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

Research output: Contribution to journalArticlepeer-review

Authors

  • Tuan Vu
  • James Lee
  • Freya A. Squires
  • Lisa K. Whalley
  • Eloise Slater
  • Robert Woodward-Massey
  • Chunxiang Ye
  • Dwayne E. Heard
  • Shengrui Tong
  • Siqi Hou
  • Yele Sun
  • Jingsha Xu
  • Lianfang Wei
  • Pingqing Fu

External organisations

  • King Abdulaziz University

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.

Details

Original languageEnglish
Pages (from-to)223-238
JournalFaraday Discussions
Volume226
Early online date21 Sep 2020
Publication statusPublished - Mar 2021

ASJC Scopus subject areas