Synergistic Remediation of Aged Oil-Contaminated Soil by Plants and Degrading Microbial Consortium
This study investigated the synergistic remediation of aged oil-contaminated soil collected from an oil well in Yanchang, northern Shaanxi, China, with an initial total petroleum hydrocarbon (TPH) concentration of 17.1 g·kg⁻¹, exceeding the second-class land use screening value (4,500 mg·kg⁻¹) by approximately 3.8-fold. Indigenous high-efficiency degrading strains were screened and a microbial consortium was constructed. Pot experiments were conducted to compare the TPH degradation efficiencies and soil property changes under plant, microbial, and combined plant-microbial remediation. The consortium MC-5 (SDB1:SDB2:SDB3:SDB4 = 1:1:0:3) exhibited the highest TPH degradation rate of 83.46% in liquid culture. In soil, combined remediation with ryegrass (Lolium perenne) achieved a TPH degradation rate of 60.93%, significantly higher than the control (CK) by 54.26 percentage points. The consortium also degraded recalcitrant resins and asphaltenes by 49.44%. The microbial consortium played a dominant role, contributing 63%–69% to TPH removal, whereas plant contribution was only 2%–12%, primarily in the later stage. Addition of rhamnolipid biosurfactant enhanced the combined remediation, increasing TPH degradation by 7.05 percentage points compared to non-amended treatments. These findings provide insights into the mechanisms of plant-microbial synergy and offer theoretical and practical guidance for bioremediation of petroleum-contaminated soils.