EVALUATION OF EQUILIBRIUM PARTITIONING THEORY FOR PREDICTING ACUTE TOXICITY OF FIELD-COLLECTED SEDIMENTS CONTAMINATED WITH DDT, DDE AND DDDTO THE AMPHIPOD HYALELLA-AZTECA

DDT is a persistent and toxic nonionic organic chemical commonly prese nt as a contaminant in aquatic sediments. As a result of effluent disc harges by a chemical company manufacturing DDT on the Redstone Army Ar senal near Huntsville, Alabama, the water column, sediment, and biota of the Huntsville Spring Branch-Indian Creek stream system (HSB-IC) be came heavily contaminated with DDT and its metabolites, DDE and DDD. B ecause DDT appeared to be the primary contaminant in the system, an in vestigation was begun to evaluate equilibrium partitioning theory (EqP ) as a basis for predicting the free pore-water concentrations in and toxicity of DDT-contaminated sediments from the system. In 10-d labora tory, flow-through, water-only exposures with the amphipod Hyalella az teca, LC50 values of 0.07 (0.06-0.28), 1.66 (1.55-1.78), and 0. 19 (0. 160. 41) mug/L were determined for p,p'-DDT, DDE, and DDD, respectivel y. Bulk sediment toxicity assays also were conducted with Hyalella azt eca and pore waters analyzed for the p, p'- and o, p'-isomers of DDT, DDE, and DDD. Measured and EqP-predicted pore-water chemical concentra tions generally agreed within one order of magnitude. Predicted or mea sured Hyalella azteca 10-d pore-water LC50 values for DDT and DDD also were similar to water-only LC50 values for Hyalella azteca. These dat a demonstrate an effect-based EqP prediction of the toxicity of field- collected sediments contaminated by a nonionic organic compound and th e potential utility of the EqP approach for developing sediment qualit y criteria.