Thomas E. Bridge, Professor of Geology(emeritus), Emporia State University, Kansas & Meer T. Husain, Environmental Geologist, Kansas Department of Health And Environment, Kansas
The oxidation of arsenopyrite minerals present in the Bengal Delta sediments may be responsible for the release of arsenic oxides in solution to the ground water. The subsequent migration of this arsenic contaminated groundwater through these deltaic sediments may be one of the principal causes of arsenic poisoning in Bangladesh.
Arsenopyrite in the reducing environment below the groundwater table would be stable. If the groundwater table were lowered by increased irrigation during the dry season and the sediments exposed to the oxygen of the atmosphere then the arsenic rich pyrites would oxidize releasing arsenic.
Increased irrigation did became necessary during India's 23 years of unilateral diversion of Ganges water at Farakka Barrage in the West Bengal state of India (Fig.1: Annual discharge ). This cut the normal flow of the Ganges River during the dry season. If the oxidation of arsenopyrite or any other mineral is the cause of arsenic release to the groundwater due to a lowered water table then the solution to the arsenic problem is to restore the natural river flow of the Ganges River. 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 Barrage 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 river beds could then be dredged and groundwater produced at a safe yield rate.