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Integrating laboratory data on major ion toxicity for multiple species into a broader assessment approach
Citation:
Mount, D., R. Erickson, B. Forsman, J. Hockett, C. Jenson, AND T. Norberg-King. Integrating laboratory data on major ion toxicity for multiple species into a broader assessment approach. SETAC North America, Toronto, ON, CANADA, November 03 - 07, 2019.
Impact/Purpose:
This work improves understanding of the aquatic toxicity of major geochemical ion mixtures to aquatic organisms by synthesizing findings from multiple test species. Insights should support development of aquatic life criteria for these ions by Office of Water.
Description:
We have completed extensive acute toxicity testing of major ion toxicity to several freshwater organisms, along with more limited chronic toxicity testing. Comparison of analyses across species has shown both similarities and differences. For example, all species evaluated have shown additive toxicity among sodium salts, but for some species exposure response relationships are best represented by solution osmolarity, while for others sodium activity appears to better explain toxicity. For most species, ion mixtures whose cation composition is dominated by magnesium and/or calcium appear to show toxicity via a different mechanism than for those dominated by sodium, though the relative potency of these two mechanisms varies. With minor exceptions, responses are mostly independent of anion composition, except to the extent that anion composition influences the chemical activity of the cations and contributes to overall osmolarity. In all cases, chemical activity better explains toxicity than mass concentration, though less robust mass concentration-based models may be sufficient for most environmental assessments. We review these findings to identify key issues and potential paths forward for developing a broadly applicable assessment approach.