PM₁₀ and PM₁ concentrations varied similarly at both sites, with average PM₁₀ concentrations 24-25 渭g/m³ and 13-14 渭g/m³ in winter and summer, respectively, and average PM₁ concentrations 12-17 渭g/m³ and 6-7 渭g/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 PM_1-10 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 PM_1-10. 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 PM_1-10 mineral-related sources, with higher contribution in summer; a PM_1-10 salt source; and a PM_1-10 organic source, with higher contribution in summer, attributed to bioaerosols.