Effects Of Biodegradation On Saturated Hydrocarbon Biomakers And Polycyclic Aromatic Hydrocarbons In Crude Oil

To reveal the effects of the microbial degradation process on the effectiveness of biomarkers and PAHs parameters in crude oil and screen out the biomarker parameters which could be used to characterize the sedimentary environment,the characteristics of biomarkers of homologous crude oil were analyzed through maturity and the sources of organic matters in this study,as well as the molecular markers parameters analyzed by PAHs source.Based on the previous studies,3 normal crude oil samples obtained from Changqing oil field were applied in simulated degradation tests by using high efficient degradation bacteria which were separated from the contaminated soil and crude oil,to investigate the resistance ability of biomarkers and PAHs to the micro-biological degradation process,and the effectiveness of different biomarker parameters and PAHs source parameters in crude oil was discussed.The following conclusion was obtained according to the research result:?1?The highest degradation level in the simulated degradation process toward crude oil by microorganism was 4,the same as mediate microbial degradation level.?2?With the increase of the microbial degradation level in the natural crude oil degradation process and the simulated crude oil degradation process,the ratio of parameters Pr/nC17,Ph/nC18 and 8??H?-homodrimane/8??H?-drimane increased,while Pr/Ph and 8??H?-homodrimane/8??H?-drimane showed the opposite tendency.?3?Under the strong microbial degradation condition,the maturity parameters C₂₉??/???+???increased while the parameter C₃₁22S/?22S+22R?stayed stable in the degradation process;parameter Ts/?Ts+Tm?changed when affected by the mediate degradation process.The parameters ???20RC27 and aaa20RC₂₈ decreases with the increase of biodegradation degree.The ability to resist biodegradation of ???20RC27 and aaa20RC₂₈ was weaker than that of aaa20RC₂₉.Homohopane isomers of selective biodegradation changed with the variety of carbon numbers.When the microbial degradation level reached 7,the C₃₁-3322S/?22S+22R?stayed stable while volatility emerged in C34-3522S/?22S+22R?.?4?Low and mediated microbial degradation could affect alkylnaphthalene parameters and change the composition of three fluorene and methyl fluorene series compounds.9-MP in methylephenanthrene showed the strongest ability to resist the microbial degradation,and the methylephenanthrene index changed only when oil went through intense microbial degradation process.?5?Low and mediated microbial degradation could affect the ratio of oil PAHs molecular markers to some degree and result in the increase of ratio of Ring456/TPAH,but the PAHs source analysis would not be affected.Crude oil went through severe microbial degradation,where 1,7/?1,7+2,6?DMP would decrease and Ring456/TPAH would increase,thus to change analytical source result.