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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
Modelling the chemical weathering fluxes at the watershed scale in the Tropics (Mule Hole, South India): Relative contribution of the smectite/kaolinite assemblage versus primary minerals
Chemical Geology, Volume 277, No. 1-2, Year 2010
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Description
We investigate the chemical weathering processes and fluxes in a small experimental watershed (SEW) through a modelling approach. The study site is the Mule Hole SEW developed on a gneissic basement located in the climatic gradient of the Western Ghats, South India. The model couples a lumped hydrological model simulating the water budget at the watershed scale to the WITCH model estimating the dissolution/precipitation rates of minerals using laboratory kinetic laws. Forcing functions and parameters of the simulation are defined by the field data. The coupled model is calibrated with stream and groundwater compositions through the testing of a large range of smectite solubility and abundance in the soil horizons. We found that, despite the low abundance of smectite in the dominant soil type of the watershed (4. vol.%), their net dissolution provides 75% of the export of dissolved silica, while primary silicate mineral dissolution releases only 15% of this flux. Overall, smectites (modelled as montmorillonites) are not stable under the present day climatic conditions. Furthermore, the dissolution of trace carbonates in the saprolitic horizon provides 50% of the calcium export at the watershed scale. Modelling results show the contrasted behavior of the two main soil types of the watershed: red soils (88% of the surface) are provider of calcium, while black soils (smectite-rich and characterized by a lower drainage) consumes calcium through overall carbonate precipitation. Our model results stress the key role played by minor/accessory minerals and by the thermodynamic properties of smectite minerals, and by the drainage of the weathering profiles on the weathering budget of a tropical watershed. © 2010 Elsevier B.V.
Authors & Co-Authors
Violette, Aurélie
France, Toulouse
Observatoire Midi-pyrénées
Goddéris, Yves
France, Toulouse
Observatoire Midi-pyrénées
Maréchal, Jean Christophe
India, Bengaluru
Indian Institute of Science
France, Orleans
Brgm
Riotte, Jean
France, Toulouse
Observatoire Midi-pyrénées
India, Bengaluru
Indian Institute of Science
Oliva, Priscia
France, Toulouse
Observatoire Midi-pyrénées
Mohan Kumar, Mandalagiri Subbarayappa
India, Bengaluru
Indian Institute of Science
Sekhar, Muddu Chandra
India, Bengaluru
Indian Institute of Science
Braun, Jean Jacques
France, Toulouse
Observatoire Midi-pyrénées
India, Bengaluru
Indian Institute of Science
Statistics
Citations: 57
Authors: 8
Affiliations: 3
Identifiers
Doi:
10.1016/j.chemgeo.2010.07.009
ISSN:
00092541
Research Areas
Environmental