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New views on old carbon in the Amazon river: Insight from the source of organic carbon eroded from the Peruvian Andes

Clark, K.E.; Hilton, R.G.; West, A.J.; Malhi, Y.; Gröcke, D.R.; Bryant, C.L.; Ascough, P.L.; Robles Caceres, A.; New, M.

New views on old carbon in the Amazon river: Insight from the source of organic carbon eroded from the Peruvian Andes Thumbnail


Authors

K.E. Clark

R.G. Hilton

A.J. West

Y. Malhi

C.L. Bryant

P.L. Ascough

A. Robles Caceres

M. New



Abstract

[1] Mountain rivers play a key role in the delivery of particulate organic carbon (POC) to large river systems and the ocean. Due to the extent of its drainage area and runoff, the Amazon River is one of Earth's most important biogeochemical systems. However, the source of POC eroded from the humid region of the Eastern Andes and the input of fossil POC from sedimentary rocks (POCfossil) remains poorly constrained. Here we collected suspended sediments from the Kosñipata River during flood events to better characterize Andean POC, measuring the nitrogen to organic carbon ratio (N/C), stable carbon isotopes (δ13Corg) and radiocarbon (Δ14Corg). Δ14Corg values ranged from −711‰ to −15‰, and significant linear trends between Δ14Corg, N/C and δ13Corg suggested that this reflects the mixing of POCfossil with very young organic matter (Δ14Corg ~ 50‰) from the terrestrial biosphere (POCnon-fossil). Using N/C and Δ14Corg in an end-member mixing analysis, we quantify the fraction of POCfossil (to within 0.1) and find that it contributes a constant proportion of the suspended sediment mass (0.37 ± 0.03%) and up to 80% of total POC. In contrast, the relative contribution of POCnon-fossil was variable, being most important during the rising limb and peak discharges of flood events. The new data shed light on published measurements of “old” POC (low Δ14Corg) in Andean-fed tributaries of the Amazon River, with their Δ14Corg and δ13Corg values consistent with variable addition of POCfossil. The findings suggest a greater persistence of Andean POC in the lowland Amazon than previously recognized.

Citation

Clark, K., Hilton, R., West, A., Malhi, Y., Gröcke, D., Bryant, C., …New, M. (2013). New views on old carbon in the Amazon river: Insight from the source of organic carbon eroded from the Peruvian Andes. Geochemistry, Geophysics, Geosystems, 14(5), 1644-1659. https://doi.org/10.1002/ggge.20122

Journal Article Type Article
Acceptance Date Mar 21, 2013
Publication Date May 31, 2013
Deposit Date Mar 25, 2013
Publicly Available Date Apr 14, 2015
Journal Geochemistry, Geophysics, Geosystems
Publisher American Geophysical Union
Peer Reviewed Peer Reviewed
Volume 14
Issue 5
Pages 1644-1659
DOI https://doi.org/10.1002/ggge.20122
Keywords Organic carbon, Erosion, Andes, Amazon, Radiocarbon.
Public URL https://durham-repository.worktribe.com/output/1462456

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Copyright Statement
Clark, K. E., R. G. Hilton, A. J. West, Y. Malhi, D. R. Gröcke, C. L. Bryant, P. L. Ascough, A. Robles Caceres, and M. New (2013), New views on “old” carbon in the Amazon River: Insight from the source of organic carbon eroded from the Peruvian Andes, Geochemistry, Geophysics, Geosystems, 14, 1644-1659, DOI: 10.1002/ggge.20122. To view the published open abstract, go to http://dx.doi.org and enter the DOI.






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