Project Summary (2000-2006)

This project is a multi-disciplinary study of the hydrology, geophysics, and geochemistry of the region in Bangladesh where the biomedical projects in this program are being conducted. The overall groundwater flow regime is being determined from a broad survey of geophysical properties and hydrologic tracers such as 3H, 3He, and 14C. Arsenic is believed to mobilize and re-concentrate in different sediment layers through a series of oxidation and reduction reactions that do not proceed at the same rate for As and for Fe. Under certain conditions, such a sequence leads to extremely high As levels in groundwater. On the basis of this information, six new multi-level wells will be installed and 15 existing drinking water wells spanning a range of redox conditions will be monitored intensively. In addition to As concentration and speciation, the suite of parameters measured in the wells includes hydraulic head, temperature, conductivity, pH, Eh, dissolved O2, NO3, Mn, Fe, SO4, 18O and D (2H). The first objective is to collect detailed time series of groundwater As concentrations in the region where biomedical Project 3 and 4 will be conducted over a period of 4 years. The second objective is to use this information to test several hypotheses proposed to explain the extremely wide range of As concentrations in groundwater in Bangladesh. An improved understanding of the geochemical and hydrological factors that regulate As levels in groundwater will be directly transferable to the many parts of the U.S. where groundwater is enriched in As due to either natural processes or anthropogenic inputs.