Comprehensive response of Medicago sativa when used to ecologically remediate a site in the eastern region of the Loess Plateau contaminated with different concentrations of oil

In order to clarify the comprehensive response of Medicago sativa when used to ecologically remediate a site in eastern Gansu Province that contained oil-contaminated soil, a 3 month ecological site remediation program was implemented at the Sludge disposal station of a secondary oil production plant affiliated to the Petro china Changqing Oilfield Company. The growth responses and physiological indicators of Medicago sativa under stress at different total petroleum hydrocarbons (TPH) concentrations were determined. We found that plant height, root length, plant underground biomass, amount of TPH degrading bacteria, and the TPH degradation rate of Medicago sativa decreased as the TPH concentration increased (P < 0.05). The 7% TPH concentration significantly reduced the rhizosphere BCF index, but there were no significant differences between the 1% and 4% concentrations (P > 0.05). The activities of antioxidant enzymes showed a single hump-shaped tend, and the greatest antioxidant enzyme activity was observed when the TPH concentration was 5%. All the results indicated that the TPH concentration should not exceed 5% when Medicago sativa is used to ecologically remediate sites containing oil-contaminated soil in the eastern region of the Loess Plateau.