Air quality characteristics during 2016-2020 in Wuhan, China.

Implementation of a clean air policy in China has high national importance. Here, we analyzed tempo-spatial characteristics of the concentrations of PM2.5 (PM2.5_C), PM10 (PM10_C), SO2 (SO2 _C), NO2 (NO2 _C), CO (CO _C), and maximum 8-h average O3 (O3_8h_C), monitored at 22 stations throughout the mega-city of Wuhan from January 2016 to December 2020, and their correlations with the meteorological and socio-economic factors. PM2.5_C, PM10_C, SO2 _C, NO2 _C, and CO _C showed similar monthly and seasonal trends, with minimum value in summer and maximum value in winter. However, O3_8h_C showed an opposite monthly and seasonal change pattern. In 2020, compared to the other years, the annual average PM2.5_C, PM10_C, SO2 _C, NO2 _C, and CO _C were lower. PM2.5_C and PM10_C were higher in urban and industrial sites and lower in the control site. The SO2_C was higher in industrial sites. The NO2_C was lower, and O3_8h_C was higher in suburban sites, while CO showed no spatial differences in their concentrations. PM2.5 _C, PM10 _C, SO2 _C, NO2 _C, and CO _C had positive correlations with each other, while O3_8h_C showed more complex correlations with the other pollutants. PM2.5_C, PM10_C, SO2 _C, and CO _C presented a significantly negative association with temperature and precipitation, while O3 was significantly positively associated with temperature and negatively associated with relative air humidity. There was no significant correlation between air pollutants and wind speed. Gross domestic product, population, number of automobiles, and energy consumption play an important role in the dynamics of air quality concentrations. These all provided important information for the decision and policy-makers to effectively control the air pollution in Wuhan.