Investigation On Natural Radioactivity Level Of Uranium Mining And Milling Tailings Pond And Its Effect On Bacterial Diversity

Although through decommissioning governance,uranium mining and milling tailings pond as a potential compound pollution source of radionuclide and heavy metals,the radioactive waste residue in the pond may migrate and diffuse due to natural or human factors,thus affecting the ecological environment safety and public health of the pond area and its surrounding areas.Therefore,the natural radioactivity level of a uranium mine and smelting tailings pond and its surrounding area in Xinjiang was investigated in this study.According to the investigation results,the spatial distribution characteristics of soil natural radionuclides,the ambient dose equivalent rate H^*(10),and soil surface radon exhalation rate were discussed,and the natural radioactivity level and control effect of the tailings pond and its surrounding area were evaluated.For further study the soil ecological environment inside and outside the tailing pond,the physical and chemical properties and some metal/metalloids content of the soil inside and outside the tailings were analyzed,and combined with the soil bacterial community 16S r RNA high-throughput sequencing results,using bioinformatics methods are discussed,the influence of different environmental factors on the bacterial community diversity parsing the bacterial community response to the environmental factor,excavate the potential relationship between bacterial community and environmental factors.The results show that the soil radionuclide activity concentration at different depths of the tailings pond and its surrounding area is ²³⁸U:5.17-153.71 Bq kg^-1,²²⁶Ra:10.93-203.45 Bq kg^-1,²³²Th:10.45-190.44 Bq kg^-1,⁴⁰K:190.47-1792.36 Bq kg^-1,and the estimation range of soil surface radon exhalation rate ranged from 27.32 to 61.08m Bq m^-2 s^-1,which are lower than the limits of national relevant standards,and also within the background range of natural soil radioactivity in Xinjiang;The ambient dose equivalent rate H^*(10)was also in the range of absorbed dose rate of air caused by permeating radiation in this region(73.6-166.2 n Gy h^-1).Radionuclide ²³⁸U and ²²⁶Ra have similar spatial distribution characteristics,and the activity distribution characteristics of the same radionuclide are similar at different depths.On the whole,the activity concentration of ²³⁸U,²²⁶Ra,and ⁴⁰K of radionuclides decreased with the increase of soil vertical depth,while ²³²Th was on the contrary.Through the processing and statistical analysis of the high-throughput sequencing data of soil bacteria in the study area,it was found that there was no significant difference in the richness and diversity of soil bacterial community inside and outside the tailings pond,while there was a significant difference in the structure of soil bacterial community,However,through LEf Se analysis,it was found that the number of evolutionary branches of bacterial communities with significant differences in the surface soil inside and outside the tailings pond was very small.The unclassified bacteria of Streptomyces,Salinimicrobium,and Rhodothermaceae with significant differences can be used to screen microbial indexes of soil environmental quality changes in tailings ponds.Redundancy analysis(RDA)results show that the environmental factor of Distance and Zn were the main reasons for the difference in bacterial community structure in the tailings pond.The results of this study show that the decommissioning governance of tailings pond has reached the expected effect from the perspective of radiation environment protection,which provides a scientific basis and data reference for the safety assessment of tailings pond,soil ecological environment protection,and soil radioactive pollution prevention and control.At the same time,from the perspective of microecology,this study provides insight into the impact of tailings pond on soil bacterial community inside and outside the reservoir area and also provides a research basis for screening microbial indicators of soil environmental quality changes.