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Enhanced formation of secondary organic aerosol from photochemical oxidation during the COVID-19 lockdown in a background site in Northwest China
Zhong, Haobin1,2,3; Huang, Ru-Jin1,2,4; Chang, Yunhua5,6; Duan, Jing1,2; Lin, Chunshui1,2; Chen, Yang7
2021-07-15
摘要The COVID-19 pandemic has drastically affected the economic and social activities, leading to large reductions in anthropogenic emissions on a global scale. Despite the reduction of primary emissions during the lockdown period, heavy haze pollution was observed unexpectedly in megacities in North and East China. In this study, we conducted online measurements of organic aerosol in a background site before and during the lockdown in Guanzhong basin, Northwest China. The oxygenated organic aerosol (OOA) increased from 24% of total OA (3.2 +/- 1.6 mu g m(-3)) before lockdown to 54% of total OA (4.5 +/- 1.3 mu g m(-3)) during lockdown, likely due to substantial decrease of NOx emissions during lockdown which resulted in large increase of O-3 and thus atmospheric oxidizing capacity. OOA showed higher mass concentrations and fractional contributions during lockdown than before lockdown, and increased with the increase of Ox in both periods. In comparison, aqueous secondary organic aerosol (aqSOA) showed high mass concentrations and fractional contributions in both polluted periods before and during lockdown with the increase of aerosol liquid water content (ALWC). The increase of aqSOA under high ALWC conditions is very likely the reason of pollution events during lockdown. Combined with trajectory analysis, the absence of Guanzhong cluster in polluted period during lockdown may play a key role in the OA variations between two polluted periods. In addition, when comparing the clusters from the same transmission directions between before lockdown and during lockdown, the OA fractions showed similar variations during lockdown in all clusters, suggesting the OA variations are widespread in northwest China. (C) 2021 Published by Elsevier B.V.
关键词COVID-19 OOA aqSOA Lockdown Secondary formation
DOI10.1016/j.scitotenv.2021.144947
发表期刊SCIENCE OF THE TOTAL ENVIRONMENT
ISSN0048-9697
卷号778页码:7
通讯作者Huang, Ru-Jin(rujin.huang@ieecas.cn)
收录类别SCI
WOS记录号WOS:000655719100011
语种英语