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(P621) Suspended Solids and Copper Toxicity in Waters with Low Hardness and Alkalinity.
Bearr, Jonathan*,1, Murray-Gulde, Cynthia1, Rogers, John1, 1 Clemson Institute of Environmental Toxicology, Pendleton, SC, USA
ABSTRACT- Adjustments or modifications of generic Water Quality Criteria are required when specific site water deviates from the 'standard' water used in the derivation of the Water Quality Criteria. The objectives of this study were to measure the effects of suspended solids on copper potency and calculated Water-Effect Ratios (WER) for South Carolina waters with low hardness and alkalinity. The WER procedure uses toxicity in site and laboratory waters for determination of site-specific water quality criteria. Two examples of low ionic strength water from South Carolina are: 1) the Saluda River near Williamston, SC and 2) an unnamed tributary of Upper Three Runs Creek at the Savannah River Site (New Ellenton, SC). These waters were amended with copper sulfate to determine 48-hr LC50s and WERs for Ceriodaphnia dubia. In addition, toxicity experiments were conducted after removal of suspended solids (0.45 m filter). For the Saluda River, we observed that the removal of suspended solids could increase copper potency, therefore decreasing the WER by 30% in February and 23% in May (2002). The filtered to unfiltered LC50 ratios were 0.75 (February) and 0.90 (May). For the unnamed tributary, the WER decreased 12% in February and no statistically significant difference was observed in April. While in February, the filtered to unfiltered ratio was 0.95. Copper potency and WERs were also compared with other models of regulatory interest: the Biotic Ligand Model and the Water Quality Criteria (WQC) hardness-based calculations.
Key words: Copper, Solids, WERs, Potency
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