Study On Distribution And Characterization Of Cultivable Microorganisms In Interlayer Oxidized Zone Sandstone Deposit Uranium Of Shihongtan And Their Mineralization

Sandstone uranium deposit is the valuable and main resource of production of uranium. Study on the groups, distribution and biomineralization of microorganisms in the Shihongtan uranium deposit in Xinjiang province are the basis for knowing the theoretical mineralization and the explorative method at a biological angle.Objectives: Investigate the main cultivated microbe groups which take part in the cycling of carbon, nitrogen, sulfur, iron, oxygen and uranium. Research the relationship among the microorganisms and the mechanism of microorganisms in the mineralization in shihongtan sandstone uranium deposit. Methods: By using biological method, microorganisms in the Shihongtan uranium deposit in Xinjiang province were isolated and identified. The simulation experiment of the function of microorganisms during the formation of uranium deposit was investigated. The reductive experiment of uranium caused by sulfate-reducing bacteria(SRB) and the oxidizing experiment of uranium caused by iron bacteria, Thiobacillus, nitrifying bacteria and denitrifying bacteria were done by the water-rock-bacteria three-phase experiment system. Research the relationship among the microorganisms in reductive experiment. Results: l.SRB, iron bacteria, Thiobacillus, Nitrobacter, Nitrosomonas, nitrifying bacteria and Bacillus were isolated and identified from shihongtan uranium deposit. The distribution of microorganisms in different zones was controlled by the organic carbon content, the existing state and content of ferrous and ferric and uranium, and also controlled by the content of oxygen, the content of sulphate in groundwater. The distribution of SRB was controlled by the content of uranium and the organic carbon. The distribution of the main microbe groups in the subzones was different and the geochemical characteristics were obvious. From the oxidation zone, the incomplete oxidation zone, the redox transitional zone to the reduction zone, the quantities and species of bacteria was gradually decreased. The distribution of SRB was controlled by the uranium content and the organic carbon content. The characteristic distribution of SRB could be as a standard to differentiate transitional zone from uranium deposit. 2. The result of biomineralization and bleaching experimental system showed that SRB could absorb organic carbon as nutrition materials to grow, at the same time, could reduce SO₄^2- in the groundwater to generate H₂S, which could give rise to the rise to the rising of pH and the dropping of Eh and form the reduction environment beneficial to gather and precipitate U(VI), at last, uranium was reduced and precipitated. SRB could reduce U(VI) by absorbing it in the surface of bacteria. Iron reducing bacteria could reduce U(VI) to U(IV), too. The result of oxidizing experiment showed that Thiobacillus and Nitrobacter, Nitrosomonas could produce an acid environment that was helpful for bleaching U(IV), iron bacteria could produce Fe³⁺and then U(IV) was oxidized to U(VI) by Fe³⁺. These microorganisms combined with each other which effected on the bleaching-transition-deposit of uranium in uranium deposit. Conclusions: The microorganisms in shihongtan uranium deposit were diversity. The distribution of the main microbe groups in the subzones was different and the geochemical characteristics were obvious. The microbial diversity was the basis for biomineralization. They influence mutually and accelerated the substance cycling in uranium deposit, they are very important in the forming of uranium deposit.