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(38-49) Bioavailability of sediment-associated tetrachlorobiphenyl to benthic invertebrates. Leppänen, Matti1,3, Landrum, Peter2, Kukkonen, Jussi*,2,3, Greenberg, Marc1, Burton, G Allen1, Robinson, Sander2, Gossiaux, Duane2, 1 Wright State University, Dayton, OH, USA3 University of Joensuu, Joensuu, Finland2 Great Lakes Environmental Research Laboratory, Ann Arbor, MI, USA ABSTRACT- Bioavailability of hydrophobic sediment-associated organic chemicals does not often obey equilibrium partitioning theory. Recent research suggests that chemical desorption limits bioavailability and only a part of particle-associated chemical may actually be available for uptake. The purpose of this work was to examine the roles of chemical desorption and diffusion in sediment on the bioavailability of tetrachlorobiphenyl (TCBP). A creek sediment was spiked with TCBP at concentrations ranging from 2 to 30 mg/kg dry weight. Three benthic species were exposed in sediments and tissue residues after 10-d exposure (Hyalella azteca, Chironomus tentans) and 10-d bioaccumulation kinetics (Lumbriculus variegatus) were recorded. Desorption and diffusion of TCBP was measured using Tenax TA beads in mixed sediment suspension and strips cut from Tenax TA membrane in undisturbed sediment. For all species, the bioaccumulation factors decreased with increasing sediment TCBP concentrations. The size of the rapidly desorbing fraction of chemical obtained in mixed sediment suspension did not explain the results; although, the flux of chemical out from the fast desorbing fraction correlated with the flux of chemical into Lumbriculus at 23°C. However, measurements of desorption and diffusion in the undisturbed system clearly improved our understanding of decreasing BAFs. We hypothesize that in addition to desorption also diffusion of chemical through sediment to the animal also affects the bioavailability of very hydrophobic chemicals Key words: Bioavailability, PCB, Tenax, Desorption |
