Abstract
Since 1980s, elevated concentrations of As in groundwater across southern Asia have been a serious problem for over 100 million villagers relying on inexpensive shallow tubewells. The level of exposure has caused widespread illness including various cancers. Despite the magnitude of the health threat and a decade of research by numerous teams, many of the most basic factors and processes controlling arsenic within deltaic and floodplain aquifer systems remain unresolved. Particular scientific issues are, (i) ultimate source of As, (ii) physico-chemical factors controlling spatial/temporal variations of As, (iii) impact of anthropogenic activities, and so on. The aim of this review is to make clear the controversial issues in this field, and to suggest what issues are needed to clarify in near future. This review is classified into 4 chapters. Geochemical characteristics of As contaminated groundwater in Bengal Basin are firstly overviewed. In the second chapter, experimental studies related to the low temperature geochemistry of As are summarized, e.g., molecular structure analysis, speciation, and water-rock interaction. In the third chapter, previously proposed hypotheses for mechanism of groundwater As contamination are outlined. Considering the background studies, current controversial issues and future prospect are proposed in the final chapter.
