Scientific Investigations Report 2006-5005

Scientific Investigations Report 2006-5005

Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04

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Surface-water samples were collected from four irrigation return-flow drainage basins and analyzed for pesticides and pesticide metabolites, major ions, trace elements, and nutrients (table 3). The pesticides were selected by the NAWQA program (Gilliom and others, 1995) from a list of about 400 pesticides most commonly used in the United States (Gianessi and Puffer, 1991, 1992a, 1992b). Each pesticide was selected on the basis of the following factors: a national use of more than 8,000 lb of active ingredient annually; inclusion in the analytical schedules of other Federal monitoring or survey programs; toxicity; leachability; and its ability to be trapped and extracted from the appropriate solid-phase-concentrating matrix. Samples for analysis of pesticides and major ions were collected and submitted to the USGS National Water Quality Laboratory (NWQL) in Lakewood, Colo., the samples for pesticides were analyzed using either gas-chromatography/mass spectrometry (GC/MS) or high-performance liquid chromatography/mass spectrometry (HPLC/MS), depending on the physical characteristics of the target analytes. Samples for nutrient analysis were sent to the Bureau of Reclamation laboratory in Boise, Idaho.

Field Methods

The sampling site in each drainage basin was visited 10 times during the irritation season and 2 times during the non-irrigation season from July 2002 to October 2004. During each visit, water temperature, pH, dissolved oxygen (DO) concentrations, and specific conductance were measured and water samples were collected for analysis of pesticides, major ions, trace elements, and nutrients. The first sample from Sand Hollow drainage basin was collected from the bridge at S Road SW and all subsequent samples were collected from the mouth of Sand Hollow before it empties into the Columbia River. One DO measurement was removed from the data set because of a faulty sensor. Samples representative of flow in the stream cross section were obtained by collecting depth-integrated subsamples at equally spaced verticals across the stream using a US DH-81 sampler as described by Edwards and Glysson (1999) and Wilde and others (1999a). The sampler holds a 1- or 3-L Teflon® bottle, and all parts of the sampler coming in contact with the water sample are made of Teflon®. Subsamples were composited and split using a Teflon® churn splitter (Wilde and others, 2004). From June through August 2002, the Teflon® churn was not available, so a polyethylene churn splitter was used. Subsamples for analysis of inorganic analytes were collected and split out using the churn. Samples for pesticides were collected directly into a 3-L Teflon® bottle from each section of the stream and were not composited into the polyethylene churn. Water samples for pesticides were drawn from the Teflon® churn splitter (after August 2002) and filtered through a 0.7-µm baked glass-fiber filter into 1-L baked glass bottles, stored at less than 4°C, and shipped to the NWQL within 24 hours. Samples for major ions and nutrients were drawn from the churn splitter and filtered or preserved, if necessary. Subsamples for analysis of filtered nutrients were pumped through a disposable 0.45-µm filter cartridge into opaque polyethylene bottles and chilled to less than 4°C. Samples for analysis of unfiltered nutrients were collected in translucent polyethylene bottles and preserved with sulfuric acid to a pH less than 2. Samples for analysis of major ions also were filtered through a 0.45-µm filter cartridge, and samples for analysis of cations, iron, and manganese were acidified with nitric acid to a pH less than 2. Samples were shipped on ice to the NWQL for pesticide and major ions analysis, and samples were shipped to the Bureau of Reclamation Boise laboratory for nutrients analysis. All equipment used to collect and process samples was cleaned with a 0.2-percent non-phosphate detergent, soaked in a 5‑percent hydrochloric acid solution, and rinsed with deionized water, as described in Wilde (2004). Equipment used to filter the pesticide samples was additionally rinsed with pesticide-grade methanol and pesticide-free reagent water. All cleaned equipment was placed in doubled plastic bags and stored in a dust-free environment prior to sample collection.

Table 3. Inorganic and organic analytes and schedules, analytical methods, and references.

[Abbreviations: °C, degrees Celsius; CAS, Chemical Abstract Services; IC, ion-chromatography; ASF, automated-segment flow; ISE, ion-selective electrode; ICP, inductively coupled plasma; SPE, solid-phase extraction; GC/MS, gas-chromatography/mass spectrometry; HPLC/MS, high-performance liquid chromatography/mass spectrometry; USEPA, U.S. Environmental Protection Agency]

Analyte or schedule CAS registry No. Analytical method Analytical method reference
Inorganic compounds
Calcium 7440-70-2 ICP Fishman, 1993
Chloride 16887-00-6 IC Fishman and Friedman, 1989
Fluoride1 16984-48-8 ASF ISE Fishman and Friedman, 1989
Iron 7439-89-6 ICP Fishman, 1993
Magnesium 7439-95-4 ICP Fishman, 1993
Manganese 7439-96-5 ICP Fishman, 1993
Potassium2 7440-09-7 ICP American Public Health Association and others, 1998
Residue, 180°C Gravimetric Fishman and Friedman, 1989
Silica 7631-86-9 Colorimetry, ASF, molybdate blue Fishman and Friedman, 1989
Sodium 7440-23-5 ICP Fishman, 1993
Sulfate 14808-79-8 IC Fishman and Friedman, 1989
Ammonia as N ISE, USEPA Method 350.3 U.S. Environmental Protection Agency, 1979
Ammonia plus organic nitrogen as N 7727-37-9 Total Kjeldahl Nitrogen, (colorimetric, semi-automatic), USEPA Method 351.2 U.S. Environmental Protetection Agency, 1993
Nitrite plus nitrate as N Nitrate-Nitrite Nitrogen by colorimetry, USEPA Method 353.2 U.S. Environmental Protetection Agency, 1993
Orthophosphorus as P Phosphorus, all forms (colorimetric, automatic, ascorbic), USEPA Method 365.1 U.S. Environmental Protetection Agency, 1993
Phosphorus as P Phosphorus, all forms (colorimetric, automatic, ascorbic), USEPA Method 365.1 U.S. Environmental Protetection Agency, 1993
Organic compounds
Schedule 2001 Various (see table 4) SPE technology and GC/MS Zaugg and others, 1995; Lindley and others (1996); and Madsen and others (2003)
Schedule 2060 Various (see table 4) SPE technology and HPLC/MS Furlong and others (2001)

1Analyzed by manual ISE method (Fishman and Friedman, 1989) from July 2002 through April 2003.

2Analyzed by flame atomic absorption (Faires, 1993) prior to May 2003.

Laboratory Methods

Samples for a broad spectrum of pesticides were analyzed at the NWQL using either gas chromatography/mass spectrometry (GC/MS) or high-performance liquid chromatography/mass spectrometry (HPLC/MS) techniques (table 4). Compounds that were sufficiently volatile and thermally stable for gas chromatography were analyzed by GC/MS, as described by Zaugg and others (1995), Lindley and others (1996), and Madsen and others (2003); the remaining pesticides were analyzed by HPLC/MS, as described by Furlong and others (2001).

The USGS NWQL collects water-quality control data on a continuing basis for method evaluation and to determine long-term method detection levels (LT-MDLs) and laboratory reporting levels (LRLs). Concentrations are reported as less than the LRL for samples in which the analyte was not detected or failed to meet necessary identification criteria. Analytes detected at concentrations lower than the lowest calibration standard or between the LT-MDL and the LRL and that pass identification criteria are reported with a remark code of “E”. In addition, some analytes generally have low or variable recovery and routinely are reported with an “E” remark code.

Table 4. Pesticide target analytes, laboratory reporting levels, drinking water standards or guidelines, and aquatic-life benchmarks.

[If laboratory reporting level changed during the study, the most frequently used level is indicated. Pesticide target analyte: CIAT, 2-chloro-4-isopropylamino-6-amino-s-triazine; CAAT, chlorodiamino-s-triazine; OIET, 2-hydroxy-4-isopropylamino-6-ethylamino-s-triazine; CEAT, 2-chloro-6-ethylamino-4-amino-s-triazine; GC/MS, gas chromatography/mass spectrometry; HPLC/MS, high-performance liquid chromatography/mass spectrometry. Type of pesticide: F, fungicide; H, herbicide; I, insecticide; S, stimulant; T, transformation product. Drinking-water standards and guidelines: Maximum contaminant levels for drinking water from U.S. Environmental Protection Agency (2004a). Freshwater aquatic-life benchmark: From U.S. Environmental Protection Agency (2004b), unless otherwise footnoted. Abbreviations: CAS, Chemical Abstracts Service; µg/L, microgram per liter; –, no data or not available; *, interim values (Canadian Council of Resource and Environment Ministers, 1997)]

Pesticide target analyte Trade or common name(s) Type of pesticide CAS registry No. Laboratory reporting level (µg/L) Drinking-water standard or guideline (µg/L) Freshwater aquatic-life benchmark(µg/L)
Gas Chromatography/Mass Spectrometry analytical data
Acetochlor Acenit, Sacenid H 34256-82-1 0.006
Alachlor Lasso H 15972-60-8 .005 2
Atrazine1 Aatrexx H 1912-24-9 .007 3 31.8
Azinphos-methyl2 Guthion I 86-50-0 .05 .01
Benfluralin Balan, Benefin H 1861-40-1 .010
Butylate Sutran +, Genate Plus H 2008-41-5 .004 4400
Carbaryl1,2 Sevin, Savit I 63-25-2 .041 4700 3.20
Carbofuran1,2 Furadan I 1563-66-2 .02 40 31.8
CIAT1,2 none T 6190-65-4 .006
Chlorpyrifos Lorsban I 2921-88-2 .005 420 .041
Cyanazine Bladex H 21725-46-2 .018 41 32.0
DCPA Dacthal H 1861-32-1 .003 470
4,4’-DDE none T 72-55-9 .003 1 .001
Desulfinlylfipronil none T .012
Desulfinlylfipronil amide none T .029
Diazinon several I 333-41-5 .005 4.6 5.08
Dieldrin Panoram D-31 I 60-57-1 .009 6.02 .056
2,6-Diethylanaline none T 579-66-8 .006
Disulfoton Di-Syston I 298-04-4 .021 4.3
EPTC Eptam, Eradicane H 759-94-4 .004
Ethalfluralin Sonalan, Curbit EC H 55283-68-6 .009
Ethoprophos Mocap I 13194-48-4 .005
Fipronil Regent I 120068-37-3 .016
Fipronil sulfide none T 120067-83-6 .013
Fipronil sulfone none T 120068-36-2 .024
Fonofos Dyfonate I 944-22-9 .003 410
alpha-HCH none I 319-84-6 .005 7.06
gamma-HCH Lindane I 58-89-9 .004 .2 3.01
Linuron1 Lorox, Linex H 330-55-2 .035 37*
Malathion several I 121-75-5 .027 4100 0.1
Methyl parathion Penncap-M I 298-00-0 .015 32
Metolachlor3 Dual, Pennant H 51218-45-2 .013 4100 37.8*
Metribuzin Lexone, Sencor H 21087-64-9 .006 4200 31*
Molinate Ordram H 2212-67-1 .003
Napropamide Devrinol H 15299-99-7 .007
Parathion several I 56-38-2 .010 .013
Pebulate Tillam H 1114-71-2 .004
Pendimethalin Prowl, Stomp H 40487-42-1 .022
cis-Permethrin ambush, Pounce I 54774-45-7 .006
Phorate Thimet, Rampart I 298-02-2 .011
Prometon Pramitol H 1610-18-0 .015 4100
Propyzamide Kerb H 23950-58-5 .004
Propachlor4 Ramrod H 1918-16-7 .010 490
Propanil Stampede H 709-98-8 .011
Propargite Comite, Omite I 2312-35-8 .023
Simazine Aquazine, Princep H 122-34-9 0.005 4
Tebuthiuron1 Spike H 34014-18-1 .016 3,500
Terbacil1,2 Sinbar H 5902-51-2 .034 390
Terbufos Counter I 13071-79-9 .017 30.9
Thiobencarb Bolero H 28249-77-6 .010
Triallate5 Far-Go H 2303-17-5 .002
Trifluralin Treflan, Trilin H 1582-09-8 .009 35
High-Performance Liquid Chromatography/Mass Spectrometry analytical data
2,4-D Weedon-2,4,-DP H 94-75-7 0.038 70 34.0
2,4-D methyl ester many H 1928-38-7 .016 34.0
2,4-DB2 none H 94-82-6 .020 34.0
OIET2 none T 2163-68-0 .032
3(4-Chlorophenyl)-1-methyl urea none T 5352-88-5 .036
3-Ketocarbofuran2 none T 16709-30-1 .02
Acifluorfen Blazer, Tackle H 50594-66-6 .028 610
Aldicarb2 Temik I 116-06-3 .04 3 31
Aldicarb sulfone2 none T 1646-88-4 .018 2 31
Aldicarb sulfoxide2 none T 1646-87-3 .022 4 31
Atrazine1 Aatrexx, Atratol H 1912-24-9 .008 3 1.8
Bendiocarb Ficam I 22781-23-3 .020
Benomyl2 Benlate F 17804-35-2 .022
Bensulfuron-methyl2 Londax H 83055-99-6 .018
Bentazon2 Adagio, Galaxy, Storm H 25057-89-0 .012 3,200
Bromacil2 Hyvar, Uragon H 314-40-9 .018 90 35.0
Bromoxynil Buctril, Bromanil, Torch H 1689-84-5 .028 35.0
Caffeine None S 58-08-2 .018  
Carbaryl1 Sevin H 63-25-2 .018 4700 3.20
Carbofuran1 Furadan, Crisfuran H 1563-66-2 .016 40 21.8
3-Hydroxycarbofuran None T 16655-82-6 .008
Chloramben, methyl ester2 Amiben H 7286-84-2 .024
Chlorimuron-ethyl2 Classic H 90982-32-4 .032
Chlorothalonil2 Bravo, Forturf F 1897-45-6 .035 55 3.18
Clopyralid Stinger, Lontrel H 1702-17-6 .024
Cycloate2 Ro-Neet, Marathon H 1134-23-2 .014
Dacthal monoacid None T 887-54-7 .028
CIAT1,2 None T 6190-65-4 .028
CAAT2,6 None T 3397-62-4 .022
CEAT2 None T 1007-28-9 .08
Dicamba Banvel, Marksman, Clarity H 1918-00-9 .036 4200 310*
Dichlorprop 2,4-DP, Weedon DP H 120-36-5 .028
Dinoseb2 DNBP, Caldon, Dynamite H 88-85-7 .038 7 3.05*
Diphenamid Rideon, Dymid, Enide H 957-51-7 .010 4200
Diuron DCMU, Direx, Aguron H 330-54-1 .015 410
Fenuron2 Beet-Kleen H 101-42-8 0.032
Flumetsulam2 DE498, XRD 498 H 98967-40-9 .040
Fluometuron Cotoran, Lanex, Cottonex H 2164-17-2 .016 490
Imazaquin2 Skepter 1.5L, Image 1.5LC H 81335-37-7 .036
Imazethapyr2 Pursuit, Pursuit DG H 81335-77-5 .038
Imidacloprid Admire, Gaucho, Merit I 138261-41-3 .020
Linuron1 Lorox, Linex, Afalon H 330-55-2 .014
MCPA Metaxon, Border Master H 94-74-6 .030 34 32.6*
MCPB2 Troptox, Can-Trol H 94-81-5 .010
Metalaxyl Apron, Subdue, Ridomil F 57837-19-1 .012
Methiocarb Draza, Mesurol I 2032-65-7 .010
Methomyl2 Lannate,Nudrin, Lanox I 16752-77-5 .020 4200
Metsulfuron methyl2 Escort, Gropper, Ally H 74223-64-6 .025
Neburon Granurex, Herbalt, Kloben H 555-37-3 .012
Nicosulfuron2 Accent, Accent DF H 111991-09-4 .04
Norflurazon2 Zorial, Evital, Solicam H 27314-13-2 .020
Oryzalin2 Ryzelan, Surflan, Dirimal H 19044-88-3 .012
Oxamyl2 Vydate: Thioxamyl I 23135-22-0 .030 200
Picloram7 Tordon, Amdon, Grazon H 1918-02-1 .020 500 329*
Propham Chem-Hoe, IPC, Premalox H 122-42-9 .030 4100
Propiconazole Tilt, Orbit, Wocosin F 60207-90-1 .010
Propoxur Baygon, PHC, Suncide I 114-26-1 .008 43
Siduron Tupersan, Trey H 1982-49-6 .020
Sulfometuron-methyl Oust, DPX-T5648 H 74222-97-2 .038
Tebuthiuron1 Graslan, Spike, Perflan H 34014-18-1 .032 4500
Terbacil1,2 Sinbar, DPX-D732, Geonter H 5902-51-2 .016 490
Tribenuron methyl2,8 Express, DPX-L5300 H 101200-48-0 .0088
Triclopyr Garlon, Curtail, Redeem H 55335-06-3 .026

1Analyzed by GC/MS and HPLC/MS.

2Because recovery or variation in recovery was outside the acceptable range, compound is qualified with an E-code (estimated).

3Canadian water-quality guidelines for the protection of freshwater aquatic life (Canadian Council of Ministers of the Environment, 2003).

4U.S. Environmental Protection Agency lifetime-health advisory for a 70-kilogram adult (U.S. Environmental Protection Agency, 2004a).

5Great Lakes water-quality objective for protection of aquatic life, from the International Joint Commission (IJC) Canada and United States, 1978.

6U.S. Environmental Protection Agency risk-specific dose health advisory associated with a cancer risk of 10-5 (1 in 100,000) was calculated from risk-specific dose of 10-4 (RSD4) (U.S. Environmental Protection Agency, 2004a).

7U.S. Environmental Protection Agency risk-specific dose health advisory associated with a cancer risk of 10-5 (1 in 100,000), from USEPA Integrated Risk Information System (IRIS) data base (U.S. Environmental Protection Agency, 2005b).

8Tibenuron methyl was routinely reported by the laboratory as a null result because of problems with stability of calibration standards. The analyte was removed from the analytical method September 30, 2004.

Quality Assurance/Quality Control

About 15 percent of all samples submitted to the laboratories were quality-control samples, which included field blanks and equipment blanks to measure possible contamination and bias; replicate samples to measure variability; and field-matrix spike samples to measure recovery of analytes. All samples for pesticide analysis were spiked with surrogate analytes prior to extraction, to monitor accuracy and precision of the analytical procedures. Wilde and others (1999b) define these quality-control samples. Additionally, laboratory quality-control samples were routinely analyzed as part of the laboratory quality-assurance plan described by Maloney (2005).

Field- and equipment-blank samples for pesticide analysis were free of contamination, except for detection of EPTC in one field blank at a concentration of 0.043 µg/L and detection of caffeine in one field blank at an estimated concentration of 0.00043 µg/L. No adjustments were made in the data set or data analysis on the basis of these results.

Precision data were obtained for two sets of replicate pesticide samples (table 16, at back of report). Differences in concentration between replicates ranged from 0 to 71 percent, as measured by relative percentage of difference (94 percent of the differences were ≤5 percent). Percentage of relative differences for atrazine ranged from 5.1 to 71 percent. The relative percentage of difference was 5.1 for one set of replicates using the GS/MS techniques; the relative percentage of difference was 62 and 71 for two other sets of replicates analyzed using the HPLC/MS method. The GC/MS technique is the preferred method of analysis and is the value used for all data analysis. No modifications were made to the data set based on these results. Mean recovery percentages of GC/MS target analytes in field-matrix spike samples ranged from 33 to 213 percent, with a median recovery of 97.5 percent (table 17, at back of report). Mean recovery percentages of HPLC/MS target analytes in field-matrix spike samples ranged from 34 to 150 percent (table 17), with a median recovery of 86.5 percent. Although recoveries of HPLC/MS target analytes generally were lower than recoveries of GC/MS target analytes, recoveries generally are large enough and consistent enough that the data are acceptable and useful for analysis. However, because of lower recoveries and greater variability, the probability of false negatives is greater for HPLC/MS target analytes than for GC/MS and the effective detection level generally is larger. No modifications were made to the environmental data set, but recovery percentages for these analytes need to be considered when interpreting the data.

Seven pesticides were analyzed by GC/MS and HPLC/MS methods. Three pesticides (atrazine, CIAT, and tebuthiuron) were reported only by the “preferred” method (GC/MS). The remaining four pesticides (carbaryl, carbofuran, linuron, and terbacil) were reported with both methods. The NWQL uses a hierarchical procedure in selecting the “preferred” method for these compounds (Mark Sandstrom, USGS National Water Quality Laboratory, written commun., 2004). For the current study, all pesticides were included in the analysis of quality-control samples to determine intra-laboratory method precision and accuracy. Precision between analytical methods is summarized in table 18 (at back of report). Generally, precision between the two analytical methods is good. Comparison between the two methods can be summarized into four categories: (1) both methods reported no detections, (2) both methods reported a detection, (3) one method reported no detection and the other method reported a detection that was either near or less than the reporting level of the other method, and (4) one method reported no detection and the other method reported a detection that was larger than the reporting level of the other method. For example, case 3 is illustrated by a detection of CIAT E0.008 by GC/MS and the HPLC/MS method reporting of CIAT as less than 0.028. Case 4 only occurred with analysis of terbacil, and an example is the detection by GC/MS of E0.026 and the HPLC/MS method reporting of less than 0.010. One method reported a detection and the other did not a total of 13 percent of the time, 11 percent of the time as a case 3 difference and 2 percent of the time as a case 4 difference. This likely indicates the preference for the GC/MS method for the analysis of terbacil.

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