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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
doi:10.5194/acp-2016-774
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
14 Oct 2016
Review status
A revision of this discussion paper was accepted for the journal Atmospheric Chemistry and Physics (ACP) and is expected to appear here in due course.
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, Annele Virtanen2, Mikael Ehn1, Pauli Paasonen1, Douglas R. Worsnop5, Ilona Riipinen6, 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
5Aerodyne Research, Inc., Billerica, Massachusetts, USA
6Department of Environmental Science and Analytical Chemistry, Stockholm University, 10961 Stockholm, Sweden
Abstract. Volatility distribution of secondary organic aerosols, i.e. the particle mass fractions of semi-volatile, low-volatility and extremely low-volatility organic compounds 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 of 2014. On average, 40 % of organics in particles was semi-volatile; 34 % low-volatility organics and 26 % extremely low-volatility organics. The model was, however, very sensitive towards 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 were assumed. The low effective enthalpy value might result from several potential reasons, 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-volatile 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 m/z 43 (f43) and m/z 44 (f44). The mass fractions of these two organic groups were compared against the VTDMA-based results. In general, the agreement between the VTDMA results and the PMF-derived mass fractions of organics was reasonable with a linear correlation coefficient of around 0.4 with ΔHVAP = 80 kJ/mol set for all organic groups. The prospect of determining of extremely low volatile organic aerosols (ELVOA) 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., 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. Discuss., doi:10.5194/acp-2016-774, in review, 2016.
Juan Hong et al.
Interactive discussionStatus: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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RC1: 'Review of acp-2016-774', Anonymous Referee #2, 14 Oct 2016 Printer-friendly Version Supplement 
 
RC2: 'Reviewer comments', Anonymous Referee #1, 22 Dec 2016 Printer-friendly Version 
AC2: 'Answers to Referee#2's comments', Juan Hong, 06 Feb 2017 Printer-friendly Version Supplement 
 
AC1: 'Answers to Referee#1's comments', Juan Hong, 06 Feb 2017 Printer-friendly Version Supplement 
Juan Hong et al.
Juan Hong et al.

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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 as well as by applying Positive Matrix Factorization (PMF) to High-Resolution Aerosol Mass Spectrometer data. The agreement between the results from these two methods was relatively reasonable.
Estimates of Volatility of secondary organic aerosols was characterized in a boreal forest...
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