Analysis of factors influencing air quality in different periods during COVID- 19: A case study of Tangshan, China

Abstract

Since the outbreak of COVID-19, China has experienced the Level I, Level II, and Level III responses to the epidemic, with different measures have an impact on air quality in difference periods. This study aimed to analyze the main factors influencing air quality in three different periods during COVID-19 in Tangshan: the COVID-19 period, the Level I response period, and the Spring Festival period. Here, we used comparative analysis and difference-in-differences (DID) method to explore differences in air quality. During COVID-19, the air quality index (AQI) and the concentrations of six conventional air pollutants (PM2.5, PM10, SO2, NO2, CO, and O3-8h) decreased significantly compared to 2017–2019. Air quality improved may be the result of industry closures not related to livelihoods during COVID-19 in 2020. For the Level I response period, multiple linear regression (MLR) models were used to quantify the impact of COVID-19 control measures on AQI, and it was shown that the measures reduced the average AQI by 29.07%, 31.43%, and 20.04% in February, March, and April 2020, respectively. During the Spring Festival, the concentrations of the above-mentioned six pollutants were significantly higher than those in 2019 and 2021 as there were two heavy pollution episodes in 2020, and the possible pollutant sources were local emissions and short-distance transportation. As for the further improvement of air quality, it is necessary to take strict measures to prevent and control air pollution while paying attention to meteorological factors.