201• 529 • 5151www.hydroqual.comJuly 2010Estimating Chemical Concentrations inUrbanized Watersheds using TREXMark Velleux, Paul Paquin,Aaron Redman, and Robert Santore2Our Focus: Antimicrobial PesticidesAntifoulants, biocides wood preservatives, etc.Differ from agricultural pesticides:“[D]etermining human and ecological risks fromexposure to antimicrobial pesticides requiresdifferent types of measurements and models thanthose needed for pesticides largely applied to cropsand other plants.”Consider antimicrobial copper use in buildingproducts...3Setting: Homogeneous vs. HeterogeneousAgricultural Use:Farm fieldsUniform applicationBuilding Products:Urbanized areasSpatially variable!biocide mass released notequal to mass installedAddress variability withwatershed approach4TREX Watershed Model:Two-Dimensional Runoff, Erosion & Export(Velleux et al. 2008)Major Inputs:Topography (DEM)Soil characteristicsLand coverStream and sedimentcharacteristicsRainfallChemical applicationand release ratesChemical partitioningand fate parametershttp://www.engr.colostate.edu/~pierre/ce_old/Projects/TREX%20Web%20Pages/TREX-Home.html5Case Study: Antimicrobial CopperExamined two separate copper uses:Algae-resistant (AR) shingles (e.g. Cu2O)Treated wood (e.g. CCA, CA, ACQ, etc.)Uses and setting differ from agricultural case:Urban setting with spatially-variable landscape conditionsRainfall-driven releases from roofs, decks, fences, and poles...Lake setting with marinaand inputs from upstreamSimulated copper transport and fate to calculateestimated environmental concentrations (EECs):Excess copperin surface water, sediment, and soil6Setting Based on a Real WatershedLocation:Goodwin Creek, MSBasin Size:21.4 km2(5,104 acres)Landcover:Grassland, pasture, etc.Landcover was modified torepresent an urban setting...Database:14 stream gages, GIS dataModel Resolution:90 m x 90 m (2,558 grid cells)R. Rojas, 20027Urban Setting DevelopmentSimulated urban land cover for Goodwin Creek siteSetting reflects spatial variations in development:Includes a range of housing density: 1, 4, & 8 house(s)/acrePercentage of houses with ARshingle roofs determined fromexpected market share informationPercentage of houses with deck and fences determined fromCensus Bureau statistics and market share informationUtility pole placement and treatment type based on study forToledo, Ohio urban areaExpected to represent reasonable maximum copper use8Copper Sources: Urban SettingAR Shingle Roofs,Treated Wood Decksand Fences...Copper Source Detail9Overall Summary of Copper Release Rates0.1110100Shingles CCA Non-CCA CCA Non-CCA

Release Rates (see legend for units)Intermittently-Wetted Wood(mg m-2mm rain-1)AR-shingles(mg m-2mm rain-1)Continuously-Wetted Wood(mg m-2days immersion-1)0.16 mg/m2/mm0.26 mg/m2/mm3.2 mg/m2/mm2.2 mg/m2/day26 mg/m2/dayOverall: 2.6 mg/m2/mmOverall: 14.1 mg/m2/dayOverall = 20% CCA, 80% non-CCA10Environmental Benchmarks for CopperSurface water:Biotic Ligand Model (BLM)Water quality for regional sitesValues vary by monthSediment:Equilibrium sediment guidelines(ESG) (USEPA, 2000)Copper as excess metalAssume 5% organic carbon insedimentSoil:Empirical relationships (Rooney et al.2006)Used local soil chemistry data11Results for Algae-Resistant ShinglesTREX was used to perform simulations for 770+individual storm events over a 10 year periodDaily average EECs calculated for surface waterand also in soil and sediment12Copper from AR Shingles Over 10 Years: WaterOver 10 years:Mean = 0.25 μg/LSt Dev = 0.79 μg/LMin = 0 μg/LMax = 7.1 μg/LCu releases driven by rainfall10% of Cu release goes tostream, 1% exportedEECs at watershed outletWater benchmark: time variable13Copper from AR Shingles After 10 Years: SoilSpatially variabledistribution of homeswith AR shingle roofsCu releases drivenby rainfall90% of Cu infiltratesAfter 10 years:Mean = 1.7 mg/kgSt Dev = 1.5 mg/kgMin = 0 mg/kgMax = 8.8 mg/kgSoil benchmark:36 mg/kg14Copper from AR Shingles After 10 Years: SedimentSpatially variabledistribution of homeswith AR shingle roofsCu transport drivenby runoff from rainfall9% of Cu depositsAfter 10 years:Mean = 6.7 mg/kgSt Dev = 4.9 mg/kgMin = 1.0 mg/kgMax = 34.5 mg/kgSediment benchmark:320 mg/kg15and Benchmarks: AR ShinglesEECsand Benchmarks: AR ShinglesMediaConcentrationUnitsMeanSt DevMinMaxBenchmarkUrban SettingWater0.250.7907.111.7 – 33.7μg/LSediment6.74.91.034.5320mg/kgSoil1.71.508.836mg/kgAquatic Setting (includes marina)Water0.230.0600.4211.7 – 33.7μg/LSediment0.14n/an/an/a320mg/kgNotes: Surface water benchmarks are time variable to reflect water chemistrydifferences over time. Ranges of values also vary to reflect possible conditionsexpressed as upper window, average, and lower window values. Values shownrepresent an average condition for six sites.16Simulated Copper Mass Fate: Urban SettingOver 10 years:90% infiltrates to soil10% runs off to stream9% deposits to sediment1% leaves watershedMost copper infiltratesbecause nearly all is inthe dissolved phase...Once in surface soil,copper sorbs to particlesurfaces and does notsignificantly leach...Algae-Resistant ShinglesTreated Wood (Decks, Fences, Poles)17Benchmark ExceedancesNote: For surface water, three benchmarks were evaluated: (1) upper (lesssensitive); (2) average; and (3) lower(more sensitive). Exceedances reflectthe number of days in 10 years whendissolved copper concentrations aregreater than the benchmark for that day. An exceedance rate of 1 day in 3years (3-4 days in 10 years) or lessis typically considered acceptable.BiocideAR ShinglesTreated WoodSettingUrbanAquaticUrbanAquaticSurface WaterUpperAverageLowerZeroZeroZeroZeroZeroZeroZero2 days in 10 years64 days in 10 yearsZeroZeroZeroSedimentZeroZeroZeroZeroSoilZeroZeroZeroZero18OutcomesResults are expected to be conservative:Settings include high-end estimates for density of copper useon land surface and in streamLow TSS and low Kpmaximize dissolved copper EECsGenerally low EECs consistent with low releases:Very low effective application rates compared to agriculturaluses: 0.15–0.32 lbs/acre/year vs. 1–16 lbs/acre/yearSimulated EECs similar to measurements in urban water(Boulanger and Nikolaidis, 2003)Simulated EECs much lower than measured at agricultural siteswith high application rates (Fernández-Calviño et al. 2008)19Copper Application Rate Comparison20Our InterpretationFor both urban and aquatic settings, EECs are notexpected to exceed benchmarks for most conditionsWhere EECs do not exceed benchmarks, copper usesnot likely to pose significant environmental risks.For treated wood, surface water EECs may exceedlower window benchmark values in urban setting:Potential for exceedances drivenby conservative assumptionsSuch conditions are unlikely tooccur for more typical usedensity and environmental conditions.Overall, copper use in shingles and treated wood notlikely to pose unacceptable environmental risks.201• 529 • 5151www.hydroqual.comJuly 2010Any Questions?22Extra SlidesResults for Treated Wood(Decks, Fences, and Utility Poles)23Copper from Treated Wood Over 10 Years: WaterOver 10 years:Mean = 0.58 μg/LSt Dev = 1.7 μg/LMin = 0 μg/LMax = 16.7 μg/LCu releases driven by rainfall10% of Cu release goes tostream, 1% exportedEECs at watershed outletWater benchmark: time variable24Copper from Treated Wood After 10 Years: SoilSpatially variabledistribution of homeswith decks, fences...Cu releases drivenby rainfall90% of Cu infiltratesAfter 10 years:Mean = 3.8 mg/kgSt Dev = 4.9 mg/kgMin = 0 mg/kgMax = 31.8 mg/kgSoil benchmark:36 mg/kg25Copper from Treated Wood After 10 Years: Sed.Spatially variabledistribution of homeswith decks, fences...Cu releases driven byrainfall90% of Cu infiltratesAfter 10 years:Mean = 14.1 mg/kgSt Dev = 9.4 mg/kgMin = 2.1 mg/kgMax = 66.8 mg/kgSediment benchmark:320 mg/kg26and Benchmarks: Treated WoodEECsand Benchmarks: Treated WoodMediaConcentrationUnitsMeanSt DevMinMaxBenchmarkUrban SettingWater0.581.7016.711.7 – 33.7μg/LSediment14.19.42.166.8320mg/kgSoil3.84.9031.836mg/kgAquatic Setting (includes marina)Water0.680.150.0011.111.7 – 33.7μg/LSediment0.40n/an/an/a320mg/kgNotes: Surface water benchmarks are time variable to reflect water chemistrydifferences over time. Ranges of values also vary to reflect possible conditionsexpressed as upper window, average, and lower window values. Values shownrepresent an average condition for six sites.27Copper Release Rate: AR Shingles0.11101001000100001.E+001.E+011.E+021.E+031.E+041.E+05Cumulative Rainfall (mm)

Cumulative Copper Release (mg m-2)Palo AltoHoustonHomesteadHagerstownMeanU95%L5%Short-Term (Palo Alto)Study1 test panel, 3 monthsMean = 0.52 mg m-2mm-1All Long-Term StudiesMean = 0.16 mg m-2mm-1Houston Study11 test panels, 8-15 yearsMean = 0.09 mg m-2mm-1Hagerstown Study6 test panels, ~13 yearsMean = 0.28 mg m-2mm-1Homestead Study18 test panels, ~4-14 yearsMean = 0.15 mg m-2mm-128Extra SlidesDetermination of Copper Release Rates29Copper Sources: Treated Wood (exposed)