Bioaccessibility of polycyclic aromatic hydrocarbons in activated carbon or biochar amended vegetated (Salix viminalis) soil.

The aim of the present study was to determine the effect of activated carbon (AC) or biochars on the bioaccessibility (C) of polycyclic aromatic hydrocarbons (PAHs) in soils vegetated with willow (Salix viminalis). The study determined the effect of willow on the C PAHs and the effect of the investigated amendments on changes in dissolved organic carbon (DOC), crop yield and the content of PAHs in plants. PAH-contaminated soil was amended with 2.5 wt% AC or biochar. Samples from individual plots with and without plants were collected at the beginning of the experiment and after 3, 6, 12 and 18 months. The C PAHs were determined using sorptive bioaccessibility extraction (SBE) (silicon rods and hydroxypropyl-β-cyclodextrin). Both AC and biochar caused a decrease in the C PAHs. Immediately after adding AC, straw-derived biochar or willow-derived biochar to the soil, the reduction in the sum of 16 (Σ16) C PAHs was 70.3, 38.0, and 29.3%, respectively. The highest reduction of C was observed for 5- and 6-ring PAHs (from 54.4 to 100%), whereas 2-ring PAHs were reduced only 8.0-25.4%. The reduction of C PAHs increased over time. Plants reduced C in all soils although effects varied by soil treatment and PAH. Willow grown in AC- and biochar-amended soil accumulated less phenanthrene than in the control soil. The presence of AC in the soil also affected willow yield and shoot length and DOC was reduced from 53.5 to 66.9% relative to unamended soils. In the biochars-amended soil, no changes in soil DOC content were noted nor effects on willow shoot length.