Department of Hydraulic and Environmental Engineering, Pontificia Universidad Católica de Chile, Santiago, Chile.
Sci Total Environ. 2014 Jan 1;466-467:490-502. doi: 10.1016/j.scitotenv.2013.07.009. Epub 2013 Aug 7.
Rivers in northern Chile have arsenic (As) concentrations at levels that are toxic for humans and other organisms. Microorganism-mediated redox reactions have a crucial role in the As cycle; the microbial oxidation of As (As(III) to As(V)) is a critical transformation because it favors the immobilization of As in the solid phase. We studied the role of microbial As oxidation for controlling the mobility of As in the extreme environment found in the Chilean Altiplano (i.e., > 4000 meters above sea level (masl) and < 310 mm annual rainfall), which are conditions that have rarely been studied. Our model system was the upper Azufre River sub-basin, where the natural attenuation of As from hydrothermal discharge (pH 4-6) was observed. As(III) was actively oxidized by a microbial consortium, leading to a significant decrease in the dissolved As concentrations and a corresponding increase in the sediment's As concentration downstream of the hydrothermal source. In-situ oxidation experiments demonstrated that the As oxidation required biological activity, and microbiological molecular analysis confirmed the presence of As(III)-oxidizing groups (aroA-like genes) in the system. In addition, the pH measurements and solid phase analysis strongly suggested that the As removal mechanism involved adsorption or coprecipitation with Fe-oxyhydroxides. Taken together, these results indicate that the microorganism-mediated As oxidation contributed to the attenuation of As concentrations and the stabilization of As in the solid phase, therefore controlling the amount of As transported downstream. This study is the first to demonstrate the microbial oxidation of As in Altiplano basins and its relevance in the immobilization of As.
智利北部的河流中砷（As）浓度达到了对人类和其他生物有毒的水平。微生物介导的氧化还原反应在砷循环中起着至关重要的作用；微生物对砷的氧化（将 As(III)氧化为 As(V)）是一个关键的转化过程，因为它有利于将砷固定在固相中。我们研究了微生物砷氧化在控制智利高原极端环境中砷迁移性的作用（即，海拔超过 4000 米（masl）和年降雨量小于 310 毫米），这些条件很少被研究过。我们的模型系统是上硫磺河亚流域，在那里观察到了来自热液排放的砷的自然衰减（pH 值为 4-6）。微生物联合体积极氧化 As(III)，导致溶解态砷浓度显著降低，而在热液源下游的沉积物中砷浓度相应增加。原位氧化实验表明，砷氧化需要生物活性，微生物分子分析证实了系统中存在 As(III)氧化菌（aroA 样基因）。此外，pH 值测量和固相分析强烈表明，砷去除机制涉及与铁的氢氧化物的吸附或共沉淀。总之，这些结果表明，微生物介导的砷氧化有助于降低砷浓度和稳定砷在固相中的稳定性，从而控制下游输送的砷量。这项研究首次证明了高原盆地中微生物对砷的氧化作用及其对砷固定的重要性。
