Abstract
Abstract. Aerosol particles play important roles in regional air quality and global climate change. In this study, we analyzed 2 years (2011–2013) of measurements of submicron particles (6–800 nm) at a suburban site in the western Yangtze River Delta (YRD) of eastern China. The number concentrations (NCs) of particles in the nucleation, Aitken and accumulation modes were 5300 ± 5500, 8000 ± 4400, 5800 ± 3200 cm−3, respectively. The NCs of total particles are comparable to those at urban/suburban sites in other Chinese megacities, such as Beijing, but about 10 times higher than in the remote western China. Long-range and regional transport largely influenced number concentrations and size distributions of submicron particles. The highest and lowest accumulation-mode particle number concentrations were observed in air masses from the YRD and coastal regions, respectively. Continental air masses from inland brought the highest concentrations of nucleation-mode particles. New particle formation (NPF) events, apparent in 44 % of the effective measurement days, occurred frequently in all the seasons except winter. The frequency of NPF in spring, summer and autumn is much higher than other measurement sites in China. Sulfuric acid was found to be the main driver of NPF events. The particle formation rate was the highest in spring (3.6 ± 2.4 cm−3 s−1), whereas the particle growth rate had the highest values in summer (12.8 ± 4.4 nm h−1). The formation rate was typically high in relatively clean air masses, whereas the growth rate tended to be high in the polluted YRD air masses. The frequency of NPF events and the particle growth rates showed a strong year-to-year difference. In the summer of 2013, associated with a multi-week heat wave and strong photochemical processes, NPF events occurred with larger frequency and higher growth rates compared with the same period in 2012. The difference in the location and strength of the subtropical high pressure system, which influences the air mass transport pathways and solar radiation, seems to be the cause for year-to-year differences. This study reports, up to now, the longest continuous measurement records of submicron particles in eastern China and helps to achieve a comprehensive understanding of the main factors controlling the seasonal and year-to-year variation of the aerosol size distribution and NPF in this region.
Highlights
Atmospheric aerosols affect human life by influencing both air quality and climate (e.g., Charlson et al, 1992; Menon et al, 2002; Akimoto, 2003; Heal et al, 2012; IPCC, 2013)
The number concentrations (NCs) of total particles at SORPES in Nanjing are comparable to those measured at the urban site (Wu et al, 2008) and at a rural site in Beijing (Shen et al, 2011), while about 10 times higher than those measured at Mount Waliguan, a remote background site in western China (Kivekäs et al, 2009)
One typical feature at SORPES is the high concentration of accumulation-mode particles, which can be up to several times the typical concentrations measured in Europe or North America (200–2900 cm−3 compared to 5700 cm−3 at SORPES in the size range of 100–500 nm) (Stanier et al, 2004; Asmi et al, 2011; Wang et al, 2011)
Summary
Atmospheric aerosols affect human life by influencing both air quality and climate (e.g., Charlson et al, 1992; Menon et al, 2002; Akimoto, 2003; Heal et al, 2012; IPCC, 2013). Numerous studies have been conducted all over the world focusing on the characters of submicron particles, including their chemical composition and size distribution as well as their formation and growth in the atmosphere (e.g., Woo et al, 2001; Birmili et al, 2003; Engler et al, 2007; Zhang et al, 2007; Dal Maso et al, 2008; Laakso et al, 2008; Jimenez et al, 2009; Komppula et al, 2009; Asmi et al, 2011; Kerminen et al, 2012; Vakkari et al, 2013; Kulmala et al, 2014; Nie et al, 2014; Nieminen et al, 2014). Knowledge about the temporal variation of submicron particles and their relationship to meteorology and human activities in China is rather poor, even in some well-developed regions such as Yangtze River Delta (YRD) in eastern China
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