Iodine Activation from Iodate Reduction in Aqueous Films via Photocatalyzed and Dark Reactions
Year: 2024
Type: article
Abstract: High Resolution Image Download MS PowerPoint Slide Iodine in the atmosphere destroys ozone and can nucleate particles by formation of iodic acid, HIO 3 . Recent field observations suggest iodate recycles from particles sustaining significant gas-phase IO radical concentrations (0.06 pptv) in aged stratospheric air, and in elevated dust plumes. However, laboratory evidence for iodine activation from aerosols is currently missing. Here, a series of coated-wall flow tube (CWFT) experiments test for iodine release from thin aqueous films containing iodate. Photocatalyzed reactions were studied using iron(III) citrate (Fe–Cit), Arizona Test Dust (ATD), and Fe 2 O 3, along with the dark reaction of iodate with H 2 O 2 at 90% RH and 293 K. Fresh films were separately irradiated with visible and UV-A light, and the efficient release of molecular iodine, I 2, was observed from all irradiated films containing photocatalysts. For films with Fe–Cit, visible light reduced larger amounts of iodate than UV-A light, activating ∼40% of iodate as I 2 . The formation of oxygenated volatile organic compounds (OVOC) and iodinated OVOC was also observed. Dark exposure of films to H 2 O 2 led to I 2 release in smaller amounts than suggested by Bray–Liebhafsky kinetics, consistent with H 2 O 2 salting-out in the films, or possibly other reasons. Photochemical activation is enhanced by dust proxies in the film, and by aging the film with H 2 O 2 in the dark prior to irradiation. These findings help explain recent field observations of elevated IO radical concentrations in lofted dust layers, and warrant the inclusion of photocatalyzed iodate reduction in atmospheric models.
Source: ACS Earth and Space Chemistry
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,500
Awards: Iodine in the upper troposphere and lower stratosphere, G2454511144, The interplay between reactive oxygen species and the multiphase chemistry of nitrogen, halogen and secondary organic species in aerosol particles, International, Interdisciplinary and Intersectoral Postdoctoral Fellowships at the Paul Scherrer Institut, G4351905433, G5010255678, Collaborative Research: United States University CLOUD (Cosmics Leaving OUtdoor Droplets) Consortium Membership, Collaborative Research: Mercury Oxidation Pathways in a Continental Atmosphere: High Temporal Resolution Measurements of Mercury and Oxidants at Storm Peak Laboratory, Collaborative Research: TI3GER--Technological Innovation Into Iodine and Gv-aircraft Environmental Research, G8502912377, G8798067104
OpenAlex ID: W4404943601