U.S. Department of the Interior

U.S. Geological Survey

Data Series 667

Dissolved Pesticides, Dissolved Organic Carbon, and 

Water-Quality Characteristics in Selected Idaho 

Streams, April–December 2010

Dissolved Pesticides, Dissolved Organic 

Carbon, and Water-Quality Characteristics 

in Selected Idaho Streams, 

April–December 2010

By Timothy J. Reilly, Kelly L. Smalling, Emma R. Wilson, and William A. Battaglin

Data Series 667

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012

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Suggested citation:

Reilly, T.J., Smalling, K.L., Wilson, E.R., and Battaglin, W.A., 2012, Dissolved pesticides, dissolved organic carbon, 

and water-quality characteristics in selected Idaho streams, April–December 2010: U.S. Geological Survey 

Data Series 667, 17 p.
iii

Acknowledgments

The authors thank Alexandra Etheridge, Kristi Jones, Megan McWayne Holmes, James 

Orlando, Corey Sanders, and Ryan Todd of the U.S. Geological Survey (USGS) for their many 

hours of field, laboratory, and database work. The authors would also like to thank Lance 

Steele, Prasanna Kandel, Alison Chamberlin, and Korrine Wade from the Boise State University, Department of Biological Sciences, for their assistance collecting water samples. This 

project was funded by the USGS Toxic Substances Hydrology Program and a grant from the 

National Science Foundation (award number DEB-0918182) to Dr. Merlin White at Boise State 

University, Department of Biological Sciences, Boise, Idaho.

Contents

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

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

Purpose and Scope ..............................................................................................................................2

Description of Sampling Sites and Watershed Characteristics ...................................................2

Methods of Study...........................................................................................................................................4

Watershed Delineation and Land-Use Characterization ..............................................................4

Sampling Methods................................................................................................................................4

Analysis of Dissolved Pesticides .......................................................................................................4

Instrument Calibration ................................................................................................................7

Quality Assurance/Quality Control............................................................................................7

Method Detection Limits ............................................................................................................7

Analysis of Dissolved Organic Carbon..............................................................................................7

Dissolved Pesticides in Streams.................................................................................................................7

Dissolved Organic Carbon and Water-Quality Characteristics in Streams.......................................13

Summary........................................................................................................................................................16

References Cited..........................................................................................................................................16
iv

Figures

1. Map showing location of four surface-water sampling sites and associated 

watersheds in Idaho.....................................................................................................................3

2. Maps showing crop and land-cover types for (A) Sand Run Gulch at Highway 95 

crossing near Parma (USGS station number 13210360) and (B) Ditch near 

Wanstad Road near Parma (USGS station number 13213008) in Idaho ..............................5

3. Maps showing crop and land-cover types for sampling sites (A) Cottonwood 

Creek near Boise (USGS station number 433711116110700) and (B) Dry Creek near 

Bogus Basin Road near Boise (USGS station number 434006116112100) in Idaho ...........6

Tables

1. Description of four surface-water sampling sites and associated watershed 

characteristics in Idaho...............................................................................................................2

2. Dissolved pesticides with types, method detection limits, and instrumental 

limits of detection .........................................................................................................................8

3. Dissolved pesticide concentrations measured in surface-water samples collected 

from sampling sites on four streams in Idaho, April–December 2010 ...............................10

4. Dissolved pesticides with type; detection frequency; and median, minimum, and 

maximum concentrations measured in surface-water samples collected from 

Sand Run Gulch at Highway 95 crossing near Parma, Idaho (USGS station number 

13210360) and Ditch near Wanstad Road near Parma, Idaho (USGS station number 

13213008), in Idaho, April–December, 2010. ...........................................................................13

5. Dissolved organic carbon concentrations and water-quality characteristics 

measured in surface-water samples collected from four streams in Idaho, 

April–December 2010.................................................................................................................14
v

Conversion Factors

SI to Inch/Pound

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

millimeter (mm) 0.03937 inch (in.)

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

Area

square kilometer (km2) 0.3861 square mile (mi2)

Volume

liter (L) 1.057 quart (qt)

liter (L) 0.2642 gallon (gal)

Mass

gram (g) 0.03527 ounce, avoirdupois (oz)

kilogram (kg) 2.205 pound, avoirdupois (lb)

microgram (μg) 3.527 x 10-8 ounce, avoirdupois (oz)

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

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

°F=(1.8×°C)+32

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88). 

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

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius 

(μS/cm at 25°C).

Concentrations of chemical constituents in water are given in milligrams per liter (mg/L), 

micrograms per liter (μg/L), or nanograms per liter (ng/L).
vi

Unit Abbreviations

°C Degrees Celsius

°C/min Degrees Celsius per minute

cm3 cubic centimeters

dd decimal degrees

g gram

L liter

m meter

mg milligrams

mg/L milligrams per liter

min minute

mL milliliter

mm millimeter

ng/L nanograms per liter

ng/μL nanograms per microliter

NTU Nephelometric turbidity unit

 μg/kg micrograms per kilogram

μL microliter

μm micrometer

μS/cm microsiemens per centimeter at 25 degrees Celsius

Acronyms

DCM dichloromethane

DOC dissolved organic carbon

GC-EIMS gas chromatograph/election ionization mass spectrometer

GC-ITMS gas chromatograph/ion trap mass spectrometer

GF/F glass fiber filter

H2SO4 sulfuric acid

i.d. inner diameter

KHP potassium hydrogen phthalate

LOD limit of detection

MDL method detection limit

N2 nitrogen gas

Na2SO4 sodium sulfate
vii

ND not detected

NWIS National Water-Quality Information System

QA/QC quality assurance/quality control

SPE solid-phase extraction

SD standard deviation

SIM selective ion monitoring

SIS selective ion storage

USDA U.S. Department of Agriculture 

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

Abstract

Water-quality samples were collected from April 

through December 2010 from four streams in Idaho and 

analyzed for a suite of pesticides, including fungicides, by 

the U.S. Geological Survey. Water samples were collected 

from two agricultural and two nonagricultural (control) 

streams approximately biweekly from the beginning of the 

growing season (April) through the end of the calendar year 

(December). Samples were analyzed for 90 pesticides using 

gas chromatography/mass spectrometry. Twenty-three pesticides, including 8 fungicides, 10 herbicides, 3 insecticides, 

and 2 pesticide degradates, were detected in 45 water samples. 

The most frequently detected compounds in the two agricultural streams and their detection frequencies were metolachlor, 

96 percent; azoxystrobin, 79 percent; boscalid, 79 percent; 

atrazine, 46 percent; pendimethalin, 33 percent; and trifluralin, 

33 percent. Dissolved-pesticide concentrations ranged from 

below instrumental limits of detection (0.5–1.0 nanograms per 

liter) to 771 nanograms per liter (hexazinone). The total number of pesticides detected in any given water sample ranged 

from 0 to 11. Only three pesticides (atrazine, fipronil, and 

simazine) were detected in samples from the control streams 

during the sampling period.

Introduction

Fungicides are used to prevent the outbreak of persistent, 

historically significant plant diseases like late blight (caused 

by Phytophthora infestans and responsible for the Irish Potato 

Famine of 1846) and newer plant diseases, such as Asian 

Soy Rust. Both late blight and Asian Soy Rust are potentially 

devastating if not controlled (Leadbeater and Gisi, 2009).

Of the more than 67,000 pesticide products currently registered for use in the United States, more than 3,600 are used 

to combat fungal diseases (U.S. Environmental Protection 

1

U.S. Geological Survey

2

Boise State University

Agency, 2011).Even with the use of chemical-based cropprotection measures, fungal pathogens were responsible for 7 

to 24 percent of losses in yields to commodity crops, such as 

potatoes, worldwide during 2001–03 (Oercke, 2006). Pesticide 

manufacturers are continually developing new fungicides to 

find more effective treatments and to outpace the rate at which 

pathogens acquire resistance to these chemicals. For example, 

Phytophthora infestans rapidly developed strains resistant to 

widely used phenylamide fungicides, leading to its classification as a high-risk pathogen and necessitating co-application 

of other fungicides to provide the necessary crop protection 

(Brent and Hollomon, 2007). Depending on the pathogen 

genome and the mode of fungicidal action (single versus 

multiple pathways), pathogens can develop resistance to 

newly introduced fungicides within a few years of exposure. 

For example, field and laboratory studies identified Alternaria 

alernata strains (responsible for Alternaria late blight of pistachio crops) resistant to boscalid within 2 years of registration 

and to azoxystrobin within 3 to 4 years of continuous application (Ma and Others, 2003; Avenot and Michailides, 2007).

Relatively little is known about the fate and effects of 

fungicides at environmentally relevant concentrations in 

the aquatic environment. Recent studies have documented 

the presence of some fungicides in runoff from greenhouse 

production and commercial foliage plant nurseries (Roseth 

and Haarstad, 2010; Wilson and Riiska, 2010), soil and water 

associated with banana production (Geissen and others, 2010), 

streams and bed sediment (Battaglin and others, 2010; Smalling and Orlando, 2011), and the atmosphere (Schummer and 

others, 2010). Even less is known about the presence in the 

environment of recently registered fungicides. For example, 

the presence of boscalid (first registered for use in the United 

States in 2003) has been documented in only four studies; it 

has been found in streams and groundwater (Smalling and 

Orlando, 2011; Reilly and others, in press) using field experiments to determine soil dissipation and residuals (Chen and 

Zhang, 2010), and in the atmosphere (Schummer and others, 

2010).

The potential for chronic exposure of nontarget fungi 

to fungicides at environmentally relevant concentrations 

exists but has not been extensively evaluated. Unlike most 

other pesticides, multiple fungicides typically are applied as 

Dissolved Pesticides, Dissolved Organic Carbon, and 

Water-Quality Characteristics in Selected Idaho Streams, 

April–December 2010

By Timothy J. Reilly1, Kelly L. Smalling1, Emma R. Wilson2, and William A. Battaglin1
2 Pesticides, Dissolved Organic Carbon, and Water-Quality Characteristics in Selected Idaho Streams, April–December 2010

a prophylactic crop protectant more than 10 times per season 

(depending on conditions and crop type) but at lower application rates than herbicides or insecticides. This difference in 

usage increases the likelihood of chronic exposure of aquatic 

ecosystems to low concentrations of fungicides. The effects 

of fungicides at environmentally relevant concentrations on 

aquatic organisms and communities are poorly understood. 

However, recent studies have documented the potential effects 

of fungicides on amphibians and macroinvertebrate communities (Schäfer and others, 2011; Belden and others, 2010).The 

genotoxic, teratogenic, and endocrine-disrupting properties of 

several fungicides have been established by field, mesocosm, 

in vivo (zebrafish and human lymphocytes), and in vitro studies (Bony and others, 2008; Şişman and Türkez, 2010; Orton 

and others, 2011; Taxvig and others, 2008).

Aside from studies conducted by manufacturers during 

the registration process, data on the effects of fungicides on 

aquatic organisms and nontarget fungi are limited. Environmental concentrations of fungicides are typically less than 100 

nanograms per liter (ng/L) (Battaglin and others, 2010; Smalling and Orlando, 2011). On the basis of current literature, the 

effect on aquatic communities of fungicides at these concentration levels is likely to be sublethal or an indirect disruption 

of community structure by altering fungal, phytoplankton, 

and zooplankton populations. Nondisease (nontarget) fungi 

are known to be sensitive to antifungal substances (including 

fungicides), and changes to their community structure could 

affect key food-web dynamics, as well as critical nutrient and 

carbon-cycling pathways (Barron, 2003; Gleason and Marano, 

2010).

A study was conducted by the U.S. Geological Survey 

(USGS) Toxic Substances Hydrology (Toxics) Program to 

measure water-quality characteristics and the concentrations 

of currently used pesticides (especially fungicides) and dissolved organic carbon in selected streams in Idaho. In 2010, 

field sampling focused on two streams with agriculture in the 

surrounding areas and with unknown insect and gut fungi 

populations and two streams with little, if any, agriculture 

and that contain populations of insects with robust gut fungi 

populations. Water-quality results from this study can be used 

to focus future efforts of the USGS Toxics Program and other 

researchers to better understand the effects of pesticides (particularly fungicides) on native fungi and the insects that they 

inhabit. 

Purpose and Scope

This report describes the methods and procedures used 

to determine pesticide concentrations in 45 water samples collected from 4 stream sites in Idaho in April to December 2010. 

Water samples were analyzed for a suite of 90 pesticides; 

concentrations of 23 pesticides are listed in a table. Concentrations of dissolved organic carbon and values of water-quality 

characteristics are also presented.

Description of Sampling Sites and Watershed 

Characteristics

Two of the four streams selected for this study drain 

agricultural land (hereafter referred to as agricultural 

streams)—Sand Run Gulch @ Hwy 95 Xing nr Parma ID (station 13210360) and Ditch nr Wanstad Rd nr Parma ID (station 

13213008)—and two streams (hereafter referred to as control 

streams) drain nonagricultural land. The two streams that drain 

nonagricultural land—Cottonwood Creek nr Boise, ID (station 433711116110700) and Dry Creek nr Bogus Basin Rd nr 

Boise, ID (station 434006116112100)—contain insect larvae 

(including black flies) with robust populations of gut fungi. 

Sampling locations are shown in figure 1, and watershed characteristics are listed in table 1.

Table 1. Description of four surface-water sampling sites and associated watershed characteristics in Idaho. 

[Horizontal datum is North American Datum of 1983. Dominant crops and percentage of watershed in agriculture from U.S. Department of Agriculture 

(2011). NA, not applicable; <, less than]

USGS station 

number USGS station name Latitude Longitude

Watershed 

area 

(acres)

Percentage 

of watershed 

in agriculture

Dominant crops 

(Percentage of 

agricultural 

acreage)

13210360 Sand Run Gulch at Highway 95 

crossing near Parma, ID 43.764 -116.912 50,877 37.1 Alfalfa (25.0), corn (15.9), winter wheat (14.3)

13213008 Ditch near Wanstad Road 

near Parma, ID 43.803 -116.957 760 90.5 Winter wheat (27.5), hay (18.1), corn (17.7)

433711116110700 Cottonwood Creek near Boise, ID 43.620 -116.185 10,613 0.1 NA

434006116112100 Dry Creek near Bogus Basin Road 

near Boise, ID 43.668 -116.189 6,171 <0.1 NA
Introduction 3

CANYON

ADA

IDAHO

433711116110700

434006116112100

13210360

13213008

116°30'

43°30'

117°

44°

116°

116°

116°30'

117°

43°30'

EXPLANATION

Watershed boundary

State boundary

County boundary

Stream

Surface-water sampling 

site and identifier 433711116110700

0 5 10 MILES

0 5 10 KILOMETERS

Figure 1. Location of four surface-water sampling sites and associated watersheds in Idaho.
4 Pesticides, Dissolved Organic Carbon, and Water-Quality Characteristics in Selected Idaho Streams, April–December 2010

Methods of Study

Watershed Delineation and Land-Use 

Characterization 

Watersheds were delineated using ArcGIS Desktop GIS 

software (ESRI, Redlands, California). Initial watershed 

boundaries were taken from a preexisting dataset of national 

watershed boundaries (Natural Resources Conservation 

Service, 2009). The boundaries were then modified to match 

specific sampling sites by digitizing the boundaries on-screen 

using high-resolution aerial photographs, digital topographic 

maps, and detailed hydrography as a backdrop. The 2010 

Idaho cropland data layer (U.S. Department of Agriculture, 

2011; figs. 2 and 3) was used to calculate the crop statistics 

shown in table 1. This data layer has a spatial resolution of 

approximately 30 meters (m). In most cases the land-use 

categories shown represent several defined classifications in 

the cropland data layer. For example, the forest category in the 

figures is composed of deciduous forest, evergreen forest, and 

forest land categories from the cropland data layer. 

Sampling Methods

Twelve water samples were collected from each of the 

agricultural streams, and 10 and 11 samples were collected 

from Dry Creek and Cottonwood Creek, respectively. Samples 

were collected approximately biweekly starting in April for the 

two agricultural streams and Cottonwood Creek and starting 

in June for Dry Creek. The period of sample collection spans 

the typical growing season in Idaho. Sample collection did not 

target runoff events or other specific hydrologic conditions.

Water-quality sampling was conducted following the 

same procedures at all sites. Samples were collected by 

immersing pre-cleaned, amber glass bottles—1 liter (L) for 

pesticides and 125 milliliters (mL) for dissolved organic 

carbon (DOC)—once at each site to a depth of not less than 

0.1 m below the water surface. A 1-L polyurethane bottle was 

rinsed three times with streamwater, then filled for determination of basic water-quality characteristics (specific conductance in microseimens per centimeter at 25 degrees Celsius 

(μS/cm), pH in standard units, and turbidity in nepholometric 

turbidity units (NTU)). At the time of sample collection, water 

temperature was measured with an alcohol-filled thermometer. 

Samples were then packed on ice and shipped overnight to the 

USGS Organic Chemistry Laboratory in Sacramento, California, for extraction and analysis.

Analysis of Dissolved Pesticides

All water samples were filtered in the laboratory using 

0.7-micrometer (μm) glass fiber filters (GF/F) (Whatman, 

Florham Park, New Jersey) to remove suspended material. Filtered water samples were analyzed for a suite of 90 

pesticides by extracting 1 L of sample water onto OasisTM 

hydrophilic-lipophilic-balanced (HLB) solid-phase extraction 

(SPE) cartridges (6 cubic centimeters (cm3), 500 milligrams 

(mg), 60 μm; Waters Corporation, Milford, Massachusetts). 

All samples were spiked with ring-13C3-atrazine and diazinondiethyl-d10 (Cambridge Isotopes, Andover, Massachusetts) as 

recovery surrogates prior to cartridge extraction. Following 

extraction, the SPE cartridges were dried with carbon dioxide, 

eluted with 12 mL of ethyl acetate, and reduced under nitrogen. After extraction, approximately 1 gram (g) of sodium 

sulfate (Na2SO4) was added to the sample bottles to remove 

any residual water, and the bottles were rinsed three times 

with dichloromethane (DCM). The bottle rinses were reduced 

to 1 mL under nitrogen and combined with the ethyl acetate 

fraction. The entire sample (bottle rinse plus SPE eluate) was 

reduced to a final volume of 200 μL (microliters) for analysis. 

Acenaphthene-d10 and pyrene-d10 (used as internal standards) 

were added to all samples prior to instrumental analysis. All 

sample extracts were analyzed for herbicides and insecticides 

by gas chromatography/mass spectrometry. Additional details 

are given in Hladik and others (2008).

Water-sample extracts (1-μL injection volume) were 

analyzed for herbicides and insecticides using a Varian Saturn 

2000 (Walnut Creek, California) gas chromatograph (GC)–ion 

trap mass spectrometer (ITMS). Analyte separation on the 

GC was achieved using a 30 m x 0.25 millimeter (mm) inner 

diameter (i.d.), 0.25-mm DB-5ms fused silica column (Agilent 

Technologies, Folsom, California) with helium as the carrier 

gas. The temperature of the splitless injector was held constant 

at 275 degrees Celsius (°C). The temperature program was 

80oC (hold 0.5 minute (min)), increase to 120oC at 10oC/min, 

increase to 200oC at 3oC/min (hold 5 min), increase to 219oC 

at 3oC/min, and finally increase to 300oC at 10oC/min (hold 

10 min). The transfer line and ion trap temperatures were 

280oC and 220oC, respectively. The ITMS was operated in 

electron ionization (EI) mode with an emission current of 15 

microamperes (μA) and no offset when run in full-scan mode, 

and an emission current of 45 μA with a multiplier offset of 

300 volts when using selective ion storage (SIS) windows. 

Data were collected in full scan and SIS modes. Complete 

details of the analytical method are described in Hladik and 

others (2008) and Smalling and Orlando (2011).

Sample extracts were analyzed for fungicides using 

an Agilent 5975 GC/electron ionization mass spectrometer 

(EIMS) (Folsom, California). Analyte separation was achieved 

using a 30-m x 0.25-mm i.d., 0.25-mm DB-5ms fused silica 

column (Agilent Technologies, Folsom, Calif.) with helium as 

the carrier gas. The temperature of the splitless injector was 

held constant at 275oC. The temperature program was 80oC 

(hold 0.5 min), increase to 180oC at 10oC/min, increase to 

220oC at 5oC/min (hold 1 min), increase to 280oC at 4oC/min 

(hold 1 min), and finally increase to 300oC at 10oC/min (hold 

10 min). The transfer-line, quadrupole, and source temperatures were 280oC, 150oC, and 230oC, respectively. Data for all 

fungicides were collected in selective ion monitoring (SIM) 

mode with each compound having one quantifier ion and one 

or two qualifier ions.
Methods of Study 5

Figure 2. Crop and land-cover types for (A) Sand Run Gulch at Highway 95 crossing near Parma (USGS station number 13210360) and 

(B) Ditch near Wanstad Road near Parma (USGS station number 13213008) in Idaho.

A. 13210360 - Sand Run Gulch at Highway 95 crossing near Parma

B. 13213008 - Ditch near Wanstad Road near Parma

0 2 4 MILES

0 2 4 KILOMETERS

0

0

2,000 FEET

500 METERS

2010 Crop types and 

land cover

Potatoes

Corn

Wheat

Other grains

Other crops

Orchards

Pasture/hay

Forest

Shrub/grassland

Wetlands

Developed land

Water

Stream

Surface-water 

sampling site

EXPLANATION
6 Pesticides, Dissolved Organic Carbon, and Water-Quality Characteristics in Selected Idaho Streams, April–December 2010

Figure 3. Crop and land-cover types for sampling sites (A) Cottonwood Creek near Boise (USGS station number 433711116110700) and 

(B) Dry Creek near Bogus Basin Road near Boise (USGS station number 434006116112100) in Idaho.

A. 433711116110700 - Cottonwood Creek near Boise

B. 434006116112100 - Dry Creek near Bogus Basin Road near Boise

0 0.5 1 MILE

0 0.5 1 KILOMETER

0 0.5 1 MILE

0 0.5 1 KILOMETER

2010 Crop types and 

land cover

Potatoes

Corn

Wheat

Other grains

Other crops

Orchards

Pasture/hay

Forest

Shrub/grassland

Wetlands

Developed land

Water

Stream

Surface-water 

sampling site

EXPLANATION
Dissolved Pesticides in Streams 7

Instrument Calibration

Calibration of both instruments (GC-ITMS and GCEIMS) was achieved using calibration standards that spanned 

the linear range of instrument response. An eight-point calibration standard was developed with concentrations ranging from 

0.025 to 5.0 nanograms per microliter (ng/μL). Calibration 

curves were considered acceptable if the R2 for each individual 

compound was greater than 0.995. The response of the instruments was monitored every six to eight samples with midlevel check standards. The instruments were considered to be 

stable if recovery of the check standards fell within the range 

of 80 to 115 percent of the nominal standard concentration. 

If environmental sample concentrations fell outside the linear 

range of the instrument, the samples were diluted appropriately and reanalyzed.

Quality Assurance/Quality Control

Dissolved-pesticide concentrations in water were 

validated against a comprehensive set of performance-based 

quality assurance/quality control (QA/QC) criteria, including 

laboratory blanks, matrix spikes, and surrogate recovery. All 

environmental and QC data were reviewed by project staff, 

and results for the target constituents analyzed under the same 

conditions were of acceptable quality.

Eight laboratory blanks (tap water) were processed to 

test the cleanliness of laboratory procedures. No pesticides 

were detected in any of the blank samples. Ring-13C3-atrazine 

and diazinon-diethyl-d10 were used as recovery surrogates to 

assess the efficiency of sample extraction. Sample data were 

excluded if recovery was less than 70 percent. Recovery of 

surrogates for all samples analyzed (including QC samples) 

ranged from 73 to 118 percent with a mean (± standard deviation) for ring-13C3

-atrazine and diazinon-diethyl-d10 of 89 ± 9 

percent and 93 ± 12 percent, respectively. Six samples were 

spiked in the laboratory with a suite of 90 pesticides, and the 

percent recovery ranged from 78 to 110 percent with a median 

of 92 percent. This test measured the efficiency of the extraction method, as well as the stability and holding times of all 

compounds during transport to the laboratory.

Method Detection Limits

Surface-water method detection limits (MDLs) were 

validated using the U.S. Environmental Protection Agency 

(USEPA) procedure described in 40 CFR Part 136 (U.S. 

Environmental Protection Agency, 1992). Water samples 

used to determine MDLs for insecticides and herbicides were 

collected in 2005 from the Sacramento River at Miller Park 

(Hladik and others, 2008), and water samples for fungicide 

MDLs were collected in 2008 from the American River near 

the California State University Campus. The MDLs were calculated for each compound using the following equation:

MDL = S x t (n-1, 1-α = 0.99) , (1)

where

MDL = method detection limit, in nanograms per 

liter;

S = standard deviation of replicate samples;

n = number of replicates; and

t = value of Student’s t statistic at 6 degrees of 

freedom and 99-percent confidence level.

MDLs for all compounds in water ranged from 0.9 to 

10.5 ng/L, and instrumental limits of detection (LOD) ranged 

from 0.5 to 1.0 ng/L (table 2). Analytes detected at concentrations greater than the instrumental LOD but less than the MDL 

are reported as estimates. 

Analysis of Dissolved Organic Carbon

All water samples were filtered in the laboratory using 

0.7-μm GF/Fs (Whatman, Florham Park, New Jersey.) to 

remove suspended material. Filtered water samples were 

analyzed for dissolved organic carbon (DOC) by high-temperature catalytic combustion using a Shimadzu TOC-VCNS

total organic carbon analyzer (Shimadzu Scientific Instruments, Columbia, Maryland) according to a modified version 

of USEPA method 415.3 (Potter and Wimsatt, 2009). The 

instrument was calibrated using potassium hydrogen phthalate 

(KHP) standards prepared in organic-free water with concentrations ranging from 0.0 to 4.0 milligrams per liter (mg/L). 

All standards, blanks, and samples were acidified prior to 

analysis with approximately four drops of concentrated sulfuric acid (H2

SO4) to lower the pH to less than 2.0. The accuracy 

and precision of the measurements were within 5 percent, as 

indicated by internal standards (KHP and caffeine), laboratory 

replicates, and matrix spikes (Bird and others, 2003; Potter 

and Wimsatt, 2009). The quantitative limit of detection for 

DOC was 0.3 mg/L.

Dissolved Pesticides in Streams

Twenty-three pesticides or pesticide degradates were 

detected in 45 water samples collected from four streams in 

Idaho (table 3). Maximum pesticide concentrations ranged 

from less than the instrumental limit of detection to 771 ng/L 

(for hexazinone). The maximum number of pesticides detected 

in a single water sample was 11. Twenty-three pesticides, 

including 8 fungicides, 10 herbicides, 3 insecticides, and 2 

pesticide degradates, were detected in 24 water samples from 

the agricultural streams. The most frequently detected compounds and the detection frequencies in the two agricultural 

streams are metolachlor, 96 percent; azoxystrobin, 79 percent; 

boscalid, 79 percent; atrazine, 46 percent; pendimethalin, 33 

percent; and trifluralin, 33 percent (table 4). 
8 Pesticides, Dissolved Organic Carbon, and Water-Quality Characteristics in Selected Idaho Streams, April–December 2010

Table 2. Dissolved pesticides with types, method detection limits, and instrumental limits of detection.—Continued 

[D, degradate; H, herbicide; I, insecticide; F, fungicide; S, synergist; ng/L, nanograms per liter]

Compound Pesticide type Method detection limit 

(ng/L)

Instrumenal limit of detection 

(ng/L)

3,4-Dichloroaniline (3,4 DCA) D 8.3 1.0

3,5-Dichloroaniline (3,5 DCA) D 7.6 1.0

Alachlor H 1.7 1.0

Allethrin I 6.0 1.0

Atrazine H 2.3 0.5

Azoxystrobin F 3.1 0.5

Bifenthrin I 4.7 0.5

Boscalid F 2.8 0.5

Butylate H 1.8 1.0

Carbaryl I 6.5 1.0

Carbofuran I 3.1 1.0

Chlorothalonil F 4.1 0.5

Chlorpyrifos I 2.1 0.5

Clomazone H 2.5 1.0

Cycloate H 1.1 1.0

Cyfluthrin I 5.2 1.0

Cypermethrin I 5.6 1.0

Cyproconazole F 4.7 0.5

Cyprodinil F 7.4 1.0

DCPA (Dacthal) H 2.0 0.5

Deltamethrin I 3.5 1.0

Diazinon I 0.9 1.0

Difenoconazole F 10.5 1.0

(E)-Dimethomorph F 6.0 1.0

EPTC (Eptam) H 1.5 0.5

Esfenvalerate I 3.9 0.5

Ethalfluralin H 3.0 0.5

Etofenprox I 2.2 1.0

Famoxadone F 2.5 1.0

Fenarimol F 6.5 1.0

Fenbuconazole F 5.2 1.0

Fenhexamid F 7.6 1.0

Fenpropathrin I 4.1 1.0

Fipronil I 2.9 0.5

Desulfinylfipronil D 1.6 0.5

Fipronil sulfide D 1.8 0.5

Fipronil sulfone D 3.5 0.5

Fluazinam F 4.4 1.0

Fludioxonil F 7.3 1.0

Fluoxastrobin F 4.2 1.0

Flusilazole F 5.1 1.0

Flutriafol F 4.5 1.0

Hexazinone H 8.4 1.0

Imazalil F 10.5 1.0

Iprodione F 4.4 1.0
Dissolved Pesticides in Streams 9

Table 2. Dissolved pesticides with types, method detection limits, and instrumental limits of detection.—Continued 

[D, degradate; H, herbicide; I, insecticide; F, fungicide; S, synergist; ng/L, nanograms per liter]

Compound Pesticide type Method detection limit 

(ng/L)

Instrumenal limit of detection 

(ng/L)

Kresoxim-methyl F 4.0 1.0

Lambda-Cyhalothrin I 2.0 0.5

Malathion I 3.7 1.0

Metconazole F 5.2 0.5

Methidathion I 7.2 1.0

Methoprene I 6.4 1.0

Methyl parathion I 3.4 1.0

Metolachlor H 1.5 1.0

Molinate H 3.2 1.0

Myclobutanil F 6.0 0.5

Napropamide H 8.2 1.0

Oxyfluorfen H 3.1 1.0

p,p' DDD D 4.1 0.5

p,p' DDE D 3.6 0.5

p,p' DDT I 4.0 0.5

Pebulate H 2.3 0.5

Pendimethalin H 2.3 0.5

Pentachloroanisole (PCA) D 4.7 0.5

Pentachloronitrobenzene (PCNB) F 3.1 0.5

Permethrin I 3.4 0.5

Phenothrin (Sumithrin) I 5.1 1.0

Phosmet I 4.4 1.0

Piperonyl Butoxide S 2.3 1.0

Prometon H 2.5 1.0

Prometryn H 1.8 1.0

Propanil H 10.1 1.0

Propiconazole F 5.0 0.5

Propyzamide H 5.0 1.0

Pyraclostrobin F 2.9 0.5

Pyrimethanil F 4.1 0.5

Resmethrin I 5.7 1.0

Simazine H 5.0 1.0

Tebuconazole F 3.7 0.5

Tefluthrin I 4.2 1.0

Tetraconazole F 5.6 0.5

Tetramethrin I 2.9 1.0

Tau-Fluvalinate I 5.3 1.0

Thiobencarb H 1.9 0.5

Triadimefon F 8.9 1.0

Triadimenol F 8.0 1.0

Trifloxystrobin F 4.7 0.5

Triflumizole F 6.1 1.0

Trifluralin H 2.1 0.5

Triticonazole F 6.9 1.0

Zoxamide F 3.5 1.0
10 Pesticides, Dissolved Organic Carbon, and Water-Quality Characteristics in Selected Idaho Streams, April–December 2010

Table 3. Dissolved pesticide concentrations measured in surface-water samples collected from sampling sites on four streams in 

Idaho, April–December 2010. 

[Values are in nanograms per liter. Values in parenthesis ( ) are below method detection limits but above instrumental limits of detection and are estimates. The 

following compounds were analyzed but were not detected in any samples; 3,4-DCA, allethrin, bifenthrin, butylate, carbaryl, carbofuran, cycloate, cyfluthrin, 

cyhlothrin, cypermethrin, cyproconazole, cyprodinil, DCPA, deltamethrin, difenoconazole, dimethomorph, esfenvalerate, etofenprox, famoxadone, fenarimol, 

fenbuconazole, fenhexamide, fenpropathrin, fipronil desulfynil, fipronil sulfide, fipronil sulfone, fluazinam, fludioxinil, fluoxastrobin, flusilazole, flutriafol, 

iprodione, kresoxim-methyl, malathion, metconazole, methidathion, methoprene, methyl parathion, molinate, myclobutanil, napropamide, oxyfluorfen, 

p,p'-DDE, p,p'-DDT, PCA, PCNB, pebulate, permethrin, phenothrin, phosmet, piperonyl butoxide, prometon, prometryn, propanil, propyzamide, pyraclostrobin, resmethrin, tau-fluvalinate, tebuconazole, tefluthrin, tetramethrin, thiobencarb, triadimefon, triadimenol, trifloxystrobin, triticonazole and zoxamide. 

USGS, U.S. Geological Survey; ND, not detected]

USGS station 

number

USGS station 

name

Date Time 3,5-DCA Alachlor Atrazine Azoxystrobin Boscalid

13213008

Ditch near Wantad 

Road near 

Parma, ID

4/13/2010 1400 8.84 ND ND 3.37 36.6

5/3/2010 1530 ND 14.1 4.65 4.04 13.3

5/24/2010 1345 ND ND ND 4.20 7.00

6/16/2010 1145 ND ND 15.2 3.37 15.6

7/6/2010 1340 ND ND ND 9.23 20.9

7/26/2010 950 ND ND ND 31.0 11.6

8/16/2010 1115 ND ND ND 40.4 21.0

9/9/2010 1135 ND ND ND 3.43 11.7

9/29/2010 907 ND ND 5.00 ND ND

10/18/2010 1130 ND ND ND (3.0) 4.60

11/8/2010 1050 ND ND 2.60 3.60 9.40

11/29/2010 950 ND ND 3.40 (2.2) 5.20

13210360

Sand Run Gulch 

at Highway 95 

crossing near 

Parma, ID

4/13/2010 1430 ND ND 9.60 (1.8) 8.20

5/3/2010 1320 ND ND 5.80 (2.2) 10.2

5/24/2010 1430 ND ND ND (1.4) 4.42

6/16/2010 1145 ND ND 28.1 ND ND

7/6/2010 1340 ND ND 7.51 6.29 10.8

7/26/2010 950 ND ND ND 11.4 16.0

8/16/2010 1200 ND ND ND 20.2 37.8

9/9/2010 1135 ND ND 4.31 12.5 14.9

9/29/2010 930 ND ND ND ND ND

10/18/2010 945 ND ND ND (2.6) 5.41

11/8/2010 920 ND ND ND ND ND

11/29/2010 1100 ND ND 6.60 ND ND

433711116110700 Cottonwood Creek 

near Boise, ID

4/21/2010 1525 ND ND ND ND ND

5/13/2010 1100 ND ND ND ND ND

6/2/2010 1300 ND ND ND ND ND

6/22/2010 1300 ND ND ND ND ND

7/12/2010 1200 ND ND ND ND ND

8/2/2010 930 ND ND ND ND ND

8/23/2010 900 ND ND ND ND ND

9/15/2010 940 ND ND ND ND ND

10/4/2010 1230 ND ND ND ND ND

11/12/2010 1230 ND ND ND ND ND

12/6/2010 1330 ND ND ND ND ND

434006116112100

Dry Creek near 

Bogus Basin 

Road near 

Boise, ID

6/2/2010 945 ND ND ND ND ND

6/22/2010 1300 ND ND ND ND ND

7/12/2010 1200 ND ND ND ND ND

8/2/2010 930 ND ND ND ND ND

8/23/2010 900 ND ND 21.4 ND ND

9/15/2010 940 ND ND ND ND ND

10/4/2010 1430 ND ND ND ND ND

10/25/2010 845 ND ND ND ND ND

11/12/2010 1030 ND ND ND ND ND

12/6/2010 950 ND ND ND ND ND
Dissolved Pesticides in Streams 11

Table 3. Dissolved pesticide concentrations measured in surface-water samples collected from sampling sites on four streams in 

Idaho, April–December 2010.—Continued 

[Values are in nanograms per liter. Values in parenthesis ( ) are below method detection limits but above instrumental limits of detection and are estimates. The 

following compounds were analyzed but were not detected in any samples; 3,4-DCA, allethrin, bifenthrin, butylate, carbaryl, carbofuran, cycloate, cyfluthrin, 

cyhlothrin, cypermethrin, cyproconazole, cyprodinil, DCPA, deltamethrin, difenoconazole, dimethomorph, esfenvalerate, etofenprox, famoxadone, fenarimol, 

fenbuconazole, fenhexamide, fenpropathrin, fipronil desulfynil, fipronil sulfide, fipronil sulfone, fluazinam, fludioxinil, fluoxastrobin, flusilazole, flutriafol, 

iprodione, kresoxim-methyl, malathion, metconazole, methidathion, methoprene, methyl parathion, molinate, myclobutanil, napropamide, oxyfluorfen, 

p,p'-DDE, p,p'-DDT, PCA, PCNB, pebulate, permethrin, phenothrin, phosmet, piperonyl butoxide, prometon, prometryn, propanil, propyzamide, pyraclostrobin, resmethrin, tau-fluvalinate, tebuconazole, tefluthrin, tetramethrin, thiobencarb, triadimefon, triadimenol, trifloxystrobin, triticonazole and zoxamide. 

USGS, U.S. Geological Survey; ND, not detected]

USGS station 

number

Chlorothalonil Chlorpyrifos Clomazone Diazinon EPTC Ethalfluralin Fipronil Hexazinone Imazalil

13213008

ND ND ND ND ND ND ND ND 176

ND ND ND ND ND 13.5 ND 66.9 ND

ND 5.00 ND 10.6 25.2 14.4 ND 46.2 ND

(3.6) ND 35.8 ND 21.1 ND ND ND ND

ND ND ND ND ND 5.49 ND ND ND

ND ND ND ND ND 5.71 ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

13210360

ND ND ND ND ND ND ND 771 205

ND ND ND ND ND 9.0 ND 96.6 ND

ND ND ND ND 23.3 ND ND 137 ND

ND ND ND ND 22.9 ND ND ND ND

ND ND ND ND 9.54 5.89 ND 16.9 ND

ND ND ND ND ND 3.20 ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

433711116110700

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND 14.4 ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

434006116112100

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND
12 Pesticides, Dissolved Organic Carbon, and Water-Quality Characteristics in Selected Idaho Streams, April–December 2010

Table 3. Dissolved pesticide concentrations measured in surface-water samples collected from sampling sites on four streams in 

Idaho, April–December 2010.—Continued 

[Values are in nanograms per liter. Values in parenthesis ( ) are below method detection limits but above instrumental limits of detection and are estimates. The 

following compounds were analyzed but were not detected in any samples; 3,4-DCA, allethrin, bifenthrin, butylate, carbaryl, carbofuran, cycloate, cyfluthrin, 

cyhlothrin, cypermethrin, cyproconazole, cyprodinil, DCPA, deltamethrin, difenoconazole, dimethomorph, esfenvalerate, etofenprox, famoxadone, fenarimol, 

fenbuconazole, fenhexamide, fenpropathrin, fipronil desulfynil, fipronil sulfide, fipronil sulfone, fluazinam, fludioxinil, fluoxastrobin, flusilazole, flutriafol, 

iprodione, kresoxim-methyl, malathion, metconazole, methidathion, methoprene, methyl parathion, molinate, myclobutanil, napropamide, oxyfluorfen, 

p,p'-DDE, p,p'-DDT, PCA, PCNB, pebulate, permethrin, phenothrin, phosmet, piperonyl butoxide, prometon, prometryn, propanil, propyzamide, pyraclostrobin, resmethrin, tau-fluvalinate, tebuconazole, tefluthrin, tetramethrin, thiobencarb, triadimefon, triadimenol, trifloxystrobin, triticonazole and zoxamide. 

USGS, U.S. Geological Survey; ND, not detected]

USGS station 

number Metolachlor p,p’-DDD Pendimethalin

Propiconazole Pyrimethanil Simazine Tetraconazole Trifluralin Triflumizole

13213008

28.8 ND ND ND ND ND ND (1.9) ND

259 17.0 51.3 ND ND 13.9 ND ND ND

114 ND 154 ND ND 15.6 ND 2.2 ND

113 ND 47.4 ND ND ND ND 5.5 ND

566 ND 31.9 ND ND ND ND 40.9 ND

84.1 ND ND ND ND ND ND 3.9 ND

321 ND ND ND ND ND ND 5.2 ND

71.3 ND ND ND ND ND ND ND ND

40.4 ND ND ND ND ND ND ND ND

36.4 ND ND ND ND ND ND ND 68.8

37.0 ND ND ND ND ND ND ND ND

20.4 ND ND ND ND ND ND ND ND

13210360

21.6 ND ND ND ND 10.6 ND ND ND

122 ND 34.2 ND ND ND ND ND ND

66.9 ND 28.5 ND ND ND ND ND ND

171 ND 38.9 ND ND ND ND ND ND

137 ND 45.9 ND ND ND ND (1.2) ND

78.4 ND ND ND ND ND ND (2.0) ND

16.2 ND ND ND ND ND ND ND ND

19.6 ND ND ND ND ND ND ND ND

11.0 ND ND ND ND ND ND ND ND

ND ND ND (4.8) 5.2 ND (4.8) ND 150

5.40 ND ND ND ND ND ND ND ND

2.80 ND ND ND ND ND ND ND ND

433711116110700

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

434006116112100

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND 142 ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND

ND ND ND ND ND ND ND ND ND
Dissolved Organic Carbon and Water-Quality Characteristics in Streams 13

Dissolved Organic Carbon and WaterQuality Characteristics in Streams

Dissolved organic carbon (DOC) concentrations in 

samples collected during this study ranged from 1.65 to 

4.32 mg/L. Results of the analysis of DOC and water-quality 

characteristics (temperature, specific conductance, and turbidity) for each sampling event are shown in table 5. 

Table 4. Dissolved pesticides with type; detection frequency; and median, minimum, and maximum concentrations measured in 

surface-water samples collected from Sand Run Gulch at Highway 95 crossing near Parma, Idaho (USGS station number 13210360) 

and Ditch near Wanstad Road near Parma, Idaho (USGS station number 13213008), in Idaho, April–December, 2010.

[Values are in nanograms per liter. Values in parentheses ( ) are below method detection limits but above instrumental limits of detection and are estimates. 

ND, not detected]

Dissolved pesticide Pesticide type Detection frequency 

(in percent)

Concentration 

Median Minimum Maximum

Metolachlor Herbicide 96 66.9 2.80 566

Azoxystrobin Fungicide 79 3.60 (1.4) 40.4

Boscalid Fungicide 79 11.6 4.42 37.8

Atrazine Herbicide 46 5.80 2.60 28.1

Pendimethalin Herbicide 33 42.4 28.5 154

Trifluralin Herbicide 33 3.04 (1.2) 40.9

Ethalfluralin Herbicide 29 5.89 3.20 14.4

Hexazinone Herbicide 25 81.7 16.9 771

EPTC Herbicide 21 22.9 9.54 25.2

Simazine Herbicide 13 13.9 10.6 15.6

Imazalil Fungicide 8 191 176 205

Triflumizole Fungicide 8 109 68.80 150

3,5-DCA Degradate 4 8.84 8.84 8.84

Alachlor Herbicide 4 14.1 14.1 14.1

Chlorothalonil Fungicide 4 (3.6) (3.6) (3.6)

Chlorpyrifos Insecticide 4 5.0 5.0 5.0

Clomazone Herbicide 4 35.8 35.8 35.8

Diazinon Insecticide 4 10.6 10.6 10.6

p,p'-DDD Degradate 4 17.0 17.0 17.0

Propiconazole Fungicide 4 (4.8) (4.8) (4.8)

Pyrimethanil Fungicide 4 5.19 5.19 5.19

Tetraconazole Fungicide 4 (4.8) (4.8) (4.8)

Fipronil Insecticide 4 14.4 14.4 14.4
14 Pesticides, Dissolved Organic Carbon, and Water-Quality Characteristics in Selected Idaho Streams, April–December 2010

Table 5. Dissolved organic carbon concentrations and water-quality characteristics measured in surface-water samples collected 

from four streams in Idaho, April–December 2010.—Continued

[USGS, U.S. Geological Survey; DOC, dissolved organic carbon; mg/L, milligrams per liter; °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 

degrees Celsius; NTU, nephelometric turbidity units; --, no data]

USGS station 

number

USGS station 

name

Date Time DOC 

(mg/L)

Water 

temperature 

(°C)

Specific 

conductance 

(μS/cm)

Turbidity 

(NTU)

13213008 Ditch near Wanstad Road 

near Parma, ID

4/13/2010 1400 2.52 -- 695 44.7

5/3/2010 1530 3.19 12.0 323 88.1

5/24/2010 1345 3.37 13.5 237 50.1

6/16/2010 1145 2.68 14.5 250 75.1

7/6/2010 1340 3.10 17.0 292 87.1

7/26/2010 950 3.06 -- 464 66.0

8/16/2010 1115 3.91 18.0 443 32.6

9/9/2010 1135 2.97 16.0 300 71.8

9/29/2010 907 2.76 18.0 370 14.5

10/18/2010 1130 4.23 -- 540 24.0

11/8/2010 1050 1.9 -- 951 4.7

11/29/2010 950 1.65 8.0 947 0.5

13210360 Sand Run Gulch at Highway 

95 crossing near Parma, ID

4/13/2010 1430 2.69 11.5 854 28.4

5/3/2010 1320 3.13 11.0 465 12.4

5/24/2010 1430 3.51 13.5 370 17.6

6/16/2010 1145 3.40 15.0 405 28.2

7/6/2010 1340 3.69 16.0 420 44.9

7/26/2010 950 3.79 19.0 289 134.0

8/16/2010 1200 3.22 18.0 307 91.0

9/9/2010 1135 3.47 16.0 451 11.5

9/29/2010 930 2.98 16.0 494 15.7

10/18/2010 945 2.01 -- 614 108.0

11/8/2010 920 2.67 9.5 669 7.8

11/29/2010 1100 2.78 4.0 713 61.3
Dissolved Organic Carbon and Water-Quality Characteristics in Streams 15

Table 5. Dissolved organic carbon concentrations and water-quality characteristics measured in surface-water samples collected 

from four streams in Idaho, April–December 2010.—Continued

[USGS, U.S. Geological Survey; DOC, dissolved organic carbon; mg/L, milligrams per liter; °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 

degrees Celsius; NTU, nephelometric turbidity units; --, no data]

USGS station 

number

USGS station 

name

Date Time DOC 

(mg/L)

Water 

temperature 

(°C)

Specific 

conductance 

(μS/cm)

Turbidity 

(NTU)

433711116110700 Cottonwood Creek 

near Boise, ID

4/21/2010 1525 3.71 -- 121 16.7

5/13/2010 1100 2.78 8 169 5.8

6/2/2010 1300 3.93 11 136 12.3

6/22/2010 1300 2.82 -- 132 5.0

7/12/2010 1200 3.05 14 211 5.6

8/2/2010 930 2.97 12 339 12.4

8/23/2010 900 2.87 12.7 350 10.2

9/15/2010 940 2.98 15 378 1.1

10/4/2010 1230 3.07 13 -- --

11/12/2010 1230 3.26 6 401 0.6

12/6/2010 1330 4.32 7 374 0.6

434006116112100 Dry Creek near Bogus 

Basin Road near Boise, ID

6/2/2010 945 3.91 8.4 112 9.4

6/22/2010 1300 3.00 -- 120 5.0

7/12/2010 1200 2.61 13 141 5.3

8/2/2010 930 2.35 16 152 5.0

8/23/2010 900 2.58 13.3 155 4.2

9/15/2010 940 2.06 12 168 2.4

10/4/2010 1430 2.36 14 -- --

10/25/2010 845 3.91 7 166 2.5

11/12/2010 1030 1.67 2.5 167 1.1

12/6/2010 950 2.61 2 161 0.3
16 Pesticides, Dissolved Organic Carbon, and Water-Quality Characteristics in Selected Idaho Streams, April–December 2010

Summary

The U.S. Geological Survey, as part of the Toxic Substances Hydrology Program, conducted a study to measure 

the concentrations of currently used pesticides (especially 

fungicides) in two agricultural streams known from a previous 

study to contain fungicides and two control streams draining nonagricultural areas in Idaho. Dissolved organic carbon 

concentrations and water-quality characteristics also were 

measured.

Water samples were collected from the four streams 

from April through December 2010 and analyzed for a suite 

of pesticides (including fungicides). Twenty-three pesticides, 

including 8 fungicides, 10 herbicides, 3 insecticides, and 

2 pesticide degradates, were detected in 45 water samples. 

The most frequently detected compounds and the detection 

frequencies in the two agricultural streams are metolachlor, 

96 percent; azoxystrobin, 79 percent; boscalid, 79 percent; 

atrazine, 46 percent; pendimethalin, 33 percent; and trifluralin, 

33 percent. Concentrations of dissolved pesticides ranged from 

below instrumental limits of detection (0.5–1.0 nanograms per 

liter (ng/L)) to 771 ng/L (for hexazinone). Three pesticides 

(atrazine, fipronil, and simazine) were each detected once in 

the samples from the control streams.

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For additional information, write to:

Director

U.S. Geological Survey

New Jersey Water Science Center

Mountain View Office Park

810 Bear Tavern Rd., Suite 206

West Trenton, NJ 08628

or visit our Web site at:

http://nj.usgs.gov/
Reilly and others—Pesticides, Dissolved Organic Carbon, and Water-Quality Characteristics in Selected Idaho Streams, April–December 2010—Data Series 667

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