title: Equilibrium sampling to determine the thermodynamic potential for bioaccumulation of persistent organic pollutants from sediment.
abstract: Equilibrium partitioning (EqP) theory is currently the most widely used approach for linking sediment pollution by persistent hydrophobic organic chemicals to bioaccumulation. Most applications of the EqP approach assume (I) a generic relationship between organic carbon-normalized chemical concentrations in sediments and lipid-normalized concentrations in biota and (II) that bioaccumulation does not induce levels exceeding those expected from equilibrium partitioning. Here, we demonstrate that assumption I can be obviated by equilibrating a silicone sampler with chemicals in sediment, measuring chemical concentrations in the silicone, and applying lipid/silicone partition ratios to yield concentrations in lipid at thermodynamic equilibrium with the sediment (CLip⇌Sed). Furthermore, we evaluated the validity of assumption II by comparing CLip⇌Sed of selected persistent, bioaccumulative and toxic pollutants (polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB)) to lipid-normalized concentrations for a range of biota from a Swedish background lake. PCBs in duck mussels, roach, eel, pikeperch, perch and pike were mostly below the equilibrium partitioning level relative to the sediment, i.e., lipid-normalized concentrations were ≤CLip⇌Sed, whereas HCB was near equilibrium between biota and sediment. Equilibrium sampling allows straightforward, sensitive and precise measurement of CLip⇌Sed. We propose CLip⇌Sed as a metric of the thermodynamic potential for bioaccumulation of persistent organic chemicals from sediment useful to prioritize management actions to remediate contaminated sites.
authors.affiliation: Department of Applied Environmental Science (ITM), Stockholm University , Svante Arrhenius väg 8, SE-114 18 Stockholm, Sweden.
authors.forename: Annika
authors.initials: A
authors.lastname: Jahnke
authors.forename: Matthew
authors.initials: M
authors.lastname: MacLeod
authors.forename: Håkan
authors.initials: H
authors.lastname: Wickström
authors.forename: Philipp
authors.initials: P
authors.lastname: Mayer
mesh_terms: D000818:Animals; D049872:Bivalvia; D004784:Environmental Monitoring; D005399:Fishes; D019015:Geologic Sediments / Q000032:analysis*; D006581:Hexachlorobenzene / Q000032:analysis*; D060106:Lakes; D008055:Lipids / Q000737:chemistry; D011078:Polychlorinated Biphenyls / Q000032:analysis; D013548:Sweden; D013816:Thermodynamics
chemical_list: D008055:Lipids; D006581:Hexachlorobenzene; D011078:Polychlorinated Biphenyls