Effects of storage on the toxicity of sediments spiked with fluoranthene to the amphipod, Rhepoxynius abronius

To determine the effect of storage on contaminant bioavailability and toxic ity, two sediment types, a fine sand and a silty sand, were spiked with nin e concentrations of fluoranthene (0.0-50 mg/dry kg) then stored at 4 degree s C for up to 170 d. Toxicity of the stored sediment was determined eight t imes during this storage interval using standard 10-d toxicity tests with t he marine infaunal amphipod Rhepoxynius abronius. The concentrations of flu oranthene in the sediment and interstitial water were determined on samples taken on each rest date. The toxicity of fluoranthene in the silty sand wa s similar for all storage times with LC50s ranging from 5.3 to 6.6 mg/g org anic carbon (OC). The LC50 in the fine sand was 7.4 mg/g OC after 13 d of s torage, ranged fi om 10.2 to 11.8 mg/g OC during 27 to 83 d of storage, and increased to 24.2 and 27.6 mg/g OC after 121 and 170 d of storage, respect ively. These data indicate that the toxicity of both the fine and the silty sand remained essentially constant during storage from days 27 to 83. Toxi city tests conducted before or after that period may give misleading result s because of disequilibrium or unknown storage effects.