title: Bioanalytical effect-balance model to determine the bioavailability of organic contaminants in sediments affected by black and natural carbon.
abstract: In sediments several binding phases dictate the fate and bioavailability of organic contaminants. Black carbon (BC) has a high sorptive capacity for organic contaminants and can limit their bioavailability, while the fraction bound to organic carbon (OC) is considered to be readily desorbable and bioavailable. We investigated the bioavailability and mixture toxicity of sediment-associated contaminants by combining different extraction techniques with in vitro bioanalytical tools. Sediments from a harbour with high fraction of BC, and sediments from remote, agricultural and urban areas with lower BC were treated with exhaustive solvent extraction, Tenax extraction and passive sampling to estimate total, bioaccessible and bioavailable fractions, respectively. The extracts were characterized with cell-based bioassays that measure dioxin-like activity (AhR-CAFLUX) and the adaptive stress response to oxidative stress (AREc32). Resulting bioanalytical equivalents, which are effect-scaled concentrations, were applied in an effect-balance model, consistent with a mass balance-partitioning model for single chemicals. Sediments containing BC had most of the bioactivity associated to the BC fraction, while the OC fraction played a role for sediments with lower BC. As effect-based sediment-water distribution ratios demonstrated, most of the bioactivity in the AhR-CAFLUX was attributable to hydrophobic chemicals while more hydrophilic chemicals activated AREc32, even though bioanalytical equivalents in the aqueous phase remained negligible. This approach can be used to understand the fate and effects of mixtures of diverse organic contaminants in sediments that would not be possible if single chemicals were targeted by chemical analysis; and make informed risk-based decisions concerning the management of contaminated sediments.
authors.affiliation: The University of Queensland, National Research Centre for Environmental Toxicology (Entox), Brisbane, QLD, Australia. Electronic address: j.braunig@uq.edu.au.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Bräunig
authors.affiliation: The University of Queensland, National Research Centre for Environmental Toxicology (Entox), Brisbane, QLD, Australia.
authors.forename: Janet Y M
authors.initials: JYM
authors.lastname: Tang
authors.affiliation: The University of Queensland, National Research Centre for Environmental Toxicology (Entox), Brisbane, QLD, Australia; Queensland Government, Department of Science, Information Technology and Innovation (DSITI), Environmental Monitoring and Assessment Science, Brisbane, QLD, Australia.
authors.forename: Michael St J
authors.initials: MSJ
authors.lastname: Warne
authors.affiliation: The University of Queensland, National Research Centre for Environmental Toxicology (Entox), Brisbane, QLD, Australia; UFZ - Helmholtz Centre for Environmental Research, Cell Toxicology, Leipzig, Germany; Eberhard Karls University Tübingen, Environmental Toxicology, Center for Applied Geosciences, Germany.
authors.forename: Beate I
authors.initials: BI
authors.lastname: Escher
mesh_terms: D000818:Animals; D001681:Biological Assay; D001682:Biological Availability; D002244:Carbon / Q000032:analysis / Q000737:chemistry* / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular / Q000378:metabolism / Q000473:pathology; D004147:Dioxins / Q000378:metabolism; D019015:Geologic Sediments / Q000032:analysis / Q000737:chemistry*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D008113:Liver Neoplasms / Q000378:metabolism / Q000473:pathology; D061986:MCF-7 Cells; D051379:Mice; D015233:Models, Statistical; D018384:Oxidative Stress / Q000187:drug effects; D018336:Receptors, Aryl Hydrocarbon / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000494:pharmacology
chemical_list: D004147:Dioxins; D018336:Receptors, Aryl Hydrocarbon; D014874:Water Pollutants, Chemical; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D002244:Carbon
keywords: Bioavailability; Black carbon; Equilibrium passive sampling; In vitro bioassays; Mixture effect