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ISOLATING AND FRACTIONATING ORGANIC TOXICANTS IN SEDIMENTS: EVALUATION OF AN EXPERIMENTAL APPROACH
Citation:
Heinis, L J., D. R. Mount, AND T L. Highland. ISOLATING AND FRACTIONATING ORGANIC TOXICANTS IN SEDIMENTS: EVALUATION OF AN EXPERIMENTAL APPROACH. Presented at 21st SETAC Annual Meeting, Nashville, TN, November 12-16, 2000.
Description:
Most solid-phase sediment TIE techniques for organic chemicals have been focused on solid phase sorptive techniques, such as amending contaminated sediments with the carbonaceousresin, 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. Solvent extraction of bulk sediment can be used to obtained larger chemical mass, but removing chemical from the sediment matrix eliminates the influence of organic carbon on partitioning and bioavailability. In previous work, we overcame this problem by reintroducing the extracts into natural uncontaminated sediment. After equilibration, which reestablished the normal organic carbon partitioning behavior, the relative potency of the chemicals in the extract are proportional to that in the original sediment. While we were successful in transferring organic contaminants by this method, it has the disadvantage of requiring lengthy periods for equilibration. The method presented in this paper utilizes asemi-permeable membrane device (SPMD) as a chemostat, introducing extracted organic contaminants to a water system in a way that mimics natural organic carbon 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. The application o fthis approach in sediment TIE is discovered.