Atmospheric Environment 38 (2004) 3935–3948 Case study analysis of PM burden at an urban and a rural site during the AUPHEP project B. Gomiscek a, *, A. Frank b , H. Puxbaum c , S. Stopper a , O. Preining a , H. Hauck a,d a Clean Air Commission, Austrian Academy of Sciences, Postgasse 7-9, Vienna, Austria b Institute of Meteorology and Physics, University of Natural Resources and Applied Life Sciences, Vienna, Austria c Institute for Chemical Technologies and Analytics, Vienna University of Technology, Vienna, Austria d Institute of Environmental Health, Medical University of Vienna, Kinderspitalgasse 15, Vienna, Austria Received 28 July 2003; received in revised form 25 February 2004; accepted 3 March 2004 Abstract On several days during the 1 year measurement period the 24h average EU concentration limit for PM 10 of 50 mg m 3 was exceeded at the urban site AUPHEP1 as well as at the rural site AUPHEP2. The exceedances occurred generally during the winter half-year, however, during the summer period the elevated values were recorded as well. At the urban site several days with concentrations above 70 mgm 3 were observed. The highest 24-h concentration reached 130 mgm 3 on 1 January 2000. Regional transport processes of polluted air mass were the influencing factor for the elevated PM burden at both sites, however, the rural site was often additionally polluted by the Vienna metropolitan area. The high pollution events generally occurred under weather condition with prevailing SE–SW air flow. The chemical composition of the PM fractions during ‘‘high PM’’ was clearly different than that during the days with ‘‘low PM’’ burden. The chemical composition obviously reflects different source regions, paths of the air masses as well as weather patterns. r 2004 Elsevier Ltd. All rights reserved. Keywords: PM 2.5 ; PM 10 ; Trajectory analyses; Air mass transport; Chemical composition of PM 1. Introduction A twin-site measurement design comprising a rural site situated in a zone of influence of the Vienna metropolitan area and an urban site gives the opportu- nity to study mutual dependence of the processes on the regional scale as well as the impact of the urban area on the meso-scale scale. PM 1 , PM 2.5 as well as PM 10 particles are small enough to remain suspended for some hours or days and they can travel considerable distances from the source. The highest concentrations of PM generally occur in urban and industrialized areas, but even there, the contribution of long-range transport can be significant—concentrations of primary PM 10 can become elevated in episodic situations, when long-range transport of particulates of man-made or natural sources could,onitsown,exceedtheshort-termEUstandard(50 mgm 3 )(ApSimon et al., 2001; Artinano et al., 2001). In order to fulfill EU requirements (European Directive 99/ 30/EC) knowledge of the contributions from different sources, including the air mass transport processes on variousscales,ofprimaryaswellasofsecondaryPMhas gained importance. Even in large cities, such as Berlin, London and Detroit aerosol transport has been shown to contribute significantly to elevated levels of PM 10 (Blanchard et al., 1999; Lenschow et al., 2001; Smith et al., 2001; Wolff et al., 1985). ARTICLE IN PRESS *Corresponding author. Tel.: +386-4-2374-252; fax: +386- 4-2374-299. E-mail address: bostjan.gomiscek@fov.uni-mb.si (B. Gomiscek). 1352-2310/$-see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2004.03.033