Change characteristics and control effect evaluation of Changzhou PM2.5 in the pollution process in January 2022
From January 1 to 25,2022,Changzhou City has experienced five regional PM2.5 pollution processes,among them,three days have mild pollution.In order to reduce the time and peak concen-tration during the pollution process,Changzhou City has adopted different targeted control measures.Based on the online observation data of PM2.5 from the National Air Control Station in Changzhou City in January,this study analyzed the change characteristics of PM2.5 concentration during the yellow warning and control period for heavily polluted weather(January 8-14)and during the intensified peak shaving control period for air pollution processes(January 15-25),and evaluated the impact of different control measures on the improvement of PM2.5 concentration in the ambient air in Changzhou City.The re-sults show that before strengthening control,the PM2.5 concentration in Changzhou City was significantly higher than that in the five cities in southern Jiangsu,with a significant gap widening compared to non polluting processes.During the pollution process,the PM2.5 concentration reached a maximum of 135μg/m3,13.4%higher than the average of other cities in southern Jiangsu,and the average PM2.5 concentration dur-ing non polluting processes is 50.0 μg/m3,12.6%higher than the average in other cities in southern Jiangsu;On the 16th,after strengthening control measures,the effect of peak shaving control has been strengthened on the basis of yellow warning control.The difference in PM2.5 concentration between Chang-zhou and other cities in southern Jiangsu has narrowed compared to the previous period,with the highest PM2.5 concentration reaching 90 μg/m3during the pollution process,which is similar to the average of other cities in southern Jiangsu.Compared with before the pollution process(taking the first day as an ex-ample),the concentration of nitrate ions in Changzhou City increased by 35.7%,43.5%,38.8%,33.7%,and 25.7%respectively during the five pollution processes,while the concentration of ammoni-um ions increased by 15.4%,19.0%,16.6%,14.0%,and 14.4%respectively.The high concentration of secondary components,especially nitrate ions and ammonia ions,is currently the difficulty in the pres-sure drop of PM2.5concentration in Changzhou City.During the pollution process,the PM2.5 concentrations in Liyang City and Jintan District were significantly higher than those in other regions of the city.The cu-mulative PM2.5 concentrations rebounded from the 1st to 25th days on a year-on-year basis,with the high-est and second highest levels in the city(Jintan District)and Liyang City,respectively,which were 15.4 and 9.8 percentage points higher than the city's average.The model simulation results showed that the main reasons were an increase in endogenous contributions and an increase in emissions from key pol-lution sources on a year-on-year basis.