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THE TIERII MODELING APPROACH FOR AQUATIC EXPOSURE ASSESSMENT IN THE U.S. EPA OFFICE OF PESTICIDE PROGRAMS

James Lin, Dirk Young, and Ian Kennedy. OPP/EFED, US EPA, Washington, DC.

As a continued effort to reduce the uncertainties in aquatic exposure assessment, Environmental Fate and Effects Division (EFED) in the Office of Pesticide Programs (OPP) has begun a new initiative to move to a tiered approach to ecological risk assessments. The approach developed includes probabilistic tools and methods for use in the pesticide regulatory process, which would address the magnitude and probability of risk and provide an estimate of the associated uncertainty. The approach proceeds through four levels of analysis or refinement, from simple deterministic quotients through a general probabilistic analysis, to an issue-specific probabilistic assessment in the highest levels. This presentation provides an update on the recent Tier II modeling approach. In addition to standardizing various modeling scenarios for PRZM (Pesticide Root Zone Model) to assess aquatic exposure associated with pesticide application to different crops in different regions, the Tier II approach will also consider the variable volume water body as the standard farm pond in EXAMS (Exposure Analysis Modeling System).

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Poster Outline

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Level 2 Modeling Approach

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Schematic of Level 2 Models

flow chart of inputs to PRZM, AgDRIFT and EXAMS and resulting Estimated Concentrations output

Schematic of Level 2 Models

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PRZM - Pesticide Root Zone Model

diagram of components of PRZM

PRZM - Pesticide Root Zone Model


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EXAMS - Exposure Analysis Modeling System

diagram of processes of EXAMS

EXAMS - Exposure Analysis Modeling System


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AgDRIFT - Spray Drift Model

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Development of Modeling Scenarios

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Major Land Resources Areas and Associated Meteorological Stations

U.S. map indicating major land resources areas and associated meteorological stations

Major Land Resources Areas and Associated Meteorological Stations
(Enlarged Map)

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Some of the Modeling Scenarios

STATECROP MLRA1SOIL
CA Alfalfa17/18Sacramento
CA Citrus17Exeter
CA Corn18Madera
CA Cotton17Twisselman
CA Fruit (non-citrus)17/18Exeter
CA Grape17/18San Joaquin
CA Sugarbeet17/18Exeter
CA Tomatoes17/18Stockton
CA Walnuts / Almonds17/18Mateca
FL Cabbage156BRiviera
FL Citrus156AWabasso
FL Cucumber156BRiviera
FL Sugarcane156AWabasso
FL Sweet Corn156BRiviera
FL Turf156AAdamsville
IL Corn108Adair
LA Sugarcane131Commerce
MN Alfalfa56Bearden
MN Sugarbeet56Adair
MS Corn134Grenada
MS Cotton131Loring
MS Soybean134Loring
NC Alfalfa130Helena
NC Apple130Hayesville
NC Corn - E133ACraven
NC Corn - W130Chewacla
NC Cotton133ABoswell
NC Peanut130Craven
NC Tobacco133ANorfolk
ND Corn56Bearden
ND Wheat56Bearden
OR Apple2Cornelius
OR Berries2Woodburn
OR Christmas Trees2Pilchuck
OR Filberts2Cornelius
OR Grass Seed2Dayton
OR Hops2Woodburn
OR Mint2Newberg
OR Sweetcorn2Woodburn
OR Vegetable (non-tuber) / Snapbeans2Dayton
OR Wheat2Bashaw
PA Alfalfa148Glenville
PA Apple148Elioak
PA Corn148Hagerstown
PA Turf148Gkenville
PA Vegetable / tomatoes148Glenville
TX Alfalfa87Lufkin
TX Corn87Axtell
TX Cotton86Crockett
TX Sorghum87Axtell
TX Wheat86Crockett

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Reference for the Modeling Scenarios

A complete discussion of the purpose and methods of scenario standardization can be found in the Preliminary OP Cumulative Risk Assessment as an appendix located on the following web page:

http://www.epa.gov/pesticides/cumulative/pra-op/

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EFED's Aquatic Exposure Shell

EFED's Aquatic Exposure Shell

graphic of Aquatic Exposure Shell computer screen input page

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Consideration of Variable Pond Volume

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Variable Volume Water Body

model of variable volume water body with input 	of runoff, outputs of evaporation and infiltration

comparison graph of PEAK concentration over time 	for PERL and MATLAB; y-axis in ppb ranging from 0 to 140; x-axis in years over 36 	years

comparison graph of PEAK concentration over time 	for PERL and MATLAB; y-axis in ppb ranging from 0 to 300; x-axis in years over 36 	years

Variable Volume Water Body

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