Monitoring of trace elements and PAHs: a combined approach using native bioaccumulators (holm oak leaves and mosses) to detect pollution gradients

In urban environments, high levels of pollutants, as polycyclic aromatic hydrocarbons (PAHs) and trace elements, coming mainly from anthropogenic sources as vehicular exhausts, industrial emissions and waste incineration, impose serious environmental and biological problems. These pollutants cause concern, especially for their potential toxicity and the adverse health effects. In this work the results of a passive biomonitoring study, concerning the accumulation of trace elements and PAHs in Quercus ilex leaves and in the epiphytic moss Leptodon smithii, are presented. Both biomonitors were sampled in two Italian Regions (Campania and Toscana) along a gradient of environmental disturbance in i) urban, ii) periurban and iii) extraurban areas. Fresh leaves and mosses were extracted by sonication in a mix of methane dichloride and acetone (1:1=v:v) and analysed for 16 EPA PAHs by GC-MS. Oven-dried (75 °C) plant samples were mineralized with acids (HF:HNO3=1:2=v:v) and analysed for elements (Al, B, Ba, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, V and Zn) by AAS and ICP-OES. In both Regions, trace element and PAH concentrations were generally higher in leaves and mosses sampled in urban areas than in periurban and extraurban ones, confirming the suitability of the selected native species to monitor air pollutants in the Mediterranean areas. The high concentrations of some elements in leaves (Mn, Na and Zn) and in mosses (B, Ba, Cd, Mn, Ni and V) from the extraurban site of Toscana, likely due to the influence of marine aerosols and of an industrial settlement located about 40 Km from the sampled area, put in evidence the importance of selecting suitable “reference” sites in order to find out situations at risk and properly evaluate the degree of pollution in urban areas.