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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2018-236
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
07 Mar 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
Observations of organic and inorganic chlorinated compounds and their contribution to chlorine radical concentrations in an urban environment in Northern Europe during the wintertime
Michael Priestley1, Michael le Breton1,a, Thomas J. Bannan1, Stephen D. Worrall1,b, Asan Bacak1, Andrew R. D. Smedley1,c, Ernesto Reyes-Villegas1, Archit Mehra1, James Allan1,2, Ann R. Webb1, Dudley E. Shallcross3, Hugh Coe1, and Carl J. Percival1,d 1Centre for Atmospheric Science, School of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK
2National Centre for Atmospheric Science, University of Manchester, Manchester, M13 9PL, UK
3School of Chemistry, The University of Bristol, Cantock’s Close BS8 1TS, UK
anow at: Department of Chemistry and Molecular Biology, University of Gothenburg, 412 96 Göteborg, Sweden
bnow at: School of Materials, University of Manchester, Manchester, M13 9PL, UK
cnow at: School of Mathematics, University of Manchester, Manchester, M13 9PL, UK
dnow at: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109
Abstract. A number of inorganic (nitryl chloride, ClNO2; chlorine, Cl2; and hypochlorous acid, HOCl) and chlorinated, oxygenated volatile organic compounds (ClOVOCs) have been measured in Manchester, UK during October and November 2014 using time of flight chemical ionisation mass spectrometry (ToF-CIMS) with the I reagent ion. ClOVOCs appear to be mostly photochemical in origin although direct emission from vehicles is also suggested. Peak concentrations of ClNO2, Cl2 and HOCl reach 506, 16 and 9 ppt respectively. The concentrations of ClNO2 are comparable to measurements made in London, but measurements of ClOVOCs, Cl2 and HOCl by this method are the first reported in the UK. Maximum HOCl and Cl2 concentrations are found during the day and ClNO2 concentrations remain elevated into the afternoon if photolysis rates are low. Cl2 exhibits a strong dependency on sunlight further adding to the growing body of evidence that it is formed in the atmosphere, however night time emission is also observed. The contribution of ClNO2, Cl2 and ClOVOCs to the chlorine radical budget suggests that Cl2 can be a greater source of Cl than ClNO2, contributing 57 % of the Cl radicals produced on a sunny day. In contrast, on a cloudy day, this drops to 17 % as both the formation of Cl2 in the atmosphere and its decomposition by sunlight are inhibited. This results in ClNO2 making up the dominant fraction (68 %) on cloudy days as its concentrations are still high. As most ClOVOCs appear to require sunlight to form, they exhibit a similar dependence to Cl2 on sunlight, contributing between 15 %–24 % of the Cl radical budget observed here.
Citation: Priestley, M., le Breton, M., Bannan, T. J., Worrall, S. D., Bacak, A., Smedley, A. R. D., Reyes-Villegas, E., Mehra, A., Allan, J., Webb, A. R., Shallcross, D. E., Coe, H., and Percival, C. J.: Observations of organic and inorganic chlorinated compounds and their contribution to chlorine radical concentrations in an urban environment in Northern Europe during the wintertime, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2018-236, in review, 2018.
Michael Priestley et al.
Michael Priestley et al.
Michael Priestley et al.

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