Derivation of a freshwater silver criteria for the New River, Virginia, using representative species

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Abstract
The U.S. Environmental Protection Agency (EPA) has not published a 30‐d average or continuous criterion for silver due to the apparent toxicity of this element and the lack of available chronic exposure data. The present study examined acute effects on nine species representative or indigenous to the New River, Virginia, and sublethal effects on three of those species using the Resident Species Approach. Our results showed that invertebrates were much more sensitive to silver than fish, including juvenile rainbow trout (Oncorhynchus mykiss). Hyalella azteca (amphipod) was the most sensitive species followed by the mayflies Stenonema sp. and Isonychia bicolor and the stonefly Leuctra sp. The Final Acute Value in this study was 1.32 μg/L total recoverable silver. In sublethal tests, Isonychia growth, as measured by the number of molts over time, was the most sensitive effect observed. Estimated acute:“chronic” ratios ranged from two to 34 with Corbicula fluminea having the largest ratio. Our study results, along with available published data, suggested a Final Chronic Value of 0.13 μg/L total silver which is approximately one‐half the level obtained using the EPA acute formula and ambient water hardness. Our results suggest that a continuous criterion for silver may be predictable using the hardness‐dependent formula and a safety factor of 0.5.