Fine and coarse PM composition and sources in rural and urban sites in Switzerland: Local or regional pollution? Original Research Article

The chemical composition and sources of ambient particulate matter (PM) in Switzerland were studied. PM1 and PM10 samples were collected in winter and summer at an urban background site in Zurich and a rural background site in Payerne. Concentrations of major and trace elements, NO3−, SO42−, NH4+, organic and elemental carbon were determined. A subsequent Positive Matrix Factorization (PMF) analysis was performed. PM10 and PM1 concentrations varied similarly at both sites, with average PM10 concentrations 24–25 μg/m3 and 13–14 μg/m3 in winter and summer, respectively, and average PM1 concentrations 12–17 μg/m3 and 6–7 μg/m3. The influence of local sources was found to be higher in winter. PM was dominated by nitrate and organic matter in winter, and by mineral matter and organic matter in summer. Trace element concentrations related to road traffic (Zn, Cu, Sb, Sn) were higher at Zurich. Concentrations of Tl and Cs, attributed to the influence of a glass industry, were higher at Payerne. The elements mainly present in the coarse fraction were those related to mineral matter and brake and tyre abrasion (Cu, Mn, Ti, Sb, Sr, Bi, Li, La, Nd), and those in the fine fraction were related to high temperature anthropogenic processes (Pb, As, Cd, Tl, Cs). Common PM1 and PM1–10 sources identified by PMF were: ammonium nitrate, present in winter, negligible in summer; ammonium sulfate + K(biomass burning) + road traffic; and road traffic itself, related to exhaust emissions in PM1 and to road dust resuspension in PM1–10. Size-fraction specific sources were: a PM1 glass industry source characterized by Cs, Tl, Rb, Li and Na, only present in Payerne; a PM1 background source characterized by V, Ni, sulfate and Fe; two PM1–10 mineral-related sources, with higher contribution in summer; a PM1–10 salt source; and a PM1–10 organic source, with higher contribution in summer, attributed to bioaerosols.