1Department of Physics, University of Helsinki, P.O. Box 64, 00014 Helsinki, Finland
2Finnish Meteorological Institute, Erik Palménin aukio 1, 00560 Helsinki, Finland
3Institute for Energy and Climate Research (IEK-8), Forschungszentrum Jülich, 52425 Jülich, Germany
4Aerodyne Research, Inc., Billerica, Massachusetts, USA
5Department of Applied Environmental Science and Bert Bolin Centre for Climate Research, Stockholm University, 10691 Stockholm, Sweden
Received: 18 Apr 2012 – Published in Atmos. Chem. Phys. Discuss.: 02 May 2012
Abstract. The volatility of submicron atmospheric aerosol particles was investigated at a boreal forest site in Hyytiälä, Finland from January 2008 to May 2010. These long-term observations allowed for studying the seasonal behavior of aerosol evaporation with a special focus on compounds that remained in the aerosol phase at 280 °C. The temperature-response of evaporation was also studied by heating the aerosol sample step-wise to six temperatures ranging from 80 °C to 280 °C. The mass fraction remaining after heating (MFR) was determined from the measured particle number size distributions before and after heating assuming a constant particle density (1.6 g cm−3). On average 19% of the total aerosol mass remained in the particulate phase at 280 °C. The particles evaporated less at low ambient temperatures during winter as compared with the warmer months. Black carbon (BC) fraction of aerosol mass correlated positively with the MFR at 280 °C, but could not explain it completely: most of the time a notable fraction of this non-volatile residual was something other than BC. Using additional information on ambient meteorological conditions and results from an Aerodyne aerosol mass spectrometer (AMS), the chemical composition of MFR at 280 °C and its seasonal behavior was further examined. Correlation analysis with ambient temperature and mass fractions of polycyclic aromatic hydrocarbons (PAHs) indicated that MFR at 280 °C is probably affected by anthropogenic emissions. On the other hand, results from the AMS analysis suggested that there may be very low-volatile organics, possibly organonitrates, in the non-volatile (at 280 °C) fraction of aerosol mass.
Revised: 05 Nov 2012 – Accepted: 08 Nov 2012 – Published: 16 Nov 2012
Citation: Häkkinen, S. A. K., Äijälä, M., Lehtipalo, K., Junninen, H., Backman, J., Virkkula, A., Nieminen, T., Vestenius, M., Hakola, H., Ehn, M., Worsnop, D. R., Kulmala, M., Petäjä, T., and Riipinen, I.: Long-term volatility measurements of submicron atmospheric aerosol in Hyytiälä, Finland, Atmos. Chem. Phys., 12, 10771-10786, doi:10.5194/acp-12-10771-2012, 2012.