The groundwater arsenic poisoning in Bangladesh is the largest disaster in the history of human civilization: more than 100 million people have been drinking arsenic-poisoned water on a daily basis. A large number of scientists believe that the groundwater arsenic poisoning in Bangladesh is a natural disaster, that the poisoning has been present for thousands of years, and that reduction of ancient soil with ferric hydroxide -bearing arsenic is the main mechanism for the mobilization of arsenic into groundwater. However, historical groundwater use data from the dug wells and the tube wells, historical medical data, arsenic toxicological data, hydrological, hydro geological and geochemical parameters reject the reduction hypothesis an d suggest that the groundwater arsenic poisoning in Bangladesh is a recent, man -made disaster and that exposure and oxidation of arsenic minerals previously below the water table is probably the principal mechanism for releasing arsenic into groundwater. The oxidation of arsenic-bearing minerals present in the Bengal delta sediments is responsible for the release of arsenic oxides in solution to the groundwater. The subsequent migration of this arsenic-contaminated groundwater through the upper layers of deltaic sediments is the principal cause of arsenic poisoning in Bangladesh. Arsenic-bearing minerals of several kinds are associated with the organic -rich sediments present in deltaic environments. Available sources for arsenic are the ocean, coal beds in India, and mountains to the north. Minerals formed in these reducing environments below the groundwater table would be stable unless they were exposed to oxidizing -environments. The groundwater table is lowered by increased irrigation during the dry season and in the cone of depression formed by pumping -tube wells and irrigation wells drilled below the zone of fluctuation. The arsenic minerals in the newly exposed sediments oxidize and release the arsenic when the water table recovers and exposes the oxidized minerals to a reducing -environment. Increased irrigation did become necessary during India 's 30 years of unilateral diversion of river water from the Ganges, Tista and 28+ common rivers of Bangladesh and India which cut the normal flow of the 30+ rivers during the dry season. The solution to the arsenic problem is to restore the natural river flow of the Ganges, Tista and other common rivers of Bangladesh and India. This would restore the groundwater level to a level that existed in Bangladesh prior to the construction and commission of Farakka Barrage in 1975 . Other man-made environmental disasters created by the Farakka, Tista and other barrages/dams constructed in the common rivers of Bangladesh and India would also be solved if these barrages were removed and a normal flow restored. The riverb eds could then be dredged and groundwater produced at a safe yield rate. A comprehensive plan not only for water supplies but associated waste disposal should be worked out for all of Bangladesh. Individual units within the plan could t hen be developed on the bases of need and tied into the overall plan as it develops.
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