Boyanov, Maxim I. Fletcher, Kelly E. Kwon, Man Jae Rui, Xue O'Loughlin, Edward J. Loeffler, Frank E. Kemner, Kenneth M. 2024-01-20T16:04:00Z 2024-01-20T16:04:00Z 2021-09-01 2011-10-01 0013-936X https://pubs.kist.re.kr/handle/201004/129909 Reduction of U(VI) to U(IV) as the result of direct or indirect microbial activity is currently being explored for in situ remediation of subsurface U plumes, under the assumption that U(IV) solubility is controlled by the low-solubility mineral uraninite (U(IV)-dioxide). However, recent characterizations of U in sediments from biostimulated field sites, as well as laboratory U(VI) bioreduction studies, report on the formation of U(IV) species that lack the U=O(2)=U coordination of uraninite, suggesting that phases other than uraninite may be controlling U(IV) solubility in environments with complexing surfaces and ligands. To determine the controls on the formation of such nonuraninite U(IV) species, the current work studied the reduction of carbonate-complexed U(VI) by (1) five Gram-positive Desulfitobacterium strains, (2) the Gram-negative bacteria Anaeromyxobacter dehalogenans 2CP-C and Shewanella putrefaciens CN32, and (3) chemically reduced 9,10-anthrahydroquinone-2,6-disulfonate (AH(2)QDS, a soluble reductant). Further, the effects of 0.3 mM dissolved phosphate on U(IV) species formation were explored. Extended X-ray absorption fine structure (EXAFS) spectroscopy analysis demonstrated that the addition of phosphate causes the formation of a nonuraninite, phosphate-complexed U(IV) species, independent of the biological or abiotic mode of U(VI) reduction. In phosphate-free medium, U(VI) reduction by Desulfitobacterium spp. and by AH(2)QDS resulted in nonuraninite, carbonate-complexed U(IV) species, whereas reduction by Anaeromyxobacter or Shewanella yielded nanoparticulate uraninite. These findings suggest that the Gram-positive Desulfitobacterium strains and the Gram-negative Anaeromyxobacter and Shewanella species use distinct mechanisms to reduce U(VI). English American Chemical Society U(VI) REDUCTION URANINITE NANOPARTICLES CONTAMINATED SUBSURFACE URANIUM(VI) PHOSPHATE ELECTRON-TRANSFER BIOREDUCTION ADSORPTION SEDIMENTS UO2 BIOMINERALIZATION Solution and Microbial Controls on the Formation of Reduced U(IV) Species Article 10.1021/es2014049 1 Environmental Science & Technology, v.45, no.19, pp.8336 - 8344 Environmental Science & Technology 45 19 8336 8344 scie scopus 000295245600054 2-s2.0-80053415935 Engineering, Environmental Environmental Sciences Engineering Environmental Sciences & Ecology Article U(VI) REDUCTION URANINITE NANOPARTICLES CONTAMINATED SUBSURFACE URANIUM(VI) PHOSPHATE ELECTRON-TRANSFER BIOREDUCTION ADSORPTION SEDIMENTS UO2 BIOMINERALIZATION