Chemical Composition of Fine and Coarse Particles at Wuqing during the HaChi Summer Campaign

摘要

To characterize regional aerosol pollution of North China Plain (NCP), fine (PM2.5) and coarse particle (PM2.5-10, between 2.5 and 10 microns in size) samples were collected during the HaChi (Haze in China) field campaign in the summer of 2009, at a suburban site Wuqing which located between two important mega-cities Beijing and Tianjin at the northern edge of NCP. The average mass concentrations of PM2.5 and PM10 were 74.90±38.53 and 97.47±47.52 μg/m3, respectively, with PM2.5/ PM10 ratio of 76%±7%. Secondary inorganic compounds (sulfate, nitrite and ammonium) accounts for 57% in fine particles, indicating the serious secondary pollution. Particle pollution during the campaign showed meteorological dependent. When the weather was stagnant, fine particle concentration, especially secondary components, accumulated steadily. On the contrary, when heavy rain combined with northern strong wind occurred pollution was scavenged with great efficiency. Back trajectory cluster analysis was applied to classifying air mass trajectories and the weather situations governing the receptor site, yielding three trajectory clusters, arrived at Wuqing from the northwest (13%), northeast (15%) and south (72%). Wuqing was mostly influence by regional secondary pollution of the North China Plain in the summer, while occasionally strong wind bring air mass from the northwest and primary pollution would be obvious.