Modelling iodide - Iodate speciation in atmospheric aerosol: Contributions of inorganic and organic iodine chemistry

Pechtl, S., Schmitz, G. and von Glasow, R. (2007) Modelling iodide - Iodate speciation in atmospheric aerosol: Contributions of inorganic and organic iodine chemistry. Atmospheric Chemistry and Physics, 7 (5). pp. 1381-1393.

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Abstract

The speciation of iodine in atmospheric aerosol is currently poorly understood. Models predict negligible iodide concentrations but accumulation of iodate in aerosol, both of which is not confirmed by recent measurements. We present an updated aqueous phase iodine chemistry scheme for use in atmospheric chemistry models and discuss sensitivity studies with the marine boundary layer model MISTRA. These studies show that iodate can be reduced in acidic aerosol by inorganic reactions, i.e., iodate does not necessarily accumulate in particles. Furthermore, the transformation of particulate iodide to volatile iodine species likely has been overestimated in previous model studies due to negligence of collision-induced upper limits for the reaction rates. However, inorganic reaction cycles still do not seem to be sufficient to reproduce the observed range of iodide – iodate speciation in atmospheric aerosol. Therefore, we also investigate the effects of the recently suggested reaction of HOI with dissolved organic matter to produce iodide. If this reaction is fast enough to compete with the inorganic mechanism, it would not only directly lead to enhanced iodide concentrations but, indirectly via speed-up of the inorganic iodate reduction cycles, also to a decrease in iodate concentrations. Hence, according to our model studies, organic iodine chemistry, combined with inorganic reaction cycles, is able to reproduce observations. The presented chemistry cycles are highly dependent on pH and thus offer an explanation for the large observed variability of the iodide – iodate speciation in atmospheric aerosol.

Item Type: Article
Additional Information: © Author(s) 2007. This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 License.
Faculty \ School: Faculty of Science > School of Environmental Sciences
UEA Research Groups: Faculty of Science > Research Groups > Volcanoes@UEA (former - to 2018)
Faculty of Science > Research Groups > Marine and Atmospheric Sciences (former - to 2017)
Faculty of Science > Research Groups > Meteorology, Oceanography and Climate Dynamics (former - to 2017)
Faculty of Science > Research Groups > Atmospheric Chemistry (former - to 2018)
Faculty of Science > Research Groups > Climate, Ocean and Atmospheric Sciences (former - to 2017)
Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences
Depositing User: Rosie Cullington
Date Deposited: 27 Feb 2011 11:08
Last Modified: 24 Oct 2022 01:28
URI: https://ueaeprints.uea.ac.uk/id/eprint/25166
DOI: 10.5194/acp-7-1381-2007

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