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Effects of laboratory test conditions on the toxicity of silver to aquatic organisms

Authors

  • Russell J. Erickson,

    Corresponding author
    1. U.S. Environmental Protection Agency, National Health and Environmental Effects Laboratory, Mid-Continent Ecology Division, Duluth, Minnesota 55804
    • U.S. Environmental Protection Agency, National Health and Environmental Effects Laboratory, Mid-Continent Ecology Division, Duluth, Minnesota 55804
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  • Larry T. Brooke,

    1. Lake Superior Research Institute, Environmental Health Laboratory, University of Wisconsin Superior, Wisconsin 54880 USA
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  • Michael D. Kahl,

    1. U.S. Environmental Protection Agency, National Health and Environmental Effects Laboratory, Mid-Continent Ecology Division, Duluth, Minnesota 55804
    2. Lake Superior Research Institute, Environmental Health Laboratory, University of Wisconsin Superior, Wisconsin 54880 USA
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  • Fred Vende Venter,

    1. Lake Superior Research Institute, Environmental Health Laboratory, University of Wisconsin Superior, Wisconsin 54880 USA
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  • Sandra L. Harting,

    1. Lake Superior Research Institute, Environmental Health Laboratory, University of Wisconsin Superior, Wisconsin 54880 USA
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  • Thomas P. Markee,

    1. Lake Superior Research Institute, Environmental Health Laboratory, University of Wisconsin Superior, Wisconsin 54880 USA
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  • Robert L. Spehar

    1. U.S. Environmental Protection Agency, National Health and Environmental Effects Laboratory, Mid-Continent Ecology Division, Duluth, Minnesota 55804
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  • This manuscript was reviewed in accordance with official U.S. Environmental Protection Agency (EPA) procedures; however, the content does not reflect EPA policy. Mention of trade names does not imply endorsement by the EPA or the U.S. federal government.

Abstract

The effects of various chemical manipulations of test water on acute toxicity of silver to fathead minnows (Pimephales promelas) were investigated. Increases in hardness and organic carbon substantially reduced toxicity. Toxicity was also inversely related to pH and alkalinity when these parameters were jointly changed by addition of strong acid or base. The addition of 2 meq/L sodium sulfate had no significant effects, but the addition of 0.2 meq/L sodium chloride increased toxicity, perhaps related to the formation of the dissolved AgCl0 complex. We also evaluated the effects of static versus flow-through test conditions, feeding during exposure, and aging of test solutions before exposure on the acute toxicity of silver to fathead minnows and Daphnia magna. Static conditions and feeding reduced toxicity, likely as a result of accretion of organic carbon. Aging of test solutions had little effect. For both juvenile fathead minnows and D. magna, silver was much less toxic in water from the St. Louis River than in our normal laboratory water, presumably because of the much higher organic carbon content of the river water. This study identified some aspects of test conditions that are important in assessing the risk of silver to aquatic biota, but improved assessments will require information for more conditions, species, and endpoints. More importantly, if toxicity test results are to be extrapolated among waters with different chemistries, adequate characterization of the chemical speciation of silver and a better understanding of the mechanisms of silver toxicity and its relationship to silver speciation and other chemical factors are needed.

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