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

该项目提议为研究砷含氧阴离子中氧的同位素组成提供基础，砷含氧阴离子是一种迄今为止尚未研究的同位素系统，但它显示出很大的潜力，可以对导致世界许多地区高砷地下水发展的情况和过程有新的认识。所需的方法学发展包括制定适当的样品制备程序，用于提取和分离砷含氧阴离子（包括与干扰阴离子的分离），以及提供适当的技术，用于测量这些物质中氧的同位素比。必须研究诸如同位素与水交换的动力学等基本问题。结合磷酸盐中氧的同位素组成的方法将被应用在三个具有不同的氧化还原功能的地点（在西孟加拉，越南和内蒙古），旨在找出这些网站的地下水中的砷是否直接来自周围的含水层沉积物（autochtonous），或者如果它是从一个遥远的低氧化还原环境中运输到高砷网站（allochtonous）。这些问题的验证对于查明高砷区产生的根本原因和防治高砷区灾害具有重要意义。

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.