title: Role of Aerosol Liquid Water in Secondary Organic Aerosol Formation from Volatile Organic Compounds.
abstract: A key mechanism for atmospheric secondary organic aerosol (SOA) formation occurs when oxidation products of volatile organic compounds condense onto pre-existing particles. Here, we examine effects of aerosol liquid water (ALW) on relative SOA yield and composition from α-pinene ozonolysis and the photooxidation of toluene and acetylene by OH. Reactions were conducted in a room-temperature flow tube under low-NOxconditions in the presence of equivalent loadings of deliquesced (∼20 μg m-3ALW) or effloresced (∼0.2 μg m-3ALW) ammonium sulfate seeds at exactly the same relative humidity (RH = 70%) and state of wall conditioning. We found 13% and 19% enhancements in relative SOA yield for the α-pinene and toluene systems, respectively, when seeds were deliquesced rather than effloresced. The relative yield doubled in the acetylene system, and this enhancement was partially reversible upon drying the prepared SOA, which reduced the yield by 40% within a time scale of seconds. We attribute the high relative yield of acetylene SOA on deliquesced seeds to aqueous partitioning and particle-phase reactions of the photooxidation product glyoxal. The observed range of relative yields for α-pinene, toluene, and acetylene SOA on deliquesced and effloresced seeds suggests that ALW plays a complicated, system-dependent role in SOA formation.
authors.affiliation: Department of Chemistry, University of Toronto , 80 Saint George Street, Toronto, Ontario M5S 3H6, Canada.
authors.forename: Jennifer A
authors.identifier: 0000-0002-2574-7579
authors.initials: JA
authors.lastname: Faust
authors.affiliation: Department of Chemistry, University of Toronto , 80 Saint George Street, Toronto, Ontario M5S 3H6, Canada.
authors.forename: Jenny P S
authors.initials: JP
authors.lastname: Wong
authors.affiliation: Department of Chemistry, University of Toronto , 80 Saint George Street, Toronto, Ontario M5S 3H6, Canada.
authors.forename: Alex K Y
authors.initials: AK
authors.lastname: Lee
authors.affiliation: Department of Chemistry, University of Toronto , 80 Saint George Street, Toronto, Ontario M5S 3H6, Canada.
authors.forename: Jonathan P D
authors.identifier: 0000-0002-3372-334X
authors.initials: JP
authors.lastname: Abbatt
mesh_terms: D000336:Aerosols; D000393:Air Pollutants; D000645:Ammonium Sulfate; D039821:Monoterpenes; D010084:Oxidation-Reduction; D055549:Volatile Organic Compounds; D014867:Water
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D039821:Monoterpenes; D055549:Volatile Organic Compounds; D014867:Water; D000645:Ammonium Sulfate