Description: Phase partitioning and volatility of secondary organic aerosol components formed from α-pinene ozonolysis and OH oxidation: the importance of accretion products and other low volatility compounds

This title appears in the Scientific Report : 2015

Phase partitioning and volatility of secondary organic aerosol components formed from α-pinene ozonolysis and OH oxidation: the importance of accretion products and other low volatility compounds

We measured a large suite of gas- and particle-phase multi-functional organic compounds with a Filter Inlet for Gases and AEROsols (FIGAERO) coupled to a high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) developed at the University of Washington. The instrument was d...

Personal Name(s):	Lopez-Hilfiker, F. D.
	Mohr, C. / Ehn, M. / Rubach, F. / Kleist, E. / Wildt, J. / Mentel, Th. F. / Carrasquillo, A. J. / Daumit, K. E. / Hunter, J. F. / Kroll, J. H. / Worsnop, D. R. / Thornton, J. A. (Corresponding author)
Contributing Institute:	Pflanzenwissenschaften; IBG-2 Troposphäre; IEK-8
Published in:	Atmospheric chemistry and physics, 15 (2015) 14, S. 7765 - 7776
Imprint:	Katlenburg-Lindau EGU 2015
DOI:	10.5194/acp-15-7765-2015
Document Type:	Journal Article
Research Program:	Tropospheric trace substances and their transformation processes
Link:	Get full text OpenAccess
	Publikationsportal JuSER

Please use the identifier: http://hdl.handle.net/2128/8978 in citations.
Please use the identifier: http://dx.doi.org/10.5194/acp-15-7765-2015 in citations.

We measured a large suite of gas- and particle-phase multi-functional organic compounds with a Filter Inlet for Gases and AEROsols (FIGAERO) coupled to a high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) developed at the University of Washington. The instrument was deployed on environmental simulation chambers to study monoterpene oxidation as a secondary organic aerosol (SOA) source. We focus here on results from experiments utilizing an ionization method most selective towards acids (acetate negative ion proton transfer), but our conclusions are based on more general physical and chemical properties of the SOA. Hundreds of compounds were observed in both gas and particle phases, the latter being detected by temperature-programmed thermal desorption of collected particles. Particulate organic compounds detected by the FIGAERO–HR-ToF-CIMS are highly correlated with, and explain at least 25–50 % of, the organic aerosol mass measured by an Aerodyne aerosol mass spectrometer (AMS). Reproducible multi-modal structures in the thermograms for individual compounds of a given elemental composition reveal a significant SOA mass contribution from high molecular weight organics and/or oligomers (i.e., multi-phase accretion reaction products). Approximately 50 % of the HR-ToF-CIMS particle-phase mass is associated with compounds having effective vapor pressures 4 or more orders of magnitude lower than commonly measured monoterpene oxidation products. The relative importance of these accretion-type and other extremely low volatility products appears to vary with photochemical conditions. We present a desorption-temperature-based framework for apportionment of thermogram signals into volatility bins. The volatility-based apportionment greatly improves agreement between measured and modeled gas-particle partitioning for select major and minor components of the SOA, consistent with thermal decomposition during desorption causing the conversion of lower volatility components into the detected higher volatility compounds.