Arsenic toxicity of groundwater in parts of the Bengal basin in India and Bangladesh: the role of Quaternary stratigraphy and Holocene sea-level fluctuation
Arsenic toxicity of groundwater in parts of the Bengal basin in India and Bangladesh: the role of Quaternary stratigraphy and Holocene sea-level fluctuation
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DOI：
10.1007/s002540000107
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发表时间：
2000-09-01
期刊：
影响因子：
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通讯作者：
Bhowmik, A
中科院分区：
文献类型：
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作者：
Acharyya, SK;Lahiri, S;Bhowmik, A
在恒河三角洲和孟加拉盆地的一些低洼地区，地下水中的砷毒性仅限于中全新世沉积物。更新世和全新世早期沉积物的解剖阶地和高地没有这样的问题。富砷黄铁矿或其他含砷矿物在受影响的沉积物中很少或不存在。砷似乎发生吸附在铁氢氧化物涂层的沙粒和粘土矿物，并以可溶性形式运输和共沉淀，或清除，铁（III）和锰（IV）在沉积物中。在中全新世海平面上升期间，孟加拉盆地的三角洲和一些低洼地区的细粒和富含有机物的沉积物中，它优先被捕获。随后在还原条件下释放，并通过微生物作用进一步介导。大量抽取地下水用于灌溉和施用磷肥可能引发了最近砷向地下水的释放。这种做法引起了地下水流动，调动了来自肥料和沉积物生物群腐烂的磷酸盐，并有助于砷的进一步释放。然而，环境还原程度不足以动员拉吉马哈尔上游恒河洪泛区地下水中的铁和砷。因此，孟加拉盆地地下水中的砷毒性是由其自然环境造成的，但似乎也是由最近的人类活动引发的。
Arsenic toxicity in groundwater in the Ganges delta and some low-lying areas in the Bengal basin is confined to middle Holocene sediments. Dissected terraces and highlands of Pleistocene and early Holocene deposits are free of such problems. Arsenic-rich pyrite or other arsenic minerals are rare or absent in the affected sediments. Arsenic appears to occur adsorbed on iron hydroxide-coated sand grains and clay minerals and is transported in soluble form and co-precipitated with, or is scavenged by, Fe(III) and Mn(IV) in the sediments. It became preferentially entrapped in fine-grained and organic-rich sediments during mid-Holocene sea-level rises in deltaic and some low-lying areas of the Bengal basin. It was liberated subsequently under reducing conditions and mediated further by microbial action. Intensive extraction of groundwater for irrigation and application of phosphate fertilizer possibly triggered the recent release of arsenic to groundwater. This practice has induced groundwater flow, mobilizing phosphate derived from fertilizer, as well as from decayed of sediment biota and aided the further release of arsenic. However, the environment is not sufficiently reducing to mobilize iron and arsenic in ground-water in the Ganges floodplains upstream of Raj-mahal. Thus, arsenic toxicity in the groundwater of the Bengal basin is caused by its natural setting, but also appears to be triggered by recent anthropogenic activities.