Biogeochemical controls of arsenic mobilization in rural Bangladesh: the role of methane and ammonium
Goals
- Mechanistic understanding of the processes in the groundwater of rural regions in Bangladesh that lead to the release of arsenic
- Biogeochemical control processes, with a particular focus on the role of CH4, and NH4 as electron donors in the microbial reduction of iron(III)
- Investigation of the microbial oxidation of CH4, and NH4, coupled with the reductive dissolution of arsenic-containing iron(III) oxyhydroxides as a potential key driver of arsenic release
- Seasonal effects on groundwater recharge, the seasonal availability of organic matter, local hydrostratigraphic conditions, and land use
- Investigation of CH4, and NH4 formation, vertical migration, and subsequent oxidation or conversion in spatially and temporally distinct redox zones
Specifically
- Depth-specific and seasonally repeated sampling of groundwater, gases, and sediments at two representative sites in Bangladesh
- Stable isotope analytical methods as well as comprehensive geochemical, hydrological, and microbial analyses to identify key transformation pathways of CH₄ and NH₄
- Integration of microbiological, hydrogeological, and geochemical data to elucidate relevant microbial metabolic processes
- Process-oriented conceptual model of arsenic mobilization through the integration of data from sediment, water, and gas phases across temporal and spatial gradients
- Risk assessments and the development of effective, site-specific remediation strategies
Project Lead
Heidelberg University — Biogeochemistry Group
Prof. Frank Keppler
Dr. Martin Maier
Cooperation Partners
- Heidelberg University — Geomorphology (Prof. Olaf Bubenzer)
- Dhaka University — Geology (Prof. Kazi Matin Ahmed)
- Manchester University — Environmental Geochemistry (Prof. David Polya, Dr. Laura Richards, Prof. Bart van Dongen and Prof. Jonathan Lloyd)
- Basel University — Environmental Sciences (Prof. Moritz Lehmann)
- Thünen Institute — Climate Smart Agriculture (Dr. Reinhard Well)
Funding
German Research Foundation (DFG), KE 884/30-1
Activities & Progress
- Compilation of initial field data from various study sites in Bangladesh
- Selection of suitable sites in the northeast (Sirajganj) and northeast (Sylhet) in the spring of 2026
- Installation of monitoring wells for depth-zoned sampling of the shallow aquifer
- Liner drilling for soil characterization and collection of undisturbed sediment samples
- Sediment analyses focusing on active organic fractions
- Microcosm studies
- Gamma-log surveys in the vicinity of the boreholes
- Depth-zoned samples of groundwater and dissolved gases across four seasons and various land uses
- Measurement of stable isotopes of H, CO2, CH4, as well as NO3 and NH4
