Variability of PM2.5 and O3 concentrations and their driving forces over Chinese megacities during 2018-2020.

Recently, air pollution especially fine particulate matters (PM 2.5) and ozone (O 3) has become a severe issue in China. In this study, we first characterized the temporal trends of PM 2.5 and O 3 for Beijing, Guangzhou, Shanghai, and Wuhan respectively during 2018-2020. The annual mean PM 2.5 has decreased by 7.82%-33.92%, while O 3 concentration showed insignificant variations by -6.77%-4.65% during 2018-2020. The generalized additive models (GAMs) were implemented to quantify the contribution of individual meteorological factors and their gas precursors on PM 2.5 and O 3. On a short-term perspective, GAMs modeling shows that the daily variability of PM 2.5 concentration is largely related to the variation of precursor gases (R = 0.67-0.90), while meteorological conditions mainly affect the daily variability of O 3 concentration (R = 0.65-0.80) during 2018-2020. The impact of COVID-19 lockdown on PM 2.5 and O 3 concentrations were also quantified by using GAMs. During the 2020 lockdown, PM 2.5 decreased significantly for these megacities, yet the ozone concentration showed an increasing trend compared to 2019. The GAMs analysis indicated that the contribution of precursor gases to PM 2.5 and O 3 changes is 3-8 times higher than that of meteorological factors. In general, GAMs modeling on air quality is helpful to the understanding and control of PM 2.5 and O 3 pollution in China. [Display omitted] [ABSTRACT FROM AUTHOR]