Inter-annual and seasonal variability in PM10 samples monitored in the city of Turin (Italy) from 2002 to 2005

The temporal trends of ten elements, namely Cl, Cu, Cr, Fe, Mg, Ni, P, S, Zn and Zr, in airborne particulate matter sampled in the urban area of Turin (Piedmont, Italy) were determined by wavelength dispersive X-ray fluorescence for the period from 2002 to 2005. The average daily concentrations were as follows: Cl 322 ng/m3 ; Cr 16.4 ng/m3 ; Cu 8.19 ng/m3 ; Fe 274 ng/m3 ; Mg 1501 ng/m3 ; Ni 7.33 ng/m3 ; P 19.8 ng/m3 ; S 1206 ng/m3 ; Zn 333 ng/m3 and Zr 8.15 ng/m3 . Some elements, namely Al, Ba, Ca, K, Na, Si and Sr, were not quantifiable using XRF because of the too high contribution from the filter blank. A clear seasonal pattern with higher concentrations of most of the elements in the cold periods was observed. Moreover, no marked change in the element distribution in atmospheric particulate matter over 4 years was evidenced during the sampling period, to indicate that similar sources have influenced the elemental composition of it in these last years. The application of multivariate chemometric techniques (principal component analysis and hierarchical cluster analysis) to the experimental results allowed us to identify correlations among the investigated elements and to reveal similarities and differences between sampling sites.