Abstract:Based on the observations of PM2.5 mass concentration, reactive gases and related meteorological elements in Beijing, Tianjin, Shijiazhuang and Zhengzhou from December 2016 to February 2017, the physical and chemical characteristics of the air pollution, transmission and elimination rules are discussed. The results show that the frequency distributions of PM2.5 mass concentration in Beijing, Shijiazhuang, Tianjin and Zhengzhou all had two obvious peaks. The mean values of PM2.5 concentrations were 10.1, 19.2, 40.0 and 47.1 μg?m-3 in the four regions respectively at the time with the highest PM2.5 frequency distribution. The degree of air oxidation in Beijing was the lowest followed by Shijiazhuang, Tianjin and Zhengzhou in order. Traffic sources had important contribution to the environmental air pollution in the four study areas. The correlation between CO and PM2.5 at low relative humidity was higher than that with high humidity. However, the correlation between NO2 and PM2.5 at low relative humidity was lower than that with high humidity. With the wind speed increasing, the PM2.5 mass concentration decreased rapidly and then tended to be gentle, of which the wind speed threshold was 3 m?s-1 in Beijing, Shijia zhuang and Zhengzhou, and for Tianjin it was 4 m?s-1. Affected by upstream pollution transport, southerly wind transport effect was about 20-30 h later than reaching the maximum and the effect of the northerly wind delayed 8-12 h before reaching the maximum.