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Isotopic Signatures of Methane Emissions from Tropical Fires, Agriculture and Wetlands: The MOYA and ZWAMPS Flights
Nisbet, Euan G. Allen, Grant Fisher, Rebecca E. France, James L. Lee, James D. Lowry, David Andrade, Marcos F. Bannan, Thomas J. Barker, Patrick Bateson, Prudence
Nisbet, Euan G.
Allen, Grant
Fisher, Rebecca E.
France, James L.
Lee, James D.
Lowry, David
Andrade, Marcos F.
Bannan, Thomas J.
Barker, Patrick
Bateson, Prudence
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EPub Date
Publication Date
2021-12-06
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rsta.2021.0112.pdf
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Abstract
We report methane isotopologue data from aircraft and ground measurements in Africa and South America. Aircraft campaigns sampled strong methane fluxes over tropical papyrus wetlands in the Nile, Congo and Zambezi basins, herbaceous wetlands in Bolivian southern Amazonia, and over fires in African woodland, cropland and savannah grassland. Measured methane δ13CCH4 isotopic signatures were in the range −55 to −49‰ for emissions from equatorial Nile wetlands and agricultural areas, but widely −60 ± 1‰ from Upper Congo and Zambezi wetlands. Very similar δ13CCH4 signatures were measured over the Amazonian wetlands of NE Bolivia (around −59‰) and the overall δ13CCH4 signature from outer tropical wetlands in the southern Upper Congo and Upper Amazon drainage plotted together was −59 ± 2‰. These results were more negative than expected. For African cattle, δ13CCH4 values were around −60 to −50‰. Isotopic ratios in methane emitted by tropical fires depended on the C3 : C4 ratio of the biomass fuel. In smoke from tropical C3 dry forest fires in Senegal, δ13CCH4 values were around −28‰. By contrast, African C4 tropical grass fire δ13CCH4 values were −16 to −12‰. Methane from urban landfills in Zambia and Zimbabwe, which have frequent waste fires, had δ13CCH4 around −37 to −36‰. These new isotopic values help improve isotopic constraints on global methane budget models because atmospheric δ13CCH4 values predicted by global atmospheric models are highly sensitive to the δ13CCH4 isotopic signatures applied to tropical wetland emissions. Field and aircraft campaigns also observed widespread regional smoke pollution over Africa, in both the wet and dry seasons, and large urban pollution plumes. The work highlights the need to understand tropical greenhouse gas emissions in order to meet the goals of the UNFCCC Paris Agreement, and to help reduce air pollution over wide regions of Africa. This article is part of a discussion meeting issue 'Rising methane: is warming feeding warming? (part 2)'.
Citation
Nisbet, E. G., Allen, G., Fisher, R. E., France, J. L., Lee, J. D., Lowry, D., Andrade, M. F., Bannan, T. J., Barker, P., Bateson, P., Bauguitte, S. J.-B., Bower, K. N., Broderick, T. J., Chibesakunda, F., Cain, M., Cozens, A. E., Daly, M. C., Ganesan, A. L., Jones, A. E., ... Wilde, S. E. (2022). Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 380(2215), 20210112. https://doi.org/10.1098/rsta.2021.0112
Publisher
The Royal Society
Journal
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Research Unit
DOI
10.1098/rsta.2021.0112
PubMed ID
PubMed Central ID
Type
Article
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Description
© 2021 The Authors.
Series/Report no.
ISSN
1364-503X
EISSN
1471-2962
ISBN
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Sponsors
Funder: Natural Environment Research Council; Id: http://dx.doi.org/10.13039/501100000270; Grant(s): NE/N016238/1 MOYA The Global Methane Budget, NE/P019641/1 New methodologies for removal of meth, NE/S00159X/1 ZWAMPS Quantifying Methane Emissions