title: Evaluating the mixing of organic aerosol components using high-resolution aerosol mass spectrometry.
abstract: According to the pseudo-ideal mixing assumption employed in practically all chemical transport models, organic aerosol components from different sources interact with each other in a single solution, independent of their composition. This critical assumption greatly affects modeled organic aerosol concentrations, but there is little direct experimental evidence to support it. A main experimental challenge is that organic aerosol components from different sources often look similar when analyzed with an aerosol mass spectrometer. We developed a new experimental method to overcome this challenge, using isotopically labeled compounds ((13)C or D) and a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). We generated mixtures of secondary organic aerosol (SOA) from isotopically labeled toluene and from unlabeled α-pinene and used the HR-ToF-AMS data to separate these different SOA types. We evaluated their interaction by comparing the aerosol mass yields of toluene and α-pinene when the SOA was formed in these mixtures to their yields when the SOA was formed in isolation. At equilibrium, our results are consistent with pseudo-ideal mixing of anthropogenic and biogenic SOA components from these chemically dissimilar precursors.
authors: Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA, USA.
authors: Lea
authors: L
authors: Hildebrandt
authors: Kaytlin M
authors: KM
authors: Henry
authors: Jesse H
authors: JH
authors: Kroll
authors: Douglas R
authors: DR
authors: Worsnop
authors: Spyros N
authors: SN
authors: Pandis
authors: Neil M
authors: NM
authors: Donahue
mesh_terms: D000336:Aerosols / Q000032:analysis*; D000081008:Bicyclic Monoterpenes; D013058:Mass Spectrometry / Q000379:methods*; D039821:Monoterpenes / Q000032:analysis; D009930:Organic Chemicals / Q000032:analysis*; D012015:Reference Standards; D013997:Time Factors; D014050:Toluene / Q000032:analysis
chemical_list: D000336:Aerosols; D000081008:Bicyclic Monoterpenes; D039821:Monoterpenes; D009930:Organic Chemicals; D014050:Toluene; C005451:alpha-pinene