Gas-Phase Oxidation Rates and Products of 1,2-Dihydroxy Isoprene

• DOI: 10.1021/acs.est.1c04177
• Publication Date: 2021-10-08T00:48:39Z
• Authors: Kelvin H. Bates; James D. Cope; Tran B. Nguyen
• Keywords: Aerosols; photochemistry; 550; oxidation; VOC; 540; Physical Chemistry; 01 natural sciences; Atmospheric Sciences; Hemiterpenes; Chemical Sciences; Earth Sciences; Butadienes; SOA; isoprene; biogenic; Oxidation-Reduction; Environmental Sciences; 0105 earth and related environmental sciences

1,2-Dihydroxy isoprene (1,2-DHI), a product of isoprene oxidation from multiple chemical pathways, is produced in the atmosphere in large quantities; however, its chemical fate has not been comprehensively studied. Here, we perform chamber experiments to investigate its gas-phase reactions. We find that the reactions of 1,2-DHI with OH radicals and ozone are rapid (kOH = 8.0 (±1.3) × 10-11 cm3 molecule-1 s-1; kO3 = 7.2 (±1.1) × 10-18 cm3 molecule-1 s-1). Reaction with OH, which dominates 1,2-DHI loss, leads primarily to fragmentation and radical recycling; major products under both high- and low-NO conditions include hydroxyacetone, glycolaldehyde, and 2,3-dihydroxy-2-methyl-propanal (DHMP). Radical-terminating hydroperoxide formation from the peroxy radical (RO2) reaction with HO2 and organonitrate formation from RO2 + NO are not observed in the gas phase, possibly due to low volatility; constraints for their branching ratios are instead derived by mass balance. We also measure secondary organic aerosol mass yields from 1,2-DHI (0-23%) and show that oxidation in the presence of aqueous particles leads to formic and acetic acid production. Finally, we incorporate results into GEOS-Chem, a global chemical transport model, to compute the global production (25.3 Tg a-1) and gas-phase loss (20.2 Tg a-1) of 1,2-DHI and show that its oxidation provides non-negligible contributions to the atmospheric budgets of hydroxyacetone, glycolaldehyde, hydroxymethyl hydroperoxide, formic acid, and DHMP.