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ISOLATING AND EVALUATING ORGANIC TOXICANTS IN SEDIMENTS: EVALUATION OF AN EXPERIMENTAL APPROACH
Citation:
Heinis, L J., D R. Mount, AND T L. Highland. ISOLATING AND EVALUATING ORGANIC TOXICANTS IN SEDIMENTS: EVALUATION OF AN EXPERIMENTAL APPROACH. Presented at Joint Regional SETAC/SOT Annual Meetings, USEPA, Duluth, MN, April 9-10, 2002.
Description:
Most solid-phase sediment toxicity identification and evaluation (TIE) techniques for organic chemicals have been focused on solid phase sorptive techniques, such as amending contaminated sediments with the carbonaceous resin, Ambersorb, coconut charcoal, or XAD resin to reduce toxicity caused by organic contaminants. Challenges in this approach include recovery and extraction of the amendment, and limitations on the mass of toxicants recovered for subsequent identification and evaluation. Solvent extraction of bulk sediment can be used to obtain larger chemical mass, but removing chemical from the sediment matrix eliminates the influence of organic carbon partitioning and bioavailability. In previous work, we overcame this problem reestablished the normal organic carbon partitioning behavior, the relative potency of the chemicals in the extract amended sediment were proportional to that in the original sediment. While we were successful in transfering and testing organic contaminants by this method, it has the disadvantage of requiring lengthy time periods for equilibration. The method presented in this paper utilizes a semi-permeable membrane device (SPMD) as a chemostat, introducing partitioning in sediments and maintains constant exposure concentrations in small test volumes. We have shown that practical steady state aqueous concentrations can be achieved within 24 hours and can be maintained for at least 10 days. partitioning of organic chemicals from the SPMD apparatus agrees well with published Kow values. Ongoing efforts are focused on coupling this exposure procedure with techniques to chemically fractionate the sediment extract leading to the identification of causative toxicants.
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