硒,79Se,是在未来的深层地质处置库(DGR)中处置的放射性废物中最关键的放射性核素之一。这里,我们研究了在DGR相关条件下膨润土微生物群落对Se(IV)生物还原产物同素异形转化的影响。此外,评估了膨润土微生物种群中硒修正依赖性的变化。水饱和膨润土的微观世界中掺入了细菌财团,用亚硒酸盐处理并厌氧孵育六个月。X射线吸收光谱的组合,电子显微镜,拉曼光谱用于跟踪硒生物还原产物的同素异形变化。有趣的是,在亚硒酸盐处理的微观世界中,膨润土的颜色从橙色变为黑色。在橙色层,鉴定出无定形或单斜晶系Se(0),而黑色沉淀物由稳定的三角Se(0)形式组成。IlluminaDNA测序表明具有Se(IV)还原和Se(0)同素异形生物转化潜力的菌株的分布,像假单胞菌,窄食单胞菌,Desulfosporosinus,和未分类的脱硫呋喃科。在存在Se(IV)的情况下,古细菌甲烷减少了其丰度,可能是由氧阴离子毒性引起的.这些发现提供了有关通过还原过程固定Se(IV)的膨润土微生物策略的理解,并证明了它们在DGR相关条件下从无定形到三角形Se(0)的同素异形生物转化中的意义。
Selenium, 79Se, is one of the most critical radionuclides in radioactive waste disposed in future deep geological repositories (DGRs). Here, we investigate the impact of bentonite microbial communities on the allotropic transformation of Se(IV) bioreduction products under
DGR relevant conditions. In addition, Se amendment-dependent shifts in the bentonite microbial populations are assessed. Microcosms of water-saturated bentonites were spiked with a bacterial consortium, treated with selenite and incubated anaerobically for six months. A combination of X-Ray Absorption Spectroscopy, Electron Microscopy, and Raman Spectroscopy was used to track the allotropic changes of the Se bioreduction products. Interestingly, the color of bentonite shifted from orange to black in the selenite-treated microcosms. In the orange layers, amorphous or monoclinic Se(0) were identified, whilst black precipitates consisted of stable trigonal Se(0) form. Illumina DNA sequencing indicated the distribution of strains with Se(IV) reducing and Se(0) allotropic biotransformation potential, like Pseudomonas, Stenotrophomonas, Desulfosporosinus, and unclassified-Desulfuromonadaceae. The archaea Methanosarcina decreased its abundance in the presence of Se(IV), probably caused by this oxyanion toxicity. These findings provide an understanding of the bentonite microbial strategies involved in the immobilization of Se(IV) by reduction processes, and prove their implication in the allotropic biotransformation from amorphous to trigonal Se(0) under
DGR relevant conditions.