A very limited role of tropospheric chlorine as a sink of the greenhouse gas methane
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Published:2018-07-12
Issue:13
Volume:18
Page:9831-9843
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ISSN:1680-7324
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Container-title:Atmospheric Chemistry and Physics
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language:en
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Short-container-title:Atmos. Chem. Phys.
Author:
Gromov SergeyORCID, Brenninkmeijer Carl A. M., Jöckel PatrickORCID
Abstract
Abstract. Unexpectedly large seasonal phase differences between CH4
concentration and its 13C ∕ 12C isotopic ratio and
their inter-annual variations observed in southern hemispheric time series
have been attributed to the Cl + CH4 reaction, in which
13CH4 is discriminated strongly compared to OH + CH4,
and have provided the only (indirect) evidence of a hemispheric-scale
presence of oxidative cycle-relevant quantities of tropospheric atomic Cl.
Our analysis of concurrent New Zealand and Antarctic time series of
CH4 and CO mixing and isotope ratios shows that a corresponding
13C ∕ 12C variability is absent in CO. Using
the AC-GCM EMAC model and isotopic mass balancing for comparing the periods
of presumably high and low Cl, it is shown that variations in extra-tropical
Southern Hemisphere Cl cannot have exceeded
0.9 × 103 atoms cm−3. It is demonstrated that the
13C ∕ 12C ratio of CO is a sensitive indicator for
the isotopic composition of reacted CH4 and therefore for its
sources. Despite ambiguities about the yield of CO from CH4 oxidation
(with this yield being an important factor in the budget of CO) and
uncertainties about the isotopic composition of sources of CO (in particular
biomass burning), the contribution of Cl to the removal of CH4 in the
troposphere is probably much lower than currently assumed.
Publisher
Copernicus GmbH
Subject
Atmospheric Science
Reference52 articles.
1. Allan, W., Manning, M. R., Lassey, K. R., Lowe, D. C., and Gomez, A. J.:
Modeling the variation of δ13C in atmospheric methane: Phase
ellipses and the kinetic isotope effect, Global Biogeochem. Cy., 15,
467–481, https://doi.org/10.1029/2000gb001282, 2001. 2. Allan, W., Struthers, H., and Lowe, D. C.: Methane carbon isotope effects caused
by atomic chlorine in the marine boundary layer: Global model results
compared with Southern Hemisphere measurements, J. Geophys. Res.-Atmos., 112, D04306,
https://doi.org/10.1029/2006jd007369, 2007. 3. Baker, A. K., Rauthe-Schöch, A., Schuck, T. J., Brenninkmeijer, C. A. M., van
Velthoven, P. F. J., Wisher, A., and Oram, D. E.: Investigation of chlorine radical
chemistry in the Eyjafjallajökull volcanic plume using observed
depletions in non-methane hydrocarbons, Geophys. Res. Lett., 38, L13801,
https://doi.org/10.1029/2011GL047571, 2011. 4. Baker, A. K., Sauvage, C., Thorenz, U. R., van Velthoven, P., Oram, D. E., Zahn, A.,
Brenninkmeijer, C. A. M., and Williams, J.: Evidence for strong, widespread
chlorine radical chemistry associated with pollution outflow from
continental Asia, Sci. Rep., 6, 36821, https://doi.org/10.1038/srep36821,
2016. 5. Bergamaschi, P., Hein, R., Brenninkmeijer, C. A. M., and Crutzen, P. J.: Inverse
modeling of the global CO cycle 2. Inversion of 13C ∕ 12C and
18O ∕ 16O isotope ratios, J. Geophys. Res.-Atmos., 105, 1929–1945,
https://doi.org/10.1029/1999jd900819, 2000.
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