Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 17, 4387-4399, 2017
http://www.atmos-chem-phys.net/17/4387/2017/
doi:10.5194/acp-17-4387-2017
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
31 Mar 2017
Estimates of the organic aerosol volatility in a boreal forest using two independent methods
Juan Hong1, Mikko Äijälä1, Silja A. K. Häme1, Liqing Hao2, Jonathan Duplissy1,3, Liine M. Heikkinen1, Wei Nie4, Jyri Mikkilä1, Markku Kulmala1, Nønne L. Prisle5,1, Annele Virtanen2, Mikael Ehn1, Pauli Paasonen1, Douglas R. Worsnop6, Ilona Riipinen7, Tuukka Petäjä1, and Veli-Matti Kerminen1 1Department of Physics, University of Helsinki, P.O. Box 64, 00014 Helsinki, Finland
2Department of Applied Physics, University of Eastern Finland, Kuopio 70211, Finland
3Helsinki Institute of Physics, University of Helsinki, P.O. Box 64, 00014 Helsinki, Finland
4Institute for Climate and Global Change Research & School of Atmospheric Sciences, Nanjing University, Nanjing, 210093, China
5University of Oulu, Nano and Molecular Systems Research Unit, P.O. Box 3000, 90014 University of Oulu, Oulu, Finland
6Aerodyne Research, Inc., Billerica, Massachusetts, USA
7Department of Environmental Science and Analytical Chemistry, Stockholm University, 10961 Stockholm, Sweden
Abstract. The volatility distribution of secondary organic aerosols that formed and had undergone aging – i.e., the particle mass fractions of semi-volatile, low-volatility and extremely low volatility organic compounds in the particle phase – was characterized in a boreal forest environment of Hyytiälä, southern Finland. This was done by interpreting field measurements using a volatility tandem differential mobility analyzer (VTDMA) with a kinetic evaporation model. The field measurements were performed during April and May 2014. On average, 40 % of the organics in particles were semi-volatile, 34 % were low-volatility organics and 26 % were extremely low volatility organics. The model was, however, very sensitive to the vaporization enthalpies assumed for the organics (ΔHVAP). The best agreement between the observed and modeled temperature dependence of the evaporation was obtained when effective vaporization enthalpy values of 80 kJ mol−1 were assumed. There are several potential reasons for the low effective enthalpy value, including molecular decomposition or dissociation that might occur in the particle phase upon heating, mixture effects and compound-dependent uncertainties in the mass accommodation coefficient. In addition to the VTDMA-based analysis, semi-volatile and low-volatility organic mass fractions were independently determined by applying positive matrix factorization (PMF) to high-resolution aerosol mass spectrometer (HR-AMS) data. The factor separation was based on the oxygenation levels of organics, specifically the relative abundance of mass ions at mz 43 (f43) and mz 44 (f44). The mass fractions of these two organic groups were compared against the VTDMA-based results. In general, the best agreement between the VTDMA results and the PMF-derived mass fractions of organics was obtained when ΔHVAP =  80 kJ mol−1 was set for all organic groups in the model, with a linear correlation coefficient of around 0.4. However, this still indicates that only about 16 % (R2) of the variation can be explained by the linear regression between the results from these two methods. The prospect of determining of extremely low volatility organic aerosols (ELVOAs) from AMS data using the PMF analysis should be assessed in future studies.

Citation: Hong, J., Äijälä, M., Häme, S. A. K., Hao, L., Duplissy, J., Heikkinen, L. M., Nie, W., Mikkilä, J., Kulmala, M., Prisle, N. L., Virtanen, A., Ehn, M., Paasonen, P., Worsnop, D. R., Riipinen, I., Petäjä, T., and Kerminen, V.-M.: Estimates of the organic aerosol volatility in a boreal forest using two independent methods, Atmos. Chem. Phys., 17, 4387-4399, doi:10.5194/acp-17-4387-2017, 2017.
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Short summary
Estimates of volatility of secondary organic aerosols was characterized in a boreal forest environment of Hyytiälä, southern Finland. This was done by interpreting field measurements using a volatility tandem differential mobility analyzer (VTDMA) with a kinetic evaporation model and by applying positive matrix factorization (PMF) to high-resolution aerosol mass spectrometer data. About 16 % of the variation can be explained by the linear regression between the results from these two methods.
Estimates of volatility of secondary organic aerosols was characterized in a boreal forest...
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