Refined pesticide ecological risk assessments will often require exposure estimates that represent a broad range of aquatic ecosystems. This can include static water bodies such as small ponds and lakes, flowing water bodies ranging from tiny headwater streams to mainstem rivers, as well as intermittent water bodies on the landscape. Spatial datasets are available that allow for the prediction of potential pesticide exposure in these water body types, either in a spatially explicit manner or aggregated to create a distribution of potential exposures over a geographic area of interest. Given the unique characteristics of the water body types of interest, a toolbox of approaches must be developed to appropriately assess their exposure potential. The simulation of pesticide exposure in static water bodies can be conducted using spatially explicit information regarding pond and small lake locations and the cropping patterns and soils surrounding each water body. Simulation of exposure in flowing water bodies can rely on the same information concerning cropping patters and soils but also requires a model of the watershed connectivity and full characterization of upstream areas draining to each flowing water body. Finally, simulation of intermittent water bodies, such as vernal pools, requires a different approach entirely due to the uncertainty in their locations, but can be based upon the principles of pesticide fate and transport that are used in modeling static and flowing water bodies with known locations. The modeling approaches taken for all water body types benefit from the consideration of multiple years of cropping information and historical pesticide use data. This presentation will demonstrate these modeling approaches in the context of a national malathion exposure assessment and describe how the results can be used to generate probabilistic exposure distributions that may be incorporated into refined risk analysis.

Spatially explicit modeling of static, flowing, and intermittent water bodies in probabilistic pesticide exposure assessments

2019 Fall National Meeting

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