Bioremediation Process And Microbial Functional Response Of Petroleum Hydrocarbon Contaminated Soil In Saline-alkali Environment

The Yellow River Delta is a typical oil-polluted saline-alkali region.A large amount of petroleum hydrocarbons and organic pollutants are discharged into the soil with various human activities every year.Biostimulation,Biostimulus-enhanced combined remediation systems have been widely used in the remediation of oilcontaminated sites at home and abroad.Current studies mainly focus on the influencing factors of bioremediation and hydrocarbon degradation,but little attention has been paid to the changes of soil microbial community diversity in the actual remediation process.In our study,a field remediation experiment of salinealkali oil-contaminated soil in the Yellow River Delta was carried out by means of biostimulation(BS)and biofortification(BA)combined with stimulation.The experiment period was 3 months.The purpose of this study is mainly in order to define the bioremediation in the process of the change of the microbial flora structure mechanism,and the soil microbial functional gene changes over time trend,combined with the bioremediation of soil physical and chemical indicators further study of environmental factors in the process of petroleum contaminated soil microbial structure and function of the corresponding relationship,at the same time,In this thesis,the change rules and differences of microbial structure and function under different soil depths(30cm,60 cm,90cm)were studied in the process of remediation,and the differences of microbial community structure and function over time during the application of different bioremediation technologies were clarified,as well as the differences of microbial structure and function under different soil depths.This study provides a theoretical basis for analyzing the biological metabolic mechanism of soil microbial degradation of petroleum hydrocarbons.The main results are as follows:(1)The remediation effects of petroleum contaminated soil under different remediation levels were discussed.The degradation rate of biofortification combined with stimulation was 57.32% and 46.49% respectively.Bioremediation significantly increased the degradation rate of petroleum hydrocarbon and the number of soil microorganisms and degrading bacteria.The number of microorganisms and hydrolytic bacteria in 30 cm was the highest in each restoration,and the degradation rate of petroleum hydrocarbon was 30 cm > 60 cm > 90 cm.(2)Based on the analysis of microbial diversity level,a total of 13149 OTU samples were obtained,including OTU of BS were 8919,OTU of BA were 1713 and CK were 8488.Alpha diversity was significantly reduced under combined restoration,while it was significantly increased under biological stimulation restoration.The diversity of microbial species was more abundant in 30 cm soil.(3)At the level of microbial community structure,the difference contribution of microbial community structure in different restoration was analyzed.The results showed that there were significant differences in the community structure under the three types of restoration,and the microbial community structure of biological stimulation was more similar to that of natural stacking Acinetobacter,Defluviicoccus,Dietzia,KCM-B-112 and Marinobacter were the common dominant bacteria in the three groups.Defluviicoccus 、 Sulfurovum were endemic to biostimulation repair.The endemic bacteria of combined biofortification and stimulation restoration were Actinomadura and Streptomyces,among which Streptomyces was introduced exogenous bacteria and became the dominant bacteria in oil-contaminated soil in the early stage.Marinobacter was the dominant bacterium at 30 cm,Sulfurovum at 60 cm,and KCM-B-112 at 90 cm.(4)In environmental factor level analysis of the correlation between microbial community structure and environmental factors,the results show that the soil microbial community structure and environmental factors influence,the soil microbial community distribution by carbon source at the same time,environmental factors and interaction effects between species,including carbon source are the main factors,environmental factors have synergy of microbial community diversity.(5)The functional response of microorganisms in different restoration processes was analyzed from the functional prediction level.The results showed that the relative abundance of hydrocarbon,amino acid,energy metabolism and other major metabolic processes were increased by biological stimulation and biofortification combined with stimulation,and the relative abundance of degradation function of organic pollutants was enhanced.Different restorations may affect the accumulation of functional microorganisms.The relative abundance of microbial community structure and function varied greatly at different depths.Aerobic metabolism was the main degradation pathway in 30 soils,and anaerobic metabolic activities such as nitrogen respiration and nitrate respiration were more active in the middle(60 cm)and deep(90 cm)layers.