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

The accumulation of four polycyclic aromatic hydrocarbons ([PAHs]; phenanthrene, pyrene, fluoranthene, and benzo[a]pyrene) was tested in the earthworm Eisenia andrei in a spiked artificial soil medium. A typical peak in the body residues was observed fur all PAHs around day 7, which could not be explained 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 water, the main bioavailable phase for earthworms. This decrease is caused by biodegradation while the low rate of mass transfer from the solid state precludes replenishment. To describe the data, bioavailability was assumed to decline exponentially in time, but the shape of the accumulation curves suggests a more abrupt change. Estimates of the uptake rate (k(1)) are similar 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 dynamic bioconcentration factors (k(1)/k(2)) agree well with an equilibrium partitioning between soil water and the phases inside the organism.