Volume 16, No. 7, July 2016, Pages 1591-1602 PDF(5.07 MB)
Observations of New Particle Formation, Subsequent Growth and Shrinkage during Summertime in Beijing
Jiaoshi Zhang1,2, Zhenyi Chen1, Yihuai Lu1, Huaqiao Gui1, Jianguo Liu1, Jie Wang1, Tongzhu Yu1, Yin Cheng1
1 Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China
2 University of Science and Technology of China, Hefei 230026, China
- New particle formation under different conditions is studied.
- Growth rate of newly formed particles correlates with coagulation sink.
- Particle shrink in a high shrinkage rate is observed in Beijing.
Size-resolved aerosol number concentrations (10 nm–10 µm in diameter) were measured at an urban site in Beijing during summertime of 2008. Case studies of new particle formation (NPF) are presented in this work. The measured mean particle formation rate was 2.37 cm–3 s–1, which varied from 1.5 to 3.8 cm–3 s–1, with growth rates ranging from 3.2 to 10.6 nm h–1. NPF was observed under low number concentration of preexisting particles as well as under relatively high number concentration of preexisting particles. It was found that condensation contributed mainly and preferentially to particles growth, however, coagulation would contribute a lot when formation rate of new particles was sufficiently high. The variation of concentration of nucleation mode particles was found to be coincident with sulfur dioxide, indicating that NPF could occur under relatively high number concentration of preexisting particles if sufficient concentration of gas-phase H2SO4 existed in the atmosphere. Grown particles were also observed to shrink from 61.1 nm to 15.4 nm at a shrinkage rate of 16.6 nm h–1, accompanied by a reduction of the particle number concentration. The shrinkage rate was higher than those reported in recent studies, probably due to particle shrinkage occurred during summertime in Beijing with higher temperature and lower RH compared to those observed in other regions, thus enhanced particle shrinkage.
Particle formation; Growth; Particle shrinkage; Beijing.