Impact of sediment manipulation on the bioaccumulation of polycyclic aromatic hydrocarbons from field-contaminated and laboratory-dosed sediments by an oligochaete

The accumulation kinetics of polycyclic aromatic hydrocarbons (PAHs) by the freshwater oligochaete Lumbriculus variegatus were measured for field-cont aminated and laboratory-dosed sediment. In addition, sediment manipulations typically used for homogenization and dosing in bioaccumulation assays wer e compared. Rather than an asymptotic approach to steady state, both reside nt and dosed PAH accumulation exhibited a peak during the 14-d assays, with steeper declines being noted for the lower-molecular-weight compounds. Lac k of evidence of a peak for higher-molecular-weight PAHs may be due to slow er kinetics and the short length of the assay. Relative to minimally mixed sediment, slurried sediment enhanced the accumulation of less-soluble resid ent PAHs, did not affect moderately soluble PAHs, and reduced the uptake of the more-soluble PAHs, fluorene and phenanthrene. Aging sediment after mix ing reduced the availability of highly to moderately soluble resident PAHs but had no effect on less-soluble PAHs. A similar effect was noted for dose d PAHs, though a larger reduction in bioavailability was observed. Dosed PA H uptake clearance coefficients (k(s)) exceeded those of minimally mixed re sident PAHs by factors of 3 to 4 for pyrene and 26 for benzo[a]pyrene. Thes e results demonstrate that sediment manipulations and contamination history need to be considered when measuring PAH bioaccumulation.