Preprints
https://doi.org/10.5194/acp-2021-928
https://doi.org/10.5194/acp-2021-928

  06 Dec 2021

06 Dec 2021

Review status: this preprint is currently under review for the journal ACP.

Amplified role of potential HONO sources in O3 formation in North China Plain during autumn haze aggravating processes

Jingwei Zhang1,, Chaofan Lian2,3,, Weigang Wang2,3,, Maofa Ge2,3,6, Yitian Guo1,3, Haiyan Ran1,3, Yusheng Zhang4, Feixue Zheng4, Xiaolong Fan4, Chao Yan5, Kaspar R. Daellenbach5, Yongchun Liu4, Markku Kulmala4,5, and Junling An1,3,6 Jingwei Zhang et al.
  • 1State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC), Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences, Beijing 100029, China
  • 2State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
  • 3University of the Chinese Academy of Sciences, Beijing 100049, China
  • 4Aerosol and Haze Laboratory, Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing, 100029, China
  • 5Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, P.O. Box 64, 00014 University of Helsinki, Helsinki, Finland
  • 6Center for Excellence in Urban Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
  • These authors contributed equally to this work.

Abstract. Co-occurrences of high concentrations of PM2.5 and ozone (O3) have been frequently observed in haze aggravating processes in the North China Plain (NCP) over the past few years, and higher O3 concentrations during hazy days were supposed to be related to nitrous acid (HONO), but the key sources of HONO enhancing O3 during haze aggravating processes remain unclear, and will be explored in this study by using the WRF-Chem model, which is improved to include ground-based (traffic, soil, and indoor emissions, and the NO2 heterogeneous reaction on ground surface (Hetground)) and aerosol-related (the NO2 heterogeneous reaction on aerosol surfaces (Hetaerosol) and nitrate photolysis (Photnitrate)) potential HONO sources. The results indicate that ground-based HONO sources producing HONO enhancements showed a rapid decrease with height, while the NO+OH reaction and aerosol-related HONO sources decreased slowly with height. Photnitrate contributions to HONO concentrations enhanced with aggravated pollution levels, the enhanced HONO due to Photnitrate in hazy days was about one order of magnitude larger than in clean days and Photnitrate dominated HONO sources (~30–70 % when the ratio of the photolysis frequency of nitrate (Jnitrate) to gas nitric acid (JHNO3) equals 30) at higher layers (> 800 m). Compared with that in clean days, the Photnitrate contribution to the enhanced daily maximum 8-h averaged O3 was increased by over one magnitude during the haze aggravating process. Photnitrate contributed only ~5 % of the surface HONO in daytime with a Jnitrate/JHNO3 ratio of 30 but contributed ~30–50 % of the enhanced O3 near the surface in NCP in hazy days. Surface O3 was dominated by volatile organic compounds-sensitive chemistry, while O3 at higher altitude (> 800 m) was dominated by NOx-sensitive chemistry. Photnitrate had a limited impact on nitrate concentrations (< 15 %) even with a Jnitrate/JHNO3 ratio of 120. The above results suggest that more field studies of Jnitrate in the atmosphere are still needed.

Jingwei Zhang et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-928', Anonymous Referee #3, 15 Dec 2021
  • RC2: 'Comment on acp-2021-928', Anonymous Referee #2, 27 Dec 2021

Jingwei Zhang et al.

Jingwei Zhang et al.

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Short summary
This study added six potential HONO sources into WRF-Chem model, evaluated their impacts on HONO and O3 concentrations, including surface and vertical. The simulations deepen our cognition on atmospheric HONO sources, especially for nitrate photolysis. This study also reaonably explain the HONO difference in O3 formation during clean and hazy days, and revealed key potential HONO sources to O3 enhancements in haze aggravating processes with a co-occurrence of high PM2.5 and O3 concentrations.
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