HAL: ird-00588739, version 1

DOI: 10.1130/G30608

IRD Horizon id: fdi:010048006

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Geology 38, 3 (2010) 255-258

Oxidation of petrogenic organic carbon in the Amazon floodplain as a source of atmospheric CO2

Julien Bouchez (  Corresponding author ) 1, Olivier Beyssac 2, Valier Galy 3, Jérôme Gaillardet 1, Christian France-Lanord 4, Laurence Maurice 5, Patricia Moreira-Turcq 5

(2010)

The two long-term sources of atmospheric carbon are CO2 degassing from metamorphic and volcanic activity, and oxidation of organic carbon (OC) contained in sedimentary rocks, or petrogenic organic carbon (OCpetro). The latter fl ux is still poorly constrained. In this study, we report particulate organic carbon content and 14C activity measurements in Amazon River sediments, which allow for estimates of the OCpetro content of these sediments. A large decrease of OCpetro content in riverine sediments is observed from the outlet of the Andes to the mouth of the large tributaries. This loss reveals oxidation of OCpetro during transfer of sediments in the floodplain, and results in an escape of ~0.25 Mt C/yr to the atmosphere, which is on the same order of magnitude as the CO2 consumption by silicate weathering in the same area. Raman microspectroscopy investigations show that graphite is the most stable phase with respect to this oxidation process. These results emphasize the significance of OCpetrooxidation in large river floodplains in the global carbon cycle.

1:	Institut de Physique du Globe de Paris (IPGP)
	CNRS : UMR7154 – INSU – IPG PARIS – Université Pierre et Marie Curie [UPMC] - Paris VI – Université Paris VII - Paris Diderot – Université de la Réunion
2:	Laboratoire de géologie de l'ENS (LGE)
	CNRS : UMR8538 – INSU – Ecole normale supérieure de Paris - ENS Paris
3:	Woods Hole Oceanographic Institution
	Woods Hole Oceanographic Institution
4:	Centre de recherches petrographiques et géochimiques (CRPG)
	CNRS : UPR2300 – INSU
5:	Laboratoire des Mécanismes et Transfert en Géologie (LMTG)
	CNRS : UMR5563 – Observatoire Midi-Pyrénées – Université Paul Sabatier [UPS] - Toulouse III – Institut de recherche pour le développement [IRD] : UMR154

subject

:

Sciences of the Universe/Earth Sciences/Hydrology Sciences of the Universe/Earth Sciences/Geochemistry Environmental Sciences/Global Changes

keyword(s): CARBONE ORGANIQUE – GAZ CARBONIQUE – SEDIMENT – COURS D'EAU – SEDIMENTATION FLUVIATILE – CYCLE BIOGEOCHIMIQUE – MATIERE ORGANIQUE PARTICULEE – ANALYSE ISOTOPIQUE – PLAINE INONDABLE – AMAZONIE – ANDES – AMAZONE BASSIN VERSANT

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From: Francine Delmas <>

Submitted on: Tuesday, 26 April 2011 13:43:14

Updated on: Wednesday, 15 June 2011 17:02:51