A Strategy for Ecological Risk Assessments for Superfund: Biological Methods for Evaluating Soil Contamination

Abstract

Within the Superfund ecological risk assessment process, soils represent not only complex contaminant sources but also complex exposure systems. Hence, soil contamination evaluations relevant to ecological risk assessments for Superfund sites must consider various routes and sources of exposure, as well as biological targets representative of various plant, animal, and microbial species. Within ecological contexts, biological evaluations in the field and laboratory should be considered critical components in the ecological risk assessment process, since integrated approaches to hazard evaluation consider contaminant bioavailability and subtle expressions of adverse biological effects associated with chronic exposures. Depending upon habitat type -- freshwater, marine and estuarine, wetland, or terrestrial -- field and laboratory methods have been developed for hazard evaluation which lend themselves directly to the Superfund ecological risk assessment process. For example, in various mining districts in the western United States, riparian wetlands are frequently impacted by heavy metal-laden sediments. The present study illustrates preliminary work within a Superfund ecological risk assessment for such a heavy metal-impacted riparian wetland in western Montana. A variety of biological test methods (e.g., terrestrial and aquatic tests) were critical to the wetland evaluation, and in conjunction with chemical analyses, these biological and ecological evaluations yielded an integrated assessment of heavy metal effects on the wetland, and assured that environmental decisions regarding the wetland could be made with reduced uncertainty.