| Uranium is a natural radionuclide that occupies an important position in the development of our nuclear industry and energy acquisition.There are many ways to access uranium resources,with uranium mining being particularly important.However,the uranium mining process produces many byproducts,such as waste rock or uranium tailings.Some of these by-products contain residual uranium,which enter the surrounding soil with rainwater and other means,and eventually enter the environment and affect people’s health and safety.As uranium is highly toxic chemically and radiologically,its presence in the soil for a long time causes serious soil contamination,so it is urgent to find an economical and environmentally friendly way to remediate uranium stressed soil.This thesis addresses the problem of uranium-stressed soils by using biochar-phytoremediation technology to carry out screening of biochar addition conditions and the mechanism of action of biochar-phytoremediation at the soil level.This provided theoretical help to solve the problem of remediating uranium-stressed soils.The results of the study are as follows:(1)In the study of adding biochar at different pyrolysis temperatures to uranium contaminated soil,and found that ryegrass grew better in the group with 700°C biochar addition and absorbed smaller amounts of uranium.The activities of soil urease and sucrase increased with the increase of biochar pyrolysis temperature.In the analysis of microbial communities,it was found that the C700 group had the highest number of microorganisms and the relative abundance of Actinobacteriota was significantly increased.The soil non-targeted metabolomics analysis showed that the main categories of differential metabolites in soil are Lipids and lipid-like molecules、Organic acids and derivatives、Organic oxygen compounds.In the metabolic pathway analysis,there were 16 significantly different metabolic pathways which were common to all groups,with the phosphotransferase system(PTS)pathway being more abundant.Benzoxazinoid biosynthesis,Renal cell carcinoma were the significantly different metabolic enrichment pathways unique under the C700 group.Proteobacteria were found to be the most significant microbial factor in the whole system by the RDA analysis.3E,12Z-Octadecadienal,L-Histidinol,and Methylenediphosphonic acid were metabolites that had the greatest impact on the whole system.(2)In the study of adding different levels of biochar to uranium contaminated soil,and the results showed that the most effective promotion of ryegrass growth was achieved when 1% wt biochar was added to the soil.The analysis of enzyme activities showed that four enzymes activities were significantly enhanced in the B-1% group,and sucrase and acid phosphatase activities were the highest.Microbial community diversity analysis showed that the B-1% group had a greater number of microorganisms.Chao index,Shannon index and Simpson index were all the highest in the B-1% group,indicating that this group had the greatest community richness and diversity.The relative abundance of the microbial communities Actinobacteriota and Myxococcota were significantly increased.The results of soil metabolomics analysis indicated that Lipids and lipid-like molecules、Organic acids and derivatives、Organic oxygen compounds remained the main classes of differential metabolites.ABC transporters were the most abundant metabolic pathway in terms of metabolite distribution.Noviherbasporillum 、 Gemmatimonas 、 Ellin6067 and Ramlibacter were the dominant species during the interaction of microorganisms and metabolites.In summary,adding 1%wt biochar with a pyrolysis temperature of 700°C to uranium-stressed soils had a better remediation effect.Actinobacteriota was a key microbial community that regulated plant resistance to adversity.Metabolites,such as lipids and organic acids,occupied an important position throughout the system. |
