HP3 Metals in the Environment: Regulatory and Risk Concerns
254 Portland Ballroom
1:20 PM - 5:20 PM, Thursday
() Silver water quality criteria development: consideration of salinity and organic carbon influence on chronic marine toxicity.
Ward, T.1, Boeri, R.1, Hogstrand, C.2, Kramer, J.3, Lussier, S.4, Stubblefield, W.5, Wyskiel, D.1, Gorsuch, J.6, 1 T.R. Wilbury Laboratories, Marblehead, MA, USA2 Kings College London, London, England3 McMaster University, Hamilton, Ontario, Canada4 U.S. EPA, Narragansett, RI, USA5 Parametrix, Inc., Corvallis, OR, USA6 Eastman Kodak Company, Rochester, NY, USA
ABSTRACT- The U.S. EPA issued a national ambient water quality criterion for silver in 1980, which established a marine criterion maximum concentration of 3.2 mg/L total silver or 2.7 mg/L dissolved silver. In 1990 a draft marine criterion was proposed for a continuous concentration (CCC) of 0.9236 mg/L, but to date a final chronic criterion has not been established, largely because only one species is represented in the marine chronic database. This study was conducted to develop additional chronic data sets with a fish species and at least one other sensitive marine invertebrate. In addition, the speciation of metals in natural estuarine and marine waters, and the binding of metals to organic complexes have become important considerations for understanding the mechanism of toxicity and for deriving site-specific chronic marine water quality criteria. A series of 28-day chronic toxicity tests with mysids, Americamysis bahia, and silversides, Menidia beryllina, was conducted to evaluate the influence of salinity and organic carbon on the chronic toxicity of silver. Salinity increases in the range of 10 to 30‰ generally decreased toxicity when based on dissolved silver concentrations (i.e., higher concentrations of dissolved silver were required to cause a toxic effect as the salinity of the seawater increased). This pattern of decreasing toxicity with increasing salinity was not observed if the same test results were evaluated against the measured concentrations of free ionic silver rather than dissolved silver. The results of our toxicity tests appear to validate the free-ion activity and biotic ligand models. Increasing the concentration of dissolved organic carbon from <1 mg/L to the apparent maximum achievable concentration of 6 mg/L in seawater had no effect on silver toxicity. A CCC range will be suggested based on these data, and those for a sea urchin study presented in another session.
Key words: marine water quality criteria, silver, Americamysis bahia, Menidia beryllina