Protracted storage of biospheric carbon in the Ganges–Brahmaputra basin


The amount of carbon stored in continental reservoirs such as soils, sediments and the biosphere greatly exceeds the amount of carbon in the atmosphere1. As such, small variations in the residence time of organic carbon in these reservoirs can produce large variations in the atmospheric inventory of carbon dioxide. One such reservoir is the Ganges–Brahmaputra system draining the Himalayas, which represents one of the largest sources of terrestrial biospheric carbon to the ocean2. Here, we examine the radiocarbon content of river sediments collected from the Ganges–Brahmaputra drainage basin to determine the residence time of organic carbon in this reservoir. We show that the average age of biospheric organic carbon in the drainage basin ranges from 0.5 to 17 thousand years. The radiocarbon age of plant-derived fatty acids—a proxy for labile terrestrial vegetation—ranges from just 0.05 to 1.3 thousand years. We propose that the bulk ages can be explained by the existence of a refractory, slowly cycling component of the organic carbon pool that is mixed with a younger labile pool. We estimate that this refractory component has an average age of over 15,000 years, and represents up to 20% of total biospheric carbon exported by the Ganges–Brahmaputra system. We suggest that global warming might destabilize this ancient pool of carbon, if warming stimulates microbial decomposition of organic carbon reserves.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Map of the Ganges–Brahmaputra river system showing the location of sampling sites.
Figure 2: Radiocarbon composition and average age of bulk biospheric C and long-chain n-alkanoic acids (C24+ FA).
Figure 3: Variation of the radiocarbon composition of long-chain n-alkanoic acids and bulk biospheric C with concentrations of long-chain n-alkanoic acid.


  1. 1

    Sabine, C. L. et al. The oceanic sink for anthropogenic CO2 . Science 305, 367–371 (2004).

    Article  Google Scholar 

  2. 2

    Galy, V. et al. Efficient organic carbon burial in the Bengal fan sustained by the Himalayan erosional system. Nature 450, 407–410 (2007).

    Article  Google Scholar 

  3. 3

    Berner, R. A. The long-term carbon cycle, fossil fuels and atmospheric composition. Nature 426, 323–326 (2003).

    Article  Google Scholar 

  4. 4

    Hayes, J. M. & Waldbauer, J. R. The carbon cycle and associated redox processes through time. Phil. Trans. R. Soc. B 361, 931–950 (2006).

    Article  Google Scholar 

  5. 5

    Galy, V., Beyssac, O., France-Lanord, C. & Eglinton, T. I. Recycling of graphite during Himalayan erosion: A geological stabilization of carbon in the crust. Science 322, 943–945 (2008).

    Article  Google Scholar 

  6. 6

    Garrels, R. M., Lerman, A. & Mackenzie, F. T. Controls of atmospheric O2 and CO2: Past, present and future. Am. Sci. 64, 306–315 (1976).

    Google Scholar 

  7. 7

    Sarmiento, J. & Gruber, N. in Ocean Biogeochemical Dynamics (eds Sarmiento, J. & Gruber, N.) Ch. 10, 392–453 (Princeton Univ. Press, 2006).

    Google Scholar 

  8. 8

    Trumbore, S. Comparison of carbon dynamics in tropical and temperate soils using radiocarbon measurements. Glob. Biogeochem. Cycles 7, 275–290 (1993).

    Article  Google Scholar 

  9. 9

    Blair, N. E., Leithold, E. L. & Aller, R. C. From bedrock to burial: The evolution of particulate organic carbon across coupled watershed-continental margin systems. Mar. Chem. 92, 141–156 (2004).

    Article  Google Scholar 

  10. 10

    Aufdenkampe, A. K. et al. Organic matter in the Peruvian headwaters of the Amazon: Compositional evolution from the Andes to the lowland Amazon mainstem. Org. Geochem. 38, 337–364 (2007).

    Article  Google Scholar 

  11. 11

    Galy, V., France-Lanord, C. & Lartiges, B. Loading and fate of particulate organic carbon from the Himalaya to the Ganga–Brahmaputra delta. Geochim. Cosmochim. Acta 72, 1767–1787 (2008).

    Article  Google Scholar 

  12. 12

    Hedges, J. I. et al. Compositions and fluxes of particulate organic material in the Amazon River. Limnol. Oceanogr. 31, 717–738 (1986).

    Article  Google Scholar 

  13. 13

    Bouchez, J. et al. Oxidation of petrogenic organic carbon in the Amazon floodplain as a source of atmospheric CO2 . Geology 38, 255–258 (2010).

    Article  Google Scholar 

  14. 14

    Drenzek, N. et al. A new look at old carbon in active margin sediments. Geology 37, 239–242 (2009).

    Article  Google Scholar 

  15. 15

    Drenzek, N. J., Montluçon, D. B., Yunker, M. B., Macdonald, R. W. & Eglinton, T. I. Constraints on the origin of sedimentary organic carbon in the Beaufort Sea from coupled molecular 13C and 14C measurements. Mar. Chem. 103, 146–162 (2007).

    Article  Google Scholar 

  16. 16

    Hilton, R. G., Galy, A., Hovius, N. & Horng, M. J. Efficient transport of fossil organic carbon to the ocean by steep mountain rivers: An orogenic carbon sequestration mechanism. Geology 39, 71–74 (2011).

    Article  Google Scholar 

  17. 17

    Mayorga, E. et al. Young organic matter as a source of carbon dioxide outgassing from Amazonian rivers. Nature 436, 538–541 (2005).

    Article  Google Scholar 

  18. 18

    Raymond, P. A. et al. Controls on the variability of organic matter and dissolved inorganic carbon ages in northeast US rivers. Mar. Chem. 92, 353–366 (2004).

    Article  Google Scholar 

  19. 19

    Galy, V., Eglinton, T., France-Lanord, C. & Sylva, S. The provenance of vegetation and environmental signatures encoded in vascular plant biomarkers carried by the Ganges–Brahmaputra rivers. Earth Planet. Sci. 304, 1–12 (2011).

    Article  Google Scholar 

  20. 20

    Burbank, D. et al. Decoupling of erosion and precipitation in the Himalayas. Nature 426, 652–655 (2003).

    Article  Google Scholar 

  21. 21

    Trumbore, S. Radiocarbon and soil carbon dynamics. Annu. Rev. Earth Planet. Sci. 37, 47–66 (2009).

    Article  Google Scholar 

  22. 22

    Eglinton, T. I. et al. Variability in radiocarbon ages of individual organic compounds from marine sediments. Science 277, 796–799 (1997).

    Article  Google Scholar 

  23. 23

    Galy, A. & France-Lanord, C. Weathering processes in the Ganges–Brahmaputra basin and the riverine alkalinity budget. Chem. Geol. 159, 31–60 (1999).

    Article  Google Scholar 

  24. 24

    IPCC, in Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (eds Solomon, S. et al.) (Cambridge Univ. Press, 2007).

    Google Scholar 

  25. 25

    Kirschbaum, M. The temperature dependence of soil organic matter decomposition, and the effect of global warming on soil organic C storage. Soil Biol. Biochem. 27, 753–760 (1995).

    Article  Google Scholar 

  26. 26

    Zimov, S. A., Schuur, E. A. G. & Chapin, F. S. Permafrost and the global carbon budget. Science 312, 1612–1613 (2006).

    Article  Google Scholar 

  27. 27

    RSP. Spatial representation and analysis of hydraulic and morphological data. Report No. FAP 24, (Water Resources Planning Organization (WARPO), 1996).

  28. 28

    Galy, V., Bouchez, J. & France-Lanord, C. Determination of total organic carbon content and δ13C in carbonate rich detrital sediments. Geostandards Geoanalytical Res. 31, 199–207 (2007).

    Google Scholar 

  29. 29

    Eglinton, T. I., Aluwihare, L. I., Bauer, J. E., Druffel, E. R. M. & McNichol, A. P. Gas chromatographic isolation of individual compounds from complex matrices for radiocarbon dating. Anal. Chem. 68, 904–912 (1996).

    Article  Google Scholar 

  30. 30

    Santos, G. M., Southon, J. R., Drenzek, N. J. & Ziolkowski, L. A. Blank assessment for ultra-small radiocarbon samples: Chemical extraction and separation versus AMS. Radiocarbon 52, 1322–1335 (2010).

    Article  Google Scholar 

Download references


We thank M. Rahman (Dhaka University) and A. Gajurel (Tribhuvan University) for their assistance during fieldwork in Bangladesh and Nepal. We thank D. Montluçon for technical support. We thank S. Jenouvrier for assistance with statistical analysis of the data. We thank C. France-Lanord for his support and insightful comments. This study was supported by the US National Science Foundation (Grants OCE-0851015 and OCE-0928582).

Author information




V.G. and T.E. designed the study and wrote the manuscript. V.G. performed bulk organic C and compound specific measurements. V.G. performed the sampling.

Corresponding author

Correspondence to Valier Galy.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Information (PDF 951 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Galy, V., Eglinton, T. Protracted storage of biospheric carbon in the Ganges–Brahmaputra basin. Nature Geosci 4, 843–847 (2011).

Download citation

Further reading


Sign up for the Nature Briefing newsletter for a daily update on COVID-19 science.
Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing