Copper bioavailability in Steilacoom Lake sediments

Sediments were collected from Steilacoom Lake, Pierce County, in Washington State, and amended with copper sulfate (nominal concentrations of 800, 1,0 00, 1,500, and 2,000 mg Cu/kg dry weight) to assess copper bioavailability to Hyalella azteca, Chironomus tentans, or Ceriodaphnia dubia. H. azteca su rvival and C. tentans survival and growth were not significantly affected, with 10-day no observed effects concentrations (NOEC) and lowest observed e ffects concentrations (LOEC) of 2,010 and >2,010 mgr Cu/kg, respectively. C . dubia was the most sensitive organism tested with 10-day NOEC and LOECs f or survival and reproduction of 906 and 1,469 mg Cu/kg, respectively. Sedim ent AVS concentrations were <0.15 mu mol/g, while simultaneously extracted metal (SEM) concentrations were greater than or equal to 5.71 mu mol Cu/g. Dissolved interstitial water concentrations ranged from below detection (0. 010 mg/L) to 0.24 mg Cu/L, with interstitial water toxicity units as high a s 3.4. Based on this study, effects to C. dubia may occur at bulk sediment concentrations >906 mg Cu/kg. Further, AVS and interstitial water concentra tions are not accurate predictors of copper bioavailability in Steilacoom L ake.