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Seasonal C-13 variations of methane from an anoxic marine sedimentRecent analyses of glacial ice suggest that the atmospheric concentration of methane has doubled in the last several hundred years, presumably due to anthropogenic perturbations of the relevant biogeochemical cycles. In principal, carbon isotopic measurements of atmospheric methane would provide information concerning changes in the sources and sinks of methane. The isotopic composition of methane is dependent on the source of the methane carbon, the mechanism of methane synthesis, and the degree and mode of oxidation which the methane has experienced. Unfortunately, few carbon isotopic measurements of atmospheric variations have been reported, so conclusions about temporal isotopic variations cannot be made. Also, before isotopic measurements of atmospheric methane can be used to identify changes in methane isotopic composition from different sources must be obtained. Methane bubbles from the anoxic sediments of Cape Lookout Bight, NC exhibit seasonal C-13 variations. The C-13 values ranged from -58 in August to -64 in the winter months with the evolution of the C-13 enriched gas occurring during periods of peak methane production. Even though a few intramolecular C-13 measurements of the pore water acetate have been made (methyl group, -26 per mil; carbonyl, -6 per mil), it is not clear how the acetate fermentation pathway affects the methane C-13/C-12 composition.
Document ID
19930073166
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Blair, Neal
(North Carolina State Univ. Raleigh., United States)
Desmarais, David S.
(NASA Ames Research Center Moffett Field, CA, United States)
Martens, Christopher S.
(North Carolina Univ. Chapel Hill., United States)
Date Acquired
August 16, 2013
Publication Date
January 1, 1985
Publication Information
Publication: First Symposium on Biospheric Research
Subject Category
Environment Pollution
Accession Number
93N70613
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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