Microbial community responses to soil parameters and their effects on petroleum degradation during bio-electrokinetic remediation

Abstract

This study evaluated the interactions among total petroleum hydrocarbons (TPH), soil parameters, and microbial communities during the bio-electrokinetic (BIO-EK) remediation process. The study was conducted on a petroleum-contaminated saline-alkali soil inoculated with petroleum-degrading bacteria with a high saline-alkali resistance. The results showed that the degradation of TPH was better explained by second-order kinetics, and the efficacy and sustainability of the BIO-EK were closely related to soil micro-environmental factors and microbial community structures. During a 98-d remediation process, the removal rate of TPH was highest in the first 35 d, and then decreased gradually in the later period, which was concurrent with changes in the soil physicochemical properties (conductivity, inorganic ions, pH, moisture, and temperature) and subsequent shifts in the microbial community structures. According to the redundancy analysis (RDA), TPH, soil temperature, and electric conductivity, as well as SO42−, Cl−, and K+ played a better role in explaining the changes in the microbial community at 0–21 d. However, pH and NO3− better explained the changes in the microbial community at 63–98 d. In particular, the dominant genera, Marinobacter and Bacillus, showed a positive correlation with TPH, conductivity, and SO42−, Cl−, and K+, but a negative relationship with pH and NO3. Rhodococcus was positively correlated with soil temperature. The efficacy and sustainability of the BIO-EK remediation process is likely to be improved by controlling these properties.