No description available.

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No description available.

The labelling of methyl tertiary butyl ether (MTBE), an oxygenate additive used extensively in gasoline blending, as an environmentally harmful chemical has led to the banning and subsequent phasing-out of this additive in California (USA). In response, the global petroleum industry is currently considering replacement strategies, which include the use of tertiary amyl methyl ether (TAME) or ethanol. Subsequently, SASOL (South African Coal and Oil Limited), a local petrochemical company, in its capacity as an environmentally responsible player in the global petroleum and aligned chemical markets, has commissioned this investigation into the environmental fate of the fuel oxygenates: TAME, ethanol and MTBE. In order to evaluate the environmental fate of the oxygenates, this dissertation has formed a three-tiered approach, using MTBE as a benchmark. The first tier assessed the general fate behaviour of the oxygenates using an evaluative model. A generic evaluative model, developed by Mackay et al. (l996a), called the Equilibrium Criterion (EQc) model was used for this purpose. This fugacity based multimedia model showed MTBE and TAME to have similar affinities for the water compartment. Ethanol was demonstrated to have a pre-disposition for the air compartment. Parameterisation of the EQC model to South African conditions resulted in the development of ChemSA, which reiterated the EQC findings. The second tier quantified the persistence (P), bioaccumulation (B) and long-range transport (LRT) potential of the additives. This tier also included a brief toxicity (T) review. MTBE and ethanol were demonstrated to be persistent and non-persistent, respectively, according to three threshold limit protocols (Convention on the Long Range Trans-boundary Air Pollution Persistent Organic Chemical Protocol; the United Nations Environment Programme Global Initiative; and the Track 1 criteria as defined by the Canadian Toxic Substances Management Policy, as referred to by the Canadian Environmental Protection Act 1999). These protocols were not unanimous in the persistence classification of TAME. Further investigation of persistence was conducted using a persistence and long-range transport multimedia model, called TaPL3, developed by Webster et al. (1998) and extended by Beyer et al. (2000). TaPL3 reiterated the conclusions drawn from the threshold limit protocols, indicating that TAME's classification worsened from non-persistent to persistent on moving from an air emission to a water emission scenario. This served to emphasise the negative water compartment affinity associated with TAME. Using classification intervals defined by Beyer et al. (2000), TaPL3 demonstrated that the long-range transport potential of the oxygenates increased in the order of TAME, ethanol and MTBE; however, it was concluded that none of the oxygenates were expected to pose a serious long-range transport threat. Bioaccumulation was not expected to be a pertinent environmental hazard. As expected, the oxygenates were dismissed as potential bioaccumulators by the first level of a screening method developed by Mackay and Fraser (2000); as well as by the threshold limit protocols listed above. Simulation of biomagnification, using an equilibrium food chain model developed by Thomann (1989), demonstrated that none of the oxygenates posed a biomagnification threat. A review of toxicity data confirmed that none of the three oxygenates are considered particularly toxic. LDso values indicated the following order of increasing toxicity: ethanol, MTBE and TAME. The third tier focussed on oxygenate aqueous behaviour. A simple equilibrium groundwater model was used to analyse the mobility of the oxygenates in groundwater. TAME was found to be 21 % less mobile than MTBE. Ethanol was shown to be very mobile; however, the applicability of the equilibrium model to this biodegradable alcohol was limited. An analysis of liquid-liquid equilibria comprised of oxygenate, water and a fuel substitution chemical was performed to investigate fuel-aqueous phase partitioning and the co-solvency effects of the oxygenates. Ethanol was shown to partition appreciably into an associated water phase from a fuel-phase. Moreover, this alcohol was shown to act as a co-solvent drawing fuel chemicals into the water phase. MTBE was found to partition sparingly into the water phase from a fuel-phase, with TAME partitioning less than MTBE. Neither ether was shown to act as a co-solvent. It was concluded that TAME and ethanol pose less of a burden to the environment than MTBE. Ethanol was assessed to be environmentally benign; however, it was concluded that ethanol's air compartment affinity and the extent of its co-influence on secondary solutes justified the need for further investigation before its adoption as a fuel additive. This project showed sufficient variation in the environmental behaviour of TAME and MTBE to justify the abandonment of the axiom that MTBE and TAME behave similarly in the environment. However, as MTBE is a significant water pollutant, and TAME has been shown to share a similar water affinity, it is cautiously recommended that the assumption of environmental similarity be discarded, except for the water compartment. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2002.

published_or_final_version / Geography / Master / Master of Arts in China Development Studies

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

Chemical kinetic mechanisms governing the fate of coal nitrogen in the fuel-rich stage of a pulverized-coal staged combustion process were investigated. Emphasis was on determination of the effects of coal rank, temperature and stoichiometric ratios on the speciation and rates of destruction of nitrogenous species and correlation of coal data by a unif1ed mechanism. The relative importance of homogeneous and heterogeneous mechanisms during post-flame interconversion reactions of the fuel nitrogen pool was quantified. Experiments with doped propane gas and a high- and low-grade coals, burned under a variety of conditions in a 2 Kg/h downflow combustor, yielded timeresolved profiles of temperature, major (H₂, CO, CO₂, O₂ and N₂), nitrogenous (NO, HeN and NH₃) and hydrocarbon (CH₄ and C₂H₂) species. These profiles allowed global mechanisms describing the speciation and destruction of fuel nitrogen species to be explored, using predictive models of increasing levels of sophistication. Fuel nitrogen speciation varied significantly from coal to coal and depended on stoichiometric ratio and temperature, which were varied independently. A general correlation describing the destruction rate of NO was derived from data. This rate, which was first-order in both NO and NH₃, was generally valid for all coals and all conditions examined. Fuel nitrogen interconversion reactions, especially destruction of NO and HeN, was predominantly homogeneous, but no single elementary reaction was controlling. Temperature quench down the combustor is the origin of OH equilibrium overshoot. Expressions for estimating the OH equilibrium overshoot as a function of the axial temperature decay along the combustor were derived both empirically and kinetically from fundamental considerations using data from doped propane gas runs. These expressions, together with available literature values of gas phase rate coefficients, could adequately describe the post-flame NO and HeN profiles of coal and gas runs. HeN profiles in the far postflame zone of the coal flames are strongly influenced by the slow release of nitrogen from the coal residue. This devolatilization plays a critical role in supplying the HeN that drives the multistep process converting fuel N into molecular nitrogen.

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The notion of green infrastructure brings a new dynamic for dealing with urban problems in a way that responsively addresses urban problems while at the same maintaining the ecological integrity of the natural environment. Key to the notion of green infrastructure is the need to integrate and link green areas with built infrastructure in planning and development processes. Green infrastructure suggests that to achieve sustainable development in urban landscapes, green spaces should be planned for and managed as infrastructure and must be conceived of and understood as a genuinely possible means to improve and contribute to sustainability. Green infrastructure requires an institutional and policy framework that supports practices geared towards planning and managing green assets in the same way in which traditional infrastructure systems are managed. This study explores the planning and management dynamics of green infrastructure in the City of Johannesburg. The study analyses the institutional and policy frameworks of City of Johannesburg to understand these dynamics. One the one hand, the aim is to explore whether green space planning and management is understood in an ‘infrastructural’ sense and on the other, to explore the institutional blockages for green infrastructure planning in the City. The study argues that a number of institutional and implementation challenges for planning and management of green infrastructure exist in Johannesburg. These are the result of an institutional setup which essentially provides fertile ground for some structures to compete against one another rather than work collaboratively in areas that are of common interest. While these challenges exist in the city, it has been established in the study that the City has begun to shift towards green infrastructure practices to address certain urban problems such as flooding and storm-water. For instance, the City is currently deepening its understanding of the concept of Sustainable Urban Drainage Systems (SUDS) to explore how this can contribute towards addressing issue of storm-water management. Important to note that is that while there is this gradual shift towards SUDS, the notion of green infrastructure largely remains at the conceptual level, in relation to particular issues, and is yet to be fully implemented and mainstreamed in the City’s planning processes.

Iron and steel plants in general are significant sources of PM10 pollution. Many studies have concluded that PM10 is harmful to human health and well being. ArcelorMittal Vanderbijlpark Works falls within the jurisdiction of the Vaal Triangle Airshed Priority Area (VTAPA) and has been given PM10 reduction targets in the Air Quality Management Plan. The aim of this study is to use dispersion modelling to determine the impact of the Vanderbijlpark Works steel plant on ambient PM10 and to assess the effectiveness of the reduction strategies with respect to PM10 The AERMOD dispersion model was chosen for the exercise because of its reliability when modelling near field dispersions on relatively flat terrain. Meteorological data was obtained from on-site stations. Emissions data was obtained from an already existing emissions inventory on site. The study modelled the PM10 baseline for 2010 and then modelled the predicted concentrations after implementation of the strategies as outlined in the VTAPA. The modeling scenarios were compared to the measured PM10 data from the fence line monitors. The following findings were made: Point sources were not significant contributors to PM10 emission. Modeling of area sources and other fugitive dust sources were found to be high and when compared to measured concentrations were found to be over predicted. It is concluded that the fugitive sources have been found to be the major source of PM10 emissions and that reduction of fugitives should feature prominently in emission reduction plans going forward. In addition, the fugitive emissions inventory needs to be refined to enhance the accuracy of the predictions.