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- Title
Iodine activation photosensitized by imidazole carboxaldehyde.
- Authors
Ammann, Markus; Arroyo, Pablo Corral; Alpert, Peter
- Abstract
Ocean surface water and sea spray aerosol deriving from the latter contain chromophoricdissolved organic matter (CDOM). CDOM species (especially carbonyls, dicarbonyls oraromatic carbonyls such as imidazole-2-carboxaldehyde (IC)), referred to as photosensitizers,form triplet excited states upon UV-VIS light absorption. These triplet-excited states mayreact with halides generating halogen radicals and additionally molecular halogencompounds, which can be released into the gas phase and may thus contribute to halogenactivation. In this work we study the influence of bromide and iodide on condensed phaseradical cycling by irradiated coated wall flow tube (CWFT) experiments in mixtures ofhalides with citric acid (CA) as matrix and IC as photosensitizer. Iodine release was measuredby post-oxidation of iodine compounds and detected as ultrafine I2O5 particles. Weuse a kinetic model to interpret our results and to assess radical production andiodine release in sea-spray particles. As indicated by the experimental results andconfirmed by the model, significant recycling of halogen species occurs via scavengingreactions with HO2, to prevent the full and immediate release of the molecular halogen(bromine and iodine) produced, while partially shutting down the HOx chemistry.The recycling efficiency is higher under the effect of diffusion limitations at highviscosity prevailing at lower relative humidity or temperature. Photosensitized iodineactivitation becomes competitive with oxidation by ozone under those conditions.
- Subjects
IODINE; IODINE compounds; ORGANIC compounds; IMIDAZOLES; WATER; BROMINE
- Publication
Geophysical Research Abstracts, 2019, Vol 21, p1
- ISSN
1029-7006
- Publication type
Article