INFUSO Maxime: Unraveling the atmospheric iodine chemistry using molecular simulations.

Abstract: The goal is to improve the understanding of the heterogeneous reactivity between gaseous iodinated species and aerosols present in the troposphere. To date, these heterogeneous interactions have been considered in the atmospheric iodine dispersion models in case of a severe nuclear power plant accident. This is a case of such heterogeneous reactivity may play a major role in the iodine transport far from their emission sources. The importance of iodine in atmospheric chemistry has been highlighted by recent reviews. However, the atmospheric iodine heterogeneous reactivity studies have been exclusively determined by the uptake coefficient of inorganic iodinated compounds (for example, I2, HI, and HOI) by water or ice. These conditions are not fully relevant for our applications and have to be extended. Furthermore, photo-oxidation of gaseous CH3I and I2 in the presence of O3 is known to produce IxOy aerosols, which are measured in the field campaigns. To the best of our knowledge, the influence of aerosols on the iodine photolysis processes is not documented. Finally, the field measurements in Arctic and Antarctica pointed out the role of the low temperature in iodine chemistry in gas phase and in the formation of iodine-rich aerosols.As a result, this thesis will provide a set of reliable kinetic and mechanistic data. Iodine reactivity with atmospheric aerosols in order to improve the relevance and accuracy of iodine chemistry in dispersion models. The work will be based on molecular simulations. Systems associating both the iodinated gaseous species and the representative atmospheric aerosols will be carefully selected. Both molecular iodine (I2) and iodomethane (CH3I) are key iodine compounds of marine and biogenic origin that appear to be of central importance in understanding iodine chemistry in the troposphere. Further, in addition to their atmospheric interest, the reactivity of the compounds in the field of nuclear safety are the most probable gaseous iodine species to be released to the troposphere during a severe nuclear power plant accident of the type in Fukushima, Japan. As a result, this work will start on the molecular basis and iodomethane surface reactivity as a function of key inorganic and organic aerosols classes from the nanometric up to micrometric size. The invention is intended to provide a method for the treatment of water and alkaline salts, and

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Thesis director: DUFLOT Denis
Co-directors: TOUBIN Céline et LOUIS Florent (PC2A)