1. Aerosol Physics Laboratory, Department of Physics, Tampere University of Technology, P. O. Box 692, FIN −33101, Tampere, Finland, Atmospheric Physics Division, Max Planck Institute for Nuclear Physis (MPIK), P.O. Box103980, D-69029, Heidelberg, Germany, Department of Technology, Helsinki Polytechnic, P.O. Box 4020, FI-00099 Helsinki, Finland, Department of Physical Sciences, University of Helsinki, P.O. Box 64, FI-00014 Helsinki, Finland, Finnish Institute of Occupational Health, FI-00250 Helsinki,...