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Comment on “Detection of multiply deuterated methane in the atmosphere”
Author(s) -
Kaye Jack A.,
Jackman Charles H.
Publication year - 1990
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl017i005p00659
Subject(s) - deuterium , methane , stratosphere , troposphere , kinetic isotope effect , atmosphere (unit) , isotope , atmospheric sciences , abundance (ecology) , chemistry , hydroxyl radical , atmospheric chemistry , environmental chemistry , environmental science , physics , ozone , meteorology , radical , nuclear physics , organic chemistry , fishery , biology
It has recently been reported [Mroz et al., 1989] that the abundance of mass‐20 isotopes of methane (CH 4 ), which correspond to either of the highly deuterated forms 12 CD 4 or 13 CHD 3 , is some 500 times that expected based on the statistical combination of H, D, 12 C, and 13 C and observed CH 4 amounts. These authors then suggested that it is possible that the enhanced concentration of these species is due to their longer lifetimes than that of CH 4 itself because of their slower rate of loss by reaction with the hydroxyl radical (OH). We have tested this hypothesis with a two‐dimensional atmospheric chemical‐dynamical model and found that no large enhancements of 13 CHD 3 and 12 CD 4 can result in this way; in the troposphere enhancement factors of between 4 and 5 and between 7 and 8, respectively, were found, with enhancements becoming only slightly larger (14 and 25, respectively) in the stratosphere. The factor of 500 enhancement reported by Mroz et al. must have other origins.