title: Evidence for oligomer formation in clouds: reactions of isoprene oxidation products.
abstract: Electrospray ionization mass spectrometry (ESI-MS) was used to investigate product formation in laboratory experiments designed to study secondary organic aerosol (SOA) formation in clouds. It has been proposed that water soluble aldehydes derived from aromatics and alkenes, including isoprene, oxidize further in cloud droplets forming organic acids and, upon droplet evaporation, SOA. Pyruvic acid is an important aqueous-phase intermediate. Time series samples from photochemical batch aqueous phase reactions of pyruvic acid and hydrogen peroxide were analyzed for product formation. In addition to the monomers predicted by the reaction scheme, products consistent with an oligomer system were found when pyruvic acid and OH radical were both present. No evidence of oligomer formation was found in a standard mix composed of pyruvic, glyoxylic, and oxalic acids prepared in the same matrix as the samples analyzed using the same instrument conditions. The distribution of high molecular weight products is consistent with oligomers composed of the mono-, oxo-, and di-carboxylic acids expected from the proposed reaction scheme.
authors.affiliation: Institute of Marine and Coastal Sciences, Department of Environmental Sciences, Rutgers NOAA CMER Program, Rutgers, The State University of New Jersey, New Brunswick 08901-8521, USA. altieri@marine.rutgers.edu
authors.forename: Katye E
authors.initials: KE
authors.lastname: Altieri
authors.forename: Annmarie G
authors.initials: AG
authors.lastname: Carlton
authors.forename: Ho-Jin
authors.initials: HJ
authors.lastname: Lim
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Turpin
authors.forename: Sybil P
authors.initials: SP
authors.lastname: Seitzinger
mesh_terms: D000447:Aldehydes / Q000032:analysis*; D001272:Atmosphere; D002070:Butadienes / Q000032:analysis* / Q000737:chemistry; D004784:Environmental Monitoring / Q000379:methods*; D006038:Glyoxylates / Q000032:analysis; D045782:Hemiterpenes / Q000032:analysis* / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry; D017665:Hydroxyl Radical / Q000737:chemistry; D007477:Ions; D008956:Models, Chemical; D008970:Molecular Weight; D019815:Oxalic Acid / Q000032:analysis; D010420:Pentanes / Q000032:analysis* / Q000737:chemistry; D019289:Pyruvic Acid / Q000032:analysis / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D014867:Water / Q000737:chemistry
chemical_list: D000447:Aldehydes; D002070:Butadienes; D006038:Glyoxylates; D045782:Hemiterpenes; D007477:Ions; D010420:Pentanes; D014867:Water; C005059:isoprene; D017665:Hydroxyl Radical; D019289:Pyruvic Acid; D019815:Oxalic Acid; D006861:Hydrogen Peroxide; C031150:glyoxylic acid