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The impact of halogen chemistry on important atmospheric processes such as ozone depletion and (potentially) climate regulation is becoming increasingly apparent. Yet only the most fundamental atmospheric chemistry of halogen species is included in global tropospheric models. Spectroscopic measurements of the concentration of halogen species within the Earth's atmosphere, and the accurate determination of kinetic information regarding the rates and mechanisms of chemical processes in the laboratory, greatly facilitate the evolution of our quantitative understanding of the atmospheric role of halogen species, ultimately leading to their inclusion in atmospheric chemistry models. The research presented in this thesis addresses previously un-investigated areas (or areas requiring further elucidation) of iodine chemistry. Specifically, Chapter Three uses new spectroscopic data to reassess the viability of a laser-induced fluorescence (LIF) instrument for the detection of ambient iodine monoxide radicals (10), a key species in the atmospheric chemistry of iodine, which may help to enhance our understanding of important atmospheric processes via its spatially resolved detection. Chapter Four presents a kinetic and spectroscopic investigation into the mechanism and products of the reaction of CH21 radicals with 02, which has potential implications for particle formation in the marine boundary layer (MBL). The reaction of Cl atoms with alkyl iodides, CH3I and CH212, has been studied in detail by the detection of adducts formed in these reactions, which have been observed by LIF for the first time, and is the subject of Chapter Five. As part of the course of this PhD, the reaction kinetics of the reaction of 10 with dimethyl sulphide (DMS) was investigated. The results obtained have led to a re-evaluation of the atmospheric significance of this reaction. The data obtained assist the development of our knowledge of the atmospheric chem istry of iodine species and, at a more fundamental level, the electronic structure and physical processes of gas phase species.

Afin d’éviter le relâchement d’iode 129 (déchet de moyenne activité à vie longue) dans l’environnement, un nouveau matériau incorporant l’iodate dans une hydroxyapatite phosphocalcique a été étudié. Deux méthodes de préparation de ce matériau ont été développées : élaboration par précipitation suivi d’un frittage SPS et élaboration par voie cimentaire. Une quantité pondérale d’iode (taux d’incorporation maximal de 10%mass.) est incorporé uniquement sous forme iodate dans la structure apatitique préparée à partir des deux méthodes d’élaboration. Un monolithe ayant un taux de densification de 88,6 % a été obtenu après mise en forme de poudres précipitées par frittage SPS. Ce matériau présente une résistance à la lixiviation satisfaisante, caractérisée par une vitesse d’altération initiale en eau pure à 50 °C de 10-2 g.m-2.j-1 (comparable à celle d’un verre R7T7 lixivié dans les mêmes conditions) et par une vitesse d’altération résiduelle à 50 °C de 10-5 g.m-2.j-1 dans l’eau souterraine d’un site potentiel de stockage. Dans l’ensemble, ce matériau est un candidat potentiel pour un conditionnement de l’iode radioactif. / In order to avoid the release of 129I (long-lived intermediate-level waste) in the environment, we describe a novel material incorporating iodate in a calcium phosphate based hydroxyapatite. This material is prepared by two synthetic processes: a wet precipitation route followed by a spark plasma sintering and a cementitious route. A high iodine content (with a maximum incorporation rate of 10 wt.%) is reached for both processes, by incorporation of the iodate in the apatitic structure. A monolith with relative density of 88.6% was obtained after shaping of the precipitated powders by spark plasma sintering. This material reveals satisfactory leaching properties, with an initial leaching rate in pure water at 50 °C of 10-2 g.m-2.j-1, and a residual leaching rate at 50 °C of 10-5 g.m-2.j-1 in underground water of potential geological repositories. All in all, this material is a potential candidate for the conditioning of radioactive iodine.