3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Assessment of BTEX concentrations on-board in-service public buses in Johannesburg, South Africa(2019-07) Mansoor, YusufExposures to BTEX compounds in indoor environments are of great concern as these compounds have been shown to negatively influence human health. For urban dwellers, a major part of the day is spent indoors within microenvironments such as offices, schools, homes and while commuting on-board vehicles. Of the different types of microenvironments, vehicle cabins have been shown to have the highest BTEX concentrations due to the vehicle being a source of emissions itself and due to its close proximity to other sources of emissions. This study specifically considers BTEX concentrations on-board public buses as these vehicles transport large numbers of people over various distances and that commuters frequently spend a considerable amounts of time commuting on-board these vehicles daily. The aim of this study was to determine the BTEX concentrations on-board in-service public buses travelling along major routes through Johannesburg during the off-peak and peak times and to determine the factors which might affect these concentrations. The factors which were specifically taken into consideration were on-board temperature and humidity, ventilation mode, passenger number and the characteristics of the travelled routes. Two sampling campaigns were conducted; one during the off-peak and another during the peak commute times. For each campaign, buses travelling along three different routes, representing major commuter routes, were sampled. A total of 21 and 42 samples were collected on-board the buses for the off-peak and peak campaign, respectively. An active sampling approach was taken using personal air sampling pumps attached to coconut charcoal sorbent tubes. iButtons were used to collect on-board temperature and humidity and a GPS was used to collect the route data. The charcoal tubes were prepared using solvent extraction and subsequently analysed using gas chromatography (time – of – flight) mass spectrometry. In addition, field blanks, lab and solvent blank samples were analysed as quality assurance measures during both campaigns. The mean BTEX concentrations measured during the off-peak and peak campaigns were Benzene - 24.39 μ/m3, Toluene - 85.88 μ/m3, Ethylbenzene - 4.80 μ/m3 and Xylene - 5.70 μ/m3 and Benzene- 28.19 μ/m3, Toluene - 9.85 μ/m3, Ethylbenzene - 2.94 μ/m3 and Xylene - 7.5 μ/m3, respectively. A significant difference (p > 0.05) was noted between the off-peak and peak toluene concentrations, while no significant differences were observed amongst the other BEX compounds between campaigns. The analysis of the BTEX concentrations along travelled routes returned a result indicating no significant differences (p < 0.05) between sampled routes for both campaigns; except for the ethylbenzene measured during the off-peak campaign which showed a significant difference (p < 0.05) between Routes A and C. With regards to the effects of ventilation mode, passenger number and on-board temperature and humidity, no discernible effects on BTEX concentrations could be observed from the data. Furthermore, the lab and field blank samples measured varied levels of BTEX concentration, which would suggest sample contamination, which introduced a level of uncertainty in deriving actual BTEX concentrations. In general, no definitive conclusions could be drawn from this study, regarding the BTEX concentrations on-board the buses during the off-peak and peak times, effects of travelled routes, passenger number and ventilation mode, potential sources of BTEX compounds and their interaction with the on-board temperature and humidity. However, given that a study of this nature has not been published in South Africa; the current study is of value in guiding future researchers as to the potential challenges and barriers that might be faced when conducting such a study. Furthermore, this study has the potential to stimulate interest in the field of in-vehicle emission testing with regards to not only buses and VOCs but other pollutants such as NOx, PM, and CO amongst a variety of vehicle types and across other microenvironments in general.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 Assessment of changing urban dynamics in Johannesburg city regions as consequence of re-mining of the tailings dumps using Geographical Information System and remote sensing(2017) Mahao, Tseliso JohnThere is a growing interest in the reclamation of the old gold mines’ tailings dumps in Johannesburg city region driven by the economic value of the remaining gold resource. This reclamation activity is accompanied by various rehabilitation methods to reduce issues such as acid mine drainage and wind pollution. The impact of land use and land cover change (LULCC) can have an enormous impact on land development and planning. Monitoring of LULCC is very important in the planning and decision making processes. Remote sensing (RS) as the source of basic data for monitoring change is very highly recommended as tool to monitor changes occurring in the Johannesburg City Region as a result of rehabilitation and reclamation of the gold mines’ tailings deposits. The main aim of the study is to understand how the reclamation and rehabilitation of the historical tailings dumps in Johannesburg are changing land use patterns of the city and its precincts. The objectives are to quantify the changes in land use and land cover as the results of mining rehabilitation using Landsat earth observation data over a period of 30 years at five years intervals and; to recommend on how the land cleared of waste dumps could be used for looking at the surrounding environment spatially. Various Geographical Information Systems techniques are applied here for change detection analysis and monitoring of potential changes in urban dynamics patterns. The results show rate of rehabilitation and reclamation to be slow, taking several years to see a meaningful change. There is some form of bias towards transforming the reclaimed land into industrial zones as opposed to other activities. The success of tailings dumps rehabilitation through revegetation process is highlighted.Item Linking streamwater quality of the upper Vaal River catchment area to acid deposition(2018) Mbewe, IsabelAcid deposition is the conveyance of acid compounds predominantly oxides of nitrogen and sulphur, acids, and salts from the atmosphere to the earth's surface. It has detrimental effects on both terrestrial and aquatic ecosystems. The concentration of industrial structure over the Highveld region of South Africa makes it a prominent air pollution area accounting for approximately 90% of South Africa's scheduled emissions of industrial dust, sulphur dioxide and nitrogen oxides. The high pollution levels mean the Highveld region is an acid deposition hotspot. This paper investigated the link between stream water quality and acid deposition by precluding the influence of land use and catchment geology on water quality in the Upper Vaal. [Abbreviated Abstract. Open document to view full version]Item An assessment of spatial and temporal variations of nitrogen dioxide over Mpumalanga highveld(2017) Malaza, Lucky SamuelHigh concentrations of nitrogen containing compounds are a growing concern in the Mpumalanga Highveld with satellite measurements confirming high NO2 in different hotspots around the globe including Mpumalanga Highveld. Nitrogen oxides are produced from the eight coal fired power stations in Mpumalanga Highveld, a petrochemical industry in Secunda, steel processing plants in Middelburg and Emalahleni and tail emissions from traffic in the Mpumalanga Highveld. Monitoring of these trace gases is important to estimate an impact that they cause to human health and the environment and also to implement air quality emission standards by government Authorities. A 2008 data from Elandsfontein monitoring station and seven other monitoring stations in the Mpumalanga Highveld have been compared with the 2008 satellite data taken from Ozone Monitoring Instrument (OMI) overpass over the Mpumalanga Highveld. Elandsfontein monitoring station is situated on the highly industrialized Mpumalanga Highveld and its purpose is to monitor impacts of stack emissions on air quality. The study focuses on a 2008 nitrogen dioxide dataset which was taken from Elandsfontein monitoring station. An analysis of data from other monitoring stations located in Ermelo, Bulfour, Hendrina, two stations in Middelburg, Emalahleni, Standerton and Secunda have been undertaken to indicate temporal variation and spatial distribution of nitrogen dioxide in the Mpumalanga Highveld. Temporal variability and spatial distribution of nitrogen dioxide in the Mpumalanga Highveld were estimated by analyzing the ground based measurements and satellite data sets. Smoke stacks emit NO into the atmosphere where it reacts with atmospheric oxygen to form NO2. Subsequent reactions of NO2 result in the formation of ozone. The satellite derived data has been modelled and compared with the ground measured data. Meteorological factors including diurnal and temporal variations of the NO2 concentrations have been analyzed to establish differences and similarities between the two data sets. Vertical column densities of nitrogen oxides from satellite measurements with high resolution are presented in mole x (1015)/cm2 and together with ground measured data from other eight air quality monitoring stations have been converted into μg/m3. Analysis of both data sets have been done on the same units, μg/m3 . Seasonal and diurnal variations between the two data sets seem to form the same graphical trends by showing high concentrations during winter than in summer. Ground measured and satellite born datasets do not agree because clouds, air mass factor, aerosols and surface albedo create retrieval errors on the satellite data.Item The desulfurization of petroleum compounds using a polymer-supported imidation agent(2016) Matoro, Tshilidzi BenedictaThe sulfur removal methods from petroleum products have become an important research topic. Sulfur poisons the catalysts found in vehicles engines and it is also a major air pollutant (Nehlsen, 2005). Recent sulfur specifications require refineries to produce ultra-clean products (Ma et al., 2002). This work aims at exploring a batch adsorptive desulfurization technique using a polymer-supported imidation agent (PI) as an adsorbent. The test was carried out at atmospheric pressure and on two commercial diesel fuels with sulfur contents of 5200 (Case 1) and 670 (Case 2) mg/kg which resembles the feed and outlet streams from the hydrodesulfurization (HDS) reactor respectively. The adsorbent was synthesized according to the procedure described by Shiraishi et al. (2003), BET, FTIR, SEM equipped with EDS and TGA were used for charaterization of the adsorbent. The PI was successfully synthesized and its surface area was 0.5333 m2/g which was incredibly lower than that of the PI synthesized by Fadhel (2010). Hence carbon nanotubes (CNTs) were added to the solution with the aim of improving the sulfur removal efficiency of PI. The obtained results indicated that PI with CNTs yield better results than PI without CNTs. In overall, the lowest sulfur content of 3462 mg/kg (33% removal efficiency) and 26 mg/kg (96% removal efficiency) for Case 1 and Case 2 respectively were obtained. Furthermore, the adsorbents were most effective at lower mixing rates (150 – 400 rpm), longer contact time (30 – 40 hours), practically high adsorbent amount (1 g) and moderate lower temperatures (25 – 50 ºC). The Freundlich adsorption isotherm model was the best fit to the experimental data in both Case 1 and Case 2. The kinetic model that best fitted well the experimental data is the pseudo-second-order model for both Case 1 and Case 2. The kinetic rate constant for Case 2 (4.079 x 10-3g/mg.min) was greater than that for Case 1 (6.75 x 10-5g/mg.min) thus indicating that fuel with low sulfur content has a higher sorption uptake than fuel with high sulfur content. Based on the results obtained in this study, it is suggested that the adsorption of sulfur at high sulfur content fuel is not capable to be used as a complimentary method to the HDS process. On the other hand, at low sulfur content fuel, there is an opportunity for combining this method with the traditional HDS method to achieve ultra-clean fuel.