Effects of biochar and the earthworm Eisenia fetida on the bioavailability of polycyclic aromatic hydrocarbons and potentially toxic elements

► Biochar reduced total and bioavailable PAH concentrations. ► Biochar was less effective at immobilising PTEs, due to its low cation exchange capacity. ► E. fetida increased PAH bioavailability and PTE mobility. ► When used in combination biochar reduced the concentration of PTEs mobilised by E. fetida. ► Biochar had a negative effect on E. fetida in terms of weight loss.