An approach to quantifying spatial components of exposure for ecological risk assessment

Estimating ecological risks associated with contaminants in the environment requires accurate characterization of the exposure of organisms to potentially toxic materials. Because organisms integrate contaminant exposure over space and time, estimating exposure concentrations reflective of actual exposures is a complex task. Quantification of spatial components of environmental exposure can utilize computerized Geographic Information Systems (GIS) as a central tool. The GIS was used to evaluate ecological risks to terrestrial receptors at a National Priorities List (NPL) site where dieldrin was one of the contaminants. The GIS was applied directly to estimating spatially weighted exposure concentrations within organisms' foraging, or exposure ranges. Moreover, GIS was also used for comparing exposure concentrations to “benchmark” concentrations and subsequent presentation of the results in a three-dimensional “risk surface” format. The three-dimensional risk surfaces were then superimposed on site-specific maps to serve as effective visual representations of site-specific quantified ecological risks and, as such, provide an effective risk-management decision-making tool. As an integral part of this approach, GIS serves as an interactive tool for assessing the effectiveness of proposed remedial alternatives by facilitating evaluation of effects of various remediation scenarios. This capability can be used to optimize remedial costs, benefits, and impacts.