Pathways Analysis Method for Estimating Water and Sediment Criteria at Hazardous Waste Sites

Abstract

A model was developed to estimate surface water and sediment criteria for the protection of animal populations and ecosystems at a hazardous waste site where the major contaminants of concern to wildlife populations included persistent, bioaccumulative chemicals. The model evaluates potential exposure pathways for a site and estimates acceptable concentrations in abiotic media for each exposure pathway. To estimate criteria based on food web exposure, the model utilizes a site‐specific food web and addresses bioaccumulation in multiple food chains that terminate in a high‐trophic‐level species. The input data for the food web were obtained from on‐site sampling as well as from literature sources. The pathways analysis model can be applied to other hazardous waste sites by selecting appropriate species and chemical specific input parameters to include in the model. Estimated criteria can be compared to on‐site analytical data to evaluate risk to wildlife populations.

A framework for ecological risk assessment at contaminated sites in Canada

“…Often certain pathways can be quickly eliminated from further consideration through simple calculations. For example, Fordham and Reagan (1991) determined from observed water concentrations and estimated daily water intake that bald eagles' bioconcentration of dieldrin through water ingestion was insignificant compared to their uptake from food. Another important consideration here is the proportion of the time an animal spends in the vicinity of the polluted zone.…”

“…Another important consideration here is the proportion of the time an animal spends in the vicinity of the polluted zone. Fordham and Reagan (1991) assumed conservatively that the aquatic contaminant source provided the bulk of bald eagles' diet even though in reality only 10% of their feeding was based on the aquatic food web.…”

“…Specifying a food chain for model analyses of ecological risk is a compromise between reality and the available data and understanding. Fordham and Reagan (1991) provide the following principles:…”

“…The simplest models of bioaccumulation in food chains rely on five variables at each trophic level (Fordham and Reagan, 1991):…”

“…Monte Carlo analyses must be careful to consider the correlation among parameters; assuming that all parameter distributions are independent will overestimate the level of uncertainty. Fordham and Reagan (1991) provide an excellent example of the application of Monte Carlo analyses to an ecological risk assessment at a hazardous waste site.…”