水土砷污染是重要的环境问题。无定形次生含砷矿物是酸性矿山废水（AMD）中砷的重要赋存形态，由于其具有高比表面积、高活性等特征，对砷的固液交换、形态转化有重要影响。然而目前对AMD中无定形次生含砷矿物的赋存分子形态、稳定性及形态转化过程与产物的认识还十分缺乏。本研究拟通过实地调研和文献查阅获得AMD中的主要元素组成和水质参数，从简单体系到复杂体系在不同pH条件下沉淀无定形次生含砷矿物，通过研究产物的溶解度、元素组成、表面形貌、比表面积等获得热力学参数和物理化学性质；利用同步辐射X射线吸收谱、密度泛函、全势多重散射等技术表征其赋存分子形态；通过考察不同pH、共存离子存在条件下和矿物转化过程中砷及相关元素的固液分配、络合形态、固相赋存形态等揭示影响其稳定性的主控因子和控制机理。研究成果对于深入理解AMD中砷的地球化学循环演化规律及建立经济有效的砷污染控制技术具有重要意义。

Arsenic pollution of soils and waters is an important environmental concern. Poorly crystalline secondary As-bearing minerals (PCSAM) are important occurrence of arsenic and strongly influence its mobility in acid mine drainage (AMD) due to their poor crystallinity, high surface area and reactivity. However, the molecular structure, stability, and transformation process and products of poorly crystalline As-bearing secondary minerals are still no well known at present in AMD. In this study, based on the major elemental constitutions and environmental parameters obtained from field survey and documents, we will investigate the formation of PCSAMs at different pH. At the same time, we will investigate their solubility, elemental compositions, morphologies, and surface areas to obtain their thermodynamic constants and physio-chemical parameters. We will probe their molecular structures by jointly using synchrotron-based X-ray absorption spectroscopy, density functional theory calculations, and full multiple scattering calculations. In addition, we will discover the dominant factors and mechanisms controlling the stability of PCSAMs in the presence of various co-existing ions and their transformation processes and products based on the solid-liquid distribution, aqueous species, and solid occurrences of As and related elements. The findings will be of significance for understanding the geochemical cycle of arsenic in AMD and for developing the economic and effective pollution controlling method.