Author(s)

K. –G. Westerlund & C. Johansson

Abstract

Emissions of metals and particulate matter due to wear of brake linings in Stockholm K. G. Westerlund1& C. Johansson1, 2 1 Stockholm Environment and Health Protection Administration, Sweden 2 Stockholm university, Air Pollution Laboratory, Sweden Abstract The total wear of brake linings have been estimated using the total yearly amount of transports and communication for different vehicle types and estimated annual consumption of linings. In order to calculate heavy metal emissions the metal content of different brake linings were analysed. Analyses were performed using plasma - emission spectrometry. This allowed the detection of copper, zinc, chromium, nickel, cadmium and lead. Emission factors for copper and lead were 1,300 and 190 pg per vehicle km. These values are 9 and 5 times higher, respectively, than measured in road traffic tunnels, indicating that less than 20% of the brake wear is airborne. The calculated total particle emission per vehicle kilometre due to wear of brake linings was 17 mg and 84 mg for passenger cars and heavy-duty vehicles, respectively. If all would be airborne, the particle wear of passenger cars would be comparable to the particle emission in car exhaust of gasoline cars. Diesel passenger exhaust emission is about 10 times higher, making brake wear emission comparatively small. For heavy-duty goods vehicles the emission due to the wear of brake linings is about 60% of that from due to exhaust. The estimate given here for Stockholm is somewhat higher compared to that given by US-EPA of 8 mg per vehicle kilometre for passenger cars‘. As exhaust emissions decrease in the future due to renewal of the vehicle fleet and cleaner fuels, emissions from brake linings may not change and therefore become relatively more important as a source of PM in urban areas. Compared to other sources, wear of brake linings may be a significant source of copper and lead.

Keywords