Glass microspheres in road dust of the city of Kielce (south-central Poland) as markers of traffic-related pollution.

Glass microspheres are widely used as reflective components in road and pavement marking materials. They commonly occur in road dust mixed with different particles of anthropogenic and geogenic origin. This paper describes different methods that enable discrimination of glass microspheres from other morphologically similar particles that occur in road dust of Kielce. The individual glass microspheres vary from 30 to 1350 µm in diameter and consist of recycled Ca-, Na-, Mg-silica glass with a minor admixture of Al, Fe, K and S. Because of their stability and chemical composition, glass microspheres are good markers of traffic-related pollution in different environmental archives. Of different elements present in Kielce road dust, the fraction < 0.125 mm was distinctly abundant in zirconium, the main constituent of disk brakes or brake pads and a potential marker of road traffic pollution. However, the statistically significant positive correlation of the Si-Zr pair (R = 0.54) in the 1.0-2.0 mm fraction is linked to the presence of some detritic quartz grains with zircon inclusions. The other metals determined provide ambiguous traffic-related signatures and may be derived from different pollution sources.