Water and Organic Carbon Cycles in Monsoon-driven Humid Tropics of the Western Ghats Mountain Belt, India

Insights from Stable Isotope Approach

M. Tripti, G. P. Gurumurthy, L. Lambs, J. Riotte, K. Balakrishna

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

The Western Ghats form a major mountain belt, next to the Himalayas, in controlling the flux of water and carbon to the northern Indian Ocean. This study attempts to understand the water and carbon cycles in two humid tropical river basins with its streams originating at higher altitudes of the Western Ghats, India. Water and suspended particulate matter (SPM) were collected on a monthly scale during summer monsoon season (June-September) from Swarna and Nethravati rivers draining into the Arabian Sea. For the source apportionment, samples have been measured for stable isotopes of oxygen (δ18O) and hydrogen (δ2H) in water and stable isotopes of carbon (δ13CPOC) in particulate organic matter (POM) at spatial scale from tributaries and main channel of rivers, and runoff water from agricultural land (dominant paddy field) and forest in the downstream region. The association between δ18O and deuterium-excess in river water and rain water shows that water in these tropical basins depicts rainout effect of marine source moisture during the onset of summer monsoon. As the monsoon intensifies, the fresher rain water replenishes older water stored previously in sub surface soil layer leading to its flushing into the river during summer monsoon season. Stable carbon isotope ratio and elemental ratio of POM (δ13CPOC = -27.1 ± 0.4 ‰ and C/N = 8.1 ± 1.7) in two humid tropical river water during summer monsoon season is an admixture of suspended particulates from runoff water of forest (δ13CPOC = - 27.82 ± 0.4 ‰) and agricultural land (δ13CPOC = -26.29 ± 0.4 ‰). It is found that δ13CPOC shows minimal variability with SPM content and C/N ratio within the same organic carbon pool. The study emphasizes the need to consider the agricultural runoff contribution to the rivers while establishing the global elemental budget and observing the global climate change.

Original languageEnglish
Pages (from-to)579-587
Number of pages9
JournalJournal of the Geological Society of India
Volume92
Issue number5
DOIs
Publication statusPublished - 01-11-2018

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humid tropics
carbon cycle
stable isotope
monsoon
organic carbon
mountain
water
suspended particulate matter
summer
particulate organic matter
river
river water
agricultural land
runoff
agricultural runoff
carbon isotope ratio
carbon
deuterium
paddy field
flushing

All Science Journal Classification (ASJC) codes

  • Geology

Cite this

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title = "Water and Organic Carbon Cycles in Monsoon-driven Humid Tropics of the Western Ghats Mountain Belt, India: Insights from Stable Isotope Approach",
abstract = "The Western Ghats form a major mountain belt, next to the Himalayas, in controlling the flux of water and carbon to the northern Indian Ocean. This study attempts to understand the water and carbon cycles in two humid tropical river basins with its streams originating at higher altitudes of the Western Ghats, India. Water and suspended particulate matter (SPM) were collected on a monthly scale during summer monsoon season (June-September) from Swarna and Nethravati rivers draining into the Arabian Sea. For the source apportionment, samples have been measured for stable isotopes of oxygen (δ18O) and hydrogen (δ2H) in water and stable isotopes of carbon (δ13CPOC) in particulate organic matter (POM) at spatial scale from tributaries and main channel of rivers, and runoff water from agricultural land (dominant paddy field) and forest in the downstream region. The association between δ18O and deuterium-excess in river water and rain water shows that water in these tropical basins depicts rainout effect of marine source moisture during the onset of summer monsoon. As the monsoon intensifies, the fresher rain water replenishes older water stored previously in sub surface soil layer leading to its flushing into the river during summer monsoon season. Stable carbon isotope ratio and elemental ratio of POM (δ13CPOC = -27.1 ± 0.4 ‰ and C/N = 8.1 ± 1.7) in two humid tropical river water during summer monsoon season is an admixture of suspended particulates from runoff water of forest (δ13CPOC = - 27.82 ± 0.4 ‰) and agricultural land (δ13CPOC = -26.29 ± 0.4 ‰). It is found that δ13CPOC shows minimal variability with SPM content and C/N ratio within the same organic carbon pool. The study emphasizes the need to consider the agricultural runoff contribution to the rivers while establishing the global elemental budget and observing the global climate change.",
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Water and Organic Carbon Cycles in Monsoon-driven Humid Tropics of the Western Ghats Mountain Belt, India : Insights from Stable Isotope Approach. / Tripti, M.; Gurumurthy, G. P.; Lambs, L.; Riotte, J.; Balakrishna, K.

In: Journal of the Geological Society of India, Vol. 92, No. 5, 01.11.2018, p. 579-587.

Research output: Contribution to journalArticle

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