Role of Colloidal Particles as Scavengers of Groundwater Arsenic: A Case Study from Rural Bengal

Elevated arsenic (As) in groundwater is a well-known phenomenon in the Bengal delta plain (BDP). It has been found that mobilization of As can be influenced by the presence of dissolved organic carbon (DOC) and other mineral phases (specially Fe). In this study, groundwater samples were filtered through varying pore size membrane filters to investigate the fractional distribution of As associated with colloids. Arsenic was found to be associated with colloidal particles having organic matter and Fe mineral phases. This finding is very important for explaining the release mechanism of groundwater As, because such data did not exist with respect to BDP, related to the dissolved phase/colloidal retention of As. This study shows that it would be better to consider the dissolved and colloidal phases as potential scavengers of As when assessing its mobilization or mitigation.