27 Jan 2022
27 Jan 2022
Status: this preprint is currently under review for the journal ACP.

The effect of COVID-19 restrictions on atmospheric new particle formation in Beijing

Chao Yan1,2,, Yicheng Shen3,, Dominik Stolzenburg2, Lubna Dada2,4, Ximeng Qi5, Simo Hakala2, Anu-Maija Sundström6, Yishuo Guo1, Antti Lipponen7, Tom Kokkonen5, Jenni Kontkanen2, Runlong Cai2,3, Jing Cai1,2, Tommy Chan2, Liangduo Chen5, Biwu Chu2, Chenjuan Deng3, Wei Du1,2, Xiaolong Fan1, Xu-Cheng He2, Juha Kangasluoma1,2, Joni Kujansuu1,2, Mona Kurppa2, Chang Li1, Yiran Li3, Zhuohui Lin1, Yiliang Liu8, Yuliang Liu5, Yiqun Lu8, Wei Nie5, Jouni Pulliainen6, Xiaohui Qiao3, Yonghong Wang1,2, Yifan Wen3, Ye Wu3, Gan Yang8, Lei Yao2, Rujing Yin3, Gen Zhang9, Shaojun Zhang3, Feixue Zheng1, Ying Zhou1, Antti Arola7, Johanna Tamminen6, Pauli Paasonen2, Yele Sun10, Lin Wang8, Neil M. Donahue11, Yongchun Liu1, Federico Bianchi2, Kaspar R. Daellenbach2,4, Douglas R. Worsnop2,12, Veli-Matti Kerminen2, Tuukka Petäjä2,5, Aijun Ding5, Jingkun Jiang3, and Markku Kulmala1,2,5 Chao Yan et al.
  • 1Aerosol and Haze Laboratory, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing, China
  • 2Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki, Finland
  • 3State Key Joint Laboratory of Environment Simulation and Pollution Control, State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex, School of Environment, Tsinghua University, Beijing, China
  • 4Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
  • 5Joint International research Laboratory of Atmospheric and Earth System Research (JirLATEST), School of Atmospheric Sciences, Nanjing University, Nanjing, China
  • 6Finnish Meteorological Institute, 00560 Helsinki, Finland
  • 7Finnish Meteorological Institute, 70211 Kuopio, Finland
  • 8Department of Environmental Science & Engineering, Fudan University, Shanghai, China
  • 9State Key Laboratory of Severe Weather & Key Laboratory of Atmospheric Chemistry of China Meteorological Administration (CMA), Chinese Academy of Meteorological Sciences, Beijing 100081, China
  • 10Institute of Atmospheric Physics, Chinese Academy of Science, Beijing, China
  • 11Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA, USA
  • 12Aerodyne Research Inc., Billerica, Massachusetts 01821, USA
  • These authors contributed equally to this work.

Abstract. During the COVID-19 lockdown, the dramatic reduction of anthropogenic emissions provided a unique opportunity to investigate the effects of reduced anthropogenic activity and primary emissions on atmospheric chemical processes and the consequent formation of secondary pollutants. Here, we utilize comprehensive observations to examine the response of atmospheric new particle formation (NPF) to the changes in the atmospheric chemical cocktail. We find that the main clustering process was unaffected by the drastically reduced traffic emissions, and the formation rate of 1.5 nm particles remained unaltered. However, particle survival probability was enhanced due to an increased particle growth rate (GR) during the lockdown period, explaining the enhanced NPF activity in earlier studies. For GR at 1.5–3 nm, sulfuric acid (SA) was the main contributor at high temperatures, whilst there were unaccounted contributing vapors at low temperatures. For GR at 3–7 nm and 7–15 nm, oxygenated organic molecules (OOMs) played a major role. Surprisingly, OOM composition and volatility were insensitive to the large change of atmospheric NOx concentration; instead the associated high particle growth rates and high OOM concentration during the lockdown period were mostly caused by the enhanced atmospheric oxidative capacity. Overall, our findings suggest a limited role of traffic emissions in NPF.

Chao Yan et al.

Status: open (extended)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-1079', Anonymous Referee #1, 18 Feb 2022 reply

Chao Yan et al.


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Short summary
Atmospheric new particle formation (NPF) is a dominant source of atmospheric ultrafine particles. In the urban environment, traffic emission is a major source of primary pollutants, but its contribution to NPF remains under debate. During the COVID-19 lockdown, traffic emissions were significantly reduced, providing a unique chance to examine its relevance to NPF. Based on our comprehensive measurements, we demonstrate an insignificant role of traffic emission in NPF.