Articles | Volume 15, issue 17
Atmos. Chem. Phys., 15, 10219–10237, 2015

Special issue: Megapoli-Paris 2009/2010 campaign

Atmos. Chem. Phys., 15, 10219–10237, 2015

Research article 15 Sep 2015

Research article | 15 Sep 2015

In situ formation and spatial variability of particle number concentration in a European megacity

M. Pikridas1,2,3, J. Sciare3,4, F. Freutel5, S. Crumeyrolle6,a, S.-L. von der Weiden-Reinmüller5, A. Borbon7, A. Schwarzenboeck6, M. Merkel8, M. Crippa9, E. Kostenidou1,2, M. Psichoudaki1,2, L. Hildebrandt10, G. J. Engelhart10, T. Petäjä11, A. S. H. Prévôt9, F. Drewnick5, U. Baltensperger9, A. Wiedensohler8, M. Kulmala11, M. Beekmann7, and S. N. Pandis1,2,10 M. Pikridas et al.
  • 1Department of Chemical Engineering, University of Patras, Patras, Greece
  • 2Institute of Chemical Engineering Sciences (ICEHT), FORTH, Patras, Greece
  • 3The Cyprus Institute, Environment Energy and Water Research Center, Nicosia, Cyprus
  • 4Laboratoire des Sciences du Climat et de l'Environnement (LSCE), Gif-sur-Yvette, France
  • 5Max Planck Institute for Chemistry, Particle Chemistry Department, Mainz, Germany
  • 6Laboratoire Meteorologie Physique (LaMP), 24 avenue des Landais, 63177 Aubière, France
  • 7Laboratoire Interuniversitaire des Systemes Atmospheriques, CNRS, Universites Paris-Est & Paris Diderot, 61 av. Du Gal de Gaulle, 94010 Cretéil, France
  • 8Leibniz Institute for Tropospheric Research, Leipzig, Germany
  • 9Paul Scherrer Institute, Laboratory of Atmospheric Chemistry, Villigen, Switzerland
  • 10Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, USA
  • 11Department of Physics, University of Helsinki, Helsinki, Finland
  • anow at: LOA, UMR8518, CNRS – Universiteì Lille1, Villeneuve d'Ascq, France

Abstract. Ambient particle number size distributions were measured in Paris, France, during summer (1–31 July 2009) and winter (15 January to 15 February 2010) at three fixed ground sites and using two mobile laboratories and one airplane. The campaigns were part of the Megacities: Emissions, urban, regional and Global Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation (MEGAPOLI) project. New particle formation (NPF) was observed only during summer on approximately 50 % of the campaign days, assisted by the low condensation sink (about 10.7 ± 5.9 × 10−3 s−1). NPF events inside the Paris plume were also observed at 600 m altitude onboard an aircraft simultaneously with regional events identified on the ground. Increased particle number concentrations were measured aloft also outside of the Paris plume at the same altitude, and were attributed to NPF. The Paris plume was identified, based on increased particle number and black carbon concentration, up to 200 km away from the Paris center during summer. The number concentration of particles with diameters exceeding 2.5 nm measured on the surface at the Paris center was on average 6.9 ± 8.7 × 104 and 12.1 ± 8.6 × 104 cm−3 during summer and winter, respectively, and was found to decrease exponentially with distance from Paris. However, further than 30 km from the city center, the particle number concentration at the surface was similar during both campaigns. During summer, one suburban site in the NE was not significantly affected by Paris emissions due to higher background number concentrations, while the particle number concentration at the second suburban site in the SW increased by a factor of 3 when it was downwind of Paris.

Short summary
Aerosol size distribution measurements from three ground sites, two mobile laboratories, and one airplane are combined to investigate the spatial and temporal variability of ultrafine particles in and around Paris during the summer and winter MEGAPOLI campaigns. The role of nucleation as a particle source and the influence of Paris emissions on their surroundings are examined.
Final-revised paper