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(70-74) Development of a risk-based approach for setting water quality criteria for metals. Van Sprang, Patrick*,1, Vangheluwe, Marnix1, Janssen, Colin2, 1 EURAS, Gent, Belgium2 University of Gent, Gent, Belgium ABSTRACT- Currently, water quality guidelines for metals are typically represented by a single threshold value for each individual metal. Compliance is achieved if this treshold value is not exceeded. However, it has been recognised that such a standard approach may not be appropriate to accurately assess the true ecological impact on aquatic ecosystems. Incorporation of bioavailability, using specific toxicity related bioavailability models, has been identified as a crucial issue for setting realistic water quality criteria (WQC). In this study a tiered risk-based framework is proposed to assess the potential impact of metals on aquatic ecosystems. Exceeding the WQC at the lower tier triggers the refinement of the measurements with additional site-specific information in order to incorporate bioavailability. In this study the proposed approach was applied to assess the potential risk of copper in the river Elbe (Germany). From the initial assessment the trigger value for dissolved copper, calculated as the hazardous concentration for 5% of the species (HC5) from chronic toxicity test results, was exceeded for some of the investigated stations. In the second tier both the biotic and abiotic speciation of copper was incorporated in the assessment using a chronic Biotic Ligand Model (BLMc). This model was used to translate the trigger value for copper as a biotic ligand concentration (HC5 expressed in nmol/g ww) and subsequently compared to the bioavailable copper concentrations in the river Elbe. The bioavailable copper concentrations in the river Elbe were all below the adjusted (translated to the biovailable fraction) WQC for copper, which indicates that no Cu-induced adverse effects are expected in the study area. Key words: metals, bioavailability, water quality criteria |
