Arsenic fixing phase and transportation mechanism in Ganges-Brhmaputra-Meghna river system of Bangladish

Abstract

Major mineralogy, chemistry, grain size distribution and As host phases of river bed sediments from Ganges-Bramaptra-Meghna (BGM) river system were analyzed to estimate the transportation mechanism of As in the river running through the As affected groundwater areas.Arsenic was fixed in finer sediments, especially in <500 micron m fractions. Sequentially chemical extraction revealed that the main host phase was insoluble phase, mainly comprises silicates and sulfides, and it is notable that As in the other phases, such as adsorbed onto particles and fixed in Fe-oxyhydroxides/oxides, are negligible in the studied sediments. Although the host phase of As could not be specified by XRD and chemistry, basic mineral(s), biotite, chlorite or hornblende, would be the main host of As in the studied sediments. This study suggests that the As is mostly transported as detrital minerals without decomposition until finally settling in the downstream sediments in the BGM delta plain.