Measuring bioavailability of polychlorinated biphenyls in soil to earthworms using selective supercritical fluid extraction

The uptake of PCBs by earthworm (Eisenia foetida) was investigated. PCB contaminated soil was pre-extracted with selective non-exhaustive SFE (50 °C, 350 bar, 1 h), which removed on average 70% of the individual PCBs. Earthworms were placed in this pre-extracted soil, as well as in untreated soil. After 10 days, the PCB uptake by earthworms in the two systems was compared. The bioaccumulation factor (BAF) was 83% lower in the pre-extracted system than in the untreated system, demonstrating that SFE extracts primarily bioavailable contaminants. From the data, the bioavailable fraction could also be calculated to be 75%, which is very close to the 70% removed by SFE under the applied conditions. This suggests that the chemical methodology is capable of measuring the bioavailable fraction very accurately in this system.