title: Reactive uptake of an isoprene-derived epoxydiol to submicron aerosol particles.
abstract: The reactive uptake of isoprene-derived epoxydiols (IEPOX) is thought to be a significant source of atmospheric secondary organic aerosol (SOA). However, the IEPOX reaction probability (γIEPOX) and its dependence upon particle composition remain poorly constrained. We report measurements of γIEPOX for trans-β-IEPOX, the predominant IEPOX isomer, on submicron particles as a function of composition, acidity, and relative humidity (RH). Particle acidity had the strongest effect. γIEPOX is more than 500 times greater on ammonium bisulfate (γ ∼ 0.05) than on ammonium sulfate (γ ≤ 1 × 10(-4)). We could accurately predict γIEPOX using an acid-catalyzed, epoxide ring-opening mechanism and a high Henry's law coefficient (1.7 × 10(8) M/atm). Suppression of γIEPOX was observed on particles containing both ammonium bisulfate and poly(ethylene glycol) (PEG-300), likely due to diffusion and solubility limitations within a PEG-300 coating, suggesting that IEPOX uptake could be self-limiting. Using the measured uptake kinetics, the predicted atmospheric lifetime of IEPOX is a few hours in the presence of highly acidic particles (pH < 0) but is greater than 25 h on less acidic particles (pH > 3). This work highlights the importance of aerosol acidity for accurately predicting the fate of IEPOX and anthropogenically influenced biogenic SOA formation.
authors.affiliation: Department of Atmospheric Sciences, University of Washington , Seattle, Washington 98195 United States.
authors.forename: Cassandra J
authors.initials: CJ
authors.lastname: Gaston
authors.forename: Theran P
authors.initials: TP
authors.lastname: Riedel
authors.forename: Zhenfa
authors.initials: Z
authors.lastname: Zhang
authors.forename: Avram
authors.initials: A
authors.lastname: Gold
authors.forename: Jason D
authors.initials: JD
authors.lastname: Surratt
authors.forename: Joel A
authors.initials: JA
authors.lastname: Thornton
mesh_terms: D000143:Acids / Q000737:chemistry; D000336:Aerosols / Q000737:chemistry*; D001272:Atmosphere / Q000737:chemistry; D002070:Butadienes / Q000737:chemistry*; D004852:Epoxy Compounds / Q000737:chemistry*; D045782:Hemiterpenes / Q000737:chemistry*; D007700:Kinetics; D010420:Pentanes / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D000143:Acids; D000336:Aerosols; D002070:Butadienes; D004852:Epoxy Compounds; D045782:Hemiterpenes; D010420:Pentanes; D014867:Water; C005059:isoprene