Impact of metal accumulation on Quercus ilex L. leaf traits

Aims: The aims of this research were: i) to compare Cr, Cu, Ni and Pb concentrations in Quercus ilex L. leaves collected at urban/industrial and urban areas; ii) to investigate the main pathway of leaf metal accumulation; iii) to evaluate probable differences in traits of leaves at the investigated area typologies; iv) to relate leaf metal concentrations and to leaf traits. Methods: Leaves and soils were collected at six sites (three of urban area and three of urban/industrial area). Length, width, area, extract pH, relative water content, specific area and petiole length were evaluated in the leaves; besides, Cr, Cu, Ni and Pb concentrations were measured in unwashed and chloroform washed leaves, and in soils. Results: The comparison between leaves collected at the urban and urban/industrial area showed that higher Cr, Ni and Pb concentrations were measured at the urban/industrial area, greater leaves and longer petiole were observed at the urban area, whereas higher leaf extract pH were observed at the urban/industrial one. Air uptake seemed to be the main pathway of leaf metal accumulation, as soils were not metal contaminated. Conclusions: Q. ilex leaves highlighted a diffuse and conspicuous air metal pollution in both urban/industrial and urban areas, although differences between the site typologies were observed. In fact, leaves of the urban/industrial area showed higher inner concentrations of all the investigated metals, with the exception of Cu. A direct leaf uptake by the air can be supposed, as the soils were scarcely metal contaminated. Greater leaves and longer petiole, among the investigated leaf traits, appeared the main leaf responses to metal accumulation.