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Vertical profile of the carbon isotopic ratio of stratospheric methane over Japan
Author(s) -
Sugawara S.,
Nakazawa T.,
Shirakawa Y.,
Kawamura K.,
Aoki S.,
Machida T.,
Honda H.
Publication year - 1997
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 - 10.1029/97gl03044
Subject(s) - stratosphere , methane , tropopause , isotopes of carbon , fractionation , carbon fibers , isotopic ratio , analytical chemistry (journal) , diffusion , atmospheric sciences , chemistry , environmental science , environmental chemistry , isotope , total organic carbon , materials science , geology , physics , thermodynamics , nuclear physics , organic chemistry , composite number , composite material
Stratospheric air samples were collected over Japan on August 31, 1994 using a balloon‐borne cryogenic sampler and then analyzed for the CH 4 concentration and δ 13 C in CH 4 . The δ 13 C value increased from about −47.5‰ at the tropopause to about −38.9‰ at 34.7 km, accompanied by a rapid decrease of the CH 4 concentration with height. From the measured values of the CH 4 concentration and δ 13 C, the apparent carbon isotopic fractionation factor was estimated to be 1.0131±0.0006. The contributions of the chemical CH 4 reactions with OH, O(¹D) and Cl were also examined by using an one‐dimensional photochemical‐diffusion model. It is suggested from this examination that the reaction of CH 4 with Cl is especially important for δ 13 C in the stratosphere.