Issue 16, 2021

Ionic-strength and pH dependent reactivities of ascorbic acid toward ozone in aqueous micro-droplets studied using aerosol optical tweezers

Abstract

The heterogeneous oxidation reaction of single aqueous ascorbic acid (AH2) aerosol particles with gas-phase ozone was investigated in this study utilizing aerosol optical tweezers with Raman spectroscopy. The measured liquid-phase bimolecular rate coefficients of the AH2 + O3 reaction exhibit a significant pH dependence, and the corresponding values at ionic strength 0.2 M are (3.1 ± 2.0) × 105 M−1 s−1 and (1.2 ± 0.6) × 107 M−1 s−1 for pH ≈ 2 and 6, respectively. These results measured in micron-sized droplets are in agreement with those from previous bulk measurements, indicating that the observed aerosol reaction kinetics can be solely explained by liquid phase diffusion and AH2 + O3 reaction. Furthermore, the results indicate that high ionic strengths could enhance the liquid-phase rate coefficients of the AH2 + O3 reaction. The results also exhibit a negative ozone pressure dependence that can be rationalized in terms of a Langmuir–Hinshelwood type mechanism for the heterogeneous oxidation of AH2 aerosol particles by gas-phase ozone. The results of the present work imply that in acidified airway-lining fluids the antioxidant ability of AH2 against atmospheric ozone will be significantly suppressed.

Graphical abstract: Ionic-strength and pH dependent reactivities of ascorbic acid toward ozone in aqueous micro-droplets studied using aerosol optical tweezers

Supplementary files

Article information

Article type
Paper
Submitted
15 Dec 2020
Accepted
30 Mar 2021
First published
31 Mar 2021

Phys. Chem. Chem. Phys., 2021,23, 10108-10117

Ionic-strength and pH dependent reactivities of ascorbic acid toward ozone in aqueous micro-droplets studied using aerosol optical tweezers

Y. Chang, S. Wu, M. Lin, C. Chiang and G. G. Huang, Phys. Chem. Chem. Phys., 2021, 23, 10108 DOI: 10.1039/D0CP06493A

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