Photolysis of frozen iodate salts as a source of active iodine in the polar environment
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...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-10-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/16/12703/2016/acp-16-12703-2016.pdf |
| Summary: | 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 750 cm<sup>−1</sup> has been measured to be
<i>A</i> = 9.8 ± 0.5 × 10<sup>−17</sup> cm molecule<sup>−1</sup>. The
photolysis rate of the ammonium iodate salt was measured by monitoring the
decay of ammonium or iodate IR bands (1430 and 750 cm<sup>−1</sup> 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 400 nm) 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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| ISSN: | 1680-7316 1680-7324 |