J Aerosol Scl. Vol. 3 I, Suppl. I, pp. $891 $892,2000 Pergamon www.etsevier.corn/locate/j aerosci Poster Session II. Source apportionment and emissions Source Apportionment of PM10 in Switzerland by Application of a Multivariate Receptor Model C. HUEGLIN 1, W. DEVOS 1, R. GEHRIG l , P. HOFER l, J. KOBLER I , W. A. STAHEL 2, M. WOLBERS e, U. BALTENSPERGER 3, and C. MONN 4 Swiss Federal Laboratories for Materials Testing and Research (EMPA), CH-8600 Dtibendorf, Switzerland 2 Seminar for Statistics, ETH Zurich, CH-8092 Zurich, Switzerland 3 Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland 4 Institute for Hygiene and Applied Physiology, ETH Zurich, CH-8092 Zurich, Switzerland Keywords: PM~o, source apportionment, receptor model INTRODUCTION A quantitative understanding of source contributions to ambient PM~o levels is needed to develop emission control strategies and to predict the trend of future PMl0. In this work, the receptor modelling approach was applied to identify the main sources of PM~o and to quantify their contributions at locations which are representative for typical air pollution levels in Switzerland (source apportionment). METHODS Receptor models require knowledge of the chemical composition of atmospheric particles at a certain measuring site (receptor), i.e. the concentrations of a large number of chemical constituents in a sufficient number of samples are needed. All receptor models are based on the assumption of mass conservation. However, there are two different realisations of this approach: chemical mass balance (CMB) and multivariate receptor models (Hopke 1991). In addition to data on the chemical composition of atmospheric particles at the receptor, the chemical mass balance uses quantitative information of the chemical composition of PM,0 emitted by the sources (source profiles) to solve the mass balance equation. In contrast, multivariate receptor models need only chemical composition data of atmospheric particles at the receptor to estimate both, the source profiles and the source contribution. Daily samples of PM~o from four different sites were taken on quartz fiber filters (high-volume sampler). Filter samples from every 4 th day between February 1998 and March 1999 were analyzed for total mass, trace elements, water soluble ions, elemental carbon, and organic carbon (120 filter samples per site). The data sets were analysed by means of multivariate receptor modelling. Receptor models cannot properly address the secondary aerosol. Therefore, only the primary PM~o fraction was modelled. The source contributions to secondary PM~0 were assessed by combined evaluation of transboundary import export budgets (EMEP 1998) and an emission inventory of the precursors (Corinair 1990). RESULTS Six sources (or source categories) which explain most of the primary PMlo were identified at the urban and suburban sites in Zurich, Bern, and Basel. The obtained source patterns at the different sites are quite similar. At a rural and elevated site (Chaumont), only four source categories could be resolved. Because of the low PMt0 concentrations at this site, the concentrations of various chemical species which are rather specific for certain emission sources were often below the detection limit of the applied analytical methods. As a consequence, the ability to resolve source impacts was much lower at the Chaumont site. Road traffic was found to be a major source for primary PM~o in Switzerland. Three factors were extracted which are attributed to different types of road traffic emissions: exhaust emissions, emissions of resuspended road dust, and resuspension of road salt during winter season. Other identified sources are resuspendend mineral dust, and a source which is responsible for most of the thallium emissions (presumably cement fabrication). Finally, a source category was found which includes emissions from combustion of biomass (wood and agricultural waste), waste incineration, long range transport of primary particles and possibly other minor emission sources. Figure 1 shows the annual mean contribution of the identified sources at the urban sites in Bern (PM~o=39.61.tg/m 3, the site is next to a main road) and Zurich (PMio=24.51,tg/m3, the site is in a large court yard), as well as at the suburban site $891