Physico-chemical characterisation of the inhalable particulate matter (PM10) in an urban area: an analysis of the seasonal trend.

Between October 1998 and February 2000, 11 particulate samplings were conducted in an urban area of Rome to evaluate the seasonal trend of PM10 characteristics: seven samplings were made at ground-level and four 30 m above ground level. The samples were analysed by scanning electron microscopy equipped with an EDS X-ray attachment and by transmission electron microscopy and an electron energy-loss spectrometer. The airborne particulate matter was characterised from a physico-chemical point of view to provide information on the particle composition and on the compounds carried on their surface. The data sets, consisting of the atomic concentrations of the constituent chemical elements of the fine (PM3.3) and of the coarse (PM10-3.3) particulate, were subjected to cluster analysis to determine the principal components of PM10. In the particulate matter, the statistical analysis methods allowed us to identify seven groups (clusters) of particles: C-rich particles; carbonates; silica; silicates; sulfates; Fe-rich particles; and metals. Carbonaceous and silicate particles with a surface coating containing S were observed. This sulfur-enriched coating turned out to be a PM3.3 feature strongly dependent upon season.