L'impact sur le climat et sur la qualité de l'air des gaz émis par les activités humaines a de fortes retombées sociales et économiques. L'ozone (O3) troposphérique est produit à partir des polluants primaires comme les oxydes d'azote. Il est le troisième gaz par importance dans l'effet de serre après le dioxyde de carbone et le méthane, et il est l'un des polluants principaux pour ses effets oxydants sur les tissus organiques. Pour répondre au besoin de mesure continue de la concentration d'O3 plusieurs satellites emportent des sondeurs capables de mesurer leur signal dans les domaines ultra-violet, visible ou infrarouge du rayonnement terrestre. Le CNES développe notamment le sondeur infrarouge IASI à bord des satellites météorologiques polaires METOP. IASI, en orbite depuis de nombreuses années, permet d'estimer la concentration de certains gaz atmosphériques, notamment l'O3, avec une couverture spatio-temporelle jamais atteinte jusqu'à présent. Chaque jour IASI mesure le spectre infrarouge de l'atmosphère entre 650 et 2700 nm avec une résolution horizontale de 12 km, ce qui fait un volume de données géolocalisées de plusieurs dizaines de gigaoctets par jour. Ces observations constituent un jeu de données idéal pour la validation des modèles de chimie-transport (CTM) à la base des systèmes de surveillance et de prévision de la qualité de l'air. Ces modèles peuvent prendre en compte les observations satellitaires par une procédure mathématique appelée 'assimilation de données'. Cette technique permet de compléter l'information parfois parcellaire des satellites (par exemple à cause de la présence des nuages ou durant la nuit pour les capteurs UV-visible) et d'obtenir des champs 3D globaux des concentrations de certaines espèces chimiques avec une fréquence horaire. Dans ce contexte, il est très important de développer des algorithmes fiables et efficaces pour assimiler les données IASI dans les CTM. A cette fin, l'UMR/CECI (CERFACS) développe en collaboration avec le CNRM/Météo-France un outil d'assimilation (VALENTINA) pour le CTM MOCAGE ayant des applications à l'échelle globale ou régionale pour l'étude du climat ou de la qualité de l'air, notamment dans le cadre du projet européen Copernicus sur la composition de l'atmosphère (CAMS). Il collabore également avec le Laboratoire d'Aérologie, qui développe depuis plusieurs années l'algorithme SOFRID de restitution des profils verticaux d' O3 IASI basé sur le code de transfert radiatif RTTOV. Le travail de cette thèse concerne la mise au point et la production d'analyses d' O3 troposphérique tridimensionnelles par l'assimilation d'observations satellitaires (MLS, IASI) dans le CTM MOCAGE. L'objectif principal est de constituer une nouvelle base de données pour l'étude de la variabilité de l'ozone de l'échelle journalière à celle décennale. On démontre ainsi la capacité des analyses utilisant les données IASI à reproduire la réponse de l' O3 troposphérique à l'ENSO (El Niño Southern Oscillation) aux basses latitudes, apportant notamment des informations nouvelles sur la distribution verticale des anomalies associées. Une large part de ce travail a de plus consisté à analyser les biais entre les analyses et les données de sondages indépendantes. Une des raisons expliquant ces biais pourrait être l'utilisation d'a-priori et de covariances d'erreurs climatologiques fortement biaisés (notamment au niveau de la tropopause) dans la procédure d'inversion des produits d' O3 de IASI. Une seconde partie de la thèse a donc consisté à mettre en place une méthode permettant de prescrire des a-priori plus proches des situations réelles améliorant ainsi les profils d' O3 restitués. En conclusion cette thèse constitue une avancée significative vers l'amélioration des produits d' O3 troposphérique issus de l'instrument IASI, permettant d'envisager un suivi à long terme que le caractère opérationnel des satellites METOP facilitera. / Human activity produces gases impacting the climate and the air quality with important economic and social consequences. Tropospheric ozone (O3) is created by chemical reactions from primary pollutants as nitrogen oxides. O3 is the third most important greenhouse gas after carbon dioxide and methane. It is one of the most important pollutants due to its oxidant effects on biological tissue. Several sensors on board satellites measure ozone concentration in the Ultraviolet, visible, or in the Earth infrared radiance. The French national center for space studies CNES (Centre National d'Etudes Spatiales) has developed the infrared sounding IASI on board polar meteorological satellites METOP. IASI, in orbit for several years, has allowed to estimate concentration of atmospheric gases, particularly O3, with a spatio-temporal coverage never reached so far. Every day, IASI measures infrared spectrum of the atmosphere between 650 to 2700 nm with an horizontal resolution of 12 km, giving tens of Gigaoctet per day of geolocated data. These observations form a part of an ideal set of data for the Chemistry Transport Model (CTM). CTM are used to analyze and predict air quality and can take into account satellite data according to a mathematical procedure called 'data assimilation'. This technic allows to fill gaps in the satellite information (for instance due to clouds or during night for the UV-visible sensor) and to obtain 3D global fields of chemical species concentration on an hourly basis. Therefore, it is important to develop accurate and efficient algorithms to assimilate IASI data in the CTM's. To this end, the UMR/CECI (CERFACS) develops in collaboration with the CNRM/Météo-France an assimilation tool (named VALENTINA) to the CTM MOCAGE that has applications on global and regional scales for climate or air quality study. The CTM MOCAGE is part of the European Copernicus project on the atmospheric composition (CAMS). In addition, the UMR/CECI collaborates with the Laboratoire d'Aérologie that has developed for several years the SOFRID algorithm for the vertical profiles retrieval of IASI ozone data based on the radiative transfer code RTTOV. The study of this PhD includes the tridimensional production of tropospheric ozone analysis with data assimilation (MLS, IASI) in the CTM MOCAGE, and on the ozone variability. Hence, we demonstrate the analysis ability to reproduce tropospheric ozone in response to ENSO, by bringing new informations on the vertical structure of associated anomalies. The PhD also focuses on the study of biases between analyses and independent ozone soundings. One of the main reasons could be due to the use of the climatological a-priori and matrix error covariance associated, strongly biased (particularly around the tropopause) in the retrieval method of IASI ozone data. Therefore, the second part of the PhD has consisted implementation of a method that generates accurate a-priori to improve retrieved ozone profiles. As a conclusion, this PhD brings a significant progress towards the improvement of tropospheric ozone products from IASI instrument, that should contribute to the long-term monitoring of tropospheric ozone thanks to the operational nature of METOP satellites.

The aim of this thesis is to examine the nature and characteristics of tropospheric ozone over Johannesburg, South Africa. Ozone, water vapour and meteorological profile data, which form part of the MOZAIC (Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft) database for the period 1995 to 2000 were utilized in this study. The thesis is divided into two main parts. The first part deals with the computation of total tropospheric ozone. A clear seasonal cycle, with ozone peaking in September and October is found. It is suggested that the main reason for the spring maximum is biomass burning, combined with prevailing anticyclonic circulation patterns, which facilitate the build-up of ozone over the region. Variability in TTO is greatest in January, September and November and least during autumn and winter (April to July). The lower day-to-day variability in autumn and winter is a reflection of the more settled weather at this time. Interannual variability is least in January and April to June. The autumn and winter ozone values are more consistent and appear to represent background tropospheric ozone loadings on which the dynamic and photochemical influences of other months are superimposed. High TTO events (>30 DU) occurred predominantly during September and October. Enhancements in the lower troposphere occurred mostly in September and seldom lasted for more than 1-2 consecutive days. It is suggested that these events are most likely due to effects of local surface pollution sources, either localised biomass burning or urban-industrial effects. An extended period of enhancement in the 7-12 km layer occurred from 14-17 September 1998 and again on 20 September 1998. The extended duration of this event suggests that it is due to an STE event. Confirmation of this was given in a case study of a particular MOZAIC flight on 16 September 1998 from Johannesburg to Cape Town. The second part of the thesis deals with the classification of ozone profiles and is used to find pattern and order within the profiles. TWINSPAN (Two-Way INdicator SPecies ANalysis), a cluster analysis technique, was used to classify the profiles according to the magnitude and altitude of ozone concentration. Six distinct groups of profiles have been identified and their characteristics described. The HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) trajectory model was used to relate the profiles to the origin of air masses, revealing clearly defined source regions. The mid-tropospheric peak in summer and the low to mid-tropospheric enhancement in spring is attributed to continental areas over central Africa and long-range transport while local sources are responsible for the winter low tropospheric enhancement. Reduced ozone values are due to westerlies bringing in clean maritime air. The classification has highlighted three important findings. Firstly, it has emphasized the pronounced seasonality of ozone profiles. It is evident that seasons are dominated by particular patterns and by inference, the processes and transport patterns that shape individual profiles are seasonally dependent. Secondly, the widely recognized spring maximum in tropospheric ozone has been confirmed in this classification, but a new and equally high summer mid-tropospheric enhancement due to the penetration of tropical air masses from continental regions in central Africa has been identified. Thirdly, it is suggested that the computation of a mean profile and furthermore, extrapolation of trends based on a mean profile is meaningless, particularly for a location on the boundaries of zonally defined meteorological regimes. / Thesis (M.A.)-University of Natal, Durban, 2002.

No description available.

During ferrochrome (FeCr) production, three types of generic chromium (Cr) containing wastes are generated, i.e. slag, bag filter dust (BFD) and venturi sludge. The loss of these Cr units contributes significantly to the loss in revenue for FeCr producers. In this study, the liberation of Cr units was investigated utilising two case study waste materials, i.e. BFD from a semi-closed submerged arc furnace (SAF) operating on acid slag and the ultrafine fraction of slag (UFS) originating from a smelter operating with both open and closed SAFs on acid slag. A detailed material characterisation was conducted for both case study materials, which included particle size distribution, chemical composition, chemical surface composition and crystalline content. Cr liberation was achieved utilising two methods, i.e. aqueous ozonation and the advanced oxidation method. Various advanced oxidation processes could be applied. However, the advanced oxidation processes considered in this study was the use of gaseous ozone (O3) in combination with hydrogen peroxide (H2O2). Controlling parameters such as the influence of pH, ozonation contact time, waste material solid loading, gaseous O3 concentration and temperature on Cr liberation were investigated for the aqueous ozonation process. The influence of pH, volume H2O2 added and the method of H2O2 addition were considered for the advanced oxidation process. Results indicated that with aqueous ozonation, limited Cr liberation could be achieved. The maximum Cr liberation achieved was only 4.2% for BFD by varying the process controlling parameters. The Cr liberation for UFS was significantly lower than that of the BFD. The difference in the results for the two waste materials was attributed to the difference in characteristics of the materials. The Cr content in BFD was mostly related to chromite and/or altered chromite particles, while the Cr content of the UFS was mostly related to FeCr particles. It is possible that the Cr(III) present in the chromite and/or partially altered chromite might be more susceptible to oxidation to Cr(VI) than the metallic Cr(0) present in the FeCr. During ozonation, aqueous O3 spontaneously decomposes to form hydroxyl (OH•) radicals, which are very strong oxidants in water. The above-mentioned Cr liberation observed was related to the formation of the OH• radicals during the spontaneous decomposition of aqueous O3. This was indicated especially by enhanced Cr liberation at higher pH values, which was attributed to the acceleration of the spontaneous decomposition to OH• radicals at higher pH levels. The advanced oxidation method gave significantly higher Cr liberation results for both case study materials considered, achieving Cr liberations of more than 21%. The advance oxidation processes improve normal oxidation methods. In this study, the H2O2 used in combination with O3 enhanced the formation of the OH• radicals that are responsible for the oxidation of Cr. The Cr liberation levels achieved are possibly not high enough to be feasible for industrial purposes. However, a further investigation of the advanced oxidation process could optimise the process to yield even higher Cr liberation. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2014

During ferrochrome (FeCr) production, three types of generic chromium (Cr) containing wastes are generated, i.e. slag, bag filter dust (BFD) and venturi sludge. The loss of these Cr units contributes significantly to the loss in revenue for FeCr producers. In this study, the liberation of Cr units was investigated utilising two case study waste materials, i.e. BFD from a semi-closed submerged arc furnace (SAF) operating on acid slag and the ultrafine fraction of slag (UFS) originating from a smelter operating with both open and closed SAFs on acid slag. A detailed material characterisation was conducted for both case study materials, which included particle size distribution, chemical composition, chemical surface composition and crystalline content. Cr liberation was achieved utilising two methods, i.e. aqueous ozonation and the advanced oxidation method. Various advanced oxidation processes could be applied. However, the advanced oxidation processes considered in this study was the use of gaseous ozone (O3) in combination with hydrogen peroxide (H2O2). Controlling parameters such as the influence of pH, ozonation contact time, waste material solid loading, gaseous O3 concentration and temperature on Cr liberation were investigated for the aqueous ozonation process. The influence of pH, volume H2O2 added and the method of H2O2 addition were considered for the advanced oxidation process. Results indicated that with aqueous ozonation, limited Cr liberation could be achieved. The maximum Cr liberation achieved was only 4.2% for BFD by varying the process controlling parameters. The Cr liberation for UFS was significantly lower than that of the BFD. The difference in the results for the two waste materials was attributed to the difference in characteristics of the materials. The Cr content in BFD was mostly related to chromite and/or altered chromite particles, while the Cr content of the UFS was mostly related to FeCr particles. It is possible that the Cr(III) present in the chromite and/or partially altered chromite might be more susceptible to oxidation to Cr(VI) than the metallic Cr(0) present in the FeCr. During ozonation, aqueous O3 spontaneously decomposes to form hydroxyl (OH•) radicals, which are very strong oxidants in water. The above-mentioned Cr liberation observed was related to the formation of the OH• radicals during the spontaneous decomposition of aqueous O3. This was indicated especially by enhanced Cr liberation at higher pH values, which was attributed to the acceleration of the spontaneous decomposition to OH• radicals at higher pH levels. The advanced oxidation method gave significantly higher Cr liberation results for both case study materials considered, achieving Cr liberations of more than 21%. The advance oxidation processes improve normal oxidation methods. In this study, the H2O2 used in combination with O3 enhanced the formation of the OH• radicals that are responsible for the oxidation of Cr. The Cr liberation levels achieved are possibly not high enough to be feasible for industrial purposes. However, a further investigation of the advanced oxidation process could optimise the process to yield even higher Cr liberation. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2014

Master of Arts / Department of Economics / Wayne Nafziger / Although the ozone layer is vital to life on Earth, as a common resource it has been the subject of rational exploitation. With ozone depletion a global (rather than merely regional) problem, measures to address it have necessarily been international efforts. The international treaty that addressed ozone depletion, the Montreal Protocol (with its subsequent amendments), has widely been hailed as a success. However, the triumphs of the Montreal Protocol are inseparable from its Multilateral Fund, whose creation was a prerequisite for developing nations, including juggernauts China and India, to ratify the Protocol. Since its inception the Fund has supplied over $2.5 billion to initiatives that support the phase-out of ozone-depleting chemicals in developing nations. These projects have increasingly employed market mechanisms to achieve efficient results, and have generated positive profits for participating firms. Funded initiatives have included upgrading capital, educating maintenance workers, production buyouts, public awareness, and institutional strengthening. Aside from ensuring the success of the overall Protocol, this last item will likely be the Multilateral Fund’s most enduring legacy, as inherent shortcomings of the Fund have largely been attributed to its status as a pioneering financial mechanism. The Multilateral Fund has broken new ground in international environmental regulation and shown that success on ecological issues is indeed possible at the global level, leading many to hope that the Fund will serve as a model for future mechanisms to address climate change. While the more complex chemistry and economics of climate change make such a ready duplication of the Multilateral Fund’s success unlikely, the Fund’s role in strengthening institutions that address ecological concerns has undoubtedly smoothed the way for future international environmental action.

Thesis (MSc)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Biofouling of water systems is a problem extensively experienced in industry. Although this subject is the focus of many studies, the ability of microorganisms to survive exposure to biocides is still poorly understood. This study aimed to assess the biocidal effect of ozone on planktonic cells and biofilm communities, to evaluate different ozone generation techniques, and to follow population shifts within the biofilm community. Specific objectives included determining the effect of different ozone concentrations, the effect of different exposure times, and an assessment of microbial responses after exposure to sub-lethal ozone concentrations. Typically, 300 ml of an ovemight bacterial culture was exposed to ozone that was generated by anodic oxidation (0.3% wt or 18- 20% wt, respectively) or silent electric discharge (3.5% wt 03). The ozone was purged into the culture for 5-, 7-, 10- and 15 min., respectively. Enumeration of cells following ~10 min. exposure to 18-20% wt ozone showed a significant reduction in viable cell numbers. In contrast, when exposed to the two lower 03 concentrations, there was little change in the viable cell numbers even after prolonged exposure (30- and 60 min.). To evaluate biofilms, ozone was bubbled into the irrigation that was pumped through replicate flow cell channels. Response to ozone exposure was evaluated after staining the biofilms with the Baclight Viability probe, observation with fluorescence microscopy, and image analysis. The higher ozone concentration (18-20% wt 03) more effectively disrupted the biofilm structure of denser biofilms than the lower concentration, especially after 90 min. exposure. When compared to the controls, the 90 min. exposure resulted in a notable reduction in viable cells from 69% to 38% and a corresponding increase in nonviable cells from 29% to 62%. The lower concentration ozone (3.5% wt 03) was effective against the less dense, thinner biofilms evaluated, but not effective against the thicker biofilm. An analysis of the differences between continuous culture biofilms and batch culture biofilms showed that the biofilms in the batch system were less rigid. To evaluate microbial response to biocides, techniques such as Biolog whole-community metabolic profiles and terminal restriction fragment length polymorphisms (T-RFLP) were used. Biolog analysis of planktonic cells revealed changes following exposure to sub-lethal biocide concentrations, however carbon utilisation profiles resembled that of the controls after 24-48 hours. For biofilm communities, no carbon utilization differences could be detected under these conditions. There was, however differences in T-RFLP patterns between treated and untreated biofilm communities. / AFRIKAANSE OPSOMMING: Biobevuiling van watersisteme is 'n probleem wat algemeen in industriëe ervaar word. Alhoewel hierdie onderwerp die fokus van vele studies is, word die vermoëns van mikroorganismes om blootstelling aan biosiede te weerstaan steeds swak verstaan. Die doel van hierdie studie was om die biosidiese effek van osoon op planktoniese selle en biofilm gemeenskappe waar te neem, om die verskillende osoon generasie tegnieke te evalueer, asook om verskuiwings in die samestelling van die biofilm gemeenskap waar te neem. Spesifieke doelwitte sluit in die bepaling van die effek van verskillende osoon konsentrasies, die blootstellingtye, en 'n waarneming van mikrobiese reaksies na blootstelling aan sub-dodings osoon konsentrasies. Drie honderd ml van 'n oornag bakteriese kultuur was aan osoon, wat deur anodiese oksidasie (0.3% wt of 18% - 20% wt) of geluidlose elektriese ontlading (3.5% wt), gegenereer is, blootgestel. Tye van blootstelling was 5-, 7-, 10-, of 15 min., onderskeidelik. Bepaling van selgetalle na :2:10 min. blootstelling aan 18 - 20% wt osoon, het 'n betekenisvolle verlaging in die getal lewensvatbare mikrobeselle getoon. In teenstelling hiermee, het blootstelling aan twee laer osoon konsentrasies min verskil in die lewensvatbare selgetalle, selfs na verlengde blootstellingstye (30- en 60 min.), getoon. Om biofilms te evalueer is osoon in die medium geborrel wat deur replikaat vloeisel kanale gepomp is. Na osoon blootstelling, was die vloeisel onderwerp aan beeld analise deur gebruik te maak van die Baclight lewensvatbare peiler en fluoressensie mikroskopie. Die hoër osoon konsentrasie (18 - 20% wt 03) het die struktuur van dikker biofilms meer effektiefuiteengeskeur as die laer konsentrasie, veral na 90 min. blootstelling. In vergelyking met die onderskeie kontroles, het die getalle van lewensvatbare selle na 90 min. blootstelling drasties verlaag vanaf 69% tot 38% en 'n ooreenstemmende toename in die nie-lewensvatbare selgetalle vanaf 29% tot 62%. Die laer osoon konsentrasie (3.5% wt 03) was meer effektief teenoor die minder digte en dunner biofilms wat ge-evalueer was, maar nie so effektief teenoor die dikker biofilms nie. 'n Analise van die verskille tussen kontinue-kultuur biofilms en lotkultuur biofilms het getoon dat die lot-kultuur biofilms minder rigied is. Vir die evaluering van mikrobiese reaksies na biosied blootstelling, is tegnieke soos Biolog gemeenskap metaboliese profiele en eind-restriksie-fragment-lengte polimorfisme (TRFLP) gebruik. Biolog analise van planktoniese selle het verskille getoon na blootstelling aan sub-dodelike biosied konsentrasies. Koolstof benutting het wel na 24 - 48 ure met dit van die kontrole ooreengestem. Vir biofilm gemeenskappe was daar geen noemenswaardige verskille in koolstof benutting nie. Daar was wel verskille in T-RFLP patrone tussen die onbehandelde en biosied-behandelde biofilm gemeenskappe.

Indoor sources of air pollution generate a large fraction of overall human exposure to airborne pollutants. Materials used in buildings have been shown to be a major contributor to indoor air pollution, with green building agencies setting guidelines limiting their primary emissions. However, such guidelines neglect secondary emissions resulting from chemistry occurring in indoor spaces. Furthermore, limited knowledge exists regarding ozone reactions and green building materials. This study focuses on the primary aldehyde emissions, ozone deposition velocity, and secondary emissions from three green building materials: recycled carpet, sustainable ceiling tile, and low-VOC paint and primer on recycled drywall. Ozone reactions resulted in secondary aldehyde emissions ranging from no increased secondary emissions to 237 µg m-2 hr-1. Modeling results suggest that these emissions can cause concentration increases beyond odor thresholds. / text

<p align='justify'>De manière à mieux comprendre l'impact des émissions anthropiques sur la troposphère reculée, les concentrations d'un nombre important de composés atmosphériques ont été mesurés dans la troposphère libre au-dessus d'Hawaii durant la campagne Mauna Loa Observatory Photochemistry Experiment (MLOPEX) accomplie au cours des années 1991 et 1992. Le constituant chimique fondamental pour évaluer cet impact est le radical hydroxyle OH qui fut mesuré au printemps et en été de l'année 1992. La variation diurne de la direction du vent génère pendant la journée un mélange des masses d'air de la couche limite planétaire avec la troposphère libre. Actuellement les modèles régional et global de chimie troposphérique ne peuvent tenir compte à la fois du transport à grande échelle et du mélange local. Nous avons développé un modèle tridimensionnel qui nous permet d'analyser la chimie et la dynamique troposphérique à ces deux échelles. Pour ce faire, nous avons utilisé une grille non-structurée qui offre un moyen efficace de caractériser la région d'Hawaii à l'aide d'une haute résolution et le restant de l'hémisphère Nord avec une résolution qui décroît au fur et à mesure que l'on s'éloigne d'Hawaii. La distribution de 46 composés gazeux avec 138 réactions, incluant une chimie détaillée des hydrocarbures non-méthaniques (isoprène, éthane, éthène, propène et alpha-pinène) est calculée avec un pas de temps de 20 minutes. A l'aide de notre modèle nous avons simulé une période de huit jours pour chacune des saisons. Les résultats des simulations ont été comparés aux observations et interprétés à l'aide d'études de rétro-trajectoires, de traceurs passifs et de bilans chimiques local et régional de l'ozone et de ses précurseurs.</p>

No description available.