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1,2-Dichlorohexafluoro-Cyclobutane (1,2-c-C4F6Cl2, R-316c) a Potent Ozone Depleting Substance and Greenhouse Gas: Atmospheric Loss Processes, Lifetimes, and Ozone Depletion and Global Warming Potentials for the (E) and (Z) stereoisomersThe atmospheric processing of (E)- and (Z)-1,2-dichlorohexafluorocyclobutane (1,2-c-C4F6Cl2, R-316c) was examined in this work as the ozone depleting (ODP) and global warming (GWP) potentials of this proposed replacement compound are presently unknown. The predominant atmospheric loss processes and infrared absorption spectra of the R-316c isomers were measured to provide a basis to evaluate their atmospheric lifetimes and, thus, ODPs and GWPs. UV absorption spectra were measured between 184.95 to 230 nm at temperatures between 214 and 296 K and a parametrization for use in atmospheric modeling is presented. The Cl atom quantum yield in the 193 nm photolysis of R- 316c was measured to be 1.90 +/- 0.27. Hexafluorocyclobutene (c-C4F6) was determined to be a photolysis co-product with molar yields of 0.7 and 1.0 (+/-10%) for (E)- and (Z)-R-316c, respectively. The 296 K total rate coefficient for the O(1D) + R-316c reaction, i.e., O(1D) loss, was measured to be (1.56 +/- 0.11) × 10(exp −10)cu cm/ molecule/s and the reactive rate coefficient, i.e., R-316c loss, was measured to be (1.36 +/- 0.20) × 10(exp −10)cu cm/molecule/s corresponding to a approx. 88% reactive yield. Rate coefficient upper-limits for the OH and O3 reaction with R-316c were determined to be <2.3 × 10(exp −17) and <2.0 × 10(exp −22)cu cm/molecule/s, respectively, at 296 K. The quoted uncertainty limits are 2(sigma) and include estimated systematic errors. Local and global annually averaged lifetimes for the (E)- and (Z)-R-316c isomers were calculated using a 2-D atmospheric model to be 74.6 +/- 3 and 114.1 +/-10 years, respectively, where the estimated uncertainties are due solely to the uncertainty in the UV absorption spectra. Stratospheric photolysis is the predominant atmospheric loss process for both isomers with the O(1D) reaction making a minor, approx. 2% for the (E) isomer and 7% for the (Z) isomer, contribution to the total atmospheric loss. Ozone depletion potentials for (E)- and (Z)-R-316c were calculated using the 2-D model to be 0.46 and 0.54, respectively. Infrared absorption spectra for (E)- and (Z)-R-316c were measured at 296 K and used to estimate their radiative efficiencies (REs) and GWPs; 100-year time-horizon GWPs of 4160 and 5400 were obtained for (E)- and (Z)-R-316c, respectively. Both isomers of R-316c are shown in this work to be long-lived ozone depleting substances and potent greenhouse gases.
Document ID
20140012685
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Papadimitriou, Vassileios C.
(National Oceanic and Atmospheric Administration Boulder, CO, United States)
McGillen, Max R.
(National Oceanic and Atmospheric Administration Boulder, CO, United States)
Smith, Shona C.
(National Oceanic and Atmospheric Administration Boulder, CO, United States)
Jubb, Aaron M.
(National Oceanic and Atmospheric Administration Boulder, CO, United States)
Portmann, Robert W.
(National Oceanic and Atmospheric Administration Boulder, CO, United States)
Hall, Bradley D.
(National Oceanic and Atmospheric Administration Boulder, CO, United States)
Fleming, Eric L.
(Science Systems and Applications, Inc. Lanham, MD, United States)
Jackman, Charles H.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Burkholder, James B.
(National Oceanic and Atmospheric Administration Boulder, CO, United States)
Date Acquired
September 26, 2014
Publication Date
September 30, 2013
Publication Information
Publication: Journal of Physical Chemistry: Part A
Volume: 117
Issue: 43
Subject Category
Geosciences (General)
Report/Patent Number
GSFC-E-DAA-TN10776
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
UV cross section
photolysis
chlorofluorocarbon
Ozone depleting substance
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