Old carbon contributes to aquatic emissions of carbon dioxide in the Amazon

Vihermaa, L.E., Waldron, S. , Garnett, M.H. and Newton, J. (2014) Old carbon contributes to aquatic emissions of carbon dioxide in the Amazon. Biogeosciences, 11(1), pp. 3635-3645. (doi:10.5194/bg-11-3635-2014)

Vihermaa, L.E., Waldron, S. , Garnett, M.H. and Newton, J. (2014) Old carbon contributes to aquatic emissions of carbon dioxide in the Amazon. Biogeosciences, 11(1), pp. 3635-3645. (doi:10.5194/bg-11-3635-2014)

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Publisher's URL: http://dx.doi.org/10.5194/bg-11-3635-2014

Abstract

Knowing the rate at which carbon is cycled is crucial to understanding the dynamics of carbon transfer pathways. Recent technical developments now support measurement of the <sup>14</sup>C age of evaded CO<sub>2</sub> from fluvial systems, which provides an important "fingerprint" of the source of C. Here we report the first direct measurements of the <sup>14</sup>C age of effluxed CO<sub>2</sub> from two small streams and two rivers within the western Amazonian Basin. The rate of degassing and hydrochemical controls on degassing are also considered. We observe that CO<sub>2</sub> efflux from all systems except for the seasonal small stream was <sup>14</sup>C -depleted relative to the contemporary atmosphere, indicating a contribution from "old" carbon fixed before ~ 1955 AD. Further, "old" CO<sub>2</sub> was effluxed from the perennial stream in the rainforest; this was unexpected as here connectivity with the contemporary C cycle is likely greatest. The effluxed gas represents all sources of CO<sub>2</sub> in the aquatic system and thus we used end-member analysis to identify the relative inputs of fossil, modern and intermediately aged C. The most likely solutions indicated a contribution from fossil carbon sources of between 3 and 9% which we interpret as being derived from carbonate weathering. This is significant as the currently observed intensification of weather has the potential to increase the future release of old carbon, which can be subsequently degassed to the atmosphere, and so renders older, slower C cycles faster. Thus <sup>14</sup>C fingerprinting of evaded CO<sub>2</sub> provides understanding which is essential to more accurately model the carbon cycle in the Amazon Basin.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Waldron, Professor Susan and Garnett, Dr Mark and Vihermaa, Dr Leena
Authors: Vihermaa, L.E., Waldron, S., Garnett, M.H., and Newton, J.
College/School:College of Science and Engineering > School of Geographical and Earth Sciences
College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Biogeosciences
Publisher:Copernicus Publications
ISSN:1726-4170
ISSN (Online):1726-4189
Copyright Holders:Copyright © 2014 The Authors
First Published:First published in Biogeosciences Discussions 11(1):3635-3645
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
467661Amazon Integrated Carbon Analysis (AMAZONICA)Susan WaldronNatural Environment Research Council (NERC)NE/F005482/1SCHOOL OF GEOGRAPHICAL & EARTH SCIENCES
467662Amazon Integrated Carbon Analysis (AMAZONICA)Susan WaldronNatural Environment Research Council (NERC)NE/F005482/1SCHOOL OF GEOGRAPHICAL & EARTH SCIENCES