Measurement report of the change of PM2.5 composition during the COVID-19 lockdown in urban Xi'an: Enhanced secondary formation and oxidation.

The Science of the Total Environment
Jing DuanColin O'Dowd

Abstract

Enhanced secondary aerosol formation was observed during the COVID-19 lockdown in Xi'an, especially for polluted episodes. More oxidized‑oxygenated organic aerosol (MO-OOA) and sulfate showed the dominant enhancements, especially in large particle-mode. Meanwhile, relative humidity (RH) showed a positive promotion on the formation of sulfate and MO-OOA during the lockdown, but had no obvious correlation with less oxidized‑oxygenated organic aerosol (LO-OOA) or nitrate. Organosulfurs (OS) displayed a higher contribution (~58%) than inorganic sulfate to total sulfate enhancement in the polluted episode during the lockdown. Although the total nitrate (TN) decreased during the lockdown ascribing to a larger reduction of inorganic nitrate, organic nitrate (ON) showed an obvious increase from pre-lockdown (0.5 ± 0.6 μg m-3 and 1 ± 2% of TN) to lockdown (5.3 ± 3.1 μg m-3 and 17 ± 9% of TN) in the polluted case (P < 0.05). In addition, RH also displayed a positive promotion on the formation of ON and OS, and the increases of both OS and ON were much efficient in the nighttime than in the daytime. These results suggest that higher RH and stagnant meteorology might facilitate the sulfate and MO-OOA enhancement, especially in the nighttim...Continue Reading

References

Jan 25, 2020·The New England Journal of Medicine·Na ZhuUNKNOWN China Novel Coronavirus Investigating and Research Team
Feb 9, 2020·International Journal of Environmental Research and Public Health·Jing WuWenjie Sun
Apr 18, 2020·The Science of the Total Environment·Aurelio TobíasXavier Querol
Apr 27, 2020·The Science of the Total Environment·Hongchao QiZhijie Zhang
May 1, 2020·The Science of the Total Environment·Samsuri AbdullahZamzam Tuah Ahmad Ramly
May 16, 2020·The Science of the Total Environment·Rui Bao, Acheng Zhang
Aug 25, 2020·Geophysical Research Letters·Xiaoqin Shi, Guy P Brasseur
Aug 25, 2020·Geophysical Research Letters·Yunhua ChangMoritz F Lehmann

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