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Title: Single-particle experiments measuring humidity and inorganic salt effects on gas-particle partitioning of butenedial
Abstract. An improved understanding of the fate and properties of atmospheric aerosolparticles requires a detailed process-level understanding of fundamentalfactors influencing the aerosol, including partitioning of aerosolcomponents between the gas and particle phases. Laboratory experiments withlevitated particles provide a way to study fundamental aerosol processesover timescales relevant to the multiday lifetime of atmospheric aerosolparticles, in a controlled environment in which various characteristicsrelevant to atmospheric aerosol can be prepared (e.g., highsurface-to-volume ratio, highly concentrated or supersaturated solutions,changes to relative humidity). In this study, the four-carbon unsaturatedcompound butenedial, a dialdehyde produced by oxidation of aromaticcompounds that undergoes hydration in the presence of water, was used as amodel organic aerosol component to investigate different factors affectinggas–particle partitioning, including the role of lower-volatility“reservoir” species such as hydrates, timescales involved inequilibration between higher- and lower-volatility forms, and the effect ofinorganic salts. The experimental approach was to use a laboratory systemcoupling particle levitation in an electrodynamic balance (EDB) withparticle composition measurement via mass spectrometry (MS). In particular,by fitting measured evaporation rates to a kinetic model, the effectivevapor pressure was determined for butenedial and compared under differentexperimental conditions, including as a function of ambient relativehumidity and the presence of high concentrations of inorganic salts. Even underdry (RH<5 %) conditions, the evaporation rate of butenedial isorders of magnitude lower than what would be expected if butenedial existedpurely as a dialdehyde in the particle, implying an equilibrium stronglyfavoring hydrated forms and the strong preference of certain dialdehydecompounds to remain in a hydrated form even under lower water contentconditions. Butenedial exhibits a salting-out effect in the presence ofsodium chloride and sodium sulfate, in contrast to glyoxal. The outcomes ofthese experiments are also helpful in guiding the design of future EDB-MSexperiments.  more » « less
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Journal Name:
Atmospheric Chemistry and Physics
Page Range / eLocation ID:
14195 to 14209
Medium: X
Sponsoring Org:
National Science Foundation
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