A comprehensive analysis of the spatio-temporal variation of urban air pollution in China during 2014–2018

Air pollution has been a serious environmental problem in China that damages human health and causes climate change. While air pollution has been extensively investigated, few studies have provided systematic research on the recent space-time changes in air pollution components, including the AQI, CO, O3, NO2, SO2, PM10 and PM2.5, over all of China. Based on the national air quality ground observation database, with data from more than 300 cities from May 2014 to December 2018, this study provides a comprehensive analysis of the characteristics and temporal trends of air pollution over the 7 classified regions in China. Compared to 2014, there are significant decreases of air pollutants in 2018, which are 16% AQI, 25% CO, 20% NO2, 52% SO2, 20% PM10, and 28% PM2.5. The constant improvement of air quality is mainly associated with rigorous emission control acts in China, along with the changes of meteorology. In contrast, O3 maximum daily 8 h average (O3MDA8) continuously increased at an average rate of 4.6% per year during the study period. The air pollution components demonstrate distinct differences in spatial distribution, with high values of CO in North China and Northwest China, NO2 in North China and East China, PM10 in Northwest China, PM2.5 in North China and Central China, and SO2 in North China and Northeast China. Generally, air pollution is most serious in the North China Plain and in cities in central and western Xinjiang Province. Causes for these spatial distributions have been discussed from the perspective of emissions.