Abstract Last century witnessed the increase of metropolitan regions and much attention has been paid on them. The concept of megacity appeared during the development process of metropolitan regions. Due to the rapid urbanisation and the population explosion in China, there are three main megacities which have great influence on the national economy. In this thesis, we choose one of the main megacities - Beijing megacity, as our case and the research question is how to strengthen the polycentricity of Beijing megacity to achieve more balanced development. In order to find out the answers to the research question, the concepts of metropolitan region, megacity and polycentric megacity are discussed in the conceptual section of this thesis. The empirical section analyses the Tokyo megacity and Los Angeles megacity on purpose of finding the lessons and experiences that could be learned and applied to strengthen the polycentric characters of Beijing megacity. In the case study chapters, firstly we analyses the problems of monocentric Beijing municipality, then we suggest the approaches of being polycentric Beijing megacity where Beijing, Tianjin and Tangshan participate actively.

Nowadays, millennials living in megacities are facing numerous issues. Most of them are currently experiencing an unsustainable lifestyle. Since this social group is destined to grow in number in the future years, its living status will strongly affect the development of sustainable cities. High frequency relocation, limited savings and lack of time are some of the Millennials’ main issues. Create appropriate solutions to their problems is therefore crucial for a sustainable development. The project aims to investigate Millennials daily life conditions through a human-needs approach performing and, at the same time analyze the possible business-based services that can help this social group to live more sustainable. This has been done through three needs-based service design methodologies that allowed to identify the reasons behind this social phenomenon: a day in life, questionnaires and phone interviews. Furthermore, a co-creation workshop allowed to investigate possible interactions between businesses realities and millennials. This project results demonstrate that there is a need of Business to Customers services which can contribute at the same time to create a sustainable lifestyle and to reduce the environmental impact of the contemporary consumerism-based society. Finally a concept of a product-based reuse service is for this reason developed considering the role of product life cycle in contemporary sustainable issues. To conclude, the importance of a needs-base approach to generate innovative solutions within the topic of service design is highlighted.

Ähnlich wie andere Metropolen in Entwicklungs- und Schwellenländern hat auch die zweitgrößte Stadt Mexikos, Guadalajara, enorme Schwierigkeiten seine Bevölkerung mit sauberem Trinkwasser zu versorgen und das Abwasser sozial- und umweltverträglich zu entsorgen. Gründe für die wachsenden Probleme hängen einerseits mit der Dynamik fortschreitender Urbanisierungsprozesse und andererseits mit der Zunahme sozialer und sozialräumlicher Disparitäten zusammen. Es werden empirische Arbeiten vorgestellt, die im Rahmen einer studentischen Exkursion entstanden sind und die sich mit dem Zusammenhang zwischen sozialräumlichen Disparitäten und der Wasserversorgung bzw. Abwasserentsorgung am innerstädtischen Flusslauf "Atemajac" beschäftigen. Dabei werden vor allem die unterschiedlichen Problemwahrnehmungen der Anwohner des Flusses und die von ihnen gesehenen Lösungsmöglichkeiten untersucht.

The area that once were “The Great Tenochtitlán”, the aztec city surrounded by five lakes, greenery and impressive sustainable systems for housing and agriculture has turned out to be a megacity growing uncontrollably, leaving a negative environmental and social impact within. Over the last 60 years the population has increased from 5.2 to 8.8 million (INEGI 2010) in the Distrito Federal and from 5.7 to 20.8 million in the ZMVM (Metropolitan Area of the Mexican Valley) known as Mexico City, area which is projected to be the third biggest city in the world by 2015 (United Nations 2005). Research Questions: What would it take for a megacity such as Mexico City to take a shift into sustainable urban design and re-development? How can infrastructures such as transit, waste management systems and public spaces interact in a hybrid urban fabric of blue and green structures, in which the natural landscape and the built environment complement each other? Aim: The aim of this study is to address a research in one of the 16 boroughs of Distrito Federal: Tláhuac, which will be the place for the first metro line reaching the urbanized south-east, therefore the activation of the area is imminent. Tláhuac is a borough with an agricultural-urban character. The area is inhabited by middle-low income families. Its connection to the city, commercial areas and public space is deplorable. The site has large areas of non-utilized agricultural land, these areas are constantly squatted, one large plot of land with these characteristics is right next to the site where the new metro line will be built. Methodology and Design Tools: The study and design is supported by the emergent discipline: Landscape Urbanism, its theory of infrastructural landscapes is used as a way to conceal the urban and the regional, and so as the belief that “Landscape has replaced architectural form as the primary medium of city making” (Waldheim 2006). The methodologies used are literature review and spatial analysis. The final outcome is a new way to do urbanism in the post-agricultural areas of Mexico City, by including the preexistent landscapes as the urban fabrics when developing towards a more urban character. The basic design tools are; infrastructural landscapes throughout the use of the canals and chinampas, urban agriculture, eco-housing, recycling stations and inclusion of new services and community areas.

京都大学 / 0048 / 新制・課程博士 / 博士(地球環境学) / 甲第19347号 / 地環博第140号 / 新制||地環||28(附属図書館) / 32349 / 京都大学大学院地球環境学舎環境マネジメント専攻 / (主査)准教授 西前 出, 教授 星野 敏, 教授 小方 登 / 学位規則第4条第1項該当 / Doctor of Global Environmental Studies / Kyoto University / DFAM

Os hidrocarbonetos (HCs) aromáticos monocíclicos, como o benzeno e o tolueno, estão entre os compostos orgânicos voláteis (COVs) de grande interesse tanto para estudos dereatividade atmosférica, devido à contribuição para formação de smog fotoquímico, quanto por efeitos nocivos diretos à saúde humana. A evaporação e queima incompleta de combustíveis é a principal fonte de benzeno e tolueno, além de atividades industriais e uso de solventes. A Região Metropolitana de São Paulo (RMSP) é uma das maiores aglomerações urbanas do mundo com 21 milhões de habitantes e frota de mais de 7 milhões de veículos. A poluição do ar, com destaque para eventos de smog fotoquímico com altas concentrações de ozônio, tem sido um dos grandes problemas ambientais da RMSP. Devido à importância do benzeno e tolueno, a Companhia Ambiental do Estado de São Paulo (CETESB) iniciou o monitoramento destes compostos com frequência horária na estação Pinheiros, em conjunto com o monitoramento de outros poluentes. Neste trabalho avaliou-se o efeito das condições meteorológicas na variabilidade temporal da concentração do benzeno e tolueno medidos na estação Pinheiros durante o ano 2017, e as interações com outros poluentes (NO2,O3e CO). As concentrações mais altas foram observadas no período do inverno e a primavera (julho, agosto e setembro), decorrentes das condições desfavoráveis à dispersão dos poluentes, com máximos de 2,81 e 14,2 ppbv para benzeno e tolueno respectivamente, 3,70 ppm para CO, 203 e 208 g/m3para NO2 e O3, respectivamente. Os valores de concentração máxima do benzeno, tolueno, CO e NO2 foram obtidos entre as 08 e 10 h da manhã e depois das 20 h, coincidindo com os horários de maior tráfego, e, portanto, aumento das emissões por queima de combustíveis. Valores mínimos foram obtidos entre as 13 e 18 h, associados à diluição e remoção em função do aumento da altura da camada de mistura e/ou da velocidade do vento nestes horários; assim como processos de remoção por reações fotoquímicas. A variação diária da concentração do O3,apresentou níveis mínimos de manhã cedo entre as 6 e 8 horas, iniciando uma subida por volta das 10 horas, atingindo os valores máximos as 15 horas. O benzeno e tolueno apresentaram correlação positiva significativa (r > 0,8) com o CO, reforçando influência das emissões veiculares. Análise mais detalhada para agosto de 2017 mostrou a complexidade das condições meteorológicas afetando a concentração dos compostos estudados, envolvendo eventos sinóticos como a passagem de frentes frias (FF) determinantes na diminuição na concentração de benzeno e tolueno. Enquanto que dias em que as alturas da camada limite convectiva e estável foram abaixo de 500m apresentaram concentrações mais altas de poluentes. / Monocyclic aromatic hydrocarbons (HCs), such as benzene and toluene, are among the volatile organic compounds (VOCs) of great interest for both atmospheric reactivity studies, due to their contribution to the formation of photochemical smog, and for direct harmful effects on human health. The evaporation and incomplete burning of fuels is the main source of benzene and toluene, as well as industrial activities and the use of solvents. The Metropolitan Region of São Paulo (RMSP) is one of the largest urban agglomerations in the world with 21 million inhabitants and more than 7 million vehicles. Air pollution, especially photochemical smog events with high concentrations of ozone, has been one of the major environmental problems for RMSP. Due to the importance of benzene and toluene, the Environmental Company of the State of São Paulo (CETESB) began an hourly monitoring of these pollutants, among others, at Pinheiros Station. This work evaluated the meteorological conditions effects on the temporal variability of the benzene and toluene concentration and their interaction with other pollutants (NO2, O3 and CO) measured at the Pinheiros station during 2017. The highest concentrations were observed during winter (July, August and September), due to the unfavorable conditions for dispersion of pollutants, with maximums of 2.81 and 14.2 ppbv for benzene and toluene, respectively, 3.70 ppm for CO; 203 and 208 g/m3 for NO2 and O3, respectively. The maximum concentration values of benzene and toluene were obtained between 08 and 10 a.m. and after 8 p.m., due to the heaviest traffic, at that time, which increases fuel-burning emissions. The minimum values were obtained between 1 and 6 p.m., which was associated to the dilution and transport as a function of the increase of the height of the mixture layer and/or the wind speed, as well as processes of removal by photochemical reactions. These compounds showed a significant positive correlation (r> 0.8) with CO, reinforcing the influence of vehicular emissions. More detailed analyses for August 2017 showed the complexity of the meteorological conditions affecting the concentration of the studied compounds. For example, synoptic events such as the passage of cold fronts (FF) caused the decrease in the concentration of benzene and toluene, while higher concentrations of benzene and toluene were associated with convective and stable layer conditions below 500 m.

Sustainability has become highly prominent, it is an important aspect of the 21st century that is gradually becoming part of everyday life. Urbanisation has also rapidly increased since the 1950s when New York was the only urban area in the world to be considered a megacity due to its extensive population; presently megacities can be found globally with predicted to arise in the future. The growth rate of some of the largest urban areas in the world has been too rapid for some cities to keep up with; resulting in environmental, social, and economic issues growing alongside the urbanisation trend. The implementation of the Sustainable Development Goals (SDGs) wants to work towards reducing and eventually removing such issues at a global scale; reducing the inequalities of the world that are more than often to visible in large urban areas. This thesis aims to examine the SDGs, specifically that of SDG 11 which focuses on cities and human settlements in line with one of the largest urban areas on the planet, Tokyo. An examination of planning and policy documents composed by the Tokyo Metropolitan Government (TMG) in the form of a comparative analysis alongside key criteria taken from SDG 11 will be conducted to gain an insight and understanding of the plans and policies that are working to create a functioning society in Tokyo.

This thesis examines the pop cultural representation of white-collar migrant women (WCMW) through the popular Chinese TV series Ode to Joy. Focusing on various aspects of their lives, this TV series raises many issues about the experiences of WCMW, including perceptions of them as “outsiders” in the megacity, gender inequality, and the tensions between female migrant identity and urban status. This study analyzes those issues by drawing on intersectional theories which examine structural inequalities from the perspective of the interactions of multiple axes of social categories. This thesis asks three major questions: In what way does Ode to Joy represent the experiences of WCMW?; To what extent do issues raised in Ode to Joy impact the wellbeing of WCMW in large cities?, and; What are the “joys” in Ode to Joy for WCMW? In addition to collecting data from the TV series, this study interviewed WCMW informants to provide first-hand accounts of their experiences in an urban culture. By critically analyzing the representation of WCMW characters’ experiences in Ode to Joy, this thesis provides insights on understanding the status of those women in a contemporary Chinese urban setting, thereby filling a gap in academic literature on the pop cultural representation of China’s white-collar migrant women in a Chinese megacity. / Graduate

A megacity is generally defined as a city that, together with its suburbs or recognised metropolitan area, has a total population of more than 10 million people. Air pollution in megacities is a major concern due to large increases of populations over the past decades. Increases of air pollution result from more anthropogenic emission sources in megacities, which include energy production, transportation, industrial activities and domestic fuel burning. In the developing parts of Africa, urbanisation is increasing rapidly, with growth rates of populations in cities of up to 5% per annum. The major driving forces for these population increases in African countries can be attributed to population growth, natural disasters and armed ethnic conflicts. In South Africa, 62% of the total population lived in cities in 2010. The rate of urbanisation growth is predicted to be 1.2% per annum. The largest urbanised city in South Africa is the Johannesburg-Pretoria conurbation (referred to as Jhb-Pta megacity) that has more than 10 million inhabitants. Johannesburg is considered to be the central hub of economic activities and -growth in South Africa. The larger conurbation includes all the suburbs of Johannesburg and Pretoria. In South Africa, household combustion and traffic emissions are major sources of pollutants in urbanised areas. The major pollutants emitted from these activities include nitrogen oxide (NO), nitrogen dioxide (NO 2 ), sulphur dioxide (SO2 ), carbon monoxide (CO), particular matter (PM) and various organic compounds. The Jhb-Pta megacity is also located relatively close to large industrialised regions in South Africa, i.e. the Mpumalanga Highveld and the Vaal Triangle. Very few air quality modelling studies have been conducted for the Jhb-Pta megacity. According to the knowledge of the author, no literature existed in peer-reviewed publications at the time of the study. An in-depth modelling study was therefore conducted to assess the current state of air quality within the Jhb-Pta megacity. The main objectives were to optimise an existing photochemical box model for the Jhb-Pta megacity and to utilise the model to investigate the photochemical processes in the Jhb-Pta megacity and surrounding areas. In this investigation, ground-based measurements of criteria atmospheric pollutant species representative of the Jhb- Pta megacity were obtained to utilise as input data in the model, as well as to compare to results determined with the model. From the ground-based measurements, the possible contribution of the Jhb-Pta megacity to the NO2 hotspot observed over the South African Highveld from satellite retrievals was also contextualised. Five ground-based monitoring sites were situated strategically within the boundaries of the Jhb- Pta megacity to measure the direct influences of urban air pollution, e.g. traffic emissions, biomass burning and residential pollution. One measurement site was situated outside the modelling domain in order to collect rural background data in close proximity to the Jhb-Pta megacity. All the air quality stations continuously measured the criteria pollutants NOx, SO2 and O3. In addition, benzene, toluene, ethylbenzene and xylene (BTEX) were measured at four sites. Passive sampling of NOx, SO2 , O3 and BTEX was also conducted in March and April 2010. Active data was obtained for March to May 2009, since no active measurements were available for the same year that passive sampling was performed due to logistical reasons. Meteorological parameters that included temperature, pressure and relative humidity were also measured at the monitoring stations Ground-based measurements provided a good indication of the state of the air quality in the Jhb-Pta megacity. The air quality levels of NO2 , SO2 , O3 and BTEX could be compared to other cities in the world. A distinct diurnal cycle was observed for NO2 at most of the stations. An early morning peak between 6:00 and 9:00 coincided with the time that commuters travel to work, whereas an evening peak between 18:00 and 21:00 could be attributed to traffic emissions and household combustion. Levels of O3, which is a secondary pollutant, peaked between 13:00 and 15:00. This diurnal pattern could be attributed to the photochemical formation of O3 from precursor species NO and VOCs. Toluene was predominantly higher than the other BTEX species. Benzene and xylene concentrations were in the same order, while the lowest levels were measured for ethyl benzene Ground-based measurements also indicated that the NO2 Highveld hotspot, which is well known in the international science community due to its prominence in satellite images, is accompanied by a second hotspot over the Jhb-Pta megacity. Peak NO2 pollution levels in the Jhb-Pta megacity exceeded the maximum daily Highveld values during the morning and evening rush hours. This result is significant for the more than 10 million people living in the Jhb-Pta megacity. Although satellite instruments have been extremely valuable in pointing out global hotspots, a limitation of satellite retrievals due to their specific overpass times has been presented. Chemical processes in the Jhb-Pta megacity were investigated by utilising an existing photochemical box model, i.e. MECCA-MCM. This model was further developed in this study and was termed the MECCA-MCM-UPWIND model. This model included horizontal and vertical mixing processes in the atmosphere. These processes were included to simulate the advection of upwind air masses into the modelling domain, as well as the entrainment from the troposphere resulting from the diurnal mixing layer (ML) height variation. Three processes, i.e. horizontal mixing, vertical mixing and ML height variation, were built into the MECCA-MCM- UPWIND model. The model was tested and evaluated to determine the efficiency of the model to represent atmospheric mixing processes. MECCA-MCM-UPWIND simulated horizontal mixing, vertical entrainment and ML height variations as expected. The input data for the model runs for the Jhb-Pta megacity modelling runs were either obtained from ground-based measurements or literature. Input data included meteorology, emission inventory, ML height and mixing ratios of the atmospheric chemical species. The chemical composition of the air mass entering the Jhb-Pta megacity was determined with MECCA-MCM- UPWIND. The concentrations and diurnal variability of criteria pollutant species were well predicted with the MECCA-MCM-UPWIND model. The day-time chemistry, especially, compared well, while slight under-predictions were observed for the night-time chemistry for most of the species. The differences observed between modelled and measured data could partially be ascribed to uncertainties associated with some of the input data obtained from literature used. The MECCA-MCM-UPWIND model was used to perform sensitivity studies on the influence of different parameters on O3 levels in the Jhb-Pta megacity. Possible scenarios to alter or mitigate pollution were also investigated. The results from the sensitivity analyses showed that O3 mixing ratios decreased within the Jhb-Pta megacity with increasing wind speeds. The contribution of local emissions to the change in the concentration of pollutants is reduced at higher wind speeds. It also indicated that the Mpumalanga Highveld can potentially be a source of NOx in the Jhb-Pta megacity that can lead to the titration of O3 . This also implies that if the air quality of the surrounding area improves, the concentration of the secondary pollutant O 3 will increase in the Jhb-Pta megacity due to the decrease in the titration of O3 . Sensitivity analyses also indicated that the Jhb-Pta megacity is a VOC-limited (or NOx-saturated) regime. Therefore, O3 reduction in the Jhb-Pta megacity will mostly be effective if VOC emissions are reduced. The same effect was observed in various cities world-wide where O3 increased when NOx emissions the Jhb-Pta megacity on the instantaneous production of O 3 was also investigated. A significant increase of approximately 23ppb O3 production was observed when changing from Euro-0 to Euro-3 vehicles with lower emissions of VOCs, NOx and CO. This compares with other modelled sensitivity studies of traffic emissions that also predict that future urban O 3 concentrations will increase in many cities by 2050 due to the reduction in the NOx titration of O3 despite the implementation of O3 control regulations / Thesis (PhD (Environmental Sciences))--North-West University, Potchefstroom Campus, 2013

A megacity is generally defined as a city that, together with its suburbs or recognised metropolitan area, has a total population of more than 10 million people. Air pollution in megacities is a major concern due to large increases of populations over the past decades. Increases of air pollution result from more anthropogenic emission sources in megacities, which include energy production, transportation, industrial activities and domestic fuel burning. In the developing parts of Africa, urbanisation is increasing rapidly, with growth rates of populations in cities of up to 5% per annum. The major driving forces for these population increases in African countries can be attributed to population growth, natural disasters and armed ethnic conflicts. In South Africa, 62% of the total population lived in cities in 2010. The rate of urbanisation growth is predicted to be 1.2% per annum. The largest urbanised city in South Africa is the Johannesburg-Pretoria conurbation (referred to as Jhb-Pta megacity) that has more than 10 million inhabitants. Johannesburg is considered to be the central hub of economic activities and -growth in South Africa. The larger conurbation includes all the suburbs of Johannesburg and Pretoria. In South Africa, household combustion and traffic emissions are major sources of pollutants in urbanised areas. The major pollutants emitted from these activities include nitrogen oxide (NO), nitrogen dioxide (NO 2 ), sulphur dioxide (SO2 ), carbon monoxide (CO), particular matter (PM) and various organic compounds. The Jhb-Pta megacity is also located relatively close to large industrialised regions in South Africa, i.e. the Mpumalanga Highveld and the Vaal Triangle. Very few air quality modelling studies have been conducted for the Jhb-Pta megacity. According to the knowledge of the author, no literature existed in peer-reviewed publications at the time of the study. An in-depth modelling study was therefore conducted to assess the current state of air quality within the Jhb-Pta megacity. The main objectives were to optimise an existing photochemical box model for the Jhb-Pta megacity and to utilise the model to investigate the photochemical processes in the Jhb-Pta megacity and surrounding areas. In this investigation, ground-based measurements of criteria atmospheric pollutant species representative of the Jhb- Pta megacity were obtained to utilise as input data in the model, as well as to compare to results determined with the model. From the ground-based measurements, the possible contribution of the Jhb-Pta megacity to the NO2 hotspot observed over the South African Highveld from satellite retrievals was also contextualised. Five ground-based monitoring sites were situated strategically within the boundaries of the Jhb- Pta megacity to measure the direct influences of urban air pollution, e.g. traffic emissions, biomass burning and residential pollution. One measurement site was situated outside the modelling domain in order to collect rural background data in close proximity to the Jhb-Pta megacity. All the air quality stations continuously measured the criteria pollutants NOx, SO2 and O3. In addition, benzene, toluene, ethylbenzene and xylene (BTEX) were measured at four sites. Passive sampling of NOx, SO2 , O3 and BTEX was also conducted in March and April 2010. Active data was obtained for March to May 2009, since no active measurements were available for the same year that passive sampling was performed due to logistical reasons. Meteorological parameters that included temperature, pressure and relative humidity were also measured at the monitoring stations Ground-based measurements provided a good indication of the state of the air quality in the Jhb-Pta megacity. The air quality levels of NO2 , SO2 , O3 and BTEX could be compared to other cities in the world. A distinct diurnal cycle was observed for NO2 at most of the stations. An early morning peak between 6:00 and 9:00 coincided with the time that commuters travel to work, whereas an evening peak between 18:00 and 21:00 could be attributed to traffic emissions and household combustion. Levels of O3, which is a secondary pollutant, peaked between 13:00 and 15:00. This diurnal pattern could be attributed to the photochemical formation of O3 from precursor species NO and VOCs. Toluene was predominantly higher than the other BTEX species. Benzene and xylene concentrations were in the same order, while the lowest levels were measured for ethyl benzene Ground-based measurements also indicated that the NO2 Highveld hotspot, which is well known in the international science community due to its prominence in satellite images, is accompanied by a second hotspot over the Jhb-Pta megacity. Peak NO2 pollution levels in the Jhb-Pta megacity exceeded the maximum daily Highveld values during the morning and evening rush hours. This result is significant for the more than 10 million people living in the Jhb-Pta megacity. Although satellite instruments have been extremely valuable in pointing out global hotspots, a limitation of satellite retrievals due to their specific overpass times has been presented. Chemical processes in the Jhb-Pta megacity were investigated by utilising an existing photochemical box model, i.e. MECCA-MCM. This model was further developed in this study and was termed the MECCA-MCM-UPWIND model. This model included horizontal and vertical mixing processes in the atmosphere. These processes were included to simulate the advection of upwind air masses into the modelling domain, as well as the entrainment from the troposphere resulting from the diurnal mixing layer (ML) height variation. Three processes, i.e. horizontal mixing, vertical mixing and ML height variation, were built into the MECCA-MCM- UPWIND model. The model was tested and evaluated to determine the efficiency of the model to represent atmospheric mixing processes. MECCA-MCM-UPWIND simulated horizontal mixing, vertical entrainment and ML height variations as expected. The input data for the model runs for the Jhb-Pta megacity modelling runs were either obtained from ground-based measurements or literature. Input data included meteorology, emission inventory, ML height and mixing ratios of the atmospheric chemical species. The chemical composition of the air mass entering the Jhb-Pta megacity was determined with MECCA-MCM- UPWIND. The concentrations and diurnal variability of criteria pollutant species were well predicted with the MECCA-MCM-UPWIND model. The day-time chemistry, especially, compared well, while slight under-predictions were observed for the night-time chemistry for most of the species. The differences observed between modelled and measured data could partially be ascribed to uncertainties associated with some of the input data obtained from literature used. The MECCA-MCM-UPWIND model was used to perform sensitivity studies on the influence of different parameters on O3 levels in the Jhb-Pta megacity. Possible scenarios to alter or mitigate pollution were also investigated. The results from the sensitivity analyses showed that O3 mixing ratios decreased within the Jhb-Pta megacity with increasing wind speeds. The contribution of local emissions to the change in the concentration of pollutants is reduced at higher wind speeds. It also indicated that the Mpumalanga Highveld can potentially be a source of NOx in the Jhb-Pta megacity that can lead to the titration of O3 . This also implies that if the air quality of the surrounding area improves, the concentration of the secondary pollutant O 3 will increase in the Jhb-Pta megacity due to the decrease in the titration of O3 . Sensitivity analyses also indicated that the Jhb-Pta megacity is a VOC-limited (or NOx-saturated) regime. Therefore, O3 reduction in the Jhb-Pta megacity will mostly be effective if VOC emissions are reduced. The same effect was observed in various cities world-wide where O3 increased when NOx emissions the Jhb-Pta megacity on the instantaneous production of O 3 was also investigated. A significant increase of approximately 23ppb O3 production was observed when changing from Euro-0 to Euro-3 vehicles with lower emissions of VOCs, NOx and CO. This compares with other modelled sensitivity studies of traffic emissions that also predict that future urban O 3 concentrations will increase in many cities by 2050 due to the reduction in the NOx titration of O3 despite the implementation of O3 control regulations / Thesis (PhD (Environmental Sciences))--North-West University, Potchefstroom Campus, 2013