on both air and 

water samples from the Mississippi 

Embayment. 

Methods are also being developed by 

the USGS using high-performace liquid 

chromatography/mass spectrometry for 

the analysis of insecticides and their 

metabolites. The organophosphorus 

insecticide metabolites will be analyzed 

using this method. These metabolites 

may be mobile in surface and ground 

water; therefore, methods to analyze 

these compounds are needed in cottongrowing areas. 

Lastly, pesticides in other 

cottongrowing areas of the United States, 

including Texas, Arizona, and California, 

are being examined. 

References 

Bastian, K.C., Thurman, E.M., Kleiss, 

B.A., Coupe, R.H., Jr., Huckins, 

J.N., and Petty, J.D., 1997, 

Comparison of pesticide 

concentrations in semipermeable 

membrane devices and fish tissue 

from the Mississippi Delta: Abstract 

and poster presentation at the 18th 

Annual Meeting of the Society of 

Environmental Toxicology and 

Chemistry, San Francisco, 

California, November 16-20, 1997. 

Battaglin, W.A., and Goolsby, D.A., 

1995, Spatial data in geographic 

information system format on 

agricultural chemical use, land use, 

and cropping practices in the United 

States: U.S. Geological 

Survey\x11Water-Resources 

Investigations Report 94-4176, 87 p. 

Gianessi, L.P., and Anderson, J.E., 1995, 

Pesticide use in U.S. crop 

production- National data report: 

Washington, D.C., unpaginated. 

Thurman, E.M., Meyer, Michael, Pomes, 

Michael, Perry, C.A., and Schwab, 

A.P., 1990, Enzymed-linked 

immunosorbent assay compared to 

gas chromatography/mass 

spectrometry for the determination 

of triazine herbicides in water: 

Analytical Chemistry, v. 62, p. 2043-

2048. 

Acknowledgments 

Richard Rebich, Mississippi Delta 

Management Systems Evaluation Areas, 

Jackson, MS; Dr. David Shaw, 

Mississippi State University, Starkville, 

MS; Jim Huckins, Biological Resources 

Division of USGS, Columbia, MO; and 

Betsy Beal, Office of Pesticide Programs, 

U.S. Environmental Protection Agency, 

Washington, D.C. 

The use of firm names in this fact sheet 

is for identification purposes only and 

does not constitute endorsement by the 

U.S. Geological Survey. 

Research and Data Team 

Chad Bastian, Richard Coupe, Ken 

Hostetler, Smiley Irelan, Jason Kish, 

Clydeen Logan, Chris Robertson, 

Elisabeth Scribner, E. Michael Thurman, 

and Lisa Zimmerman. 

For more information, contact: 

E. Michael Thurman 

U.S. Geological Survey 

4821 Quail Crest Place 

Lawrence, Kansas 66049 

(785) 832-3559 

ethurman@usgs.gov 

Dicrotophos 

P rofenofos 

M ethy l para thion 

M ala thion 

S ulprofos 

E ndos ulfan 

Dieldrin 

E ndrin 

A ldrin 

C hlorpy riphos 

A zinphos -

m ethy l 

C hlordane 

Heptachlor 

T ota l 

0.5 

0.4 

0.3 

0.2 

0.1 

0 

0.6 

0.7 

0.8 

Concentration, in m icrogram s per liter

N um ber of s am ples = 60 

35 

18 

12 

12 

3 

3 

2 

2 2 

2 

48 

2 

0 0 

P ercent detections 

M inimum 

concentration 

7 5 th percentile 

5 0 th percentile (median) 

2 5 th percentile 

M aximum concentration 

O rganophos phate ins ecticide O rga nochlorine ins ecticide 

Figure 8. Concentrations of insecticides detected in surface-water samples from the Mississippi 

Embayment, January-December 1996.