Predicting the acute toxicity of copper in freshwater sediments: Evaluation of the role of acid‐volatile sulfide

Abstract

AbstractAcid‐volatile sulfide (AVS) has been proposed as an important partitioning phase determining the bioavailability of cationic metals in sediments. The objective of this research was to evaluate the role of AVS in determining copper toxicity in sediments from two sites heavily contaminated with copper: Steilacoom Lake, Washington, and the Keweenaw Watershed, Michigan. Sediments from the two sites were used in 10‐d toxicity tests with the amphipod Hyalella azteca, and results of the toxicity tests were compared to bioavailability predictions based on copper and AVS concentrations in the test sediments, as well as copper concentrations in the sediment interstitial (pore) water. Normalization of sediment copper concentrations to AVS accurately predicted sediments that were nontoxic when molar copper‐to‐AVS ratios were less than one; however, toxicity also was frequently not observed in samples with molar copper‐to‐AVS ratios significantly greater than one. In contrast, measurement of pore‐water copper concentrations and subsequent comparison of these concentrations to water‐only copper toxicity data for Hyalella azteca resulted in accurate predictions of the presence and extent of copper toxicity in the test sediments. These results indicate that AVS alone is not an appropriate partitioning phase for predicting copper bioavailability in freshwater sediments.