Observations of organic and inorganic chlorinated compounds and their contribution to chlorine radical concentrations in an urban environment in northern Europe during the wintertime


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 Ig 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 9ppt 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 shortwave radiation, further adding to the growing body of evidence that it is a product of secondary chemistry. 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 74% of the Cl radicals produced on a high radiant-flux day. In contrast, on a low radiant-flux day, this drops to 14%, as both Cl2 production and loss pathways are inhibited by reduced photolysis rates. This results in ClNO2 making up the dominant fraction (83%) on low radiant-flux days, as its concentrations are still high. As most ClOVOCs appear to be formed photochemically, they exhibit a similar dependence on photolysis, contributing 3% of the Cl radical budget observed here.

Publication DOI: https://doi.org/10.5194/acp-18-13481-2018
Divisions: College of Engineering & Physical Sciences > School of Infrastructure and Sustainable Engineering > Chemical Engineering & Applied Chemistry
College of Engineering & Physical Sciences
Additional Information: © Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License.
Uncontrolled Keywords: Atmospheric Science
Publication ISSN: 1680-7324
Full Text Link:
Related URLs: http://www.scop ... tnerID=8YFLogxK (Scopus URL)
https://www.atm ... /18/13481/2018/ (Publisher URL)
PURE Output Type: Article
Published Date: 2018-09-21
Accepted Date: 2018-08-28
Authors: Priestley, Michael
Le Breton, Michael
Bannan, Thomas J.
Worrall, Stephen D. (ORCID Profile 0000-0003-1969-3671)
Bacak, Asan
Smedley, Andrew R.D.
Reyes-Villegas, Ernesto
Mehra, Archit
Allan, James
Webb, Ann R.
Shallcross, Dudley E.
Coe, Hugh
Percival, Carl J.



Version: Published Version

License: Creative Commons Attribution

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