2022年1月污染过程中常州市PM_(2.5)的变化特征及管控效果评估

Change characteristics and control effect evaluation of Changzhou PM_(2.5) in the pollution process in January 2022

2022年1月1日至25日,常州市经历了5次区域性PM_(2.5)污染过程,其中3天达中度污染。为力争在污染过程中缩时削峰,常州市采取了不同针对性管控措施。本研究基于1月常州市国控空气站的PM_(2.5)在线观测数据,对重污染天气黄色预警管控期间(1月8-14日)和大气污染过程强化削峰管控期间(1月15-25日)PM_(2.5)浓度的变化特征进行了分析,评估了不同管控措施对常州市环境空气中PM_(2.5)浓度改善效果的影响。结果表明,强化管控前常州市PM_(2.5)浓度在苏南五市偏高突出,较非污染过程差距明显拉大,污染过程中PM_(2.5)浓度最高达135μg/m^(3),较其他苏南城市均值偏高13.4%,非污染过程中PM_(2.5)浓度平均为50.0μg/m^(3),较其他苏南城市均值偏高12.6%;16日推进强化管控后削峰管控效果在黄色预警管控基础上有所加强,常州市PM_(2.5)浓度与其他苏南城市差距较前期有所缩小,污染过程中PM_(2.5)浓度最高达90μg/m^(3),与其他苏南城市均值持平。与污染过程前相比(以1日为例),5次污染过程中常州市硝酸根离子浓度分别上升35.7%、43.5%、38.8%、33.7%和25.7%,铵根离子浓度分别上升15.4%、19.0%、16.6%、14.0%、14.4%,二次组分尤其是硝酸根离子、氨根离子浓度偏高是当前常州市PM_(2.5)浓度压降的难点。污染过程中,溧阳市和金坛区PM_(2.5)浓度显著高于全市其他区域,1日-25日累计PM_(2.5)浓度同比反弹幅度分别为全市最高(金坛区)和次高(溧阳市),较全市均值偏高15.4和9.8个百分点,模型模拟结果显示,其内源贡献增加、重点污染源排放量同比上升是主要原因。

From January 1 to 25,2022,Changzhou City has experienced five regional PM_(2.5) pollution processes,among them,three days have mild pollution.In order to reduce the time and peak concentration during the pollution process,Changzhou City has adopted different targeted control measures.Based on the online observation data of PM_(2.5) from the National Air Control Station in Changzhou City in January,this study analyzed the change characteristics of PM_(2.5) 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 PM_(2.5) concentration in the ambient air in Changzhou City.The results show that before strengthening control,the PM_(2.5) 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 PM_(2.5) concentration reached a maximum of 135μg/m^(3),13.4%higher than the average of other cities in southern Jiangsu,and the average PM_(2.5) concentration during non polluting processes is 50.0μg/m 3,12.6%higher than the average in other cities in southern Jiangsu;On the 16 th,after strengthening control measures,the effect of peak shaving control has been strengthened on the basis of yellow warning control.The difference in PM_(2.5) concentration between Changzhou and other cities in southern Jiangsu has narrowed compared to the previous period,with the highest PM_(2.5) concentration reaching 90μg/m^(3) during 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 example),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 ammonium 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 pressure drop of PM_(2.5) concentration in Changzhou City.During the pollution process,the PM_(2.5) concentrations in Liyang City and Jintan District were significantly higher than those in other regions of the city.The cumulative PM_(2.5) concentrations rebounded from the 1 st to 25 th days on a year-on-year basis,with the highest 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 pollution sources on a year-on-year basis.