The photohydrodebromination of brominated paracyclophanes was studied to help elucidate the possible mechanistic pathways leading to product for bromoarenes in general. Several brominated [2.2]paracyclophanes were studied to determine the effect of substitution patterns on this reaction. [2.2]Paracyclophanes were chosen for this study in order to investigate possible intramolecular excimer formation as a route to product formation. The [2.2]paracyclophanes studied were 4-bromo-, pseudo-para-dibromo-, and pseudo-ortho-dibromo[2.2]paracyclophane. 5-Bromo[3.3]paracyclophane has also been studied to determine the effect of increased ring separation on the reaction. These brominated cyclophanes showed varying efficiencies of both intermolecular and intramolecular excimer formation. / Graduation date: 1993

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Thesis (Ph.D.) -- McMaster University, 2002. / Includes bibliographical references (leaves 154-163). Also available via World Wide Web.

Thesis (M. Sc)--York University, 2000. Graduate Programme in Physics and Astronomy. / Typescript. Includes bibliographical references (leaves 128-135). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pMQ59206.

We derive tropospheric column BrO during the ARCTAS and ARCPAC field campaigns in spring 2008 using retrievals of total column BrO from the satellite UV nadir sensors OMI and GOME-2 using a radiative transfer model and stratospheric column BrO from a photochemical simulation. We conduct a comprehensive comparison of satellite-derived tropospheric BrO column to aircraft in-situ observations of BrO and related species. The aircraft profiles reveal that tropospheric BrO, when present during April 2008, was distributed over a broad range of altitudes rather than being confined to the planetary boundary layer (PBL). Perturbations to the total column resulting from tropospheric BrO are the same magnitude as perturbations due to longitudinal variations in the stratospheric component, so proper accounting of the stratospheric signal is essential for accurate determination of satellite-derived tropospheric BrO. We find reasonably good agreement between satellite-derived tropospheric BrO and columns found using aircraft in-situ BrO profiles, particularly when satellite radiances were obtained over bright surfaces (albedo >0.7), for solar zenith angle <80 degree and clear sky conditions. The rapid activation of BrO due to surface processes (the bromine explosion) is apparent in both the OMI and GOME-2 based tropospheric columns. The wide orbital swath of OMI allows examination of the evolution of tropospheric BrO on about hourly time intervals near the pole. Low surface pressure, strong wind, and high PBL height are associated with an observed BrO activation event, supporting the notion of bromine activation by high winds over snow. We also provide monthly climatological maps of free tropospheric BrO volume mixing ratio (VMR) derived using the so-called cloud slicing technique. In this approach, the derived slope of the total column BrO versus cloud pressure is proportional to free tropospheric BrO VMR. Estimated BrO VMR shows a minimum in the tropics and greater values at higher latitudes in both hemispheres. High tropospheric BrO VMR at high latitudes in spring could be influenced by near-surface bromine activation.

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Thesis (DTech (Environmental Health))--Cape Peninsula University of Technology, 2011. / This study was aimed to provide baseline information about the environmental levels of selected PBDEs (BDE 28, 47, 100, 99, 154, 153, 183 & 209) and BB 153 in different matrices, including wastewater treatment plants' effluent, sludge, landfill leachate, river water and bottom sediment samples from different locations within the City of Cape Town. The monitoring of these contaminants was carried out bi-monthly over an extended period of 12 months beginning from April 2010 to March 2011. In this study, a total of 63, 168, 312, 93 and 108 samples for leachate, wastewater treatment plant (WWTP) sludge, effluent, river water and bottom sediment, respectively were collected from three landfill sites, four WWTPs and two rivers within the City of Cape Town. The aqueous matrices were extracted using a liquid-liquid extraction technique. The extraction of both sediment and sludge samples were performed using mechanical shaking and soxhlet extraction techniques, respectively. Extract obtained were further purified using multi-layer silica gel column chromatographic technique. The routine analysis of these target compounds was carried out using a gas chromatograph equipped with an electron capture detector (GC-µECD). However, the structural elucidation of these compounds was performed with a gas chromatography-time of flight-mass spectrometry (GC-TOF-MS) instrument.

Bromine compounds play an important role as catalyst of the ozone destruction in both the stratosphere and troposphere. While the impact of bromine species on the chemistry of the stratosphere is known to a large extend, a number of uncertainties remain regarding the sources and sinks of atmospheric bromine as well as the chemistry and impact of bromine species on the troposphere. <p>This work describes remote-sensing observations of bromine monoxide (BrO) derived from scattered sunlight spectra in the ultraviolet region measured by ground-based multi-axis and satellite nadir viewing instruments (GOME and GOME-2). The method of differential optical absorption spectroscopy is used to retrieve the columnar concentration of BrO along the effective light path through the atmosphere. New algorithms to derive vertical columns of BrO resolved into their stratospheric and tropospheric contributions are developed and described. For the ground-based geometry a way was found to determine independently the stratospheric and tropospheric BrO columns from the diurnal variation of the BrO measurements. For the satellite observations, the contribution of the stratospheric BrO to the measured column is estimated using an innovative stratospheric BrO climatology. This climatology is based on a state-of-the-art stratospheric chemical transport model, and explicitly accounts for the impact of atmospheric dynamics and photochemistry on the stratospheric BrO distribution. As for the tropospheric fraction of the measured total BrO column, it is derived using a residual technique accounting for the effects of clouds and surface reflectivity. <p>Supported by an extensive set of correlative data, the results presented here allow to study properly the spatial and temporal evolution of atmospheric BrO at the global scale and enable to better assess the significance of BrO in the polar planetary boundary layer and free-troposphere as well as the contribution from very short-lived brominated sources gases to the stratospheric bromine budget. We also report on the first satellite detection of BrO in a volcanic plume, using GOME-2 measurements.<p><p><p><p>Les composés bromés jouent un rôle important dans la stratosphère et la troposphère en tant que catalyseurs de la destruction d’ozone. Bien que l’impact des espèces bromées sur la chimie de la stratosphère soit largement compris, il reste de nombreuses incertitudes en ce qui concerne les sources et les pertes de brome dans l’atmosphère ainsi qu’à propos de la chimie et de l’impact des espèces bromées sur la troposphère.<p>Le travail présenté dans ce manuscrit porte sur la télédétection du monoxyde de brome (BrO) à partir de spectres du rayonnement solaire diffusé, mesurés dans l’ultraviolet à partir d’instruments au sol de type multi-axis et satellitaires à visée nadir (GOME et GOME-2). La méthode de spectroscopie d’absorption optique différentielle est utilisée pour inverser la colonne intégrée de BrO le long du chemin optique effectif dans l’atmosphère. Nous avons développé de nouveaux algorithmes afin de dériver les colonnes verticales de BrO résolues en leurs contributions stratosphérique et troposphérique. Pour la géométrie d’observation au sol, un moyen a été trouvé pour déterminer indépendamment les colonnes de BrO stratosphérique et troposphérique, et cela à partir de la variation diurne des mesures de BrO. Pour les observations satellitaires, la contribution de la stratosphère à la colonne mesurée de BrO est estimée à partir d’une climatologie innovante de BrO stratosphérique. Cette climatologie est basée sur un modèle de pointe de la chimie et du transport de la stratosphère; par ailleurs, elle tient compte explicitement de l’impact de la dynamique atmosphérique et de la photochimie sur la distribution du BrO dans la stratosphère. La fraction troposphérique de la colonne totale mesurée de BrO est quant à elle dérivée à partir d’une technique résiduelle tenant compte des effets des nuages et de la réflectivité de la surface. <p>Soutenus par un vaste jeu de données corrélatives, les résultats présentés dans ce travail permettent d’étudier de manière appropriée l’évolution spatiale et temporelle du BrO atmosphérique à l’échelle globale. Ces résultats permettent également de mieux estimer l’importance du BrO dans la couche limite planétaire polaire et dans la troposphère libre ainsi que la contribution des précurseurs bromés à temps de vie court sur le budget de brome dans la stratosphère. Nous présentons également la première détection satellitaire de BrO dans un panache volcanique, à l’aide de mesures effectuées avec l’instrument GOME-2. <p> / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished