Impact of automobile emissions on the levels of platinum and lead in Accra, Ghana

Abstract

Examination of car fleet records in Accra demonstrates an increasing proportion of catalytic converter-equipped cars in the relatively old car fleet (average age 13 years) due to their import from developed countries. However, only leaded petrol is sold in Ghana. Lead anti-knocking additives, which are known to affect catalyst activity and promote thermal sintering and mechanical abrasion, may increase Pt emissions. This possible synergism prompted the concomitant determination of Pb and Pt levels in road dust and roadside soils in Ghana. Both metals followed traffic density with higher concentrations in urban areas compared to remote sites. In urban areas, the range for Pb (365 ± 93 µg g⁻¹ for dust and 291 ± 76 µg g⁻¹ for soil) reflects pre-catalyst levels in Europe and the US, while the range for Pt (39 ± 24 ng g⁻¹ for dust and 15 ± 5.3 ng g⁻¹ for soil) is typical for the same countries. The elevated Pt concentrations were unexpected due to recent introduction of catalysts to Ghana compared to the prolonged use of catalysts in Europe and the US.