Thesis (Ph. D.)--University of Denver, 1985. / Includes bibliographical references (leaves 247-266).

Le blanchiment est toujours l’un des points critiques en termes d’impact environnemental lors de la production de pâte de bois. Une nouvelle séquence « propre » de blanchiment sans réactifs chlorés (TCF) et à base d’ozone a permis d’obtenir une pâte à dissoudre blanchie dont les propriétés sont semblables à celles de pâtes blanchies par des séquences conventionnelles ECF à base de dioxyde de chlore. Il est montré que la pâte TCF a une meilleure stabilité de blancheur que la pâte ECF correspondante. Les phénomènes de jaunissement dont les mécanismes sont toujours mal compris ont été étudiés en mettant en œuvre diverses méthodes dont la spectroscopie RPE et la spectroscopie UV Raman et l’analyse des groupements carbonyle et carboxyle par fluorescence. Les groupes carbonyle que peut porter la cellulose se sont montrés néfastes pour la stabilité de la pâte, à la fois dans les conditions d’un vieillissement accéléré et en conditions alcalines de mercerisation. Ils peuvent néanmoins être partiellement éliminés par un traitement alcalin, ce qui se traduit par une meilleure stabilité de blancheur. L’addition de peroxyde d’hydrogène dans ce traitement permet d’obtenir des résultats encore meilleurs, sans élimination supplémentaire des carbonyles. Il aurait pour effet d’éliminer des chromophores résiduels de type quinonique et ayant un très fort impact sur le jaunissement des pâtes. La pâte TCF possèderait moins de chromophores quinoniques qu’une pâte ECF. / Bleaching of wood pulp is still an environmental issue. A new ozone-based TCF bleaching sequence made it possible to produce a bleached dissolving pulp whose properties were comparable to those of a pulp bleached with a conventional bleaching sequence using chlorine dioxide (ECF). It was noticed that the TCF bleached pulp had better brightness stability. The origin of yellowing is still poorly understood. It was studied here by the implementation of several analytical methods including EPR spectroscopy, UVRaman spectroscopy and also fluorescence spectroscopy for the specific analysis of carbonyl and carboxyl groups. It was shown that the carbonyl groups present on the cellulose are detrimental to the brightness stability, both during accelerated ageing and mercerization. They can be partly eliminated by an alkaline treatment, which improves the brightness stability. Addition of hydrogen peroxide allows for a further increase of the brightness stability, but without any extra carbonyl removal. It would have an effect on some conjugated residual chromophores, mainly quinones, involved in the yellowing mechanism. The TCF pulp would possess less quinones than a ECF pulp.

L'ozone troposphérique (O3) est un gaz à effet de serre et un polluant atmosphérique majeur. Il est la source principale du radical hydroxyle OH, l'oxydant le plus important dans l'atmosphère, fortement réactif avec les composés organiques et inorganiques. Les concentrations globales d'ozone troposphérique ont augmenté considérablement depuis l'époque pré-industrielle en raison de l'accumulation des émissions anthropiques de précurseurs d'ozone. Mon travail de thèse consiste à étudier la variabilité spatiale et temporelle de l'ozone troposphérique aux échelles globale et régionale telle qu'elle est mesurée par le sondeur IASI (Infrared Atmospheric Sounding Interferometer). Deux instruments IASI ont été lancés à bord des satellites MetOp-A et MetOp-B en 2006 et 2012.La première partie de mon travail consiste en l'étude des mesures O3/IASI: sa sensibilité dans la troposphère, sa variabilité saisonnière et ses modes de transport. Le deuxième volet de mon travail de thèse repose sur des études ciblées. Celles-ci comprennent une première étude sur l'ozone, urbain et rural, et sa relation complexe avec le dioxide d'azote (NO2) mesuré depuis l'espace par GOME-2 (Global Ozone Monitoring Experiment) au-dessus de différentes villes de l'hémisphère nord. Une deuxième étude s'attache à expliquer la source des pics d'ozone observés en région méditerranéenne en été, en utilisant IASI et le modèle de chimie-transport WRF-Chem (Weather Research and Forecasting model coupled with Chemistry). Enfin, en utilisant ces deux jeux de données, je présente en troisième étude l'analyse de la mousson d'été en Asie de l'Est ainsi que son effet sur l'ozone troposphérique. / Tropospheric ozone (O3) is an important greenhouse gas and air pollutant. It is the primary source of the most important oxidant in the atmosphere, the hydroxyl radical OH, that is highly reactive with organic and inorganic compounds. Global tropospheric O3 concentrations have been rising considerably since pre-industrial times as a result of the increase in the anthropogenic emissions of O3 precursors. In this thesis, I will study the temporal and spatial variability of tropospheric O3 on a global and regional scale as measured by IASI (Infrared Atmospheric Sounding Interferometer). The IASI instruments have been launched on-board the MetOp-A and MetOp-B satellites in 2006 and 2012.I first discuss the IASI/O3 measurements, their sensitivity in the troposphere and their seasonal variation and transport processes. I then perform more detailed and focused studies. Those include studying the urban and rural O3 and its relationship with nitrogen dioxyde (NO2) measured from GOME (Global Ozone Monitoring Experiment) over different cities in the Northern Hemisphere; investigating the summertime tropospheric O3 maxima over the Mediterranean region using IASI and the WRF-Chem (Weather Research and Forecasting model coupled with Chemistry) data; and finally, using both satellite and model data, I present my analysis of the East Asian monsoon variability and its effect on the tropospheric O3 column.

A fast response chemiluminescent ozone sonde originally intended for use as a balloon borne instrument, was deployed on a single engine light aircraft to determine mean ozone concentrations in the boundary layer downwind of a major urban centre. Vancouver is a coastal city at the mouth of a major river delta and valley walled in by mountains to the north and east. Hence, the pollutant distribution during anti-cyclonic conditions is influenced by the thermally induced flows of the sea/land breeze and mountain/valley wind systems. This study focused on ozone concentration in a steep walled, glacial valley near the city, where ozone concentrations had not been previously monitored but were suspected to be high. Measurements confirmed this hypothesis and the mass budget of ozone for the valley was calculated for a period shortly after sunrise when the rate of boundary layer growth was at its maximum. The high levels of ozone found in the valley were partly attributed to residual layer storage of ozone above the nocturnal stable layer. This overnight storage of ozone during sustained anti-cyclonic conditions suggests that the Pitt River valley and possibly other tributary valleys represent an important net sink for ozone emanating from precursor sources in the Lower Fraser Valley. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Networks of ground-based and satellite borne instruments to measure ultraviolet (UV) sunlight and total column ozone have greatly contributed to an understanding of increased amounts of UV reaching the surface of the Earth caused by stratospheric ozone depletion. Increased UV radiation has important potential effects on human health, and agricultural and ecological systems. Observations from these networks make it possible to monitor total ozone decreases and to predict ozone recovery trends due to global efforts to curb the use of products releasing chemicals harmful to the ozone layer. Thus, continued and expanded global monitoring of ozone and UV is needed. However, existing automatic stratospheric ozone monitors are complex and expensive instruments. The main objective of this research was the development of a low-cost fully automated total column ozone monitoring instrument which, because of its affordability, will increase the number of instruments available for ground-based observations. The new instrument is based on a high-resolution fiber optic spectrometer, coupled with fiber optics that are precisely aimed by a pan and tilt positioning mechanism and with controlling programs written in commonly available software platforms which run on a personal computer. This project makes use of novel low-cost fiber optic spectrometer technology. A cost advantage is gained over available units by placing one end of the fiber outdoors to collect sunlight and convey it indoors, thereby allowing the spectrometer and computer to be placed in a controlled environment. This reduces the cost of weatherproofing and thermal compensation. Cost savings also result from a simplified sun targeting system, because only a small pan and tilt device is required to aim the lightweight fiber optic ends. Precision sun-targeting algorithms, optical filter selection, and software to derive ozone from spectral measurements by the spectrometer are a major contribution of this project. This system is a flexible platform which may be adapted to study other atmospheric constituents such as sulfur dioxide, nitrous oxides, and haze.

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

Ozone is a known pollutant harmful to human health and a strong oxidizer. The use of Zero Energy Air Purification (ZEAP) materials has proven to be a viable option to reduce indoor ozone concentrations during short-term experiments. The current study focuses on activated carbon mats, and three green building materials (perlite-based ceiling tile, recycled carpet, and painted gypsum wallboard. The effects of long-term exposure of these materials to real environments on ozone removal capability, primary emissions (in absence of ozone) of carbonyls and secondary emissions of carbonyls following the use of ozone were studied. A field study was completed over a six-month period and laboratory testing was intermittently conducted on material samples. The results show sustained ozone removal capability for all materials except carpet. Carbonyl emissions are low for activated carbon in all field locations. Painted gypsum wallboard and perlite-based ceiling tile have similar overall emissions over the six-month period, but distributed differently in time, while carpet has large initial emission rates that decline rapidly but remain high compared to the other materials. This study confirms that activated carbon mats are a viable ZEAP material and that perlite-based ceiling tile could also be considered as such as it balances good ozone removal capability and low by- product emissions. / text

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