| Title: | Second-Order Kinetic Rate Coefficients for the Aqueous-Phase Hydroxyl Radical (OH) Oxidation of Isoprene-Derived Secondary Organic Aerosol Compounds at 298 K |
| Author(s): | Abellar KA; Cope JD; Nguyen TB; |
| Address: | "Department of Chemistry, University of California-Davis, Davis, California 95616, United States. Department of Environmental Toxicology, University of California-Davis, Davis, California 95616, United States" |
| ISSN/ISBN: | 1520-5851 (Electronic) 0013-936X (Linking) |
| Abstract: | "The hydroxyl radical (OH) oxidation of the most abundant nonmethane volatile organic compound emitted to the atmosphere, isoprene (C(5)H(8)), produces a number of chemical species that partition to the condensed phase via gas-particle partitioning or form condensed-phase compounds via multiphase/heterogeneous chemistry to generate secondary organic aerosols (SOA). The SOA species in aerosol water or cloud/fog droplets may oxidize further via aqueous reaction with OH radicals, among other fates. Rate coefficients for compounds in isoprene's photochemical cascade are well constrained in the gas phase; however, a gap of information exists for the aqueous OH rate coefficients of the condensed-phased products, precluding the atmospheric modeling of the oxidative fate of isoprene-derived SOA. This work investigated the OH-initiated oxidation kinetic rate coefficients (k(OH)) for six major SOA compounds formed from the high-NO and low-NO channels of isoprene's atmospheric oxidation and one analog, most of which were synthesized and purified for study: (k(1)) 2-methyltetrol [MT: 1.14 (+/-0.17) x 10(9) M(-1) s(-1)], (k(2)) 2-methyl-1,2,3-trihydroxy-4-sulfate [MT-4-S: 1.52 (+/-0.25) x 10(9) M(-1) s(-1)], (k(3)) 2-methyl-1,2-dihydroxy-3-sulfate [MD-3-S: 0.56 (+/-0.15) x 10(9) M(-1) s(-1)], (k(4)) 2-methyl-1,2-dihydroxy-but-3-ene [MDE: 4.35 (+/-1.16) x 10(9) M(-1) s(-1)], (k(5)) 2-methyl-2,3-dihydroxy-1,4-dinitrate [MD-1,4-DN: 0.24 (+/-0.04) x 10(9) M(-1) s(-1)], (k(6)) 2-methyl-1,2,4-trihydroxy-3-nitrate [MT-3-N: 1.12 (+/-0.15) x 10(9) M(-1) s(-1)], and (k(7)) 2-methylglyceric acid [MGA: pH 2:1.41 (+/-0.49) x 10(9) M(-1) s(-1); pH 5:0.97 (+/-0.42) x 10(9) M(-1) s(-1)]. The second-order rate coefficients are determined against the known k(OH) of erythritol in pure water. The decays of each reagent were measured with nuclear magnetic resonance (NMR) and high-performance liquid chromatography-high resolution mass spectrometry (HPLC-HRMS). The aqueous photooxidation fates of isoprene-derived SOA compounds are substantial and may impact the SOA budget when implemented into global models" |
| Keywords: | Aerosols Butadienes Hemiterpenes *Hydroxyl Radical Oxidation-Reduction *Volatile Organic Compounds Water OH radical oxidation aqueous photooxidation isoprene derived compounds methyltetrol organonitrate organosulfate; |
| Notes: | "MedlineAbellar, Karizza A Cope, James D Nguyen, Tran B eng Research Support, N.I.H., Extramural Research Support, U.S. Gov't, Non-P.H.S. 2021/09/30 Environ Sci Technol. 2021 Oct 19; 55(20):13728-13736. doi: 10.1021/acs.est.1c04606. Epub 2021 Sep 29" |
