Geoscience research conducted as part of this project focuses on the vulnerability of aquifers that are currently low in arsenic (As), but may become affected by human perturbations such as irrigation pumping and municipal pumping. These low-As aquifers are crucial for reducing As exposure for the Health of Effects of Arsenic Longitudinal Study (HEALS) cohort in Bangladesh, and throughout South and Southeast Asia. The approach builds on the premise that: a) iron oxide dissolution and precipitation control the partitioning of As between groundwater and aquifer sediments; and b) the supply of reactive organic carbon controls iron oxide dissolution and therefore the release of As to groundwater. The researchers are testing three hypotheses in collaboration with other projects and cores of the Columbia University Superfund Research Program Center: • Whether irrigation pumping has redistributed As in shallow aquifers by enhanced lateral mixing • Whether clay layers releasing organic carbon to deep, depressurized sandy aquifers pose a greater threat of As contamination than downward advection due to the lack of such clays • Whether exposure to As can be predicted at the individual level from information available from the household including the status of its own and surrounding well(s), access to these wells, and awareness to the health risks of continued exposure. ExpandCollapse Abstract