title: Influence of sediment ingestion and exposure concentration on the bioavailable fraction of sediment-associated tetrachlorobiphenyl in oligochaetes.
abstract: The desorption and bioavailability of 3,3',4,4'-tetrachlorobiphenyl (PCB 77) were studied in spiked natural sediments at six concentrations. The desorption kinetics were measured in a sediment-water suspension using Tenax resin extraction, and the bioavailability was measured by exposing Lumbriculus variegatus (Oligochaeta) to PCB 77-spiked sediment in a 14-d kinetic study. In addition, freely dissolved pore-water concentrations were measured using the polyoxymethylene solid-phase extraction method. The present study examined whether bioavailability can be defined more accurately by measuring the size of desorbing fractions and the pore-water concentrations than by using the standard equilibrium partitioning approach. The importance of ingested sediment in bioaccumulation also was investigated. Our data showed a clear, decreasing trend in the rapid-desorbing fractions and in the standard biota-sediment accumulation factors (BSAF) with increasing concentration in sediment. Desorbing fractions-refined BSAFs were more uniform across the concentration treatments, and the pore-water PCB 77 concentration predicted tissue concentrations close to observed values. In the risk assessment process, pore-water concentration or desorbing fractions would lead to more precise bioavailability estimates compared with those from the traditional equilibrium partitioning approach. The result also showed, however, that sediment-ingesting worms had access to an additional bioavailable chemical fraction that was especially evident when PCB 77 pore-water concentrations most likely approached the solubility limit. Thus, feeding may modify the bioavailable fraction that cannot be explained by simple equilibrium partitioning models.
authors.affiliation: University of Joensuu, Faculty of Biosciences, P.O. Box 111, 80101 Joensuu, Finland. arto.sormunen@joensuu.fi
authors.forename: Arto J
authors.initials: AJ
authors.lastname: Sormunen
authors.forename: Matti T
authors.initials: MT
authors.lastname: Leppänen
authors.forename: Jussi V K
authors.initials: JV
authors.lastname: Kukkonen
mesh_terms: D000818:Animals; D001682:Biological Availability; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000032:analysis*; D009835:Oligochaeta / Q000378:metabolism*; D011078:Polychlorinated Biphenyls / Q000493:pharmacokinetics*; D014874:Water Pollutants, Chemical / Q000493:pharmacokinetics*
chemical_list: D014874:Water Pollutants, Chemical; D011078:Polychlorinated Biphenyls; C028451:3,4,3',4'-tetrachlorobiphenyl