Spatial and temporal variations of the concentrations of PM10, PM2.5 and PM1 in China

Concentrations of PM10, PM2.5 and PM1 were monitored at 24 CAWNET (China Atmosphere Watch Network) stations from 2006 to 2014. The highest particulate matter (PM) concentrations were observed at the stations of Xian, Zhengzhou and Gucheng, on the Guanzhong Plain and the Huabei Plain (HBP). The second highest PM concentrations were observed in northeast China, followed by southern China. According to the latest air quality standards of China, 14 stations reached the PM10 standard, and only 7 stations, mainly rural and remote stations, reached the PM2.5 standard. The ratios of PM2.5 to PM10 showed a clear increasing trend from northern to southern China, because of the substantial contribution of coarse mineral aerosol in northern China. The ratios of PM1 to PM2.5 were higher than 80% at most stations. PM concentrations tended to be highest in winter and lowest in summer at most stations, and mineral dust influenced the results in spring. A decreasing interannual trend was observed on the HBP and in southern China for the period 2006 to 2014, but an increasing trend occurred at some stations in northeast China. Bimodal and unimodal diurnal variation patterns were identified at urban stations. Both emissions and meteorological variations dominate the long-term PM concentration trend, while meteorological factors play a leading role in the short term.