Remediation of petroleum contaminated soil by persulfate oxidation coupled with microbial degradation

Abstract

This study was conducted on soil polluted with high concentrations of crude oil (12,835 ± 572.76 mg/kg) with different dosages of persulfate (PS) coupled with hydrocarbon-degrading mixed bacteria (including Enterobacteriaceae, Stenotrophomonas, Pseudomonas, Acinetobacter, and Achromobacter) obtained from long-term oil-contaminated soil. The interaction among total petroleum hydrocarbons (TPH), soil parameters, and microbial communities during a 187-d combined remediation process was evaluated. The result showed that the TPH removal of 1% PS oxidation combined with bioremediation was 80.05%; this was 4.88% and 20.94% higher than that of bioremediation and 1% PS oxidation combined with natural attenuation. This is a result of 1%PS stimulated enzyme secretion and dissolved organic carbon content, especially fulvic acid, improving TPH mobility and bioavailability in soil. Furthermore, introducing mixed bacteria after oxidation further increased enzyme activities and TPH-degrading ability, thus promoting carbon substrate conversion and biodegradation rate. Conversely, the excessive oxidation of 3% and 5% PS had a negative impact on the soil environment and microbial diversity resulting in lower TPH degradation (36%-57%). High-throughput sequencing revealed that the abundance and diversity of soil bacteria decreased in all remediation groups compared to those in the pristine soil. Redundancy analysis showed that the main factors affecting 1% PS oxidation combined with bioremediation during subsequent microbial remediation were pH, cation exchange capacity, and lipase activity, which may indirectly influence TPH biodegradation by increasing the abundance of genus Immundisolibacteraceae, Comamonadaceae, and Acinetobacter. This study provides data on in situ chemical oxidation integrated with the bioremediation of petroleum hydrocarbon-contaminated soils.