Atmospheric Lifetimes of Long-Lived Halogenated Species

The atmospheric lifetimes of the fluorinated gases CF4, C2F6, c-C4F8, (CF3)2c-C4F6, C5F12, C6F14, C2F5Cl, C2F4C12, CF3Cl, and SF6 are of concern because of the effects that these long-lived compounds acting as greenhouse gases can have on global climate. The possible atmospheric loss processes of these gases were assessed by determining the rate coefficients for the reactions of these gases with O(1D), H, and OH and the absorption cross sections at 121.6 nanometers in the laboratory and using these data as input to a two-dimensional atmospheric model. The lifetimes of all the studied perfluoro compounds are >2000 years, and those of CF3Cl, CF3CF2Cl, and CF2ClCF2Cl are >300 years. If released into the atmosphere, these molecules will accumulate and their effects will persist for centuries or millennia.

[1]  D. Neumark,et al.  Fast beam studies of N3 photodissociation , 1991 .

[2]  C. B. Farmer,et al.  Infrared spectroscopic detection of sulfur hexafluoride (sf6) in the lower stratosphere and upper troposphere , 1990 .

[3]  Ghanshyam L. Vaghjiani,et al.  Photodissociation of H2O2 and CH3OOH at 248 nm and 298 K: Quantum yields for OH, O(3P) and H(2S) , 1990 .

[4]  J. Houghton,et al.  Climate change : the IPCC scientific assessment , 1990 .

[5]  S. Lal,et al.  CF4 and C2F6 in the atmosphere , 1987 .

[6]  M. Khalil,et al.  Atmospheric carbontetrafluoride (CF4): Sources and trends , 1985 .

[7]  Rolando R. Garcia,et al.  The effect of breaking gravity waves on the dynamics and chemical composition of the mesosphere and lower thermosphere , 1985 .

[8]  A. Ravishankara,et al.  Reaction of hydrogen atom with benzene. Kinetics and mechanism , 1984 .

[9]  J. Wiesenfeld,et al.  Collisional deactivation of oxygen(1D2) by the halomethanes. Direct determination of reaction efficiency , 1981 .

[10]  R. Cicerone,et al.  Atmospheric Carbon Tetrafluoride: A Nearly Inert Gas , 1979, Science.

[11]  H. Gies,et al.  Temperature dependence of the molecular oxygen photoabsorption cross section near the H Lyman α line , 1977 .

[12]  D. Husain,et al.  Absolute reaction rates of oxygen(21D2) with halogenated paraffins by atomic absorption spectroscopy in the vacuum ultraviolet , 1976 .

[13]  G. Streit,et al.  Absolute rate constant determinations for the deactivation of O(1D) by time resolved decay of O(1D) →O(3P) emission , 1976 .

[14]  R. Atkinson,et al.  Relative rate constants for the reaction of O(1D) atoms with fluorocarbons and N2O , 1974 .

[15]  J. Doucet,et al.  Vacuum ultraviolet and photoelectron spectra of fluoroethanes , 1974 .

[16]  P. Sauvageau,et al.  Vacuum ultraviolet absorption spectra of fluoromethanes , 1973 .

[17]  J. Doucet,et al.  Vacuum ultraviolet and photoelectron spectra of fluoro‐chloro derivatives of methane , 1973 .

[18]  E. A. Fletcher,et al.  Fluorocarbon combustion studies III—Deflagration in perfluorocyclobutane-oxygen mixtures. Spatial velocities and limits in a 2·5 cm tube , 1968 .