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Implications of the large carbon kinetic isotope effect in the reaction CH 4 + Cl for the 13 C/ 12 C ratio of stratospheric CH 4
Author(s) -
Bergamaschi P.,
Brühl C.,
Brenninkmeijer C. A. M.,
Saueressig G.,
Crowley J. N.,
Grooß J. U.,
Fischer H.,
Crutzen P. J.
Publication year - 1996
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 - 10.1029/96gl02139
Subject(s) - stratosphere , kinetic isotope effect , isotope , chemical reaction kinetics , kinetic energy , chemical kinetics , isotopes of carbon , chemistry , analytical chemistry (journal) , kinetics , atmospheric sciences , physics , environmental chemistry , deuterium , atomic physics , nuclear physics , quantum mechanics
Recent investigations of the carbon kinetic isotope effect (KIE) of the reaction CH 4 + Cl yielded KIE Cl = 1.066±0.002 at 297 K (increasing to 1.075±0.005 at 223 K) [ Saueressig et al. , 1995]. In order to assess the effect of the exceptionally large KIE cl on δ 13 C of stratospheric CH 4 we applied a two‐dimensional, time dependent chemical transport model. The model results demonstrate the strong influence of the CH 4 + Cl reaction on δ 13 CH 4 in particular in the middle and upper stratosphere, where this reaction contributes several tens of percent to the total CH 4 sink. The Cl sink helps to explain the relatively large overall isotope fractionation of 1.010–1.012 observed in the lower stratosphere [ Brenninkmeijer et al. , 1995; Brenninkmeijer et al. , 1996], even though the model results predict a smaller effect than observed.