Characterisation of the local topsoil contribution to airborne particulate matter in the area of Rome (Italy). Source profiles.

Elemental profiles of the local resuspended natural topsoil of Rome area have been studied. Relevant compositional differences were observed either among main geological domains and rock types of this area (volcanics, flysch, marlstone, travertine) or between the two considered dimensional fractions (50 mm and PM10 resuspended from the former). A significant enrichment in trace metals (especially Pb, Ni and Cr) has been observed in the PM10 resuspended fraction of either volcanics or sedimentary outcropping rocks; volcanics show larger trace metals enrichment than sedimentary. Profiles of this study have been compared with signatures of natural crustal dust of African origin (collected either in situ or at European receptor sites, including Rome and other sites in the Latium region) and with signatures of road dust, properly selected from literature. This comparison was performed for source apportionment goals, with the aim of improving discrimination among signatures of local and non-local natural crustal materials. Elemental ratios of major and trace elements of geochemical relevance were used for the comparative study. Mg/Ca and Ti/Ca ratios appear successful in separating, by dispersion diagram, the resuspended fraction of local Rome geological topsoil from road dust and from long-range transported dust from Africa.