Observations of New Particle Formation, Subsequent Growth and Shrinkage during Summertime in Beijing

Abstract

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 gasphase H 2 SO 4 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 , 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.

New Particle Formation in the Atmosphere: From Molecular Clusters to Global Climate

“…Atmospheric observations show sometimes distinctive shrinkage (as opposed to growth) events of newly formed particles, usually associated with high temperatures (Alonso‐Blanco et al, ; Cusack et al, ; Salma et al, ; Skrabalova et al, ; Yao et al, ; Young et al, ; Zhang et al, ). These observations imply that SVOCs are also involved in the growth of new particles.…”

New particle formation, growth and apparent shrinkage at a rural background site in western Saudi Arabia

“…Stabilizing bases, such as ammonia and dimethylamine, low-volatility oxidation products of VOCs (volatile organic compounds) and ions have been shown to enhance particle formation rates and bridge some of the gaps between theoretical evaluations, laboratory studies and ambient measurements (H. Yu et al, 2012;F. Yu et al, 2018;Almeida et al, 2013;Kürten et al, 2014Kürten et al, , 2016Kürten et al, , 2018Zhang et al, 2004;Riccobono et al, 2014). The initial particle-forming compounds will also participate in growing the particles, but, in order to explain the observed growth rates, the presence of more abundant condensing (or otherwise particle mass forming, for example, via heterogeneous oligomer formation) species is required (Nieminen et al, 2010;Riccobono et al, 2012).…”

Particle Formation in a Complex Environment

“…High CS is associated with high pre-existing particles. Pre-existing particles provide a significant sink for condensable vapours in the atmosphere, which may prevent particle formation and growth [71]. High CS rates can be one of the factors that drove the observed Class II particle formation and growth on 9 February 2013.…”

“…A decrease of the total particles several minutes before a clear particle formation observed is a common observation. This can be due to coagulation [13,71].…”