Arsenic in groundwater in the Bengal Delta Plain: slow poisoning in Bangladesh

摘要

The purpose of this paper is to provide an overview of the problems concerning the widespread occurrences of arsenic in groundwater in Bangladesh, a land with enormous resources of precipitation, surface water, and groundwater. Because of the potential risk of microbiological contamination in the surface water, groundwater was relied on as an alternate source of drinking water. Exploitation of groundwater has increased dramatically in Bangladesh since the 1960s to provide safe water for drinking and to sustain wetland agriculture. The presence of arsenic in the groundwater at elevated concentrations has raised a serious threat to public health in the region. Nearly 60-75 million people inhabiting a large geographical area are at potential risk ofarsenic exposure, and several thousands have already been affected by chronic arsenicosis. The source of arsenic in groundwater is geogenic and restricted within the Holocene sedimentary aquifers. Mobilization of arsenic from the alluvial aquifers is primarily effected through a mechanism of reductive dissolution of the iron oxyhydroxides within the sediments, rather than by the oxidation of pyrite, as has been hypothesized by other workers. The problem is further accentuated by the fact that arsenic isalso found at elevated concentrations in vegetables and rice grown in the areas where high-arsenic groundwater is used for irrigation. Dietary habits among the population are also an important pathway for arsenic ingestion. Studies are in progress at national as well as international levels to alleviate the arsenic crisis in Bangladesh. Besides the identification of arsenic-free tubewells in the affected areas for drinking purposes, purification of groundwater at household level by low-cost arsenic removal techniques is suggested. Rehabilitation of the patients with chronic arsenicosis and arsenic education programs for rural communities must be addressed urgently by the government of Bangladesh.