Measurements of sub-3 nm particles using a particle size magnifier in different environments: from clean mountain top to polluted megacities

Abstract

Abstract. The measurement of sub-3 nm aerosol particles is technically challenging. Therefore, there is a lack of knowledge about the concentrations of atmospheric sub-3 nm particles and their variation in different environments. In this study, the concentrations of ∼ 1-3 nm particles measured with a particle size magnifier (PSM) were investigated at nine sites around the world. Sub-3 nm particle concentrations were highest at the sites with strong anthropogenic influence. In boreal forest, measured particle concentrations were clearly higher in summer than in winter, suggesting the importance of biogenic precursor vapors in this environment. At all sites, sub-3 nm particle concentrations had daytime maxima, which are likely linked to the photochemical production of precursor vapors and the emissions of precursor vapors or particles from different sources. When comparing ion concentrations to the total sub-3 nm particle concentrations, electrically neutral particles were observed to dominate in polluted environments and in boreal forest during spring and summer. Generally, the concentrations of sub-3 nm particles seem to be determined by the availability of precursor vapors rather than the level of the sink caused by preexisting aerosol particles. The results also indicate that the formation of the smallest particles and their subsequent growth to larger sizes are two separate processes, and therefore studying the concentration of sub-3 nm particles separately in different size ranges is essential.

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

“…Nucleation measurements at ~1 nm show that J values in three megacities, Mexico City, Nanjing, and Shanghai, for example, are 2 orders of magnitude higher than those observed in the boreal forest (Kulmala et al, ). A global comparison of sub‐3‐nm particle number concentrations ( N sub‐3 ) further indicates that N sub‐3 in polluted megacities could be up to 2 orders of magnitude higher than in clean and moderately polluted environments (Kontkanen et al, ). When particles grow to 3–15 nm, the J values decay to a few to tens of new particles per cubic centimeter per second but are still higher than, or at least comparable to, those in rural and remote environments (Kulmala, Vehkamäki, et al, ).…”

“…For example, NPF in Beijing was characterized by high frequencies during the spring and winter than the summer. In comparison to the boreal forest, the Helsinki urban atmosphere also showed a less distinctive seasonal difference in N sub‐3 between winter and summer (Kontkanen et al, ). The fundamental reasons for these differences imply the balance between factors that contribute to or suppress NPF and growth.…”

Long-term analysis of clear-sky new particle formation events and nonevents in Hyytiälä

“…While primary emissions are a very important source of atmospheric aerosol particles, especially in terms of the aerosol mass loading, the particle number concentration is greatly affected by atmospheric new particle formation (NPF). During the last couple of decades, NPF has been observed to take place almost all over the world (Kulmala et al, 2004a;Zhang et al, 2011;Bianchi et al, 2016;Kontkanen et al, 2016aKontkanen et al, , 2017. Atmospheric NPF is thought to be the dominant source of the total particle number concentration ) and a major source of cloud condensation nuclei in the global tro-posphere (Merikanto et al, 2009;Yu et al, 2010;Kerminen et al, 2012;Salma et al, 2016).…”

Data inversion methods to determine sub-3 nm aerosol size distributions using the particle size magnifier

“…The particle size magnifier (PSM) using diethylene glycol as a working fluid (Vanhanen et al, 2011) is widely used in new particle formation studies (Kulmala et al, 2012Kontkanen et al, 2017) …”