February 28, 2007
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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999
FROM VOLUME 5, NUMBER 5, MAY 1992
HALOCARBONS: TROPOSPHERIC CHEMISTRY
"Estimating Tropospheric Lifetimes and Ozone-Depletion Potentials of
One- and Two-Carbon Hydrofluorocarbons and Hydrochlorofluorocarbons," J.S.
Nimitz (Eng. Res. Inst., Univ. New Mexico, Albuquerque NM 87131), S.R. Skaggs,
Environ. Sci. Technol., 26(4), 739-744, Apr. 1992.
Makes estimates for 53 HFCs and HCFCs based on theory and on the authors'
analysis, to help make choices among CFC alternatives based on environmental
considerations. In many cases, the depletion potentials of chlorine-containing
compounds are below 0.001.
"Tropospheric Lifetimes of Potential CFC Replacements: Rate
Coefficients for Reaction with Hydroxyl Radical," D.L. Cooper (Dept. Chem.,
Univ. Liverpool, POB 147, Liverpool L69 3BX, UK), T.P. Cunningham et al., Atmos.
Environ., 26A(7), 1331-1334, 1992.
To determine the rate of removal of potential CFC replacements by reaction
with the hydroxyl radical, approximate linear correlations were investigated
that allow the prediction of relevant rate constants for partially fluorinated
hydrocarbons. Differences between ethers and alkanes are discussed, as well as
dependence of lifetime on degree of fluorination.
"Chemical Kinetics of the Reactions of the OH Radical with Several
Hydrochlorofluoropropanes," D.D. Nelson (Aerodyne Res. Inc., 45 Manning
Rd., Billerica MA 01821), M.S. Zahniser, C.E. Kolb, J. Phys. Chem., 96(1),
249-253, Jan. 9, 1992.
Rate constants were measured for HCFC-225ca, HCFC-225cb and HCFC-243cc with
the discharge flow technique. Results are used to calculate tropospheric
lifetimes of 4, 8 and 44 years, respectively.
"Ultraviolet Absorption Spectra and Kinetics of the Self Reaction of
CH1Br and CH1BrO2 Radicals in the Gas Phase and 298 K," O.J. Nielson
(Environ. Dept., Riso Nat. Lab., DK-4000 Roskilde, Denmark), J. Munk et al.,
ibid., 95(22), 8714-8719, Oct. 31, 1991.
To further understand the atmospheric fate of halogen-containing compounds,
results of experiments using pulse radiolysis and an FTIR spectrometer are
discussed with respect to similar studies on peroxy radicals.
"Rate Constants for the Gas-Phase Reactions of OH Radicals with
CH3CHF2 and CHCl2CF3 over the Temperature Range 295-388 K," O.J. Nielson
(addr. above), Chem. Phys. Lett., 187(3), 286-290, 1991. Results
using the absolute rate technique of pulse radiolysis combined with kinetic
spectroscopy are discussed in light of the important role these species play as
alternatives to fully halogenated CFCs.
"UV Gas- and Liquid-Phase Absorption Cross Section Measurements of
Hydrochlorofluorocarbons HCFC-225ca and HCFC-225cb," W. Braun (Chem.
Kinetics Div., Nat. Inst. Standards & Technol., Gaithersburg MD 20899), A.
Fahr et al., J. Geophys. Res., 96(D7), 13,009-13,015, July 20,
1991. Absorption cross sections derived from measurements in the liquid phase
can, with appropriate correction factors, be converted into the accurate
gas-phase values for low cross sections that are important to determining
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