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.