Emissions of fine particles, NOx, and CO from on-road vehicles in Finland

Real-time particle number size distributions and NO, NO2, NOx, CO, and CO2 concentrations were measured with a mobile laboratory van in October 2003 on the streets and highways of the Helsinki metropolitan area, Finland. A bimodal particle size distribution was observed with about 85% of the particles being smaller than 29 nm. Real-time fuel-based emission factors for size-resolved particle numbers, CO, and NOx were determined. Wide distributions of emission factors were obtained for all pollutants. In addition, PM2.5 samples were collected and the elemental compositions were analysed. Relative to fixed site urban PM2.5, street air PM2.5 concentrations of Cu, BC, Fe, and Zn were elevated. Weather and road conditions influenced PM concentrations more than the differences between the city and highway traffic environments.