Amazon Capims (floating grassmats): A source of 13C enriched methane to the troposphere

The 13C isotopic composition of methane emitted to the troposphere from Amazon capims (floating grassmats) ranged from −36.9 to −48.0‰, averaging −44.4 ± 4.2‰. All pools of methane associated with the grassmats were 13C enriched; methane withdrawn from plant stems ranged from −39 to −49‰ while bubbl...

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Bibliographic Details
Main Authors: Chanton, J., Crill, P., Bartlett, K., Martens, C.
Other Authors: University of North Carolina at Chapel Hill
Format: Article in Journal/Newspaper
Language:English
Published: 1989
Subjects:
isotopic composition
methane
grassmat
Brazil
Amazonia
floating grassmat
capims
South America
carbon isotope
Arctic
Online Access:https://doi.org/10.17615/c9yd-2w22
https://cdr.lib.unc.edu/downloads/n583z4678?file=thumbnail
https://cdr.lib.unc.edu/downloads/n583z4678
Description
Summary:The 13C isotopic composition of methane emitted to the troposphere from Amazon capims (floating grassmats) ranged from −36.9 to −48.0‰, averaging −44.4 ± 4.2‰. All pools of methane associated with the grassmats were 13C enriched; methane withdrawn from plant stems ranged from −39 to −49‰ while bubbles stirred from the root mat averaged −41.4‰. As the CH4 flux from these habitats makes up some 40% of the total flux from the Amazon floodplain, CH4 emissions from the region as a whole must be enriched in the heavy carbon isotope. Methane withdrawn from the stems of five genera of rooted macrophytes ranging in latitude from the Florida Everglades to the Alaskan Arctic exhibited 13C enrichment relative to the sedimentary methane bubble reservoir. Several hypotheses based upon isotopic fractionation by methane transport, oxidation and production processes are proposed to explain this phenomenon.

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