Abstract
Abstract. The aim of this study was to characterise the new particle formation events in a subtropical urban environment in the Southern Hemisphere. The study measured the number concentration of particles and its size distribution in Brisbane, Australia during 2009. The variation of particle number concentration and nucleation burst events were characterised as well as the particle growth rate which was first reported in urban environment of Australia. The annual average NUFP, NAitken and NNuc were 9.3×103, 3.7×103 and 5.6×103 cm−3, respectively. Weak seasonal variation in number concentration was observed. Local traffic exhaust emissions were a major contributor of the pollution (NUFP) observed in morning which was dominated by the Aitken mode particles, while particles formed by secondary formation processes contributed to the particle number concentration during afternoon. Overall, 65 nucleation burst events were identified during the study period. Nucleation burst events were classified into two groups, with and without particles growth after the burst of nucleation mode particles observed. The average particle growth rate of the nucleation events was 4.6 nm h−1 (ranged from 1.79–7.78 nm h−1). Case studies of the nucleation burst events were characterised including (i) the nucleation burst with particle growth which is associated with the particle precursor emitted from local traffic exhaust emission, (ii) the nucleation burst without particle growth which is due to the transport of industrial emissions from the coast to Brisbane city or other possible sources with unfavourable conditions which suppressed particle growth and (iii) interplay between the above two cases which demonstrated the impact of the vehicle and industrial emissions on the variation of particle number concentration and its size distribution during the same day.
Highlights
Understanding the formation process of atmospheric particles is vital because of the significant impact of particulate matter on human health and climate change (Charlson et al, 1992; Donaldson et al, 1998)
The NUFP and Nnuc measured in this study were about 8 % and 60 % higher than those measured by Mejıa et al (2007), being 8.6×103 cm−3 and 3.5×103 cm−3, respectively
In relation to Nnuc, it should be noted that the nucleation mode particle concentration in this study covered particles in the size range 4–30 nm, and it is expected to be higher than the earlier result reported by Mejıa et al (2007)
Summary
Understanding the formation process of atmospheric particles is vital because of the significant impact of particulate matter on human health and climate change (Charlson et al, 1992; Donaldson et al, 1998). Weber et al, 2001), boreal forests (e.g. Vehkamaki et al, 2004) and coastal areas (e.g. O’Dowd et al, 1999; Lee et al, 2008) Most of these studies focused on particle formation in rural settings and in colder climates, with very few studies conducted in urban environments, especially in the Southern Hemisphere (Kulmala et al, 2004). Woo et al, 2001; Moore et al, 2007; Wu et al, 2008) and coastal (Pey et al, 2008; Rodrıguez et al, 2008; Fernandez-Camacho et al, 2010; Perez et al, 2010) urban areas These studies examined the variation of particle number concentration in urban environments.
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