title: Kinetics, Mechanism, and Secondary Organic Aerosol Yield of Aqueous Phase Photo-oxidation of α-Pinene Oxidation Products.
abstract: Formation of secondary organic aerosol (SOA) involves atmospheric oxidation of volatile organic compounds (VOCs), the majority of which are emitted from biogenic sources. Oxidation can occur not only in the gas-phase but also in atmospheric aqueous phases such as cloudwater and aerosol liquid water. This study explores for the first time the aqueous-phase OH oxidation chemistry of oxidation products of α-pinene, a major biogenic VOC species emitted to the atmosphere. The kinetics, reaction mechanisms, and formation of SOA compounds in the aqueous phase of two model compounds, cis-pinonic acid (PIN) and tricarballylic acid (TCA), were investigated in the laboratory; TCA was used as a surrogate for 3-methyl-1,2,3-butanetricarboxylic acid (MBTCA), a known α-pinene oxidation product. Aerosol time-of-flight chemical ionization mass spectrometry (Aerosol-ToF-CIMS) was used to follow the kinetics and reaction mechanisms at the molecular level. Room-temperature second-order rate constants of PIN and TCA were determined to be 3.3 (± 0.5) × 10(9) and 3.1 (± 0.2) × 10(8) M(-1) s(-1), respectively, from which were estimated their condensed-phase atmospheric lifetimes. Aerosol-ToF-CIMS detected a large number of products leading to detailed reaction mechanisms for PIN and MBTCA. By monitoring the particle size distribution after drying, the amount of SOA material remaining in the particle phase was determined. An aqueous SOA yield of 40 to 60% was determined for PIN OH oxidation. Although recent laboratory studies have focused primarily on aqueous-phase processing of isoprene-related compounds, we demonstrate that aqueous formation of SOA materials also occurs from monoterpene oxidation products, thus representing an additional source of biogenically driven aerosol formation.
authors: Department of Chemistry, University of Toronto , 80 St. George Street, Toronto, Ontario M3S 3H6, Canada.
authors: Dana
authors: D
authors: Aljawhary
authors: Department of Chemistry, University of Toronto , 80 St. George Street, Toronto, Ontario M3S 3H6, Canada.
authors: Ran
authors: R
authors: Zhao
authors: Department of Chemistry, University of Toronto , 80 St. George Street, Toronto, Ontario M3S 3H6, Canada.
authors: Alex K Y
authors: AK
authors: Lee
authors: Department of Physical and Environmental Sciences and Department of Chemistry, University of Toronto Scarborough , 1265 Military Trail, Toronto, Ontario M1C 1A4, Canada.
authors: Chen
authors: C
authors: Wang
authors: Department of Chemistry, University of Toronto , 80 St. George Street, Toronto, Ontario M3S 3H6, Canada.
authors: Jonathan P D
authors: JP
authors: Abbatt
mesh_terms: D000336:Aerosols / Q000737:chemistry*; D000081008:Bicyclic Monoterpenes; D007700:Kinetics; D039821:Monoterpenes / Q000737:chemistry*; D009930:Organic Chemicals / Q000737:chemistry*; D010084:Oxidation-Reduction; D010777:Photochemistry; D014233:Tricarboxylic Acids / Q000737:chemistry
chemical_list: D000336:Aerosols; D000081008:Bicyclic Monoterpenes; D039821:Monoterpenes; D009930:Organic Chemicals; D014233:Tricarboxylic Acids; C005451:alpha-pinene