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Séminaire de Gurumurthy, Birbal Sahni Inst. of Paleosciences, India

Silicate weathering in humid tropics and coastal biogeochemical processes affecting the elemental budgets to Oceans

The Western Ghats form a major mountain belt, next to the Himalayas, in controlling the flux of chemical elements and sediments to the northern Indian Ocean. Numerous small mountain streams flow towards the Arabian Sea draining the western slopes of Western Ghats because of the prevailing orographicity. The weathering process and the associated atmospheric CO2 drawdown due to silicate weathering have been deduced using the dissolved and particulate chemical composition in river basins having similar geomorpho-climatic settings but differing lithology (granite-gneisses, charnockites and basalts). The speaker discusses the silicates weathering process in the small mountain streams of Western Ghats, the rate controlling parameters and their role in geological carbon sequestration.

Further, the geochemical redistribution of redox sensitive elements during the weathering and fluvial transport process with special reference to molybdenum geochemistry in the riverine and estuarine environments will be discussed. The role of oxidative scavenging of dissolved molybdenum on to particulate phase in river, and its subsequent release/scavenging of metal elements in the coastal region will be discussed in detail to demonstrate the role of coastal/interface biogeochemical processes in the source-sink pathways of chemical elements, and the extent these biogeochemical processes affect the elemental budgets.