The isotopic composition of oxygen in arsenate and arsenite: a novel approach to constrain the source of arsenic in groundwater

该项目建议为砷氧离子中氧的同位素组成的研究提供基础，这是一个迄今尚未研究的同位素系统，但它显示出强大的潜力，可以对导致世界许多地区高砷地下水发展的环境和过程有新的认识。所需的有条不紊的发展包括为砷氧离子的提取和分离（包括与干扰阴离子的分离）制定适当的样品制备程序，以及提供适当的技术来测量这些物种中氧的同位素比率。必须研究同位素与水交换动力学等基本问题。结合磷酸盐中氧的同位素组成，该方法将应用于三个具有明显氧化还原特征的地点（西孟加拉邦、越南和内蒙古），旨在找出这些地点地下水中的砷是直接来自周围含水层沉积物（本地）还是从遥远的低氧化还原环境运输到高砷地点（异地）。对这些问题的核实对于找出导致高砷地区发生的最终原因和防治这类灾害至关重要。

The project proposes to provide a basis for the study of the isotopic composition of oxygen in arsenic oxyanions, an isotope system which has not been investigated until now, but which shows a strong potential in getting new insights into the circumstances and processes that led to the development of high arsenic groundwaters in many parts of the world. The required methodical developments consist in elaboration of an adequate sample preparation procedure for the extraction and separation of the arsenic oxyanions (including separation from interfering anions), as well as in the supply of an adequate technique for the measurement of the isotope ratios of oxygen in these species. Basic issues like the kinetic of isotope exchange with water must be investigated. In combination with the isotope composition of oxygen in phosphate the approach will be applied in three locations with distinct redox features (in West Bengal, Vietnam, and Inner Mongolia), intending to find out whether the arsenic in groundwater in these sites originates directly from the surrounding aquifer sediments (autochtonous) or if it was transported from a distant low redox environment to the high arsenic site (allochtonous). The verification of such questions is crucial in finding out the ultimate causes which lead to the occurrence of high arsenic regions and to combat such calamities.