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Volume 16, issue 19
Atmos. Chem. Phys., 16, 12703-12713, 2016
https://doi.org/10.5194/acp-16-12703-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Atmos. Chem. Phys., 16, 12703-12713, 2016
https://doi.org/10.5194/acp-16-12703-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 12 Oct 2016

Research article | 12 Oct 2016

Photolysis of frozen iodate salts as a source of active iodine in the polar environment

Óscar Gálvez1,a, M. Teresa Baeza-Romero2, Mikel Sanz2,b, and Alfonso Saiz-Lopez3 Óscar Gálvez et al.
  • 1Departamento de Física Molecular, Instituto de Estructura de la Materia, IEM-CSIC, 28006 Madrid, Spain
  • 2Escuela de Ingeniería Industrial, Universidad de Castilla-La Mancha, 45071 Toledo, Spain
  • 3Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, CSIC, 28006 Madrid, Spain
  • anow at: Departamento de Física Interdisciplinar, Facultad de Ciencias, Universidad Nacional de Educación a Distancia, 28040 Madrid, Spain
  • bnow at: Institute of Physical Chemistry Rocasolano, CSIC, 28006 Madrid, Spain

Abstract. Reactive halogens play a key role in the oxidation capacity of the polar troposphere. However, sources and mechanisms, particularly those involving active iodine, are still poorly understood. In this paper, the photolysis of an atmospherically relevant frozen iodate salt has been experimentally studied using infrared (IR) spectroscopy. The samples were generated at low temperatures in the presence of different amounts of water. The IR spectra have confirmed that, under near-ultraviolet–visible (UV–Vis) radiation, iodate is efficiently photolysed. The integrated IR absorption coefficient of the iodate anion on the band at 750cm−1 has been measured to be A = 9.8±0.5 × 10−17cmmolecule−1. The photolysis rate of the ammonium iodate salt was measured by monitoring the decay of ammonium or iodate IR bands (1430 and 750cm−1 respectively) in the presence of a solar simulator. The absorption cross section of the liquid solutions of ammonium iodate at wavelengths relevant for the troposphere (250 to 400nm) has been obtained and used to estimate the photolytic quantum yield for the frozen salt. Finally, using an atmospheric model, constrained with the experimental data, we suggest that the photolysis of iodate in frozen salt can potentially provide a pathway for the release of active iodine to the polar atmosphere.

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Reactive iodine species play a key role in the oxidation capacity of the polar troposphere, although sources and mechanisms are poorly understood. In this paper, the photolysis of frozen iodate salt has been studied, confirming that under near-UV–Vis radiation iodate is photolysed. Incorporating this result into an Antarctic atmospheric model, we have shown that it could increase the atmospheric IO levels and could constitute a pathway for the release of active iodine to the polar atmosphere
Reactive iodine species play a key role in the oxidation capacity of the polar troposphere,...
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