The Chemical Speciation of Trace-Metals in Street Dusts of Irbid, Jordan

Street dust samples were collected from different locations in Irbid city, Jordan. The concentrations of Pb, Cu, Zn, Cd, Ni, Mn, Cr and Al in these samples were determined usingInductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) after chemical fractionation according to the modified Community Bureau of Reference (BCR) sequential extraction procedure. The street dusts were sequentially extracted into three operationally defined fractions; exchangeable and bound to carbonates, bound to Fe-Mn oxides and residual.The order of bioavailability of measured elements (exchangeable and bound to carbonates) isfound to follow the order: Zn Cu Mn Cd Pb Ni Cr Al. However, the relative abundance of the metals in mobile phases of the samples based on the sum of acid- extractable and oxidizable fractions are in the following sequence: Pb (96.2%) Mn (92.9%) Zn (77.2%) Cu (76.3%) Cd (65.7%) Ni (44.5%) Cr (33.4%) Al (28.4%). Enrichment factor calculations indicated that Zn, Cu, Pb and Cd are highly enriched (EF values 100), which indicates a widespread contamination of these elements by human sources. However,enrichments of other elements were moderate and show large variability. The highest EF values for Cr and Ni are found in the residential areas followed by the main roads.