Grain-size distribution and heavy metal contamination of road dusts in urban parks and squares in Changchun, China

Due to rapid urbanization and the scarcity of land, most of the urban parks and squares in cities are built close to major roads or industrial areas, where they are subject to many potential pollution sources, including vehicle exhaust and industrial emissions. The aims of this study were to determine the concentrations of selected metals (Pb, Cr, Cu, Ni, Zn, and Cd) in road dusts collected in urban parks and squares in Changchun, China, on June 1, 2013 (International Children's Day) and to estimate the pollution sources. The mean Pb, Cr, Cu, Ni, Zn, and Cd contents (70.89, 60.30, 43.56, 23.16, 170.80, and 0.3111 mg kg(-1) dry weight, respectively) in urban dusts were higher than their corresponding natural background values, particularly Pb, Cu, Zn, and Cd, which had about 2.5, 1.4, 1.9, and 2.6-fold higher levels, respectively. The results of principal component analysis indicated that Cr and Ni concentrations were mainly of natural origin, while Pb, Cu and Zn were derived from anthropogenic activities, and Cd tended to be from both sources. The geoaccumulation index (I-geo) of these metals in the urban dusts under study indicates that they are uncontaminated with Cr and Ni; uncontaminated to moderately contaminated with Cu and Zn; and moderately contaminated with Pb and Cd. In addition, five particle sizes were analyzed separately for heavy metal concentrations. In all studied areas, there are large differences in the metal-loading percentage of different particle-size fractions among the samples, and the particles in 250-2,000-mu m fraction are dominant in the total metal loading.