2019年1月长春市一次霾污染过程成因分析

Causes of a haze pollution event in Changchun in January of 2019

利用空气质量历史监测数据、地面气象要素及激光雷达探测资料,综合分析了2019年1月10-15日长春市一次霾污染过程,探讨了污染过程中污染物和气象要素的变化特征与影响机制。结果表明:此次霾污染过程中12-13日污染最重,PM2.5和PM10质量浓度均超过150μg·m-3,气溶胶消光最强,超过70%的PM2.5/PM10比值大于0.7,指出了细粒子对重污染事件的贡献;重污染期间近地面风速偏小、相对湿度增加、变压较小,同时低空风出现明显的风向转变,弱下沉运动与逆温以及较低的边界层共同削弱了大气的水平和垂直扩散能力,有利于污染物累积,导致霾污染。500 h Pa天气形势表明长春市位于槽前脊后,850 h Pa高度场为弱西风,相对湿度大;海平面气压场存在低压气旋及弱西南气流,该气流有利于将污染物输送至长春市,造成霾污染加剧;1月14-15日高空槽加深东移,850 h Pa西北气流增强,近地面气压梯度力变大,污染物得到扩散,霾污染逐渐结束。

Using air quality monitoring data,surface meteorological data,and Li DAR detection data,we analyzed the variation of air pollutants and meteorological parameters and the influence mechanisms during a haze pollution event in Changchun during January 10-15,2019. The results showed that the heaviest pollution period occurs on January12-13,with mass concentrations of PM2.5 and PM10 exceeding 150 μg·m-3 and the aerosol extinction coefficient reaching the highest level. The PM2.5/PM10 ratio values are higher than 0. 7 at most times( > 70%),indicating the important contribution of fine particles to this heavy pollution event. During heavy pollution period,near-surface wind speed remains low,relative humidity increases,air pressure varies hardly,and low-level wind direction changes. Weak descending motion,temperature inversion,and shallow boundary layer weaken the horizontal and vertical diffusion capacity of the atmosphere together,which favors the accumulation of air pollutants and the formation of this haze pollution. Changchun is located ahead of a trough and in the rear of a ridge at 500 h Pa. Meanwhile,weak westerly winds prevail and relative humidity is high at 850 h Pa. The sea-surface air pressure field is characterized by low-pressure cyclones and weak southwest flows,which results in the transport of pollutants to Changchun and enhances haze pollution. On January 14-15,the upper-level trough is deepened and moves eastwards,and the northwest airflow at 850 hPa and the near-surface pressure gradient are strengthened,leading to the dispersion of air pollutants and ending this haze pollution event.