Road dust and run-off

3 Road dust and run-off. Roads are a potentially important source of environmental contamination. Concerns include NO, PAHs and organo-lead from exhaust emission, and a variety of heavy metals associated with vehicle manufacture and use. 

Copper, lead, cadmium and zinc have been found predominantly in potentially mobile forms by sequential extraction of material collected during road cleaning (Colandini et al, 1995). Cadmium and zinc were found to be more labile than lead and copper. A study of street dust and gully pot sediments confirmed this order of potential availability (Striebel and Gruber, 1997) and also suggested that lead levels in material of the types studied had decreased since the introduction of unleaded fuel in Germany. Lead has also been studied in street dusts from Brisbane, Australia. The element was found mainly in the carbonate phase and in the smaller particle size fraction (Al-Chalabi and Hawker, 1996) except where resuspension caused particle aggregation. 

The impact of heavy metals from highways on adjacent soils and receiving waters has also been investigated by sequential extraction (Stone and Marsalek, 1996). Airborne dust, at least partly derived from motorways, was found to be a significant source of soil contamination in two satellite cities of Seoul, South Korea (Chon et al., 1998). A comparison between roadside soil and sediment from 

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