Study on the characteristics of air quality change in Shenyang city during 2014-2017

Based on the data of air quality in Shenyang city during 2014-2017, the annual air quality index, concentration of pollutants, types and pollution days of major pollutants and the air pollution control effect were analyzed. The results show that the air quality of Shenyang City have been improving in the past four years, and the days of ambient air quality pollution had decreased significantly, and both of the median value and average value of AQI have dropped significantly, and the concentrations of PM2.5 and SO2 have kept decreasing. The annual pollution days with O3 as the major pollutant increased significantly, and the phenomenon of two or three pollutants as the major pollutant group has continued to appear, indicating that the soot type air-pollution represented by PM2.5, SO2, etc. is changing to the combined type air-pollution.