Nanoparticles in boreal forest and coastal environment: a comparison of observations and implications of the nucleation mechanism 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
Received: 23 November 2009 – Published in Atmos. Chem. Phys. Discuss.: 11 December 2009 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.
Revised: 07 July 2010 – Accepted: 18 July 2010 – Published: 02 August 2010
Citation: Lehtipalo, K., Kulmala, M., Sipilä, M., Petäjä, T., Vana, M., Ceburnis, D., Dupuy, R., and O'Dowd, C.: Nanoparticles in boreal forest and coastal environment: a comparison of observations and implications of the nucleation mechanism, Atmos. Chem. Phys., 10, 7009-7016, doi:10.5194/acp-10-7009-2010, 2010.