Changes in soil and leaf trace element concentrations: a study in Naples city centre.

The spatial and temporal changes of trace element concentrations in leaves and soils of an urban area were investigated simultaneously. For this purpose, in May and September 2001 and in January and May 2002, samples of Quercus ilex leaves and surrounding soils were taken at 5 sites in central Naples and on Mt. Vesuvius, a remote area, as control. The contents of Cd, Cr, Cu, Fe, Mn, Pb, V and Zn were analysed in both matrices by atomic absorption spectrometry. The urban sites in Naples showed different spatial trends of contamination depending on each element. The highest leaf concentrations of Cr, Cu, Fe, Pb, V and Zn were measured at the sites affected by a high traffic flow. The highest Cd, Cu, Pb and Zn soil concentrations were measured at different urban sites. The remote soil showed the highest values of Cr and V. The significant correlations between Pb and Zn in each matrix and between leaf and soil Pb and Zn concentrations suggest a common origin and an influence of wet and dry airborne deposition upon foliage and soils. Cd, Pb and Zn concentrations decreased and Cr increased from May 2001 to May 2002 in both matrices. The season and sampling period do not seem to affect trace element concentrations of Q. ilex mature leaves.