Availability of Polycyclic Aromatic Hydrocarbons (PAHs) and Polychlorinated Biphenyls (PCBs) to Earthworms in Urban Soils

Abstract

We studied the uptake of 20 PAHs and 12 PCBs from 25 field-contaminated soils by Lumbricus terrestris L. and tested the suitability of the equilibrium partitioning theory (EPT) to describe the uptake. The bioavailability of PAHs and PCBs was assessed by exhaustive (hexane-acetone) and nonexhaustive extraction methods (methanol−water 1:1 and 0.5 M NaOH). The latter extracted on average 6−68% and 2−42% of the total PAH concentrations and 7−81% and 9−22% of the total PCB concentrations, respectively. The extractability of an individual compound decreased with increasing octanol−water partitioning coefficient ( K OW ) and was higher for the PCBs than for the PAHs. The EPT described the uptake of PAHs and PCBs well. After 15 d of exposure, the concentrations in earthworms were near steady-state. We found close correlations between concentrations in all extracts and concentrations in earthworms after 15 d of exposure (total: r = 0.75−0.94; methanol−water: r = 0.68−0.94; NaOH: r = 0.59−0.87). The average biota-to-soil accumulation factors ( BSAF ) were 10−100 times higher for PCBs (0.71−70) than for PAHs (0.13−0.41). The BSAFs of the PAHs were independent of K OW; those of the PCBs decreased with increasing K OW (−0.72 ≤ r ≤ −0.97).