Dissipation of polycyclic aromatic hydrocarbons in soil amended with sewage sludge compost

• The application of fresh compost accelerated the dissipation of PAHs in soil.
• The amendment ratio of 10% is unlikely to pose an accumulation of PAHs in soil.
• The dehydrogenase activities in soils with amendment of compost were much higher.
• Tall fescue improved PAH degradation in soil and accumulated PAHs in plant tissues.
• Some 2–3-ring PAHs were likely to be volatilized or metabolized in plant tissues.

Greenhouse experiments were conducted with amendment ratios of fresh sludge compost to soil of 0, 10, 25 and 50% (w/w) to investigate the dissipation of polycyclic aromatic hydrocarbons (PAHs) in soils planted with tall fescue (Festuca arundinacea). The initial PAH concentrations in four amended soils increased with the more addition of compost. During the experiment, PAH concentrations decreased in all treatments, and the PAH dissipation followed the first-order kinetics. The residual concentrations in planted soils were lower than those in non-planted soils at every sampling time. After 126 days, the lowest PAH concentration was observed in the soil amended with compost at 10%. These results suggest that appropriate compost addition and planting vegetation could improve the dissipation of PAHs in soil, and the increase of soil dehydrogenase activities due to the increased density and activity of microorganism was an important indicator to obtain the high PAH removal efficiencies in soil. Moreover, some PAHs in soil were absorbed by the roots of tall fescue, then transferred to the shoots and accumulated. During this process, 2–3-ring PAHs were more likely to be absorbed, transferred, and removed in plant, but 4–6-ring PAHs were prone to be accumulated in plant tissues.