[Variational Trend and Characteristics of Air Pollution in Baoding City]

To understand the trends and characteristics of air pollution in Baoding in recent years, an analysis of air quality and air pollutant concentrations in Baoding from 2013 to 2018 was carried out. The results showed that: 1 from 2013 to 2018, the comprehensive index of Baoding dropped from 11.6 to 6.6, the days of severe pollution decreased from 114 days to 27 days, and cumulative concentration of pollutants during severe pollution decreased from 57.34% to 20.59%. This indicated that the air quality of Baoding city has improved year on year from 2013 to 2018. Not only has the number of heavy pollution days and the annual average concentration of pollutants decreased, but also the proportion of cumulative concentrations of pollutants during heavy pollution has decreased. the difference between the average concentration level of Baoding city and "2+26" Cities is getting smaller and smaller. ② Summer ρ(O₃-8h) increased year on year. In 2017 and 2018, the heavy pollution days caused by O₃ accounted for 17.0% and 14.8% of the heavy pollution days of the year, respectively, and the ozone pollution gradually became prominent; the characteristic value of NO₂ in autumn was higher than that of SO₂, CO, PM_2.5, and PM₁₀, indicating that the type of pollution in autumn was more motorized. The sources of pollution in winter changed from the partial combustion of coal in 2013-2014 to a mixed influence of partial combustion of coal and incomplete combustion in 2015-2018. ③ In 2016, 2017, and 2018, a high cumulative concentrations of PM_2.5 during the high pollution season that accounted for 5.56%, 6.21%, and 2.58% declined as compared to that during the same period in 2015; this was the largest decline among the six pollutants; PM₁₀ followed; The decreases of SO₂ and NO₂ were small, indicating that the emergency measures were better in cutting peaks of particulate matter than the gaseous pollutants during heavy pollution in Baoding. In a heavy pollution event during the high pollution season in 2018, partial-burning coal-type pollution increased as compared to that during the high pollution season in 2017, indicating that the coal combustion was still one of the pollution sources that Baoding city needed to control. In summary, Baoding should strengthen the management and control of motor vehicles in autumn, and gradually change from the original coal control measures to a combination of coal control and diesel control in winter; in the future, the focus of air pollution prevention and control should be strengthened toward O₃ pollution.