Toxicokinetics of polycyclic aromatic hydrocarbons in Eisenia andrei (Oligochaeta) using spiked soil

The accumulation of four polycyclic aromatic hydrocarbons ([PAHs]; phenanth rene, pyrene, fluoranthene, and benzo[a]pyrene) was tested in the earthworm Eisenia andrei in a spiked artificial soil medium. A typical peak in the b ody residues was observed fur all PAHs around day 7, which could not be exp lained from changes in the total soil concentration. It is argued that the most likely cause of this peak is a decrease in the concentration in pore w ater, the main bioavailable phase for earthworms. This decrease is caused b y biodegradation while the low rate of mass transfer from the solid state p recludes replenishment. To describe the data, bioavailability was assumed t o decline exponentially in time, but the shape of the accumulation curves s uggests a more abrupt change. Estimates of the uptake rate (k(1)) are simil ar fur all PAHs when expressed on soil solution basis (approximately 2,000 L/kg/d); the elimination rate (k(2)) shows a decrease with K-ow as expected , but the values tend to be slightly lower than literature data. The dynami c bioconcentration factors (k(1)/k(2)) agree well with an equilibrium parti tioning between soil water and the phases inside the organism.