WP20 Contaminated Harbor and River Sediment
Wednesday, 16 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(MOU-1117-832154) The significance of non-aqueous phases in assessing the toxicity of contaminated sediments.

Mount, D¹, Heinis, L¹, Highland, T¹, Hockett, J¹, Jenson, C¹, Norberg-King, T¹, ¹ U.S. EPA/ORD, Duluth, MN, USA

ABSTRACT- Although oils, tars, and other non-aqueous liquids are common sources of contamination to aquatic sediments, the toxicity of such contamination has generally been attributed to component chemicals, particularly PAHs. While PAHs can be toxic to aquatic organisms, it is not entirely clear that they are the only source of toxicity from contamination by non-aqueous phases. In laboratory experiments, reference sediments were spiked with either purified triolein or mineral oil, and tested for toxicity. Toxicity to both Hyalella azteca and Chironomus dilutus was observed, even though these two model oils are not thought to have compenents with sufficient solubility to cause toxicity. Additional experiments using a water accommodated fraction (WAF) of mineral oil showed no toxicity to either species, suggesting that the effects observed in spiked sediment are not mediated via soluble components of the oil, but perhaps by the presence of the non-aqueous phase itself. When "oil" was quantified gravimetrically via solvent extraction, the exposure response curves for both model oils were similar. Measurements of solvent-extractable material in toxic field sediments indicate the presence of non-aqueous phases at concentrations comparable to those found toxic in spiked sediment tests. The results of these studies suggest that greater attention should be given to the quantification and assessment of effects from non-aqueous phases in field sediments. This abstract does not necessarily reflect EPA policy.

Key words: sediment, oil, toxicity, PAH