Heavy metals, pahs contents and ecophysiological changes in leaves of holm-oak inurban area of Caserta (Italy)

Human health as well as that of animals and plants is severely affected by air pollution. In urban areas the vehicular traffic, in particular, contributes to the release of contaminants like heavy metals and polycyclic aromatic hydrocarbons (PAHs). Plants are effective biomonitors because, through their large leaf surface area, intercept and also absorb air pollutants, that can cause morphological, physiological and biochemical responses. In this interdisciplinary study the concentration of airborne contaminants were correlated with plant metabolites in leaves of holm-oak (Quercus ilex L.). This species, a typical sclerophyllous evergreen broadleaf plant widely distributed in the Mediterranean Basin, has been used as biomonitor being an ornamental plant in parks, gardens and avenues of the city of Caserta. The concentrations of V, Cd, Cr, Pb, Ni, Cu, PAHs as well as chlorophyll contents and peroxidase activity in one year old leaves from different sites of the urban area were determined. The contents of leaf free amino acids were also measured in order to identify new indicators that could be useful to monitor air quality even at relatively low level of pollutants. The tested sites showed different contents of heavy metals and PAHs, in particular cancerogenic PAHs, as well as different amino acid patterns. Negative correlations were found between Cu and Cd contents and the peroxidase activity and between these metals and some amino acid concentrations. No relationships, instead, were found between the PAHs and heavy metal contents. All data were tested by multivariate analysis. The Principal Component Analysis (PCA), evidenced a clear grouping of the sites