The baseline of uncertainty in aerosol radiative forcing is large and depends on aerosol characteristics (e.g. size and composition), which can vary significantly on a regional scale. Sources (natural and anthropogenic) can be directly linked to the aerosol characteristics of a region, making monitoring campaigns to determine aerosol composition in different regions very important. Limited data currently exists for atmospheric aerosol black carbon (BC) and organic carbon (OC) in South Africa. In this study, BC and OC concentrations were explored in terms of spatial and temporal patterns, mass fractions of BC and OC of the overall aerosol mass, as well as possible sources. Primary pollutants, of which BC is an example, are emitted directly from the source. Certain primary pollutants can react with other pollutants to form secondary pollutants. OC can either be a primary or secondary pollutant, e.g. formed by gas-to-particle conversion of volatile organic compounds (VOCs) in the atmosphere (nucleation and condensation of gaseous precursors). Greenhouse gases (GHG) and BC absorb terrestrial long wave radiation causing an increase of atmospheric temperature. In contrast, OC generally reflects incoming radiation, cooling the atmosphere. GHGs have a long residence time in the atmosphere (10 to 100 years), while the residence time of aerosols is usually only a week or more. The climatic effects of aerosols are therefore particularly important from a regional perspective. Aerosols are also important from an air quality perspective, especially since ultrafine particles (diameter smaller than 100nm) are small enough to go through the membranes of the respiratory tract and into the blood stream. They can then be transported to the brain. Up to 2005, DEBITS (Deposition of Biogeochemical Import Trace Species) activities in South Africa did not include aerosol measurements. In order to initiate aerosol monitoring, campaigns were launched during the 2005 to 2007 period. Additionally, OC and BC measurements for the PM10 and PM2.5 (particulate matter smaller than or equal to 10 and 2.5 μm, respectively) fractions were started in 2009. PM10 and PM2.5 samples were collected at five sampling sites in South Africa operated within the DEBITS network, i.e. Louis Trichardt, Skukuza, Vaal Triangle, Amersfoort and Botsalano, with MiniVol samplers. The selected sites are mostly located in rural areas, but with the surrounding atmosphere influenced by industries, transportation, biomass burning, etc. Winters are characterised by an increase in biomass burning (fires) and combustion for domestic use (cooking and space heating). Samples were analysed with a Thermal/Optical Carbon analyser (Desert Research Institute). OC and BC results showed that the total carbonaceous content decreased during the summer due to less biomass burning (fires). BC was the highest at the industrially influenced sites, while OC was highest at regional background sites. OC was higher than BC concentrations at all sites in both size fractions. Most OC and BC occurred in the PM2.5 fraction. OC/BC ratios reflected the setting of the different DEBITS sites, with sites in or close to anthropogenic source regions having the lowest OC/BC ratios, while background sites had the highest OC/BC ratios. The OC mass fraction percentage of the total aerosol weight varied up to 24% and the BC up to 12%. The highest OC mass fraction was found at Skukuza, which was attributed to both natural (lies within the savannah biome) and anthropogenic (dominant path of air mass movement from the anthropogenic industrial hub of South Africa) reasons. The highest mass fraction of BC was found in the Vaal Triangle, since it is situated within a well-known anthropogenic source region. Household combustion for space heating and cooking also seemed to make a significant contribution to BC at this site in the cold winter months. A relatively well-defined seasonal pattern was observed, with higher OC and BC concentrations measured from May to October, which coincides with the dry season in the interior of South Africa. Positive correlations between OC and BC concentrations with the distance back trajectories passed fires were observed, indicating that fires contribute significantly to both atmospheric OC and BC during the burning season. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014

The baseline of uncertainty in aerosol radiative forcing is large and depends on aerosol characteristics (e.g. size and composition), which can vary significantly on a regional scale. Sources (natural and anthropogenic) can be directly linked to the aerosol characteristics of a region, making monitoring campaigns to determine aerosol composition in different regions very important. Limited data currently exists for atmospheric aerosol black carbon (BC) and organic carbon (OC) in South Africa. In this study, BC and OC concentrations were explored in terms of spatial and temporal patterns, mass fractions of BC and OC of the overall aerosol mass, as well as possible sources. Primary pollutants, of which BC is an example, are emitted directly from the source. Certain primary pollutants can react with other pollutants to form secondary pollutants. OC can either be a primary or secondary pollutant, e.g. formed by gas-to-particle conversion of volatile organic compounds (VOCs) in the atmosphere (nucleation and condensation of gaseous precursors). Greenhouse gases (GHG) and BC absorb terrestrial long wave radiation causing an increase of atmospheric temperature. In contrast, OC generally reflects incoming radiation, cooling the atmosphere. GHGs have a long residence time in the atmosphere (10 to 100 years), while the residence time of aerosols is usually only a week or more. The climatic effects of aerosols are therefore particularly important from a regional perspective. Aerosols are also important from an air quality perspective, especially since ultrafine particles (diameter smaller than 100nm) are small enough to go through the membranes of the respiratory tract and into the blood stream. They can then be transported to the brain. Up to 2005, DEBITS (Deposition of Biogeochemical Import Trace Species) activities in South Africa did not include aerosol measurements. In order to initiate aerosol monitoring, campaigns were launched during the 2005 to 2007 period. Additionally, OC and BC measurements for the PM10 and PM2.5 (particulate matter smaller than or equal to 10 and 2.5 μm, respectively) fractions were started in 2009. PM10 and PM2.5 samples were collected at five sampling sites in South Africa operated within the DEBITS network, i.e. Louis Trichardt, Skukuza, Vaal Triangle, Amersfoort and Botsalano, with MiniVol samplers. The selected sites are mostly located in rural areas, but with the surrounding atmosphere influenced by industries, transportation, biomass burning, etc. Winters are characterised by an increase in biomass burning (fires) and combustion for domestic use (cooking and space heating). Samples were analysed with a Thermal/Optical Carbon analyser (Desert Research Institute). OC and BC results showed that the total carbonaceous content decreased during the summer due to less biomass burning (fires). BC was the highest at the industrially influenced sites, while OC was highest at regional background sites. OC was higher than BC concentrations at all sites in both size fractions. Most OC and BC occurred in the PM2.5 fraction. OC/BC ratios reflected the setting of the different DEBITS sites, with sites in or close to anthropogenic source regions having the lowest OC/BC ratios, while background sites had the highest OC/BC ratios. The OC mass fraction percentage of the total aerosol weight varied up to 24% and the BC up to 12%. The highest OC mass fraction was found at Skukuza, which was attributed to both natural (lies within the savannah biome) and anthropogenic (dominant path of air mass movement from the anthropogenic industrial hub of South Africa) reasons. The highest mass fraction of BC was found in the Vaal Triangle, since it is situated within a well-known anthropogenic source region. Household combustion for space heating and cooking also seemed to make a significant contribution to BC at this site in the cold winter months. A relatively well-defined seasonal pattern was observed, with higher OC and BC concentrations measured from May to October, which coincides with the dry season in the interior of South Africa. Positive correlations between OC and BC concentrations with the distance back trajectories passed fires were observed, indicating that fires contribute significantly to both atmospheric OC and BC during the burning season. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014

Philosophiae Doctor - PhD / The work of the International Defence and Aid Fund (IDAF) conducted between 1956 and 1991 gave rise to a collection of records that traverse 35 years of support work. As a solidarity organisation IDAF provided support to liberation movements in South Africa through their legal and welfare assistance programmes. Equally significant, IDAF also sought to highlight the oppressive machinery of the apartheid government through the deployment of their research, information and publications programmes as a way of creating awareness and ‘keeping the conscience of the world alive.’ When the administrative records of IDAF were relocated to South Africa, with the Mayibuye Centre for History and Culture as chosen location, they were turned into an archival collection which also became a memorial to IDAF’s resistance work located in the foremost anti-apartheid university and politically in a new project that intended to create a museum about apartheid. Later the collection was incorporated into the Robben Island Museum (RIM) through an agreement between the University of the Western Cape (UWC) and the Museum. The dissertation examines the cultural history and the political life of the IDAF archival collection and the processes through which it was made and continues to be remade.

Ce travail de recherche, réalisé dans le cadre du programme IDAF, est une contribution à l'étude des dépôts des constituants majeurs atmosphériques à la surface de la terre, en Afrique tropicale. Il concerne l'étude des concentrations atmosphériques des gaz azotés (ammoniac, dioxyde d'azote, acide nitrique), du dioxyde de soufre (SO2) et de l'ozone (O3) et leur dépôt sec en Afrique de l'Ouest et Centrale. Les gaz ont été mesurés sur une base mensuelle par la technique des capteurs passifs sur une période de dix ans (1998-2007) dans sept sites IDAF représentatifs d'un transect d'écosystèmes : savanes sèches - savanes humides - forêts. La validation et l'analyse de la base de données décennales des " gaz IDAF " a permis d'établir les niveaux de concentrations caractéristiques de chaque écosystème et d'étudier leurs évolutions moyennes mensuelles, saisonnières, annuelles et interannuelles sur le transect d'écosystèmes. Les flux de dépôt sec ont été estimés par la méthode inférentielle à partir des vitesses de dépôt sec calculées en utilisant le modèle " big-leaf " de Zhang et al. (2003b). Dans le modèle de dépôt, les conditions de surface et météorologiques spécifiques aux sites IDAF ont été adaptées puis validées pour être représentatives de ces sites et ont ainsi permis de simuler les vitesses de dépôt sec représentatives des grands écosystèmes. Les variations moyennes mensuelles, saisonnières et annuelles des flux de dépôt sec des gaz (NO2, HNO3, NH3, O3, et SO2) sont analysées dans l'objectif de réaliser un bilan de dépôt atmosphérique total (sec + humide) d'azote à l'échelle des écosystèmes africains. Le dépôt total d'azote est estimé respectivement à 6-9 kgN.ha-1.an-1, 7-10 kgN.ha-1.an-1 et 13 kgN.ha-1.an-1 en savanes sèches, en savane humides et en forêts, avec une contribution relative du dépôt sec sous forme gazeuse au dépôt total d'azote comprise entre 46 et 71% sur l'ensemble des écosystèmes. Un bilan émission-dépôt des composés azotés oxydés et réduits à l'échelle de chaque écosystème a été réalisé et a montré un flux d'émission totale de même ordre de grandeur que le dépôt moyen annuel d'azote pour les écosystèmes de savanes mais plus faible dans l'écosystème forestier. Enfin une analyse comparative entre les mesures IDAF de dépôt d'azote et, d'une part, le dépôt d'azote simulé par une analyse multi-modèle à l'échelle globale et d'autre part, avec les charges critiques d'eutrophisation existantes dans la littérature a permis une première évaluation de l'impact potentiel du dépôt total d'azote sur les écosystèmes tropicaux africains.

En Afrique de l'Ouest, la diminution brutale de la pluviométrie depuis les années 1970 s'est produite en concomitance avec une augmentation des dommages liés aux inondations. Si une accentuation de la vulnérabilité des populations est indéniable, la question d'une évolution de l'aléa pluviométrique en particulier des pluies les plus intenses reste posée - notamment dans un contexte où le réchauffement climatique devrait s'accompagner d'une intensification du cycle hydrologique globale. Cette thèse s'attache améliorer nos connaissances sur le régime de pluies extrêmes en Afrique de l'Ouest sous-documenté à l'heure actuelle dans les sciences du climat et de l'hydrologie opérationnelle. Le travail s'articule autour des trois objectifs: (i) fournir une vision régionale intégrée de l'organisation spatiale des extrêmes, (ii) étudier l'évolution du régime de précipitations extrêmes en lien avec la variabilité décennale des cumuls pluviométriques annuels, (iii) caractériser les extrêmes pluviométriques en produisant des cartes d'aléa pluviométrique et en étudiant les liens d'échelles entre les extrêmes de pluie à différents résolutions spatio-temporelles. On se base ici sur les données journalières des réseaux nationaux disponibles depuis les années 1950 sur l'Afrique de l'Ouest et actualisées sur le Sahel Central jusqu'en 2010; les données de précipitation à haute résolution disponibles depuis 1990 sur l'observatoire AMMA-CATCH Niger. Les modèles statistiques classiques issus de la théorie des valeurs extrêmes, ont été adaptés pour incorporer des covariables représentant des non-stationnarités spatiales et temporelles dans les pluies extrêmes. On montre la grande robustesse de ces modèles pour estimer les quantiles rares et détecter les tendances régionales dans les séries d'extrêmes. Le cadre théorique des fractales a été utilisé pour modéliser les relations d'échelles spatio-temporelles. On montre ainsi qu'une représentation de type "simple scaling" permet de décrire de manière très satisfaisante ces relations sur la gamme des pas de temps allant de 1 à 24 heures. Les résultats climatologiques confirment que la sécheresse de la fin du XXeme siècle a été avant tout associée à une baisse de l'occurrence des précipitations, leur intensité demeurant relativement inchangée. On note en revanche un comportement singulier sur la dernière décennie durant laquelle un déficit persistant d'occurrence est compensé par une intensification des précipitations qui explique un retour vers une meilleure pluviométrie annuelle, associée cependant à des extrêmes plus marqués et donc porteurs de risque hydrologique. / In West Africa, the sharp decrease of rainfall since the 70s has occurred concurrently with an increase of flood damage. If it is certain that the vulnerability of the population has increased, the question of the evolution of extreme rainfall remains unanswered - especially in a context where global warming should be accompanied by an intensification of the global water cycle. This thesis aims to improve our understanding of the extreme rainfall regime in West Africa. The work is based on three objectives: (i) provide an integrated regional vision of the spatial organization of extremes, (ii) study the evolution of extreme precipitation regime in connection with the decadal variability of annual rainfall (iii) characterize the extreme rainfall by producing rainfall hazard maps and IDAF (Intensity-Duration-Area-Frequency) curves. In this work, two datasets are used: (i) daily data from national networks, available since 1950 on West Africa, have been updated on the Central Sahel until 2010; (ii) precipitation data with high resolution available since 1990 from the AMMA-CATCH Niger observatory. Conventional statistical models from the extreme value theory has been adapted to incorporate covariates in order to represent spatial and temporal non-stationarity in extreme rainfall. These models show a high robustness to estimate the high quantiles and detect regional trends in the extreme series. The theoretical framework of fractals has been used to model the relationships of spatial and temporal scales. Climatological results confirm that the drought of the late 20th century was primarily associated with a decrease in the occurrence of rainfall, intensity remained relatively unchanged. We note, however, a singular behavior in the last decade: a persistent deficit of occurrence of rainfall is compensated by higher intensities which explains a return to better annual rainfall associated with more extreme rainfall.

Made available in DSpace on 2018-08-01T23:40:37Z (GMT). No. of bitstreams: 1 tese_9076_Dissertacao José Osmar - Configuracoes Identitarias Autarquia Publica.pdf: 1760544 bytes, checksum: a278cecc0eccaaa733fed241ac5e938e (MD5) Previous issue date: 2015-06-30 / Esta dissertação tem por objetivo compreender como as transformações no contexto da defesa sanitária e inspeção agropecuária entre 1996 e 2014 se relacionam com as configurações identitárias do Idaf manifestadas por gestores nesse contexto. Trata-se de uma pesquisa qualitativa que descreve os processos identitários da organização por um olhar interpretativista, pelo entendimento das relações simbólicas que permeiam essa organização, observados em discursos dos sujeitos. Para coleta dos dados foram utilizadas pesquisa documental e entrevistas semiestruturadas individuais. As entrevistas foram realizadas com cinco sujeitos da organização nos meses de setembro e outubro de 2014. O método de análise foi a Análise de Conteúdo (KRIPPENDORFF, 1990) que busca investigar dados textuais através de técnicas que permitam compreendê-los com seus significados, referências, valorações e intenções. Pretendeu-se contribuir, com esse estudo, para a compreensão da identidade organizacional, em uma organização pública, no contexto da defesa sanitária e inspeção agropecuária. Os resultados permitiram identificar o Idaf como único e distinto de outras organizações e como essa identificação está relacionada às transformações do contexto agropecuário.