title: Transitions from functionalization to fragmentation reactions of laboratory secondary organic aerosol (SOA) generated from the OH oxidation of alkane precursors.
abstract: Functionalization (oxygen addition) and fragmentation (carbon loss) reactions governing secondary organic aerosol (SOA) formation from the OH oxidation of alkane precursors were studied in a flow reactor in the absence of NO(x). SOA precursors were n-decane (n-C10), n-pentadecane (n-C15), n-heptadecane (n-C17), tricyclo[5.2.1.0(2,6)]decane (JP-10), and vapors of diesel fuel and Southern Louisiana crude oil. Aerosol mass spectra were measured with a high-resolution time-of-flight aerosol mass spectrometer, from which normalized SOA yields, hydrogen-to-carbon (H/C) and oxygen-to-carbon (O/C) ratios, and C(x)H(y)+, C(x)H(y)O+, and C(x)H(y)O(2)+ ion abundances were extracted as a function of OH exposure. Normalized SOA yield curves exhibited an increase followed by a decrease as a function of OH exposure, with maximum yields at O/C ratios ranging from 0.29 to 0.74. The decrease in SOA yield correlates with an increase in oxygen content and decrease in carbon content, consistent with transitions from functionalization to fragmentation. For a subset of alkane precursors (n-C10, n-C15, and JP-10), maximum SOA yields were estimated to be 0.39, 0.69, and 1.1. In addition, maximum SOA yields correspond with a maximum in the C(x)H(y)O+ relative abundance. Measured correlations between OH exposure, O/C ratio, and H/C ratio may enable identification of alkane precursor contributions to ambient SOA.
authors.affiliation: Chemistry Department, Boston College, Chestnut Hill, Massachusetts, United States. andrew.lambe@bc.edu
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Lambe
authors.forename: Timothy B
authors.initials: TB
authors.lastname: Onasch
authors.forename: David R
authors.initials: DR
authors.lastname: Croasdale
authors.forename: Justin P
authors.initials: JP
authors.lastname: Wright
authors.forename: Alexander T
authors.initials: AT
authors.lastname: Martin
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Franklin
authors.forename: Paola
authors.initials: P
authors.lastname: Massoli
authors.forename: Jesse H
authors.initials: JH
authors.lastname: Kroll
authors.forename: Manjula R
authors.initials: MR
authors.lastname: Canagaratna
authors.forename: William H
authors.initials: WH
authors.lastname: Brune
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Worsnop
authors.forename: Paul
authors.initials: P
authors.lastname: Davidovits
mesh_terms: D000336:Aerosols / Q000032:analysis*; D000473:Alkanes / Q000737:chemistry*; D002244:Carbon / Q000032:analysis; D017665:Hydroxyl Radical / Q000737:chemistry*; D007753:Laboratories; D013058:Mass Spectrometry; D008800:Mexico; D009930:Organic Chemicals / Q000032:analysis*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000032:analysis; D059392:Petroleum Pollution / Q000032:analysis; D013997:Time Factors
chemical_list: D000336:Aerosols; D000473:Alkanes; D009930:Organic Chemicals; D017665:Hydroxyl Radical; D002244:Carbon; D010100:Oxygen