The Investigation Of Rhizosphere Effect And Microbial Community In E-waste Soil

With the rapid development of electronic equipment and relevant technologies,the waste electrical and electronic equipment,such as discarded personal computers,televisions,refrigerators and cell phones,has become one of the fastest increasing waste streams in the world.For the electronic waste disposal,China started late and there are still insufficient in the management of this field.As the result,electronic waste pollution in China has caused serious environmental problems to be addressed urgently.Polyhalogenated aromatic hydrocarbons have been widely applied in the production of various electronic products because of their low cost and good insulation and flame retardant effect,but due to their durability against degradation in the natural environment and their long-range mobility in environmental media,its release caused serious ecological effects.Therefore,the control of polyhalogenated aromatic hydrocarbon pollution plays a critical role in e-waste pollution management.In order to remediate electronic waste-contaminated soil,the principle of remediation based on plant-microbial combination can provide a better theoretical and methodological framework in future perspective of sustainable development and ecological civilization construction.The interaction of energy and nutrition between plant roots and rhizosphere microbiota establishes a critical link between plants and microbes.Rhizosphere ecology is not only closely related to the growth of plants,but also involves a complex network of plants and rhizosphere microorganisms including symbiosis,parasitism,competition,and a series of ecological effects.Therefore,the study of rhizosphere ecology is not only the critical focus of the interdisciplinary study on environmental science-pedology-botany-microbiology,but also has great significance for the explanation of the plant-microbial combined remendiation mechanism.With the deepening research on the relationship between microbial communities and the environment,there emerged the microbiome study whose objective is not only the microbiota but also includes the surrongding environmental conditions and their habitat where the microorganisms are located.Therefore,the study under the definition of the microbiome places more emphasis on the interaction and co-evolution of the environment,the host,and the microbes and have a better insight into rhizosphere effect.In this study,we investigate the distribution of polyhalogenated aromatic hydrocarbons,including polyhalogenated biphenyls?PCBs?and polybrominated diphenyl ethers?PBDEs?,in the electronic waste dismantling sites and surrounding forest soils;besides,we investigate the functional microbial community through Stable Isotope Probing?SIP?,and reveal the ecological network in rhizosphere and soil microbiome.In this study,shrub species caused a greater difference in the distribution of PCBs and PBDEs than PCBs and PBDEs distribution in rhizosphere and soil.The wood samples show the opposite trend.Simultaneously,the microbial community network analysis in this study demonstrated the interaction model between microorganisms in the rhzosphere and soil microbial communities.Compared to the soil microbial community network,the module of rhizophere microbial community network shows a more complex interaction between members.The interconnections are tighter,and the modularity medium value is higher,the average path distance is longer.In addition,¹³C stable isotope probing technology was applied here for obtaining the relevant taxonomy information and community structure characteristics of functional microbial communities,and showcase the e-waste soil functional microbial communities in situ.In summary,in this thesis we elaborate the rhizosphere effect in e-waste soil through polyhalogenated aromatic hydrocarbons distribution,functional microbiota investigation and microbial ecological network structure comparison between rhizosphere and soil.This work would provide meaningful references for future phyto-microbial remendiation study.