Open AccessIsotopic signatures of methane emissions from tropical fires, agriculture and wetlands: the MOYA and ZWAMPS flights
Author(s) -
AUTHOR_ID,
E. G. Nisbet,
Grant Allen,
Rebecca E. Fisher,
James L. France,
James Lee,
David Lowry,
Marcos Andrade,
Thomas J. Bannan,
Patrick Barker,
Prudence Bateson,
Stéphane Bauguitte,
Keith Bower,
Tim Broderick,
Francis Chibesakunda,
Michelle Cain,
Alice E. Cozens,
M. C. Daly,
Anita L. Ganesan,
A. E. Jones,
Musa Lambakasa,
Mark F. Lunt,
Archit Mehra,
Isabel Moreno,
Dominika Pasternak,
Paul I. Palmer,
Carl J. Percival,
Joseph Pitt,
Amber Riddle,
Matthew Rigby,
Jacob Shaw,
Angharad C. Stell,
Adam Vaughan,
N. J. Warwick,
Shona Wilde
Publication year - 2021
Publication title -
philosophical transactions - royal society. mathematical, physical and engineering sciences/philosophical transactions - royal society. mathematical, physical and engineering sciences
Language(s) - English
Resource type - Journals
eISSN - 1471-2962
pISSN - 1364-503X
DOI - 10.1098/rsta.2021.0112
Subject(s) - wetland , environmental science , methane , amazon rainforest , tropics , tropical savanna climate , isotopic signature , dry season , hydrology (agriculture) , geography , ecology , ecosystem , geology , stable isotope ratio , physics , cartography , geotechnical engineering , quantum mechanics , biology
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 methaneδ 13 CCH4 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 similarδ 13 CCH4 signatures were measured over the Amazonian wetlands of NE Bolivia (around −59‰) and the overallδ 13 CCH4 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,δ 13 CCH4 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,δ 13 CCH4 values were around −28‰. By contrast, African C4 tropical grass fireδ 13 CCH4 values were −16 to −12‰. Methane from urban landfills in Zambia and Zimbabwe, which have frequent waste fires, hadδ 13 CCH4 around −37 to −36‰. These new isotopic values help improve isotopic constraints on global methane budget models because atmosphericδ 13 CCH4 values predicted by global atmospheric models are highly sensitive to theδ 13 CCH4 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)'.