Collaborative Research: Hydrologic, Geomorphic, and Geochemical Controls on Iron, Arsenic, and Organic Matter Cycling Across River-to-Tidal Corridors

Despite decades of research and mitigation efforts, millions of people in tropical regions still drink groundwater contaminated with arsenic. One reason is that arsenic is unevenly distributed, and the processes that control its movement remain poorly understood. This project studies river floodplains in Bangladesh to understand how arsenic moves among rivers, floodplain sediments, and aquifers. The goal is to identify the hydrologic and geochemical conditions that release arsenic and determine how human activities affect these processes. The results will improve understanding of contaminant transport in connected river and groundwater systems, providing knowledge that can support groundwater management in the United States and elsewhere. The interactions among water, rock, and organic matter that control arsenic release are difficult to study because groundwater flowpaths are hard to define, physical and chemical processes influence one another, and groundwater chemistry reflects reactions that occur over long distances. This project combines groundwater levels, water chemistry, isotopes, in situ microcosms, and reactive transport models to identify the conditions that make arsenic mobile. The resulting framework will improve predictions of contaminant movement in floodplain aquifers and help scientists understand groundwater quality in river corridors where similar processes affect arsenic, nutrients, iron, manganese, and other contaminants. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.