Characteristics Of Ambient Air Pollution And Process Of Heavy Pollution Events In Jinzhong City,Shanxi Province

In July 2018,the State Council formally replaced the Pearl River Delta with Fenwei Plain in the "Three-year Action Plan for Winning the Blue Sky Defense War".In the air quality ranking of 169 key cities in China in 2018,six cities in the Fenwei Plain ranked the bottom 20,of which Jinzhong ranked 154,and the situation is not optimistic.In order to find out the pollution status of Jinzhong City,this study is based on the environmental monitoring data of Jinzhong City from 2016 to 2018 and the meteorological data of the same period.It used correlation analysis,wavelet analysis,backward trajectory simulation,sand dust transmission simulation and other methods to explore the characteristics of air pollution in Jinzhong City and the process of heavy pollution in the main urban area.The results show that:（1）From 2016 to 2018,the annual average value of AQI in Jinzhong City was high in the West and low in the east.The high AQI value is located in the southwest,including Lingshi,Jiexiu,Pingyao and other counties.The average seasonal value of AQI was high in winter and low in summer.The primary pollutants in Jinzhong City are PM_2.5,PM₁₀ and O₃.（2）The concentrations of PM_2.5,SO₂ and CO in the main cities showed a downward trend,while the concentrations of PM₁₀,NO₂ and O₃ showed different degrees of increase.The concentration of each pollutant is high in winter and low in summer（except O₃）.The diurnal variations of PM_2.5,PM₁₀ and SO₂ showed bimodal variations.The NO₂ daily change showed a significant low value between 14:00-16:00.The diurnal variation of CO concentration was small,and the variation of O₃ concentration was a typical single peak.（3）In the southerly winds,pollutants tend to accumulate,while northwest winds and westerly winds were conducive to the spread of pollutants.Except for O₃,wind speed and temperature are negatively correlated with the concentration of each pollutant.Relative humidity had a greater impact in winter,and high humidity was conducive to the reduction of SO₂ and NO₂ concentrations.The correlation between air pressure and concentration of various pollutants was weak.（4）The heavily polluted weather in Jinzhong City occured in winter and spring and the primary pollutants in the heavy pollution process in Jinzhong City were PM_2.5 and PM₁₀.The heavy pollution process with PM_2.5 as the primary pollutant mainly occurs in winter.During heavy pollution,the change rules of various pollutants were similar,and the first main cycle wasbetween 100 and 150 hours.In the process of heavy pollution with PM₁₀ as the primary pollutant,the concentration of particulate matter exceeded the standard,while the concentration of gaseous pollutants was normal.Combined with the backward trajectory simulation and the NAPPS dust transmission model simulation,the heavy pollution may be affected by the dust weather.This paper provides a powerful basis for the government departments to formulate corresponding control measures by summarizing the temporal and spatial distribution of pollutants in Jinzhong City and analyzing the impact of different meteorological factors on pollutant concentration.