Remediation Characterization Of Petroleum-contaminated Soil By Indigenous Microorganisms In Combination With Nitrogen Stimulation

Petroleum is one of the more common fuels used by human beings,and inevitably faces environmental pollution problems caused by spills during its development,transportation and utilization.Microbial remediation technology has become a popular research and development method for petroleum-contaminated soil remediation due to its advantages of being economical and efficient,and less likely to produce secondary pollution.The traditional microbial remediation technology for crude petroleum-contaminated land has long remediation cycle and unstable remediation,which seriously affects the effect of microbial remediation of petroleumcontaminated soil.Establishing a bioremediation system with good degradation effect,salinity resistance and sustainable operation is an inevitable requirement for the application of bioremediation technology.Petroleum hydrocarbons have hydrophobicity and low water solubility,and petroleum pollution destroys the appropriate carbon to nitrogen ratio required by microorganisms,which seriously affects the metabolism of microorganisms and brings difficulties to the bioremediation of petroleum-contaminated soil.Therefore,it is necessary to adjust the carbon to nitrogen ratio of the soil by enhancing the metabolism of microorganisms,so as to achieve the bioremediation effect of petroleum-contaminated soil.To address the above problems,this study aims to screen functional strains from petroleum-contaminated soils that are highly efficient in petroleum degradation and emulsification and can tolerate extreme environments,construct a simulation system for in situ activation of indigenous petroleum-degrading bacteria from petroleum-contaminated soils by means of biostimulation,identify key factors affecting the biostimulation effect,investigate the mechanism of petroleum hydrocarbon degradation and nitrogen utilization,optimize the operation parameters for remediation of petroleum-contaminated soils,and realize the bioremediation effect of petroleum-contaminated soils.The main findings of this paper are as follows The main research contents and conclusions of this paper are as follows:(1)In order to better target the remediation of petroleum-contaminated soil,a strain with petroleum hydrocarbon degradation function.was screened from the petroleum-contaminated soil in Dongying in situ and named Bacillus sp.Z-13 after identification and comparison.the optimum salinity range for the growth of this strain is 0-8%,temperature tolerance range 2545℃,and pH adaptation range 6-9.(2)In order to analyze the mechanism of the strain to promote the degradation of petroleum hydrocarbons,the emulsification function of Bacillus sp.Z-13 was analyzed,and it was found that strain Z-13 also has the function of producing biosurfactant,and the emulsification efficiency was 55%.The biosurfactant was characterized and identified as a lipid biosurfactant.The biosurfactant was analyzed for tolerance and its optimum salinity range was 0-8%,temperature tolerance range was 15-45℃,and pH adaptation range was 5-9.(3)To promote the degradation of petroleum hydrocarbons,a nitrogen source was applied to the soil.The results showed that the combination of ammonia nitrogen and strain Bacillus sp.Z-13 was the most effective,and 890 mg/kg of petroleum hydrocarbons could be removed from the soil,with a removal rate of 59%.The abundance of functional petroleum hydrocarbon degrading bacteria represented by Bacillus sp.in the restored soil increased substantially and gradually became the dominant strain.The ammonia nitrogen stimulation was mainly through the promotion of ammonia nitrogen assimilation and and nitrification pathways of indigenous microorganisms,which led to the degradation of petroleum hydrocarbons.In conclusion,this study screened a petroleum hydrocarbon degrading strain with environmental tolerance,which can also produce biosurfactant.Its emulsification of petroleum hydrocarbons increases the contact area between petroleum hydrocarbons and microorganisms,and ammonia nitrogen stimulation of petroleum hydrocarbon degrading bacteria accelerates the degradation of petroleum hydrocarbons,which has a broad application prospect in petroleum contaminated soil remediation in the future.