Variation in the Bioavailability of Polycyclic Aromatic Hydrocarbons to the Amphipod Diporeia (spp.) with Sediment Aging

The accumulation kinetics of the amphipod Diporeia sp. for sediment-sorbed polycyclic aromatic hydrocarbon (PAH) congeners were measured where the contact time between the PAH congeners and the sediments varied between 3 and 150 d. Diporeia were exposed to a reference sediment dosed with two radiolabeled PAHs (phenanthrene and pyrene) and to sediments dosed with the two radiotracers and a mixture of PAHs at 272.3 + 10.9 nmol g-' dry sediment, as the sum of the nine nonlabeled PAHs. The sediments were prepared by dosing aliquots of a single collection of sediment with PAHs at different times, producing a series of contact times. The exposures were all performed at the same time from a single collection of organisms. Diporeia were sampled for mortality and toxicokinetics for up to 28 d. Some sediment avoidance was observed during the first 12 d of exposure. The partitioning between sediment particles and interstitial water increased significantly for both phenanthrene and pyrene as contact time increased. The uptake rate coefficient decreased for both phenanthrene and pyrene when the contact with the sediment was increased from 3 to 60 d. When thi contaminant-sediment contact was increased from 60 to 150 d, the phenanthrene uptake rate coefficient remained constant whereas that for pyrene increased somewhat. Similar uptake results were observed with the nonradiolabeled compounds. Keywords-Bioavailability Diporeia Polycyclic aromatic hydrocarbons (PAHs) Sediment storage Sediment aging