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 (<i>C</i><sub>Lip⇌Sed</sub>). Furthermore, we evaluated the validity
of assumption II by comparing <i>C</i><sub>Lip⇌Sed</sub> 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 ≤<i>C</i><sub>Lip⇌Sed</sub>, whereas HCB was near equilibrium between
biota and sediment. Equilibrium sampling allows straightforward, sensitive
and precise measurement of <i>C</i><sub>Lip⇌Sed</sub>. We propose <i>C</i><sub>Lip⇌Sed</sub> as a metric
of the thermodynamic potential for bioaccumulation of persistent organic
chemicals from sediment useful to prioritize management actions to
remediate contaminated sites