Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 7 2 2007 10.5194/acpd-7-4001-2007 http://www.atmos-chem-phys-discuss.net/7/4001/2007/ http://www.atmos-chem-phys-discuss.net/7/4001/2007/acpd-7-4001-2007.html http://www.atmos-chem-phys-discuss.net/7/4001/2007/acpd-7-4001-2007.pdf 4001 4034 2007-03-23 Evaluation and modeling of the size fractionated aerosol number concentration measurements near a major road in Helsinki T. Hussein tareq.hussein@helsinki.fi J. Kukkonen H. Korhonen M. Pohjola L. Pirjola D. Wraith J. Härkönen K. Teinilä I. K. Koponen A. Karppinen R. Hillamo M. Kulmala University of Helsinki, Department of Physical Sciences, Finland Stockholm University, Department of Applied Environmental Science, Sweden Finnish Meteorological Institute, Air Quality Research, Finland Institute for Atmospheric Science, School of Earth and Environment, University of Leeds, UK Helsinki Polytechnic, Department of Technology, Finland School of Mathematical Science, Queensland University of Technology, Brisbane, Australia Department of Chemistry, University of Copenhagen, Denmark This study presents an evaluation and modeling of the size fractionated aerosol number concentrations that were measured near a major road of Itäväylä in Helsinki, during 23 August – 19 September 2003 and 14 January – 11 February 2004. The measurement system contained also electronic traffic counts, on-site meteorological measurements, and urban background concentration measurements. We have evaluated the temporal variations and the dependencies on local meteorological conditions of the measured aerosol number concentrations and size distributions. The ultrafine particle (UFP) number concentrations at the roadside site were approximately an order of magnitude higher than those at the urban background site during daytime, due to vehicular emissions from the road. We also determined the statistical correlations of the sequential time series of the particle number size distributions at the roadside site, and the traffic densities. The computed Pearson correlation coefficients for the downwind cases were substantially high for UFP's (>0.6), and low for accumulation mode particles; the latter is due to the substantial contribution of long-range transported particles in that size range. 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