Inorganic geochemistry of roadway dust from the metropolitan area of Palermo, Italy

Inorganic matter from roadway dust collected in the urban area of Palermo, Italy, was analysed to identify the chemical elements introduced into the environment as a result of human activities. Metals of environmental concern exhibit very high enrichment factors, which in some cases exceed 100. Metal size distribution indicates that Pd, Pt, Au, Sb, Zn, S, Ni, V, Mo and Cr substantially accumulate in the finest particles, whereas Pb, Br, As, Cu, Ag and Ba are almost independent of the size fraction. SEM/EDS analyses revealed that some individual particles contain clusters of foreign particles (<10 mum) made up of Fe-Ni, Cr-Ni or Fe alone, typical of the abrasion of stainless steel. Others are aggregates of smaller Pb-Br-Cl particles. Lead isotope composition indicates that Pb pollution is mainly due, to automobile exhausts and industrial sources. Pt and Pd concentrations reveal the increasing release of these elements into the environment from catalytic converters. Data indicate that monitoring Total Solid Particles, as generally done by the municipal agencies for the environment, is inadequate from a sanitary point of view, while there is a need for more attention to the presence of trace elements in airborne particulate matter and their distribution as a function of particle size.