2019年元宵节重污染期间济宁市PM2.5化学组分特征及污染成因分析

Analysis of PM2.5 chemical characteristics and causes during heavy pollution in Jining City around the Lantern Festival of 2019

采用观测资料与轨迹模拟相结合的方法,对济宁市2019年元宵节前后出现的一次空气污染过程的大气环境背景、气象因素、污染物变化、组分特征等进行了分析,并探讨了污染成因.结果表明,污染过程中济宁市PM2.5小时浓度峰值为211μg·m-3,主要成分为NO-3、SO2-4、NH+4等二次无机组分,占比之和达到77.4%,钾离子浓度在元宵节夜间增加18倍.在PM2.5质量浓度高值时段,SO2-4占比大幅增加.NO-3/SO2-4值为0.7—0.9,SOR值为0.7—0.8,NOR值为0.5—0.6,一次排放源中燃煤的贡献更为显著.济宁此次重污染过程受元宵节期间烟花燃放和春节后复工影响,本地污染物排放贡献显著.在静稳高湿、近地逆温等不利扩散气象条件下污染物快速累积,气态污染物的二次转化和颗粒物的吸湿增长显著抬升了PM2.5浓度,硫酸盐爆发式增长加剧了污染发生.受偏北风影响,携带高浓度污染物的气团由北向南传输,是济宁市本次污染过程发展的关键因素.建议加强二次无机组分前体物SO2、NOx及NH3排放源的管控,重点关注散煤燃烧和重型柴油车的污染控制,节日期间坚决采取烟花爆竹禁放措施,同时做好秋冬季空气质量预测预警工作,确保各项应急减排措施落实到位,并加强区域间的联防联控,减少污染传输影响.

Based on the analysis of measurement data and air mass trajectory,the study discussed the atmospheric environment background,meteorological factors,pollutant changes and component characteristics of a heavy air pollution process occurred before and after the lantern festival in 2019 in Jining City.During this period,the peak concentration of PM2.5 in the whole area of Jining City was 211μg·m-3,the main components were secondary inorganic components such as NO-3,SO2-4,and NH+4,accounting for 77.4%of the total PM2.5 mass concentration.In particular,compared with non-pollution days,the potassium ion concentration has increased by 18 times during the night of the Lantern Festival.We also found that with the mass concentration of PM2.5 continued to increases,the proportion of SO2-4 components increases significantly.The NO-3/SO2-4 ratio was between 0.7 and 0.9,the SOR value was between 0.7 and 0.8,and the NOR was between 0.5 and 0.6,coal combustion contributed significantly to the primary emission sources.Influenced by the fireworks and firecrackers during the Lantern Festival and industrial sources discharge coursed by resumption of work after the Spring Festival,the local pollutant sources significantly contributed to this heavy pollutions period.Under the static weather,high relative humidity,near-surface radiation inversion and other unfavorable diffusion meteorological conditions,the secondary conversion of gaseous pollutants and the hygroscopic growth of particulate matter make the sulfate explosive growth.Through the analysis of the backward trajectory,air mass contained large amount of pollutants transported from north to south further increased the Jining local degree of pollution.Therefore,we proposed the local government to strengthen the control of secondary inorganic precursors such as SO2,NOx and NH3 emission sources,reduce coarse coal combustion,control heavy-duty diesel vehicles.The government also need to resolutely adopt fireworks and firecracker bans during the holiday season,and improve the accuracy of air quality forecast in autumn and winter as well,ensure that all emergency response measurements are in place,strengthen joint prevention and control between regions.