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Atmospheric halocarbons: Evidence in favor of reduced average hydroxyl radical concentration in the troposphere
Author(s) -
Singh Hanwant B.
Publication year - 1977
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/gl004i003p00101
Subject(s) - troposphere , atmospheric sciences , atmospheric chemistry , halocarbon , environmental science , hydroxyl radical , stratosphere , atmospheric models , ozone , climatology , environmental chemistry , chemistry , meteorology , atmosphere (unit) , radical , physics , geology , organic chemistry
Data are provided on the May 1976 northern hemispheric background concentrations of 13 halocarbons, SF 6 , and N 2 O. A model is developed that permits an easy comparison of atmospheric lifetimes, emissions, and ambient concentrations. Our measurements indicate that atmospheric levels of CCl 2 F 2 (F12) and CCl 3 F(F11) are consistent with an average residence time of 50 (±33) and 36 (±8) years respectively. The tropospheric lifetimes of reactive species such as CH 3 CCl 3 , CHCl 3 , and C 2 Cl 4 are found to be 7.2 (±1.2), 1.7 (±0.4), and 0.4 (±0.1) years respectively. These longer lifetimes of tropospherically reactive species are inconsistent with the existing knowledge of atmospheric chemistry. Our conservative analysis of atmospheric halocarbon data shows that average HO concentrations must be 2 to 6 × 10 5 HO/ml instead of the accepted range of 10 to 30 × 10 5 HO/ml. These lower HO values tend to resolve the apparent discrepancies in the biospheric budgets and distribution of chlorinated hydrocarbons and CO. The tropospheric and stratospheric implications of reduced HO levels are discussed.