Biomimetic extraction of PAHs and PCBs from soil with octadecyl-modified silica disks to predict their availability to earthworms

We developed a model to predict the availability of PAHs and PCBs to earthworms (Lumbricus terrestris L.) in soils. We related the uptake of PAHs and PCBs by earthworms to the extraction with octadecyl-modified silica disks (C-18 disks). Eleven soils (data set A) were used to develop the model, and 14 additional soils (data set B) were used to validate it independently. The biota-to-soil accumulation factors (BSAFs) of higher molecular weight PAHs (greater than or equal to 202 g mol(-1)) and PCBs were higher than the corresponding C18 disk-soil partition coefficients (K-disk) in the soils of data set A. This suggested that PAHs and PCBs were not only partitioned between soil and earthworms but also selectively ingested or metabolized. Nevertheless, we could predict the BSAFs of individual PAHs and PCBs for data set A by regression equations of log BSAF on log K-disk (r = 0.47-0.87). To predict the BSAFs of all PAHs and PCBs,, respectively, we derived a model for each compound class that uses K-disk and K-ow values. Both the compound and the compound-class specific model were suitable to predict the BSAFs of PAHs and PCBs in data set B within a factor of 10-15.