Size distribution of airborne particulate matter and associated heavy metals in the roadside environment.

Abstract The size distributions of airborne particulate matter (PM) and associated heavy metals Pb, Cd, Ni, Cr, V, Mn, Cu and Fe in different inhalable fractions ( 6.7 μm) were determined at a traffic-orientated urban site in the city of Thessaloniki, northern Greece. The airborne PM displayed a bimodal distribution with most of the mass (52%) contained in the submicron size range ( 6.7 μm). Characteristic size distributions of heavy metals allowed identification of three main behavioral types: (a) metals whose mass was resided mainly within the accumulation mode (Pb, Cd), (b) those which were distributed between fine, intermediate and coarse modes (Ni, Cu, Mn), and (c) those which were mainly found within particles larger than 2.7 μm in diameter (Fe). The mean mass median aerodynamic diameter (MMAD) of PM was found at 0.85 ± 0.71 μm, while the mean MMADs of heavy metals followed the order Pb (0.96 ± 0.71 μm)