Arsenic is having a devastating impact on human health in Asia. In Bangladesh and West Bengal alone, an estimated 57 million people are exposed to drinking water with arsenic concentrations exceeding the World Health Organization's recommended limit of 10 g/L. It is our hypothesis that different land uses will limit arsenic exposure to tens of millions more individuals within Southeast and Sub-continental Asia. We therefore propose an interdisciplinary study focusing on how land use alters the solid-water partitioning of arsenic in Cambodia and Vietnam. Our study blends an integrative scientific investigation of chemical, biological, and hydrologic factors controlling arsenic partitioning with an evaluation of the relationship between agricultural policies and farming practices on these processes. This research is a significant departure from existing efforts, in terms of scope and geography, with the goal of understanding the relative impact land use will have on biogeochemical mechanisms responsible for arsenic liberation.