Temporal Variations in the Air Quality Index and the Impact of the COVID-19 Event on Air Quality in Western China

Abstract

This study investigated the AQI (air quality index) and atmospheric pollutants including PM 2.5 , PM 10 , CO, SO 2 , NO 2 and O 3 in Chongqing, Luzhou and Chengdu from 2017 to 2019. In addition, the impacts of the COVID-19 event on the air quality in the three cities in 2020 were compared and discussed. For the combined AQIs for the three cities, in spring, the daily AQIs ranged between 25 and 182 and averaged 72.1. In summer, the daily AQIs ranged between 24 and 206 and averaged 77.5. In autumn, the daily AQIs ranged between 22 and 170 and averaged 61.1, and in winter, the daily AQIs ranged between 28 and 375 and averaged 99.6. The distributions of the six AQI classes in spring were 3%, 94%, 3%, 0%, 0%, and 0%; in summer, they were 11%, 74%, 15%, 0%, 0% and 0%; in autumn, they were 29%, 70%, 1%, 0%, 0%, and 0%, and in winter, they were 1%, 52%, 44%, 3%, 0%, and 0%, respectively. The average AQIs, in order, were Chengdu (85.4) > Chongqing (73.8) > Luzhou (73.2). Both the highest AQIs and PM 2.5 (as the major indicatory air pollutant) occurred mainly in the low temperature season (January, December, and February), while O 3 was the main air pollutant in June and August when the weather was hot. In February 2020, during the epidemic prevention and control actions taken in response to COVID-19 for the three cities, the combined AQIs for the top five days with the highest

Effects of COVID-19 Emergency Response Levels on Air Quality in the Guangdong-Hong Kong-Macao Greater Bay Area, China

“…The values of AQI, NO2, PM2.5, PM10, and CO from 1-19 January 2020 declined 19.4%, 17.0%, 27.5%, 15.8%, and 25.7%, respectively, compared with the same time periods in 2016-2019. The trends are consistent with the results in other regions in China(Chen et al, 2020;Xu et al, 2020;Filonchyk et al, 2020;Zhang et al, 2020a;Zhang et al, 2020b;Wan et al, 2020;Bao and Zhang, 2020). Different time periods of analysis contribute to the differences of our results from those of other studies.…”

“…the COVID-19 pandemic (Chen et al, 2020;Xu et al, 2020;Filonchyk et al, 2020;Zhang et al, 2020a;Zhang et al, 2020b;Wan et al, 2020;Bao and Zhang, 2020). Similar reductions have been observed in other regions of the world.…”

Changes in ambient air quality and atmospheric composition and reactivity in the South East of the UK as a result of the COVID-19 lockdown

“…S4, the time lag between the O 3 and PM 2.5 trendlines and the presence of isolated peaks in O 3 , suggest there were significant contributions to local O 3 concentrations derived from changes in UK emissions. Importantly, these findings are not limited to the UK, with other studies from a range of countries also showing that tropospheric O 3 concentrations increased owing to changes in emissions profiles during lockdown, including in Spain ( Tobías et al, 2020 ), Brazil ( Siciliano et al, 2020 ), Italy, ( Sicard et al, 2020 ), China ( Chen et al, 2020 ; Le et al, 2020 ; Zhang et al, 2020 ), Korea ( Ju et al, 2020 ) and India ( Sharma et al, 2020 ).…”

Air pollution episodes during the COVID-19 outbreak in the Beijing–Tianjin–Hebei region of China: An insight into the transport pathways and source distribution

“…The O 3 concentration decreased by 16.4% and 33.9% in Beijing and Tianjin, respectively, but increased by 16.6% in Shijiazhuang. Related studies also found that the average O 3 concentration increased during the COVID-19 outbreak compared to 2017–2019 in Hubei Province ( Xu et al., 2020 ), western China ( Zhang et al., 2020a ), and 366 urban areas across mainland China ( Chen et al., 2020b ). An increased O 3 concentration is believed to be mainly due to the reduced NO 2 that hinders the reaction between NO and O 3 , thus increasing the atmospheric oxidizing capacity ( Le et al., 2020 ; Nichol et al., 2020 ; Xu et al., 2020 ).…”