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- Title
Enhancement of nanoparticle formation and growth during the COVID-19 lockdown period in urban Beijing.
- Authors
Xiaojing Shen; Junying Sun; Fangqun Yu; Xiaoye Zhang; Junting Zhong; Yangmei Zhang; Xinyao Hu; Can Xia; Sinan Zhang
- Abstract
Influenced by the spread of the global 2019 novel coronavirus (COVID-19) pandemic, primary emissions of particles and precursors associated with anthropogenic activities decreased significantly in China during the Chinese New Year of 2020 and the lockdown period (January 24-February 16, 2020), as indicated by approximately 50 % reduction of NOx emission nation-wide based on the open literature. Two-month measurements of the number size distribution of neutral particles and charged ions showed that during the lockdown (LCD) period, the number concentration of particles smaller than 100 nm decreased by approximately 40 % compared to the pre-LCD period in January. However, the accumulation mode particles increased by approximately 20 % as several polluted episodes contributed to secondary aerosol formation. In this study, new particle formation (NPF) events were found to be enhanced in the nucleation and growth processes during the LCD period, as indicated by higher formation (J2) and growth rate (GR), even as NPF occurrence frequency slightly decreased. The condensing vapors controlling the nucleation and growth process, sulfuric acid, and oxidation product of volatile organic compounds were estimated based on available information. The proxy values showed that sulfuric acid and organic oxidized vapors increased during the LCD period by approximately 35 % and 133 % on NPF days, respectively. Higher J2 and GR during the LCD period were favored by the increased concentration level of condensing vapors and decreased condensation sink. Several heavy haze episodes have been reported by other studies during the LCD period; however, the increase in nanoparticle number concentration should also be considered. Some typical NPF events produced a high number concentration of nanoparticles that intensified in the following days to create severe aerosol pollution. Our study confirms a significant enhancement of the nucleation and growth process of nanoparticles during the COVID-19 LCD in Beijing and highlights the necessity of controlling nanoparticles in current and future air quality management.
- Subjects
BEIJING (China); CHINA; SARS-CoV-2; AIR quality management; DISCONTINUOUS precipitation; STAY-at-home orders; COVID-19
- Publication
Atmospheric Chemistry & Physics Discussions, 2020, p1
- ISSN
1680-7367
- Publication type
Article
- DOI
10.5194/acp-2020-1064