西北工业城市冬季PM2.5污染特征及理化性质

Winter Pollution Characteristics and Physicochemical Properties of PM in a Northwest Industrial City

为研究西北工业城市冬季PM2.5污染特征及理化性质,以甘肃省白银市为例,采用单颗粒气溶胶质谱等相关仪器,开展实时在线PM2.5化学组分观测,与兰州市同期进行对比分析.结果表明,观测期间白银市PM2.5浓度(44.89μg·m^-3)显著低于同期兰州市(70.69μg·m^-3),但含重金属颗粒物占比(7.84%)明显高于兰州市(2.92%),化学组分复杂,PM2.5以较大粒径颗粒物贡献为主;白银含Cu、Pb和Zn颗粒物粒径分布范围较宽,其中含Cu和Zn颗粒物数量、颗粒物混合比多大于兰州市;主要污染源为汽车尾气30.91%和二次无机源13.00%,机动车尾气贡献均高于其他对比城市;2020年1月4日发生的污染过程主要由汽车尾气和二次无机源贡献增加引起,加之前期气象扩散条件较差.白银冬季PM2.5污染治理应以汽车尾气和二次无机源减排为主,同时加强大气重金属污染管控.

To study winter pollution characteristics and physicochemical properties of PM2.5 in a northwest industrial city,for example,Baiyin in Gansu Province,we used related instruments,such as single particle aerosol mass spectrometry to conduct real-time online PM2.5 chemical composition observations,compared with Lanzhou in the same period.The results showed that,during the observation,PM2.5 concentrations(44.89μg·m^-3)in Baiyin were significantly lower than the same period in Lanzhou(70.69μg·m^-3).However,the proportion of particles containing heavy metals(7.84%)was significantly higher than that of Lanzhou(2.92%),the chemical composition was complex,and PM2.5 was mainly contributed by particles with larger particle sizes.The particle size distribution range of Cu,Pb,and Zn particles in Baiyin was relatively wide,the number of Cu and Zn particles was higher,and the mixing ratio of particles was higher than in Lanzhou.The main pollution source was automobile exhaust 30.91%and a secondary inorganic source was 13.00%.The pollution event on January 4,2020 was mainly caused by the increased contributions of automobile exhaust and secondary inorganic sources,and the poor meteorological diffusion conditions in the early stage.The control of PM2.5 pollution in Baiyin in winter should be dominated by emission reduction of automobile exhaust and secondary inorganic sources,and control of heavy metal pollution in the atmosphere should be strengthened.