Correspondence/Rebuttal pubs.acs.org/est
Comment on “Airborne Trifluoroacetic Acid and Its Fraction from the Degradation of HFC-134a in Beijing, China” The authors declare no competing financial interest.
W
u et al.1 reported an assessment of the fraction of airborne trifluoroacetic acid (TFA) resulting from atmospheric degradation of HFC-134a (CF3CFH2) in Beijing, China. In the box model used to estimate the trifluoroacetic acid (TFA) flux, Wu et al. used a molar yield of TFA from HFC-134a of 0.36. This value was taken from the modeling study by Kanakidou et al.2 We comment that since the work of Kanakidou et al. was published, it has become well established that chemical activation can be important in determining the atmospheric fate of alkoxy radicals.3 In the atmospheric oxidation of HFC-134a this effect reduces the yield of TFA by approximately a factor of 2.5.4,5 Accounting for this effect reduces the contribution of atmospheric degradation of HFC-134a to airborne TFA in Beijing from the value of 14% (6−33%) reported by Wu et al. to approximately 6% (2−13%). This revision strengthens the conclusion by Wu et al. that unknown sources other than HFC134a oxidation are present in the air over Beijing.
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REFERENCES
(1) Wu, J.; Martin, J. W.; Zhai, Z.; Lu, K.; Fang, X.; Jin, H. Airborne trifluoroacetic acid and its fraction from the degradation of HFC-134a in Beijing, China. Environ. Sci. Technol. 2014, 48, 3675−3681. (2) Kanakidou, M.; Dentener, F. J.; Crutzen, P. J. A global 3dimensional study of the fate of HCFCs and HFC-134a in the troposphere. J. Geophys. Res. 1995, 100, 18781−18801. (3) Wallington, T. J.; Hurley, M. D.; Fracheboud, J. M.; Orlando, J. J.; Tyndall, G. S.; Sehested, J.; Møgelberg, T. E.; Nielsen, O. J. Role of excited CF3CFHO radicals in the atmospheric chemistry of HFC134a. J. Phys. Chem. 1996, 100, 18116−18122. (4) Schneider, W. F.; Wallington, T. J.; Barker, J. R.; Stahlberg, E. A. CF3CFHO Radical: Decomposition vs. reaction with O2. Ber. BunsenGes. 1998, 102, 1850−1856. (5) Orlando, J. J.; Tyndall, G. S.; Wallington, T. J. The atmospheric chemistry of alkoxy radicals. Chem. Rev. 2003, 103, 4657−4689.
T. J. Wallington* Systems Analytics and Environmental Sciences, Ford Motor Company, Mail Drop RIC-2122, Dearborn, Michigan 48121-2053, United States
J. J. Orlando G. S. Tyndall Atmospheric Chemistry Division National Center for Atmospheric Research, P.O. Box 3000, Boulder, Colorado 80307, United States
O. J. Nielsen
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Copenhagen Center for Atmospheric Research, Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
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[email protected]. Notes
While this article is believed to contain correct information, Ford Motor Company (Ford) does not expressly or impliedly warrant, nor assume any responsibility, for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe the rights of third parties. Reference to any commercial product or process does not constitute its endorsement. This article does not provide financial, safety, medical, consumer product, or public policy advice or recommendation. Readers should independently replicate all experiments, calculations, and results. The views and opinions expressed are of the authors and do not necessarily reflect those of Ford. This disclaimer may not be removed, altered, superseded or modified without prior Ford permission. The National Center for Atmospheric Research is operated by the University Corporation for Atmospheric Research, under the sponsorship of the National Science Foundation. © 2014 American Chemical Society
Published: July 24, 2014 9948
dx.doi.org/10.1021/es502485w | Environ. Sci. Technol. 2014, 48, 9948−9948
