Hydrocarbons removal and microbial community succession in petroleum-contaminated soil under hydrogen peroxide treatment

Abstract

Chemical oxidation as a pretreatment step coupled with bioremediation for petroleum-contaminated soil may pose serious impacts on indigenous microorganisms and the available nutrients. Petroleum-contaminated soil were treated by hydrogen peroxide (H₂O₂) at initial concentrations of 105 mM (HH), 21 mM (HL), and 105 mM in three equal amounts (HT) without adding any external catalyst. The contents of total petroleum hydrocarbons (TPH) and dissolved nutrients (total organic compounds, nitrogen, and phosphate), and the indigenous bacteria community succession (analyzed by high-throughput sequencing of 16S rDNA) were investigated over 50 days. Compared to the control treatment without H₂O₂ addition, H₂O₂ treatments for the petroleum-contaminated soil significantly promoted the TPH removal especially in the first 4 days and impacted the contents of dissolved nutrients. Both of chemical oxidation and nutrients contributed to microbial community structure changes in alpha diversity. Although the soil microbial community structure had undergone significant changes after different chemical oxidation pretreatments, Firmicutes, Proteobacteria, Gemmatimonadetes, and Actinobacteria were the main bacterial phyla. Compared with adding H₂O₂ at one time, H₂O₂ added in stepwise was beneficial to indigenous bacterial diversity recovery and TPH removal. H₂O₂ oxidation treatments showed a great influence on the microbial community structures in the start-up stage, while recovery time rather than the oxidation treatments presented greater effects on the composition of the microbial community structure with the incubation time extended. Therefore, adding H₂O₂ as pretreatment for petroleum-contaminated soil showed little effect on the structure of soil indigenous microbial community from a long-term scale, and was conducive to the continuous removal of TPH by indigenous microorganisms.

Keywords: Chemical oxidation; Indigenous bacteria; Microbial diversity; Nutrient; Petroleum hydrocarbon.