1

Maximum fipronil concentrations in water ranged from 0.829 to 5.29 μg/L (micrograms per liter) 

during March through April, corresponding to the release of ricefield tailwater. 

Fipronil degradation products in water were detected from February through June 2000. Aerobic degradation products desulfinylfipronil and fipronil sulfone were detected at maximum concentrations in March and April, similarly to the parent compound. Maximum concentrations of 

the anaerobic degradation product fipronil sulfide were detected in June. 

Concentrations of fipronil and degradation products in suspended sediment ranged from 1 to 10 

percent of the concentrations in water. 

The parent compound fipronil is not accumulating in bed sediment. 

The anaerobic reduction degradation product fipronil sulfide was the predominant degradation 

product detected in bed sediment, and concentrations ranged from 0.636 to 24.8 μg/kg (micrograms per kilogram). The degradation products desulfinylfipronil and fipronil sulfone also were 

frequently detected in bed sediment. 

cially-produced crawfish populations in the 

Mermentau River Basin. Traditional rice-cultivation practices include releases of ricefield 

water in the spring months. The effects of 

ricefield drainage on receiving waters and 

biota are not well understood. 

This report presents a study of the analyses of fipronil and three of its degradation 

products in water, suspended sediment, and 

bed sediment. Samples were collected from 

17 sites in the rice-producing areas of the Mermentau River Basin from February to September 2000 collected as part of the U.S. 

Geological Survey National Water-Quality 

Assessment (NAWQA) Program. This insecticide and its degradation products--desulfinylfipronil, fipronil sulfide, and fipronil 

sulfone--were selected for discussion because 

little information currently exists on the occurrence and partitioning of this new insecticide 

in the environment.

The Mermentau River Basin has a drainage area of about 3,800 mi2

 (square miles) 

(Sloss, 1971). Land-surface elevations are less 

than 100 feet in most of the basin and range 

from 20 to 30 feet above the National Geodectic Vertical Datum of 1929 along the Mermentau River main stem (Garrison, 1997). 

Vegetation in the upper basin consists of mixed 

pine-hardwoods, but as the land flattens vegetation rapidly changes. The Mermentau River 

Basin in the mid-to-lower reaches is bordered 

by a cypress-water tupelo riparian zone that is 

typically flooded for a large part of the year. 

NATIONAL WATER-QUALITY ASSESSMENT PROGRAM

FIPRONIL AND DEGRADATION PRODUCTS IN THE RICE-PRODUCING 

AREAS OF THE MERMENTAU RIVER BASIN, LOUISIANA, FEBRUARYSEPTEMBER 2000

INTRODUCTION

The Mermentau River Basin is a unique 

agricultural area located in southwestern 

Louisiana. Historically, the area was a 

tallgrass prairie similar in many ways to the 

tallgrass prairie in the midwestern United 

States (Allain and others, 2000). The area 

also is called coastal prairie or wet prairie 

(Brown, 1972). The distinctive prairie characteristics of the basin are a result of an 

impermeable clay layer underlying the shallow soils. Five major tributaries divide the 

basin into a series of broad, flat areas ideal for 

agriculture. The areas are separated by bottomland hardwood riparian corridors that 

vary in width from only a hundred feet to several miles. Thus, the basin is characterized by 

a dendritic river system, low gradient, and a 

heavy clay soil. 

Most of the Mermentau River Basin has 

been altered for growing rice, sugarcane, forage, grain crops, crawfish production, and 

cattle grazing. Rice, however, is the most 

important agricultural crop produced in the 

basin. Crawfish farming also occurs in ricefields. The insecticide fipronil was licensed 

in 1996 (U.S. Environmental Protection 

Agency, 1996a), and the insecticide was 

widely used on rice seed to control the rice 

water weevil beginning in 1999. In the summer of 1999, public concern in Louisiana 

arose over the use of fipronil-coated rice seed 

and the apparent negative effects on commerThe banks generally are steep in the tributaries 

with cypress-water tupelo extending into the 

stream. Along the lower reaches, banks often 

are not discernible as the water extends into a 

bottomland hardwood flood plain. The flood 

plain may abruptly end as it meets a ricefield 

levee system or roadway. Water velocities are 

typically less than 1 ft/s (foot per second). 

Isolated flow reversals can occur in the tributaries and canals draining into the river during 

periods of heavy pumping for rice irrigation. 

The streambed substrate in the tributaries and 

main channel is silt and clay. The substrate in 

the loops of the main stem and smaller tributaries can also be a soft flocculent muck rich 

in organic matter. 

Total rice acreage in the seven parishes 

(Acadia, Allen, Evangeline, Jefferson Davis, 

Lafayette, St. Landry, and Vermilion) of the 

Mermentau River Basin was almost 400,000 

acres in 1998 and about 340,000 acres in 2000 

(Louisiana Cooperative Extension Service, 

1998, 2000). The primary cause of the 

decrease in rice acreage was a drought in 

south Louisiana which began in the spring of 

1999 and lasted well into the summer and fall 

of 2000. Rice cultivation in this basin utilizes 

both ground and surface water (fig. 1) (B.P. 

Sargent, U.S. Geological Survey, written commun., 2002). The decreased availability of 

fresh surface water during the drought in the 

southern part of the basin, especially Vermilion Parish, resulted in less rice planted in 2000 

than in 1998. 

Significant Findings

U.S. Department of the Interior USGS Fact Sheet FS-010-03

U.S. Geological Survey March 2003
 2

Aerial application of seed onto flooded 

fields is the predominant method of rice 

seeding in southwestern Louisiana. After 

aerial rice seeding, the water is retained for 

about 1 to 2 days and released. The field is 

allowed to drain only long enough for the 

young seedling to become anchored, about 

3 to 5 days. The field is then re-flooded until 

the rice nears maturity. Releases of ricefield 

water (called tailwater) into drainage ditches 

and streams result in high turbidities during 

March through May.

The flooding of fields also functions to 

suppress red rice, a wild variety with no commercial value (Linscombe and others, 1999), 

and to make ricefields easily adaptable for 

crawfish farming. Most crawfish farming 

occurs in ricefields, either double-cropped with 

rice or utilizing ricefields that are not in rice 

production that year. There are more than 

80,000 acres of farm-raised crawfish in southern Louisiana, including about 40,000 acres in 

the Mermentau River Basin in 2000. 

Study Design

Prior to the public concern about fipronil, 

an assessment of agricultural practices on 

stream quality and aquatic invertebrates in the 

Mermentau River Basin was designed as part 

of the NAWQA Program. The purpose of the 

assessment is to integrate surface- and groundwater-quality data with information about 

aquatic invertebrate community structure to 

gain a more complete understanding of the factors, both natural and human-induced, that 

affect water quality in the Mermentau River 

Basin. The community structure of aquatic 

invertebrates in this area is of interest because, 

in addition to their value as indicators of the 

overall health of the system, the ricefields of 

southwestern Louisiana are an internationally 

important stopover site for invertebrate-eating 

shorebirds during their spring migration. About 

3,200 mi2

 of the Mermentau Basin are assessed 

by NAWQA. Three major components of the 

assessment have been completed, as follows:

• 2000: Surface-water quality--Occurrence and 

distribution of major inorganic ions, nutrients, and pesticides in water; also fipronil 

and degradation products in water, suspended sediment, and bed sediment.

• 2000: Ground-water quality--Occurrence and 

distribution of major inorganic ions, nutrients, trace elements, and pesticides including 

fipronil and degradates in shallow ground 

water.

• 2001: Ecology and aquatic invertebrate community structure--Integration of chemical 

data with ecological data including aquatic 

invertebrates.

Site Selection

The sampling sites for the 2000 surfacewater-quality component of NAWQA (fig. 2) 

were selected to represent the water quality at 2 

or 3 locations from each major tributary: 

Bayou des Cannes, Bayou Nezpique, Bayou 

Lacassine, Bayou Plaquemine Brule, and 

Bayou Queue de Tortue (table 1). One site 

was located near the headwaters of each major 

tributary and 1 to 2 sites were located midreach or downstream. Two sites were located 

on the Mermentau River main stem: Mermentau at Mermentau and Mermentau at Lake 

Arthur. Mermentau at Mermentau is a longterm USGS water-quality site. Downstream 

from Mermentau at Lake Arthur, tidal effects 

and the Gulf Intracoastal Waterway greatly 

complicate data analysis and were excluded 

from this study of fipronil and three of its degradation products. The sites were sampled 

monthly February to June 2000. Bed sediment samples were collected from August 28 

to September 6, 2000.

Sample Collection and Laboratory 

Analysis

USGS personnel conducted extensive discussions with the following organizations 

before sampling for fipronil and its degradation products: Louisiana Department of Agriculture and Forestry, Louisiana State 

University Agriculture Center, including their 

Aquaculture Research Station and Rice 

Research Station, and Bayer CropScience, the 

manufacturers of fipronil.

Water column samples were collected 

according to methods described in Fishman 

and Friedman (1989) and Shelton (1994). In 

those streams where water velocities were less 

than 1.5 ft/s, a weighted bottle sampler was 

used to collect a depth-integrated sample. 

Samples were processed on site in a USGS 

mobile laboratory. For analysis of fipronil and 

degradation products on suspended sediment, 

the volume of water passing through a baked 

glass-fiber filter was measured, and the glassfiber filter was retained and frozen until 

analysis. Fipronil and degradation products 

were analyzed at the USGS National Water 

Quality Laboratory in Lakewood, Colorado. 

These compounds were not part of any 

standard USGS analyses prior to this study. 

Personnel at the USGS laboratory developed a 

custom method for these analyses in filtered 

water. This method was a modification of an 

approved analytical method (Zaugg and 

others, 1995). Bed sediment samples were 

collected using a Petite Ponar grab sampler. 

This sampler has a 6-by-6 inch collection area 

and penetrates about 4 inches into the bed 

sediments. Five bed-sediment samples were 

collected at each site, composited, and a 

subsample was placed in a baked glass bottle 

and shipped at 4 degrees Celsius to the 

laboratory. The sediment and suspendedsediment methods were custom modifications 

of a method for determinations of compounds 

Preparation for aerial-rice seeding in the Mer- in bed sediment (Furlong and others, 1996).

mentau River Basin.

Figure 1. Ground- and surface-water withdrawals in the Mermentau River Basin, Louisiana, 2000. (Data from: B.P. Sargent, U.S. 

Geological Survey, written commun., 2002.)
 3

Figure 2. Study area in the Mermentau River Basin,

Louisiana. (Modified from Garrison, 1997, p. 15.) log Kow of 4.01, which places it between 

highly insoluble pesticides such as DDT, 

which has a log Kow of 6.2, and highly soluble pesticides such as atrazine, which has a 

log Kow of 2.6 (U.S. Environmental Protection 

Agency, 1996b).

These chemical characteristics indicate 

that fipronil and its degradation products have 

differing mobilities and environmental fates. 

Therefore, to document the presence of these 

compounds in the environment it is necessary 

to analyze water, suspended sediment, and bed 

sediment. Ali and others (1998) reported that 

two species of chironomid (midge fly) larvae 

were highly susceptible to fipronil. Fifty percent of the test organisms died with 48 hours 

(LC 50) upon exposure to 0.42 μg/L.

The degradation products of fipronil also 

are toxic. Fipronil sulfone is 3.3 times more 

Table 2. Partitioning coefficients and fate of fipronil and three degradation products

Name Company 

code no.1

 Coefficient2

 Koc (ave.) log Kow Fate1

Fipronil MB 46030 803 4.01

Desulfinylfipronil MB 46513 1,290 Not available Photolysis in water or soil

Fipronil sulfide MB 45950 2,719 Not available Reduction in soil (anaerobic)

Fipronil sulfone MB 46136 4,209 Not available Oxidation in soil (aerobic)

1

Rhone-Poulenc (1996); 2Connelly (2001)

Bayou Lacassine near Welsh) and 5.19 μg/L 

on April 19, at site 9 (West Bayou Grand 

Marais near Roanoke). The maximum fipronil 

concentration detected at the main stem of the 

Mermentau River was 3.0 μg/L at site 10 

(Mermentau River at Mermentau). The maximum concentration of fipronil occurs at or 

slightly before the maximum concentrations 

of other ricefield pesticides such as molinate 

(Goree and others, 2000, 2001). 

 Water samples also were analyzed for 

three fipronil degradation products (table 3). 

The degradation product detected in the highest concentrations was desulfinylfipronil. Desulfinylfipronil is the result of aerobic 

photodegradation, so the fact that this degradation product was detected in the highest concentrations in the water column (1.13 μg/L at 

site 7; 0.651 μg/L at site 2), as compared to the 

other two degradation products, conforms to 

FIPRONIL AND DEGRADATION 

PRODUCTS

Fipronil, 5-amino-1-[2,6 dichloro-4-(trifluromethyl)phenyl]-4-[(1R,S)-(trifluromethyl)sulfinyl]-1H-pyrazole-3-carbonitrile, was 

discovered in 1987 and first registered as a 

pesticide in the United States in 1996. 

Fipronil is a phenylpyrazole insecticide which 

functions by targeting the gamma-aminobutyric acid (GABA) receptor system of insects 

(Kidd and James, 1991), interfering with chloride transport through the membranes of neurons. At sufficient doses, fipronil causes 

neural excitation, paralysis, and insect death 

(Bobe and others, 1998).

 As organic compounds, pesticides have 

an affinity for the natural organic matter 

present in soils or water (Barbash and Resek, 

1996). This affinity can be expressed by 

reporting a coefficient K indicating the compound’s organic carbon partitioning coefficient 

(Koc) or octanol/water partitioning coefficient 

(Kow). The larger the Koc, the greater the affinity of the compound to bind to soil particles, 

resulting in lower mobility through the soil. 

Based on the Koc data (table 2), fipronil and 

desulfinylfipronil are expected to display lowto-moderate mobility, and fipronil sulfide and 

fipronil sulfone a low mobility (Connelly, 

2001). The fipronil parent compound has a 

toxic to native bluegill sunfish than the 

parent compound. Fipronil sulfone is 

6.6 times more toxic, and fipronil sulfide is 1.9 times more toxic to freshwater invertebrates than the parent 

compound (U.S. Environmental Protection Agency, 1996a).

McClain (2001) has shown that 

juvenile crawfish may be susceptible 

to the initial ricefield release water 

when fipronil-treated seed is applied 

following typical planting practices, 

and that water temperature and turbidity also may play a role in increased 

toxicity of fipronil to crawfish.

Fipronil in Surface Water

Concentrations of fipronil and 

three selected degradation products 

are listed in table 3. The maximum 

concentrations of the parent compound occurred in late March through 

mid-April. The maximum concentrations detected in this study were from 

the headwaters of small bayous surrounded by rice agriculture, such as 

5.29 μg/L on March 23, at site 8 (East 

.

Site 

number

(fig. 2)

Site name

1 Bayou Nezpique near Basile

2 Bayou Nezpique at Guidry Road near Basile

3 Bayou des Cannes near Eunice

4 Bayou Mallet near Eunice

5 Bayou Nezpique near Panchoville

6 Bayou des Cannes near Iota

7 Bayou Plaquemine Brule near Church Point

8 East Bayou Lacassine near Welsh

9 West Bayou Grand Marais near Roanoke

10 Mermentau River at Mermentau

11 Bayou Plaquemine Brule at Estherwood

12 Bayou Wikoff near Rayne

13 Bayou Chene near Thornwell

14 Bayou Lacassine near Lake Arthur

15 Mermentau River at Lake Arthur

16 Bayou Queue de Tortue at Riceville

17 Bayou Queue de Tortue near Lelieux

Table 1. Sampling sites for fipronil and degradation products, Mermentau River Basin, Louisiana
 4

Table 3. Concentrations of fipronil and three degradation products in water, Mermentau River Basin, Louisiana, 2000

 [Concentrations are in micrograms per liter; <, less than the method detection level; E, estimated; --, not analyzed]

Sample

(month-day) Fipronil Desulfinylfipronil

Fipronil 

sulfide

Fipronil 

sulfone

Bayou Nezpique near Basile (site1)

2-22 <0.0044 -- -- 0.0062

3-21 1.29 0.151 0.054 .065

4-18 .593 .158 .109 .052

5-30 .028 .063 .148 .03

6-27 .009 .036 .087 .022

Bayou Nezpique at Guidry Road near Basile (site 2)

2-22 <.0044 -- -- .012

 3-21 3.94 .651 .067 .015

4-18 1.7 .242 .109 .089

5-30 .297 .082 .127 .049

6-27 .012 .059 .12 .037

Bayou des Cannes near Eunice (site 3)

2-22 .005 -- -- .014

3- 9 .0044 -- -- .012

4- 5 .799 .166 .045 .05

4-18 2.69 .593 .124 .163

5-10 .088 .102 .076 .039

6-21 .014 .046 .058 .03

6-27 .016 .061 .081 .04

Bayou Mallet near Eunice (site 4)

2-22 <.0044 -- -- .005

4-18 .829 .13 .043 .044

5-30 .298 .282 .043 .027

6-27 <.0044 .018 .022 .008

Bayou Nezpique near Panchoville (site 5)

2-23 <.0044 -- -- .012

4-19 3.24 .36 .149 .143

5-31 .083 .079 .172 .05

6-28 .03 .071 .186 .05

Bayou des Cannes near Iota (site 6)

2-23 .005 -- -- .013

3-22 2.69 .416 .071 .116

4-19 2.26 .413 .137 .126

5-31 .104 .171 .214 .07

6-28 .013 .071 .119 .038

Bayou Plaquemine Brule near Church Point (site 7)

2-22 <.0044 -- -- <.005

3-21 1.59 1.13 .034 .126

4-18 .128 .036 .018 .011

5-30 <.0044E .005E .008 .004

6-27 <.0044E .004E .007 .004

East Bayou Lacassine near Welsh (site 8)

2-24 <.0044 -- -- .019

3-23 5.29E .2 .046 .132

4-19 4.54 .4 .171 .205

5-31 .09 .082 .163 .079

6-28 .024 .041 .1 .046

West Bayou Grand Marais near Roanoke (site 9)

2-23 .007 -- -- .017

3-22 1.28 .12 .043 .066

4-19 5.19E .425 .128 .202

5-31 .047 .066 .145 .057

6-28 .017 .033 .097 .037

 Sample

 (month-day) Fipronil Desulfinylfipronil

Fipronil 

sulfide

Fipronil 

sulfone

Mermentau River at Mermentau (site 10)

2-23 0.006 -- -- 0.015

3- 8 <.0044 -- -- .013

3-23 .193 0.037 0.03 .018

4- 4 3.00 .51 .103 .163

4-19 1.02 .207 .071 .064

5- 9 .188 .068 .059 .038

5-31 .188 .101 .083 .044

6-20 .109 .109 .122 .052

6-28 .06 .086 .115 .052

Bayou Plaquemine Brule at Estherwood (site 11)

2-23 <.0044 -- -- .013

3-22 3.04 .566 .085 .195

4-20 2.47 .541 .105 .144

6- 1 .243 .157 .129 .062

6-28 .019 .049 .066 .034

Bayou Wikoff near Rayne (site 12)

2-23 <.0044 -- -- .004

3-21 .106 .091 .026 .018

4-19 1.07 .482 .044 .09

6- 1 .008 .038 .027 .015

6-27 <.0044E .009 .012 .006

Bayou Chene near Thornwell (site 13)

2-24 <.0044 -- -- .012

3-23 1.44 .09 .045 .066

4-20 2.6 .284 .122 .124

5-31 .086 .092 .107 .043

6-28 .047 .115 .169 .058

Bayou Lacassine near Lake Arthur (site 14)

2-24 <.0044 -- -- .01

3-23 <.0044 .024 .011 .008

4- 4 1.94 .226 .077 .081

4-20 1.04 .219 .08 .068

5- 9 .176 .059 .048 .029

6- 1 .092 .073 .066 .029

6-20 .056 .094 .075 .033

6-28 .052 .121 .085 .042

Mermentau River at Lake Arthur (site 15)

2-24 <.0044 -- -- .016

3-23 .09 .034 .028 .016

4-20 .915 .195 .064 .06

6- 1 .161 .112 .08 .046

6-29 .077 .1 .113 .053

Bayou Queue de Tortue at Riceville (site 16)

2-24 <.0044 -- -- .01

3-23 1.64 .305 .037 .064

4-20 3.23 .534 .167 .194

6- 1 .282 .158 .14 .063

6-29 .016 .052 .084 .039

Bayou Queue de Tortue near Lelieux (site 17)

2-25 <.0044 -- -- .009

3-24 4.07 .47 .069 .16

6- 1 .807 .236 .184 .11

6-28 .007 .03 .062 .024
 5

the expected chemical behavior of the compounds in the environment. Interestingly, the 

highest desulfinylfipronil concentrations were 

detected at the same time as the highest 

fipronil concentrations at 14 of the 17 sites, 

and in the same months at 16 of the 17 sites 

(fig. 3). This indicates that the photolytic 

decomposition pathway is rapid.

The highest detected concentration of 

fipronil sulfide was 0.214 μg/L at site 6. The 

maximum concentration of fipronil sulfide 

tended to lag behind the maximum concentrations of the parent compound and the other 

two selected degradation products (fig. 3). 

This is consistent with the known degradation process, as fipronil sulfide is a reduction 

product most frequently detected in soils 

(U.S. Environmental Protection Agency, 

1996a; Connelly, 2001). 

The aerobic degradation product fipronil 

sufone had a similar detection pattern to the 

desulfinyl degradation product and the parent 

compound, with maximum concentrations 

occurring in March and April. The highest 

concentrations were 0.202 μg/L at site 9 and 

0.205 μg/L at site 8. These are both wadable 

streams less than 20 feet in width. Aerobic 

degradation is more likely at these sites than 

in wider, deeper Mermentau Basin streams in 

which low dissolved oxygen concentrations 

are more common. Fipronil sulfone was the 

only degradation product analyzed in the 

February samples. Fipronil sulfone was 

detected at very low concentrations, about 

0.01 μg/L, at 16 of the 17 sites in February, 

whereas the parent compound was detected 

only four times: 0.005 μg/L at site 3, 

0.005 μg/L at site 6, 0.007 μg/L at site 9, and 

0.006 μg/L at site 10. These concentrations 

were just above the minimum detection level 

of 0.0044 μg/L. The fipronil sulfone 

detected in February could be degradation 

products of fipronil application from the previous year, when fipronil was used on rice for 

the first time commercially. 

Degradation product concentrations 

began to equal or exceed the parent compound in the May samples. In the June samples, only fipronil sulfone was detected in 

concentrations less than the parent compound at the downstream sites 10, 14, and 15.

Fipronil in Suspended Sediment

Fipronil and three degradation products 

in suspended sediment were determined from 

monthly samples at site 8, East Bayou 

Lacassine near Welsh, March-June and at site 

14, Bayou Lacassine near Lake Arthur, 

March-May (fig. 4). Suspended-sediment 

concentrations of fipronil and degradation 

products range from 1 to 10 percent of the 

concentrations in water. Degradation product concentrations at site 8 exceeded the parent concentration by May, exhibiting the 

same general relation of parent 

compound to degradation 

products seen in the water column.

Fipronil in Bed Sediment

Fipronil in bed sediment 

(fig. 5) shows an interesting 

pattern. The parent compound 

was not detected in the 17 samples collected from August 28 

to September 6, 2000. However, two degradation products, fipronil sulfide and 

desulfinylfipronil were 

detected at all 17 sites. The reduction product, 

fipronil sulfide, had the highest range of concentrations from 0.636 to 24.8 μg/kg (micrograms per kilogram). The photolysis product 

desulfinylfipronil concentrations ranged from 

0.55 to 7.01 μg/kg. Fipronil sulfone was 

detected at 16 of the 17 sites and ranged from 

not detected to 10.5 μg/kg. Fipronil sulfone is 

an aerobic soil-oxidation product (U.S. Environmental Protection Agency, 1996a) and 

would be expected to occur in bed sediment. 

The concentrations of the three degradation products in bed sediment also show a general increase downstream on all the streams, 

with the exception of Bayou Nezpique. The 

highest concentrations of all three degradation 

products were detected in bed sediment from 

the main stem of the Mermentau River at the 

two most downstream sites in the basin. In 

contrast, fipronil parent and degradation product concentrations in water at these sites generally were among the lowest during the 

February-June 2000 sampling.

Figure 3. Occurrence of maximum concentrations of

fipronil and three degradation products at 17 sites, MarchJune 2000.

Figure 4. Fipronil and degradation products in suspended sediment, March-June 2000.

1

0.1

0.01

0.001

0.0001

1

0.1

0.01

0.001

0.0001

Fipronil

Desulfinylfipronil

Fipronil sulfide

Fipronil sulfone

Not detected

CONCENTRATION IN SUSPENDED SEDIMENT, IN MICROGRAMS 

PER LITER

East Bayou Lacassine near Welsh (site 8)

Bayou Lacassine near Lake Arthur (site 14)

DATE

Fipronil

Desulfinylfipronil

Fipronil sulfide

Fipronil sulfone

Not detected

13

11

9

7

5

3

1

0

Fipronil

Desulfinylfipronil

Fipronil sulfide

Fipronil sulfone

NUMBER OF SITES

DATE
 6

Rhone-Poulenc, 1996, Fipronil: Research Triangle Park, N.C., World Wide Technical Bulletin, 

21 p.

Shelton, L.R., 1994, Field guide for collecting 

and processing stream-water samples for the 

National Water-Quality Assessment Program: 

U.S. Geological Survey Open-File Report 94-

0445, 42 p.

Sloss, Raymond, 1971, Drainage area of Louisiana streams: Louisiana Department of Public 

Works Basic Records Report no. 6, 117 p.

U.S. Environmental Protection Agency, 1996a, 

New pesticide Fact Sheet: Washington, D.C., 

U.S. EPA Office of Prevention, Pesticides and 

Toxic Substances, EPA 737-F-96-005, 10 p.

-----1996b, Partition coefficient (N-octanol/water) 

estimation by liquid chromatography: U.S. EPA 

Office of Prevention, Pesticides, and Toxics 

Substances, accessed October 15, 2002, at URL 

http://www.epa.gov/docs/OPPTS_Harmonized/

830_Product_Properties_Test_Guidelines/

Series/830-7570.pdf

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

Fehlberg, K.M., 1995, Methods of analysis by 

the U.S. Geological Survey National Water 

Quality Laboratory--Determination of pesticides in water by C-18 solid-phase extraction 

and capillary-column gas chromatography/

mass spectrometry with selected-ion monitoring: U.S. Geological Survey Open-File Report 

95-181, 60 p.

By Dennis K. Demcheck and 

 Stanley C. Skrobialowski

For additional information, contact:

District Chief

U.S. Geological Survey

3535 S. Sherwood Forest Blvd., Suite 120

Baton Rouge, LA 70816

Telephone: (225) 298-5481

Fax: (225) 298-5490

Home pages: http://water.usgs.gov/nawqa http://la.water.usgs.gov

ACKNOWLEDGMENTS

The authors wish to thank Bayer CropScience for providing additional reference standards of fipronil degradation products and 

James Madsen and Michael Schroeder of the 

USGS National Water Quality Laboratory for 

their work in the development of the custom 

method for the analysis of fipronil and degradation products.

REFERENCES

Ali, A., Nayar, J.K., and Gu, W.D., 1998, Toxicity 

of a phenyl pyrazole insecticide, fipronil, to 

mosquito and chironomid midge larvae in the 

laboratory: Journal of the American Mosquito 

Control Association, v. 14, no. 2, p. 216-218.

Allain, Larry, Vidrine, Malcolm, Grafe, Vicki, 

Allen, Charles, and Johnson, Steve, 2000, Paradise lost? The coastal prairie of Louisiana and 

Texas: U.S. Fish and Wildlife Service, 39 p.

Barbash, J.E., and Resek, E.A., 1996, Pesticides in 

ground water, Distribution, trends, and governing factors: Volume two of the series Pesticides 

in the Hydrologic System: Ann Arbor Press, 

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Figure 5. Fipronil degradation products in bed sediments, Mermentau River Basin, Louisiana, August 28-September 6, 2000.

Any use of trade, product, or firm names in this report is for

descriptive purposes only and does not imply endorsement by the

U.S. Government.