Spatial and seasonal variations of gaseous and particulate matter pollutants in 31 provincial capital cities, China

In order to know air pollution situation and their health, environmental, and climate effects, the air quality data with high temporal and spatial resolutions are essential. The spatial and seasonal variations of six criteria pollutants were investigated in 31 provincial capital cities between April 2014 and March 2015 using hourly mean air quality monitoring data, and the cities were classified by cluster analysis based on annual variations of air pollutants. The annual mean concentrations of PM2.5 (particulate matter with aerodynamic diameter less than 2.5 μm) and PM10 (particulate matter with aerodynamic diameter less than 10 μm) were high for all cities, which exceeded Chinese Ambient Air Quality Standards (CAAQS) Grade I standards. Only Fuzhou, Haikou, Kunming, and Lasa met Grade II standards for PM2.5 and PM10. Additionally, elevated SO2 concentration was observed in northern cities, especially in winter. However, the seasonal variation of O3 was opposite to other pollutants with the lowest concentrations in the winter and the highest in the summer. Winter domestic heating has significant impact on urban air quality, especially SO2 and PM10.