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Puzzling Haze Events in China During the Coronavirus (COVID‐19) Shutdown
Author(s) -
Chang Yunhua,
Huang RuJin,
Ge Xinlei,
Huang Xiangpeng,
Hu Jianlin,
Duan Yusen,
Zou Zhong,
Liu Xuejun,
Lehmann Moritz F.
Publication year - 2020
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2020gl088533
Subject(s) - aerosol , haze , covid-19 , shutdown , china , atmospheric sciences , environmental science , particle (ecology) , nitrate , outbreak , meteorology , environmental chemistry , chemistry , geography , physics , virology , nuclear chemistry , medicine , geology , oceanography , disease , archaeology , pathology , infectious disease (medical specialty) , organic chemistry
It is a puzzle as to why more severe haze formed during the New Year Holiday in 2020 (NYH‐20), when China was in an unprecedented state of shutdown to contain the coronavirus (COVID‐19) outbreak, than in 2019 (NYH‐19). We performed a comprehensive measurement and modeling analysis of the aerosol chemistry and physics at multiple sites in China (mainly in Shanghai) before, during, and after NYH‐19 and NYH‐20. Much higher secondary aerosol fraction in PM 2.5 were observed during NYH‐20 (73%) than during NYH‐19 (59%). During NYH‐20, PM 2.5 levels correlated significantly with the oxidation ratio of nitrogen ( r 2 = 0.77, p < 0.01), and aged particles from northern China were found to impede atmospheric new particle formation and growth in Shanghai. A markedly enhanced efficiency of nitrate aerosol formation was observed along the transport pathways during NYH‐20, despite the overall low atmospheric NO 2 levels.