Fractionation and mobility of Cu, Fe, Mn, Pb and Zn in the road dust retained on noise barriers along expressway - A potential tool for determining the effects of driving conditions on speciation of emitted particulate metals

Road dust (RD) retained on noise barriers was used as a monitor of emission of traffic-related metals from expressway. By using SEM/EDX analysis it has been revealed that the main components of this particulate were irregular fine aggregates and tire debris with a ragged porous structure and with inclusions derived from the road surface. The results of chemical fractionation showed that driving conditions influence strongly a distribution pattern of Cu, whereas the atmospheric corrosion process affects a distribution pattern of Zn. The distribution pattern of Cu originating only from vehicle braking emission was isolated from the distribution pattern of road traffic copper. The predicted comparative mobilities of the emitted metals form the order: Zn >> Cu approximate to Mn > Pb >> Fe. The high mobility of zinc (K = 0.61) may create a current inhalation hazard and may be a source of future environmental hazard in the areas adjacent to heavily trafficked roads. (C) 2014 Published by Elsevier Ltd.