TP20 Ecological Risk Assessment
Tuesday, 15 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(RAM-1117-236446) Application of the Sequential Assessment of Lines of Evidence (SALE) Modified Weight of Evidence Approach to an Aquatic Ecological Risk Assessment.

Swanson, S¹, Ramesh, G¹, Duncan, W², ¹ Golder Associates Ltd., Calgary, Alberta, Canada² Teck Cominco Ltd., Trail, British Columbia, Canada

ABSTRACT- The Sequential Analysis of Lines of Evidence (SALE) approach is presented in a companion poster by Hull and Swanson. An example of the SALE approach to weight of evidence is presented herein for the benthic community of a large river. The first step in the SALE approach was to compare chemical (in this case metal) concentrations in sediment to regulatory criteria. This was done for upstream and downstream sites, and was used to rule out risks for chemicals of potential concern with concentrations less than criteria (step one of the SALE process). The second step was the scoring of laboratory and field lines of evidence relative to causal criteria. The lines of evidence included four toxicity tests (10-day survival and growth of Chironomus tentans, and 20-day survival and growth of Chironomus tentans, benthic community analyses (mean total abundance, total richness, percent dominance of most abundant taxa and combined abundance of sensitive organisms), and an evaluation of habitat quality. The laboratory toxicity tests showed a strong causal relationship and the changes in the benthic community showed a moderate causal relationship to metals in sediment. Indirect effects on habitat quality showed a weak-to-moderate causal relationship to metals in sediment. The third step was the evaluation and documentation of the magnitude of the observed response in each line of evidence (i.e., toxicity test, field community analysis, and habitat evaluation). The SALE weight of evidence summary integrated the information on the magnitude of response with the causal analysis for each site along the river. This summary showed that there are a few depositional areas which should be evaluated for potential risk management. However, risk management clearly is not warranted at several other areas, due to weak responses or weak causal relationships to metals in sediment, or both. The SALE analysis helps to ensure that the proposed risk management is appropriate to the measured or predicted ecological risks.

Key words: Weight of Evidence, Aquatic ERA, Benthic invertebrates, sequential analysis of lines of evidence