Elemental Composition of the Ultrafine Fraction of Road Dust in the Vicinity of Motorways and Expressways in Poland – Asphalt Versus Concrete Surfaces

Abstract

Air pollution in the vicinity of roads is a complex and growing problem. In urbanised areas, there are many sources of dust emissions, but one of the main ones is road traffic. Investigating and assessing the physical and chemical properties of road dust and, more specifically, dust collected from surface courses is one way of providing an opportunity not only to identify the contribution of the emitters concerned to the formation of dust air pollution in the vicinity of roads but above all the environmental risks associated with traffic emissions. The study aimed to analyse the elemental composition of dust with a fraction <0.1 mm, collected from asphalt and concrete roads characterised by the highest technical and service parameters in Poland. The samples were analysed using a Shimadzu EDX 7000 energy-dispersive X-ray fluorescence spectrometer, then the results were statistically analysed using the t-Welch test, and the enrichment factors EF were determined. It was shown that road dust with a grain size of less than 0.1 mm collected from asphalt surface course was extremely highly enriched in Cu, Cr, Pb and S, while that from the concrete surface course was enriched in Zn and Zr, indicating a strong anthropogenic origin of these elements; exhaust gases were identified as their source. Irrespective of the type of surface course, very high dust enrichment occurs for Ca, Mn, Ni, S, Ti and Y. These elements may originate from the abrasion process of vehicle tyres. For road dust collected from both road types, the most similar EF values were found for Fe, K, Mn, Si, Sr and Ti. The source of these elements is most likely the roadside soil. It follows that the type of road surface is not the main determinant of the composition of road dust with a fraction <0.1 mm.