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Ozone depletion potential of CH_3Br

Ko, Malcolm K. W. and Sze, Nien Dak and Scott, Courtney and Rodríguez, José M. and Weisenstein, Debra K. and Sander, Stanley P. (1998) Ozone depletion potential of CH_3Br. Journal of Geophysical Research. Atmospheres, 103 (D21). pp. 28187-28195. ISSN 2169-897X.

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The ozone depletion potential (ODP) of methyl bromide (CH_3Br) can be determined by combining the model‐calculated bromine efficiency factor (BEF) for CH_3Br and its atmospheric lifetime. This paper examines how changes in several key kinetic data affect BEF. The key reactions highlighted in this study include the reaction of BrO + HO_2, the absorption cross section of HOBr, the absorption cross section and the photolysis products of BrONO_2, and the heterogeneous conversion of BrONO_2 to HOBr and HNO_3 on aerosol particles. By combining the calculated BEF with the latest estimate of 0.7 year for the atmospheric lifetime of CH_3Br, the likely value of ODP for CH_3Br is 0.39. The model‐calculated concentration of HBr (∼0.3 pptv) in the lower stratosphere is substantially smaller than the reported measured value of about 1 pptv. Recent publications suggested models can reproduce the measured value if one assumes a yield for HBr from the reaction of BrO + OH or from the reaction of BrO + HO_2. Although the DeMore et al. [1997] evaluation concluded any substantial yield of HBr from BrO + HO_2 is unlikely, for completeness, we calculate the effects of these assumed yields on BEF for CH_3Br. Our calculations show that the effects are minimal: practically no impact for an assumed 1.3% yield of HBr from BrO + OH and 10% smaller for an assumed 0.6% yield from BrO + HO_2.

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Sander, Stanley P.0000-0003-1424-3620
Alternate Title:Ozone depletion potential of CH3Br
Additional Information:© 1998 American Geophysical Union. (Received February 6, 1998; revised July 23, 1998; accepted July 28, 1998.) Paper number 98JD02537. Work at AER is supported by the Methyl Bromide Global Coalition and by the National Aeronautics and Space Administration (NASA) Atmospheric Chemistry Modeling and Analysis Program (ACMAP, NAS5-97039). The authors benefited from numerous discussions with participants at the Methyl Bromine State of the Science Workshop, 1997. Their contributions are gratefully acknowledged. We would also like to thank Martyn Chipperfield for sharing his results prior to their publication.
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Issue or Number:D21
Record Number:CaltechAUTHORS:20181129-163705207
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Official Citation:Ko, M. K. W., N. D. Sze, C. Scott, J. M. Rodríguez, D. K. Weisenstein, and S. P. Sander (1998), Ozone depletion potential of CH3Br, J. Geophys. Res., 103(D21), 28187–28195, doi: 10.1029/98JD02537.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:91346
Deposited By: George Porter
Deposited On:30 Nov 2018 15:18
Last Modified:03 Oct 2019 20:34

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