Effects of freezing on toxicity of sediments contaminated with ddt and endrin

摘要

AbstractTwo freshwater sediments containing 3 and 11 total organic carbon (TOC) were spiked with DDT and endrin to compare the effects of cold (4°C) and frozen (−20°C) storage of the sediment on toxicity to the amphipodHyalella aztecain 10‐d tests. Toxicity of the DDT‐spiked sediment was reduced when it was frozen for 14 d. LC50 values for cold‐stored and frozen‐stored sediments were 4.2 and 7.3 μg/g DDT (calculated on dry solids basis) at 3 sediment TOC and 11.1 and 23.2 μg/g DDT at 11 sediment TOC, respectively. Toxicity of the 3 TOC endrin‐spiked sediment was reduced by freezing; it exhibited LC50s of 5.1 and 7.7 μg/g endrin, respectively, for cold and frozen storage. Toxicity of endrin in two tests in the 11 TOC sediment remained essentially unchanged by freezing. LC50s were 19.6 and 21.7 μg/g endrin for cold and frozen sediments in one test and 10.3 and 9.8 μg/g endrin in the second test. Decreased toxicity was assumed to be related to the release of soluble organic carbon from the sediments during freezing and thawing. Relative differences in toxicity between DDT and endrin for cold and frozen sediments appear to be related to the different adsorptions of the chemicals onto t