Bioaccumulation in earthworms (Eisenia andrei) of polycyclic aromatic hydrocarbons (PAH) from biochar

Biochars contain relatively low but variable concentrations of PAH and extensive biochar application could therefore result in bioaccumulation by soil biota In this study, we analyzed PAH bioaccumulation in adult specimens of Eisenia Andrei exposed to two types of biochar: biochar from wine tree cuttings (WB) and a commercial low tar hardwood lump charcoal (CB) Pots containing a moist soil (clay or sandy-loam) received 42g biochar/kg of soil (100 t/ha) Nearly all the earthworms were found alive and in good conditions in controls after 45 days, but only 64 5% survived in the sandy soil and 78 4% in the loam soil treated with biochar The two different types of biochar tested displayed a significantly different toxicity: in fact the average survival rate was 60 9% for CB and 80 3% for WB (97 2 % in controls) The way of biochar placement had no effect on earthworm survival or PAH accumulation PAH accumulation was much larger in the sandy soil than in the clay soil and largest in soils amended with CB In this treatment, the concentration of fluoranthene in earthworms was 125 times larger that of earthworms reared in the corresponding control treatment, crysene was 368 times larger, benzo [a]fluorene 136 and benzo[a]pyrene 119 times No accumulation was found in the clay soil for PAH of large molecular weight Environmental safety of reiterated massive biochar additions should not be given for granted and require further research to assess potential impacts on soil biota and the food chain