Characterization of summertime single aerosol particles in Chengdu (China): Interannual evolution and impact of COVID-19 lockdown

Junke Zhang; Chunying Chen; Yunfei Su; Wenkai Guo; Xinyi Fu; Yuhan Long; Xiaoxue Peng; Wei Zhang; Xiaojuan Huang; Gehui Wang

doi:10.1016/j.scitotenv.2023.167765

Characterization of summertime single aerosol particles in Chengdu (China): Interannual evolution and impact of COVID-19 lockdown

Sci Total Environ. 2024 Jan 10:907:167765. doi: 10.1016/j.scitotenv.2023.167765. Epub 2023 Oct 11.

Authors

Junke Zhang¹, Chunying Chen², Yunfei Su², Wenkai Guo², Xinyi Fu², Yuhan Long², Xiaoxue Peng², Wei Zhang³, Xiaojuan Huang⁴, Gehui Wang⁵

Affiliations

¹ Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu 611756, China. Electronic address: zhangjunke@home.swjtu.edu.cn.
² Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu 611756, China.
³ Sichuan Ecological Environment Monitoring Station, Chengdu 610091, China.
⁴ Department of Environmental Science & Engineering, Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Fudan University, Shanghai 200438, China.
⁵ Key Lab of Geographic Information Science of the Ministry of Education, School of Geographic Sciences, East China Normal University, Shanghai 200241, China.

PMID: 37832658
DOI: 10.1016/j.scitotenv.2023.167765

Abstract

To investigate the interannual evolution of air pollution in summer and the impact of the COVID-19 lockdown on local pollution in Chengdu, China, single aerosol particles were continuously measured in three summer periods: the regular period in 2020 (RP2020); the regular period in 2022 (RP2022); and the lockdown period in 2022 (LP2022). It was found that, from RP2020 to RP2022, the mass concentrations of PM_2.5, PM₁₀, SO₂ and NO₂ decreased by 25.6 %, 24.7 %, 28.8 % and 38.5 %, respectively, while the concentration of O₃ increased by 11.0 %. Affected by regional transport, there was no significant decrease in the concentrations of various pollutants during LP2022. All single aerosol particles could be classified into seven categories: vehicle emissions (VE), dust, biomass burning (BB), coal combustion (CC), K mixed with sulfate (KSO₄), K mixed with nitrate (KNO₃) and K mixed with sulfate and nitrate (KSN) particles. From RP2020 to RP2022, the contributions of BB and CC particles decreased by 12.1 % and 0.9 %, respectively, while VE and dust particles increased by 3.6 % and 2.5 %, respectively; and compared to RP2022, the contributions of VE, dust and CC particles in LP2022 decreased by 22.2 %, 11.0 % and 12.7 %, respectively. The high PM_2.5 pollution events in RP2020 and RP2022 were mainly caused by combustion sources (BB and CC, 51.6 %) and VE (38.3 %) particles, respectively, while the pollution event in LP2022 was contributed by BB (27.0 %) and secondary inorganic (KSO₄, KNO₃ and KSN, 60.2 %) particles. The formation mechanisms of different pollution events were further validated by WRF-Chem results. Although the potential source areas of particles showed a shrinking trend from RP2020 to RP2022, regional transport still caused high PM_2.5 pollution events during LP2022. Photochemical processes dominated the formation of KSO₄ particles, while the KNO₃ and KSN particles were mainly generated by liquid-phase reactions, and this effect increased year by year.

Keywords: Chemical composition; Formation mechanism; Regional transport; Single aerosol particles; WRF-Chem.

MeSH terms

Air Pollutants* / analysis
Air Pollution* / analysis
COVID-19* / epidemiology
China
Coal
Communicable Disease Control
Dust / analysis
Environmental Monitoring / methods
Humans
Nitrates / analysis
Particulate Matter / analysis
Respiratory Aerosols and Droplets
Seasons
Sulfates / analysis
Vehicle Emissions

Substances

Air Pollutants
Particulate Matter
Nitrates
Dust
Vehicle Emissions
Sulfates
Coal