TIRE-TREAD AND BITUMEN PARTICLE CONCENTRATIONS IN AEROSOL AND SOIL SAMPLES

ABSTRACT

Tire and bitumen particle concentrations are determined in aerosol and soil samples. They each constitute about 5 wt-% of the total suspended particulate matter (TSP) in inner city air, collected with a Berner low pressure impactor, 5 m from a road. The particle size distribution shows that 92% of the mass of airborne particulate tire debris have aerodynamic diameters smaller than 1 µm. The mean aerodynamic diameter is about 1 µm for the bitumen particles. This size range enables the possibility for far range transport and inhalation by humans. Soil concentrations in the vicinity of a highway indicate an approximate exponential decrease with increasing distance from the road. Constant values are reached after about 5 m for the tire particles and 10 m for the bitumen particles. Concentrations in soil that has not been touched for at least 30 years show a decrease in tire concentration by a factor of 30 when moving from the top soil to a depth of 3 cm. The bitumen concentration is approximately constant to a depth of 10 cm.

ACKNOWLEDGEMENTS

We would like to thank Senior Scientist Kaare Kemp, National Environmental Research Institute, for supplying aerosol filters and PIXE-data. Senior Scientist Jørgen Bilde-Sørensen, Risø, for assistance with the scanning electron microscope.