High rates of rock organic carbon oxidation sustained as Andean sediment transits the Amazon foreland-floodplain.
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| Title: | High rates of rock organic carbon oxidation sustained as Andean sediment transits the Amazon foreland-floodplain. |
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| Authors: | Dellinger, Mathieu1,2 mathieu.dellinger@univ-smb.fr, Hilton, Robert G.1,3 robert.hilton@earth.ox.ac.uk, Baronas, J. Jotautas4, Torres, Mark A.5, Burt, Emily I.6, Clark, Kasey E.7, Galy, Valier8, Ccahuana Quispe, Adan Julian9, West, A. Joshua6 |
| Source: | Proceedings of the National Academy of Sciences of the United States of America. 9/26/2023, Vol. 120 Issue 39, p1-9. 17p. |
| Subjects: | Oxidation, Sedimentary rocks, Sediments, Floodplains, Carbon |
| Abstract: | The oxidation of organic carbon contained within sedimentary rocks ("petrogenic" carbon, or hereafter OCpetro) emits nearly as much C2 as is released by volcanism, thereby playing a key role in the long-term global C budget. High erosion rates in mountains have been shown to increase OCpetro oxidation. However, these settings also export unweathered material that may continue to react in downstream floodplains. The relative importance of OCpetro oxidation in mountains versus floodplains remains difficult to assess as disparate methods have been used in the different environments. Here, we investigate the sources and fluxes of rhenium (Re) in the Rio Madre de Dios to quantify OCpetro oxidation from the Andes to the Amazon floodplain using a common approach. Dissolved rhenium concentrations (n = 131) range from 0.01 to 63 pmol L-1 and vary depending on lithology and geomorphic setting. We find that >75% of the dissolved Re derives from OCpetro oxidation and that this proportion increases downstream. We estimate that in the Andes, OCpetro oxidation releases 11.2+4.5/-2.8 tC km-2 y-1 of C2, which corresponds to ~41% of the total OCpetro denudation (sum of oxidized and solid OCpetro). A Re mass balance across the Rio Madre de Dios shows that 46% of OCpetro oxidation takes place in the Andes, 14% in the foreland-lowlands, and 40% in the Andean-fed floodplains. This doubling of OCpetro oxidation flux downstream of the Andes demonstrates that, when present, floodplains can greatly increase OCpetro oxidation and C2 release. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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