3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Development of high accuracy hazardous air pollutants, primary standard gas mixtures(2018) Lekoto, Goitsemang AngelinahVolatile organic compounds also classified as hazardous air pollutants (HAPs) such as benzene, chloroform, dichloromethane, 1,2-dichloroethane, tetrachloroethylene, trichloroethylene, vinyl chloride and 1,3-butadiene. have been identified to be potential carcinogens and travel longer distances from their point sources from one environmental compartment to the other. Monitoring of HAPs in ambient air has been receiving great attention across the world due to its contribution to emission studies of air pollution. However, to accurately measure these contaminants in the atmosphere standards of high accuracy are needed to ensure good air quality monitoring. Measurements which are accurate have traceability to SI unit because they are comparable internationally and are associated with low uncertainty. In this study the development of gaseous standard gas mixtures was carried following gravimetric method. The preparation of gaseous mixture is difficult due to the nature and properties of gas. To accurately follow gravimetric preparation, purity analysis of high pure starting materials was performed to obtain the precise composition of the final mixture. Various techniques such as gas chromatography coupled to mass-spectroscopy, thermal conductivity detector and pulsed charged ionisation detector were used. The development of gases was carried out following direct-step dilution for pure liquid samples using syringe method and multiple-step dilution for pressurized liquid. To carefully understand the behaviour of gases, binary gas mixtures were prepared in nitrogen at 10 µmol/mol, followed by 10 µmol/mol multicomponent of six gas component and 100 nmol/mol eight components to check for matrix interference. Gas chromatography coupled to flame ionisation detector was used to verify gravimetric concentration and following ABA sequence using one point calibration. The sequence was used to monitor instrumental drift, affecting analysis results. No impurities were detected in benzene, chloroform, tetrachloroethylene, trichloroethylene, dichloromethane and 1,2-dichloroethane. Nitrogen impurities were detected in vinyl chloride at 681±4.4 µmol/mol and 1,3-butadiene at 254± 2.1 µmol/mol. The method of analyses obtained good results with instrumental drift of less than 1.0. Good accuracy of less than 3 % was obtained between the gravimetric and analytical results. Relative expanded uncertainty was different for the binary gas mixtures, benzene was obtained within 3.2 %, tetrachloroethylene 1.9 %, chloroform 2.5 %, vinyl chloride 0.15 %, trichloroethylene 2.3 %, dichloromethane 2.7 %, 1,2-dichloroethane 2.5 % and 1,3 butadiene 0.15 % at coverage factor of K= 2 at 95 % c-onfidence level. Multicomponent development showed no interferences within the mixture during analyses for determining of accuracy of mole-fraction gravimetrically prepared. Percentage difference between the gravimetric and analytical values were within 2.03 % with relative expanded uncertainty ranging between 3.1 to 9.8 % at K=2 at 95 % confidence level. The developed multicomponent was successfully used to identify and quantify HAPs found in air sampleItem Trade, climate change and renewable energy: regulatory conflict or convergence?(2018) Thomaides, Anastasia ChrisaThe research report seeks to explore the link between trade and the environment, with a particular focus on the renewable energy sector. The aim is to determine the tensions and unification amongst the regulatory tools of the World Trade Organisation and Climate Change Regimes will be discussed, in a manner that shows how trade can assist in mitigating or adapting to the effects of climate change. As such the intention of the report is to answer the question of how do we use trade to disseminate energy technology as set out in the Sustainable Development Goals (“SDGs”) in order to ensure access to affordable, reliable, sustainable and modern energy for all, in both an international and South African context. The result, however, lead the need for more inclusive global regime that is less fragmented, over and above the need for improvement for domestic laws as well as infrastructure to generate electricity in order to provide for much more enabling approach to the investment of renewable energy.Item Metal content in soil and a wild leafy vegetable, Bidens pilosa L. on the Witwatersrand gold fields(2017) Mlalazi, NkanyisoMetal pollution could result in health and economic risks to communities. Plant absorbs both essential and toxic elements from polluted soil and water. Consumption of contaminated vegetables and incidental ingestion of soils have been confirmed to be a pathway of contaminants for humans and livestock. Previous studies have established that some species which are utilized as wild leafy vegetables (WLVs) grow on polluted land in Witwatersrand goldfields, and people harvest these vegetables for consumption. An edible plant that is harvested and consumed is Bidens pilosa (black jack). Samples of soil and corresponding B. pilosa leaves were collected from a mine contaminated site on the Witwatersrand known as the Varkenslaagte, in Gauteng Province which is being monitored since the implementation of phytoremediation about 14 years ago. Metal concentrations were compared with those in soil and leaf material collected from different sites, viz., (i) the nearby Kraalkop nature reserve (n=2); (ii) a commercial/industrial site in Johannesburg’s central business district (n=1) and (iii) a residential site in Johannesburg (n=1). Different soil particle size fractions and leaf material subjected to different treatments were analysed for iron (Fe), zinc (Zn), arsenic (As), and lead (Pb) concentrations. Concentration of As in unfractionated soils were highest in Kraalkop plot 2 (52.6 mg/kg). Johannesburg commercial area had the least As concentration (6.3 mg/kg). Zinc concentrations in soils were highest in Johannesburg commercial area (649.3 mg/kg) and lowest in Varkenslaagte (84.0 mg/kg). Kraalkop plot 1 had the highest Fe concentrations (61000 mg/kg) and Johannesburg residential suburb had the lowest Fe concentrations (31720 mg/kg). Lead concentrations in soils were highest in Johannesburg commercial area (185.9 mg/kg) and lowest in Varkenslaagte (32.6 mg/kg). While the mean concentrations of Pb, As and Zn in soil and B. pilosa in Varkenslaagte (n=8) was in some cases lower than concentrations in some of the comparison sites, the metal concentrations in some plots in Varkenslaagte were above the concentrations of the samples obtained from the comparison sites. This indicates that metal concentrations are still high in some areas of the Varkenslaagte despite remediation. There was no significant difference in distribution of metal concentrations between different soil particle size ranges. Different preparatory and cooking methods resulted in different concentrations of Fe and Pb. However, concentrations of As and Zn were not affected by different categories of B. pilosa treatment and cooking methods. Concentrations of Zn and Pb exceeded minimum allowable limit levels as stipulated in FAO/WHO, European Union (EU) and South African regulations relating to maximum levels of metals in leafy vegetables. A dietary risk index (DRI) indicated that there is no obvious risk to adult populations from B. Pilosa consumption, particularly as this species is not consumed in the same volumes as other, more popular, wild leafy vegetables. However, this preliminary study does not include DRI in children, dietary exposure through consumption of other foods besides B. pilosa and does not encompass dermal and inhalation exposure pathways which are important contributing factors to health risk indices. Key words: Wild leafy vegetables, gold mining, pollution, contaminated land, dietary riskItem The deterioration of the life support base: the perceptions of people in informal settlements towards limiting pollution in their environment(2008-08-28T12:07:31Z) Mporetji, SimonDiepsloot, a township in Johannesburg, South Africa, was used as a case study to explore the perceptions of people in informal settlements towards their role in limiting pollution in their environment. The method followed was qualitative, and primary data were collected through the use of key informants (Ward Councillor and Environmental Health Officer), and three focus groups. Diepsloot is a marginalised residential area located in the Northern perimeter of the City of Johannesburg. The settlement is spatially fragmented, reflects a high residential density and is plagued with high levels of unemployment and poverty. Compounded by poor municipal service delivery, these challenges lead to a range of environmental problems such as overflowing solid waste on the streets, water pollution, and high levels of indoor air pollution. The study found that there were varying levels of commitment to limiting pollution by people in the informal settlement. This (commitment to limiting pollution) was largely dependent on community action through the formation of street committees. In streets where there was community cohesion, street committees were stronger and environmental conditions were better. In contrast, environmental problems were worse where street committees were weak or not operating. Regarding the role of government, the major constraints leading to unresponsive interventions were the limited scale of municipal operation and their poor communication with residents. Suggested corrective measures include recycling, education on pollution and the need for institutional strengthening. Further research aimed at identifying a set of appropriate partnerships and institutions needed for responsive interventions in informal settlements is required.