Distribution of vehicular lead in roadside soils of major roads of Brisbane, Australia

Collections were made from three sites in the urban area of Brisbane, Australia. At each site, soil samples were collected from transects parallel and perpendicular to the roadway, as well as a depth profile. Total lead was determined by refluxing the samples with concentrated nitric acid (1 h) and organic lead by shaking with cold ammoniacal methanol (Flameless AAS). Both chloride and bromide anions were obtained from an aqueous extract (HPLC). Results showed that vehicular emissions were the major source of lead in the roadside soils of this study. At sites located in relatively enclosed areas of higher atmospheric stability, both lead and bromide contents decreased markedly with increasing distance from the roadway. However, in the absence of such atmospheric stability, the distribution of both lead and bromide contents revealed different patterns which was attributed mainly to the effect of meteorological factors such as wind direction and speed. The depth profile of roadside soils generally showed lead accumulation within the uppermost 5 cm, whereas elevated concentrations of bromide were observed at greater depth.