长治市冬季典型大气重污染过程特征分析

Characteristic of typical atmospheric heavy pollution episodes in winter of Changzhi

为研究长治市冬季大气重污染过程特征,本文以2019年1月1日—15日发生的一次典型大气重污染过程为例,从污染过程、气象条件、颗粒物化学组分及源解析结果等角度综合分析此次重污染过程的特征和成因.结果表明,此次污染期间PM_(10)、PM_(2.5)浓度增加显著,首要污染物是PM_(2.5),其平均质量浓度为142μg·m^(-3);低风速(均值为2.6 m·s^(-1))与高湿度(均值为57.9%)共同作用形成高湿静稳天气,促进了PM_(2.5)的形成和累积;污染过程中PM_(2.5)中水溶性离子SO^(2-)_(4)和NO^(3-)显著增加,硫氧化率(SOR)和氮氧化率(NOR)分别为清洁阶段时的3.0倍和2.8倍,二次无机转化对PM_(2.5)浓度增加的贡献较大;污染阶段中OC、EC平均浓度分别是清洁阶段时的2.9、1.7倍,且二次有机碳(SOC)占OC的60.1%;二次源、燃煤源、机动车源和扬尘源是此污染过程中的主要污染源,贡献比例分别为46.7%、30.1%、17.5%和5.7%.因此,此次污染过程中污染物在高湿静稳天气下积累和吸湿增长,SO_(2)、NO_(2)等前体污染物的二次转化和燃煤源等一次污染源排放的污染物是污染发生的重要原因.故在长治市冬季期间控制二次污染物的前体物排放和燃煤源等一次污染源是降低重污染程度的关键.

To discuss the characteristics of atmospheric heavy pollution in winter of Changzhi,a typical atmospheric heavy pollution process from January 1st to 15th,2019 was taken in this study as an example,with the perspectives of pollution process,meteorological conditions,chemical composition of particles and source analysis results.The major results were obtained as follows.During the pollution stage,the concentration of PM_(10)and PM_(2.5)increased significantly.The primary pollutant was PM_(2.5)with the average concentration of 142μg·m^(-3).The combination of low wind speed(average 2.6 m·s^(-1))and high relative humidity(average 57.9%)formed the stagnant meteorological situation with high humidity,which could promote the formation and accumulation of PM_(2.5).The concentration of SO^(2-)_(4)and NO^(-)_(3)in PM_(2.5)were significantly increased in pollution stage,and the sulfur oxidation rate(SOR)and nitrogen oxidation rate(NOR)in pollution stage were 3.0 and 2.8 times of that in the cleaning stage,respectively.The secondary inorganic conversion had a greater contribution to the increasement of PM_(2.5)concentration.The average concentration of OC and EC in the pollution stage was 2.9 and 1.7 times than that in the cleaning stage,respectively,and secondary organic carbon(SOC)accounted for 60.1%of OC in the pollution stage.Secondary source,coal combustion source,motor vehicle source and dust source were the main pollution sources,which accounting for 46.7%,30.1%,17.5%and 5.7%,respectively.Therefore,the secondary transformation of precursor pollutants,such as SO_(2)and NO_(2),and primary sources such as coal combustion source were the important causes of atmospheric heavy pollution.Controlling emission of the precursor of secondary pollutants and the primary sources such as coal combustion source during the winter in Changzhi is the key to reducing the heavy pollution level.