Long-term dynamics of soil metal concentrations at the urban area of Naples (Sourthern Italy).

Metals constitute a risk to human and environment health. Metals in urban soils derive from natural and anthropogenic sources, and their concentrations may differ over time depending on quantity and quality of emission sources. The aim of the work was to evaluate, over a period of 15 years from 1993 to 2008, differences in metal (Cr, Cu, Fe, Mn, Ni, Pb and Zn) concentrations in soils collected at the urban area of Naples (Southern Italy). Other goal was to individuate the origin (natural and anthropogenic) of the detected metals in the soils and for this aim, three indices were calculated: contamination factor, ecological risk factor, and geo-accumulation index. The results highlighted an overall decrease of metal concentrations from the beginning to the end of the study period, even if Pb concentrations in 2008 were still 2-fold higher than the threshold value fixed by the Italian law. Cr, Cu, Pb and Zn in the soils mainly derive from anthropogenic activity, as highlighted by the comparison with the baseline values. The indices suggest a moderate contamination degree but a low potential ecological risk of the investigated soils.