Effects of electric field on microbial metabolism in petroleum-polluted soil: Insights from microbial function and carbon utilization characteristics

This study investigated how the electric field enhances microbial metabolism during bio-electrokinetic (BIO-EK) remediation and identified factors hindering sustainable pollutant degradation. The results showed that the degradation rate of total organic carbon (TOC) was higher in BIO-EK than in bioremediation and electrokinetic processes, by up to 2.22 and 1.54 times, respectively. Similarly, the degradation efficiency of total petroleum hydrocarbons (TPH) in BIO-EK was 1.58 and 1.81 times higher than in the bioremediation and electrokinetic groups. In BIO-EK, microbial biomass carbon (MBC) content was up to 6.13 times higher than in the bioremediation group, and dissolved organic carbon (DOC) content was 2.30 and 1.26 times higher than in the bioremediation and electrokinetic groups, respectively. This indicates that the electric field promoted the conversion of TOC to DOC, which was assimilated by microorganisms to generate MBC. The analysis of the structure and functional genes of soil microbial communities revealed that the electric field accelerated the degradation of key petroleum hydrocarbon components and the soil carbon cycle. However, degradation rates varied, and MBC and DOC levels declined in later stages, indicating discontinuous pollutant degradation. The analysis of the ratio of organic carbon derived from petroleum and soil sources (12Cp/12Cs) revealed intermittent use of petroleumderived carbon, potentially limiting the sustainable degradation of pollutants. The research results provide insights for improving BIO-EK remediation efficiency.