Study On Removal Method And Mechanism Of Petroleum Hydrocarbon Residue In Soil

With the development of modern industry,the problem of oil pollution to the soil environment is becoming more and more serious.In the process of oil extraction,transportation,storage and processing,there are often oil spills,leaks and other accidents,a large amount of oil into the soil environment,resulting in serious pollution.Among many remediation technologies of oil-contaminated soils,Bioremediation has the advantages of good effect,simple operation,no secondary pollution and low cost,and has become the most concerned repair method for domestic and overseas researchers.However,there are some problems in bioremediation that need to be explored.The related research shows that the degradation effect of oil is obvious in the early stage of repairing oil-contaminated soil by bioremediation,the removal effect of petroleum hydrocarbon is worse in the later stage of repair,resulting in the "lag period " of petroleum hydrocarbon degradation.Therefore,it is of great significance for deep removal and thorough purification of petroleum hydrocarbon to explore effective methods for removing petroleum hydrocarbon residue in soil.In this paper,four strains of oil-degrading bacteria were isolated from the oilcontaminated soil which was in the " lag period " of petroleum hydrocarbon degradation,and were screened out by using the inorganic medium with oil-hydrocarbon as the sole carbon source.According to the analysis of 16 SrRNA sequence,the 4 strains of oilhydrocarbon degrading bacteria were pseudomonas,bacillus,rhodococcus and rhodococcus.The degradation effect of the mixture bacteria on petroleum hydrocarbon was measured after the mixture bacteria were mixed in equal proportion.Degradation experiments show that the screened strains can degrade petroleum hydrocarbon pollutants,which can be used to repair petroleum contaminated soil.For aging oil contaminated soil,this study used repair methods such as maintaining soil moisture,adding nitrogen source,applying compost,adding surfactant,adding surfactant combined with degradation bacteria and so on.And the total petroleum hydrocarbon content,alkanes content and ammonium nitrogen content were determined along the course.In addition,the number of petroleum hydrocarbon degradation bacteria in soil,the microbial activity of degradable hydrocarbons,the structure of microbial communities and the change of diversity were measured for the stage 1 with the best remediation effect.The results show that maintaining soil moisture has the effect on the removal of petroleum hydrocarbons in soil containing compost,and in the soil of(Oil-contaminated soil + compost)and(Oil-contaminated soil + compost + bacteria),the degradation rate of petroleum hydrocarbon was 6.48% and 8.38%,respectively.It has no obvious remediation effect on the soil polluted by petroleum without compost.Adding nitrogen sources to the soil,adding surfactant A and adding surfactant A combined degradation bacteria had no obvious removal effect on petroleum hydrocarbon residues in aging oilcontaminated soil.In addition,maintaining soil moisture can promote the increase of the number of oil-hydrocarbon degrading bacteria in soil,enhance the utilization ability of microorganisms in soil with compost to petroleum hydrocarbon,and has no obvious effect on the activity of biodegradable hydrocarbon microorganisms in soil without compost.The results of high-throughput sequencing show that maintaining soil moisture has a significant effect on microbial community structure and microbial diversity.Maintaining soil moisture can increase the proportion of Acinetobacter and Pseudomonas,and decrease the proportion of Promicromonospora.For the oil-contaminated soil containing compost,maintaining soil moisture has failed to promote the growth and propagation of the dominant genus of the compost.The initial ammonium nitrogen content in the oil-contaminated soil is 8~12mg/kg,and maintaining soil moisture will reduce the ammonium nitrogen content below the detection limit,which promotes the utilization of ammonium nitrogen by microorganisms.