Presented at the Joint European Stable Isotope Users Group Meeting (JESIUM) 2012 held in Leipzig, Germany, on September 2–7, 2012.
First assessment of water and carbon cycles in two tropical coastal rivers of south-west India: an isotopic approach†
Article first published online: 2 JUL 2013
Copyright © 2013 John Wiley & Sons, Ltd.
Rapid Communications in Mass Spectrometry
Volume 27, Issue 15, pages 1681–1689, 15 August 2013
How to Cite
Tripti, M., Lambs, L., Otto, T., Gurumurthy, G. P., Teisserenc, R., Moussa, I., Balakrishna, K. and Probst, J. L. (2013), First assessment of water and carbon cycles in two tropical coastal rivers of south-west India: an isotopic approach. Rapid Commun. Mass Spectrom., 27: 1681–1689. doi: 10.1002/rcm.6616
- Issue published online: 20 JUN 2013
- Article first published online: 2 JUL 2013
- Manuscript Revised: 29 APR 2013
- Manuscript Accepted: 29 APR 2013
- Manuscript Received: 31 JAN 2013
The contribution of tropical coastal rivers to the global carbon budget remains unmeasured, despite their high water dynamics, i.e. higher run-off with their basin characteristic of warm temperature. Two rivers draining the western part of the Western Ghats, the Swarna (length 80 km) and Nethravati (147 km) Rivers, were studied for water and carbon cycles.
The stable isotope ratios of oxygen (δ18O values), hydrogen (δ2H values) and carbon (δ13C values) were used to understand the water circulation, the weathering processes and the carbon biogeochemical cycle. The river water samples were collected during the dry post-monsoonal season (November 2011).
The δ18O and δ2H values of river water suggested that the monsoonal vapour source and its high recycling have a dominant role because of the orographical and tropical conditions. The absence of calcareous rocks has led to dissolved inorganic carbon (DIC) mainly originating from atmospheric/soil CO2, via rock-weathering processes, and the low soil organic matter combined with high run-off intensity has led to low riverine dissolved organic carbon (DOC) contents. The δ13C values increase from upstream to downstream and decrease with increasing pCO2. There is a positive relationship between the δ13CDIC values and the DOC concentrations in these two rivers that is contrary to that in most of the studied rivers of the world.
The higher evapotranspiration supported by tropical conditions suggests that there are higher vapour recycling process in the Swarna and Nethravati basins as studied from the water δ18O and δ2H values. The basin characteristics of higher rainfall/run-off accompanied by warm temperature suggest that the δ13C value of riverine DIC is mainly controlled by the weathering of source rocks (silicates) with variation along the river course by CO2 degassing from the river water to the atmosphere and is less dominated by the oxidation of DOC. Copyright © 2013 John Wiley & Sons, Ltd.