Open AccessOxygen isotope composition of carbon dioxide in the middle atmosphere
Author(s) -
Barth Volker,
Zahn Andreas
Publication year - 1997
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/97jd00609
Subject(s) - atmosphere (unit) , stratosphere , ozone , carbon dioxide , isotope fractionation , isotope , isotopes of oxygen , carbon dioxide in earth's atmosphere , oxygen , isotopes of carbon , photodissociation , carbon fibers , fractionation , analytical chemistry (journal) , mass independent fractionation , stable isotope ratio , isotopic signature , chemistry , environmental chemistry , atmospheric sciences , materials science , geology , total organic carbon , photochemistry , physics , meteorology , organic chemistry , quantum mechanics , composite number , composite material , nuclear chemistry
We present model calculations to investigate the isotopic behavior of both heavy carbon dioxide molecules C 17 O 16 O and C 18 O 16 O in the stratosphere and mesosphere. For this purpose the existing theory of 18 O transfer between O 3 and CO 2 via O( 1 D ) and the electronically excited complex CO 3 *, as proposed by Yung et al . [1991], is extended to 17 O. Our one‐dimensional model agrees well with atmospheric measurements performed till now, when reasonable assumptions for the isotopic composition of ozone in the middle atmosphere are made, and when in addition a mass‐dependent fractionation process during the transfer of oxygen atoms is included. Best agreement between model results and atmospheric CO 2 isotope data is obtained by assuming (1) an averaged O 3 isotope composition in the middle atmosphere of δ 17 O = (12.5±1.5)% and δ 18 O = (16±1.5)% (versus Vienna standard mean ocean water) and (2) a mass‐dependent isotope fractionation during the O atom transfer via CO 3 * of (32±7)‰ for 17 O and (64±14)‰ for 18 O, both relative to 16 O. Effects of CO 2 photolysis and its reformation via the reaction CO + OH → CO 2 + H on the CO 2 isotope composition are found to be small and may be neglected.