1Department of Physics, University of Helsinki, P.O. Box 64, 00014 Helsinki, Finland
2Department of Chemical Engineering, Columbia University, 10027 New York, USA
3Helsinki Institute of Physics, University of Helsinki, P.O. Box 64, 00014 Helsinki, Finland
4AirModus OY, Helsinki, Finland
5Department of Applied Environmental Science and Bert Bolin Center for Climate Research, Stockholm University, 10691 Stockholm, Sweden
6Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark
Abstract. The Volatility-Hygroscopicity Tandem Differential Mobility Analyzer (VH-TDMA) was applied to study the hygroscopicity and volatility properties of submicron atmospheric aerosol in a boreal forest environment in Hyytiälä, Finland during the summer of 2010. Aitken and accumulation mode particles (50 nm, 75 nm and 110 nm) were investigated. The results suggest that the particles were internally mixed at all sizes. Hygroscopicity was found to increase with size. The relative mass fraction of organics and SO42− is probably the major contributor to the fluctuation of the hygroscopicity for all particle sizes. The Cloud Condensation Nuclei counter (CCNc)-derived hygroscopicity parameter κ was slightly higher than κ calculated from VH-TDMA data under sub-saturated conditions, which can be explained by the fact that particulate organics have a different degree of dissolution in sub- and supersaturated conditions. Also, the size-resolved volatility properties of particles were investigated. Upon heating, small particles evaporated more compared to large particles. There was a significant amount of aerosol volume (non-volatile material) left even at heating temperatures above 280 °C. Using size resolved volatility-hygroscopicity analysis, we concluded that there was always hygroscopic material remaining in the particles of different sizes at all different heating temperatures, even above 280 °C. This indicates that the observed non-volatile aerosol material was not consisting solely of black carbon.