Comparative study on the hydrogeochemical environment at the major drinking water based arsenism areas

In major drinking water based arsenism areas of China, the hydrogeochemical environment is controlled by the geology, structure and depositional environments. The arsenism prevalence and degree are closely linked to local hydro-chemical environments and the form and valence of arsenic in the groundwater. In this paper, field trips, samples monitoring and comprehensive comparison methods, and hydrogeochemical environment are comparatively analyzed at five drinking water based arsenism areas of China comprising Taiwan, Xinjiang Uygur Autonomous Region, Inner Mongolia Autonomous Region, Shanxi and Jilin provinces. The arsenism areas, except Taiwan, are located in arid and semi-arid areas indicating that the climate condition is not the main factor that affects the groundwater arsenic enrichment. All arsenism areas are located in the center of sedimentary basins or relatively lower zones within the plains, and the groundwater for drinking is taken from the Cenozoic layer. The groundwater in Taiwan, Inner Mongolia and Shanxi arsenism areas are located in a complex organic-rich reductive environment, where not only high As (III) contents occur but also detectable levels of organic matter, humic acid and methyl arsine. In the groundwater samples of the Inner Mongolia arsenism area, many gases are detected, such as H2S, CH4, and NH3. Groundwater environments in Xinjiang Uygur Autonomous Region and Jilin province show oxidic conditions with As (V), and organic arsine is rarely or never detected.