Abstract
To study the air quality changes during the Corona Virus Disease 2019 (COVID-19) lockdown in Changchun, we analyzed the changes in pollution of six major pollutants (PM2.5, PM10, SO2, NO2, O3, CO) and correlated them with meteorological parameters, using meteorological data and pollutants concentration data. Regional transport pathways and potential source areas of pollutants were analyzed using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model and Potential Source Contribution Function (PSCF). The results showed that the concentrations of PM2.5, PM10, SO2, NO2, CO were 30.5%–53.8% lower in the Level I period and 49.4%–65.0% lower in the Level II period than in the pre-lockdown period, respectively. Conversely, O3 increased 59.6% and 58.1% during Level I and Level II, respectively, compared to the pre-lockdown period. During the 55-day lockdown, daily average concentrations of each pollutant were lower than in previous years on 36-55 days, while O3 was higher on 35 days. The pollutants that decreased in concentration during the lockdown also showed an increase during the Level III period (up to 188.5%). The maximum daily growth rate of PM2.5 during the lockdown period in 2020 was 16.0%, which was higher than this value in the same period of previous years (21.8%, 21.4%, 17.4%). This shows that the change trend of pollutants during the lockdown period is smoother than in previous years. Temperature and O3 were positively correlated before the lockdown and during Level I and weakly negatively correlated during Level II and Level III. Despite the prevalence of northwest winds in winter, a high percentage of trajectories from other directions (up to 36.8%) was observed during the lockdown. Simultaneously, the lockdown reduced the potential source area for PM2.5 (WPSCF ≥ 0.000007), but rebounded after the lockdown was lifted. In conclusion, the lockdown only temporarily reduced the air pollution in Changchun.
Highlights
Publisher: Taiwan Association for Aerosol Research ISSN: 1680-8584 print ISSN: 2071-1409 onlineCopyright: The Author(s)
There are ten automatic air monitoring stations in Changchun, as shown in Fig. 1: Daishan Park (DP), High-Tech Zone Management Committee (HZMC), Economic Development Zone Environment Sanitary Administration (EESA), Jingyue Park (JYP), Bus Factory Hospital (BFH), Labour Park (LP), Garden Management Office (GMO), Institute of Posts and Telecommunications (IPT), Food Products Factory (FPF), and one clean control station named Shuaiwanzi (SWZ), which is located in the Shuangyang district of Changchun
During the level I period, PM2.5 increased by 10.7% and 63.8% respectively compared with the same period in 2017 and 2018, possibly because the lockdown began at the beginning of the Lunar New year in 2020, and the lockdown made people stay at home and travel was greatly reduced
Summary
Publisher: Taiwan Association for Aerosol Research ISSN: 1680-8584 print ISSN: 2071-1409 onlineCopyright: The Author(s). In the wake of the pandemic, China has put in place strict and effective emergency measures to deal with the pandemic, the core of which is the “lockdown”, and as a result, the number of new confirmed cases has fallen dramatically, and many people have been prevented from becoming infected (Shen et al, 2020; Tian et al, 2020). We know that human activities such as industry, traffic and living are the primary sources of air pollution emissions, especially in winter (Li et al, 2017; Wen et al, 2020). The air quality during COVID-19 in China was better than in previous years. Satellite images released by the National Aeronautics and Space Administration (NASA) of the United States of America point to a significant reduction in China's NO2
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