Aerosol Particle Sources Affecting the Swedish Air Quality at Urban and Rural Level

Abstract: During the last decades anthropogenic aerosol particles have attracted much attention due to their adverse health effects and their influence of climate change, and in Sweden, there are mainly three aerosol sources that affect the air quality; domestic wood combustion, traffic, and long distance transport, which includes new particle formation. This work concerns the characterization of these sources and an estimate of how much they contribute to the aerosol particle number (ToN) and mass concentrations (PM) in Swedish cities and at background locations. The aims have been achieved with the help of extensive measurement campaigns, characterizing emissions from the sources and with measurements and modelling at receptor points, where people are exposed to the particle pollution. The most important outcomes of these studies show that, in urban areas both traffic and domestic wood combustion are very important sources of high levels of ToN and PM. It is especially during cold days in northern Sweden that domestic wood combustion is an important source of particles. Both trucks and personal cars are contributing significantly to the particle emissions of ToN and PM. However, exhaust particles mainly affect ToN, whereas most of the PM2.5 and PM10 (total particle mass below 2.5 and 10 ?m diameter respectively) emissions come from road dust generated by the moving vehicles. At locations in large cities, in southern Scandinavia further away from the traffic (urban background), the long distance transported fraction is beginning to dominate contributions to PM10, and it has both natural and anthropogenic sources. The exhaust emissions from traffic can on the other hand make a significant contribution to increased levels of ToN even at distances about 50 km away from the urban area. New particle formation, which is observed more than 1/3 of the days in southern Sweden, can both come from clean as well as more polluted air masses. However, the formation in polluted air has half the impact on ToN that cleaner air has.