Articles | Volume 10, issue 15
Atmos. Chem. Phys., 10, 7009–7016, 2010

Special issue: European Integrated Project on Aerosol-Cloud-Climate and Air...

Atmos. Chem. Phys., 10, 7009–7016, 2010

  02 Aug 2010

02 Aug 2010

Nanoparticles in boreal forest and coastal environment: a comparison of observations and implications of the nucleation mechanism

K. Lehtipalo1, M. Kulmala1, M. Sipilä1,2, T. Petäjä1, M. Vana1,3, D. Ceburnis4, R. Dupuy4,*, and C. O'Dowd4 K. Lehtipalo et al.
  • 1Department of Physics, University of Helsinki, P.O. Box 64, 00014, Helsinki, Finland
  • 2Helsinki Institute of Physics, University of Helsinki, P.O. Box 64, 00014, Helsinki, Finland
  • 3Institute of Physics, University of Tartu, Ülikooli 18, 50090 Tartu, Estonia
  • 4School of Physics & Centre for Climate and Air Pollution Studies, Environmental Change Institute, National University of Ireland Galway, Galway, Ireland
  • *currently at: Université Blaise Pascal, INSU, UMR6016, Laboratoire de Météorologie Physique, 63177 Aubiere, France

Abstract. The detailed mechanism of secondary new particle formation in the atmosphere is still under debate. It is proposed that particle formation happens via activation of 1–2 nm atmospheric neutral molecular clusters and/or large molecules. Since traditional instrumentation does not reach these sizes, the hypothesis has not yet been verified. By directly measuring particle size distributions down to mobility diameters of about 1.3 nm with a pulse-height CPC, we provide evidence of the nucleation mechanism in a coastal environment (Mace Head, Ireland) and in a boreal forest (Hyytiälä, Finland). In both places neutral sub-3 nm condensation nuclei (nano-CN) were continuously present, even when no new particle formation was detected. In Mace Head, however, the concentration of the nano-CN was far too low to account for the particle formation rates during particle bursts. Thus the results imply that at coastal sites new particle formation initiates, as previously proposed, via homogenous nucleation from biogenic iodine vapors. In contrast, activation of pre-existing nano-CN remains a possible explanation in the boreal forest, but the observed concentrations are not the limiting factor for the particle formation events.

Final-revised paper