Role of Organic Carbon of Oxbow Lakes in Making Aquifers Vul- Nerable to Arsenic Mobilization

Dissolved organic matter (DOM) is implicated in arsenic (As) and iron (Fe) mobilization via microbial metabolic processes. The Ganges Delta Plain is a key area where As contamination of groundwater constitutes a human catastrophe. The delta plain geomorphology comprises a large number of abandoned meander bends, or oxbow lakes (Donselaar et al., 2017) characterized by an anoxic environment in the lower part of the lake water column (hypolimnion). Organic matter (OM) is preserved in this environment and provides a perfect environment for microbial oxidation and mobilization of As-bearing Fe-oxides. Additional deposition of human introduced sewage wastes into the lake waters adds to a rich source of nutrients to the indigenous microbial communities.