1Air Chemistry Department, Max-Planck Institute of Chemistry, Mainz, Germany
2Plant and Vegetation Ecology, University of Antwerp, Wilrijk, Belgium
3Faculty of Chemistry, University of Sciences and Technology Houari Boumediene, Algiers, Algeria
4Department of Physics, University of Helsinki, Helsinki, Finland
5Atmospheric Trace Gases and Ions, Max-Planck-Institute for Nuclear Physics, Heidelberg, Germany
6Atmospheric trace gases, Institute of Atmospheric Physics, DLR, Oberpfaffenhofen-Wessling, Germany
Abstract. In this study we present measurements of selected trace gases and aerosols made in a boreal forest during the BACCI-QUEST IV intensive field campaign in Hyytiälä, Finland in April 2005. Springtime diel and vertical variations of VOCs are discussed in connection with the variations in other trace gases and with the prevailing meteorological conditions. A daytime and a nighttime event have been analysed in detail. The nighttime particle event occurred synchronously with huge increases in monoterpenes, while the second event type involved nucleation and was anti-correlated with sulphuric acid. Here we discuss the possible origins of these two distinct forms of aerosol production at the Hyytiälä site using the measurement data, air mass back trajectories and the optical stereoisomery of monoterpenes. Optical stereoisomery is used in source identification to distinguish between unnatural and natural monoterpene emissions.