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NATURAL ARSENIC IN GROUNDWATER: OCCURRENCE, REMEDIATION AND MANAGEMENT - CHAPTER 4

Nghiên cứu này cố gắng để điều tra thành phần khoáng vật của tiền gửi sông ngòi tạo thành tầng nước ngầm để hiểu hành vi của các giai đoạn vững chắc trong mối quan hệ để làm giàu asen trong nước ngầm ở Meghna đồng bằng ngập lũ của lưu vực sông Bengal. Các yếu tố chủ yếu trong các mẫu trầm tích cùng với hàm lượng asen tổng số, được xác định bởi XRF quang phổ. Leachable arsenic trong các mẫu trầm tích từ các khu vực của quá trình oxy hóa (3-4 m chiều sâu) trong điều. | Natural Arsenic in Groundwater Occurrence Remediation and Management -Bundschuh Bhattacharya and Chandrasekharam eds 2005 Taylor Francis Group London ISBN 04 1536 700 X Mineralogical characteristics of the Meghna floodplain sediments and arsenic enrichment in groundwater A.M. Sikder M.H. Khan Arsenic Research Group BD Banani Dhaka Bangladesh M.A. Hasan K.M. Ahmed Department of Geology University of Dhaka Dhaka Bangladesh ABSTRACT The study attempts to investigate the mineralogical composition of the fluvial deposits forming aquifers in order to understand the behavior of the solid phases in relation to arsenic enrichment in groundwater in the Meghna floodplain of the Bengal Basin. The major elements in the sediment samples along with its total arsenic content were determined by XRF spectrophotometer. Leachable arsenic in the sediments samples from the zone of oxidation 3-4 m depth under atmospheric condition at pH 5.5 is insignificant though the samples contain relatively high amount of total arsenic. Jarosite KFe3 SO4 2 OH 6 is identified in a number of samples and alunite KAl3 SO4 2 OH 6 is also observed in the lower part of the sequence. Carbonate minerals are found to exist throughout the entire sequence in the form of siderite FeCO3 dolomite CaMg CO3 2 and rhodocrosite MnCO3 . The present mineralogical and chemical analyses of sub-surface sediment samples of the studied area reveals that oxidation due to the fluctuation of the groundwater level do not contribute significant amount to the arsenic release to groundwater. The strong correlation between TOC content and total arsenic indicates that organic matters might have played an important role in the mobilization of arsenic to the groundwater of the Meghna floodplain of the Bengal Basin. 1 INTRODUCTION Arsenic enrichment in groundwater at shallow depths in the Ganges-Brahmaputra-Meghna GBM delta have been considered as an environmental catastrophe of the current time Dhar et al. 1997 Bhattacharya et al. 1997