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(38-66) Bioavailability of sediment-associated organic chemicals in relation to measured desorption. Kukkonen, Jussi*,1, Gossiaux, Duane2, Landrum, Peter2, 1 University of Joensuu, Joensuu, Finland2 NOAA/Great Lakes Environmental Research Laboratory, Ann Arbor, MI ABSTRACT- Desorption of benzo(a)pyrene (BaP), pyrene, 3,3',4,4'-tetrachlorobiphenyl (TCBP) and 2,2',4,4',5,5'-hexachlorobiphenyl (HCBP) was measured in seven different natural sediments using the consecutive Tenax extraction. Bioavailabilities of these chemicals were measured using Lumbriculus variegatus (Oligochaeta) and Diporeia spp. (Amphipoda) as the test organisms. Each compound was spiked to the sediments at the same molar concentration. Sediment characterization included TOC, TON, sootC, particle size distribution, pigments and NaOH extractable OC. The fraction of rapidly, slowly and very slowly desorbing chemical was calculated as well as rate constants for the desorption from these fractions. The rapidly desorbing fraction probably represents the fraction of sorbed organic compound that dominates the bioavailable portion of chemical by organisms. The bioavailability of the chemicals varied considerably among the different sediments and the TOC content, soot particles or TON content of the sediment did not explain the variation between the sediments. However, sediment pigment content correlated significantly with BSAF values showing that the quality and age of TOC in the sediments plays a role in controlling the bioavailability. Further, there was a negative correlation between the portion of chemical bound by the small particles and the bioavailability (sediment clearance rate or BAF). This means that the distribution of the chemicals among different particle size fractions affects the bioavailability. The flux of the desorbing chemical seemd promising for explaining the bioaccumulation when using desorption data to account for bioavailability. Key words: Sediments, Bioavailability, Desorption, Organic chemicals |
