Study On Bioremediation Of BDE-47 Contaminated Soil

2,2',4,4'-tetrabromodiphenyl ether(BDE-47)as a new type of persistent organic pollutants PBDEs,it was detected in a variety of environmental media and organisms.BDE-47 has developmental neurotoxicity,thyroid toxicity,immunotoxicity and certain carcinogenic effects.The soil is one of the ultimate destinations for BDE-47,which is the gathering and release of BDE-47 contaminants.Microorganisms as an important biological component in the soil environment medium,Microbiologicalr behavior plays an important role for BDE-47 migration and transformation.Microbial remediation technology as one of the main ways of soil remediation technology,which is favored by the majority of researchers.Therefore,2.2',4,4'-tetrabromodiphenyl ether(BDE-47)was selected as the research object,the chernozem and yellow brown soils were used as background soil,the experiment as far as possible to simulate the different types of pollution soil ecological environment,then to analyze effect about additon of BDE-47 and degradation strains 4-1 on soil microbial population and community structure.To determine the repair effect through determining BDE-47,choose the better remediation effect soil to carry out the study of immobilized degrading bacteria repair,combined with soil physical and chemical properties,microbial quantity,microbial community structure to complete the evaluation of microbial remediation effect of contaminated sites.The research results show that,(1)The addition of BDE-47 and degrading bacteria 4-1 had little effect on the physical and chemical properties of yellow brown soil.The water content,pH,organic matter,total nitrogen,total phosphorus and total potassium were not significantly different in each simulation system.For the chernozem,the addition of BDE-47 and the degrading bacteria had affected directly on soil total nitrogen and total phosphorus,Which had a significant effect on total nitrogen content.Through the analysis of BDE-47 content showed,The degradation ability of BDE-47 in chernozem is weak,added degrading strain was not obvious effect for removing BDE-47.There was strainsdegrading BDE-47 bacteria in yellow brown soil,simulated 90 days,the degradation rate was 24.53%.The degradation of BDE-47 was increased by the addition of degrading bacteria,and the degradation rate was 39.77%.(2)In the chernozem simulation system,the addition of BDE-47 and degrading bacteria have significant effect on the microbial quantity.According to the high-throughput sequencing structure and clustering analysis,the addition of degrading bacteria 4-1 have a great effect on the microbial community structure in chernozem.The Chao1,Ace,Shannon and Simpson indices in the simulation systems showed,the total number of microbial species showed a decreasing trend with the simulation,the addition of BDE-47 and degrading strains reduced the diversity of microbes in chernozem.The microbial community in chernozem belongs to 28 gates,57 classes,116 orders,212 families,and 302 genera.Acidobacteria,Proteobacteria and Actinobacteria are the dominant bacteria in the chernozem.The addition of BDE-47 and degrading bacteria can promote Acidobacteria,chloroflexi and Verrucomicrobia in chernozem,but on the contrary,it can reduce Proteobacteria,Nitrospirae.(3)In the yellow brown soil simulation system,the addition of BDE-47 inhibited microbial quantity in the early stage of simulation,but microbial quantity increased significantly with the simulation.According to the high-throughput sequencing structure and clustering analysis,The addition of BDE-47 and degrading bacteria 4-1 had little effect on the microbial community in the beginning.The main reason for the change of microbial community structure during the simulation process.Through analyzing the diversity index of each simulation system,the total number of microbial species in each simulation system showed an increasing trend with the simulation,but the addition of BDE-47 and degrading strains reduced the diversity of microbes in yellow-brown soils.The microbial community of yellow brown soil belongs to 19 gates,53 classes,1116 orders,226 families,348 genera.Acidobacteria,Proteobacteria and Actinobacteria are the dominant bacteria in the yellow brown soil.The abundance of microbial bacteria in yellow brown soil did not show significant changes with the addition of BDE-47 and degrading bacteria.And the simulation process is the main reason for the change of microbial relative abundance.(4)In the process of simulated restoration of chernozem and yellow brown soil,the relative abundance of more than 1% can be found in taxonomy,microorganism and soilphysical and chemical properties showed a certain correlation.Agromyces,Arthrobacter and Nocardioides showed a significant negative correlation with soil organic matter content and total potassium content.Haliangium and Reyranella showed a significant negative correlation with soil water content and total phosphorus content,And positively correlated with soil organic matter content.(5)Immobilization technology was used in the repair process,the BDE-47 degradation rate was 36.94% in the simulated system repaired for 90 days.The immobilized pellets have an effect on the yellow brown soil physical and chemical properties during the simulation process,pH,organic matter and total nitrogen showed a decreasing trend,total phosphorus and total potassium showed an upward trend.The addition of immobilized strain 4-1 has not significant effect on the microorganisms number in the beginning,the microorganisms number showed a significant increase as the simulation(p < 0.05).In the simulation process,The descending trend of Proteobacteria was obvious in yellow brown soi,it was descend about 11%.While Actinobacteria increased significantly,it was up about 23%.The trend of Acidobacteria was not obvious.