title: Products and mechanism of secondary organic aerosol formation from reactions of linear alkenes with NO3 radicals.
abstract: Secondary organic aerosol (SOA) formation from reactions of linear alkenes with NO(3) radicals was investigated in an environmental chamber using a thermal desorption particle beam mass spectrometer for particle analysis. A general chemical mechanism was developed to explain the formation of the observed SOA products. The major first-generation SOA products were hydroxynitrates, carbonylnitrates, nitrooxy peroxynitrates, dihydroxynitrates, and dihydroxy peroxynitrates. The major second-generation SOA products were hydroxy and oxo dinitrooxytetrahydrofurans, which have not been observed previously. The latter compounds were formed by a series of reactions in which delta-hydroxycarbonyls isomerize to cyclic hemiacetals, which then dehydrate to form substituted dihydrofurans (unsaturated compounds) that rapidly react with NO(3) radicals to form very low volatility products. For the approximately 1 ppmv alkene concentrations used here, aerosol formed only for alkenes C(7) or larger. SOA formed from C(7)-C(9) alkenes consisted only of second-generation products, whereas for larger alkenes first-generation products were also present and contributions increased with increasing carbon number apparently due to the formation of lower volatility products. The estimated mass fractions of first- and second-generation products were approximately 50:50, 30:70, 10:90, and 0:100, for 1-tetradecene, 1-dodecene, 1-decene, and 1-octene SOA, respectively. This study shows that delta-hydroxycarbonyls play a key role in the formation of SOA in alkene-NO(3) reactions and are likely to be important in other systems because delta-hydroxycarbonyls can also be formed from reactions of OH radicals and O(3) with hydrocarbons.
authors.affiliation: Air Pollution Research Center, University of California, Riverside, CA 92521, USA.
authors.forename: Huiming
authors.initials: H
authors.lastname: Gong
authors.forename: Aiko
authors.initials: A
authors.lastname: Matsunaga
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Ziemann
mesh_terms: D000336:Aerosols / Q000737:chemistry; D000475:Alkenes / Q000737:chemistry; D002627:Chemistry, Physical / Q000379:methods*; D004583:Electrons; D005609:Free Radicals / Q000737:chemistry; D006838:Hydrocarbons / Q000737:chemistry; D007477:Ions; D013058:Mass Spectrometry; D008956:Models, Chemical; D009566:Nitrates / Q000737:chemistry*; D013696:Temperature
chemical_list: D000336:Aerosols; D000475:Alkenes; D005609:Free Radicals; D006838:Hydrocarbons; D007477:Ions; D009566:Nitrates