Hydrological Aspects of Arsenic Contamination of Groundwater in Eastern India

Arsenic in the Bengal Delta has been the topic of discussion for more than a decade since 73% of the population (more than 140 million people) are under deep stress for locating arsenic-free drinking water. Most of this arsenic is geogenic, having its source from the Himalayan metamorphic facies, and is carried down by major river systems and thereby accumulating on the fluvio-deltaic plains to the southeast. All the states on this path are to some extent have depicted the presence of arsenic in the subsurface groundwaters. Currently, there are two major pathways for ingesting arsenic: (1) by the drinking water; and (2) by the food chain. Various scales of health effects from skin lesions to major cancer outbreaks have been located distinctively and pathologically in about 43% of the affected population. Irrigation practices have exacerbated the lateral extent of high arsenic in this region. Secondary natural minerals Fe and Mn oxy-hydroxides seem to adsorb both the valences of arsenic and, in the presence of labile organic carbon as in dissolved organic matter, help in releasing the arsenic into the groundwaters. Shallow to intermediate depth-reducing aquifers within the Holocene floodplains are the most contaminated and range from <10 to 4600 mu g L-1. The Bengal Basin, within a few meters of sea level, has repercussions from infiltrating saline seawater, and the impacts of climate change makes the problem worse in this region. Switching groundwater wells, harvesting rainwater, and household small-scale filtration systems, are the three most effective remediation mechanisms known to the people of the Bengal Delta.