Optimization of Environmental Conditions for Microbial Stabilization of Uranium Tailings, and the Microbial Community Response

Abstract

Uranium pollution in tailings and its decay products is a global environmental problem. It is of great significance to use economical and efficient technologies to remediate uranium-contaminated soil. In this study, the effects of pH, temperature, and inoculation volume on stabilization efficiency and microbial community response of uranium tailings were investigated by a single-factor batch experiment in the remediation process by mixed sulfate-reducing bacteria (SRB) and phosphate-solubilizing bacteria (PSB, Pantoea sp. grinm-12). The results showed that the optimal parameters of microbial stabilization by mixed SRB-PSB were pH of 5.0, temperature of 25°C, and inoculation volume of 10%. Under the optimal conditions, the uranium in uranium tailings presented a tendency to transform from the acid-soluble state to residual state. In addition, the introduction of exogenous SRB-PSB can significantly increase the richness and diversity of endogenous microorganisms, effectively maintain the reductive environment for the microbial stabilization system, and promote the growth of functional microorganisms, such as sulfate-reducing bacteria (Desulfosporosinus and Desulfovibrio) and iron-reducing bacteria (Geobacter and Sedimentibacter). Finally, PCoA and CCA analyses showed that temperature and inoculation volume had significant effects on microbial community structure, and the influence order of the three environmental factors is as follows: inoculation volume > temperature > pH. The outcomes of this study provide theoretical support for the control of uranium in uranium-contaminated sites.

Insights into remediation effects and bacterial diversity of different remediation measures in rare earth mine soil with SO42− and heavy metals

“…It was clear that abundant SRB in the system could increase the chance of contacting SO 4 2− , and the higher activity of SRB in the system was a key to transforming SO 4 2− rapidly ( Wang C. et al, 2022 ). When the population and activity of SRB are met at the same time, SRB can quickly and efficiently convert from SO 4 2− to H 2 S, and then, the H 2 S combined with heavy metal ions (Pb and Zn) to form stable compound precipitation (PbS and ZnS), so as to achieve the purpose of solidification of heavy metals in the REM soil ( Lv et al, 2022a , b ). For the collaborative remediation group with the addition of Ca(OH) 2 and SRB, the remediation effects of Pb, Zn, and Mn were as follows: the CM-M (from 5.15, 8.56, and 8.49 to 0.60, 0.17, and 0.76) > the CM-L (from 5.15, 8.56, and 8.49 to 0.75, 0.87, and 1.19) > the CM-H (from 5.15, 8.56, and 8.49 to 0.95, 0.32, and 1.30).…”

“…DNA was extracted from the REM soil under different treatments using a DNeasy PowerSoil Kit (QIAGEN, Germany) according to the manufacturer’s instructions. The V3–V4 region of the 16S rRNA gene was amplified by polymerase chain reaction (PCR) with primers 338F (5′-ACTCCTACGGGAGGCAGCAG-3′) and 806R (5′-GGACTACHVGGGTWTCTAAT-3′) ( Lv et al, 2022a , b ). Each sample was amplified with three technical replicates under the following conditions: 94°C for 5 min, and then 30 cycles of 94°C for 30 s, 56°C for 30 s, and 72°C for 45 s, and a final extension at 72°C for 7 min.…”

“…SRB can use SO 4 2− as electron acceptors to reduce SO 4 2− to S 2− . Then, S 2− can remove heavy metals in the water solution by synthesizing a variety of insoluble sulfides precipitation including PbS, ZnS, CuS, and MnS ( Lv et al, 2022a , b ). Previous studies concluded that SRB can effectively remove heavy metals (Pb, Zn, Cu, Cd, Cr, and U) in the water solution from acid mine drainage and sustainably improve the ecological environment ( Gu et al, 2021 ; Wang et al, 2021 ; You et al, 2021 ; Yang et al, 2021a ).…”

“…For example, Yang X. et al (2021) and Yang Z. et al (2021) inoculated SRB into a biological filter disk carrier, which can decline SO 4 2− concentration from wastewater systems by over 90% in 60 days ( Yang Z. et al, 2021 ). Lv et al (2022a , b) reported that the 99% of U(VI) was solidified by SRB when the initial concentration of U(VI) is about 5 mg/L ( Li J. et al, 2022 ). Therefore, the SRB was widely used to treat wastewater containing SO 4 2− and heavy metal contamination of soil ( Li J. et al, 2022 ).…”

Soil Microbial Stress Responses under External Chemical and Physical Environmental Stresses

“…In particular, the abundance of functional microorganisms such as Nitrogen spirochetes, Geobacteria, Desulfurization spores and Sterilization bacteria can always be maintained at a high level. [59] Most of the current studies have focused on changing the morphology of uranium in the soil or the way of binding to the soil to reduce its mobility or bioavailability in the environment. However, there are great challenges in the morphological variability of uranium in soils, the adaptability of microorganisms to environmental changes, as well as the stability of uranium fixation by microorganisms.…”