Temporal and spatial variation in C, N, S and trace element contents in the leaves of Quercus ilex within the urban area of Naples

This paper presents a comparative analysis of the concentrations of C, N an d S and several trace elements (Fe, Mn, Na, Zn, Cu, V, Pb, Ni, Cr, Cd) in l eaves of Quercus ilex, an evergreen oak, collected in the urban area of Nap les in 1989 and 1996. The samplings were carried out from 25 urban sites (r oads with different traffic flows as well as urban and suburban parks) and from two remote areas as controls. Relative to 1989, the values measured in 1996 denote a strong decrement of S, Fe, Na, Pb, and Cr, with the exceptio n of S in control sites. By contrast, C, N and Cd contents were higher in 1 996 than in 1989. Cu and Ni showed a conspicuous increment in control sites as well as in urban sites facing the sea and in the parks, while in all th e other urban sites these elements decreased remarkably. No significant dif ference was found in the leaf contents of Mn, Zn and V measured in 1989 rel ative to 1996. Both in 1989 and 1996 the contents of N, S, Fe, Na, Cu, Pb, V, Ni, Cr and Cd were significantly higher in leaves from urban sites than in the controls, reflecting the high degree of contamination of the urban a rea. Concentration factors expressed as the ratio of road/control values fo r most of the elements were still very high in leaves collected in 1996, th ough remarkably lower than in 1989. (C) 2000 Elsevier Science Ltd. All righ ts reserved.