Risk-Trace: Software for Spatially Explicit Exposure Assessment

摘要

Large areas of valuable habitats have been physically disturbed and/or contaminated by hazardous pollutants as a result of industrial activities. This paper presents a methodological approach and a software prototype for spatially explicit risk assessment of contaminated terrestrial ecosystems, to be implemented as a part of a risk-based decision protocol to support the assessment of ecological value and site reuse options. Exposure estimates for wildlife in areas containing spatially localized contaminants are functions of spatial factors, such as the receptor's average foraging area, the size of the habitat being assessed, and the distribution of contamination. Species exhibiting different foraging strategies may experience significantly different chemical exposures from the same site, even if their foraging areas overlap. Currently, exposure estimates and subsequent human health and ecological risk projections usually assume a static and continuous exposure of an ecological receptor to a contaminant concentration represented by some descriptive statistic, such as the mean or maximum concentration. These assumptions are generally overly conservative and ignore some of the major advantages offered by advanced risk assessment techniques, such as the ability to account for site-specific conditions and to conduct iterative analyses. We developed a spatially explicit foraging model that provides a time series estimation of soil and food contamination that receptors may encounter in their daily movements. The model currently inputs information on: the geospatial parameters of the contaminated area, surrounding land, and the habitat types found in each; density and distribution of ecological receptors; receptor home range; maps of contamination concentrations and habitat disturbance; and receptor's foraging range. The model also employs habitat quality factors that account for differential attraction to various habitat types within the site. This paper presents a software prototype that calculates chemical accumulation by a receptor foraging in areas having specified contamination patterns and habitat parameters.