Objective Soil contamination represents a critical environmental challenge associated with oil extraction and transportation. Traditional microbial remediation methods frequently demonstrate limited efficacy in addressing oil-contaminated soils. The introduction of exogenous oil-degrading bacteria as well as surfactants which enhance oil dispersion, offers a more effective approach for microbial remediation of oil-contaminated soils.

Method A 40-day remediation experiment was conducted on soil contaminated with 3 wt% oil using a mixed system of TX-100/SDS surfactants and microbial agents. The changes in petroleum hydrocarbons and microbial community composition were analyzed by gas chromatography-mass spectrometry (GC-MS) and 16S rRNA gene sequencing methods, and changes in enzyme activity was also tested. Four groups were included in the study, which were a blank soil control group (E1), a microbial agent group (E2), a surfactant group (E3), and a combined surfactant and microbial agent group (E4).

Result Over a 40-day period, the E4 demonstrated the highest oil degradation rate, achieving 65%. This rate was similar to that of the E3 and exceeded the 58% degradation rate observed in the E2. The oil degradation rates and speeds in E2 to E4 were significantly higher than those in E1. The relative abundance of alkanes in E2 to E4 was 50%, marking a 38 percentage points reduction compared to the initial oil alkane composition. Similarly, the relative abundance of phenols decreased. Oil-degrading bacteria such as Pseudomonas, as well as members of the phyla Proteobacteria, Actinobacteria, and Firmicutes, were detected in the E4, though the enrichment of introduced bacteria was not significant. Dehydrogenase activity in the E4 exhibited a steady increase, aligning with the trend of alkane degradation. However, polyphenol oxidase activity did not show significant changes in E2 to E4, likely due to the challenges in degrading complex aromatic compounds in oil-contaminated soils, which might have limited the enzyme's activity.

Conclusion The synergistic interaction between TX-100/SDS surfactants and microorganisms significantly enhances the microbial remediation efficiency of oil-contaminated soils. The strategic application of surfactants promotes the rapid degradation of alkanes by the inoculated bacterial community during the dominant growth phase.