0428同步年報-2021-全

070 ACTIVITY REPORT 2021 oxidation or indirect oxidation after Fe(II) dissolution followed by electron transfer between Fe(II) in the mineral substrate and Fe(III) in the solid or in solution. The LCF of Fe K-edge EXAFS and XANES spectra of the tailings ( Figs. 2(d) and 3(c) ) showed the decrease of biotite-like minerals (from 55 to 37%), epidote-like minerals (from ~20 to < 10%) and olivine-like minerals (from ~10% to nearly 0%) in tailings, in response to living SOB inoculation (TB5S and TB1S). In contrast, SOB colonization led to an increase of ferrihydrite-like minerals (from 25% to nearly 50%) in the tailings. Fe(III)-carboxyl complexes (Fe(III)-oxalate like) appeared after A. ferrooxidans inoculation in the S 0 -amended tailings. All these LCF-XAFS results were consistent with the qXRD results, revealing the critical role of A. ferrooxidans in the weathering of primary minerals ( i.e. , biotite, epidote and olivine) and formation of amorphous ferrihydrite-like minerals and Fe-organic complexes. In summary, Huang’s team used XAS measurements to reveal that Fe-bearing primary mineral weathering ( e.g. , biotite) and secondary mineral formation ( e.g. , ferrihydrite and jarosite) were induced by the activities of SOB, possibly through both a contact mechanism ( e.g. , direct oxidation of Fe 2+ to Fe 3+ ) and a non-contact mechanism ( e.g. , production of proton and organic compounds to stimulate elemental dissolution from minerals). It was determined that A. ferrooxidans coupled with the S 0 amendment was able to initiate and to accelerate the mineral weathering as the first step in the pedogenesis of alkaline Fe ore tailings. This knowledge of the behaviour and biogeochemical functionality of A. ferrooxidans in the tailings provides a fundamental basis to develop microbial bioweathering technologies using Fe/S-oxidizing bacteria towards eco- engineering soil formation in Fe ore tailings. (Reported by Ting-Shan Chan) This report features the work of Longbin Huang and his collaborators published in Environ. Sci. Technol. 55 , 8020 (2021). TLS 17C1 EXAFS • EXAFS, XANES • Environmental Science and Engineering, Biogeochemistry, Mineralogy Reference 1. Q. Yi, S. Wu, G. Southam, L. Robertson, F. You, Y. Liu, S. Wang, N. Saha, R. Webb, J. Wykes, T.-S. Chan, Y.-R. Lu, L. Huang, Environ. Sci. Technol. 55 , 8020 (2021). Fig. 3 : K-space Fe K-edge EXAFS spectra (black lines) and linear-combination fitting (LCF; red dashed lines) of Fe ore tailings from various treatments reveal the Fe phases in the tailings. The left column (a) also shows Fe K-edge EXAFS spectra of some key Fe standards including biotite, iron(II) oxide, ferrihydrite, Fe(III) oxalate, epidote and olivine. (b) Parameters and (c) results of the LCF fitting of Fe K-edge EXAFS spectra of Fe ore tailings from various treatments are also presented. [Reproduced from Ref. 1]