Journal Article
Atmospheric Chemistry and Physics, vol. 19, iss. 17, pp. 11253-11265, 2019
Authors
Emma L. D'Ambro, Siegfried Schobesberger, Cassandra J. Gaston, Felipe D. Lopez-Hilfiker, Ben H. Lee, Jiumeng Liu, Alla Zelenyuk, David Bell, Christopher D. Cappa, Taylor Helgestad, Ziyue Li, Alex Guenther, Jian Wang, Matthew Wise, Ryan Caylor, Jason D. Surratt, Theran Riedel, Noora Hyttinen, Vili-Taneli Salo, Galib Hasan, Theo Kurten, John E. Shilling, Joel A. Thornton
Abstract
Abstract. We present measurements utilizing the Filter Inlet for Gases and Aerosols
(FIGAERO) applied to chamber measurements of isoprene-derived epoxydiol
(IEPOX) reactive uptake to aqueous acidic particles and associated secondary organic aerosol (SOA)
formation. Similar to recent field observations with the same instrument, we
detect two molecular components desorbing from the IEPOX SOA in high
abundance: C5H12O4 and C5H10O3. The thermal
desorption signal of the former, presumably 2-methyltetrols, exhibits two
distinct maxima, suggesting it arises from at least two different SOA
components with significantly different effective volatilities. Isothermal
evaporation experiments illustrate that the most abundant component giving
rise to C5H12O4 is semi-volatile, undergoing nearly complete
evaporation within 1 h while the second, less volatile component
remains unperturbed and even increases in abundance. We thus confirm, using
controlled laboratory studies, recent analyses of ambient SOA measurements
showing that IEPOX SOA is of very low volatility and commonly measured IEPOX
SOA tracers such as C5H12O4 and C5H10O3,
presumably 2-methyltetrols and C5-alkene triols or 3-MeTHF-3,4-diols,
result predominantly from thermal decomposition in the FIGAERO-CIMS. We
infer that other measurement techniques using thermal desorption or
prolonged heating for analysis of SOA components may also lead to reported
2-methyltetrols and C5-alkene triols or 3-MeTHF-3,4-diol structures.
We further show that IEPOX SOA volatility continues to evolve via acidity-enhanced accretion chemistry on the timescale of hours, potentially
involving both 2-methyltetrols and organosulfates.
