The importance of flood events and floodplain processes for the dynamics of organic carbon transport and processing in large tropical rivers systems.

This proposal wishes to improve our understanding of the role of episodic events and flood pulses on the transport and processing of carbon in tropical rivers, and on the role of floodplains in the basin-scale carbon budget. We propose to develop and employ a unique combination of advanced techniques to simultaneously assess sediment dynamics, C characteristics and C transformations in large tropical river basins. We will use a set of dissolved chemical elements, radionuclides (7Be, 137Cs, and 210Pb) and sediment mineralogy as proxies for suspended matter origin and residence time, combined with biogeochemical characterization of dissolved and particle-bound organic C (DOC and POC) fractions (e.g., delta13C signatures). Our proposed strategy consists of concurrent high-frequency sampling (i.e. daily to sub-daily scale) at two sites in the Tana River basin (Kenya) during an entire flood pulse, located upstream and downstream of floodplains, respectively. The net carbon balance effect of the deposition and remobilisation of sediments and associated organic matter in floodplains will be examined by a combination of carbon stock measurements, sedimentation rate measurements and post-deposition C loss estimates. A single modeling framework will be developed to link both riverine sediment and carbon transport and processing with floodplain carbon dynamics.

Keywords:Tropical rivers, Carbon dynamics, Geomorphology, Biogeochemistry, Sediment transport, Hydrology, Tana River

Disciplines:Geology, Aquatic sciences, challenges and pollution, Physical geography and environmental geoscience