In:
Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 18, No. 18 ( 2018-09-21), p. 13481-13493
Abstract:
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 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.
Type of Medium:
Online Resource
ISSN:
1680-7324
DOI:
10.5194/acp-18-13481-2018
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2018
detail.hit.zdb_id:
2092549-9
detail.hit.zdb_id:
2069847-1
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