U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2006–5169

Occurrence of Isoxaflutole, Acetamide, and 

Triazine Herbicides and Their Degradation 

Products in 10 Iowa Rivers Draining to the 

Mississippi and Missouri Rivers, 2004

Diketontrile of 

isoxaflutole

Benzoic acid of 

isoxaflutole

Isoxaflutole

Occurrence of Isoxaflutole, Acetamide, and 

Triazine Herbicides and Their Degradation 

Products in 10 Iowa Rivers Draining to the 

Mississippi and Missouri Rivers, 2004

By Elisabeth A. Scribner, Michael T. Meyer, and Stephen J. Kalkhoff

Scientific Investigations Report 2006–5169

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

P. Patrick Leahy, Acting Director

U.S. Geological Survey, Reston, Virginia: 2006

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Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Scribner, E.A., Meyer, M.T., and Kalkhoff, S.J., 2006, Occurrence of isoxaflutole, acetamide, and triazine herbicides 

and their degradation products in 10 Iowa rivers draining to the Mississippi and Missouri Rivers, 2004: U.S. 

Geological Survey Scientific Investigations Report 2006–5169, 84 p.
iii

Contents

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

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

Herbicide Usage....................................................................................................................................1

Previous Studies ...................................................................................................................................2

Iowa Department of Natural Resources..................................................................................2

U.S. Geological Survey Monitoring Networks ........................................................................2

Description of Current Study ..............................................................................................................3

Purpose and Scope of Report.............................................................................................................4

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

Sample Collection and Processing....................................................................................................5

Analytical Methods...............................................................................................................................5

Organic Geochemistry Research Laboratory .........................................................................5

Analysis of Isoxaflutole and Its Degradation Products................................................5

Materials .....................................................................................................................5

Preparation of Standards .........................................................................................6

Solid-Phase Extraction .............................................................................................7

Liquid Chromatography/Mass Spectrometry/Mass Spectrometry ...................7

Analysis of Acetamide and Triazine Herbicides and Their Degradation Products..7

National Water-Quality Laboratory...........................................................................................7

Quality Assurance........................................................................................................................................10

Organic Geochemistry Research Laboratory ................................................................................10

National Water-Quality Laboratory..................................................................................................10

Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation 

Products...........................................................................................................................................10

Summary........................................................................................................................................................32

References Cited..........................................................................................................................................32

Supplemental Information..........................................................................................................................35

Figures

1. Graph showing herbicide use in Iowa, 1990–2003 ................................................................. 2

2. Map showing location of Iowa Department of Natural Resources ambient streammonitoring sites in relation to U.S. Geological Survey streamflow-gaging stations.........3

3. Map showing location of Eastern Iowa Basin stream-monitoring trend sites and 

National Stream Accounting Network sites in Iowa in relation to U.S. Geological 

Survey streamflow-gaging stations...........................................................................................4

4. Map showing location of sampling sites on 10 Iowa rivers draining to the Mississippi 

and Missouri Rivers......................................................................................................................6

5. Chemical structures of isoxaflutole and isoxaflutole degradation products, diketonitrile 

and benzoic acid...........................................................................................................................7

6. Graph showing concentrations of isoxaflutole, diketonitrile, and benzoic acid in water 

samples collected from 10 rivers in Iowa, 2004.....................................................................25

7. Graphs showing concentrations of acetochlor, metolachlor, and their degradation 

products in water samples collected from 10 rivers in Iowa, 2004 ....................................29

8. Graph showing concentrations of triazine herbicides and their degradation products in 

water samples collected from 10 rivers in Iowa, 2004 .........................................................31
iv

Tables

1. Sampling sites and drainage areas on 10 Iowa rivers draining to the Mississippi and 

Missouri Rivers, 2004 ...................................................................................................................5

2. Herbicide compounds, laboratory method analysis codes, parameter codes, method 

numbers, and reporting limits analyzed by the U.S. Geological Survey Organic 

Geochemistry Research Laboratory for water samples collected from 10 Iowa rivers, 

2004 .................................................................................................................................................8

3. Pesticide compounds and laboratory reporting limits analyzed by the National WaterQuality Laboratory using laboratory schedule 2001 for water samples collected from 

10 Iowa rivers, 2004 ....................................................................................................................11

4. Concentrations of herbicides and their degradation products in quality-assurance 

samples collected from 10 Iowa rivers as determined by the U.S. Geological Survey 

Organic Geochemistry Research Laboratory, 2004.............................................................. 12

5. Percentage recoveries of compounds as determined by U.S. Geological Survey 

National Water-Quality Laboratory, using laboratory schedule 2001 for water samples 

collected from 10 Iowa rivers, 2004 ........................................................................................ 20

6. Summary of number and percentage of detections for herbicides and their 

degradation products analyzed by the U.S. Geological Survey Organic Research 

Laboratory for water samples collected from 10 rivers in Iowa, 2004...............................23

7. Concentrations of isoxaflutole and two degradation products analyzed by the U.S. 

Geological Survey Organic Geochemistry Research Laboratory for water samples 

collected from 10 rivers in Iowa, 2004.....................................................................................26

8. Concentrations of acetamide herbicides and their degradation products analyzed 

by the U.S. Geological Survey Organic Geochemistry Research Laboratory for water 

samples collected from 10 rivers in Iowa, 2004.....................................................................36

9. Concentrations of triazine and phenylurea herbicides and their degradation products 

analyzed by the U.S. Geological Survey Organic Geochemistry Research Laboratory 

for water samples collected from 10 rivers in Iowa, 2004 ...................................................50

10. Concentrations of selected pesticides and pesticide degradation products determined 

by the U.S. Geological Survey National Water-Quality Laboratory using laboratory 

schedule 2001 for water samples collected from 10 rivers in Iowa, 2004.........................65
Conversion Factors, Abbreviated Water-Quality Units, and 

Datum

Multiply By To obtain

acre 4,047 square meter (m2)

liter (L) 0.2642 gallon (gal)

microliter (μL) 2.642 x 10-7 gallon (gal)

micrometer (μm) 3.937 x 10-5 inch (in.)

mile (mi) 1.609 kilometer (km)

millimeter (mm) 0.03937 inch (in.)

nanogram (ng) 3.527 x 10-11 ounce (oz)

ounce, fluid (oz) 0.02957 liter (L)

pound (lb) 453.6 gram (g)

square mile (mi2) 2.590 square kilometer (km2)

Temperature can be converted to degrees Celsius ( ̊C) or degrees Fahrenheit ( ̊F) by the 

equations: 

  ̊C = 5/9 ( ̊F -32)

  ̊F = 9/5 ( ̊C) +32.

Abbreviated Water-Quality Units

microgram per liter (μg/L)

microgram per milliliter (μg/mL)

milligram per milliliter (mg/mL)

milliliter (mL)

nanogram per microliter (ng/μL)

Datum

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

During 2004, a study to document the occurrence of herbicides and herbicide degradation products was conducted for 

10 major Iowa rivers draining to the Missouri and Mississippi 

Rivers. Seventy-five water-quality samples were collected to 

measure isoxaflutole, acetamide, and triazine herbicides and 

their herbicide degradation products. An analytical method to 

measure isoxaflutole and its degradation products, diketonitrile 

and benzoic acid, was developed by the U.S. Geological Survey Organic Geochemistry Research Laboratory in Lawrence, 

Kansas, using vacuum manifold solid-phase extraction and 

liquid chromatography/mass spectrometry/mass spectrometry 

and is described in this report. 

Isoxaflutole, a low application rate preemergence herbicide for control of annual broadleaf weeds, is used extensively 

in Iowa. Findings from the study documented in this report 

indicate that isoxaflutole was designed to degrade quickly to 

diketonitrile, which appears to be more stable, and then to 

benzoic acid. Of the 75 samples collected to measure isoxaflutole, there were four detections of isoxaflutole, 56 detections of diketonitrile, and 43 detections of benzoic acid. Also, 

results of acetamide and triazine water-quality samples correlate with past studies, which indicate that herbicide degradation products are detected more frequently and often at higher 

concentrations in surface water than their parent compounds.

In addition to analysis of isoxaflutole and its degradation products, samples were analyzed by the USGS National 

Water-Quality Laboratory schedule 2001 for about 52 pesticides and their degradation products. 

Introduction

Iowa is one of the most productive agricultural areas in 

the United States for corn. Crops grown in the State are used 

to produce food, fuel, and fiber. Agricultural chemicals are 

needed for crops to control competing vegetation, insects, 

and fungus, and to supply sufficient nutrients. The use of 

pesticides and fertilizer has resulted in substantial crop yields, 

but certain climate conditions often result in agricultural 

chemicals being applied before rainfall that produces runoff 

and washing of the chemicals into streams and rivers. The 

presence of pesticides used in agricultural and urban areas has 

been documented in rivers and streams in Iowa and throughout 

the Midwestern United States. These contaminants can have 

an effect on water quality in local streams, downstream on 

major rivers such as the Mississippi and Missouri Rivers, and 

the Gulf of Mexico. 

Herbicide Usage

Modern agricultural practices in the United States often 

involve widespread use of herbicides for production of crops. 

Herbicide use is one factor that affects the concentrations of 

herbicides measured in Midwestern streams (Battaglin and 

Goolsby, 1999; Coupe and Goolsby, 1999; Scribner and others, 2000a) and an important reason for monitoring the water 

quality in streams. 

Isoxaflutole was patented by the Rhone-Poulenc Agriculture Company (Basel, Switzerland) in 1990. The Rhone-Poulenc Agriculture Company merged with AgrEvo (a company of 

Hoescht and Schering) in 1999 to form Aventis CropScience 

(Lyon, France), which was purchased by Bayer CropScience 

(Research Triangle Park, North Carolina) in 2001 (Luscombe 

and others, 1995). 

Isoxaflutole, a member of the benzoyl isoxazole family, 

is a low-application-rate preemergence herbicide for control 

of annual broadleaf weeds and some grasses in field corn and 

sugar cane (Pallet and others, 2001). For example, in Iowa 

isoxaflutole was applied at 0.07 lb active ingredient per acre 

per year during 2003 compared to atrazine, applied at 0.91 lb 

active ingredient per acre per year, and metolachlor, applied 

at 1.9 lb active ingredient per acre per year (U.S. Department 

of Agriculture, 2004). The intended strategy of the manufacturer is that under field conditions, isoxaflutole, also known by 

Occurrence of Isoxaflutole, Acetamide, and Triazine 

Herbicides and Their Degradation Products in 10 Iowa 

Rivers Draining to the Mississippi and Missouri Rivers, 

2004

By Elisabeth A. Scribner, Michael T. Meyer, and Stephen J. Kalkhoff
its trade name Balance, degrades quickly to the biologically 

active diketonitrile (Lin and others, 2002), followed by conversion of diketonitrile to benzoic acid. Diketonitrile also is more 

water soluble than isoxaflutole, and therefore, its transport to 

surface or ground water is a concern. 

Isoxaflutole was first used in 1999 in the United States, 

and usage has fluctuated from 213,000 lb in 1999, peaking 

at 439,000 lb in 2001, then decreasing to 321,000 lb in 2003 

(U.S. Department of Agriculture, 2004). Isoxaflutole usage 

in Iowa (fig. 1) was 62,000 lb in 1999 and 2000, peaking at 

229,000 lb in 2001, then decreasing to 135,000 lb in 2003. 

The historical use of acetochlor, alachlor, atrazine, 

cyanazine, metolachlor, and S-metolachlor in Iowa is also 

shown in figure 1. Acetochlor was introduced in 1994 with 

its registration contingent on it reducing the use of other corn 

herbicides. As a preemergent herbicide, acetochlor rapidly 

replaced alachlor. As can be seen in figure 1, acetochlor usage 

in Iowa was about 2 million lb in 1994 increasing to 9.5 million lb in 2003 compared to alachlor usage which was at its 

peak of more than 9 million lb in 1992 declining to about 

250,000 lb in 1998 (U.S. Department of Agriculture, 2004). 

Atrazine usage in Iowa stayed steady between 7 and 8.5 million lb during 1990 to 2003 regardless of the two decreases in 

the maximum application rate of atrazine recommended on the 

manufacturers’ labels during the 1990s (Scribner and others, 

2005). The manufacture of cyanazine was discontinued in 

1999, with distribution of existing supplies discontinued on 

September 30, 2002 (Scribner and others, 1998). Cyanazine 

usage in Iowa declined to about 1 million lb in 1998 (fig. 1). 

The formulation of metolachlor has been refined to include 

primarily the active S-isomer (S-metolachlor), which reduced 

required application rates substantially (Benbrook, 2001). 

Iowa usage of metolachlor and S-metolachlor can be seen as 

metolachlor peaked at a rate of 12 million lb in 1997, then 

declined to about 600,000 lb by 2003 while S-metolachlor 

rapidly increased from usage of 2.7 million lb in 2001 to more 

than 3 million lb in 2001 (fig. 1).

Previous Studies

The effects of agricultural and urban land use on the quality of Iowa’s rivers and streams have been assessed during the 

last 30 years by several State and Federal agencies. Monitoring networks have been established by the Iowa Department of 

Natural Resources (IADNR) and the U.S. Geological Survey 

(USGS) as described in the following sections.

Iowa Department of Natural Resources

The IADNR Ambient Water Monitoring Program 

conducts an ongoing assessment of the condition of Iowa’s 

ground- and surface-water resources and reports the results 

to the public (Iowa Department of Natural Resources, 2001). 

Beginning in 1995, water samples were collected by IADNR 

personnel at a network of 84 sites on Iowa’s rivers located 

upstream and downstream from Iowa’s larger urban areas. 

Figure 2 shows IADNR ambient stream-monitoring sites in 

relation to USGS streamflow-gaging stations. 

U.S. Geological Survey Monitoring Networks

The USGS National Stream Accounting Network 

(NASQAN) was begun in 1973 to provide nationally comparable information on the status of and trends in water quality 

(Hooper and others, 1997). Water-quality measurements were 

made quarterly at sites at the downstream end of most hydrologic accounting units to be consistent with the design of the 

national streamflow-gaging network. In 1995, the NASQAN 

program was redesigned to focus on monitoring water quality 

in four of the Nation’s largest rivers, of which the Mississippi 

River Basin is the largest. The chemical constituents measured include 52 water-soluble pesticides. Samples are collected from 6 to 15 times per year at various NASQAN sites. 

Iowa NASQAN sites are shown in relation to USGS gaging 

stations in figure 3.

Figure 1. Herbicide use in 

Iowa, 1990–2003 (data from 

U.S. Department of Agriculture, 2004).

1990 1992 1994 1996 1998 2000 2002 2004

0

5,000

10,000

15,000

Use, in thousands of pounds

Acetochlor

Alachlor

Cyanazine

Metolachlor

S-metolachlor

Isoxaflutole

Atrazine
In 1991, the USGS began the National Water-Quality 

Assessment (NAWQA) Program. The long-term goals of this 

program are to describe the status and trends in the quality of a 

large, representative part of the Nation’s surface- and groundwater resources and to identify the major factors that affect the 

quality of the resources. The NAWQA Program has identified more than 50 study units throughout the United States 

for which water quality was assessed (Gilliom and Hamilton, 

2006; Gilliom and others, 2006). The Eastern Iowa Basins 

(EIWA) study unit was selected as an important hydrologic 

system representative of an agricultural area in the Midwest. 

The EIWA study unit encompasses the Wapsipinicon, the 

Cedar, the Iowa, and the Skunk River Basins in eastern Iowa 

and southern Minnesota as shown in figure 3. 

Surface-water data collection activities in the EIWA study 

unit began in March 1996, and during the high-intensity phase 

of data collection (1996–98), water-quality samples were collected monthly from 12 sites on rivers and streams in the study 

unit. Two of these 12 sites were former NASQAN locations 

(Iowa River at Wapello—station 05465500; Skunk River at 

Augusta—station 05474000). As part of the trends network 

of NAWQA, 4 of the 12 EIWA sites continue to be sampled 

(fig. 3). Data are published annually in the Iowa annual water 

data report (Nalley and others, 2001). Continuous streamdischarge data are an integral part of the program, and thus 

streamflow gages are located at all NAWQA sites (fig. 3). 

Description of Current Study

More than 26,000 mi of rivers and perennial streams 

drain the approximately 56,000 mi2 of Iowa (Iowa Department of Natural Resources, 2001). Many of the major rivers 

drain directly to the Mississippi River, but a number of rivers 

in western Iowa drain to the Missouri River. To meet the 

objectives of this study, 10 sites were selected near the mouth 

of major rivers draining Iowa for sampling. Samples were 

collected monthly from March to September at each site, and 

high-flow samples were collected at 7 of the 10 sites 

Figure 2. Location of Iowa Department of Natural Resources (IADNR) ambient stream-monitoring sites in relation to U.S. 

Geological Survey streamflow-gaging stations (modified from Iowa Department of Natural Resources, 2001).

Introduction 

95° 94° 93° 92°

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Base from U.S. Geological Survey digital data, 1:100,000, 1991

Universal Transverse Mercator projection,

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Big Sioux

River Basin

Des Moines

River Basin

Raccoon

River Basin

Cedar

River Basin

Mississippi

River Basin

Iowa River Basin

Skunk River Basin

Des Moines and

Fox River Basins Platte, Grand, and

Chariton River Basins

Nishnabotna

and Nodway

River Basins

Boyer and

Missouri Main

Stem River 

Basins

Missouri, Floyd

River, Perry Creek

and MononaHarrison Ditch

Basins

Little Sioux and

Soldier River 

Basins

Turkey and

Maquoketa

River Basins

Mississippi,

Wapsipinicon River,

and Crow Creek 

Basins

River basin boundary

Iowa Department of Natural Resources ambient 

 stream-monitoring site

U.S. Geological Survey streamflow-gaging station

EXPLANATION
(stations 05412500, 05418600, 05422000, 06485500, 

06607500, 06609500, and 06810000; table 1) and analyzed 

for relevant constituents. The location of sampling sites is 

shown in figure 4, and sampling-site drainage areas are given 

in table 1. 

Purpose and Scope of Report

The main purpose of this report is to document the occurrence of the herbicide isoxaflutole and two of its degradation 

products (diketonitrile and benzoic acid) in 10 major rivers in 

Iowa that drain the Missouri and Mississippi Rivers (table 1) 

during the spring and summer of 2004. As part of quantifying 

isoxaflutole and its degradation products in rivers, the report 

describes an analytical method, using solid-phase extraction 

(SPE) and liquid chromatography/mass spectrometry/mass 

spectrometry (LC/MS/MS), developed by the USGS Organic 

Geochemistry Research Laboratory (OGRL), Lawrence, Kansas. The report also provides the results of analysis of waterquality samples for the occurrence of acetamide and triazine 

herbicides and their degradation products by two separate 

Figure 3. Location of Eastern Iowa Basin (EIWA) stream-monitoring trend sites and National Stream Accounting Network 

(NASQAN) sites in Iowa in relation to U.S. Geological Survey streamflow-gaging stations.

95° 94° 93° 92°

91°

96°

43°

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0 50 100 MILES

Base from U.S. Geological Survey digital data, 1:100,000, 1991

Universal Transverse Mercator projection,

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Big Sioux

River Basin

Des Moines

River Basin

Raccoon

River Basin

Cedar

River Basin

Mississippi

River Basin

Iowa River Basin

Skunk River Basin

Des Moines and

Fox River Basins Platte, Grand, and

Chariton River Basins

Nishnabotna

and Nodway

River Basins

Boyer and

Missouri Main

Stem River 

Basins

Missouri, Floyd

River, Perry Creek

and MononaHarrison Ditch

Basins

Little Sioux and

Soldier River 

Basins

Turkey and

Maquoketa

River Basins

Mississippi,

Wapsipinicon River,

and Crow Creek 

Basins

River basin boundary

Eastern Iowa Basin (EIWA) trend site

National Stream Accounting Network 

 (NASQAN) site

U.S. Geological Survey streamflow- gaging station

EXPLANATION

13-0028/fig03final.ai

Augusta

Wapello

Wapsipinicon

River Basin

MINNESOTA

IOWA

Mississippi River

EIWA study unit

Cedar River Basin

Iowa River Basin

Skunk River Basin

Index map
LC/MS methods at the OGRL. The USGS National WaterQuality Laboratory (NWQL), Lakewood, Colorado, analyzed 

for about 52 pesticides and degradation products.

Methods

Sample Collection and Processing

During 2004, samples were collected monthly from 

March to September using methods described in Shelton 

(1994) and equal-width increment sampling, which is a collection of composite samples across a section of stream with 

equidistant verticals and equal transit rates within each vertical 

that yields a representative sample of stream condition (Webb 

and others, 1999). The water samples were filtered through a 

0.7-μm pore-size baked glass-fiber filter, using an aluminum 

plate filter holder and a ceramic-piston fluid-metering pump 

with all Teflon tubing, into precleaned 123-mL amber glass 

bottles. All sampling equipment was cleaned with a Liquinox 

solution, rinsed thoroughly with tapwater, then rinsed with 

organic-free or reagent water, followed by a final rinse with 

methanol and organic-free water to remove traces of methanol. 

The equipment then was air dried. The filtrate was collected 

in six heat-cleaned 125-L amber glass bottles. The remainder 

of the water in the compositing container was used for onsite 

measurements of specific conductance, pH, and water temperature (Wilde and others, 1998). 

All samples were chilled immediately and shipped to the 

USGS OGRL in Lawrence, Kansas, and NWQL in Lakewood, 

Colorado, for analyses. Samples were refrigerated at approximately 4 o

C until analysis.

Analytical Methods

Analysis of herbicides was provided by the USGS OGRL 

and the USGS NWQL as described in this section.

Organic Geochemistry Research Laboratory

An analytical method was developed using vacuum 

manifold SPE and LC/MS/MS to measure isoxaflutole [5-

cyclopropyl-4-(2-methylsulfonyl-4-(trifluoromethylbenzoyl) 

isoxazole] and its degradation products, diketonitrile [1-(2-

methylsulfonyl-4-trifluoromethylphenyl)-2-cyano-3-cyclopropyl propan-1, 3-dione] and benzoic acid [2-methylsulphonyl4(trifluoromethyl) benzoic acid]. Chemical structures of these 

compounds are shown in figure 5. A detailed description of 

this method is provided in the following section. Analytical 

methods using SPE and LC/MS were developed to analyze 

water samples for acetamide and triazine herbicides (Scribner 

and others, 2000b). Herbicide compounds, method analysis, 

and reporting limits are listed in table 2.

Analysis of Isoxaflutole and Its Degradation Product

An analytical method for isoxaflutole and its degradation 

products was developed at the OGRL. The method includes 

SPE with LC/MS/MS and uses electrospray ionization (ESI) 

in negative-ion mode. The analytical method used to analyze 

isoxaflutole and its degradation products is currently (2006) 

undergoing USGS evaluation.

Materials

Isoxaflutole, diketonitrile, and benzoic acid were 

obtained from the U.S. Environmental Protection Agency 

(USEPA) repository (Fort Meade, Maryland). The internal 

Table 1. Sampling sites and drainage areas on 10 Iowa rivers draining to the Mississippi and Missouri Rivers, 

2004.

Map number

(fig. 4)

U.S. Geological Survey 

site identification 

number

Site name Drainage area 

(square miles)

Mississippi River Basin

1 05412500 Turkey River at Garber 1,545

2 05418600 Maquoketa River near Spragueville 1,635

3 05422000 Wapsipinicon River near DeWitt 2,330

4 05474000 Skunk River at Augusta 4,303

5 05490500 Des Moines River at Keosauqua 14,038

Missouri River Basin

6 06485500 Big Sioux River at Akron 8,424

7 06607500 Little Sioux River near Turin 3,526

8 06609500 Boyer River at Logan 871

9 06810000 Nishnabotna River above Hamburg 2,806

10 06904010 Chariton River near Moulton 740

Methods 
standard (ISTD), 2-4, dichlorophenoxyacetic acid-d3

, was 

obtained from Cambridge Isotope Laboratory (Andover, 

Massachusetts). The surrogate standard, alachlor ethanesulfonic acid (ESA)-D5

, was provided by Monsanto (St. Louis, 

Missouri). All solvents were HPLC (high-performance 

liquid chromatography) grade, and the acetic acid was ACS 

(American Chemical Society) certified. 

Preparation of Standards

Individual solutions of the ISTD, 2-4, dichlorophenoxyacetic acid-d3

, and the surrogate standard, alachlor ESA-d5, 

were prepared, using volumetric procedures, at a concentration 

of 0.615 ng/μL methanol from 1-mg/mL stock solution. An 

intermediate standard mix containing isoxaflutole, diketonitrile, and benzoic acid was prepared by diluting individual 

1-mg/mL stock solutions into acetonitrile to a concentration of 

12.3 ng/μL. Using volumetric procedures, a working standard 

mix of 0.123 ng/μL was prepared from the intermediate standard mix by diluting it 1:100 into 9:1 formic acid (1.1 percent 

aqueous) in reagent water and acetonitrile. 

Calibration curve solutions were prepared for extraction in new 4-oz amber bottles by adding 75 mL reagent 

water, 0.5 mL of 1-mg/mL aqueous humic acid solution, and 

0.25 mL water pollution (WP) minerals A and B. The working standard mix then was added to each calibration standard 

to obtain final concentrations of 0, 0.005, 0.010, 0.050, 0.100, 

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Index map

95° 94° 93° 92°

91°

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42°

41°

0 50 100 KILOMETERS

0 50 100 MILES

NEBRASKA

Missouri River drainage basin

Mississippi River drainage basin

Sampling site and map number

MISSOURI

EXPLANATION

ILLINOIS

WISCONSIN

MINNESOTA

SOUTH

DAKOTA

Missouri

River

Mississippi

River

Base from U.S. Geological Survey digital data, 1:100,000, 1991

Universal Transverse Mercator projection,

Zone 15

Figure 4. Location of sampling sites on 10 Iowa rivers draining to the Mississippi and Missouri Rivers.

 Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products in 10 Iowa Rivers, 2004
and 0.200 μg/L. Finally, reagent water was added to bring 

the final volume of the calibration solutions to 123 mL. The 

bottles then were capped and mixed well. 

Solid-Phase Extraction

Blank samples, standards, and environmental samples 

were prepared by adding 100 μL of 0.615-ng/μL surrogate 

and 100 μL of glacial acetic acid to all bottles. One hundred 

microliters (100 μL) of 0.615-ng/μL working standard solution 

was added to each matrix spike bottle. SPE cartridges were 

prepared by passing 5 mL of 50/50 methanol and acetonitrile 

and 5 mL of reagent water slowly through each cartridge. 

Samples were loaded onto the cartridges within 15 to 20 minutes under vacuum. Cartridges were washed by adding 3 mL 

of aqueous 1-percent formic acid under vacuum. Compounds 

then were eluted from the cartridge with two 4-mL aliquots of 

50/50 methanol/acetonitrile to each cartridge. Then 100 μL of 

0.615-ng/μL ISTD solution were added to each sample tube. 

Sample eluates were reduced to a volume of 200 μL using a 

Zymark turbovap at 45 oC. Sample extracts were transferred 

to 200-μL autosampler vials and stored in a freezer at -10 oC 

until analysis.

Liquid Chromatography/Mass Spectrometry/Mass 

Spectrometry

Samples were analyzed on an Agilent 1100 series liquid 

chromatography (LC) system (Wilmington, Delaware) and a 

Waters Quattro Micro API triple-stage quadrupole mass spectrometer (MS/MS) system in electrospray negative ionization 

mode (Milford, Massachusetts). A Keystone 250- x 4.6-mm 

C-18 analytical column was used to separate isoxaflutole and 

its degradation products (Bellefonte, Pennsylvania). The LC 

column was equilibrated with the mobile phase for approximately 2 hours prior to analysis. Method reporting limits are 

given in table 2. 

Analysis of Acetamide and Triazine Herbicides and Their 

Degradation Products 

Method number 0–2139–03 was used to analyze 6 acetamide parent herbicides and 26 acetamide degradation products. This method is identified by the USGS OGRL with the 

method analysis code of LCPD (Lee and Strahan, 2003). The 

method reporting limit for LCPD is 0.02 μg/L (table 2). 

Method number 0–2138–02 was used to analyze 6 triazine parent herbicides, 12 triazine degradation products, 

3 phenylurea parent compounds, and 1 phenylurea degradation 

product. This method is identified by the USGS laboratory 

with the method analysis code of LCEA (Lee and others, 2002). The method reporting limits for LCEA were 

0.025 μg/L for all triazine herbicides except deethylcyanazine, 

for which the reporting limit was 0.20 μg/L. The method 

reporting limit for phenylurea herbicides was 0.20 μg/L 

(table 2). 

National Water-Quality Laboratory

The NWQL analyzed 106 samples for 52 pesticides and 

degradation products using laboratory schedule 2001. Analytes for this laboratory schedule are listed in table 3. Details 

of the analytical methods for NWQL schedule 2001 can be 

found in Zaugg and others (1995), Lindley and others (1996), 

and Madsen and others (2003). Various laboratory reporting 

limits are reported in table 3. 

Figure 5. Chemical structures of isoxaflutole and isoxaflutole 

degradation products, diketonitrile, and benzoic acid.

Methods 

F3C

SO2CH3 O

O

N

F3C

SO2CH3 O

C

O

N

Diketonitrile of isoxaflutole [1-(2-methylsulfonyl-4-

trifluoromethylphenyl)-2-cyano-3-cyclopropyl 

propan-1, 3-dione]

F3C

SO2CH3 O

OH

Benzoic acid of isoxaflutole [2-methylsulfonyl-4-

(trifluoromethyl) benzoic acid]

soxaflutole [5-cyclopropyl-4-(2-methylsulfonyl-4-

(trifluoromethylbenzoyl) isoxazole] 
Table 2. Herbicide compounds, laboratory method analysis codes, parameter codes, method numbers, and reporting limits analyzed 

by the U.S. Geological Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 

10 Iowa rivers, 2004.

[USGS, U.S. Geological Survey; μg/L, micrograms per liter; ESA, ethanesulfonic acid; OXA, oxanilic acid; SAA, sulfynil acetic acid; --, USGS method 

under review]

Herbicide compound Laboratory method 

analysis code

USGS parameter 

code USGS method number Method reporting limit (μg/L)

Acetamide parent herbicides

 acetochlor LCPD 49260X O–2139–03 0.02

 alachlor LCPD 46342X O–2139–03 .02

 dimethenamid LCPD 61588X O–2139–03 .02

 flufenacet LCPD 62481X O–2139–03 .02

 metolachlor LCPD 39415X O–2139–03 .02

 propachlor LCPD 04024X O–2139–03 .02

Acetamide degradation products

 acetochlor deschloro LCPD 63778U O–2139–03 .02

 acetochlor ESA LCPD 61029Y O–2139–03 .02

 acetochlor hydroxy LCPD 63784U O–2139–03 .02

 acetochlor OXA LCPD 61030Y O–2139–03 .02

 acetochlor SAA LCPD 62847W O–2139–03 .02

 acetochlor/metolachlor ESA-2nd amide LCPD 62850W O–2139–03 .02

 acetochlor/metolachlor-2nd amide LCPD 63782U O–2139–03 .02

 alachlor deschloro LCPD 63777U O–2139–03 .02

 alachlor ESA LCPD 50009Y O–2139–03 .02

 alachlor ESA-2nd amide LCPD 62849W O–2139–03 .02

 alachlor hydroxy LCPD 63783U O–2139–03 .02

 alachlor OXA LCPD 61031Y O–2139–03 .02

 alachlor SAA LCPD 62848W O–2139–03 .02

 alachlor-2nd amide LCPD 63781U O–2139–03 .02

 dimethenamid deschloro LCPD 63779U O–2139–03 .02

 dimethenamid ESA LCPD 61951W O–2139–03 .02

 dimethenamid OXA LCPD 62482W O–2139–03 .02

 dimethenamid hydroxy LCPD 64045U O–2139–03 .02

 flufenacet ESA LCPD 61952W O–2139–03 .02

 flufenacet OXA LCPD 62483W O–2139–03 .02

 metolachlor deschloro LCPD 63780U O–2139–03 .02

 metolachlor ESA LCPD 61043Y O–2139–03 .02

 metolachlor OXA LCPD 61044Y O–2139–03 .02

 metolachlor hydroxy LCPD 63785U O–2139–03 .02

 propachlor ESA LCPD 62766W O–2139–03 .05

 Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products in 10 Iowa Rivers, 2004
Table 2. Herbicide compounds, laboratory method analysis codes, parameter codes, method numbers, and reporting limits analyzed 

by the U.S. Geological Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 

10 Iowa rivers, 2004.—Continued

[USGS, U.S. Geological Survey; μg/L, micrograms per liter; ESA, ethanesulfonic acid; OXA, oxanilic acid; SAA, sulfynil acetic acid; --, USGS method 

under review]

Herbicide compound Laboratory method 

analysis code

USGS parameter 

code USGS method number Method reporting limit (μg/L)

Acetamide degradation products—Continued

 propachlor OXA LCPD 62767W O–2139–03 0.02

Isoxaflutole parent herbicide

 isoxaflutole LCIX 62733U -- .003

Isoxaflutole degradation products

 benzoic acid LCIX 62656U -- .003

 diketonitrile LCIX 63011U -- .002

Phenylurea parent herbicides

 diuron LCEA 50374S O–2138–02 0.20

 fluometuron LCEA 38811S O–2138–02 .20

 linuron LCEA 38478S O–2138–02 .20

Phenylurea degradation product

 demethylfluometuron (DMFM) LCEA 61755S O–2138–02 .20

Triazine parent herbicides

 atrazine LCEA 39632S O–2138–02 .025

 bromacil LCEA 04029U O–2138–02 .025

 cyanazine LCEA 04041S O–2138–02 .025

 prometon LCEA 04037U O–2138–02 .025

 propazine LCEA 38535S O–2138–02 .025

 simazine LCEA 04035S O–2138–02 .025

Triazine degradation products

 deethylatrazine LCEA 04040S O–2138–02 .025

 deethylhydroxyatrazine LCEA 62676S O–2138–02 .025

 deethyldeisopropylatrazine/didealkylatrazine LCEA 04039S O–2138–02 .025

 deisopropylatrazine LCEA 04038S O–2138–02 .025

 deisopropylhydroxyatrazine LCEA 62678S O–2138–02 .025

 hydroxyatrazine LCEA 50355S O–2138–02 .025

 hydroxysimazine LCEA 63154U O–2138–02 .025

 cyanazine acid LCEA 61745S O–2138–02 .025

 cyanazine amide LCEA 61709S O–2138–02 .025

 deethylcyanazine LCEA 61749S O–2138–02 .20

 deethylcyanazine acid LCEA 61750S O–2138–02 .025

 deethylcyanazine amide LCEA 61751S O–2138–02 .025

Methods 
Quality Assurance

All water-quality measurements and water samples for 

this study were collected by USGS personnel in accordance 

with a written work plan for the study (on file with the USGS 

in Iowa City, Iowa). Field blank and equipment blank samples 

were collected to ensure cross contamination did not occur due 

to contaminated equipment. Replicate samples were collected 

to document analytical variability. 

Organic Geochemistry Research Laboratory 

Results of herbicide concentrations in qualityassurance samples collected during 2004 are shown in table 4. 

All samples were collected in duplicate or more. Analytical control was maintained by the use of carryover blanks, 

laboratory duplicates, laboratory spiked samples, and calibration verification standards. Types of quality assurance/quality 

control (QA/QC) samples collected during the study for acetamide parent and degradation products included 2 field blank, 

1 field replicate, 10 laboratory duplicate, and 8 laboratory 

spiked samples. QA/QC samples collected for triazine parent 

compounds and degradation products included one field blank, 

seven laboratory duplicate, and five laboratory spiked samples. 

QA/QC samples collected for isoxaflutole and degradation 

products included seven laboratory duplicate and eight laboratory spiked samples. Herbicides were not detected in any of 

the field or laboratory blanks. 

National Water-Quality Laboratory

Surrogate herbicides were added to all environmental and 

blank samples analyzed for pesticides by the USGS NWQL. 

Surrogates in samples analyzed by laboratory schedule 2001 

(table 3) were diazinon-d10 and alpha HCH-d6. Surrogate 

herbicides were similar in chemical properties to some target 

analytes but were not expected to be present in the environmental samples. Surrogate herbicides are used to assess extraction efficiency and to detect sample-handling problems in the 

laboratory. The percentage recoveries of surrogate compounds 

analyzed is shown in table 5. Diazinon-d10 had a maximum 

of 131 and minimum of 65 percent recovery of the 106 water 

samples analyzed, whereas alpha HCH-d6 had a maximum of 

114 and a minimum of 58 percent recovery, which indicates an 

overall acceptable method performance. 

Occurrence of Isoxaflutole, Acetamide, 

and Triazine Herbicides and Their 

Degradation Products

 A summation of the number and percentage of detections of herbicides and their degradation products analyzed by 

the USGS OGRL are presented in table 6. Of the 75 samples 

analyzed, isoxaflutole was only present in four samples, and 

these were collected during the postplanting (May–June) 

season. During this season, there were 27 samples analyzed 

for isoxaflutole at a 15-percent detection rate. This concurs 

with prior findings that isoxaflutole has a very short half-life 

of less than 24 hours and rapidly converts to diketonitrile (Pallett and others, 2001; Lin and others, 2002). After application, 

isoxaflutole becomes herbicidally active through opening 

of the isoxazole ring, becoming the diketonitrile degradation product. Then, diketonitrile is transformed further to a 

herbicidally inactive benzoic acid degradation product (Viviani 

and others, 1998). Diketonitrile (56 detections) and benzoic 

acid (43 detections) were present in samples collected from 

all three sampling periods. However, as shown in table 6, the 

maximum number and percentage of detections for both compounds occurred during the postplanting season with diketonitrile detected in all 27 samples (100 percent) and benzoic acid 

in 23 of the 27 samples (85 percent). 

The concentration results for isoxaflutole, diketonitrile, 

and benzoic acid are shown in figure 6 and table 7. Results 

show that the maximum concentration of isoxaflutole was 

0.077 μg/L, whereas diketonitrile had a maximum concentration of 0.552 μg/L, and the highest concentration for benzoic 

acid was 0.166 μg/L. Maximum concentrations for all three 

compounds appeared during the postplanting season. 

Because isoxaflutole is applied at a low application 

rate and has a very short half-life, a stable analytical method 

proved necessary to reach acceptable method detection and 

reporting limits. The method developed to analyze isoxaflutole and its degradation products by LC/MS/MS was an important breakthrough and contributed to an improved understanding of the occurrence, persistence, and transport of isoxaflutole 

and its degradation products in the environment.

Detections for five acetamide herbicides and their degradation products are summarized by number and percentage in 

table 6, which shows that metolachlor was the most frequently 

detected acetamide parent (59 of 60 samples) during all three 

sampling periods, followed by acetochlor (41/60). Ethanesulfonic acid (ESA) and oxanilic acid (OXA) degradation 

products of acetochlor (60/60 ESA and 60/60 OXA), alachlor 

(56/60 and 53/60), and metolachlor (60/60 and 60/60) were 

detected as frequently or more frequently than their parent 

compounds during all three sampling periods. 

Acetochlor, acetochlor ESA and OXA, metolachlor, and 

metolachlor ESA and OXA were detected at a 100-percent 

detection (29/29) frequency in water-quality samples collected 

during the postplanting season. Acetochlor was detected at a 

100-percent detection frequency in water-quality samples collected during the postplanting season (table 6). 

As shown in figure 7A and in table 8 at the back of this 

report, acetochlor had the highest concentration (8.6 μg/L) of 

all the analyzed acetamide compounds in samples collected 

during the postplanting season. The maximum concentrations 

of acetochlor ESA and OXA collected during the postplanting 

10 Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products in 10 Iowa Rivers, 2004
season were considerably less than their parent herbicide at 

2.9 and 2.3 μg/L, respectively (fig. 7A). 

The highest concentration for metolachlor was 

3.8 μg/L from samples collected during the postplanting 

season; however, metolachlor ESA had a maximum concentration of 2.9 μg/L, which was analyzed from a sample collected 

during the late summer (July–September) (fig. 7B). As can be 

seen from the analytical results in table 8, ESA and OXA 

products of acetochlor, alachlor, dimethenamid, and metolachlor were detected almost as frequently or more frequently 

than their parent herbicides. There were no detections of 

alachlor deschloro, alachlor hydroxy, alachlor 2nd amide, 

dimethenamid hydroxy, propachlor, propachlor ESA, and 

propachlor OXA.

Measurable amounts of atrazine, the most frequently 

detected triazine parent herbicide during all three sampling 

periods (64 detections of 67 samples), occurred in 19 of 

Table 3. Pesticide compounds and laboratory reporting limits analyzed by the National Water-Quality Laboratory, Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 Iowa rivers, 2004.

Pesticide compound

Laboratory reporting 

limit 

(micrograms per liter)

Pesticide compound

Laboratory reporting 

limit 

(micrograms per liter)

2,6-diethylaniline 0.006 fipronil sulfone .024

acetochlor .006 fonofos .003

alachlor .005 lindane .004

alpha-HCH .005 linuron .035

atrazine .007 malathion .027

azinphos-methyl .050 metolachlor 0.006

benfluralin .010 metribuzin .006

butylate .004 molinate .003

carbaryl .041 napropamide .007

carbofuran .020 p,p’-DDE .003

chlorpyrifos .005 parathion .010

cis-permethrin .006 parathion-methyl .015

cyanazine .018 pebulate .004

dacthal (DCPA) .003 pendimethalin .022

deethylatrazine (DEA) .006 phorate .011

desulfinylfipronil .012 prometon .010

desulfinylfipronil amide .029 propachlor .025

diazinon .005 propanil .011

dieldrin .009 propargite .023

disulfoton .021 propyzamide .004

EPTC (s-ethyl dipropylthiocarbamate) .004 simazine .005

ethalfluralin .009 tebuthiuron .016

ethoprophos .005 terbacil .034

fipronil .016 terbufos .017

fipronil sulfide .013 thiobencarb .010

tri-allate .006

trifluralin .009

Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products 11
Table 4. Concentrations of herbicides and their degradation products in quality-assurance samples collected from 10 Iowa rivers as determined by the U.S. Geological 

Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, 2004. [ESA, ethanesulfonic acid; FB, field blank; FR, field replicate; LD, laboratory duplicate; LS, laboratory spike; OXA, oxanilic acid; SAA, sulfynil acetic acid; <, less than; --, not detected]

Map 

number 

(fig. 4)

U.S. Geological Survey 

site identification 

number

Site name Sample type

Date of 

collection 

(month/

day/ year)

Collection 

time 

(24-hour)

Concentration, in micrograms per liter

Acetochlor Aceto- chlor deschloro Aceto- chlor ESA Ace- tochlor hydroxy Aceto- chlor OXA

Acetamide parent and degradation products

1 05412500 Turkey River at Garber LD 03/15/04 1100 0.04 -- 0.17 -- 0.22

LD 04/20/04 0950 <.02 -- .16 -- .05

LS 06/10/04 1000 1.1 1.3 1.3 -- 1.2

2 05418600 Maquoketa River near Spragueville LD 05/19/04 0800 .49 .02 .43 -- .44

LD 06/10/04 1300 .03 .03 .82 -- .42

3 05422000 Wapsipinicon River near DeWitt FB 05/18/04 1140 <.02 -- <.02 -- <.02

LS 05/18/04 1200 .56 -- .95 -- 1.0LS 05/25/04 1430 1.2 1.5 .80 -- 1.2

5 05490500 Des Moines River at Keosauqua LD 07/19/04 1600 .10 .02 .90 0.08 .596 06485500 Big Sioux River at Akron LD 04/13/04 0930 <.02 -- .10 -- .14

LS 05/12/04 1030 1.2 -- .92 -- 1.0

7 06607500 Little Sioux River near Turin LS 03/10/04 0830 .88 -- 1.2 -- 1.1

FB 05/11/04 1000 <.02 <.02 <.02 -- <.02

LS 05/24/04 1100 1.3 1.5 .98 -- 1.0

8 06609500 Boyer River at Logan FR 03/12/04 0930 <.02 -- .08 -- .15

LD 06/17/04 1000 .28 .02 .36 -- .71

9 06810000 Nishnabotna River above Hamburg LD 03/11/04 1030 <.02 -- .07 -- .09

LS 04/12/04 1300 1.0 -- 1.0 -- 1.1

LD 05/25/04 1045 .72 <.02 .43 -- .69

10 06904010 Chariton River near Moulton LD 05/17/04 1100 .06 .02 .22 -- .35

LS 07/19/04 1230 1.1 .99 1.0 1.1 .79

12 Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products in 10 Iowa Rivers, 2004
Table 4. Concentrations of herbicides and their degradation products in quality-assurance samples collected from 10 Iowa rivers as determined by the 

U.S. Geological Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, 2004. [ESA, ethanesulfonic acid; FB, field blank; FR, field replicate; LD, laboratory duplicate; LS, laboratory spike; OXA, oxanilic acid; SAA, sulfynil acetic acid; <, less than; --, not detected]

Map

number

(fig. 4)

Concentration, in micrograms per liter

Acetochlor

SAA

Acetochlor/

metolachlor

2nd

amide

Acetochlor/

metolachlor

ESA - 2nd

amide

Alachlor Alachlor deschloro Alachlor ESA Alachlor hydroxy Alachlor OXA Alachlor SAA

Acetamide parent and degradation products—Continued

1 0.08 <0.02 0.05 <0.02 -- 0.26 -- 0.07 <0.02

<.02 <.02 .03 <.02 <0.02 .40 -- .03 <.021.0 .86 .53 1.1 1.2 1.2 -- 1.1 .94

2 .13 <.02 .09 <.02 <.02 .49 -- .02 .04

.06 <.02 .13 <.02 <.02 .49 -- .02 <.02

3 <.02 <.02 <.02 <.02 <.02 <.02 -- <.02 <.02

1.0 .93 .58 .99 1.1 1.0 -- .98 .92

1.4 1.1 .60 1.3 1.6 1.2 -- 1.3 .95

5 .30 <.02 .35 <.02 <.02 .32 <0.02 .02 <.02

6 .04 -- .03 <.02 -- .07 -- .03 <.02

.77 1.0 .54 1.1 2.5 .92 -- 1.0 .76

7 1.2 -- .26 .93 -- .93 -- 1.1 1.6

<.02 <.02 <.02 <.02 <.02 <.02 -- <.02 <.02

1.1 .80 .46 1.0 1.4 1.1 -- 1.0 .96

8 .06 -- .07 <.02 -- .09 -- .06 <.02

.31 <.02 .05 <.02 <.02 <.02 -- <.02 <.02

9 <.02 -- .05 <.02 -- .08 -- .05 <.02

1.0 <.02 .54 1.0 <.02 1.0 -- 1.1 1.0

.34 <.02 .03 <.02 <.02 .02 -- .02 .11

10 .06 <.02 .03 <.02 <.02 .05 -- .02 <.02

1.1 .61 1.2 1.1 .97 1.1 .96 .84 .77

Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products 1
Table 4. Concentrations of herbicides and their degradation products in quality-assurance samples collected from 10 Iowa rivers as determined by the U.S. Geological 

Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, 2004. [ESA, ethanesulfonic acid; FB, field blank; FR, field replicate; LD, laboratory duplicate; LS, laboratory spike; OXA, oxanilic acid; SAA, sulfynil acetic acid; <, less than; --,not detected] 

Map

number

(fig. 4)

Concentration, in micrograms per liter

Alachlor

2nd

amide

Alachlor

ESA - 2nd

amide

Dimethenamid Dimeth- enamid deschloro Dimeth- enamid ESA Dimeth- enamid hydroxy Dimethen- amid OXA Flufenacet Flufenacet ESA

Acetamide parent and degradation products—Continued

1 -- <0.02 0.02 -- 0.05 -- 0.02 <0.02 <0.02

<0.02 <.02 <.02 -- <.02 -- <.02 <.02 <.02

1.0 .71 1.0 1.5 1.2 -- 1.1 1.2 1.0

2 <.02 <.02 .02 <.02 .03 -- <.02 .10 <.02

<.02 <.02 .03 <.02 .06 -- .03 <.02 <.02

3 <.02 <.02 <.02 -- <.02 -- <.02 <.02 <.02

.65 1.1 .84 -- 1.1 -- 1.1 .94 .98

1.1 1.3 1.1 1.3 1.7 -- 1.3 1.3 1.3

5 <.02 <.02 .11 <.02 .12 <0.02 .04 <.02 <.02

6 <.02 <.02 <.02 -- .02 -- <.02 <.02 <.02

1.1 1.3 2.6 -- .85 -- 1.2 1.1 .95

7 -- .97 .92 -- 1.7 -- 1.0 .95 1.0

<.02 <.02 <.02 <.02 <.02 -- <.02 <.02 <.02

1.0 1.2 1.0 1.0 1.2 -- 1.2 .94 1.0

8 -- <.02 <.02 -- <.02 -- <.02 <.02 <.02

<.02 <.02 <.02 <.02 <.02 -- <.02 .26 .03

9 -- <.02 <.02 -- <.02 -- <.02 <.02 <.02

.79 1.1 .95 -- 1.1 -- 1.2 1.1 1.1

<.02 <.02 .42 <.02 .06 -- .12 <.02 .02

10 <.02 <.02 <.02 <.02 .03 -- .02 <.02 <.02

.90 .49 2.0 1.5 3.0 2.7 .90 1.0 .90

14 Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products in 10 Iowa Rivers, 2004
Table 4. Concentrations of herbicides and their degradation products in quality-assurance samples collected from 10 Iowa rivers as determined by the U.S. 

Geological Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, 2004. —Continued[ESA, ethanesulfonic acid; FB, field blank; FR, field replicate; LD, laboratory duplicate; LS, laboratory spike; OXA, oxanilic acid; SAA, sulfynil acetic acid; <, less than; --, not detected] 

Map

number

(fig. 4)

Concentration, in micrograms per liter

Flufenacet

OXA Metolachlor Metolachlor deschloro Metolachlor hydroxy Metolachlor ESA Metolachlor OXA Propachlor Propachlor ESA Propachlor OXA

Acetamide parent and degradation products—Continued

1 <0.02 0.07 -- -- 0.39 0.12 <0.02 <0.05 <0.02

<.02 <.02 -- -- .63 .07 <.02 <.05 <.02

.62 1.0 1.2 -- 1.3 1.1 1.1 <.05 .51

2 <.02 .19 <.02 -- 1.7 .16 <.02 <.05 <.02

<.02 .10 <.02 -- 1.9 .28 <.02 <.05 <.02

3 <.02 <.02 <.02 -- <.02 <.02 <.02 <.05 <.02

.52 .80 -- -- 1.1 1.0 .86 <.05 .41.91 1.1 1.4 -- .63 1.2 1.3 <.05 .77

5 <.02 .27 <.02 0.08 1.6 .33 <.02 <.05 <.026 <.02 .08 -- -- .48 .13 <.02 <.05 <.02

.71 1.1 -- -- .72 .91 1.0 <.05 .44

7 .30 .96 -- -- 1.5 1.1 .92 <.05 .29

<.02 <.02 <.02 -- <.02 <.02 <.02 <.02 <.02

.54 .98 1.2 -- .99 1.0 .96 <.05 .42

8 <.02 .14 -- -- .21 .25 <.02 <.05 <.02

.03 .48 <.02 -- .29 .23 <.02 <.05 <.02

9 <.02 .03 -- -- .14 .14 <.02 <.05 <.02

.48 .96 -- -- 1.1 1 .89 <.05 .4.02 2 <.02 -- .42 .45 <.02 <.05 <.02

10 <.02 .08 .07 -- .23 .28 <.02 <.05 <.02

.86 1.4 1.4 2.2 1.3 .94 .94 <.05 .33

Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products 1
Table 4. Concentrations of herbicides and their degradation products in quality-assurance samples collected from 10 Iowa rivers as determined by the U.S. Geological 

Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, 2004. —Continued[ESA, ethanesulfonic acid; FB, field blank; FR, field replicate; LD, laboratory duplicate; LS, laboratory spike; OXA, oxanilic acid; SAA, sulfynil acetic acid; <, less than; --, not detected]

Map

number

(fig. 4)

U.S. Geological

survey site

identification 

number

Site name Sample type

Date of

collection

(month/

day/

year)

Collection

time

(24-hour)

Concentration, in micrograms per liter

Atrazine Deethyl- atrazine Deethyl- hydroxy- atrazine Deisopro- pyl- atrazine Deiso- propyl- hydroxy- atrazine

Triazine parent and degradation products

1 05412500 Turkey River at Garber LD 05/19/04 1200 3.1 0.35 <0.025 0.15 <0.0252 05418600 Maquoketa River near Spragueville LS 03/15/04 1700 .83 .94 .76 .85 1.1

LS 03/29/04 1500 .83 .89 1.0 .87 1.0

3 05422000 Wapsinicon River near DeWitt LS 05/18/04 1200 <.025 .70 1.1 .78 .82

LD 06/16/04 1230 1.4 .36 <.025 .14 <.025

5 05490500 Des Moines River at Keosauqua LS 06/14/04 1400 .70 .75 1.3 .81 .81

LD 09/13/04 1330 .19 .09 <.025 .04 .03

6 06485500 Big Sioux River at Akron LD 03/09/04 1200 .06 .04 <.025 <.025 <.025

7 06607500 Little Sioux near Turin FB 05/11/04 1000 <.025 <.025 <.025 <.025 <.025

8 06609500 Boyer River at Logan LD 05/23/04 1015 18 1.9 .53 1.2 .039 06810000 Nishnabotna River above Hamburg LD 04/12/04 1300 .04 .04 <.025 <.025 <.025

LD 05/10/04 1230 24 1.1 <.025 .42 <.025

10 06904010 Chariton River near Moulton LS 04/22/04 1320 .81 .74 1.0 .67 .98

1 Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products in 10 Iowa Rivers, 2004
Table 4. Concentrations of herbicides and their degradation products in quality-assurance samples collected from 10 Iowa rivers as determined by the U.S. Geological 

Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, 2004. —Continued[ESA, ethanesulfonic acid; FB, field blank; FR, field replicate; LD, laboratory duplicate; LS, laboratory spike; OXA, oxanilic acid; SAA, sulfynil acetic acid; <, less than; --, not detected]

Map

number

(fig. 4)

Concentration, in micrograms per liter

Didealkylatrazine Hydroxy- atrazine Bromacil Cyanazine Cyanazine amide Cyanazine acid Deethylcy- anazine Deethyl- cyanazine acid Deethyl- cyanazine amide

Triazine parent and degradation products—Continued

1 0.36 0.11 <0.025 <0.025 <0.025 <0.025 <0.20 <0.025 <0.0252 .72 .85 .79 1.2 1.2 1.2 1.1 1.0 1.2

.88 1.1 .87 1.4 1.5 1.5 1.5 1.1 1.4

3 .77 1.1 .66 1.0 1.2 1.1 1.1 1.5 1.1

.23 .14 <.025 <.025 <.025 <.025 <.20 <.025 <.025

5 .99 1.1 .69 1.1 1.4 .97 1.2 1.2 1.4

.10 .19 <.025 <.025 <.025 <.025 <.20 <.025 <.025

6 <.025 .29 <.025 <.025 <.025 <.025 <.20 <.025 <.0257 <.025 <.025 <.025 <.025 <.025 <.025 <.20 <.025 <.0258 1.2 .08 <.025 .03 .24 <.025 .11 1.4 <.0259 .26 .08 <.025 <.025 <.025 <.025 <.20 .52 <.025

.13 .87 <.025 <.025 <.025 <.025 <.20 .32 <.025

10 .73 1.1 .59 1.0 1.3 1.1 1.1 1.5 1.1

Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products 1
Table 4. Concentrations of herbicides and their degradation products in quality-assurance samples collected from 10 Iowa rivers as determined by 

the U.S. Geological Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, 2004. —Continued[ESA, ethanesulfonic acid; FB, field blank; FR, field replicate; LD, laboratory duplicate; LS, laboratory spike; OXA, oxanilic acid; SAA, sulfynil acetic acid; <, less than; --, not detected]

Map

number

(fig. 4)

Concentration, in micrograms per liter

Prometon Propazine Simazine Hydroxysimazine Diuron Fluometuron Demethyl- fluometuron Linuron

Triazine parent and degradation products—Continued

1 <0.025 <0.025 <0.025 <0.025 <0.20 <0.20 <0.20 <0.20

2 -- .86 .89 .82 .73 .90 1.0 .95

-- .86 .79 1.1 1.0 1.1 1.1 1.1

3 .82 .70 .70 .84 .78 .90 .84 .91

<.025 <.025 <.025 <.025 <.20 <.20 <.20 <.20

5 <.025 .67 .72 1.0 .94 .94 .98 .86

<.025 <.025 <.025 <.025 <.20 <.20 <.20 <.20

6 -- <.025 <.025 <.025 <.20 <.20 <.20 <.207 <.025 <.025 <.025 <.025 <.20 <.20 <.20 <.208 <.025 .13 .08 .04 <.20 <.20 <.20 <.209 -- <.025 <.025 <.025 <.20 <.20 <.20 <.20

<.025 .22 .08 <.025 <.20 <.20 <.20 <.20

10 -- .85 .70 .91 1.1 .92 .82 1.1

1 Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products in 10 Iowa Rivers, 2004
Table 4. Concentrations of herbicides and their degradation products in quality-assurance samples collected from 10 Iowa rivers as determined by the U.S. Geological Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, 2004. —Continued

[ESA, ethanesulfonic acid; FB, field blank; FR, field replicate; LD, laboratory duplicate; LS, laboratory spike; OXA, oxanilic acid; SAA, sulfynil acetic acid; <, less than; --, not detected]

Map

number

(fig. 4)

U.S. Geological

survey site

identification number

Site name Sample type Date of collection (month/day/year) Collection time (24-hour) Concentration, in micrograms per liter Isoxaflutole Diketonitrile Benzoic acid

Isoxaflutole and degradation products

1 05412500 Turkey River at Garber LD 06/10/04 1000 <0.003 0.011 0.005

LS 07/21/04 1130 .087 .136 .148

LS 08/17/04 1445 .068 .077 .100LS 09/14/04 1300 .082 .074 .110

2 05418600 Maquoketa River near Spragueville LD 03/29/04 1500 <.003 <.002 <.003

LD 05/19/04 0800 <.003 .017 .007

3 05422000 Wapsipinicon River near DeWitt LS 05/18/04 1200 .048 .084 .096

LS 05/25/04 1430 .030 .096 .111

5 05490500 Des Moines River at Keosauqua LS 03/18/04 1230 .039 .056 .108

LS 04/22/04 0910 .032 .062 .103

6 06485500 Big Sioux River at Akron LD 03/09/04 1200 <.003 .003 .014

9 06810000 Nishnabotna River above Hamburg LD 05/10/04 1230 .084 .097 .067

LD 07/12/04 1230 <.003 .020 .012

10 06904010 Chariton River near Moulton LS 06/14/04 1050 .071 .085 .120

LD 08/16/04 1030 <.003 .003 .009

Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products 1
Table 5. Percentage recoveries of compounds as determined by U.S. Geological Survey National Water-Quality Laboratory, 

Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 rivers in Iowa, 2004.

Map

number

(fig. 4)

U.S. Geological

survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Percentage recovery

alpha-HCH-d6 Diazinon-d10

1 05412500 Turkey River at Garber 03/15/04 1100 105 113

04/20/04 0950 96 120

05/19/04 1200 93 120

05/24/04 1100 98 127

06/10/04 1000 100 114

07/21/04 1130 89 102

08/17/04 1445 92 102

09/14/04 1300 92 105

2 05418600 Maquoketa River near Spragueville 03/15/04 1700 107 117

03/29/04 1500 101 118

04/20/04 1510 108 131

05/19/04 0800 93 117

05/25/04 1000 95 122

06/10/04 1300 101 115

07/21/04 0720 92 104

08/17/04 1025 92 91

09/14/04 1000 91 101

3 05422000 Wapsipinicon River near DeWitt 03/17/04 0830 109 125

04/15/04 0830 99 118

05/18/05 1200 91 121

05/25/04 1400 100 128

06/16/04 1230 94 117

07/20/94 1200 93 98

08/17/04 0745 89 95

09/14/04 0730 94 103

4 05474000 Skunk River at Augusta 03/17/04 1430 105 119

04/15/04 1345 96 112

05/18/04 0730 94 117

06/16/04 0900 95 121

07/20/04 0800 94 101

20 Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products in 10 Iowa Rivers, 2004
Table 5. Percentage recoveries of compounds as determined by U.S. Geological Survey National Water-Quality Laboratory, 

Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 rivers in Iowa, 2004.—Continued

Map

number

(fig. 4)

U.S. Geological

survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Percentage recovery

alpha-HCH-d6 Diazinon-d10

4 05474000 Skunk River at Augusta 08/16/04 1615 91 105

09/13/04 1530 93 101

5 05490500 Des Moines River at Keosauqua 03/18/04 1230 108 118

04/22/04 0910 98 122

05/17/04 1400 94 115

06/14/04 1400 95 119

07/19/04 1600 97 104

08/16/04 1330 84 95

09/13/04 1330 95 99

6 06485500 Big Sioux River at Akron 0309/04 1200 110 130

04/13/04 0930 102 122

05/12/04 1030 98 116

05/26/04 1300 102 124

06/02/04 1215 96 98

07/14/04 1030 88 97

08/11/04 0940 94 110

09/08/04 0730 93 98

09/17/04 1230 85 98

7 06607500 Little Sioux River near Turin 03/10/04 0830 114 125

04/13/04 1400 100 113

05/11/04 1020 97 114

05/24/04 1100 99 122

06/08/04 0850 95 108

06/17/04 1230 104 124

07/13/04 1000 85 102

08/10/04 0900 83 90

09/08/04 1100 90 96

09/20/04 1145 86 102

Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products 21
Table 5. Percentage recoveries of compounds as determined by U.S. Geological Survey National Water-Quality Laboratory, 

Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 rivers in Iowa, 2004.—Continued

Map

number

(fig. 4)

U.S. Geological

survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Percentage recovery

alpha-HCH-d6 Diazinon-d10

8 06609500 Boyer River at Logan 03/12/04 0930 109 117

04/14/04 0730 102 118

05/11/04 1300 98 108

05/23/04 1015 93 121

06/08/04 1130 95 105

06/17/04 1000 103 125

07/13/04 1230 58 65

08/10/04 1130 96 116

09/07/04 1530 93 96

9 06810000 Nishnabotna River above Hamburg 03/11/04 1030 106 115

03/29/04 1230 92 115

04/12/04 1300 97 114

05/10/04 1230 90 113

05/15/04 1045 95 122

06/07/04 1245 96 109

07/12/04 1230 78 107

08/09/04 1230 91 106

09/07/04 1230 93 98

10 06904010 Chariton River near Moulton 03/18/04 0900 108 120

04/22/04 1320 101 128

05/17/04 1100 96 121

06/14/04 1050 98 120

07/19/04 1230 98 115

08/16/04 1030 90 102

09/13/04 1030 88 93

22 Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products in 10 Iowa Rivers, 2004
Table 6. Summary of number and percentage of detections of herbicides and their degradation products analyzed by the U.S. 

Geological Survey Organic Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004. 

[ESA, ethanesulfonic acid; OXA, oxanilic acid; SAA, sulfynil acetic acid; n, number of samples]

Herbicide compound

Number of detections Percentage of detections

Preplanting

(March–

April)

Postplanting

(May–June)

Late

summer

(July–Sept.)

Preplanting

(March–

April)

Postplanting

(May–June)

Late

summer

(July–Sept.)

Isoxaflutole parent and degradation products

n = 21 n = 27 n = 27 n = 21 n = 27 n = 27

Isoxaflutole 0 4 0 0 15 0

Diketonitrile 13 27 16 62 100 59

Benzoic acid 7 23 13 33 85 48

Acetamide parent and degradation products

n = 21 n = 29 n = 10 n = 21 n = 29 n = 10

Acetochlor 9 29 3 43 100 30

Acetochlor deschloro 0 22 2 0 76 20

Acetochlor ESA 21 29 10 100 100 100

Acetochlor hydroxy 0 0 4 0 0 40

Acetochlor OXA 21 29 10 100 100 100

Acetochlor SAA 15 27 6 71 93 60

Acetochlor/metolachlor 2nd amide 0 8 0 0 28 0

Acetochlor/metolachlor ESA 2nd amide 20 28 10 95 97 100

Alachlor 0 3 0 0 10 0

Alachlor ESA 21 26 9 100 90 90

Alachlor OXA 21 25 7 100 86 70

Alachlor SAA 0 12 0 0 41 0

Alachlor ESA 2nd amide 5 6 0 24 21 0

Dimethenamid 6 23 0 29 79 0

Dimethenamid deschloro 0 1 0 0 3 0

Dimethenamid ESA 14 22 7 67 76 70

Dimethenamid OXA 6 18 5 29 62 50

Flufenacet 1 14 0 5 48 0

Flufenacet ESA 2 6 0 10 21 0

Flufenacet OXA 0 5 0 0 17 0

Metolachlor 20 29 10 95 100 100

Metolachlor deschloro 0 2 1 0 7 10

Metolachlor ESA 21 29 10 100 100 100

Metolachlor OXA 21 29 10 100 100 100

Metolachlor hydroxy 0 0 4 0 0 40

Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products 2
22 (86 percent) preplanting (March–April) samples analyzed 

by the triazine herbicide method, 29 of 29 (100 percent) 

postplanting (May–June) samples, and 16 of 16 (100 percent) 

late summer (July–September) samples (table 6). Deethylatrazine (91 percent detection) occurred more frequently than 

atrazine (86 percent) in the preplanting-season samples, and 

both compounds were detected in all samples during the latesummer season. As can be seen in table 6, three other atrazine 

degradation products, deisopropylatrazine (32/100/88 percent), 

didealkylatrazine (95/100/75 percent), and hydroxyatrazine 

(95/100/63 percent), also occurred frequently during the three 

seasons in the 10 Iowa rivers sampled. 

As shown in figure 8 and in table 9 at the back of this 

report, atrazine was not only the most frequently detected 

herbicide but also had the maximum concentration of 21 μg/L 

during the postplanting season. This maximum concentration occurred in a sample from the Nishnabotna River above 

Hamburg, Iowa (fig. 4). The atrazine degradation products 

deethylatrazine, didealkylatrazine, and hydroxyatrazine also 

were detected frequently during all three seasons. It is of 

importance to note that deethylcyanazine acid, a degradation product of cyanazine, also was detected during all three 

sampling seasons (table 6). The manufacture of cyanazine 

was discontinued on December 31, 1999, but the hydrologic 

system still contains the “fingerprint” of past cyanazine use.

There were no detections for the uracil herbicide, bromacil, nor the triazine degradation products, cyanazine amide, 

cyanazine acid, and deethylcyanazine amide. The triazine 

method used in this study also analyzes for three phenylurea 

herbicides, diuron, fluometuron, and linuron, and one degradation product, demethylfluometuron. There were no detections of the phenylurea parent compounds nor the degradation 

product, demethylfluometuron. 

Analytical results for concentrations of selected pesticides and their degradation products determined by the USGS 

NWQL schedule 2001 are shown in table 10 at the back of 

this report. NWQL schedule 2001 (table 3) contains 52 parent 

pesticides and degradation products. Twenty-eight pesticide herbicides were detected above various reporting limits 

(table 10). Atrazine, deethylatrazine, a triazine degradation 

product, and metolachlor were detected in all of the 106 analyzed water samples. The highest concentration was atrazine 

with an estimated concentration of 42 μg/L, followed by metolachlor with a concentration of 3.9 μg/L, and deethylatrazine 

with an estimated concentration of 0.67 μg/L.

This study reaffirms several previous findings of herbicides and their degradation products from the 1980s through 

the mid-1990s, including the fact that large concentrations 

of herbicides were flushed from cropland and transported 

in response to late spring and early summer rainfall and that 

Table 6. Summary of number and percentage of detections of herbicides and their degradation products analyzed by the U.S. 

Geological Survey Organic Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—

Continued 

[ESA, ethanesulfonic acid; OXA, oxanilic acid; SAA, sulfynil acetic acid; n, number of samples]

Herbicide compound

Number of detections Percentage of detections

Preplanting

(March–

April)

Postplanting

(May–June)

Late

summer

(July–Sept.)

Preplanting

(March–

April)

Postplanting

(May–June)

Late

summer

(July–Sept.)

Triazine parent and degradation products

n = 22 n = 29 n = 16 n = 22 n = 29 n = 16

Atrazine 19 29 16 86 100 100

Deethylatrazine 20 29 16 91 100 100

Deethylhydroxyatrazine 0 2 0 0 7 0

Deisopropylatrazine 7 29 14 32 100 88

Deisopropylhydroxyatrazine 0 2 1 0 7 6

Didealkylatrazine 21 29 12 95 100 75

Hydroxyatrazine 21 29 10 95 100 63

Cyanazine 0 1 0 0 3 0

Deethylcyanazine acid 11 12 3 50 41 19

Propazine 0 10 0 0 34 0

Simazine 1 9 1 5 31 6

24 Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products in 10 Iowa Rivers, 2004
herbicides and their degradation products were detected year 

round in streams (Thurman and others, 1991, 1992, 1994; 

Scribner and others, 1993, 1998, 2000a,b, 2005; Meyer and 

others, 1996; Thurman and Fallon, 1996; Schnoebelen and 

others, 2003). 

Another significant finding of this study comparable to 

previous studies revealed that herbicide degradation products 

commonly were detected as frequently or more frequently than 

their parent herbicide. These data agree with past studies of 

Iowa ground water and rivers (Kolpin and others, 1996, 1997, 

1998, 2000, 2001, 2004; Kalkhoff and others, 1998, 2003; 

Battaglin and others, 2003, 2005; Scribner and others, 2004).

Isoxaflutole is applied in Iowa at a rate that is 8 percent 

of the rate of atrazine application and 4 percent of the rate of 

metolachlor application and is only applied to 24 percent of 

the number of acres to which atrazine is applied (U.S. Department of Agriculture, 2004). Thus, the frequent detection of 

the herbicidally active degradation product of isoxaflutole, 

diketonitrile, and its degradation product, benzoic acid, was 

unexpected. 

The water-quality data resulting from this study are 

important to understanding effects of herbicides on the 

surface-water resources locally in Iowa and nationally in the 

Mississippi and Missouri Rivers. The data also can be used to 

provide information so that decisions regarding the development, management, and protection of these resources may be 

improved.

Figure 6. Concentrations of isoxaflutole, diketonitrile, and benzoic acid in water samples collected from 10 rivers 

in Iowa, 2004.

Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products 2

0.001

0.010

0.10

1.0

Concentration, in micrograms per liter

Diketonitrile

Benzoic acid

Isoxaflutole

Diketonitrile

Benzoic acid

Isoxaflutole

Diketonitrile

Benzoic acid

Isoxaflutole

Compound and time interval

Preplanting

(March−April)

Postplanting

(May−June)

Late summer

(July−September)

EXPLANATION

Percentile—Percentage of analyses equal 

 to or less than indicated values

95th percentile

75th percentile

25th percentile

Interquartile

range

5th percentile

Median

Reporting limit

(0/21) (0/27)

(16/27)

(13/27)

(11/27)

(4/27)

(27/27)

(23/27)

(13/21)

(7/21)

Number of samples

Number of detections
Table 7. Concentrations of isoxaflutole and two degradation products analyzed by the U.S. Geological Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.

[<, less than]

Map

number

(fig. 4)

U.S. Geological 

Survey site 

identification 

number

Site name

Date of

collection

(month/day/

year)

Collection

Time

(24-hour)

Concentration, 

in micrograms per liter

IsoxaflutoleDiketonitrileBenzoic 

acid

1 05412500 Turkey River at Garber 03/15/04 1100 <0.003 <0.002 <0.003

04/20/04 0950 <.003 <.002 <.003

05/19/04 1200 <.003 .035 .006

05/24/04 1115 <.003 .092 .050

06/10/04 1000 <.003 .010 .005

07/21/04 1130 <.003 .004 <.003

08/17/04 1445 <.003 <.002 <.003

09/14/04 1300 <.003 <.002 <.003

2 05418600 Maquoketa River near 

Spragueville

03/15/04 1700 <.003 <.005 <.003

03/29/04 1500 <.003 <.002 <.003

04/20/04 1510 <.003 <.002 <.003

05/19/04 0800 <.003 .015 .005

05/25/04 1015 <.003 .010 .005

06/10/04 1300 <.003 .003 <.003

07/21/04 0720 <.003 <.002 <.003

08/17/04 1025 <.003 <.002 <.003

09/14/04 1000 <.003 <.002 <.003

3 05422000 Wapsipinicon River near DeWitt 03/17/04 0830 <.003 .002 .005

04/15/04 0830 <.003 <.002 <.003

05/18/04 1140 <.003 .002 <.003

05/18/04 1200 <.003 .007 .003

05/25/04 1430 <.003 .027 .013

06/16/04 1230 <.003 .018 .009

07/20/04 1200 <.003 .017 .012

08/17/04 0745 <.003 .002 <.003

09/14/04 0730 <.003 .010 <.003

4 05474000 Skunk River at Augusta 03/17/04 1430 <.003 .002 <.003

04/15/04 1345 <.003 <.002 <.003

05/18/04 0730 <.003 .036 .006

2 Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products in 10 Iowa Rivers, 2004
Table 7. Concentrations of isoxaflutole and two degradation products analyzed by the U.S. Geological Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[<, less than]

Map

number

(fig. 4)

U.S. Geological 

Survey site 

identification 

number

Site name

Date of

collection

(month/day/

year)

Collection

Time

(24-hour)

Concentration, 

in micrograms per liter

IsoxaflutoleDiketonitrileBenzoic 

acid

4 05474000 Skunk River at Augusta 06/16/04 0900 <0.003 0.066 0.101

07/20/04 0800 <.003 .008 .003

08/16/04 1615 <.003 <.002 <.003

09/13/04 1530 <.003 <.002 <.003

5 05490500 Des Moines River at Keosauqua 03/18/04 1230 <.003 .002 .003

04/22/04 0910 <.003 .002 <.003

05/17/04 1400 <.003 .015 .004

06/14/04 1400 <.003 .100 .038

07/19/04 1600 <.003 .039 .014

08/16/04 1330 <.003 .002 .006

09/13/04 1330 <.003 .010 .019

6 06485500 Big Sioux River at Akron 03/09/04 1200 <.003 .003 .016

04/13/04 0930 <.003 <.002 <.003

05/12/04 1030 <.003 .007 <.003

05/26/04 1300 <.003 .042 .016

07/14/04 1030 <.003 .006 .008

08/11/04 0940 <.003 <.002 <.003

09/08/04 0730 <.003 <.002 <.003

7 06607500 Little Sioux River near Turin 03/10/04 0830 <.003 .002 .008

04/13/04 1400 <.003 .002 <.003

05/11/04 1000 <.003 .004 <.003

05/11/04 1020 .008 .090 .007

05/24/04 1100 .003 .141 .051

06/08/04 0850 <.003 .011 .003

07/13/04 1000 <.003 .012 .005

09/08/04 1100 <.003 <.002 <.003

8 06609500 Boyer River at Logan 03/12/04 0930 <.003 .002 .007

04/14/04 0730 <.003 .002 <.003

05/11/04 1300 <.003 .012 .003

Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products 2
Table 7. Concentrations of isoxaflutole and two degradation products analyzed by the U.S. Geological Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[<, less than]

Map

number

(fig. 4)

U.S. Geological 

Survey site 

identification 

number

Site name

Date of

collection

(month/day/

year)

Collection

Time

(24-hour)

Concentration, 

in micrograms per liter

IsoxaflutoleDiketonitrileBenzoic 

acid

8 06609500 Boyer River at Logan 05/23/04 1015 0.006 0.552 0.166

06/08/04 1130 <.003 .013 .003

07/13/04 1230 <.003 .008 .004

09/07/04 1330 <.003 .007 .016

9 06810000 Nishnabotna River above 

Hamburg

03/11/04 1030 <.003 .003 .006

04/12/04 1300 <.003 .002 <.003

05/10/04 1230 .077 .378 .045

05/25/04 1045 <.003 .079 .048

06/07/04 1245 <.003 .010 .006

07/12/04 1230 <.003 .020 .012

09/07/04 1230 <.003 .003 <.003

10 06904010 Chariton River near Moulton 03/18/04 0900 <.003 .005 .003

04/22/04 1320 <.003 .003 <.003

06/14/04 1050 <.003 .024 .036

07/19/04 1230 <.003 .011 .009

08/16/04 1030 <.003 <.002 .011

09/13/04 1030 <.003 .005 .007

2 Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products in 10 Iowa Rivers, 2004
Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products 2

Figure 7. Concentrations of acetochlor, metolachlor, and their degradation products in water samples collected from 

10 rivers in Iowa, 2004.

(A) Acetochlor and its degradation products Acetochlor Acetochlor ethanesulfonic acid Acetochlor oxanilic acid Acetochlor deschloro Acetochlor hydroxy Acetochlor sulfynil acetic acid Acetochlor/metolachlor 2nd amide Acetochlor Acetochlor ethanesulfonic acid Acetochlor oxanilic acid Acetochlor deschloro Acetochlor hydroxy Acetochlor sulfynil acetic acid Acetochlor/metolachlor 2nd amide Acetochlor/metolachlor ESA 2nd amide

Acetochlor

Acetochlor

ethanesulfonic acid

Acetochlor

oxanilic acid

Acetochlor

deschloro

Acetochlor

hydroxy

Acetochlor

sulfynil acetic acid

Acetochlor/metolachlor

 2nd amide

Acetochlor/metolachlor

ESA 2nd amide

Acetochlor/metolachlor

ESA 2nd amide

0.010

0.10

1.0

10

Concentration, in micrograms per liter

Reporting limit

(9/21)

(0/21)(0/21) (0/21) (0/29) (2/10) (0/10)

(21/21)

(21/21)

(15/21)

(20/21)

(29/29)

(29/29)

(29/29)

(22/29)

(27/29)

(8/29)

(28/29)

(3/10)

(10/10)

(10/10)

(10/10)

(4/10)

(6/10)

EXPLANATION

Percentile—Percentage of analyses equal 

 to or less than indicated values

95th percentile

75th percentile

25th percentile

Interquartile

range

5th percentile

Median

(15/21)

Number of samples

Outlier

Number of detections

Compound and time interval

Preplanting

(March−April)

Postplanting

(May−June)

Late summer

(July−September)
Figure 7. Concentrations of acetochlor, metolachlor, and their degradation products in water samples collected 

from 10 rivers in Iowa, 2004.—Continued

0.010

0.10

1.0

10

Metolachlor

Metolachlor hydroxy

Metolachlor deschloro

Metolachlor oxanilic acid

Metolachlor ethanesulfonic

acid

Metolachlor

Metolachlor hydroxy

Metolachlor deschloro

Metolachlor oxanilic acid

Metolachlor ethanesulfonic

acid

Metolachlor

Metolachlor hydroxy

Metolachlor deschloro

Metolachlor oxanilic acid

Metolachlor ethanesulfonic

acid

Reporting limit

Concentration, in micrograms per liter

(20/21)

(29/29)

(29/29)

(29/29)

(10/10)

(10/10)

(10/10)

(1/10)

(4/10)

(2/29)

(21/21)

(21/21)

(0/21) (0/21) (0/29)

EXPLANATION

Percentile—Percentage of analyses equal 

 to or less than indicated values

95th percentile

75th percentile

25th percentile

Interquartile

range

5th percentile

Median

(20/21)

Number of samples

Outlier

Number of detections

(B) Metolachlor and its degradation products

Compound and time interval

Preplanting

(March−April)

Postplanting

(May−June)

Late summer

(July−September)
Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products 1

Figure 8. Concentrations of triazine herbicides and their degradation products in water samples collected from 

10 rivers in Iowa, 2004.

EXPLANATION

Percentile—Percentage of analyses equal 

 to or less than indicated values

95th percentile

75th percentile

25th percentile

Interquartile

range

5th percentile

Median

(17/31)

Number of samples

Outlier

Number of detections

Compound and time interval

Preplanting

(March−April)

Postplanting

(May−June)

Late summer

(July−September)

0.01

0.10

1.0

10

100

Concentration, in micrograms per liter

Simazine

Propazine

Deethylcyanazine acid

Cyanazine

Didealkylatrazine

DeisopropylhydroxyatrazineDeisopropylhydroxyatrazineDeisopropylhydroxyatrazine

Deethylhydroxyatrazine

Deisopropylatrazine

Deethylatrazine

Atrazine

Simazine

Propazine

Deethylcyanazine acid

Cyanazine

Didealkylatrazine

Deethylhydroxyatrazine

Deisopropylatrazine

Deethylatrazine

Atrazine

Simazine

Propazine

Deethylcyanazine acid

Cyanazine

Didealkylatrazine

Deethylhydroxyatrazine

Deisopropylatrazine

Deethylatrazine

Atrazine

Reporting limit

(20/22)

(7/22)

(0/22)

(0/22) (0/22) (0/16) (0/16)

(0/16)

(3/16)

(1/16)

(1/16)

(12/16)

(0/22)

(21/22)

(11/22)

Hydroxyatrazine

(21/22)

(29/29)

(29/29)

(29/29)

Hydroxyatrazine

(29/29)

(29/29)

(1/29)

(12/29)

(10/29) (2/29)

(2/29)

(16/16)

Hydroxyatrazine

(10/16)

(14/16)

(1/22)

(19/22)

(9/29)

(16/16)
Summary

Iowa is one of the most productive agricultural areas in 

the United States. Pesticides are needed for crops to control 

competing vegetation, insects, and fungus. The use of herbicides has produced substantial crop yields. 

The use of isoxaflutole, which was registered in 1998, has 

increased rapidly in the Midwestern United States, but there 

is limited understanding of its environmental fate. However, 

it is known that isoxaflutole degrades to a biologically active 

degradation product, diketonitrile, which is more stable, and 

further degradation of diketonitrile produces a nonbiologically 

active benzoic acid degradation product. 

The main purpose of this report is to document the occurrence of the herbicide isoxaflutole and its degradation products 

from samples collected from 10 major rivers draining Iowa 

to the Missouri and Mississippi Rivers and to compare their 

occurrence with that of more commonly measured herbicides 

such as acetochlor, atrazine, and metolachlor. Herbicide use 

is one factor that affects the concentrations of herbicides measured in Midwestern rivers and a vital reason for monitoring 

the water quality in these rivers. 

An analytical method to quantify isoxaflutole and its two 

degradation products was developed by the U.S. Geological 

Survey (USGS) Organic Geochemistry Research Laboratory 

using solid-phase extraction (SPE) and liquid chromatography/mass spectrometry/mass spectrometry (LC/MS/MS). 

Two separate methods also were used to provide the results of 

analysis for the occurrence of acetamide and triazine herbicides, and their degradation products. The USGS National 

Water-Quality Laboratory schedule 2001 was used to analyze 

52 pesticides and degradation products.

Analytical results of 75 water samples show that isoxaflutole was detected in only four of the samples collected 

during the postplanting (May–June) season, whereas diketonitrile was detected in 56 water samples and benzoic acid was 

detected in 43 water samples collected from all three sampling periods. Metolachlor was the most frequently detected 

acetamide parent (59 of 60 samples) during all three sampling 

periods, followed by acetochlor (41/60). Ethanesulfonic 

acid and oxanilic acid degradation products of acetochlor 

(60/60 ESA and 60/60 OXA), alachlor (56/60 and 53/60), and 

metolachlor (60/60 and 60/60) were detected as frequently or 

more frequently than their parent compounds. Atrazine was 

the most detected triazine parent compound with 64 detections 

of 67 samples during all three sampling periods, whereas the 

triazine degradation products of deethylatrazine, didealkylatrazine, hydroxyatrazine, and deisopropylatrazine were detected 

in 65, 62, 61, and 50 samples, respectively, which is similar to 

other reported conclusions of the detection frequency of the 

atrazine parent and its degradation.

Findings of the isoxaflutole study by the USGS include 

an improved understanding of the occurrence of the herbicide 

isoxaflutole and its degradation products in the hydrologic 

environment. Analytical results of the acetamide and triazine herbicides are consistent with previous studies, which 

show that large amounts of herbicides and their degradation 

products are flushed into streams with runoff. Also, the study 

confirmed previous findings that these herbicides occur as 

frequently or more frequently than their parent herbicide. 

The results of this study provide an important data set for 

future use. 

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environmental occurrence of herbicides—the importance 

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Supplemental Information

Supplemental Information 
Table 8. Concentrations of acetamide herbicides and their degradation products analyzed by the U.S. Geological Survey Organic 

Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.

[ESA, ethanesulfonic acid; OXA, oxanilic acid; SAA, sulfynil acetic acid; <, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological Survey 

site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-

hour)

Concentrations, in micrograms per liter

Acetochlor

Acetochlor

deschloro

Acetochlor

ESA

Acetochlor

hydroxy

Acetochlor

OXA

1 05412500 Turkey River at Garber 03/15/04 1100 0.04 -- 0.16 -- 0.23

04/20/04 0950 <.02 -- .22 -- .06

05/19/04 1200 2.2 0.07 1.2 -- .81

05/24/04 1115 .13 .02 2.9 -- .69

06/10/04 1000 .34 .02 .85 -- .46

07/21/04 1130 <.02 <.02 .75 <0.02 .10

2 5418600 Maquoketa River near Spragueville 03/15/04 1700 <.02 -- .16 -- .12

03/29/04 1500 <.02 -- .50 -- .16

04/20/04 1510 .02 -- .26 -- .04

05/19/04 0800 .58 <.02 .32 -- .44

05/25/04 1015 6.1 .12 1.3 -- 2.2

06/10/04 1300 .05 .03 .74 -- .39

07/21/04 0720 <.02 <.02 .45 <.02 .13

3 05422000 Wapsipinicon River near DeWitt 03/17/04 0830 .03 -- .31 -- .28

04/15/04 0830 <.02 -- .60 -- .16

05/18/04 1200 2.6 .08 .94 -- 1.0

05/25/04 1430 3.1 .09 1.8 -- 2.3

06/16/04 1230 .16 .04 1.7 -- .82

07/20/04 1200 .02 <.02 1.7 .04 .38

4 05474000 Skunk River at Augusta 03/17/04 1430 .03 -- .15 -- .18

04/15/04 1345 <.02 -- .18 -- .08

05/18/04 0730 .59 .05 .37 -- .43

06/16/04 0900 .20 .03 1.6 -- 2.0

07/20/04 0800 <.02 <.02 .52 <.02 .19

5 05490500 Des Moines River at Keosauqua 03/18/04 1230 .05 -- .14 -- .24

04/22/04 0910 .02 -- .30 -- .26

05/17/04 1400 .42 .02 .27 -- .22

06/14/04 1400 .64 .04 .87 -- 1.3

07/19/04 1600 .11 .02 .87 .10 .56

6 06485500 Big Sioux River at Akron 03/09/04 1200 .33 -- .80 -- 1.5
Table 8. Concentrations of acetamide herbicides and their degradation products analyzed by the U.S. Geological Survey Organic 

Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[ESA, ethanesulfonic acid; OXA, oxanilic acid; SAA, sulfynil acetic acid; <, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological Survey 

site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-

hour)

Concentrations, in micrograms per liter

Acetochlor

Acetochlor

deschloro

Acetochlor

ESA

Acetochlor

hydroxy

Acetochlor

OXA

6 06485500 Big Sioux River at Akron 04/13/04 0930 <0.02 -- 0.11 -- 0.15

05/12/04 1030 .04 <.02 .07 -- .08

05/26/04 1300 .64 .02 .72 -- .87

06/02/04 1215 1.3 .05 .83 -- 1.3

07/14/04 1030 <.02 <.02 .34 0.04 .30

7 06607500 Little Sioux River near Turin 03/10/04 0830 .03 -- .25 -- .56

04/13/04 1400 <.02 -- .11 -- .09

05/11/04 1020 .43 <.02 .15 -- .19

05/24/04 1100 1.4 .03 .33 -- .54

06/08/04 0850 .08 .02 .31 -- .26

06/17/04 1230 .08 <.02 .14 -- .20

07/13/04 1000 <.02 <.02 .32 <.02 .22

8 06609500 Boyer River at Logan 04/14/04 0730 <.02 -- .07 -- .06

05/11/04 1300 .09 <.02 .07 -- .05

05/23/04 1015 8.6 .11 .84 -- 1.7

06/08/04 1130 .04 <.02 .14 -- .09

06/17/04 1000 .27 .02 .44 -- .80

07/13/04 1230 <.02 <.02 .15 <.02 .06

9 06810000 Nishnabotna River above Hamburg 03/11/04 1030 <.02 -- .07 -- .09

03/29/04 1230 .02 -- .09 -- .10

04/12/04 1300 <.02 -- .05 -- .03

05/10/04 1230 3.1 .03 .20 -- .32

05/25/04 1045 .75 .02 .57 -- .85

06/07/04 1245 .05 <.02 .13 -- .08

07/12/04 1230 <.02 <.02 .10 <.02 .09

10 06904010 Chariton River near Moulton 03/18/04 0900 <.02 -- .14 -- .47

04/22/04 1320 <.02 -- .20 -- .35

05/17/04 1100 .05 .02 .21 -- .35

06/14/04 1050 .15 .03 1.3 -- 2.1

07/19/04 1230 .05 .02 .42 .09 .69

Supplemental Information 
Table 8. Concentrations of acetamide herbicides and their degradation products analyzed by the U.S. Geological Survey Organic 

Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[ESA, ethanesulfonic acid; OXA, oxanilic acid; SAA, sulfynil acetic acid; <, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

Acetochlor

SAA

Acetochlor/

metolachlor

2nd amide

Acetochlor/

metolachlor

ESA - 2nd 

amide

1 05412500 Turkey River at Garber 03/15/04 1100 0.09 <0.02 0.07

04/20/04 0950 <.02 <.02 .03

05/19/04 1200 .34 .03 .16

05/24/04 1115 .64 .02 .07

06/10/04 1000 .24 <.02 .10

07/21/04 1130 <.02 <.02 .14

2 5418600 Maquoketa River near Spragueville 03/15/04 1700 <.02 -- .08

03/29/04 1500 .03 -- .10

04/20/04 1510 <.02 <.02 .04

05/19/04 0800 .17 <.02 <.02

05/25/04 1015 .89 .10 .13

06/10/04 1300 .14 <.02 .12

07/21/04 0720 <.02 <.02 .12

3 05422000 Wapsipinicon River near DeWitt 03/17/04 0830 .10 -- .11

04/15/04 0830 .02 -- .16

05/18/04 1200 .43 .07 .14

05/25/04 1430 .99 .05 .21

06/16/04 1230 .36 <.02 .24

07/20/04 1200 .15 <.02 .41

4 05474000 Skunk River at Augusta 03/17/04 1430 .08 -- .08

04/15/04 1345 .02 -- .05

05/18/04 0730 .18 <.02 .09

06/16/04 0900 .93 <.02 .16

07/20/04 0800 .05 <.02 .20

5 05490500 Des Moines River at Keosauqua 03/18/04 1230 .11 -- .05

04/22/04 0910 .05 <.02 .07

05/17/04 1400 .07 <.02 .09

06/14/04 1400 .64 <.02 .14

07/19/04 1600 .32 <.02 .35

6 06485500 Big Sioux River at Akron 03/09/04 1200 .56 -- .13
Table 8. Concentrations of acetamide herbicides and their degradation products analyzed by the U.S. Geological Survey Organic 

Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[ESA, ethanesulfonic acid; OXA, oxanilic acid; SAA, sulfynil acetic acid; <, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

Acetochlor

SAA

Acetochlor/

metolachlor

2nd amide

Acetochlor/

metolachlor

ESA - 2nd 

amide

6 06485500 Big Sioux River at Akron 04/13/04 0930 0.04 -- 0.03

05/12/04 1030 <.02 <0.02 .03

05/26/04 1300 .20 <.02 .06

06/02/04 1215 .50 .03 .07

07/14/04 1030 .12 <.02 .09

7 06607500 Little Sioux River near Turin 03/10/04 0830 .19 -- .08

04/13/04 1400 .02 -- .03

05/11/04 1020 .04 <.02 .03

05/24/04 1100 .25 <.02 .03

06/08/04 0850 .10 <.02 .07

06/17/04 1230 .08 <.02 .04

07/13/04 1000 .10 <.02 .09

8 06609500 Boyer River at Logan 04/14/04 0730 <.02 -- .05

05/11/04 1300 <.02 <.02 .02

05/23/04 1015 .70 .07 .07

06/08/04 1130 .05 <.02 .05

06/17/04 1000 .31 <.02 .06

07/13/04 1230 <.02 <.02 .05

9 06810000 Nishnabotna River above Hamburg 03/11/04 1030 <.02 -- .05

03/29/04 1230 .04 -- .05

04/12/04 1300 <.02 -- <.02

05/10/04 1230 .12 .08 .03

05/25/04 1045 .26 <.02 .03

06/07/04 1245 .06 <.02 .05

07/12/04 1230 <.02 <.02 .04

10 06904010 Chariton River near Moulton 03/18/04 0900 .11 -- .04

04/22/04 1320 .07 <.02 .03

05/17/04 1100 .07 <.02 .03

06/14/04 1050 .81 <.02 .12

07/19/04 1230 .23 <.02 .13

Supplemental Information 
Table 8. Concentrations of acetamide herbicides and their degradation products analyzed by the U.S. Geological Survey Organic 

Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[ESA, ethanesulfonic acid; OXA, oxanilic acid; SAA, sulfynil acetic acid; <, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

Alachlor Alachlor

deschloro

Alachlor

ESA

Alachlor

hydroxy

1 5412500 Turkey River at Garber 03/15/04 1100 <0.02 -- 0.25 --

04/20/04 0950 <.02 <0.02 .46 --

05/19/04 1200 <.02 <.02 .44 --

05/24/04 1115 <.02 <.02 .30 --

06/10/04 1000 <.02 <.02 .28 --

07/21/04 1130 <.02 <.02 .36 <0.02

2 5418600 Maquoketa River near Spragueville 03/15/04 1700 <.02 -- .29 --

03/29/04 1500 <.02 -- .29 --

04/20/04 1510 <.02 <.02 .56 --

05/19/04 0800 <.02 <.02 .39 --

05/25/04 1015 <.02 <.02 .13 --

06/10/04 1300 <.02 <.02 .43 --

07/21/04 0720 <.02 <.02 .48 <.02

3 5422000 Wapsipinicon River near DeWitt 03/17/04 0830 <.02 -- .40 --

04/15/04 0830 <.02 -- .69 --

05/18/04 1200 <.02 <.02 .39 --

05/25/04 1430 .09 <.02 .37 --

06/16/04 1230 <.02 <.02 .43 --

07/20/04 1200 <.02 <.02 .51 <.02

4 5474000 Skunk River at Augusta 03/17/04 1430 <.02 -- .12 --

04/15/04 1345 <.02 -- .16 --

05/18/04 0730 <.02 <.02 .11 --

06/16/04 0900 <.02 <.02 .06 --

07/20/04 0800 <.02 <.02 .07 <.02

5 5490500 Des Moines River at Keosauqua 03/18/04 1230 <.02 -- .08 --

04/22/04 0910 <.02 <.02 .07 --

05/17/04 1400 <.02 <.02 .05 --

06/14/04 1400 <.02 <.02 .04 --

07/19/04 1600 <.02 <.02 .04 <.02

6 6485500 Big Sioux River at Akron 03/09/04 1200 <.02 -- .08 --

04/13/04 0930 <.02 -- .08 --

40 Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products in 10 Iowa Rivers, 2004
Table 8. Concentrations of acetamide herbicides and their degradation products analyzed by the U.S. Geological Survey Organic 

Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[ESA, ethanesulfonic acid; OXA, oxanilic acid; SAA, sulfynil acetic acid; <, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

Alachlor Alachlor

deschloro

Alachlor

ESA

Alachlor

hydroxy

6 6485500 Big Sioux River at Akron 05/12/04 1030 <0.02 <0.02 0.05 --

05/26/04 1300 <.02 <.02 .06 --

06/02/04 1215 .03 <.02 .04 --

07/14/04 1030 <.02 <.02 .05 <0.02

7 6607500 Little Sioux River near Turin 03/10/04 0830 <.02 -- .08 --

04/13/04 1400 <.02 -- .09 --

05/11/04 1020 <.02 <.02 .06 --

05/24/04 1100 <.02 <.02 <.02 --

06/08/04 0850 <.02 <.02 .05 --

06/17/04 1230 <.02 <.02 <.02 --

07/13/04 1000 <.02 <.02 .05 <.02

8 6609500 Boyer River at Logan 04/14/04 0730 <.02 -- .07 --

05/11/04 1300 <.02 <.02 .06 --

05/23/04 1015 <.02 <.02 .02 --

06/08/04 1130 <.02 <.02 .03 --

06/17/04 1000 <.02 <.02 <.02 --

07/13/04 1230 <.02 <.02 .02 <.02

9 6810000 Nishnabotna River above Hamburg 03/11/04 1030 <.02 -- .08 --

03/29/04 1230 <.02 -- .02 --

04/12/04 1300 <.02 -- .05 --

05/10/04 1230 .15 <.02 .04 --

05/25/04 1045 <.02 <.02 .04 --

06/07/04 1245 <.02 <.02 .03 --

07/12/04 1230 <.02 <.02 .02 <.02

10 6904010 Chariton River near Moulton 03/18/04 0900 <.02 -- .07 --

04/22/04 1320 <.02 <.02 .07 --

05/17/04 1100 <.02 <.02 .05 --

06/14/04 1050 <.02 <.02 .03 --

07/19/04 1230 <.02 <.02 <.02 <.02

Supplemental Information 41
Table 8. Concentrations of acetamide herbicides and their degradation products analyzed by the U.S. Geological Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[ESA, ethanesulfonic acid; OXA, oxanilic acid; SAA, sulfynil acetic acid; <, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/

day/

year)

Collection time

(24-hour)

Concentrations, in micrograms per liter

Alachlor

OXA

Alachlor

SAA

Alachlor

2nd

amide

Alachlor

ESA - 2nd

amide

Dimethenamid

1 5412500 Turkey River at Garber 03/15/04 1100 0.07 <0.02 <0.02 -- 0.03

04/20/04 0950 .03 <.02 <.02 <0.02 <.02

05/19/04 1200 .04 .06 <.02 <.02 .71

05/24/04 1115 .03 .58 <.02 .33 .62

06/10/04 1000 .02 <.02 <.02 <.02 .42

07/21/04 1130 .02 <.02 <.02 <.02 <.02

2 5418600 Maquoketa River near Spragueville 03/15/04 1700 .05 <.02 -- <.02 <.02

03/29/04 1500 .03 <.02 -- <.02 <.02

04/20/04 1510 .02 <.02 <.02 <.02 <.02

05/19/04 0800 .02 <.02 <.02 <.02 .02

05/25/04 1015 .02 .63 <.02 .15 1.1

06/10/04 1300 .02 <.02 <.02 <.02 .03

07/21/04 0720 .02 <.02 <.02 <.02 <.02

3 5422000 Wapsipinicon River near DeWitt 03/17/04 0830 .10 <.02 -- .03 .03

04/15/04 0830 .06 <.02 <.02 <.02 <.02

05/18/04 1200 .05 .12 <.02 .16 .98

05/25/04 1430 .09 .58 <.02 .12 .35

06/16/04 1230 .05 <.02 <.02 .02 .08

07/20/04 1200 .04 <.02 <.02 <.02 <.02

4 5474000 Skunk River at Augusta 03/17/04 1430 .06 <.02 <.02 .02 <.02

04/15/04 1345 .03 <.02 <.02 <.02 <.02

05/18/04 0730 .02 .02 <.02 .04 .18

06/16/04 0900 .03 <.02 <.02 <.02 .08

07/20/04 0800 .02 <.02 <.02 <.02 <.02

5 5490500 Des Moines River at Keosauqua 03/18/04 1230 .05 <.02 -- .02 .03

04/22/04 0910 .03 <.02 <.02 <.02 <.02

05/17/04 1400 .02 <.02 <.02 <.02 .20

06/14/04 1400 .03 <.02 <.02 <.02 .24

07/19/04 1600 .02 <.02 <.02 <.02 <.02

6 6485500 Big Sioux River at Akron 03/09/04 1200 .07 <.02 -- .05 .04

42 Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products in 10 Iowa Rivers, 2004
Table 8. Concentrations of acetamide herbicides and their degradation products analyzed by the U.S. Geological Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[ESA, ethanesulfonic acid; OXA, oxanilic acid; SAA, sulfynil acetic acid; <, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/

day/

year)

Collection time

(24-hour)

Concentrations, in micrograms per liter

Alachlor

OXA

Alachlor

SAA

Alachlor

2nd

amide

Alachlor

ESA - 2nd

amide

Dimethenamid

6 6485500 Big Sioux River at Akron 04/13/04 0930 0.03 <0.02 <0.02 <0.02 <0.02

05/12/04 1030 .02 <.02 <.02 <.02 <.02

05/26/04 1300 .03 .10 <.02 <.02 .09

06/02/04 1215 .03 <.02 <.02 <.02 .15

07/14/04 1030 <.02 <.02 <.02 <.02 <.02

7 6607500 Little Sioux River near Turin 03/10/04 0830 .05 <.02 -- <.02 <.02

04/13/04 1400 .02 <.02 <.02 <.02 <.02

05/11/04 1020 <.02 .02 <.02 <.02 .06

05/24/04 1100 <.02 .10 <.02 <.02 .04

06/08/04 0850 .02 <.02 <.02 <.02 <.02

06/17/04 1230 <.02 <.02 <.02 <.02 .02

07/13/04 1000 <.02 <.02 <.02 <.02 <.02

8 6609500 Boyer River at Logan 04/14/04 0730 .06 <.02 <.02 <.02 <.02

05/11/04 1300 .05 <.02 <.02 <.02 <.02

05/23/04 1015 .02 .26 <.02 <.02 .23

06/08/04 1130 .03 <.02 <.02 <.02 <.02

06/17/04 1000 <.02 <.02 <.02 <.02 <.02

07/13/04 1230 .02 <.02 <.02 <.02 <.02

9 6810000 Nishnabotna River above Hamburg 03/11/04 1030 .05 <.02 -- <.02 .02

03/29/04 1230 .02 <.02 -- <.02 <.02

04/12/04 1300 .03 <.02 <.02 <.02 <.02

05/10/04 1230 .02 .06 <.02 <.02 .52

05/25/04 1045 .03 .15 <.02 <.02 .38

06/07/04 1245 .02 <.02 <.02 <.02 .02

07/12/04 1230 <.02 <.02 <.02 <.02 <.02

10 6904010 Chariton River near Moulton 03/18/04 0900 .04 <.02 -- .96 .03

04/22/04 1320 .02 <.02 <.02 <.02 <.02

05/17/04 1100 .02 <.02 <.02 <.02 <.02

06/14/04 1050 .02 <.02 <.02 <.02 .03

07/19/04 1230 .02 <.02 <.02 <.02 <.02

Supplemental Information 4
Table 8. Concentrations of acetamide herbicides and their degradation products analyzed by the U.S. Geological Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[ESA, ethanesulfonic acid; OXA, oxanilic acid; SAA, sulfynil acetic acid; <, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

Dimethenamid

deschloro

Dimethenamid

ESA

Dimethenamid

hydroxy

Dimethenamid

OXA

1 5412500 Turkey River at Garber 3/15/2004 1100 -- 0.05 -- <0.02

4/20/2004 950 -- <.02 -- <.02

5/19/2004 1200 <0.02 .10 -- .08

5/24/2004 1115 <.02 .17 -- .34

6/10/2004 1000 <.02 .13 -- .07

7/21/2004 1130 <.02 <.02 <0.02 <.02

2 5418600 Maquoketa River near Spragueville 3/15/2004 1700 -- .06 -- .02

3/29/2004 1500 -- .07 -- <.02

4/20/2004 1510 -- .02 -- <.02

5/19/2004 800 <.02 .02 -- .02

5/25/2004 1015 <.02 .18 -- .15

6/10/2004 1300 <.02 .08 -- .03

7/21/2004 720 <.02 .10 <.02 .02

3 5422000 Wapsipinicon River near DeWitt 3/17/2004 830 -- .10 -- .03

4/15/2004 830 -- .05 -- <.02

5/18/2004 1200 <.02 .12 -- .16

5/25/2004 1430 <.02 .18 -- .12

06/16/04 1230 <.02 0.21 -- 0.07

07/20/04 1200 <.02 .60 <.02 .06

4 5474000 Skunk River at Augusta 03/17/04 1430 -- .06 -- .02

04/15/04 1345 -- .03 -- <.02

05/18/04 0730 <.02 .06 -- .05

06/16/04 0900 <.02 .17 -- .15

07/20/04 0800 <.02 .12 <.02 .03

5 5490500 Des Moines River at Keosauqua 03/18/04 1230 -- .06 -- .02

04/22/04 0910 -- .03 -- <.02

05/17/04 1400 <.02 .04 -- <.02

06/14/04 1400 <.02 .14 -- .10

07/19/04 1600 <.02 .14 <.02 .04

44 Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products in 10 Iowa Rivers, 2004
Table 8. Concentrations of acetamide herbicides and their degradation products analyzed by the U.S. Geological Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[ESA, ethanesulfonic acid; OXA, oxanilic acid; SAA, sulfynil acetic acid; <, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

Dimethenamid

deschloro

Dimethenamid

ESA

Dimethenamid

hydroxy

Dimethenamid

OXA

6 6485500 Big Sioux River at Akron 03/09/04 1200 -- 0.12 -- 0.07

04/13/04 0930 -- .02 -- <.02

05/12/04 1030 <0.02 <.02 -- <.02

05/26/04 1300 <.02 .02 -- .04

06/02/04 1215 <.02 .05 -- .04

07/14/04 1030 <.02 .03 <0.02 <.02

7 6607500 Little Sioux River near Turin 03/10/04 0830 -- <.02 -- <.02

04/13/04 1400 -- <.02 -- <.02

05/11/04 1020 <.02 <.02 -- <.02

05/24/04 1100 <.02 <.02 -- <.02

06/08/04 0850 <.02 <.02 -- <.02

06/17/04 1230 <.02 .02 -- <.02

07/13/04 1000 <.02 <.02 <.02 <.02

8 6609500 Boyer River at Logan 04/14/04 0730 -- <.02 -- <.02

05/11/04 1300 <.02 <.02 -- <.02

05/23/04 1015 <.02 .03 -- .05

06/08/04 1130 <.02 <.02 -- <.02

06/17/04 1000 <.02 <.02 -- <.02

07/13/04 1230 <.02 <.02 <.02 <.02

9 6810000 Nishnabotna River above Hamburg 03/11/04 1030 -- <.02 -- <.02

03/29/04 1230 -- .02 -- <.02

04/12/04 1300 -- <.02 -- <.02

05/10/04 1230 <.02 .02 -- <.02

05/25/04 1045 .03 .06 -- .14

06/07/04 1245 <.02 .02 <.02 <.02

07/12/04 1230 <.02 .02 <.02 <.02

10 6904010 Chariton River near Moulton 03/18/04 0900 -- .06 -- .05

04/22/04 1320 -- <.02 -- <.02

05/17/04 1100 <.02 .03 -- .02

06/14/04 1050 <.02 .09 -- .08

07/19/04 1230 <.02 .06 <.02 .04

Supplemental Information 4
Table 8. Concentrations of acetamide herbicides and their degradation products analyzed by the U.S. Geological Survey Organic 

Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[ESA, ethanesulfonic acid; OXA, oxanilic acid; SAA, sulfynil acetic acid; <, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

Flufenacet

Flufenacet

ESA

Flufenacet

OXA

Metolachlor

Metolachlor

deschloro

1 5412500 Turkey River at Garber 03/15/04 1100 <0.02 <0.02 <0.02 0.07 --

04/20/04 0950 <.02 <.02 <.02 <.02 --

05/19/04 1200 .06 <.02 <.02 .59 <0.02

05/24/04 1115 <.02 .03 .02 .07 <.02

06/10/04 1000 <.02 <.02 <.02 .40 <.02

07/21/04 1130 <.02 <.02 <.02 .02 <.02

2 5418600 Maquoketa River near Spragueville 03/15/04 1700 <.02 <.02 <.02 .03 --

03/29/04 1500 <.02 <.02 <.02 .03 --

04/20/04 1510 <.02 <.02 <.02 .02 --

05/19/04 0800 .13 <.02 <.02 .22 <.02

05/25/04 1015 <.02 <.02 <.02 3.3 <.02

06/10/04 1300 <.02 <.02 <.02 .10 <.02

07/21/04 0720 <.02 <.02 <.02 .03 <.02

3 5422000 Wapsipinicon River near DeWitt 03/17/04 0830 <.02 <.02 <.02 .09 --

04/15/04 0830 <.02 <.02 <.02 .03 --

05/18/04 1200 .04 <.02 <.02 1.5 <.02

05/25/04 1430 <.02 .02 <.02 2.3 <.02

06/16/04 1230 <.02 <.02 <.02 .34 <.02

07/20/04 1200 <.02 <.02 <.02 .08 <.02

4 5474000 Skunk River at Augusta 03/17/04 1430 <.02 <.02 <.02 .17 --

04/15/04 1345 <.02 <.02 <.02 .06 --

05/18/04 0730 <.02 <.02 <.02 1.2 <.02

06/16/04 0900 .19 .16 .12 .84 <.02

07/20/04 0800 <.02 <.02 <.02 .15 <.02

5 5490500 Des Moines River at Keosauqua 03/18/04 1230 .03 .02 <.02 1.1 --

04/22/04 0910 <.02 <.02 <.02 .25 --

05/17/04 1400 <.02 <.02 <.02 .66 <.02

06/14/04 1400 .05 <.02 <.02 .64 <.02

07/19/04 1600 <.02 <.02 <.02 .23 <.02

4 Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products in 10 Iowa Rivers, 2004
Table 8. Concentrations of acetamide herbicides and their degradation products analyzed by the U.S. Geological Survey Organic 

Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[ESA, ethanesulfonic acid; OXA, oxanilic acid; SAA, sulfynil acetic acid; <, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

Flufenacet

Flufenacet

ESA

Flufenacet

OXA

Metolachlor

Metolachlor

deschloro

6 6485500 Big Sioux River at Akron 03/09/04 1200 <0.02 <0.02 <0.02 1.5 --

04/13/04 0930 <.02 <.02 <.02 .08 --

05/12/04 1030 <.02 <.02 <.02 .06 <0.02

05/26/04 1300 <.02 <.02 <.02 .31 <.02

06/02/04 1215 .03 <.02 <.02 .58 <.02

07/14/04 1030 <.02 <.02 <.02 .03 <.02

7 6607500 Little Sioux River near Turin 03/10/04 0830 <.02 .02 <.02 .33 --

04/13/04 1400 <.02 <.02 <.02 .05 --

05/11/04 1020 .16 <.02 <.02 .40 <.02

05/24/04 1100 .20 <.02 <.02 1.1 <.02

06/08/04 0850 <.02 <.02 <.02 .09 <.02

06/17/04 1230 .12 <.02 <.02 .45 <.02

07/13/04 1000 <.02 <.02 <.02 .04 <.02

8 6609500 Boyer River at Logan 04/14/04 0730 <.02 <.02 <.02 .02 --

05/11/04 1300 <.02 <.02 <.02 .32 <.02

05/23/04 1015 .98 .04 .04 3.8 <.02

06/08/04 1130 <.02 <.02 <.02 .13 <.02

06/17/04 1000 .26 .03 .02 .46 <.02

07/13/04 1230 <.02 <.02 <.02 .04 <.02

9 6810000 Nishnabotna River above Hamburg 03/11/04 1030 <.02 <.02 <.02 .03 --

03/29/04 1230 <.02 <.02 <.02 .05 --

04/12/04 1300 <.02 <.02 <.02 .02 --

05/10/04 1230 .68 <.02 <.02 .88 <.02

05/25/04 1045 .20 .02 .02 2.4 <.02

06/07/04 1245 .02 .02 <.02 .11 <.02

07/12/04 1230 <.02 <.02 <.02 .08 <.02

10 6904010 Chariton River near Moulton 03/18/04 0900 <.02 <.02 <.02 .10 --

04/22/04 1320 <.02 <.02 <.02 .04 --

05/17/04 1100 <.02 <.02 <.02 .07 .06

06/14/04 1050 <.02 <.02 <.02 .17 .04

07/19/04 1230 <.02 <.02 <.02 .32 .08

Supplemental Information 4
Table 8. Concentrations of acetamide herbicides and their degradation products analyzed by the U.S. Geological Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[ESA, ethanesulfonic acid; OXA, oxanilic acid; SAA, sulfynil acetic acid; <, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/

day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

Metolachlor

ESA

Metolachlor

hydroxy

Metolachlor

OXA

Propachlor

Propachlor

ESA

Propachlor

OXA

1 5412500 Turkey River at Garber 03/15/04 1100 0.30 -- 0.12 <0.02 <0.05 <0.02

04/20/04 0950 .88 -- .08 <.02 <.05 <.02

05/19/04 1200 1.3 -- .22 <.02 <.05 <.02

05/24/04 1115 1.6 -- .49 <.02 <.05 <.02

06/10/04 1000 .69 -- .16 <.02 <.05 <.02

07/21/04 1130 .75 <0.02 .07 <.02 <.05 <.02

2 5418600 Maquoketa River near Spragueville 03/15/04 1700 1.2 -- .21 <.02 <.05 <.02

03/29/04 1500 1.6 -- .32 <.02 <.05 <.02

04/20/04 1510 1.9 -- .17 <.02 <.05 <.02

05/19/04 0800 1.5 -- .16 <.02 <.05 <.02

05/25/04 1015 1.0 -- .49 <.02 <.05 <.02

06/10/04 1300 1.7 -- .25 <.02 <.05 <.02

07/21/04 0720 1.6 <.02 .15 <.02 <.05 <.02

3 5422000 Wapsipinicon River near DeWitt 03/17/04 0830 1.3 -- .30 <.02 <.05 <.02

04/15/04 0830 1.7 -- .26 <.02 <.05 <.02

05/18/04 1200 1.5 -- .40 <.02 <.05 <.02

05/25/04 1430 2.0 -- .87 <.02 <.05 <.02

06/16/04 1230 2.2 -- .51 <.02 <.05 <.02

07/20/04 1200 2.9 .03 .33 <.02 <.05 <.02

4 5474000 Skunk River at Augusta 03/17/04 1430 .84 -- .31 <.02 <.05 <.02

04/15/04 1345 .97 -- .23 <.02 <.05 <.02

05/18/04 0730 1.1 -- .29 <.02 <.05 <.02

06/16/04 0900 1.6 -- 1.1 <.02 <.05 <.02

07/20/04 0800 2.0 .05 .36 <.02 <.05 <.02

5 5490500 Des Moines River at Keosauqua 03/18/04 1230 .42 -- .36 <.02 <.05 <.02

04/22/04 0910 1.3 -- .38 <.02 <.05 <.02

05/17/04 1400 .86 -- .24 <.02 <.05 <.02

06/14/04 1400 1.1 -- .45 <.02 <.05 <.02

07/19/04 1600 1.5 .07 .32 <.02 <.05 <.02

6 6485500 Big Sioux River at Akron 03/9/04 1200 1.1 -- .99 <.02 <.05 <.02

4 Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products in 10 Iowa Rivers, 2004
Table 8. Concentrations of acetamide herbicides and their degradation products analyzed by the U.S. Geological Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[ESA, ethanesulfonic acid; OXA, oxanilic acid; SAA, sulfynil acetic acid; <, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/

day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

Metolachlor

ESA

Metolachlor

hydroxy

Metolachlor

OXA

Propachlor

Propachlor

ESA

Propachlor

OXA

6 6485500 Big Sioux River at Akron 4/13/04 930 0.57 -- 0.14 <0.02 <0.05 <0.02

5/12/04 1030 .40 -- .10 <.02 <.05 <.02

5/26/04 1300 1.2 -- .31 <.02 <.05 <.02

6/2/04 1215 .50 -- .23 <.02 <.05 <.02

7/14/04 1030 .63 <0.02 .13 <.02 <.05 <.02

7 6607500 Little Sioux River near Turin 03/10/04 0830 .39 -- .39 <.02 <.05 <.02

04/13/04 1400 .46 -- .15 <.02 <.05 <.02

05/11/04 1020 .41 -- .14 <.02 <.05 <.02

05/24/04 1100 .37 -- .22 <.02 <.05 <.02

06/08/04 0850 .61 -- .14 <.02 <.05 <.02

06/17/04 1230 .27 -- .20 <.02 <.05 <.02

07/13/04 1000 .67 <.02 .15 <.02 <.05 <.02

8 6609500 Boyer River at Logan 04/14/04 0730 .36 -- .19 <.02 <.05 <.02

05/11/04 1300 .30 -- .16 <.02 <.05 <.02

05/23/04 1015 .51 -- .45 <.02 <.05 <.02

06/08/04 1130 .48 -- .15 <.02 <.05 <.02

06/17/04 1000 .38 -- .23 <.02 <.05 <.02

07/13/04 1230 .61 <.02 .14 <.02 <.05 <.02

9 6810000 Nishnabotna River above Hamburg 03/11/04 1030 .16 -- .13 <.02 <.05 <.02

03/29/04 1230 .33 -- .15 <.02 <.05 <.02

04/12/04 1300 .31 -- .09 <.02 <.05 <.02

05/10/04 1230 .22 -- .09 <.02 <.05 <.02

05/25/04 1045 .72 -- .63 <.02 <.05 <.02

06/07/04 1245 .28 -- .09 <.02 <.05 <.02

07/12/04 1230 .24 <.02 .12 <.02 <.05 <.02

10 6904010 Chariton River near Moulton 03/18/04 0900 .19 -- .41 <.02 <.05 <.02

04/22/04 1320 .43 -- .32 <.02 <.05 <.02

05/17/04 1100 .23 -- .29 <.02 <.05 <.02

06/14/04 1050 .46 -- .51 <.02 <.05 <.02

07/19/04 1230 .55 .23 .51 <.02 <.05 <.02

Supplemental Information 4
Table 9. Concentrations of triazine and phenylurea herbicides and their degradation products analyzed by the U.S. Geological Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004. 

[<, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Concentration, in micrograms per liter

AtrazineDeethylatrazine

DeethylhydroxyatrazineDeisopropylatrazine

1 05412500 Turkey River at Garber 03/15/04 1100 0.04 0.07 <0.025 <0.025

04/20/04 0950 .06 .09 <.025 .03

05/19/04 1200 2.6 .32 <.025 .14

05/24/04 1115 3.4 .65 <.025 .34

06/10/04 1000 1.2 .28 <.025 .14

07/21/04 1130 .21 .18 <.025 .08

09/14/04 1300 .06 .11 <.025 .03

2 05418600 Maquoketa River near Spragueville 03/15/04 1700 <.025 .08 <.025 <.025

03/29/04 1500 .03 .09 <.025 <.025

04/20/04 1510 .06 .10 <.025 .03

05/19/04 0800 .88 .20 <.025 .07

05/25/04 1015 4.5 .84 <.025 .50

06/10/04 1300 .33 .16 <.025 .05

07/21/04 0720 .20 .19 <.025 .08

09/14/04 1000 .04 .12 <.025 .03

3 05422000 Wapsipinicon River near DeWitt 03/17/04 0830 <.025 .06 <.025 <.025

04/15/04 0830 .03 .08 <.025 .03

05/18/04 1200 5.8 .41 <.025 .17

05/25/04 1430 4.6 .77 <.025 .45

06/16/04 1230 1.6 .40 <.025 .15

07/20/04 1200 .43 .50 <.025 .21

09/14/04 0730 .07 .08 <.025 <.025

4 05474000 Skunk River at Augusta 03/17/04 1430 .03 .04 <.025 <.025

04/15/04 1345 .05 .05 <.025 .03

05/18/04 0730 1.3 .18 <.025 .08

06/16/04 0900 1.2 .70 <.025 .38

07/20/04 0800 .30 .18 <.025 .09

09/13/04 1530 .07 .06 <.025 <.025
Table . Concentrations of triazine and phenylurea herbicides and their degradation products analyzed by the U.S. Geological 

Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—

Continued 

[<, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Concentration, in micrograms per liter

AtrazineDeethylatrazine

DeethylhydroxyatrazineDeisopropylatrazine

5 05490500 Des Moines River at Keosauqua 03/18/04 1230 0.05 0.04 <0.025 <0.025

04/22/04 0910 .07 .04 <.025 .03

05/17/04 1400 1.3 .10 <.025 .05

06/14/04 1400 1.2 .31 <.025 .14

07/19/04 1600 1.2 .34 <.025 .19

09/13/04 1330 .18 .09 <.025 .04

6 06485500 Big Sioux River at Akron 03/09/04 1200 .06 .06 <.025 <.025

04/13/04 0930 .03 <.025 <.025 <.025

Supplemental Information 1

05/12/04 1030 .06 .05 <.025 .05

05/26/04 1300 .38 .07 <.025 .06

06/02/04 1215 1.3 .27 <.025 .20

07/14/04 1030 .52 .14 <.025 .11

7 06607500 Little Sioux River near Turin 03/10/04 0830 .04 .04 <.025 <.025

04/13/04 1400 .03 .03 <.025 <.025

05/11/04 1020 1.4 .15 <.025 .08

05/24/04 1100 3.3 .47 <.025 .30

06/08/04 0850 .23 .07 <.025 .04

06/17/04 1230 8.2 .46 .09 .29

07/13/04 1000 .51 .14 <.025 .08

8 06609500 Boyer River at Logan 03/12/04 0930 .03 <.025 <.025 <.025

04/14/04 0730 .03 .03 <.025 <.025

05/11/04 1300 .32 .09 <.025 .06

05/23/04 1015 18 1.7 <.025 .94

06/08/04 1130 .33 .08 <.025 .04

06/17/04 1000 13 .88 .22 .65

07/13/04 1230 .25 .12 <.025 .06

9 06810000 Nishnabotna River above Hamburg 03/11/04 1030 <.025 .03 <.025 <.025

03/29/04 1230 .08 .05 <.025 <.025
Table 9. Concentrations of triazine and phenylurea herbicides and their degradation products analyzed by the U.S. Geological 

Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—

Continued 

[<, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Concentration, in micrograms per liter

AtrazineDeethylatrazine

DeethylhydroxyatrazineDeisopropylatrazine

9 06810000 Nishnabotna River above Hamburg 04/12/04 1300 0.04 0.04 <0.025 <0.025

05/10/04 1230 21 .96 <.025 .37

05/25/04 1045 5.1 1.2 <.025 .91

06/07/04 1245 .50 .14 <.025 .06

07/12/04 1230 .58 .35 <.025 .16

10 06904010 Chariton River near Moulton 03/18/04 0900 .36 .29 <.025 .09

04/22/04 1320 .23 .18 <.025 .07

05/17/04 1100 .29 .21 <.025 .08

06/14/04 1050 .85 .53 <.025 .20

07/19/04 1230 .86 .67 <.025 .38

09/13/04 1030 .56 .38 <.025 .15
Table 9. Concentrations of triazine and phenylurea herbicides and their degradation products analyzed by the U.S. Geological 

Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 

2004.—Continued

[<, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Concentration, in micrograms per liter

Deisopropylhydroxyatrazine

DidealkylatrazineHydroxyatrazine

1 05412500 Turkey River at Garber 03/15/04 1100 <0.025 0.10 0.04

04/20/04 0950 <.025 .12 .04

05/19/04 1200 <.025 .34 .09

05/24/04 1115 <.025 .43 .28

06/10/04 1000 <.025 .29 .22

07/21/04 1130 .05 <.025 <.025

09/14/04 1300 <.025 .17 .09

2 05418600 Maquoketa River near Spragueville 03/15/04 1700 <.025 .10 <.025

03/29/04 1500 <.025 .13 .05

04/20/04 1510 <.025 .13 .04

05/19/04 0800 <.025 .18 .06

05/25/04 1015 <.025 .45 .46

06/10/04 1300 <.025 .23 .07

07/21/04 0720 <.025 .28 .09

09/14/04 1000 <.025 .19 .09

3 05422000 Wapsipinicon River near DeWitt 03/17/04 0830 <.025 .08 .05

04/15/04 0830 <.025 .12 .05

05/18/04 1200 <.025 .18 .16

05/25/04 1430 <.025 .58 .37

06/16/04 1230 <.025 .25 .15

07/20/04 1200 <.025 <.025 <.025

09/14/04 0730 <.025 .10 .13

4 05474000 Skunk River at Augusta 03/17/04 1430 <.025 .07 .05

04/15/04 1345 <.025 .11 .06

05/18/04 0730 <.025 .15 .10

06/16/04 0900 <.025 .58 .30

07/20/04 0800 <.025 .36 <.025

09/13/04 1530 <.025 .12 .19

Supplemental Information 
Table 9. Concentrations of triazine and phenylurea herbicides and their degradation products analyzed by the U.S. Geological 

Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 

2004.—Continued

[<, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Concentration, in micrograms per liter

Deisopropylhydroxyatrazine

DidealkylatrazineHydroxyatrazine

5 05490500 Des Moines River at Keosauqua 03/18/04 1230 <0.025 0.05 0.10

04/22/04 0910 <.025 .07 .06

05/17/04 1400 <.025 .10 .10

06/14/04 1400 <.025 .23 .25

07/19/04 1600 <.025 .32 <.025

09/13/04 1330 <.025 .11 .24

6 06485500 Big Sioux River at Akron 03/09/04 1200 <.025 <.025 .26

04/13/04 0930 <.025 .09 .05

05/12/04 1030 <.025 .14 .06

05/26/04 1300 <.025 .32 .16

06/02/04 1215 <.025 .29 .40

07/14/04 1030 <.025 .26 .15

7 06607500 Little Sioux River near Turin 03/10/04 0830 <.025 .06 .18

04/13/04 1400 <.025 .11 .05

05/11/04 1020 <.025 .14 .63

05/24/04 1100 <.025 .37 .96

06/08/04 0850 <.025 .19 .12

06/17/04 1230 .06 .25 .86

07/13/04 1000 <.025 .27 <.025

8 06609500 Boyer River at Logan 03/12/04 0930 <.025 .08 .07

04/14/04 0730 <.025 .12 .07

05/11/04 1300 <.025 .15 .09

05/23/04 1015 <.025 .73 1.0

06/08/04 1130 <.025 .24 .15

06/17/04 1000 .08 .55 1.5

07/13/04 1230 <.025 <.025 .14

9 06810000 Nishnabotna River above Hamburg 03/11/04 1030 <.025 .08 .08

03/29/04 1230 <.025 .12 .15
Table 9. Concentrations of triazine and phenylurea herbicides and their degradation products analyzed by the U.S. Geological 

Survey Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 

2004.—Continued

[<, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Concentration, in micrograms per liter

Deisopropylhydroxyatrazine

DidealkylatrazineHydroxyatrazine

9 06810000 Nishnabotna River above Hamburg 04/12/04 1300 <0.025 0.15 0.07

05/10/04 1230 <.025 .22 .69

05/25/04 1045 <.025 .84 .84

06/07/04 1245 <.025 .31 .16

07/12/04 1230 <.025 .50 .31

10 06904010 Chariton River near Moulton 03/18/04 0900 <.025 .08 .44

04/22/04 1320 <.025 .07 .31

05/17/04 1100 <.025 .07 .33

06/14/04 1050 <.025 .28 .46

07/19/04 1230 <.025 <.025 <.025

09/13/04 1030 <.025 .16 .57

Supplemental Information 
Table 9. Concentrations of triazine and phenylurea herbicides and their degradation products analyzed by the U.S. Geological Survey 

Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[<, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/

day/

year)

Collection

time

(24-hour)

Concentration, in micrograms per liter

BromacilCyanazine

Cyanazine

amide 

Cyanazine

acid

Deethylcyanazine

Deethylcyanazine

acid

1 05412500 Turkey River at Garber 03/15/04 1100 <0.025 <0.025 <0.025 <0.025 <0.020 <0.025

04/20/04 0950 <.025 <.025 <.025 <.025 <.020 <.025

05/19/04 1200 <.025 <.025 <.025 <.025 <.020 <.025

05/24/04 1115 <.025 <.025 <.025 <.025 <.020 <.025

06/10/04 1000 <.025 <.025 <.025 <.025 <.020 <.025

07/21/04 1130 <.025 <.025 <.025 <.025 <.020 <.025

09/14/04 1300 <.025 <.025 <.025 <.025 <.020 <.025

2 05418600 Maquoketa River near 

Spragueville

03/15/04 1700 <.025 <.025 <.025 <.025 <.020 <.025

03/29/04 1500 <.025 <.025 <.025 <.025 <.020 <.025

04/20/04 1510 <.025 <.025 <.025 <.025 <.020 .08

05/19/04 0800 <.025 <.025 <.025 <.025 <.020 <.025

05/25/04 1015 <.025 <.025 <.025 <.025 <.020 <.025

06/10/04 1300 <.025 <.025 <.025 <.025 <.020 <.025

07/21/04 0720 <.025 <.025 <.025 <.025 <.020 <.025

09/14/04 1000 <.025 <.025 <.025 <.025 <.020 .06

3 05422000 Wapsipinicon River near 

DeWitt

03/17/04 0830 <.025 <.025 <.025 <.025 <.020 <.025

04/15/04 0830 <.025 <.025 <.025 <.025 <.020 .07

05/18/04 1200 <.025 <.025 <.025 <.025 <.020 <.025

05/25/04 1430 <.025 <.025 <.025 <.025 <.020 <.025

06/16/04 1230 <.025 <.025 <.025 <.025 <.020 <.025

07/20/04 1200 <.025 <.025 <.025 <.025 <.020 <.025

09/14/04 0730 <.025 <.025 <.025 <.025 <.020 <.025

4 05474000 Skunk River at Augusta 03/17/04 1430 <.025 <.025 <.025 <.025 <.020 <.025

04/15/04 1345 <.025 <.025 <.025 <.025 <.020 .08

05/18/04 0730 <.025 <.025 <.025 <.025 <.020 <.025

06/16/04 0900 <.025 <.025 <.025 <.025 <.020 <.025

07/20/04 0800 <.025 <.025 <.025 <.025 <.020 <.025

09/13/04 1530 <.025 <.025 <.025 <.025 <.020 <.025
Table 9. Concentrations of triazine and phenylurea herbicides and their degradation products analyzed by the U.S. Geological Survey 

Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[<, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/

day/

year)

Collection

time

(24-hour)

Concentration, in micrograms per liter

BromacilCyanazine

Cyanazine

amide 

Cyanazine

acid

Deethylcyanazine

Deethylcyanazine

acid

5 05490500 Des Moines River at 

Keosauqua

03/18/04 1230 <0.025 <0.025 <0.025 <0.025 <0.020 <0.025

04/22/04 0910 <.025 <.025 <.025 <.025 <.020 <.025

05/17/04 1400 <.025 <.025 <.025 <.025 <.020 <.025

06/14/04 1400 <.025 <.025 <.025 <.025 <.020 <.025

07/19/04 1600 <.025 <.025 <.025 <.025 <.020 <.025

09/13/04 1330 <.025 <.025 <.025 <.025 <.020 <.025

6 06485500 Big Sioux River at Akron 03/09/04 1200 <.025 <.025 <.025 <.025 <.020 <.025

04/13/04 0930 <.025 <.025 <.025 <.025 <.020 .38

05/12/04 1030 <.025 <.025 <.025 <.025 <.020 .41

05/26/04 1300 <.025 <.025 <.025 <.025 <.020 .25

06/02/04 1215 <.025 <.025 <.025 <.025 <.020 <.025

07/14/04 1030 <.025 <.025 <.025 <.025 <.020 <.025

7 06607500 Little Sioux River near 

Turin

03/10/04 0830 <.025 <.025 <.025 <.025 <.020 .21

04/13/04 1400 <.025 <.025 <.025 <.025 <.020 .58

05/11/04 1020 <.025 <.025 <.025 <.025 <.020 .41

05/24/04 1100 <.025 <.025 <.025 <.025 <.020 .26

06/08/04 0850 <.025 <.025 <.025 <.025 <.020 .19

06/17/04 1230 <.025 <.025 <.025 <.025 <.020 .06

07/13/04 1000 <.025 <.025 <.025 <.025 <.020 <.025

8 06609500 Boyer River at Logan 03/12/04 0930 <.025 <.025 <.025 <.025 <.020 .35

04/14/04 0730 <.025 <.025 <.025 <.025 <.020 .71

05/11/04 1300 <.025 <.025 <.025 <.025 <.020 .80

05/23/04 1015 <.025 <.025 <.025 <.025 <.020 1.0

06/08/04 1130 <.025 <.025 <.025 <.025 <.020 .47

06/17/04 1000 <.025 <.025 <.025 <.025 <.020 <.025

07/13/04 1230 <.025 <.025 <.025 <.025 <.020 .23

9 06810000 Nishnabotna River above 

Hamburg

03/11/04 1030 <.025 <.025 <.025 <.025 <.020 .20

03/29/04 1230 <.025 <.025 <.025 <.025 <.020 .26

04/12/04 1300 <.025 <.025 <.025 <.025 <.020 .55

Supplemental Information 
Table 9. Concentrations of triazine and phenylurea herbicides and their degradation products analyzed by the U.S. Geological Survey 

Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[<, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/

day/

year)

Collection

time

(24-hour)

Concentration, in micrograms per liter

BromacilCyanazine

Cyanazine

amide 

Cyanazine

acid

Deethylcyanazine

Deethylcyanazine

acid

9 06810000 Nishnabotna River above 

Hamburg

05/10/04 1230 <0.025 <0.025 <0.025 <0.025 <0.020 0.27

05/25/04 1045 <.025 .61 <.025 <.025 <.020 .31

06/07/04 1245 <.025 <.025 <.025 <.025 <.020 .33

07/12/04 1230 <.025 <.025 <.025 <.025 <.020 .43

10 06904010 Chariton River near 

Moulton

03/18/04 0900 <.025 <.025 <.025 <.025 <.020 <.025

04/22/04 1320 <.025 <.025 <.025 <.025 <.020 <.025

05/17/04 1100 <.025 <.025 <.025 <.025 <.020 <.025

06/14/04 1050 <.025 <.025 <.025 <.025 <.020 <.025

07/19/04 1230 <.025 <.025 <.025 <.025 <.020 <.025

09/13/04 1030 <.025 <.025 <.025 <.025 <.020 <.025
Table 9. Concentrations of triazine and phenylurea herbicides and their degradation products analyzed by the U.S. Geological Survey 

Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[<, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Concentration, in micrograms per liter

Deethylcyanazine

amide

PrometonPropazineSimazine

Hydroxysimazine

1 05412500 Turkey River at Garber 03/15/04 1100 <0.025 -- <0.025 <0.025 <0.025

04/20/04 0950 <.025 -- <.025 <.025 <.025

05/19/04 1200 <.025 <0.025 <.025 <.025 <.025

05/24/04 1115 <.025 <.025 <.025 <.025 <.025

06/10/04 1000 <.025 <.025 <.025 .03 <.025

07/21/04 1130 <.025 <.025 <.025 <.025 <.025

09/14/04 1300 <.025 <.025 <.025 <.025 <.025

2 05418600 Maquoketa River near 

Spragueville

03/15/04 1700 <.025 -- <.025 <.025 <.025

03/29/04 1500 <.025 -- <.025 <.025 <.025

04/20/04 1510 <.025 -- <.025 <.025 <.025

05/19/04 0800 <.025 -- <.025 .04 <.025

05/25/04 1015 <.025 <.025 .04 <.025 <.025

06/10/04 1300 <.025 <.025 <.025 <.025 <.025

07/21/04 0720 <.025 <.025 <.025 <.025 <.025

09/14/04 1000 <.025 <.025 <.025 <.025 <.025

3 05422000 Wapsipinicon River near DeWitt 03/17/04 0830 <.025 -- <.025 <.025 <.025

04/15/04 0830 <.025 -- <.025 <.025 <.025

05/18/04 1200 <.025 <.025 .05 .05 <.025

05/25/04 1430 <.025 <.025 .04 <.025 <.025

06/16/04 1230 <.025 <.025 <.025 <.025 <.025

07/20/04 1200 <.025 <.025 <.025 <.025 <.025

09/14/04 0730 <.025 <.025 <.025 <.025 <.025

4 05474000 Skunk River at Augusta 03/17/04 1430 <.025 -- <.025 <.025 <.025

04/15/04 1345 <.025 -- <.025 <.025 <.025

05/18/04 0730 <.025 -- <.025 <.025 <.025

06/16/04 0900 <.025 <.025 .03 <.025 <.025

07/20/04 0800 <.025 <.025 <.025 <.025 <.025

09/13/04 1530 <.025 <.025 <.025 <.025 <.025

Supplemental Information 
Table 9. Concentrations of triazine and phenylurea herbicides and their degradation products analyzed by the U.S. Geological Survey 

Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[<, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Concentration, in micrograms per liter

Deethylcyanazine

amide

PrometonPropazineSimazine

Hydroxysimazine

5 05490500 Des Moines River at Keosauqua 03/18/04 1230 <0.025 -- <0.025 <0.025 <0.025

04/22/04 0910 <.025 -- <.025 <.025 <.025

05/17/04 1400 <.025 -- <.025 <.025 <.025

06/14/04 1400 <.025 <0.025 <.025 <.025 <.025

07/19/04 1600 <.025 <.025 <.025 <.025 <.025

09/13/04 1330 <.025 <.025 <.025 <.025 <.025

6 06485500 Big Sioux River at Akron 03/09/04 1200 <.025 -- <.025 <.025 <.025

04/13/04 0930 <.025 -- <.025 <.025 <.025

05/12/04 1030 <.025 -- <.025 <.025 <.025

05/26/04 1300 <.025 <.025 <.025 <.025 <.025

06/02/04 1215 <.025 <.025 <.025 <.025 <.025

07/14/04 1030 <.025 <.025 <.025 <.025 <.025

7 06607500 Little Sioux River near Turin 03/10/04 0830 <.025 -- <.025 <.025 <.025

04/13/04 1400 <.025 -- <.025 <.025 <.025

05/11/04 1020 <.025 -- <.025 <.025 <.025

05/24/04 1100 <.025 <.025 .03 .04 <.025

06/08/04 0850 <.025 <.025 <.025 <.025 <.025

06/17/04 1230 <.025 <.025 .05 <.025 <.025

07/13/04 1000 <.025 <.025 <.025 <.025 <.025

8 06609500 Boyer River at Logan 03/12/04 0930 <.025 -- <.025 <.025 <.025

04/14/04 0730 <.025 -- <.025 <.025 <.025

05/11/04 1300 <.025 -- <.025 <.025 <.025

05/23/04 1015 <.025 <.025 .14 .06 <.025

06/08/04 1130 <.025 <.025 <.025 <.025 <.025

06/17/04 1000 <.025 <.025 .07 .05 <.025

07/13/04 1230 <.025 <.025 <.025 <.025 <.025
Table 9. Concentrations of triazine and phenylurea herbicides and their degradation products analyzed by the U.S. Geological Survey 

Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[<, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Concentration, in micrograms per liter

Deethylcyanazine

amide

PrometonPropazineSimazine

Hydroxysimazine

9 06810000 Nishnabotna River above 

Hamburg

03/11/04 1030 <0.025 -- <0.025 <0.025 <0.025

03/29/04 1230 <.025 -- <.025 <.025 <.025

04/12/04 1300 <.025 -- <.025 <.025 <.025

05/10/04 1230 <.025 <0.025 .21 .08 <.025

05/25/04 1045 <.025 <.025 .06 .02 <.025

06/07/04 1245 <.025 <.025 <.025 <.025 <.025

07/12/04 1230 <.025 <.025 <.025 <.025 <.025

10 06904010 Chariton River near Moulton 03/18/04 0900 <.025 <.025 <.025 <.025 <.025

04/22/04 1320 <.025 -- <.025 .03 <.025

05/17/04 1100 <.025 -- <.025 <.025 <.025

06/14/04 1050 <.025 <.025 <.025 .03 <.025

07/19/04 1230 <.025 <.025 <.025 .05 <.025

09/13/04 1030 <.025 <.025 <.025 <.025 <.025

Supplemental Information 1
Table 9. Concentrations of triazine and phenylurea herbicides and their degradation products analyzed by the U.S. Geological Survey 

Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[<, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

 Concentration, in micrograms per liter

Diuron Fluometuron

Demethylfluometuron

Linuron

1 05412500 Turkey River at Garber 03/15/04 1100 <0.020 <0.020 <0.020 <0.020

04/20/04 0950 <.020 <.020 <.020 <.020

05/19/04 1200 <.020 <.020 <.020 <.020

05/24/04 1115 <.020 <.020 <.020 <.020

06/10/04 1000 <.020 <.020 <.020 <.020

07/21/04 1130 <.020 <.020 <.020 <.020

09/14/04 1300 <.020 <.020 <.020 <.020

2 05418600 Maquoketa River near Spragueville 03/15/04 1700 <.020 <.020 <.020 <.020

03/29/04 1500 <.020 <.020 <.020 <.020

04/20/04 1510 <.020 <.020 <.020 <.020

05/19/04 0800 <.020 <.020 <.020 <.020

05/25/04 1015 <.020 <.020 <.020 <.020

06/10/04 1300 <.020 <.020 <.020 <.020

07/21/04 0720 <.020 <.020 <.020 <.020

09/14/04 1000 <.020 <.020 <.020 <.020

3 05422000 Wapsipinicon River near DeWitt 03/17/04 0830 <.020 <.020 <.020 <.020

04/15/04 0830 <.020 <.020 <.020 <.020

05/18/04 1200 <.020 <.020 <.020 <.020

05/25/04 1430 <.020 <.020 <.020 <.020

06/16/04 1230 <.020 <.020 <.020 <.020

07/20/04 1200 <.020 <.020 <.020 <.020

09/14/04 0730 <.020 <.020 <.020 <.020

4 05474000 Skunk River at Augusta 03/17/04 1430 <.020 <.020 <.020 <.020

04/15/04 1345 <.020 <.020 <.020 <.020

05/18/04 0730 <.020 <.020 <.020 <.020

06/16/04 0900 <.020 <.020 <.020 <.020

07/20/04 0800 <.020 <.020 <.020 <.020

09/13/04 1530 <.020 <.020 <.020 <.020

5 05490500 Des Moines River at Keosauqua 03/18/04 1230 <.020 <.020 <.020 <.020
Table 9. Concentrations of triazine and phenylurea herbicides and their degradation products analyzed by the U.S. Geological Survey 

Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[<, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

 Concentration, in micrograms per liter

Diuron Fluometuron

Demethylfluometuron

Linuron

5 05490500 Des Moines River at Keosauqua 04/22/04 0910 <0.020 <0.020 <0.020 <0.020

05/17/04 1400 <.020 <.020 <.020 <.020

06/14/04 1400 <.020 <.020 <.020 <.020

07/19/04 1600 <.020 <.020 <.020 <.020

09/13/04 1330 <.020 <.020 <.020 <.020

6 06485500 Big Sioux River at Akron 03/09/04 1200 <.020 <.020 <.020 <.020

04/13/04 0930 <.020 <.020 <.020 <.020

05/12/04 1030 <.020 <.020 <.020 <.020

05/26/04 1300 <.020 <.020 <.020 <.020

06/02/04 1215 <.020 <.020 <.020 <.020

07/14/04 1030 <.020 <.020 <.020 <.020

7 06607500 Little Sioux River near Turin 03/10/04 0830 <.020 <.020 <.020 <.020

04/13/04 1400 <.020 <.020 <.020 <.020

05/11/04 1020 <.020 <.020 <.020 <.020

05/24/04 1100 <.020 <.020 <.020 <.020

06/08/04 0850 <.020 <.020 <.020 <.020

06/17/04 1230 <.020 <.020 <.020 <.020

07/13/04 1000 <.020 <.020 <.020 <.020

8 06609500 Boyer River at Logan 03/12/04 0930 <.020 <.020 <.020 <.020

04/14/04 0730 <.020 <.020 <.020 <.020

05/11/04 1300 <.020 <.020 <.020 <.020

05/23/04 1015 <.020 <.020 <.020 <.020

06/08/04 1130 <.020 <.020 <.020 <.020

06/17/04 1000 <.020 <.020 <.020 <.020

07/13/04 1230 <.020 <.020 <.020 <.020

9 06810000 Nishnabotna River above Hamburg 03/11/04 1030 <.020 <.020 <.020 <.020

03/29/04 1230 <.020 <.020 <.020 <.020

04/12/04 1300 <.020 <.020 <.020 <.020

05/10/04 1230 <.020 <.020 <.020 <.020

05/25/04 1045 <.020 <.020 <.020 <.020

Supplemental Information 
Table 9. Concentrations of triazine and phenylurea herbicides and their degradation products analyzed by the U.S. Geological Survey 

Organic Geochemistry Research Laboratory, Lawrence, Kansas, for water samples collected from 10 rivers in Iowa, 2004.—Continued

[<, less than; --, no data]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

 Concentration, in micrograms per liter

Diuron Fluometuron

Demethylfluometuron

Linuron

9 06810000 Nishnabotna River above Hamburg 06/07/04 1245 <0.020 <0.020 <0.020 <0.020

07/12/04 1230 <.020 <.020 <.020 <.020

10 06904010 Chariton River near Moulton 03/18/04 0900 <.020 <.020 <.020 <.020

04/22/04 1320 .38 <.020 <.020 <.020

05/17/04 1100 <.020 <.020 <.020 <.020

06/14/04 1050 <.020 <.020 <.020 <.020

07/19/04 1230 <.020 <.020 <.020 <.020

09/13/04 1030 .020 <.020 <.020 <.020
Table 10. Concentrations of selected pesticides and pesticide degradation products determined by the U.S. Geological Survey National 

Water-Quality Laboratory, Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 rivers in Iowa, 2004.

[E, estimated; EPTC, s-ethyl dipropylthiocarbamate; <, less than; --, not detected]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of 

collection

(month/

day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

AcetochlorAlachlorAtrazineCarbarylCarbofuranChloropyrifos

1 05412500 Turkey River at Garber 03/15/04 1100 0.038 <0.007 0.104 <0.041 <0.020 <0.005

04/20/04 0950 .029 <.005 .125 <.041 <.020 <.005

05/19/04 1200 2.5 .014 5.6 <.041 <.020 <.005

05/24/04 1100 4.9 .147 7.1 <.041 <.020 .009

06/10/04 1000 .336 .008 1.9 <.041 E.016 .037

07/21/04 1130 .019 <.005 .264 <.041 <.020 <.005

08/17/04 1445 .016 <.005 .189 <.041 <.020 <.005

09/14/04 1300 .008 <.005 .147 <.041 <.020 <.005

10/18/04 1030 E.005 <.005 .112 <.041 <.020 <.005

11/16/04 0901 <.006 <.005 .093 <.041 <.020 <.005

12/06/04 0955 <.006 <.005 .073 <.041 <.020 <.005

2 05418600 Maquoketa River near 

Spragueville

03/15/04 1700 .009 .006 .074 <.041 <.020 <.005

03/29/04 1500 .015 .008 .090 <.041 <.020 <.005

04/20/04 1510 .052 <.005 .154 <.041 <.020 <.005

05/19/04 0800 .526 .007 1.5 <.041 <.020 .006

05/25/04 1000 5.5 .080 10 <.041 E.092 .013

06/10/04 1300 .075 E.005 .571 <.041 E.006 E.004

07/21/04 0720 .017 <.005 .238 <.041 <.020 <.005

08/17/04 1025 .009 <.005 .135 <.041 <.020 <.005

09/14/04 1000 <.010 <.005 .095 <.041 <.020 <.005

10/18/04 1330 E.005 <.005 .096 <.041 <.020 <.005

11/17/04 0710 <.006 <.005 .091 <.041 <.020 <.005

12/06/04 1340 .047 <.010 .099 <.041 <.020 <.005

3 05422000 Wapsipinicon River near 

DeWitt

03/17/04 0830 .023 .007 .078 <.041 <.020 <.005

04/15/04 0830 .012 <.005 .069 <.041 <.020 <.005

05/18/04 1200 3.4 .019 9.5 <.041 <.020 E.008

05/25/04 1400 3.2 .149 8.6 <.041 E.026 .010

06/16/04 1230 .219 .007 2.5 <.041 E.516 <.005

07/20/04 1200 .029 <.005 .517 <.041 E.031 <.005

Supplemental Information 
Table 10. Concentrations of selected pesticides and pesticide degradation products determined by the U.S. Geological Survey National 

Water-Quality Laboratory, Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 rivers in Iowa, 

2004.—Continued

[E, estimated; EPTC, s-ethyl dipropylthiocarbamate; <, less than; --, not detected]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of 

collection

(month/

day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

AcetochlorAlachlorAtrazineCarbarylCarbofuranChloropyrifos

3 05422000 Wapsipinicon River near 

DeWitt

08/17/04 0745 0.015 <0.005 0.247 <0.041 <0.020 <0.005

09/14/04 0730 .011 <.005 .173 <.041 <.020 <.005

10/18/04 1520 .006 <.005 .119 <.041 <.020 <.005

11/17/04 0845 <.010 <.005 .100 <.041 <.020 <.005

12/06/04 1615 .010 <.005 .062 <.041 <.020 <.005

4 05474000 Skunk River at Augusta 03/17/04 1430 .019 <.005 .099 <.041 <.020 <.005

04/15/04 1345 .013 <.005 .093 <.041 <.020 <.005

05/18/04 0730 .549 .006 2.6 <.041 <.020 <.010

06/16/04 0900 .279 .011 2.5 <.041 <.020 <.005

07/20/04 0800 .021 <.005 .363 <.041 <.020 <.005

08/16/04 1615 .017 <.005 .244 <.041 <.020 <.005

09/13/04 1530 .011 <.005 .150 <.041 <.020 <.005

10/19/04 0845 .007 <.005 .452 <.041 <.020 <.005

11/17/04 1130 <.020 <.005 .118 <.041 <.020 <.005

12/08/04 1150 .013 <.005 .106 <.041 <.020 <.005

5 05490500 Des Moines River at 

Keosauqua

03/18/04 1230 .049 <.007 .124 <.041 <.020 <.005

04/22/04 0910 .049 <.005 .147 <.041 <.020 <.005

05/17/04 1400 .422 .020 2.3 <.041 <.020 <.007

06/14/04 1400 .776 .017 2.6 <.041 <.040 <.005

07/19/04 1600 .148 <.005 1.4 <.041 <.020 <.005

08/16/04 1330 .018 <.005 .488 <.041 <.020 <.005

09/13/04 1330 .012 <.005 .313 <.041 <.020 <.005

10/19/04 1100 .013 <.005 .240 <.041 <.020 <.005

11/17/04 1400 <.006 <.005 .162 <.041 <.020 <.005

12/08/04 0900 .015 <.005 .104 <.041 <.020 <.005

6 06485500 Big Sioux River at Akron 03/09/04 1200 .500 <.005 .173 <.041 <.020 <.005

04/13/04 0930 .020 <.005 .045 <.041 <.020 <.005

05/12/04 1030 .063 .008 .140 <.041 <.020 <.005

05/26/04 1300 .911 .015 .759 E.008 <.020 E.005

06/02/04 1215 1.3 .057 1.8 E.016 E.005 .005
Table 10. Concentrations of selected pesticides and pesticide degradation products determined by the U.S. Geological Survey National 

Water-Quality Laboratory, Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 rivers in Iowa, 

2004.—Continued

[E, estimated; EPTC, s-ethyl dipropylthiocarbamate; <, less than; --, not detected]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of 

collection

(month/

day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

AcetochlorAlachlorAtrazineCarbarylCarbofuranChloropyrifos

6 06485500 Big Sioux River at Akron 07/14/04 1030 0.017 0.005 0.696 <0.041 <0.020 <0.005

08/11/04 0940 .012 <.005 .214 <.041 <.020 <.005

09/08/04 0730 .006 <.005 .092 <.041 <.020 <.005

09/17/04 1230 .015 <.005 .104 E.011 <.020 E.004

10/12/04 1600 <.006 <.005 .055 <.041 <.020 <.005

11/18/04 1100 <.006 <.005 .044 <.041 <.020 <.005

7 06607500 Little Sioux River near 

Turin

03/10/04 0830 .020 <.005 .109 <.041 <.020 <.005

04/13/04 1400 .019 <.005 .048 <.041 <.020 <.005

05/11/04 1020 .493 .031 2.3 <.041 <.020 <.005

05/24/04 1100 1.5 .016 4.8 <.041 <.020 .011

06/08/04 0850 .086 .005 .370 <.041 <.020 <.005

06/17/04 1230 .118 E.005 10 <.041 E.049 .007

07/13/04 1000 .026 <.005 .568 <.041 <.020 <.005

08/10/04 0900 .009 <.005 .180 <.041 <.020 <.005

09/08/04 1100 <.006 <.005 .094 <.041 <.020 E.004

09/20/04 1145 .035 <.005 .182 <.041 <.020 <.005

10/12/04 1300 <.006 <.005 .067 <.041 <.020 <.005

11/17/04 0945 <.006 <.005 .047 <.041 <.020 <.005

8 06609500 Boyer River at Logan 03/12/04 0930 .008 <.005 .084 <.041 <.020 <.005

04/14/04 0730 .023 <.005 .070 <.041 <.020 <.005

05/11/04 1300 .111 .007 .566 <.041 <.020 <.005

05/23/04 1015 5.2 .039 27 E.007 <.020 .012

06/08/04 1130 .038 <.005 .428 <.041 <.020 <.005

06/17/04 1000 .390 E.005 18 <.041 E.736 .006

07/13/04 1230 .016 <.005 .258 <.041 <.020 <.005

08/10/04 1130 .009 <.005 .175 <.041 <.020 E.004

09/07/04 1530 1.0 <.005 .239 <.041 <.020 <.005

10/12/04 1000 E.005 <.005 .061 <.041 <.020 <.005

11/17/04 1230 .013 <.005 .111 <.041 <.020 <.005

Supplemental Information 
Table 10. Concentrations of selected pesticides and pesticide degradation products determined by the U.S. Geological Survey National 

Water-Quality Laboratory, Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 rivers in Iowa, 

2004.—Continued

[E, estimated; EPTC, s-ethyl dipropylthiocarbamate; <, less than; --, not detected]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of 

collection

(month/

day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

AcetochlorAlachlorAtrazineCarbarylCarbofuranChloropyrifos

9 06810000 Nishnabotna River above 

Hamburg 

03/11/04 1030 0.009 <0.005 0.078 <0.041 <0.020 <0.005

03/29/04 1230 .026 <.005 .160 <.041 <.020 .006

04/12/04 1300 .017 <.005 .070 <.041 <.020 <.005

05/10/04 1230 2.3 .240 E41.7 E.007 <.020 .008

05/25/04 1045 .884 .051 8.7 E.007 <.020 .027

06/07/04 1245 .051 .006 .781 <.041 <.020 <.005

07/12/04 1230 .032 <.005 .681 <.041 <.020 <.005

08/09/04 1230 .015 <.005 .239 <.041 <.020 E.004

09/07/04 1230 .025 <.005 .273 <.041 <.020 <.005

10/13/04 0800 <.006 <.005 .065 <.041 <.020 <.005

11/16/04 1300 E.004 <.005 .041 <.041 <.020 <.005

10 06904010 Chariton River near 

Moulton

03/18/04 0900 .011 .006 .657 <.041 <.020 <.005

04/22/04 1320 .022 <.005 .493 <.041 <.020 <.005

05/17/04 1100 .065 <.005 .555 <.041 <.020 <.005

06/14/04 1050 .206 <.005 1.3 <.041 <.020 <.005

07/19/04 1230 .083 <.005 1.1 <.041 <.020 <.005

08/16/04 1030 .047 <.005 1.1 <.041 <.020 <.005

09/13/04 1030 .036 <.005 .853 <.041 <.020 <.005
Table 10. Concentrations of selected pesticides and pesticide degradation products determined by the U.S. Geological Survey 

National Water-Quality Laboratory, Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 rivers in 

Iowa, 2004.—Continued

[E, estimated; EPTC, s-ethyl dipropylthiocarbamate; <, less than; --, not detected]

Map

number

(fig. 4)

U.S. Geological

Survey 

site

identification number

Site name

Date of 

collection

(month/

day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

Cyanazine

Deethylatrazine

Dacthal Desulfinyl

fipronil

DiazinonDieldrin

1 05412500 Turkey River at Garber 03/15/04 1100 <0.018 E0.051 <0.003 <0.012 0.008 <0.009

04/20/04 0950 <.018 E.058 <.003 <.012 <.005 <.009

05/19/04 1200 <.018 E.184 <.003 <.012 <.005 <.009

05/24/04 1100 .021 E.475 <.003 <.012 <.005 <.009

06/10/04 1000 E.013 E.166 <.003 <.012 <.005 <.009

07/21/04 1130 <.018 E.091 <.003 <.012 <.005 <.009

08/17/04 1445 <.018 E.112 <.003 <.012 <.005 <.009

09/14/04 1300 <.018 E.078 <.003 <.012 <.005 <.009

10/18/04 1030 <.018 E.075 <.003 <.012 <.005 <.200

11/16/04 0901 <.018 E.067 <.003 <.012 <.005 <.009

12/06/04 0955 <.018 E.048 <.003 <.012 <.005 <.009

2 05418600 Maquoketa River near 

Spragueville

03/15/04 1700 <.018 E.065 <.003 <.012 <.005 <.009

03/29/04 1500 <.018 E.088 <.003 <.012 <.005 <.009

04/20/04 1510 <.018 E.074 <.003 <.012 <.005 <.009

05/19/04 0800 <.018 E.128 <.003 <.012 <.005 <.009

05/25/04 1000 .023 E.440 <.003 <.012 <.005 <.009

06/10/04 1300 <.018 E.114 <.003 <.012 <.005 <.009

07/21/04 0720 <.018 E.100 <.003 <.012 <.005 <.009

08/17/04 1025 <.018 E.078 <.003 <.012 <.005 <.009

09/14/04 1000 <.018 E.079 <.003 <.012 <.005 <.009

10/18/04 1330 <.018 E.088 <.003 <.012 <.005 <.020

11/17/04 0710 <.018 E.069 <.003 <.012 <.005 <.009

12/06/04 1340 <.018 E.052 <.003 <.012 <.005 <.009

3 05422000 Wapsipinicon River near 

DeWitt

03/17/04 0830 <.018 E.050 <.003 <.012 <.005 <.009

04/15/04 0830 <.018 E.054 <.003 <.012 <.005 <.009

05/18/04 1200 E.015 E.265 <.003 <.012 <.005 <.009

05/25/04 1400 E.017 E.418 .003 <.012 <.005 <.009

06/16/04 1230 <.018 E.228 <.003 <.012 <.005 <.009

Supplemental Information 
Table 10. Concentrations of selected pesticides and pesticide degradation products determined by the U.S. Geological Survey 

National Water-Quality Laboratory, Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 rivers in 

Iowa, 2004.—Continued

[E, estimated; EPTC, s-ethyl dipropylthiocarbamate; <, less than; --, not detected]

Map

number

(fig. 4)

U.S. Geological

Survey 

site

identification number

Site name

Date of 

collection

(month/

day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

Cyanazine

Deethylatrazine

Dacthal Desulfinyl

fipronil

DiazinonDieldrin

3 05422000 Wapsipinicon River near 

DeWitt

07/20/04 1200 <0.018 E0.165 <0.003 <0.012 <0.005 <0.009

08/17/04 0745 <.018 E.073 <.003 <.012 <.005 <.009

09/14/04 0730 <.018 E.068 <.003 <.012 <.005 <.009

10/18/04 1520 <.018 E.067 <.003 <.012 <.005 <.009

11/17/04 0845 <.018 E.053 <.003 <.012 <.005 <.009

12/06/04 1615 <.018 E.041 <.003 <.012 <.005 <.009

4 05474000 Skunk River at Augusta 03/17/04 1430 <.018 E.037 <.003 <.012 <.005 <.009

04/15/04 1345 <.018 E.038 <.003 <.012 <.005 <.009

05/18/04 0730 E.007 E.113 <.003 <.012 <.005 <.009

06/16/04 0900 E.018 E.433 <.003 <.012 <.005 <.009

07/20/04 0800 <.018 E.079 <.003 <.012 <.005 <.009

08/16/04 1615 <.018 E.056 <.003 <.012 <.005 <.009

09/13/04 1530 <.018 E.051 <.003 <.012 <.005 <.009

10/19/04 0845 <.018 E.034 <.003 E.004 <.005 <.009

11/17/04 1130 <.018 E.056 <.003 <.012 <.005 <.009

12/08/04 1150 <.018 E.038 <.003 <.012 <.005 <.009

5 05490500 Des Moines River at 

Keosauqua

03/18/04 1230 <.018 E.025 <.003 <.012 <.005 <.009

04/22/04 0910 <.018 E.028 <.003 <.012 <.005 <.009

05/17/04 1400 E.008 E.071 <.003 E.004 <.005 <.009

06/14/04 1400 <.018 E.199 <.003 <.012 <.005 <.009

07/19/04 1600 <.018 E.126 <.003 <.012 <.005 <.009

08/16/04 1330 <.018 E.067 <.003 <.012 <.005 <.009

09/13/04 1330 <.018 E.059 <.003 <.012 <.005 <.009

10/19/04 1100 <.018 E.052 <.003 <.012 <.005 <.009

11/17/04 1400 <.018 E.040 <.003 <.012 <.005 <.009

12/08/04 0900 <.018 E.024 <.003 <.012 <.005 <.009

6 06485500 Big Sioux River at Akron 03/09/04 1200 <.018 E.042 <.003 <.012 <.005 <.009

04/13/04 0930 <.018 E.015 <.003 <.012 <.005 <.009

05/12/04 1030 <.018 E.030 <.003 E.003 <.005 <.009
Table 10. Concentrations of selected pesticides and pesticide degradation products determined by the U.S. Geological Survey 

National Water-Quality Laboratory, Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 rivers in 

Iowa, 2004.—Continued

[E, estimated; EPTC, s-ethyl dipropylthiocarbamate; <, less than; --, not detected]

Map

number

(fig. 4)

U.S. Geological

Survey 

site

identification number

Site name

Date of 

collection

(month/

day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

Cyanazine

Deethylatrazine

Dacthal Desulfinyl

fipronil

DiazinonDieldrin

6 06485500 Big Sioux River at Akron 05/26/04 1300 E0.010 E0.060 <0.003 E0.004 0.006 <0.009

06/02/04 1215 E.018 E.109 <.003 E.003 <.005 <.009

07/14/04 1030 <.018 E.045 <.003 <.012 <.005 <.009

08/11/04 0940 <.018 E.037 <.003 <.012 <.005 <.009

09/08/04 0730 <.018 E.015 <.003 E.003 E.002 <.009

09/17/04 1230 <.018 E.024 E.002 E.003 E.004 <.009

10/12/04 1600 <.018 E.018 <.003 <.012 <.005 <.009

11/18/04 1100 <.018 E.013 <.003 <.012 <.005 <.009

7 06607500 Little Sioux River near Turin 03/10/04 0830 <.018 E.032 <.003 <.012 <.005 <.009

04/13/04 1400 <.018 E.017 <.003 <.012 <.005 <.009

05/11/04 1020 <.018 E.093 <.003 <.012 <.005 <.009

05/24/04 1100 E.012 E.229 <.003 <.012 <.005 <.009

06/08/04 0850 <.018 E.048 <.003 <.012 <.005 <.009

06/17/04 1230 .026 E.245 <.003 E.003 <.005 <.009

07/13/04 1000 <.018 E.042 <.003 <.012 <.005 <.009

08/10/04 0900 <.018 E.027 <.003 <.012 <.005 <.009

09/08/04 1100 <.018 E.016 <.003 <.012 <.005 <.009

09/20/04 1145 <.018 E.057 <.003 <.012 <.005 <.009

10/12/04 1300 <.018 E.027 <.003 <.012 <.005 <.009

11/17/04 0945 <.018 E.025 <.003 <.012 <.005 <.009

8 06609500 Boyer River at Logan 03/12/04 0930 <.018 E.027 <.003 <.012 <.005 <.009

04/14/04 0730 <.018 E.019 <.003 <.012 <.005 <.009

05/11/04 1300 <.018 E.045 <.003 <.012 <.005 <.009

05/23/04 1015 .029 E.668 <.003 <.012 <.005 <.009

06/08/04 1130 <.018 E.042 <.003 <.012 <.005 <.009

06/17/04 1000 E.015 E.418 <.003 E.003 <.005 <.009

07/13/04 1230 <.018 E.028 <.003 <.012 <.005 <.009

08/10/04 1130 <.018 E.029 <.003 <.012 <.005 <.009

09/07/04 1530 E.007 E.016 <.003 <.012 <.005 <.009

Supplemental Information 1
Table 10. Concentrations of selected pesticides and pesticide degradation products determined by the U.S. Geological Survey 

National Water-Quality Laboratory, Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 rivers in 

Iowa, 2004.—Continued

[E, estimated; EPTC, s-ethyl dipropylthiocarbamate; <, less than; --, not detected]

Map

number

(fig. 4)

U.S. Geological

Survey 

site

identification number

Site name

Date of 

collection

(month/

day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

Cyanazine

Deethylatrazine

Dacthal Desulfinyl

fipronil

DiazinonDieldrin

8 06609500 Boyer River at Logan 10/12/04 1000 <0.018 E0.012 <0.003 <0.012 <0.005 <0.009

11/17/04 1230 <.018 E.021 <.003 <.012 <.005 <.009

9 06810000 Nishnabotna River above 

Hamburg 

03/11/04 1030 <.018 E.024 <.003 <.012 <.005 <.009

03/29/04 1230 E.012 E.028 <.003 <.012 <.005 <.009

04/12/04 1300 <.018 E.023 <.003 <.012 <.005 <.009

05/10/04 1230 .019 E.441 <.003 <.012 <.005 E.006

05/25/04 1045 .516 E.469 <.003 <.012 <.005 <.009

06/07/04 1245 E.008 E.076 <.003 <.012 <.005 E.003

07/12/04 1230 <.018 E.068 <.003 <.012 <.005 <.009

08/09/04 1230 <.018 E.036 <.003 <.012 <.005 <.009

09/07/04 1230 E.016 E.025 <.003 <.012 <.005 <.009

10/13/04 0800 <.018 E.017 <.003 <.012 <.005 <.009

11/16/04 1300 <.018 E.014 <.003 <.012 <.005 <.009

10 06904010 Chariton River near Moulton 03/18/04 0900 <.018 E.222 <.003 <.012 <.005 <.009

04/22/04 1320 <.018 E.107 <.003 <.012 <.005 <.009

05/17/04 1100 <.018 E.158 <.003 <.012 <.005 <.009

06/14/04 1050 <.018 E.343 <.003 <.012 <.005 <.009

07/19/04 1230 <.018 E.270 <.003 <.012 <.005 <.009

08/16/04 1030 <.018 E.235 <.003 <.012 <.005 <.009

09/13/04 1030 <.018 E.223 <.003 <.012 <.005 <.009
Table 10. Concentrations of selected pesticides and pesticide degradation products determined by the U.S. Geological Survey 

National Water-Quality Laboratory, Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 rivers in 

Iowa, 2004.—Continued

[E, estimated; EPTC, s-ethyl dipropylthiocarbamate; <, less than; --, not detected]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

EPTC Fipronil

sulfide

Fipronil

sulfone Fipronil Fonofos

1 05412500 Turkey River at Garber 03/15/04 1100 <0.004 <0.013 <0.024 <0.016 <0.003

04/20/04 0950 <.004 <.013 <.024 <.016 <.003

05/19/04 1200 E.002 <.013 <.024 <.016 <.003

05/24/04 1100 <.004 <.013 E.007 E.013 <.003

06/10/04 1000 <.004 <.013 <.024 <.016 <.003

07/21/04 1130 <.004 <.013 <.024 <.016 <.003

08/17/04 1445 <.004 <.013 <.024 <.016 <.003

09/14/04 1300 <.004 <.013 <.024 <.016 <.003

10/18/04 1030 <.004 <.013 <.024 <.016 <.003

11/16/04 0901 <.004 <.013 <.024 <.016 <.003

12/06/04 0955 <.004 <.013 <.024 <.016 <.003

2 05418600 Maquoketa River near 

Spragueville

03/15/04 1700 <.004 <.013 <.024 <.016 <.003

03/29/04 1500 <.004 <.013 <.024 <.016 <.003

04/20/04 1510 <.004 <.013 <.024 <.016 <.003

05/19/04 0800 <.004 <.013 <.024 <.016 <.003

05/25/04 1000 .006 <.013 <.024 E.019 <.003

06/10/04 1300 <.004 <.013 <.024 <.016 <.003

07/21/04 0720 <.004 <.013 <.024 <.016 <.003

08/17/04 1025 <.004 <.013 <.024 <.016 <.003

09/14/04 1000 <.004 <.013 <.024 <.016 <.003

10/18/04 1330 <.004 <.013 <.024 <.016 <.003

11/17/04 0710 <.004 <.013 <.024 <.016 <.003

12/06/04 1340 <.004 <.013 <.024 <.016 <.003

3 05422000 Wapsipinicon River near 

DeWitt

03/17/04 0830 <.004 <.013 <.024 <.016 <.003

04/15/04 0830 <.004 <.013 <.024 <.016 <.003

05/18/04 1200 <.004 <.013 <.024 <.016 <.003

05/25/04 1400 E.004 <.013 <.024 E.016 <.003

06/16/04 1230 <.004 <.013 <.024 <.016 <.003

07/20/04 1200 <.004 <.013 <.024 <.016 <.003

Supplemental Information 
Table 10. Concentrations of selected pesticides and pesticide degradation products determined by the U.S. Geological Survey 

National Water-Quality Laboratory, Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 rivers in 

Iowa, 2004.—Continued

[E, estimated; EPTC, s-ethyl dipropylthiocarbamate; <, less than; --, not detected]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

EPTC Fipronil

sulfide

Fipronil

sulfone Fipronil Fonofos

3 05422000 Wapsipinicon River near 

DeWitt

08/17/04 0745 <0.004 <0.013 <0.024 <0.016 <0.003

09/14/04 0730 <.004 <.013 <.024 <.016 <.003

10/18/04 1520 <.004 <.013 <.024 <.016 <.003

11/17/04 0845 <.004 <.013 <.024 <.016 <.003

12/06/04 1615 <.004 <.013 <.024 <.016 <.003

4 05474000 Skunk River at Augusta 03/17/04 1430 <.004 <.013 <.024 <.016 <.003

04/15/04 1345 <.004 <.013 <.024 <.016 <.003

05/18/04 0730 <.004 <.013 <.024 <.016 <.003

06/16/04 0900 <.004 <.013 <.024 <.016 <.003

07/20/04 0800 <.004 <.013 <.024 <.016 <.003

08/16/04 1615 <.004 <.013 <.024 <.016 <.003

09/13/04 1530 <.004 <.013 <.024 <.016 <.003

10/19/04 0845 <.004 <.013 <.024 <.016 <.003

11/17/04 1130 <.004 <.013 <.024 <.016 <.003

12/08/04 1150 <.004 <.013 <.024 <.016 <.003

5 05490500 Des Moines River at 

Keosauqua

03/18/04 1230 <.004 <.013 <.024 <.016 <.003

04/22/04 0910 <.004 <.013 <.024 <.016 <.003

05/17/04 1400 <.007 <.013 <.024 E.004 <.003

06/14/04 1400 <.004 <.013 <.024 <.016 <.003

07/19/04 1600 <.004 <.013 <.024 <.016 <.003

08/16/04 1330 <.004 <.013 <.024 <.016 <.003

09/13/04 1330 <.004 <.013 <.024 <.016 <.003

10/19/04 1100 <.004 <.013 <.024 <.016 <.003

11/17/04 1400 <.004 <.013 <.024 <.016 <.003

12/08/04 0900 <.004 <.013 <.024 <.016 <.003

6 06485500 Big Sioux River at Akron 03/09/04 1200 <.004 <.013 <.024 <.016 <.003

04/13/04 0930 <.004 <.013 <.024 <.016 <.003

05/12/04 1030 E.003 <.013 <.024 <.016 <.003

05/26/04 1300 E.003 <.013 <.024 E.014 <.003

06/02/04 1215 .008 <.013 E.005 E.019 <.003
Table 10. Concentrations of selected pesticides and pesticide degradation products determined by the U.S. Geological Survey 

National Water-Quality Laboratory, Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 rivers in 

Iowa, 2004.—Continued

[E, estimated; EPTC, s-ethyl dipropylthiocarbamate; <, less than; --, not detected]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

EPTC Fipronil

sulfide

Fipronil

sulfone Fipronil Fonofos

6 06485500 Big Sioux River at Akron 07/14/04 1030 <0.004 <0.013 <0.024 <0.016 <0.003

08/11/04 0940 <.004 <.013 <.024 <.016 <.003

09/08/04 0730 <.004 <.013 <.024 <.016 <.003

09/17/04 1230 <.004 <.013 <.024 <.016 <.003

10/12/04 1600 <.004 <.013 <.024 <.016 <.003

11/18/04 1100 <.004 <.013 <.024 <.016 <.003

7 06607500 Little Sioux River near 

Turin

03/10/04 0830 <.004 <.013 <.024 <.016 <.003

04/13/04 1400 <.004 <.013 <.024 <.016 <.003

05/11/04 1020 <.004 <.013 <.024 <.016 <.003

05/24/04 1100 E.003 <.013 <.024 E.009 <.003

06/08/04 0850 <.004 <.013 <.024 <.016 <.003

06/17/04 1230 <.004 E.003 E.006 E.014 <.003

07/13/04 1000 <.004 <.013 <.024 <.016 <.003

08/10/04 0900 <.008 <.013 <.024 <.016 <.003

09/08/04 1100 <.004 <.013 <.024 <.016 <.003

09/20/04 1145 <.004 <.013 <.024 <.016 <.003

10/12/04 1300 <.004 <.013 <.024 <.016 <.003

11/17/04 0945 <.004 <.013 <.024 <.016 <.003

8 06609500 Boyer River at Logan 03/12/04 0930 <.004 <.013 <.024 <.016 <.003

04/14/04 0730 <.004 <.013 <.024 <.016 <.003

05/11/04 1300 <.004 <.013 <.024 <.016 <.003

05/23/04 1015 E.003 <.013 <.024 E.006 <.003

06/08/04 1130 <.004 <.013 <.024 <.016 <.003

06/17/04 1000 <.004 <.013 E.005 E.010 <.003

07/13/04 1230 <.004 <.013 <.024 <.016 <.003

08/10/04 1130 <.004 <.013 <.024 <.016 <.003

09/07/04 1530 <.004 <.013 <.024 <.016 <.003

10/12/04 1000 <.004 <.013 <.024 <.016 <.003

11/17/04 1230 <.004 <.013 <.024 <.016 <.003

Supplemental Information 
Table 10. Concentrations of selected pesticides and pesticide degradation products determined by the U.S. Geological Survey 

National Water-Quality Laboratory, Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 rivers in 

Iowa, 2004.—Continued

[E, estimated; EPTC, s-ethyl dipropylthiocarbamate; <, less than; --, not detected]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

EPTC Fipronil

sulfide

Fipronil

sulfone Fipronil Fonofos

9 06810000 Nishnabotna River above 

Hamburg 

03/11/04 1030 <0.004 <0.013 <0.024 <0.016 <0.003

03/29/04 1230 <.004 <.013 <.024 <.016 <.003

04/12/04 1300 <.004 <.013 <.024 <.016 <.003

05/10/04 1230 <.004 <.013 E.006 E.009 <.003

05/25/04 1045 <.004 <.013 E.008 E.031 .024

06/07/04 1245 <.004 <.013 <.024 <.016 <.003

07/12/04 1230 <.004 <.013 <.024 <.016 <.003

08/09/04 1230 <.004 <.013 <.024 <.016 <.003

09/07/04 1230 <.004 <.013 <.024 <.016 <.003

10/13/04 0800 <.004 <.013 <.024 <.016 <.003

11/16/04 1300 <.004 <.013 <.024 <.016 <.003

10 06904010 Chariton River near 

Moulton

03/18/04 0900 <.004 <.013 <.024 <.016 <.003

04/22/04 1320 <.004 <.013 <.024 <.016 <.003

05/17/04 1100 <.004 <.013 <.024 <.016 <.003

06/14/04 1050 <.004 <.013 <.024 <.016 <.003

07/19/04 1230 <.004 <.013 <.024 <.016 <.003

08/16/04 1030 <.004 <.013 <.024 <.016 <.003

09/13/04 1030 <.004 <.013 <.024 <.016 <.003
Table 10. Concentrations of selected pesticides and pesticide degradation products determined by the U.S. Geological Survey 

National Water-Quality Laboratory, Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 rivers in 

Iowa, 2004 —Continued

[E, estimated; EPTC, s-ethyl dipropylthiocarbamate; <, less than; --, not detected]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of 

collection

(month/

day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

MetolachlorMetribuzinp,p’-

DDE

Pendamethalin

Prometon

Propachlor

1 05412500 Turkey River at Garber 03/15/04 1100 0.08 <0.006 <0.003 <0.022 <0.01 <0.025

04/20/04 0950 .031 <.006 <.003 <.022 .01 <.025

05/19/04 1200 .594 .013 <.003 <.022 .01 <.025

05/24/04 1100 .930 .029 <.010 E.011 .01 <.025

06/10/04 1000 .415 <.006 <.003 <.022 .01 <.025

07/21/04 1130 .025 <.006 <.003 <.022 <.01 <.025

08/17/04 1445 .019 <.006 <.003 <.022 .01 <.025

09/14/04 1300 .015 <.006 <.003 <.022 .01 <.025

10/18/04 1030 .011 <.006 <.015 <.022 E.01 <.025

11/16/04 0901 .011 <.006 <.003 <.022 <.01 <.025

12/06/04 0955 .011 <.006 <.003 <.022 .01 <.025

2 05418600 Maquoketa River near 

Spragueville

03/15/04 1700 .024 <.006 <.003 <.022 <.01 <.025

03/29/04 1500 .053 <.006 <.003 <.022 .01 <.025

04/20/04 1510 .041 <.006 <.003 <.022 .01 <.025

05/19/04 0800 .238 .006 <.003 <.022 .01 <.025

05/25/04 1000 2.8 .019 <.010 <.022 .01 <.025

06/10/04 1300 .128 <.006 E.002 <.022 .01 <.025

07/21/04 0720 .039 <.006 <.003 <.022 .01 <.025

08/17/04 1025 .022 <.006 <.003 <.022 .01 <.025

09/14/04 1000 .015 <.006 <.003 <.022 <.01 <.025

10/18/04 1330 .011 <.006 <.015 <.022 E.01 <.025

11/17/04 0710 .011 <.006 <.003 <.022 <.01 <.025

12/06/04 1340 .019 <.006 <.003 <.022 <.01 <.025

3 05422000 Wapsipinicon River near 

DeWitt

03/17/04 0830 .102 <.006 <.003 <.022 <.01 <.025

04/15/04 0830 .042 <.006 <.003 <.022 .01 <.025

05/18/04 1200 1.6 <.006 <.003 <.022 .01 <.025

05/25/04 1400 2.4 .025 <.010 E.014 .01 <.025

06/16/04 1230 .310 <.010 <.003 <.022 .01 <.025

Supplemental Information 
Table 10. Concentrations of selected pesticides and pesticide degradation products determined by the U.S. Geological Survey 

National Water-Quality Laboratory, Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 rivers in 

Iowa, 2004 —Continued

[E, estimated; EPTC, s-ethyl dipropylthiocarbamate; <, less than; --, not detected]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of 

collection

(month/

day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

MetolachlorMetribuzinp,p’-

DDE

Pendamethalin

Prometon

Propachlor

3 05422000 Wapsipinicon River near 

DeWitt

07/20/04 1200 0.063 <0.006 <0.003 <0.022 0.01 <0.025

08/17/04 0745 .048 <.006 <.003 <.022 .01 <.025

09/14/04 0730 .039 <.006 <.003 <.022 .01 <.025

10/18/04 1520 .028 <.006 <.015 <.022 E.01 <.025

11/17/04 0845 .043 <.006 <.003 <.022 E.01 <.025

12/06/04 1615 .034 <.006 <.003 <.022 <.01 <.025

4 05474000 Skunk River at Augusta 03/17/04 1430 .228 <.006 <.003 <.022 <.01 <.025

04/15/04 1345 .085 <.006 <.003 <.022 .01 <.025

05/18/04 0730 1.2 <.006 <.003 <.022 .01 <.025

06/16/04 0900 .930 .009 <.003 <.022 .04 <.025

07/20/04 0800 .126 <.006 <.003 <.022 .01 <.025

08/16/04 1615 .085 <.006 <.003 <.022 <.01 <.025

09/13/04 1530 .067 <.006 <.003 <.022 .01 <.025

10/19/04 0845 .031 <.006 <.006 <.022 E.01 <.025

11/17/04 1130 .062 <.006 <.003 <.022 <.01 <.025

12/08/04 1150 .071 <.006 <.003 <.022 .02 <.025

5 05490500 Des Moines River at 

Keosauqua

03/18/04 1230 .953 <.006 <.003 <.022 .01 <.025

04/22/04 0910 .337 <.006 <.003 <.022 .01 <.025

05/17/04 1400 .612 <.006 <.003 <.022 .01 <.025

06/14/04 1400 .704 .012 <.003 <.022 .01 <.025

07/19/04 1600 .199 <.006 <.003 <.022 .02 <.025

08/16/04 1330 .074 <.006 <.003 <.022 .02 <.025

09/13/04 1330 .064 <.006 <.003 <.022 .02 <.025

10/19/04 1100 .053 <.006 <.003 <.022 .01 <.025

11/17/04 1400 .036 <.006 <.003 <.022 E.01 <.025

12/08/04 0900 .034 <.006 <.003 <.022 E.01 <.025

6 06485500 Big Sioux River at Akron 03/09/04 1200 1.7 <.006 <.003 <.022 <.01 <.025

04/13/04 0930 .111 <.006 <.003 <.022 .01 <.025

05/12/04 1030 .079 <.006 <.003 E.006 .01 <.025

05/26/04 1300 .387 .012 <.003 <.022 .02 <.025
Table 10. Concentrations of selected pesticides and pesticide degradation products determined by the U.S. Geological Survey 

National Water-Quality Laboratory, Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 rivers in 

Iowa, 2004 —Continued

[E, estimated; EPTC, s-ethyl dipropylthiocarbamate; <, less than; --, not detected]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of 

collection

(month/

day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

MetolachlorMetribuzinp,p’-

DDE

Pendamethalin

Prometon

Propachlor

6 06485500 Big Sioux River at Akron 06/02/04 1215 0.662 <0.007 <0.003 <0.022 0.01 <0.025

07/14/04 1030 .046 <.006 <.003 <.022 .01 <.025

08/11/04 0940 .045 <.006 <.003 <.022 .01 <.025

09/08/04 0730 .035 <.006 <.003 <.022 .03 <.025

09/17/04 1230 .049 <.006 <.005 <.022 .02 <.025

10/12/04 1600 .035 <.006 <.003 <.022 .01 <.025

11/18/04 1100 .014 <.006 <.003 <.022 <.01 <.025

7 06607500 Little Sioux River near 

Turin

03/10/04 0830 .472 <.006 <.003 <.022 <.01 <.025

04/13/04 1400 .071 <.006 <.003 <.022 .01 <.025

05/11/04 1020 .451 .015 <.003 E.013 <.01 <.025

05/24/04 1100 1.2 .019 <.003 .032 .01 <.025

06/08/04 0850 .113 E.005 <.003 <.022 .01 <.025

06/17/04 1230 .470 .007 <.015 .030 .01 E.004

07/13/04 1000 .070 <.006 <.003 <.022 .01 <.025

08/10/04 0900 .023 <.006 <.003 <.022 <.01 <.025

09/08/04 1100 .020 <.006 <.003 <.022 .01 <.025

09/20/04 1145 .081 <.006 <.003 <.022 .01 <.025

10/12/04 1300 .022 <.006 <.003 <.022 <.01 <.025

11/17/04 0945 .015 <.006 <.003 <.022 <.01 <.025

8 06609500 Boyer River at Logan 03/12/04 0930 .205 <.006 <.003 <.022 .02 <.025

04/14/04 0730 .042 <.006 <.003 <.022 .01 <.025

05/11/04 1300 .333 .007 <.003 <.022 .01 <.025

05/23/04 1015 3.9 .139 <.003 E.021 .01 <.025

06/08/04 1130 .146 E.004 <.003 <.022 <.01 <.025

06/17/04 1000 .650 .008 <.015 E.016 .01 <.025

07/13/04 1230 .053 <.006 <.003 <.022 .01 <.025

08/10/04 1130 .035 <.006 <.003 <.022 .02 <.025

09/07/04 1530 .111 <.006 <.003 <.022 .01 <.025

10/12/04 1000 .024 <.006 <.003 <.022 .01 <.025

Supplemental Information 
Table 10. Concentrations of selected pesticides and pesticide degradation products determined by the U.S. Geological Survey 

National Water-Quality Laboratory, Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 rivers in 

Iowa, 2004 —Continued

[E, estimated; EPTC, s-ethyl dipropylthiocarbamate; <, less than; --, not detected]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of 

collection

(month/

day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

MetolachlorMetribuzinp,p’-

DDE

Pendamethalin

Prometon

Propachlor

8 06609500 Boyer River at Logan 11/17/04 1230 0.022 <0.006 <0.003 <0.022 0.02 <0.025

9 06810000 Nishnabotna River above 

Hamburg 

03/11/04 1030 .027 <.006 <.003 <.022 <.01 <.025

03/29/04 1230 .066 <.006 <.003 E.007 .01 <.025

04/12/04 1300 .032 <.006 <.003 <.022 <.01 <.025

05/10/04 1230 .925 .053 <.003 E.017 .01 <.025

05/25/04 1045 3.1 .075 <.003 .028 .01 <.025

06/07/04 1245 .131 .006 <.003 E.009 .01 <.025

07/12/04 1230 .121 E.005 <.003 <.022 .02 <.025

08/09/04 1230 .041 <.006 <.003 <.022 .01 <.025

09/07/04 1230 .098 <.006 <.003 <.022 .01 <.025

10/13/04 0800 .012 <.006 <.003 <.022 <.01 <.025

11/16/04 1300 .014 <.006 <.003 <.022 <.01 <.025

10 06904010 Chariton River near 

Moulton

03/18/04 0900 .123 <.006 <.003 <.022 .01 <.025

04/22/04 1320 .079 <.006 <.003 <.022 .01 <.025

05/17/04 1100 .102 <.006 <.003 <.022 .04 <.025

06/14/04 1050 .193 <.006 <.003 <.022 .01 <.025

07/19/04 1230 .301 <.006 <.003 <.022 <.01 <.025

08/16/04 1030 .222 <.006 <.003 <.022 .01 <.025

09/13/04 1030 .228 <.006 <.003 <.022 <.01 <.025
Table 10. Concentrations of selected pesticides and pesticide degradation products determined by the U.S. Geological Survey 

National Water-Quality Laboratory, Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 rivers in 

Iowa, 2004. —Continued

[E, estimated; EPTC, s-ethyl dipropylthiocarbamate; <, less than; --, not detected]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/

day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

PropanilSimazine

 

Tebuthiuron

Terbacil

Trifluralin

1 05412500 Turkey River at Garber 03/15/04 1100 <0.011 <0.005 <0.02 <0.034 <0.009

04/20/04 0950 <.011 <.010 <.02 <.034 <.009

05/19/04 1200 <.011 .029 <.02 <.034 <.009

05/24/04 1100 <.011 .046 .04 <.034 <.009

06/10/04 1000 <.011 .042 <.02 <.034 <.009

07/21/04 1130 <.011 .010 <.02 <.034 <.009

08/17/04 1445 <.011 .011 <.02 <.034 <.009

09/14/04 1300 <.011 <.010 <.02 <.034 <.009

10/18/04 1030 <.011 E.004 <.02 <.034 <.009

11/16/04 0901 <.011 <.010 <.02 <.034 <.009

12/06/04 0955 <.011 <.005 <.02 <.034 <.009

2 05418600 Maquoketa River near Spragueville 03/15/04 1700 <.011 <.005 <.02 <.034 <.009

03/29/04 1500 <.011 .006 <.02 <.034 <.009

04/20/04 1510 <.011 <.005 <.02 <.034 <.009

05/19/04 0800 <.011 .050 <.02 <.034 <.009

05/25/04 1000 <.011 .046 .02 <.034 <.009

06/10/04 1300 <.011 .007 <.02 <.034 E.004

07/21/04 0720 <.011 <.010 <.02 <.034 <.009

08/17/04 1025 <.011 .008 <.02 <.034 <.009

09/14/04 1000 <.011 <.005 <.02 <.034 <.009

10/18/04 1330 <.011 <.005 <.02 <.034 <.009

11/17/04 0710 <.011 <.005 <.02 <.034 <.009

12/06/04 1340 <.011 <.005 <.02 <.034 <.009

3 05422000 Wapsipinicon River near DeWitt 03/17/04 0830 <.011 <.005 <.02 <.034 <.009

04/15/04 0830 <.011 .006 <.02 <.034 <.009

05/18/04 1200 <.011 .063 <.02 <.034 <.009

05/25/04 1400 <.011 .059 E.01 <.034 <.009

06/16/04 1230 <.011 .017 <.02 <.034 <.009

07/20/04 1200 <.011 <.010 <.02 <.034 <.009

Supplemental Information 1
Table 10. Concentrations of selected pesticides and pesticide degradation products determined by the U.S. Geological Survey 

National Water-Quality Laboratory, Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 rivers in 

Iowa, 2004. —Continued

[E, estimated; EPTC, s-ethyl dipropylthiocarbamate; <, less than; --, not detected]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/

day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

PropanilSimazine

 

Tebuthiuron

Terbacil

Trifluralin

3 05422000 Wapsipinicon River near DeWitt 08/17/04 0745 <0.011 0.008 <0.02 <0.034 <0.009

09/14/04 0730 <.011 <.010 <.02 <.034 <.009

10/18/04 1520 <.011 <.005 <.02 <.034 <.009

11/17/04 0845 <.011 <.005 <.02 <.034 <.009

12/06/04 1615 <.011 <.005 <.02 <.034 <.009

4 05474000 Skunk River at Augusta 03/17/04 1430 <.011 <.005 <.02 <.034 <.009

04/15/04 1345 <.011 .006 <.02 <.034 <.009

05/18/04 0730 <.011 .011 <.02 <.034 <.009

06/16/04 0900 <.011 .018 <.02 <.034 E.005

07/20/04 0800 <.011 <.010 <.02 <.034 <.009

08/16/04 1615 <.011 <.005 <.02 <.034 <.009

09/13/04 1530 <.011 .010 <.02 <.034 <.009

10/19/04 0845 <.011 E.004 <.02 <.034 <.009

11/17/04 1130 <.011 <.005 <.02 <.034 <.009

12/08/04 1150 <.011 <.005 <.02 <.034 <.009

5 05490500 Des Moines River at Keosauqua 03/18/04 1230 <.011 .022 <.02 <.034 <.009

04/22/04 0910 <.011 <.010 <.02 <.034 <.009

05/17/04 1400 <.011 .024 <.02 <.034 <.009

06/14/04 1400 <.011 .015 <.02 <.034 E.004

07/19/04 1600 <.011 .012 <.02 <.034 <.009

08/16/04 1330 <.011 .009 <.02 <.034 <.009

09/13/04 1330 <.011 .012 <.02 <.034 <.009

10/19/04 1100 <.011 <.005 <.02 <.034 <.009

11/17/04 1400 <.011 <.005 <.02 <.034 <.009

12/08/04 0900 <.011 <.005 <.02 <.034 <.009

6 06485500 Big Sioux River at Akron 03/09/04 1200 <.011 <.005 <.02 <.034 <.009

04/13/04 0930 <.011 <.005 <.02 <.034 <.009

05/12/04 1030 <.011 <.005 <.02 <.034 <.009

05/26/04 1300 <.011 .007 <.02 <.034 E.009

06/02/04 1215 <.011 .010 <.02 <.034 E.007
Table 10. Concentrations of selected pesticides and pesticide degradation products determined by the U.S. Geological Survey 

National Water-Quality Laboratory, Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 rivers in 

Iowa, 2004. —Continued

[E, estimated; EPTC, s-ethyl dipropylthiocarbamate; <, less than; --, not detected]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/

day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

PropanilSimazine

 

Tebuthiuron

Terbacil

Trifluralin

6 06485500 Big Sioux River at Akron 07/14/04 1030 <0.011 0.005 <0.02 <0.034 <0.009

08/11/04 0940 <.011 <.005 <.02 <.034 <.009

09/08/04 0730 <.011 <.005 <.02 <.034 <.009

09/17/04 1230 <.011 <.005 <.02 <.034 <.009

10/12/04 1600 <.011 <.005 <.02 <.034 <.009

11/18/04 1100 <.011 <.005 <.02 <.034 <.009

7 06607500 Little Sioux River near Turin 03/10/04 0830 <.011 <.005 <.02 <.034 <.009

04/13/04 1400 <.011 <.005 <.02 <.034 <.009

05/11/04 1020 <.011 .015 <.02 <.034 <.009

05/24/04 1100 <.011 .067 <.02 <.034 .021

06/08/04 0850 <.011 .018 E.01 <.034 <.009

06/17/04 1230 <.011 .040 <.02 <.034 .020

07/13/04 1000 <.011 .007 <.02 <.034 <.009

08/10/04 0900 <.011 <.005 <.02 <.034 <.009

09/08/04 1100 <.011 <.005 <.02 <.034 <.009

09/20/04 1145 <.011 <.005 <.02 <.034 <.009

10/12/04 1300 <.011 <.005 <.02 <.034 <.009

11/17/04 0945 <.011 <.005 <.02 <.034 <.009

8 06609500 Boyer River at Logan 03/12/04 0930 <.011 <.005 <.02 <.034 <.009

04/14/04 0730 <.011 <.005 <.02 <.034 <.009

05/11/04 1300 <.011 <.005 <.02 <.034 <.009

05/23/04 1015 <.011 .092 <.02 <.034 .015

06/08/04 1130 <.011 E.005 <.02 <.034 <.009

06/17/04 1000 <.011 .076 <.02 <.034 .016

07/13/04 1230 <.011 .149 <.02 <.034 <.009

08/10/04 1130 <.011 E.004 <.02 E.031 <.009

09/07/04 1530 <.011 <.005 <.02 <.034 <.009

10/12/04 1000 <.011 <.005 <.02 <.034 <.009

11/17/04 1230 <.011 <.005 <.02 <.034 <.009

Supplemental Information 
Table 10. Concentrations of selected pesticides and pesticide degradation products determined by the U.S. Geological Survey 

National Water-Quality Laboratory, Lakewood, Colorado, using laboratory schedule 2001 for water samples collected from 10 rivers in 

Iowa, 2004. —Continued

[E, estimated; EPTC, s-ethyl dipropylthiocarbamate; <, less than; --, not detected]

Map

number

(fig. 4)

U.S. Geological

Survey site

identification number

Site name

Date of

collection

(month/

day/

year)

Collection

time

(24-hour)

Concentrations, in micrograms per liter

PropanilSimazine

 

Tebuthiuron

Terbacil

Trifluralin

9 06810000 Nishnabotna River above Hamburg 03/11/04 1030 <0.011 <0.005 <0.02 <0.034 <0.009

03/29/04 1230 <.011 <.005 <.02 <.034 E.004

04/12/04 1300 <.011 <.005 <.02 <.034 <.009

05/10/04 1230 <.011 .098 <.02 <.034 .035

05/25/04 1045 <.011 .042 <.02 <.034 .034

06/07/04 1245 <.011 .006 <.02 <.034 <.009

07/12/04 1230 <.011 .009 <.02 <.034 <.009

08/09/04 1230 <.011 <.005 <.02 <.034 <.009

09/07/04 1230 <.011 .011 <.02 <.034 <.009

10/13/04 0800 <.011 <.005 <.02 <.034 <.009

11/16/04 1300 <.011 <.005 <.02 <.034 <.009

10 06904010 Chariton River near Moulton 03/18/04 0900 <.011 .043 <.02 <.034 <.009

04/22/04 1320 <.011 .031 <.02 <.034 <.009

05/17/04 1100 <.011 .037 E.01 <.034 <.009

06/14/04 1050 <.011 .041 <.02 <.034 <.009

07/19/04 1230 <.011 .035 <.02 <.034 <.009

08/16/04 1030 <.011 .033 <.02 <.034 <.009

09/13/04 1030 <.011 .032 <.02 <.034 <.009
Prepared by Lawrence Publishing Service Center.

Edited by Lanna Combs.

Graphics by Jeff Hartley and Mike Kemppainen.

Layout and design by Kristi Hartley.

For more information concerning the research described 

in this report, contact:

U.S. Geological Survey

4821 Quail Crest

Lawrence, KS 66049–3839

(785) 842–9909

http://ks.water.usgs.gov
Printed on recycled paper

Scribner and others—Occurrence of Isoxaflutole, Acetamide, and Triazine Herbicides and Their Degradation Products in 10 Iowa Rivers 

Draining to the Mississippi and Missouri Rivers, 2004—Scientific Investigations Report 2006–5169

0.001

0.010

0.10

1.0

Concentration, in micrograms per liter

Diketonitrile

Benzoic acid

Isoxaflutole

Diketonitrile

Benzoic acid

Isoxaflutole

Diketonitrile

Benzoic acid

Isoxaflutole

Compound and time interval

Preplanting

(March−April)

Postplanting

(May−June)

Late summer

(July−September)

Reporting limit

(0/21)(0/27)

(16/27)

(13/27)

(4/27)

(27/27)

(23/27)

(13/21)

(7/21)