Mobilization of Arsenic in the Groundwater of Some Char Lands in Meghna Basin, Bangladesh: A Mechanistic Study

摘要

In this paper, we describe the mechanistic details for arsenic mobilization in some newly formed char lands in Meghna basin, Bangladesh. We measured the concentrations of arsenic along with some other associated parameters involved in the release mechanism of arsenic in sediment-water interface. Total 38 water samples were collected and analyzed from both shallow (60 to 110 feet) and deep (≥200 feet) aquifers and arsenic concentration ranged from 0 to 2.5 mg/L with an average value of 0.4266 mg/L. We observed three arsenic contaminated hot spots in the shallow aquifers where one spot's arsenic concentration is as high as 2.5 mg/L which could be the second highest arsenic contaminated spot in Bangladesh reported so far. Concentration of arsenic exhibits a clear positive correlation with iron and also with ammonium, bicarbonate and phosphate significantly. From the study, it reveals that reductive dissolution of arsenic-rich iron minerals is primarily responsible for the mobilization of arsenic in the groundwater. The presence of other competitive ions such as phosphate and bicarbonate in the adsorption-desorption process of arsenic were indentified for facilitating the mobilization.