Enhanced degradation of polycyclic aromatic hydrocarbons in aged subsurface soil using integrated persulfate oxidation and anoxic biodegradation

[Display omitted] •Integrated PS oxidation and anoxic biodegradation of PAH in subsurface soil was investigated.•Soil bacterial abundance was negatively impacted by PS, but that can be restored.•Both PS oxidation and anoxic biodegradation contributed to PAH removal in the soil added 1% of PS.•PAH removal was primarily attributed to PS oxidation in soil added 1% of PS.•Combined treatment was more efficient for PAH removal than either one alone in the soil added 1% of PS. Coupling chemical oxidation and biodegradation to remediate polycyclic aromatic hydrocarbons (PAHs) contaminated soil has gained great attention in recent decades. However, there remains a knowledge gap concerning the integration of persulfate oxidation and anoxic biodegradation of PAHs in subsurface soil. In this study, the potential of integrated persulfate oxidation and anoxic biodegradation of PAHs in aged subsurface soil are investigated. Dynamic changes in the soil bacterial abundance and community composition are also examined. The soil bacterial abundance and community composition were negatively influenced following the application of different dosages of persulfate (e.g., 1% and 3% (wt/wt)), but these were found to be gradually restored after the depletion of persulfate. The bacteria that were capable of degrading PAHs under anoxic conditions were predominated by the phyla Proteobacteria and Firmicutes. The results also indicated an increasing trend in Firmicutes and a decreasing trend in Proteobacteria with increasing dosages of persulfate applied to the soil. The observations also suggested that the elimination of PAHs was primarily attributed to persulfate oxidation in the soil that received 3% (wt/wt) persulfate. However, persulfate oxidation and anoxic biodegradation were both responsible for the abatement of PAHs in the soil when 1% (wt/wt) of persulfate was applied. In addition, in the successful treatment (1% (wt/wt) persulfate), the integrated treatment was more effective in PAH removal than either one alone. The results of this study imply that integrated persulfate and anoxic biodegradation may be a promising alternative for the remediation of PAH contaminated subsurface soil.