Size distributions and elemental compositions of particulate matter on clear, hazy and foggy days in Beijing, China

Abstract

Total suspended particulates (TSP) samples were collected using low pressure impactors (Andersen Series 20–800, USA) on typical clear, hazy and foggy days in Beijing in order to investigate the characteristics of size distributions and elemental compositions of particulate matter (PM) in different weather conditions. The concentrations of sixteen elements, including Na, Mg, Al, K, Ca, Mn, Fe, Ni, Cu, Zn, As, Se, Cd, Ba, Tl and Pb were detected using inductively coupled plasma mass spectrometry (ICP-MS). The results showed that Ca, Al, Fe, Mg and Ba on foggy days were 2.0–2.6 times higher than on clear days, and 2.3–2.9 times higher than on hazy days. Concentrations of Cu, Zn, As, Se and Pb on foggy days were 163.5, 1186.7, 65.9, 32.0 and 708.2 ng m⁻³, respectively, in fine particles, and 68.1, 289.5, 19.8, 1.6 and 103.8 ng m⁻³, respectively, in coarse particles. This was 1.0–8.4 times higher and 1.4–7.4 times higher than on clear and hazy days, respectively. It is then shown that Mg, Al, Fe, Ca and Ba were mainly associated with coarse particles, peaking at 4.7–5.8 µm; that Cd, Se, Zn, As, Tl and Pb were most dominant in fine particles, peaking at 0.43–1.1 µm; and that Na, K, Ni, Cu and Mn had a multi-mode distribution, with peaks at 0.43–1.1 µm and 4.7–5.8 µm. The enrichment factors indicated that coal combustion along with vehicle and industry emissions may be the main sources of pollution elements.