Platinum group element distribution in the soils from urban areas of the Campania region (Italy)

Abstract

This paper represents a detailed study to assess the platinum group element (PGE) content of topsoils from urban areas in the Campania region (Italy), following on from previous work. Samples were collected from residual and non-residual soils from flowerbeds in the urban areas of Avellino, Benevento and Caserta (characterized by low population density, LPD), and in Salerno (a city with high population and high automobile traffic densities). The soils (<100-mesh size fraction, i.e. <150 μm) were analysed for Pt, Pd and Rh by fire assay ICP-MS and for 37 other elements by ICP-AES and ICP-MS after a modified aqua regia digestion. In LPD cities, PGE concentrations were close to background values (with the exception of the industrial areas), but Salerno proved to be contaminated by PGEs. Platinum, Pd and Rh concentrations are in the <0.1–278, <0.5–432 and 0.07–47 ppb range, respectively. Moreover, a high correlation among Pt, Pd and Rh (R=0.98), and between PGEs and other typical traffic-emitted metals such as Cr, Cu, Sb and Sn has been detected only in Salerno. Finally, the statistical analysis pointed out a lower background for PGEs in soils formed on sedimentary rocks (in the eastern sector of Caserta, in Benevento and Salerno) compared to those formed on volcanic rocks (Avellino and the western area of Caserta).