Predicting PAHs bioavailability for earthworms by mild solvents and Tenax extraction

The total concentration of organic contaminants in soil often overestimates their environmental risk, it is thus important to establish time- and cost-efficient chemical techniques for predicting their bioavailability. In the present study, three chemical extractions, namely: Tenax extraction, butanol extraction and HPCD extraction, were conducted to predict PAHs bioavailability in soil for earthworms. The results showed that earthworm accumulations had less correlation with total concentrations except for PAHs of low molecular weight (R2–3 PAHs). Fractions extracted by butanol/HPCD correlated to earthworm accumulated PAHs of low molecular weight (R2–3 PAHs), but not to earthworm accumulated PAHs of high molecular weight (R5–6 PAHs). Tenax 6 h-extracted PAHs had significantly linear correlations with earthworm accumulated R2–3 PAHs, R4 PAHs as well as R5–6 PAHs (associated R2 were 0.96, 0.98 and 0.97, respectively). Furthermore, Tenax 6 h-extracted concentrations were comparable to earthworm accumulations for R2–3, R4 as well as R5–6 PAHs. These observations verified that Tenax 6 h extraction is better than butanol and HPCD extractions to predict earthworm accumulation of PAHs in soil. Tenax 6 h extraction can serve as a good technique to assess PAHs bioavailability for earthworms.