Volume 226, 2021

Insights into air pollution chemistry and sulphate formation from nitrous acid (HONO) measurements during haze events in Beijing

Abstract

Wintertime urban air pollution in many global megacities is characterised by episodic rapid increase in particulate matter concentrations associated with elevated relative humidity – so-called haze episodes, which have become characteristic of cities such as Beijing. Atmospheric chemistry within haze combines gas- and condensed-phase chemical processes, leading to the growth in secondary species such as sulphate aerosols. Here, we integrate observations of reactive gas phase species (HONO, OH, NOx) and time-resolved aerosol composition, to explore observational constraints on the mechanisms responsible for sulphate growth during the onset of haze events. We show that HONO abundance is dominated by established fast gas-phase photochemistry, but the consideration of the additional formation potentially associated with condensed-phase oxidation of S species by aqueous NO2 leading to NO2 production and hence HONO release, improves agreement between observed and calculated gas-phase HONO levels. This conclusion is highly dependent upon aerosol pH, ionic strength and particularly the parameterisation employed for S(IV) oxidation kinetics, for which an upper limit is derived.

Graphical abstract: Insights into air pollution chemistry and sulphate formation from nitrous acid (HONO) measurements during haze events in Beijing

Associated articles

Supplementary files

Article information

Article type
Paper
Submitted
13 Aug 2020
Accepted
21 Sep 2020
First published
21 Sep 2020
This article is Open Access
Creative Commons BY license

Faraday Discuss., 2021,226, 223-238

Insights into air pollution chemistry and sulphate formation from nitrous acid (HONO) measurements during haze events in Beijing

W. J. Bloss, L. Kramer, L. R. Crilley, T. Vu, R. M. Harrison, Z. Shi, J. D. Lee, F. A. Squires, L. K. Whalley, E. Slater, R. Woodward-Massey, C. Ye, D. E. Heard, S. Tong, S. Hou, Y. Sun, J. Xu, L. Wei and P. Fu, Faraday Discuss., 2021, 226, 223 DOI: 10.1039/D0FD00100G

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