A screening level risk assessment of waterborne copper in San Francisco bay, California, USA

摘要

Studies were conducted in San Francisco Bay, California, USA to determine site-specific water quality criteria for copper and the ability of the Biotic Ligand Model (BLM) to predict copper toxicity in estuarine waters. Tests were conducted using the estuarine bivalve, Mytilus edulis. M. edulis is the species most sensitive to copper in the US EPA's saltwater quality criteria database and is the basis for the present saltwater quality criteria. Results indicate that toxicity to M. edulis is predictable using the BLM and that dissolved organic carbon (DOC) explains most of the variability in the model predictions (r~2 = 0.98). Based on the results of these studies, a simple but conservative model was developed to quantify historical risk levels throughout the Bay. This simple model was applied to San Francisco Bay Regional Monitoring Program data collected three times per year from 16 to 26 stations throughout the Bay from 1993 to 1999. Risk was characterized by dividing the exposure concentration by its site- and date-specific predicted-no-effect concentration. Based on 487 site- and date-specific observations, none of the exposure to predicted-no-effect ratios suggest unacceptable risk existed in the Bay and the probability of unacceptable risk was estimated at <0.2%.