Ref ID : 6721
Arto J. Sormunen, Matti T. Leppanen, and Jussi V.K. Kukkonen; Influence of sediment ingestion and exposure concentration on the bioavailable fraction of sediment-associated tetrachlorobiphenyl in Oligochaetes. Environmental Toxicology & Chemistry 27(4):854-863, 2008
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The desorption and bioavailability of 3,3',4,4'-tetrachlorobiphenyl (PCB77) 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 PCB77-spiked sediment in a 14-day 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 PCB77 concentration predicted tissue concentration 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 PCB77 pore-water concentration most likely approached the solubility limit. Thus, feeding may modify the bioavailable fraction that cannot be explained by simple equilibrium partitioning models.