Second-Order Kinetic Rate Coefficients for the Aqueous-Phase Hydroxyl Radical (OH) Oxidation of Isoprene-Derived Secondary Organic Aerosol Compounds at 298 K

• DOI: 10.1021/acs.est.1c04606
• Publication Date: 2021-09-29T23:49:07Z
• Authors: Karizza A. Abellar; James D. Cope; Tran B. Nguyen
• Keywords: Isoprene; Hydroxyl radical; Aqueous two-phase system; Atmospheric chemistry

The hydroxyl radical (OH) oxidation of the most abundant nonmethane volatile organic compound emitted to atmosphere, isoprene (C5H8), produces a number chemical species that partition condensed phase via gas-particle partitioning or form condensed-phase compounds multiphase/heterogeneous chemistry generate secondary aerosols (SOA). SOA in aerosol water cloud/fog droplets may oxidize further aqueous reaction with OH radicals, among other fates. Rate coefficients for isoprene's photochemical cascade are well constrained gas phase; however, gap information exists rate condensed-phased products, precluding atmospheric modeling oxidative fate isoprene-derived SOA. This work investigated OH-initiated kinetic (kOH) six major formed from high-NO and low-NO channels one analog, which were synthesized purified study: (k1) 2-methyltetrol [MT: 1.14 (±0.17) × 109 M–1 s–1], (k2) 2-methyl-1,2,3-trihydroxy-4-sulfate [MT-4-S: 1.52 (±0.25) (k3) 2-methyl-1,2-dihydroxy-3-sulfate [MD-3-S: 0.56 (±0.15) (k4) 2-methyl-1,2-dihydroxy-but-3-ene [MDE: 4.35 (±1.16) (k5) 2-methyl-2,3-dihydroxy-1,4-dinitrate [MD-1,4-DN: 0.24 (±0.04) (k6) 2-methyl-1,2,4-trihydroxy-3-nitrate [MT-3-N: 1.12 (k7) 2-methylglyceric acid [MGA: pH 2:1.41 (±0.49) s–1; 5:0.97 (±0.42) s–1]. second-order determined against known kOH erythritol pure water. decays each reagent measured nuclear magnetic resonance (NMR) high-performance liquid chromatography-high resolution mass spectrometry (HPLC-HRMS). photooxidation fates substantial impact budget when implemented into global models.