Chemistry of atmospheric fine particles during the COVID-19 pandemic in a megacity of eastern China

Lei Liu, Jian Zhang, Rongguang Du, Xiaomi Teng, Rui Hu, Qi Yuan, Shanshan Tang, Chuanhua Ren, Xin Huang, Liang Xu, Yinxiao Zhang, Xiaoye Zhang, Congbo Song, Bowen Liu, Gongda Lu, Zongbo Shi, Weijun Li

Research output: Contribution to journalLetterpeer-review


Air pollution in megacities represents one of the greatest environmental challenges. Our observed results show that the dramatic NOx decrease (77%) led to significant O3 increases (a factor of 2) during the COVID-19 lockdown in megacity Hangzhou, China. Model simulations further demonstrate large increases of daytime OH and HO2 radicals and nighttime NO3 radical, which can promote the gas-phase reaction and nocturnal multiphase chemistry. Therefore, enhanced NO3 and SO42− formation was observed during the COVID-19 lockdown because of the enhanced oxidizing capacity. The PM2.5 decrease was only partially offset by enhanced aerosol formation with its reduction reaching 50%. In particular, NO3 decreased largely by 68%. PM2.5 chemical analysis reveals that vehicular emissions mainly contributed to PM2.5 under normal conditions in Hangzhou. Whereas, stationary sources dominated the residual PM2.5 during the COVID-19 lockdown. This study provides evidence that large reductions in vehicular emissions can effectively mitigate air pollution in megacities.

Original languageEnglish
Pages (from-to)1-10
Number of pages10
JournalGeophysical Research Letters
Issue number2
Publication statusPublished - 28 Jan 2021


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