Wheat straw biochar amendments on the removal of polycyclic aromatic hydrocarbons (PAHs) in contaminated soil

• Removal rates of PAHs were affected by the associated biochar remediation.
• Effects of biochar on activities of DH and PPO were different.
• LS and BR promote soil microbial activity in associated biochar remediation.

Soil amendments of wheat straw biochar (BC), lignocellulosic substrate (LS), BC+LS, and BC+LS+BR (surfactant Brij30) were investigated for the first time in order to remedy polycyclic aromatic hydrocarbons (PAHs)-polluted soil using pilot scale microcosm incubation. We hypothesized that the removal of PAHs could be inhibited due to the adsorption and immobilization of biochar and the inhibition depends on the molecular-weight of PAHs. The removal rates of phenanthrene (PHE) and Benzo[a]pyrene (BaP) ranked as C=BC>LS=LS+BC=LS+BC+BR and C=BC=LS+BC+BR>LS=LS+BC. Wheat straw biochar inhibited the removal of PHE and accelerated BaP removal. The activity of Dehydrogenase (DH) was depressed by the addition of the biochar while the activity of polyphenol oxidase (PPO) was stimulated. Lignocellulose and surfactant are favourable to sustain soil microbiological activity and the removal of PAHs although the diversity of bacterial community was not significantly changed. The findings implied that the components of PAHs are necessary to consider when the amendments are implemented by associated biochar in PAH-polluted soil.