R3 PM Application of Spatially Explicit Techniques in Ecological Risk Assessment
Thursday, 17 November 2005: 1:50 PM - 5:30 PM in Ballroom 3

(GOO-1117-754469) Spatially Explicit Ecological Risk Assessment for Pesticides: Applications of the GeoSpatial Exposure Model (GeoSEM).

Thayer, W¹, Goodrum, P¹, Negley, T¹, ¹ Syracuse Research Corporation, Syracuse, NY, 13212

ABSTRACT- Spatially explicit exposure models can be used in ecological risk assessments to link exposure concentration data with information and assumptions regarding a receptor's habitat use. The spreadsheet model developed by Hope (2005, HERA 11:1-27) provides a framework for investigating alternative exposure scenarios for receptors that exhibit one of different foraging strategies: territorial, nesting, and wide ranging. The same rules for receptor movement behavior were incorporated into the Geospatial Exposure Model (GeoSEM). Case studies were developed to illustrate the application of the spatially explicit model to ecological risk assessments at a scale relevant to agro-environments in which terrestrial receptors (small mammals and birds) may be exposed to pesticide residues both within and adjacent to treated fields. Concentration-time profiles of pesticide residues in potential exposure media (water, soil, forage items) were estimated with fate and transport models typically used by U.S. EPA Office of Pesticides (e.g., PRZM v.3.12, EXAMS v.2.98.04.06, TREX v.1.13). Exposure factors such as ingestion rates, field metabolic rate, and habitat use preferences were obtained from the open literature and Agency guidance. A methodology is proposed to account for multiple chemical stressors for the case in which pesticides that share a common mode of action are applied during the same time of year within the same habitat use area. Population-level effects are estimated by repeating simulations of individuals until population density estimates are matched. Results of simulations with small mammals are linked to a simple food web model for a predatory bird species. Using sensitivity analysis, this case study highlights the relative importance of risk assessment assumptions, including habitat use preferences, foraging strategies, and accounting for multiple chemical stressors. The tool can also be used to inform risk management options that may be most effective at reducing risks, including decisions involving pesticide use practices and land use practices.

Key words: spatially explicit, ecological risk assessment, pesticide mixtures