Bioavailability-based assessment of aryl hydrocarbon receptor-mediated activity in Lake Tai Basin from Eastern China.

Coupling polydimethylsiloxane (PDMS)-based equilibrium passive sampling with chemical and bioassay analysis, we assessed aryl hydrocarbon receptor (AhR)-mediated activity and contributing chemicals in sediment from Lake Tai Basin, Eastern China. The bioanalytical equivalent concentrations (BEQs) of AhR-active chemicals for the exhaustive (total burden) and PDMS extracts (bioavailable fractions) ranged from <9.5-300 ng TCDD-EQ/ kgdry weight (dw) and <0.096-2.2 ng TCDD-EQ/kgdw, respectively, which were of average levels compared to those reported elsewhere. The total concentrations of PAHs in sediment and PDMS were 17-4700 μg/kgdw and 0.61-10 μg/kgdw, respectively. The majority of the exhaustive extracts subject to acid treatment showed >70% decline in AhR-mediated activity, suggesting the minor contribution by persistent AhR ligands. Targeted analysis of polycyclic aromatic hydrocarbons (PAHs) showed, however, that these chemicals contributed <40% to the overall effect in both exhaustive and PDMS extracts, indicating the presence of other labile AhR ligands. The concentrations of PAHs and BEQs of the AhR-mediated activity attributed to these chemicals in the exhaustive extracts can be back calculated from those in the PDMS extracts via a general organic carbon-PDMS partition coefficient. Similar quantitative conversion between PDMS and aquatic organisms was also verified for aquatic organisms via the lipid-PDMS partition coefficient. Therefore, our study provided a first insight into the quantitative links between bulk chemical burdens in sediment, chemical bioavailability, bioaccumulation potential and resulting mixture effects, as an integral part of predictive environmental risk assessment of contaminated sediment.