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(P177) Use of the BLM to determine a WER for copper.
Linton, Tyler1, McIntyre, Dennis*,1, Premo, Bette2, Alexander, Michael3, 1 Great Lakes Environmental Center, Columbus, Ohio, USA2 White Water Associates, Inc., Amasa, Michigan, USA3 Michigan Department of Environmental Quality, Lansing, Michigan, USA
ABSTRACT- The Hammell Creek watershed in the upper peninsula of Michigan has experienced water quality standard exceedances for copper from previous mining activity at Osceola, Michigan. A water-effect ratio (WER) investigation was performed for copper in Hammell Creek to establish a site-specific water quality standard for copper in Hammell Creek. WER values were determined both by measuring the toxicity of copper added to site water (upstream Hammell Creek water), and the toxicity of copper in a laboratory reference water, i.e., moderately hard reconstituted water (MHW). The Biotic Ligand Model (BLM, version ap08, HydroQual, Inc.) was also used to estimate copper toxicity based on the chemical composition of these waters. Site water samples used in the three WER determinations were collected on October 1, October 30, and December 18, 2001. The primary and secondary tests used to determine the WER values were the Ceriodaphnia dubia and Pimephales promelas 48-hour static acute toxicity tests. The three dissolved copper WER values obtained from tests with C. dubia were 20, 26, and 43, respectively. The corresponding BLM-predicted WER values were 18, 26, and 17. For P. promelas (tested October 1, 2001), the measured WER and BLM-predicted WER values were 7.5 and 10, respectively. The BLM-predicted LC50 values, however, were on average 2.1 times higher than the actual LC50 values generated in the two waters. Because the higher LC50 estimates generated via the BLM were consistently high in MHW and site water, the BLM-predicted WER values were only marginally different from actual, with the exception of the third WER determined for C. dubia. Based on these results, the BLM appears to accurately predict the WER for these two species, although acute toxicity was consistently underestimated.
Key words: biotic ligand model, water effect ratio, bioavailability, copper
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