Partitioning of Lead in Urban Street Dust Based on the Particle Size Distribution and Chemical Environments

The objective of the present study was to investigate the distribution of lead among the physical fractions and between the various chemical forms of urban street dust. In order to achieve this aim, street dust samples were collected from three major roads with high traffic volume and one minor road with a low traffic density in urban areas of Az Zarqa City, Jordan. The dust samples (N = 6 for each site) were split into two portions. One part was employed for physical size fractionation and the other portion for chemical and physical analyses. A sequential extraction procedure was used to determine Pb associated with various chemical and physical fractions. It was found that about half of the lead was associated with the carbonate fraction and Fe-Mn oxides were ranked second, followed by the exchangeable and organic fractions. A general trend of increasing lead levels with decreasing particle size in street dust was observed. The current study showed that leaded gasoline was the major source for the elevated lead levels in street dust. Therefore, for those countries still employing leaded gasoline, such as Jordan, substantial reductions in lead contamination of street dust and roadside soils could be achieved by prohibiting the use of Pb additives. Consequently, many health benefits could be expected for the entire population and especially for children. The accuracy of lead results was checked by periodic analysis of SRM Soil 7. Observed concentrations were within 5% of certified value in analyzed SRM for lead.