Toward Direct Measurement of Atmospheric Nucleation
Markku Kulmala,1*
Ilona Riipinen,1
Mikko Sipilä,1
Hanna E. Manninen,1
Tuukka Petäjä,1
Heikki Junninen,1
Miikka Dal Maso,1
Genrik Mordas,1
Aadu Mirme,2
Marko Vana,1,2
Anne Hirsikko,1
Lauri Laakso,1
Roy M. Harrison,3
Ian Hanson,3
Carl Leung,3
Kari E. J. Lehtinen,4
Veli-Matti Kerminen5
Atmospheric aerosol formation is known to occur almost all over
the world, and the importance of these particles to climate
and air quality has been recognized. Although almost all of
the processes driving aerosol formation take place below a particle
diameter of 3 nanometers, observations cover only larger particles.
We introduce an instrumental setup to measure atmospheric concentrations
of both neutral and charged nanometer-sized clusters. By applying
the instruments in the field, we come to three important conclusions:
(i) A pool of numerous neutral clusters in the sub–3 nanometer
size range is continuously present; (ii) the processes initiating
atmospheric aerosol formation start from particle sizes of
1.5
nanometers; and (iii) neutral nucleation dominates over the
ion-induced mechanism, at least in boreal forest conditions.
2 Institute of Environmental Physics, University of Tartu, Ülikooli 18, EE-50090, Tartu, Estonia.
3 Division of Environmental Health and Risk Management, School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
4 Department of Physics, University of Kuopio and Finnish Meteorological Institute, Kuopio Unit, Post Office Box 1627, 70211 Kuopio, Finland.
5 Finnish Meteorological Institute, Post Office Box 503, FI-00101, Helsinki, Finland.
* To whom correspondence should be addressed. E-mail: kulmala{at}pcu.helsinki.fi
