Distribution of Vehicular Lead in Roadside Soils of Major Roads of Brisbane, Australia

Abstract

Collections were made from three sites in the urbanarea of Brisbane, Australia. At each site, soilsamples were collected from transects parallel andperpendicular to the roadway, as well as a depthprofile. Total lead was determined by refluxing thesamples with concentrated nitric acid (1 h) andorganic lead by shaking with cold ammoniacal methanol(Flameless AAS). Both chloride and bromide anionswere obtained from an aqueous extract (HPLC). Resultsshowed that vehicular emissions were the major sourceof lead in the roadside soils of this study. At siteslocated in relatively enclosed areas of higheratmospheric stability, both lead and bromide contentsdecreased markedly with increasing distance from theroadway. However, in the absence of such atmosphericstability, the distribution of both lead and bromidecontents revealed different patterns which wasattributed mainly to the effect of meteorologicalfactors such as wind direction and speed. The depthprofile of roadside soils generally showed leadaccumulation within the uppermost 5 cm, whereaselevated concentrations of bromide were observed at greater depth.