Oxidation of organic carbon and weathering of silicate minerals during fluvial transit from mountains to depositional basins control the exchange of carbon dioxide between the atmosphere, biosphere, and geosphere and can alter global climate over geologic timescales. In several projects we investigate the processes and determine fluxes that drive the global carbon cycle.
This project, funded by the German Science Foundations (DFG) funded International Research Training Group StRATEGy aims to understand how rivers transfer terrestrial organic material and what happens to it during transit. Rivers drain continents and thereby convey terrestrial sediments through landscapes and eventually to the ocean. Organic material takes different paths during its journey through the landscape, therefore, we investigate various processes that impact transport, bonding and sequestration of organic material constrained by fluvial transit and intermediate floodplain storage. We use organic-geochemical methods to fingerprint the organic carbon in the river system and further, mineralogical, isotopegeochemical and experimental methods to determine the fate of the organic matter. Our results contribute to our understanding of the natural processes affecting organic carbon during fluvial transport.
We investigate the effect of weathering and erosion of fossil organic carbon, which is eroded today in eastern Nepal at the upstream Kali Gandaki river. This carbon was removed from the atmosphere through photosynthesis millions of years ago and is exported today by this river. We are developing novel methods to characterize this organic carbon on a molecular level (compound-specific carbon and hydrogen isotope analysis, ultra-high resolution mass spectrometry FT-ICR-MS) and better understand transport and transformation.
With the analysis of stable water isotope ration we are investigating hydrological fluxes in NW India. In particular we detect the relative effect of precipitation and snow/glacial melt on surface runoff. We investigate, if the biomarker and stable isotopic composition of soils is characteristic for altitude and climatic conditions in the Sutlej valley in NW India and evaluate it’s potential as a proxy for past climates and tectonic uplift. This project is part of the EU funded Innovative Training Network iTECC.
Despite it’s critical role in the global carbon cycle, data documenting organic carbon oxidation and silicate weathering rates within rivers and their floodplains are rare, and the mechanisms controlling total silicate weathering and oxidative losses from sediment source to sink are poorly understood. We are currently performing a combination of laboratory flume experiments and targeted field measurements designed to disentangle weathering occurring in active river transport versus during temporary deposition in floodplains. Because organic carbon loading of sediments tends to increase with decreasing grain size, we are measuring the grain size distribution of our samples in the Sediment Laboratory to correct for any grain-size dependencies that exist. The results will elucidate the major mechanistic controls on silicate weathering and organic carbon oxidation in fluvial transit from source to sink, and allow for building process-based models linking sediment transport, organic carbon oxidation, and silicate weathering capable of predicting the influence of changing tectonic and climatic regimes on the global carbon cycle.