Assessing Alternate Approaches to Estimating Uptake of Metals by Plants and Animals in Ecological Risk Assessments. W. R. Alsop and J. H. Samuelian, AMEC Earth & Environmental
In the absence of empirical data, there are several approaches used to estimate uptake of metals by plants, and to higher trophic level organisms. The most commonly applied approach used for Ecological Risk Assessments (ERAs) is to apply uptake factors reported by Baes et al (1984), EPA’s Combustion Protocol (EPA, 1998a and 1999a), or those derived by ORNL (Bechtel Jacobs, 1998). Alternate approaches are also available, such as those from EPA’s Sludge Rule (EPA, 1992), EPA’s Cement Kiln Dust Risk Assessment (EPA 1998b) and Fertilizer Risk Assessment (EPA 1999b). These alternate approaches often result in different predicted media concentrations, which are propagated to different predicted exposures to receptor organisms. Unfortunately, many of these approaches do not take into account site-specific characteristics, such as soil type, soil particle distribution, organic carbon content, or complexing agents (such as iron, manganese, and phosphorous oxides) that can affect the bioavailability of the chemicals of concern. Although the predicted results from the alternate approaches could be used as part of a sensitivity analysis, or treated as uncertainty in a probabilistic assessment, it is often more appropriate to identify the most representative tool, especially if a deterministic approach is being used for the ERA. We will also compare predicted results from these different approaches against those from several Case Studies and provide recommendations for methodology, sampling, and assessment approaches.
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