Wenlin Chen, Peter Hertl, Paul HendleySyngenta Crop Protection, Inc., Greensboro, NCPreliminary Probabilistic evaluation ofsampling “peak” atrazine residues usingdaily monitoring data from Midwestern nondrinking water streams and rivers2ObjectiveTest three alternatives to daily sampling byevaluating the probability of finding highpercentile atrazine residue concentrations in nondrinking water monitoring data sets fromMidwestern streams and rivers with dailysamples during the high use/runoff seasonCompare findings to USGS study in Perry LakeKS3Data SetsData from flowing water bodies are NOT fromCWS intakesStagnant water data and analysis are cited fromUSGS Perry Lake Study in KS4Data Set 1Syngenta Atrazine Ecological MonitoringProgram (AEMP) 2009 data, including 10 sitesin IN, MO, and NE.oDaily samples between May1 – July 31, 4-daygrabs in April, August, SeptemberoHigh runoff vulnerability, high atrazine useintensity, and Headwater Watershedsbetween 8 and 388 square milesoTypically not representative for drinking waterproduction5Data Set 2Ohio Heidelberg College (OHC) Water QualityMonitoring Program 2000-2004, including HoneyCreek, Rock Creek, Sandusky, and Maumee rivers.oMostly 1 sample/day (up to 3 samples/day) takenduring high runoff season (Apr.15–Aug. 15). Lessfrequent samples for the rest of the calendar year(~2 samples/month) (Richards and Baker, 1993).oWatershed size (square miles): Rock: 34; Honey:149; Sandusky:1251; and Maumee: 6330.oPredominant agriculture land use (67–83% rowcrop)6MethodDeveloped annual daily chemo-graphs from highatrazine runoff season daily data; low atrazine runoffseason daily residue values were estimated byinterpolation from measured valuesRandom Monte Carlo sampling technique -bootstrap,to sample annual daily chemo-graphs based on threealternative sampling scenarios.Comparison of the bootstrap-sampled annualmaximum to the 95% confidence limit (CL) of themeasured data at 95th, 99th, and 99.9thupperpercentiles per site per year7100*% 

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r e n c e−=Daily monitoring dataper site yearAnnual daily chemograph per site year1000 iterationsper site yearThree alternativescenariosDetermine if Simulated Max isequal to or greater than the 95%CL of measured upper percentiles(95th, 99th, & 99.9th)Procedures8Sampling scenarios testedMonthScenario A (summerweekly window=AMP)Scenario B (summer4 day window)Scenario C (summer2 day window)Jan333Feb222Mar222Apr4815May5816Jun4715Jul5815Aug222Sep222Oct222Nov222Dec222Total annualsamples35 48 789Data range and upper percentiles of measured data95th%=6.2 ppbLCL=5.8 ppbUCL=6.9 ppb99.9th%=62.1 ppbLCL=53.3 ppbUCL=71.6 ppbMax=155 ppb99th%=18.2 ppbLCL=16.5 ppbUCL=21.1 ppbNon-parametric estimates by S+ (v.8.1)© and EnvironmentalStats©. Reference: Millardand Neerchal, Environmental Statistics with S-Plus.CRC Press LLC. 2001.10Preliminary ResultsSummary statistics of the river/stream-measured datasetsProbability of bootstrap-simulated daily maximaconcentrations to meet or exceed the lower 95%confidence limit (LCL) of the measured data pointsat 95th,99th, and 99.9thpercentilesA comparison to the statistical analysis availablefromUSGS for Perry Lake, Kansas (1993-1994)11Preliminary statistics (AEMP 2009 data)Site_YearWatershedsize (mi2)No. ofSamplesMax99.9th%centile(1-sidedLCL)*99th%centile (1-sided LCL)*95th%centile(1-sidedLCL)*Min Mean MedianMax/MedianRatioIN-11 9106 21.07 19 (15.5) 8.7 (8.5 ) 3.7 (2.2 ) 0.080 0.76 0.26 81MO-01 12108 72.00 71.9 (71.6 ) 63.1 (29.5 ) 6.6 (2.2 ) 0.025 1.900.07 1029MO-02 28114 155.20 122.7 (66.0 ) 48.7 (30.6 ) 11.2 (7.4 ) 0.025 2.60 0.14 1109MO-04A 8110 52.14 44.2 (30.2 ) 14.2 (10.4 ) 6.0 (4.7 ) 0.025 1.090.12 435MO-04B 388106 23.92 22.4 (19.8 ) 12.9 (10.7 ) 6.1 (4.8 ) 0.025 1.060.19 126MO-05B 182114 67.60 65.8 (62.6 ) 44.3 (32.8 ) 11.7 (9.1 ) 0.025 2.50 0.09 751MO-05 25110 42.60 42.2 (41.6 ) 24.1 (20.1 ) 11.2 (4.8 ) 0.025 1.62 0.30 142NE-05 49107 55.10 46.3 (31.0 ) 25.8 (17.9 ) 8.8 (5.8 ) 0.025 1.410.08 689NE-07 994 19.69 16.2 (10.1 ) 9.2 (7.8 ) 3.1 (2.4 ) 0.025 0.57 0.07 281NE-08B 18893 38.78 31.6 (19.0 ) 13.4 (10.1 ) 6.6 (5.1 ) 0.025 1.11 0.10 388Atrazine Concentration Unit: ppbNE04 not included in analysis since site was dry until May 25th200912Preliminary statistics (OHC 2000-04 data)Site_YearWatershedsize (mi2)No. ofSamplesMax99.9th centile(1-side LCL)*99th centile(1-side LCL)*95th centile(1 side-LCL)*Min Mean MedianMax/MedianRatioHONEY - 2000 149 129 17.25 16.8 (16.1 ) 14.2 (13.0 ) 6.0 (3.8 ) 0.00 0.94 0.15 112HONEY - 2001 149 102 16.32 15.8 (14.8 ) 9.7 (7.9 ) 3.7 (3.2 ) 0.00 0.90 0.31 53HONEY - 2002 149 101 130.42 108.7 (70.7 ) 31.0 (26.1 ) 7.4(4.6 ) 0.00 2.10 0.24 553HONEY - 2003 149 135 13.05 13.0 (12.8 ) 8.8 (6.6 ) 3.6 (2.9 ) 0.04 0.74 0.17 75HONEY - 2004 149 149 46.29 38.0 (23.7 ) 15.4 (11.0 ) 6.4 (4.3 ) 0.00 1.14 0.11 429MAUMEE - 2000 6330 118 11.68 11.0 (9.9 ) 8.5 (7.9 ) 5.9 (4.5 ) 0.00 0.83 0.13 93MAUMEE - 2001 6330 99 26.45 23.9 (19.4 ) 16.2 (14.6 ) 6.6(5.5 ) 0.00 1.32 0.22 118MAUMEE - 2002 6330 81 16.56 16.5 (16.3 ) 13.8 (11.4 ) 9.3(8.7 ) 0.11 2.00 0.31 53MAUMEE - 2003 6330 120 11.86 11.8 (11.7 ) 9.4 (8.2 ) 2.9 (2.5 ) 0.00 0.73 0.12 102MAUMEE - 2004 6330 93 9.29 9.1 (8.8 ) 8.1 (7.1 ) 5.8 (5.0) 0.00 0.89 0.10 94ROCK - 2000 34 93 23.43 21.5 (18.2 ) 12.4 (9.3 ) 2.7 (1.8) 0.00 0.60 0.05 486ROCK - 2001 34 86 17.89 16.5 (14.0 ) 10.7 (8.0 ) 3.3 (1.5) 0.00 0.62 0.10 174ROCK - 2002 34 116 99.58 82.9 (53.7 ) 38.5 (27.1 ) 7.0 (4.1 ) 0.00 2.07 0.15 670ROCK - 2003 34 107 16.37 16.1 (15.6 ) 9.8 (7.2 ) 3.8 (2.8) 0.00 0.70 0.11 155ROCK - 2004 34 137 46.31 39.6 (27.8 ) 19.3 (14.3 ) 5.1 (3.6 ) 0.00 1.09 0.02 2108SANDUSKY - 2000 1251 134 13.94 13.8 (13.5 ) 11.2 (10.4 ) 5.1 (3.7 ) 0.00 0.80 0.13 105SANDUSKY - 2002 1251 118 28.38 27.8 (26.8 ) 20.5 (16.7 ) 9.6 (7.3 ) 0.09 1.73 0.21 133SANDUSKY - 2003 1251 133 11.86 11.8 (11.6 ) 8.6 (7.2 ) 3.8(2.6 ) 0.00 0.73 0.11 108SANDUSKY - 2004 1251 134 24.70 22.5 (18.6 ) 17.2 (12.2 ) 7.4 (6.0 ) 0.00 1.24 0.15 167Atrazine Concentration Unit: ppb13Reported summary statistics in the USGS dailyCWS data (ppb)** Blomquist et al. Pesticides Pesticides in Selected Water-Supply Reservoirs and Finished Drinking Water, 1999-2000:Summary of Results from a Pilot Monitoring Program.U.S. Geological Survey (USGS), Open-File Report 01-456.USGS CWS site Maximum 99th 95thMedian(50th)Max/MedianPerry Lake, Kansas,1993-943.790 3.640 3.475 1.7202Drainage basin size 1,117 mile2Less spikyRelatively lower magnitude14Preliminary Bootstrap simulation results: AEMP2009 dataProbability of bootstrap-simulated daily maxima (1000 rep/site year) meeting orexceeding the 95% lower confidence limit (LCL) of the measured data points at95th, 99th, and 99.9thupper percentilesSite_YearScenario A (growing season weeklywindow =AMP)Scenario B (growing season 4 daywindow)Scenario C (growing season 2 daywindow)95thpercentile99thpercentile99.9thpercentile95thpercentile99thpercentile99.9thpercentile95thpercentile99thpercentile99.9thpercentileIN 11 - 2009100%66% 14%100%89% 26%100%100% 50%MO 01 - 2009100%87% 15%100%96% 26%100%100% 53%MO 02 - 2009100%75% 28%100%94% 45%100%100% 76%MO 04A - 2009100%76% 26%100%92% 44%100%100% 76%MO 04B - 2009100%70% 15%100%90% 25%100%100% 51%MO 05B - 2009100%78% 16%100%100% 24%100%100% 49%MO 05 - 2009100%78% 26%100%100% 47%100%100% 74%NE 05 - 2009100%73% 25%100%95% 43%100%100% 73%NE 07 - 2009100%69% 27%100%88% 44%100%100% 75%NE 08B - 2009100%70% 29%100%93% 50%100%100% 75%Average 100% 74% 22% 100% 94% 37% 100% 100% 65%15Preliminary Bootstrap simulation results: OHC2000-04 dataProbability of bootstrap-simulated daily maxima (1000 rep/site year) meeting orexceeding the 95% lower confidence limit (LCL) of the measured data points at 95th,99th, and 99.9thupper percentilesSite_YearScenario A (growing seasonweekly window =AMP)Scenario B (growing season 4day window)Scenario C (growing season 2 daywindow)95thpercentile99thpercentile99.9thpercentile95thpercentile99thpercentile99.9thpercentile99thpercentile99thpercentile99.9thpercentileHONEY - 2000100%80% 13%100%92% 24%100%100% 50%HONEY - 2001100%71% 27%100%93% 53%100%100% 100%HONEY - 2002100%73% 13%100%92% 27%100%100% 51%HONEY - 2003100%78% 30%100%95% 44%100%100% 74%HONEY - 2004100%71% 27%100%94% 51%100%100% 76%MAUMEE - 2000100%85% 28%100%97% 50%100%100% 100%MAUMEE - 2001100%76% 30%100%94% 50%100%100% 100%MAUMEE - 2002100%83% 24%100%100% 46%100%100% 75%MAUMEE - 2003100%87% 14%100%95% 25%100%100% 53%MAUMEE - 2004100%100% 30%100%100% 49%100%100% 100%ROCK - 2000100%89% 26%100%100% 43%100%100% 72%ROCK - 2001100%81% 14%100%100% 25%100%100% 51%ROCK - 2002100%77% 30%100%95% 47%100%100% 75%ROCK - 2003100%78% 15%100%94% 25%100%100% 49%ROCK - 2004100%82% 14%100%95% 22%100%100% 49%SANDUSKY - 2000100%89% 15%100%97% 24%100%100% 46%SANDUSKY - 2002100%78% 15%100%94% 24%100%100% 53%SANDUSKY - 2003100%89% 13%100%96% 27%100%100% 51%SANDUSKY - 2004100%76% 25%100%92% 44%100%100% 75%Average 100% 81% 21% 100% 95% 37% 100% 100% 68%16Summary results of USGS Perry Lake sampling frequencyanalysis (Blomquist et al., USGS Open File Report 01-456)“Estimates of themaximum value and95th percentileshowed that, basedon sufficiently smallstandard deviations,reasonable measuresof the actual valuescould be determinedusing a monthlysampling frequency.”17Preliminary ConclusionsAtrazine Summary StatisticsoChemographs from rivers/streams are spikier, with max/median ratio~ 53-2018oStatic Water Bodies such as Perry Lake have lower concentrationchanges as evident from much lower max/median ratio (=2).oMagnitude of the peaks in the river systems are higher than inreservoirs.oChemographs in rivers draining larger watersheds tend to be lessspiky than in smaller onesoThe stream data used in these analyses are from environmentalmonitoring programs not CWS intakes18The current 35 samples/year as implemented in AMP will provided:oPotential single maximum exposure values at or above the lower 95%confidence limit for the 95thpercentile 100% of the timeoPotential single maximum exposure values at or above the lower 95%confidence limit for the 99thpercentile level most of the time (74-81%).The 4-day grab program used for the Eco-Monitoringsites provided:oPotential single maximum exposure values at or above the lower 95%confidence limit for the 99thpercentile 94-95% of the timeoGiven the transient nature of peaks in the ecological monitoring data setsit is to be expected that high end percentiles in flowing water bodies inlarger watersheds were determined with even greatercertainty.Given reservoirs less temporal variability in concentration, the AMP samplingprogram is able to sufficiently determine peak exposures equal to or greaterthan the 95thpercentile values.Preliminary Conclusions19Additional Data Recently Submitted by Syngenta●Long-term (1994-2006) Trend in Atrazine Occurrencein Raw Waters ofthe U.S. Midwestern and Southern Community Water Systems (W. Chenet. al, April 16, 2008, Syngenta Crop Protection, Inc.)●Atrazine Evaluation of Sampling Frequency Alternatives for AtrazineMonitoring Program of Raw Water Sources at U.S. Community WaterSystems (W. Chen et. Al., October 13, 2009, Syngenta Crop Protection,Inc.)20Next Steps●Protocol development in Progress with RTI for a feasibility analysis touse the historic DW monitoring data to determine-The probability for a high percentile concentrationwithin the time andspace domain of historic drinking water monitoringdata-An estimate a high quantile concentration in finished drinking waterand its confidence intervals-The probability for this high quantile concentration not to exceed apredefined threshold concentration●Protocol will be provided to EPA●Preliminary Results expected end of January 2010