Chemical weathering and associated carbon-dioxide consumption in a tropical river basin (Swarna River), Southwestern India

Tripti, M and Gurumurthy, G P and Balakrishna, K and Stéphane, Audry and Jean, Riotte and J-J, Braun and Chadaga, Mohandas and Udayashankar, H N and L, Lambs (2013) Chemical weathering and associated carbon-dioxide consumption in a tropical river basin (Swarna River), Southwestern India. In: American Geophysical Union Fall Meeting 2013, 9-13, San Francisco, USA.

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Abstract

Chemical weathering in river basins forms the key process to study the global climate change on a long term scale due to its association with the carbon sequestration. Water samples from a west flowing tropical river (Swarna River) of Southern India were collected for a period of two years to study the chemical weathering process and to quantify the weathering and associated carbon-dioxide consumption rates in the river basin. In addition, the major ion chemistry of Swarna River is studied for the first time on a spatial and temporal (monthly) scale to decipher the factors (lithology, precipitation/ discharge, temperature, slope and physical weathering) controlling the chemical weathering process. Swarna River originates in Western Ghats at an altitude of 1100 m above mean sea level and flows westwards draining Peninsular Gneiss and Dharwar Schist to join the Arabian Sea near Udupi. The river basin receives annual rainfall of 4500 mm and experiences warm climate with average temperature of 30°C. Major ion composition and radiogenic strontium isotopic composition measured in the Swarna river water reflects the influence of silicate rocks in the basin. The river water chemistry is found to be least affected by anthropogenic impact; however, the effect of evaporation is observed on few samples during the peak dry season. The atmospheric inputs and carbonate contributions to the river water are corrected to estimate the silicate weathering rate (SWR) and the associated carbon-dioxide consumption rate (CCR) using local rainwater and bed rock composition respectively. The SWR and CCR in the Swarna river basin are estimated to be 46 tons/km2/yr and 4.4 x 10^5 mol/km2/yr respectively. This estimation is observed to be relatively higher than the recently reported SWR and CCR in the adjacent larger Nethravati river basin (Gurumurthy et al., 2012). The increased rate could be attributed to the relatively higher precipitation in the Swarna river basin than the lithological variation between the two basins. The weathering process is largely controlled by the higher run-off accompanied by warm temperature in the Swarna river basin. The intense silicate weathering is also supported by the highly radiogenic strontium isotope composition (87Sr/86Sr) ranging between 0.7195 and 0.7304 in the Swarna river water. The average 87Sr/86Sr = 0.7249 in the river water is found to be higher than the global river average. Keywords: Major ion, Radiogenic strontium isotope, Silicate weathering rate, Carbon-dioxide consumption rate, Tropical river, Southwestern India.

Item Type: Conference or Workshop Item (Poster)
Uncontrolled Keywords: Chemical weathering;carbon-dioxide;tropical river basin; Swarna River;Southwestern; India
Subjects: Engineering > MIT Manipal > Civil Engineering
Departments at MU > Manipal Centre for Natural Sciences
Depositing User: MCNS Editor
Date Deposited: 10 Feb 2014 11:16
Last Modified: 20 Apr 2015 06:05
URI: http://eprints.manipal.edu/id/eprint/137313

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