Predicting bioavailability of PAHs and PCBs with porewater concentrations measured by solid-phase microextraction fibers

Bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) was measured in the deposit-feeding oligochaete Ilyodrilus templetoni exposed for 28d to Anacostia River sediment (Washington, DC, USA) and to an initially uncontaminated sediment from Brown Lake (Vicksburg, MS, USA) sequentially diluted with 3 to 25% contaminated New Bedford Harbor sediment (New Bedford, MA, USA). The Anacostia River sediment studies represented exposure to a historically contaminated sediment with limited availability, whereas exposure to the other sediment included both the historically contaminated New Bedford Harbor sediment and fresh redistribution of contaminants into the Brown Lake sediments. Organism tissue concentrations did not correlate with bulk sediment concentrations in the Anacostia River sediment but did correlate with the sequentially diluted sediment. Porewater concentrations measured via disposable solid-phase microextraction fiber (SPME) with polydimethylsiloxane (PDMS), however, correlated well with organism uptake in all sediments. Bioaccumulation was predicted well by a linear relationship with the product of porewater concentration and compound octanol-water partition coefficient (Anacostia, slope=1.08, r²=0.76; sequentially diluted sediments, slope=1.24, r²=0.76). The data demonstrate that the octanol-water partition coefficient is a good indicator of the lipid-water partition coefficient and that porewater concentrations provide a more reliable indicator of bioaccumulation in the organism than sediment concentrations, even when the route of uptake is expected to be via sediment ingestion.