Degrading of petroleum contaminated soil by injected mixed oil-degradation bacterial strains

Some oil-degradation bacterial strains,designated as A6,A5,D4,F1 and F2,were screened and isolated from oil contaminated soil at Huaqing Oilfield of Gansu Province,China.Different amounts of mixed bacteria were injected into soil polluted by crude oil,and the influences of petroleum degradation rates,including dehydrogenises activity,soil solution electrical conductivity and nitrogen-phosphorus content were studied.The results show that the oil degradation rates with high-efficiency degradation bacteria are higher than the rates without degradation bacteria.After 48 d,with oil contents of 50 g/kg in the contaminated soil,the oil degradation rates with addition of 2%,4% and 8% bacteria reach 68.01%,80.42%,78.47%,respectively,which clearly improves the biodegrading efficiency higher than CK degradation rate(40.34%).The degradation efficiency of the case with 4% mixed bacteria is the highest.In organic fertilizer,nitrogen and phosphorus contents are the main factors affecting oil degradation rate,only appropriate amount of the organic fertilizer could achieve the best degradation efficiency,e.g.the 4% additive amount of organic fertilizer.As revealed by GS-MC, the degrading appears that after being treated with the mixed bacteria, the higher molecular weight n-alkanes are degraded into lower molecular weight n-alkanes, and the n-alkanes in odd-numbered carbon are degraded into n-alkanes in even-numbered carbon. As well as, isoprenoid alkanes appear a significant degradation in crude oil under the action of mixed bacteria after 7 d. The mixed bacteria can promote the transition pentacyclic triterpenes fromless stable configuration to stable one.