The redox state of arsenic controls its toxicity and mobility in the subsurface environment. Understanding the redox reactions of arsenic is particularly important for addressing its environmental behavior. Clay miner...The redox state of arsenic controls its toxicity and mobility in the subsurface environment. Understanding the redox reactions of arsenic is particularly important for addressing its environmental behavior. Clay minerals are commonly found in soils and sediments, which are an important host for arsenic. However, limited information is known about the redox reactions between arsenic and structural Fe in clay minerals. In this study, the redox reactions between As(Ⅲ)/As(Ⅴ) and structural Fe in nontronite NAu-2 were investigated in anaerobic batch experiments. No oxidation of As(Ⅲ) was observed by the native Fe(Ⅲ)-NAu-2. Interestingly, anaerobic oxidation of As(Ⅲ) to As(Ⅴ) occurred after Fe(Ⅲ)-NAu-2 was bioreduced. Furthermore, anaerobic oxidization of As(Ⅲ) by bioreduced NAu-2 was significantly promoted by increasing Fe(Ⅲ)-NAu-2 reduction extent and initial As(Ⅲ) concentrations. Bioreduction of Fe(Ⅲ)-NAu-2 generated reactive Fe(Ⅲ)-O-Fe(Ⅱ) moieties at clay mineral edge sites. Anaerobic oxidation of As(Ⅲ) was attributed to the strong oxidation activity of the structural Fe(Ⅲ) within the Fe(Ⅲ)-O-Fe(Ⅱ) moieties. Our results provide a potential explanation for the presence of As(Ⅴ) in the anaerobic subsurface environment. Our findings also highlight that clay minerals can play an important role in controlling the redox state of arsenic in the natural environment.展开更多
基金supported by the National Natural Science Foundation of China(Nos.41977280,51678557,U1904205,and 51808541)the special fund from Key Laboratory of Drinking Water Science and Technology,Research Center for Eco-Environmental Sciences,Chinese Academy of Sciences(Nos.15Z09KLDWST and 18Z03KLDWST)。
文摘The redox state of arsenic controls its toxicity and mobility in the subsurface environment. Understanding the redox reactions of arsenic is particularly important for addressing its environmental behavior. Clay minerals are commonly found in soils and sediments, which are an important host for arsenic. However, limited information is known about the redox reactions between arsenic and structural Fe in clay minerals. In this study, the redox reactions between As(Ⅲ)/As(Ⅴ) and structural Fe in nontronite NAu-2 were investigated in anaerobic batch experiments. No oxidation of As(Ⅲ) was observed by the native Fe(Ⅲ)-NAu-2. Interestingly, anaerobic oxidation of As(Ⅲ) to As(Ⅴ) occurred after Fe(Ⅲ)-NAu-2 was bioreduced. Furthermore, anaerobic oxidization of As(Ⅲ) by bioreduced NAu-2 was significantly promoted by increasing Fe(Ⅲ)-NAu-2 reduction extent and initial As(Ⅲ) concentrations. Bioreduction of Fe(Ⅲ)-NAu-2 generated reactive Fe(Ⅲ)-O-Fe(Ⅱ) moieties at clay mineral edge sites. Anaerobic oxidation of As(Ⅲ) was attributed to the strong oxidation activity of the structural Fe(Ⅲ) within the Fe(Ⅲ)-O-Fe(Ⅱ) moieties. Our results provide a potential explanation for the presence of As(Ⅴ) in the anaerobic subsurface environment. Our findings also highlight that clay minerals can play an important role in controlling the redox state of arsenic in the natural environment.
