Comparative analysis of whole sediment and porewater toxicity identification evaluation techniques for ammonia and non-polar organic contaminants.

Porewater and whole sediment toxicity identification evaluations (TIEs) were performed on contaminated Illinois River sediment and compared using two standardized toxicity-testing organisms (Ceriodaphnia dubia and Hyalella azteca). Results suggested that the choice of testing matrix (porewater versus whole sediment) significantly influenced characterization of toxicity. The porewater TIE suggested that ammonia was the major source of toxicity, while the whole sediment TIE indicated that non-polar organics, specifically polycyclic aromatic hydrocarbons, were the primary contributor to toxicity, with ammonia being a secondary contributor to toxicity. While the choice of test organism may have played a smaller role in the discordance between the TIEs, the data suggest that this factor alone could play a prevalent role in characterizing toxicity in other TIE assessments. Because porewater and whole sediment TIEs examine sediment toxicity differently, using both TIE approaches as part of a risk assessment may provide a more accurate risk estimate of sediment toxicity.