Study On Anaerobic Biodegradation Of Gasoline Components In Unsaturated Soil

There are more and more accidents reported about leakage of petroleum productsfrom gas station, it has become an important environmental issue. Unsaturated zone isnot only the path of leaked oils accessing the underground water/atmosphere, but alsothe parclose that protects the underground water/atmosphere from being contaminatedby leaked oils. Therefore, studying the gasoline microbial degradation mechanism invadose soil, could offer scientific basis of underground water/atmosphere protectionin underground storage tank sites. This experiment regards gasoline as the targetedpollutant and unsaturated deep soil as research object, carried out the study as follow:(1) soil microorganism abundance and community diversity in typical petroleumleakage sites;(2) effect of nitrate as electron acceptor on anaerobic biodegradation ofgasoline components in unsaturated soil;(3) effect of sulfate as electron acceptor onanaerobic biodegradation of gasoline components in unsaturated soil.The results of real-time quantitative PCR show that, microorganism abundanceof topsoil is higher than deepsoil (1-2magnitudes) in the uncontaminated contrast siteand typical petroleum leakage site. RPD analysis results based on clone library revealthat, bacterial community diversity of the oil-leaked site is obviously lower than thecontrast site, the community diversity of topsoil in contaminated place is absolutelyhigher than the subsurface soil. The sequencing results of AS and BS fromcontanminated deepsoil are respectively97and95, most of Betaproteobacteria, moreover, the gene sequence of deepsoil CKS in uncontaminated contrast site includes7bacteria groups (class).After180days anaerobic culture, there is no significant change of concertrationof mono-aromatic hydrocarbons in contrast treatment by no adding nitrate (SGN0),but the degradation efficiency of TPH(C6-C9) and TPH(C10-C12) is high, reaching torespectively33%and37%. Toluene, ethylbenzene, TPH (C6-C9) and TPH (C10-C12)in the treatments that adding nitrate (SGN40, SGN200, SGN1000) degradesignificantly, the rates are10-47%,22%-82%,42%-57%and39%-52%respectively. The more nitrate added, the higher degradation efficiency. Even so, the concertrationof other mono-aromatic hydrocarbons do not change significantly. Compared by thecontrol treatment, the concertration of other mono-aromatic hydrocarbons such astoluene, ethylbenzene, xylene,1,2,4-trimethybenzene, sec-butylbenzene, TPH (C6-C9)and TPH (C10-C12) do not change significantly in the treatments that adding sulfate(SGS40, SGS200, SGS1000).