title: Effects of contact time on the sequestration and bioavailability of different classes of hydrophobic organic chemicals to benthic oligochaetes (Tubificidae).
abstract: Differences in bioavailability of hydrophobic organic compounds (HOC) to benthic deposit feeders have been related to differences in sediment-HOC contact time and sequestration (formation of slowly desorbing fractions) status. As a consequence, it was postulated that contact time and/or sequestration should be incorporated into risk assessment. In the present study, we investigated the effect of contact time on the bioavailability and sequestration of different classes of HOC. For this purpose, we simultaneously measured the steady-state accumulation into benthic oligochaetes (Tubificidae) and the distribution over rapidly and slowly desorbing fractions in laboratory-contaminated sediment at different contact times. The decrease in rapidly desorbing fractions (Frap) of polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and 2,2-bis (4-chlorophenyl)-1,1-dichloroethylene (p,p'-DDE) after a contact time of 959 d did not exceed a factor of 1.2. Similarly, the reduction in bioavailability was a factor of 2.3 at maximum, indicating that long contact times do not necessarily result in pronounced bioavailability reduction. For chlorobenzenes, the bioavailability was reduced with a factor of 5 to 18. This decrease corresponded with a pronounced reduction in Frap, which was attributed to losses of rapidly desorbing compounds. Over 75% of the variation in biota-to-sediment accumulation factors (BSAFs) of the PAHs and chlorobenzenes at the three contact times could be explained by differences in Frap. The present study provides evidence of a relationship between sequestration status and bioavailability of HOC to benthic deposit feeders.
authors.affiliation: Institute for Risk Assessment Sciences, University of Utrecht, The Netherlands.
authors.forename: Rik H
authors.initials: RH
authors.lastname: Kraaij
authors.forename: Johannes
authors.initials: J
authors.lastname: Tolls
authors.forename: Dick
authors.initials: D
authors.lastname: Sum
authors.forename: Gerard
authors.initials: G
authors.lastname: Cornelissen
authors.forename: Alex
authors.initials: A
authors.lastname: Heikens
authors.forename: Angelique
authors.initials: A
authors.lastname: Belfroid
mesh_terms: D000327:Adsorption; D000818:Animals; D001682:Biological Availability; D004781:Environmental Exposure; D019015:Geologic Sediments / Q000737:chemistry; D009835:Oligochaeta; D009930:Organic Chemicals / Q000493:pharmacokinetics; D018570:Risk Assessment; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000493:pharmacokinetics*
chemical_list: D009930:Organic Chemicals; D014874:Water Pollutants, Chemical