Abstract
It is well known that automobiles, especially diesel vehicles, are an important source of fine particulate matter (PM2.5) in urban environments. Particles emitted directly by cars consist of organic and elemental carbon, and to a lesser extent of sulfate and various trace elements. Automobiles cause also emissions not related to the engine or the exhaust system, such as the road dust elevated by moving vehicles and the tyre wear. These indirect emissions, although made mainly of larger particles, are also able to contribute to urban PM2.5.
In this presentation, we will discuss automotive sources of fine particles from an atmospheric perspective. This is done by presenting ambient measurement data on different particle properties and from different distances from major traffic lines. It will be demonstrated that automobile are one but not the only important source of fine particulate matter in urban environments. The role of automobiles relative to other sources is shown to depend crucially on which particle properties we are interested in. In this respect, a clear distinction has to be made between the following parameters: PM10, PM2.5, PM0.1 (ultrafine particulate matter), the total particle number concentration, the ultrafine particle number concentration, and the concentration of various chemical components in the particulate matter. We will also demonstrate the importance of different temporal and spacial scales involved, since it is clear that automotive emissions peak during the rush hours and close to traffic lines. Other related issues, such as outdoor-to-indoor transportation of particulate matter, will also be discussed.