title: Investigating the role of desorption on the bioavailability of sediment-associated 3,4,3',4'-tetrachlorobiphenyl in benthic invertebrates.
abstract: Only a fraction of all sediment-associated hydrophobic organic contaminants are bioavailable, and a simple Tenax extraction procedure may estimate this fraction. Bioavailability is assumed to coincide with the rapidly and, possibly, slowly desorbing sediment-associated contaminant. River sediment was spiked with radiolabeled (14C) and nonradiolabeled (12C) 3,4,3',4'-tetrachlorobiphenyl (TCBP), and desorption kinetics using Tenax extraction were obtained at 10 degrees C and 22 degrees C. Bioaccumulation was measured in Lumbriculus variegatus, Chironomus tentans, and Hyalella azteca. Desorption of TCBP was triphasic at 22 degrees C and slowed at 10 degrees C to show only biphasic kinetics. The rapidly desorbing fractions decreased with increasing TCBP sediment concentration. The biota sediment accumulation factors, biota accumulation factors, and sediment clearance coefficients (ks) also decreased with increasing sediment TCBP concentration. The rapidly plus slowly desorbing fractions and the total TCBP desorbed when 99.9% of the rapidly desorbing fraction had desorbed were used to estimate bioavailable TCBP. These Tenax-based fractions did not explain the decreasing bioavailability with increasing TCBP load. Several factors, such as animal behavior and TCBP water solubility limitations, were evaluated to explain the concentration effect, but the most likely cause was severe diffusion limitations in whole sediment that were not predicted by the fully mixed Tenax extraction. Therefore, desorbing fractions determined by Tenax extraction overestimated the bioavailable fractions in sediments.
authors.affiliation: Institute for Environmental Quality, Wright State University, 3640 Colonel Glenn Highway, Dayton, Ohio 45435, USA.
authors.forename: Matti T
authors.initials: MT
authors.lastname: Leppänen
authors.forename: Peter F
authors.initials: PF
authors.lastname: Landrum
authors.forename: Jussi V K
authors.initials: JV
authors.lastname: Kukkonen
authors.forename: Marc S
authors.initials: MS
authors.lastname: Greenberg
authors.forename: G Allen
authors.initials: GA
authors.lastname: Burton
authors.forename: Sander D
authors.initials: SD
authors.lastname: Robinson
authors.forename: Duane C
authors.initials: DC
authors.lastname: Gossiaux
mesh_terms: D000327:Adsorption; D033304:Amphipoda; D000818:Animals; D001682:Biological Availability; D002683:Chironomidae; D019015:Geologic Sediments / Q000737:chemistry; D009835:Oligochaeta; D011078:Polychlorinated Biphenyls / Q000032:analysis / Q000493:pharmacokinetics*; D011108:Polymers / Q000737:chemistry; D014018:Tissue Distribution; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000493:pharmacokinetics*
chemical_list: D011108:Polymers; D014874:Water Pollutants, Chemical; C010514:tenax; D011078:Polychlorinated Biphenyls; C028451:3,4,3',4'-tetrachlorobiphenyl