Abstract
High temporal resolution (5 min) particle size distribution data (0.5. 20 mu m) were collected using aerodynamic particle sizer at an urban (Lanzhou) and a suburban (Yuzhong) site at Lanzhou, northwest China from 1(st) August to 31(st) October 2010. Variations of particle concentrations and properties of volume size distributions (PVSD) were analyzed and urban pollution characteristics were investigated using PVSDs and chemical analysis. The average particle number, surface area and volume concentrations for size range 0.5. 10 mu m were 280.54 +/- 270.92 cm(-3), 331.04 +/- 316.95 mu m(2) cm(-3) and 93.01 +/- 127.75 mu m(3) cm(-3), respectively, at the urban site, which were 2.87, 1.50 and 1.62 times higher than those at the suburban site. Compared with the suburban site, shifts of accumulation mode (0.5. 1.0 mu m) to a smaller size and the coarse mode (1.0. 10 mu m) to a larger size of the PVSDs were observed at the urban site, which may be related to elevated fossil fuel burning and municipal construction or fugitive dust, respectively, in urban area. K-means cluster analysis was used to group the PVSD into six clusters representing the effect of different sources and meteorological conditions. PVSDs at the urban site were dominated by clusters affected by local anthropogenic sources and secondary aerosols, which was characterized by bimodal with peaks at accumulation mode and coarse mode, respectively, while those affected by construction works, wind-borne dust, and dust events were dominated by coarse mode. Chemical composition analysis of PM2.5 samples collected on days representing different clusters confirmed the assignment of clusters to different sources.
Highlights
Atmospheric aerosols are primary pollutants affecting the air quality of most urban areas in China and have attracted increasingly attention in recent years due to their effects on visibility (Jung and Kim, 2006), human health (Strak et al, 2012) and climate (Paasonen et al, 2013)
The particle concentrations in different size bins are much higher at the urban site (Lanzhou) than those at the suburban site (Yuzhong) during the study period, which is significant for the size range 0.5‒1.0 μm
Shifts of the accumulation mode (0.5‒1.0 μm) to a smaller size and the coarse mode (1.0‒10 μm) to a larger size of the properties of volume size distributions (PVSD) were observed at the urban site, which may be related to more fine particles from elevated anthropogenic emissions, e.g., road traffic, coal burning etc. and more coarse particles (1.0‒10 μm) from construction activities and resuspended/fugitive dust, respectively, in urban area
Summary
Atmospheric aerosols are primary pollutants affecting the air quality of most urban areas in China and have attracted increasingly attention in recent years due to their effects on visibility (Jung and Kim, 2006), human health (Strak et al, 2012) and climate (Paasonen et al, 2013). Shape and compositions, particle size distributions have been found to be an important factor affecting the behaviour of aerosols in the atmosphere (Dusek et al, 2006; See et al, 2006). Since the 1970s, many important results about particle size distribution properties and their influencing factors have been obtained under various environments, e.g., urban (Hussein et al, 2004; Yue et al, 2013), near highway (Buonanno et al, 2009; Wang et al, 2001; Wehner et al, 2002) and background stations (Tunved et al, 2004; Liu et al, 2008; Shen et al, 2011; Croft et al, 2016). Particles emitted from motor vehicles are major particulate pollution sources, especially fine particles (Morawska et al, 1998). Harrison et al (1999) and Buonanno et al (2009) found that particle number concentration was 7.5 times and more than 3 times higher than the background level near a busy road and at two urban background locations, respectively. Ketzel et al (2004) suggested that the average
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