关键词: 土著菌群, 铀, 生物还原, 生物矿化, 机理分析

Abstract: In recent years, microbial technology for remediation of uranium-contaminated groundwater has attracted the attention of scholars, because of its advantages of low cost, self-reproduction, no ease to cause secondary contamination, and less disturbance to the environment. The mechanisms of microbial remediation include biosorption, bioaccumulation, bioreduction, and biomineralization. Among them, bioreduction and biomineralization were two promising methods that could be utilized in situ shortly. Previous studies had shown that adding organophosphate compound to uranium-contaminated groundwater may give rise to remediation mechanisms such as bioreduction and biomineralization. To explore the coupling mechanisms of these two methods mediated by the indigenous microorganism, β-glycerol phosphate disodium salt was added in this study to stimulate the indigenous microorganism to treat neutral artificial uranium-containing groundwater. In the control group, glycerol was added to stimulate the bioreduction activity of the microbes only. The results showed that the removal rate of uranium in the experimental group was more than 98%, and the removal efficiency and effect were better than that of the control group under the same condition. After 21 days of the experiment, the scale-like precipitation on the cell surface could be observed via SEM. XRD analysis confirmed that the products were CaU(PO4)2 and Mg(UO2)2(PO4)2?10H2O, which possessed excellent resistance against reoxidation. XPS also indicated the presence of U(IV) and U(VI) in the products. Mechanism analysis showed that β-Glycerol phosphate disodium salt activated both bioreduction and biomineralization microbial community. Dysgonomonas, Propionispora, Macellibacteroides, unclassified_Rhizobiaceae and unclassified_Rhodocyclacea may be involved in the reduction of U(VI), NO3-, and SO42-, and Acinetobacter facilitated the process of biomineralization. while Methyloversatilis and unclassified_Enterobacteriaceae may take part in the reduction of U(VI)-phosphate minerals. In the early stage of the reaction, bioreduction and biomineralization were both involved in the immobilization process, and biomineralization was the main mechanism. Subsequently, the formed U(VI) precipitate was gradually reduced to U(IV) precipitate by microorganisms. This work would provide a new theoretical insight for the research on the long-term stability of bioremediation of uranium-contaminated groundwater in the future.

Key words: indigenous microorganisms, uranium, bioreduction, biomineralization, mechanism analysis