Coupling and environmental implications of in situ formed biogenic Fe-Mn minerals induced by indigenous bacteria and oxygen perturbations for As (III) immobilization in groundwater

作者：Zhao, Xinxin; Xie, Zuoming^*; Liu, Taikun; Li, Ping; Pei, Fuwen; Wang, Linan

来源：Science of the Total Environment, 2023, 858: 159884.

DOI：10.1016/j.scitotenv.2022.159884

• Oxygen perturbations
• Indigenous bacteria
• Fe-Mn minerals
• As immobilization
• As-rich groundwater

Iron (Fe)-manganese (Mn) minerals formed in situ can be used for the natural remediation of the primary poor -quality groundwater with coexistence of arsenite [As(III)], Mn(II), and Fe(II) (PGAMF). However, the underlying mechanisms of immobilization and coupling of As, Mn, and Fe during in-situ formation of Fe-Mn minerals in PGAMF remains unclear. The simultaneous immobilization and coupling of arsenic (As), Mn, and Fe in PGAMF during in-situ formation of biogenic Fe-Mn minerals induced by O-2 perturbations and indigenous bac-teria (Comamonas sp. RM6) were investigated at the different molar ratios of Fe(II):Mn(II) (1:1, 2:1, and 3:1). Compared with systems without Fe(II) in the presence of Mn(II), the coexisted Fe(II) significantly enhanced Mn(II) bio-oxidation and mineral precipitation, resulting in As immobilization increased by 5, 7, and 7 times at initial Fe(II) concentration of 0.3, 0.6, and 0.9 mM, respectively. Moreover, the As(III) immobilization effi-ciencies in Mn(II) and Fe(II) mixed system at initial Fe(II) concentration of 0.3, 0.6, and 0.9 mM were 73%, 91%, and 92%, respectively, that were significantly higher than those of single Fe(II) system (30%, 59%, and 74%) and those of single Mn(II) system (12% ), indicating that Fe(II) and Mn(II) oxidation synergically enhanced As(III) immobilization. This was mainly attributed to the formation and As adsorption capacity of bio-genic Fe-Mn minerals (BFMM). The formed BFMM significantly facilitated simultaneous immobilization of Fe, Mn, and As in PGAMF by oxidation, adsorption, and precipitation/coprecipitati on, a coupling of biological, physical, and chemical processes. Fe component was mainly responsible for As fixation, and Mn component dominated As(III) oxidation. Based on the results from this work, biostimulation and bioaugmentation techniques can be developed for in-situ purification and remediation of PGAMF. This work provides insights into the simultaneous immobilization of pollutants in PGAMF, as well as promising strategies for in-situ purification and remediation of PGAMF.