A study of the airflow on the windward slope of a transverse dune in the Alexandria coastal dunefield
- Authors: Burkinshaw, Jennifer Ruth
- Date: 2021-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52734 , vital:43883
- Description: Our understanding of the evolution of dune morphology has been hampered by a lack of empirical observations of airflow behaviour over dune forms. Sand dunes intrude into the atmospheric boundary layer and convergence of streamlines results in an acceleration of airflow up the windward slopes of dunes. This study examines the airflow structure and corresponding bedform development on the windward slope of a 7 m high transverse dune on the edge of the Alexandria coastal dunefield, Algoa Bay, South Africa. The Alexandria dunefield is subjected to a trimodal wind regime, consisting of the dominant south-westerly which blows all year round, summer easterlies and winter northwesterlies. The morphology of the study dune, Dune13, is controlled by the easterlies and north-westerlies, and reverses seasonally with respect to these two winds. Seven section lines 30 m apart and normal to the dune crest were surveyed regularly over the period of a year to monitor the reversal process. Three detailed topographic surveys were also done during this period. Airflow behaviour was monitored during the year. Wind speed profiles on the windward slope of the dune were measured using 4 to 5 vertical arrays of anemometers positioned from the base of the dune to the crest on a 1 selected section line. Usually 4 to 5 anemometers were deployed in each vertical array, from a height of 6 to 10 cm above the surface, up to a height of 150 cm above the surface. Initially 8 microanemometers were available; ultimately 28 anemometers were run simultaneously. An independent weather station at an elevation of 6 m recorded the unaccelerated flow. Local gradient measurements and erosion and deposition rates were recorded along selected section lines. Strong summer easterly winds (14 m/sec at 1.4 m above the dune crest) were measured on a dune slope in the process of being transformed from a slipface to a stoss slope. The following winter, light north-westerly winds (typically B m/sec at 1.6 m above the dune crest) were measured on the new windward slope already reversed by the prevailing winter wind. Airflow data confirm the compression of airflow against the windward slope resulting in a non-logarithmic wind speed profile. Compression results in an increased shear velocity within 30 cm of the dune surface, and the dune slope is eroded. Higher up in the wind speed profile, shear velocity decreases to 0.1 m/sec. It is not known at what height the wind speed profile recovers from the intrusion of the dune into the boundary layer. High values of shear velocity (1.6 m/sec) above the rounded crestal area of the dune record the recovery of the wind speed profile from flow divergence, which is a response to the rapid reduction of dune gradient and is accompanied by deposition of sand in this region. 2 The erosion pin data act as a simple and sensitive test for changes in gradient, reflecting the dune's response to changes in the airflow regime. The shape of the dune plays a major role in determining the extent of the compression and the distribution of shear velocity up the slope. Increased shear velocity is experienced on that part of the slope which is nonaerodynamic with respect to the prevailing wind. Under unidirectional conditions, feedback between flow and form results ultimately in a slope with a curvature such that shear velocity increases systematically upslope. The survey data and erosion pin data record the reversal process as the dune achieves a new steady state during each wind season. The existence of a non-logarithmic wind speed profile makes it difficult to know what relevant measure of shear velocity is to be used in sand transport equations. Future work should include wind speed measurements within 10 cm of the surface. An ideal study modelling aeolian bedform development would utilise wind tunnel measurements, combined with field measurements such as obtained in this study, for comparison with numerical modelling. The study needs to be extended to 3-dimensional airflow measurements. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Burkinshaw, Jennifer Ruth
- Date: 2021-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52734 , vital:43883
- Description: Our understanding of the evolution of dune morphology has been hampered by a lack of empirical observations of airflow behaviour over dune forms. Sand dunes intrude into the atmospheric boundary layer and convergence of streamlines results in an acceleration of airflow up the windward slopes of dunes. This study examines the airflow structure and corresponding bedform development on the windward slope of a 7 m high transverse dune on the edge of the Alexandria coastal dunefield, Algoa Bay, South Africa. The Alexandria dunefield is subjected to a trimodal wind regime, consisting of the dominant south-westerly which blows all year round, summer easterlies and winter northwesterlies. The morphology of the study dune, Dune13, is controlled by the easterlies and north-westerlies, and reverses seasonally with respect to these two winds. Seven section lines 30 m apart and normal to the dune crest were surveyed regularly over the period of a year to monitor the reversal process. Three detailed topographic surveys were also done during this period. Airflow behaviour was monitored during the year. Wind speed profiles on the windward slope of the dune were measured using 4 to 5 vertical arrays of anemometers positioned from the base of the dune to the crest on a 1 selected section line. Usually 4 to 5 anemometers were deployed in each vertical array, from a height of 6 to 10 cm above the surface, up to a height of 150 cm above the surface. Initially 8 microanemometers were available; ultimately 28 anemometers were run simultaneously. An independent weather station at an elevation of 6 m recorded the unaccelerated flow. Local gradient measurements and erosion and deposition rates were recorded along selected section lines. Strong summer easterly winds (14 m/sec at 1.4 m above the dune crest) were measured on a dune slope in the process of being transformed from a slipface to a stoss slope. The following winter, light north-westerly winds (typically B m/sec at 1.6 m above the dune crest) were measured on the new windward slope already reversed by the prevailing winter wind. Airflow data confirm the compression of airflow against the windward slope resulting in a non-logarithmic wind speed profile. Compression results in an increased shear velocity within 30 cm of the dune surface, and the dune slope is eroded. Higher up in the wind speed profile, shear velocity decreases to 0.1 m/sec. It is not known at what height the wind speed profile recovers from the intrusion of the dune into the boundary layer. High values of shear velocity (1.6 m/sec) above the rounded crestal area of the dune record the recovery of the wind speed profile from flow divergence, which is a response to the rapid reduction of dune gradient and is accompanied by deposition of sand in this region. 2 The erosion pin data act as a simple and sensitive test for changes in gradient, reflecting the dune's response to changes in the airflow regime. The shape of the dune plays a major role in determining the extent of the compression and the distribution of shear velocity up the slope. Increased shear velocity is experienced on that part of the slope which is nonaerodynamic with respect to the prevailing wind. Under unidirectional conditions, feedback between flow and form results ultimately in a slope with a curvature such that shear velocity increases systematically upslope. The survey data and erosion pin data record the reversal process as the dune achieves a new steady state during each wind season. The existence of a non-logarithmic wind speed profile makes it difficult to know what relevant measure of shear velocity is to be used in sand transport equations. Future work should include wind speed measurements within 10 cm of the surface. An ideal study modelling aeolian bedform development would utilise wind tunnel measurements, combined with field measurements such as obtained in this study, for comparison with numerical modelling. The study needs to be extended to 3-dimensional airflow measurements. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text:
- Date Issued: 2021-04
An investigation into the effects of nano-carbons on the negative electrode morphology of lead acid batteries under high rate partial state of capacity cycling
- Authors: Bolo, Lukanyo
- Date: 2021-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53324 , vital:45132
- Description: New technological developments in the field of Hybrid Electric Vehicles (HEV’s), vehicle stop-start applications and electrical power utility devices have brought about new demands on the use of energy storage devices such as the Pb-acid battery. These applications require a new understanding and research into the material chemistry of the battery where it has to functionin a Partial State of Capacity Cycling (PSoCC) or High Rate Partial State of Capacity Cycling (HRPSoCC)duty. The Pb-acid battery is well known for its use in the automotive industry where it had worked for decades as a typical Starter, Lighting and Ignition (SLI) power source. However, the conventional Pb-acid battery is not suitable for the new types of vehicle demands and applications. When the Pb-lead acid battery is subjected to PSoCC conditions, very quickly excessive amount of non-conducting PbSO4crystals are formed on the negative plates of the battery that then drastically reduce its useful life in application. Over the years, researchers have shown that the small addition of certain carbon types to the negative plate active material (NAM) during battery manufacturing can reduce the sulfation effect thereby increasing its use the modern vehicle applications. This study investigated industrial manufactured cells that contained up to 0.5 % by weight two types of carbons in the NAM. These were compared to standard built cells in terms of their standard achievable capacities at various rates, their Cold Cranking Ability (CCA), their Dynamic Charge Acceptance (DCA) and a simplified PSoCC test. The carbons were classified as an activated carbon and a carbon nano-fiber and were included as a dry weight additive during the standard paste manufacturing process of the negative plate. Cells were built with a 9-plate configuration using standard expanded grid positive plates with a nominal rated capacity of 36 Ah. The cells were formed and subjected to a number of electrochemical tests, of which selected negative plates were then studied using Scanning Electron Microscopy (SEM) and Electrochemical in-situ Atomic Force Microscopy (EC-AFM). The microscopic study was then used to try and relate the observed material characteristics of the NAM with the carbons to the electrochemical results observed when testing a built cell. , Thesis (MA) --Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Bolo, Lukanyo
- Date: 2021-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53324 , vital:45132
- Description: New technological developments in the field of Hybrid Electric Vehicles (HEV’s), vehicle stop-start applications and electrical power utility devices have brought about new demands on the use of energy storage devices such as the Pb-acid battery. These applications require a new understanding and research into the material chemistry of the battery where it has to functionin a Partial State of Capacity Cycling (PSoCC) or High Rate Partial State of Capacity Cycling (HRPSoCC)duty. The Pb-acid battery is well known for its use in the automotive industry where it had worked for decades as a typical Starter, Lighting and Ignition (SLI) power source. However, the conventional Pb-acid battery is not suitable for the new types of vehicle demands and applications. When the Pb-lead acid battery is subjected to PSoCC conditions, very quickly excessive amount of non-conducting PbSO4crystals are formed on the negative plates of the battery that then drastically reduce its useful life in application. Over the years, researchers have shown that the small addition of certain carbon types to the negative plate active material (NAM) during battery manufacturing can reduce the sulfation effect thereby increasing its use the modern vehicle applications. This study investigated industrial manufactured cells that contained up to 0.5 % by weight two types of carbons in the NAM. These were compared to standard built cells in terms of their standard achievable capacities at various rates, their Cold Cranking Ability (CCA), their Dynamic Charge Acceptance (DCA) and a simplified PSoCC test. The carbons were classified as an activated carbon and a carbon nano-fiber and were included as a dry weight additive during the standard paste manufacturing process of the negative plate. Cells were built with a 9-plate configuration using standard expanded grid positive plates with a nominal rated capacity of 36 Ah. The cells were formed and subjected to a number of electrochemical tests, of which selected negative plates were then studied using Scanning Electron Microscopy (SEM) and Electrochemical in-situ Atomic Force Microscopy (EC-AFM). The microscopic study was then used to try and relate the observed material characteristics of the NAM with the carbons to the electrochemical results observed when testing a built cell. , Thesis (MA) --Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text:
- Date Issued: 2021-04
On the ideals and semimodules of commutative semirings
- Authors: Olivier, Ruan
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52782 , vital:44026
- Description: Semirings are a generalisation of rings where additive inverses need not exist. In this dissertation, we focus on results of commutative semirings with non-zero identity. Many results that we study are analogous to results from commutative rings with non-zero identity. Properties which are unique to semirings are also investigated, such as semirings where all elements are additively idempotent. The notion of ideals is examined in the context of a semiring. Specifically, prime ideals, maximal ideals, k-ideals and partitioning ideals of semirings are considered. Additionally, the module over a ring is generalised to a semimodule over a semiring. The emphasis is on prime subsemimodules and multiplication semimodules. Lastly, invertible ideals of semirings are examined. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Olivier, Ruan
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52782 , vital:44026
- Description: Semirings are a generalisation of rings where additive inverses need not exist. In this dissertation, we focus on results of commutative semirings with non-zero identity. Many results that we study are analogous to results from commutative rings with non-zero identity. Properties which are unique to semirings are also investigated, such as semirings where all elements are additively idempotent. The notion of ideals is examined in the context of a semiring. Specifically, prime ideals, maximal ideals, k-ideals and partitioning ideals of semirings are considered. Additionally, the module over a ring is generalised to a semimodule over a semiring. The emphasis is on prime subsemimodules and multiplication semimodules. Lastly, invertible ideals of semirings are examined. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text:
- Date Issued: 2021-04
Optimising the uptake of [𝐈𝐫𝐂𝐥𝟔]𝟐− by a diammonium resin: HCl effect and resin performance
- Authors: Ngayeka, Mbokazi Zizipho
- Date: 2021-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54089 , vital:46284
- Description: The separation of [IrCl6]2- from [RhCl5(H2O)]2- by silica microparticles functionalized with 1,10-diamindecane (C10) and quaternized with 4-nitrobenzylchloride (NO2Benz) in various hydrochloric acid mediums was investigated by continuous column studies. The sorbent materials were synthesized using three different routes: Synthesis route 1 (NaI catalyzed synthesis of diammonium functionalized silica microparticles), Synthesis Route 2 (via silylazation of silica followed by functionalization) and Synthesis Route 3 (silane-based sorbent material). The functionalized sorbent materials were characterized by NMR, Microanalysis, SEM-EDS, FT-IR, TGA and BET surface area. The separation efficiency of the quaternary diammonium cations was investigated under dynamic flow adsorption conditions. Preliminary ICP-OES runs were done, at 6 M HCl, to assess which synthesis route gave the best performing sorbent material. [IrCl6]2- selectivity of the sorbent materials was achieved by washing with an HCl solution to remove unadsorbed metal species, then stripping off the [RhCl5(H2O)]2- with 0.05 M of sodium chlorate and the iridium species was eluted with a 20% HCl solution. From the preliminary ICP-OES, loading capacities were calculated, and it was observed that the three sorbent materials from synthesis route 2 (13.89 mg/g for (4) SSC10NO2Benz-A, 1.44 mg/g for (5) SSC10NO2Benz-HoA, and 1.0859 mg/g for (6) SSC10NO2Benz-DoA) showed the highest uptake of [IrCl6]2- and route 1 (1.89 mg/g for (1) SSC10NO2Benz-A, 1.25 mg/g for (2) SSC10NO2Benz-HoA and 0.99 mg/g for (3) SSC10NO2Benz-DoA ) and Route 3 (0.55 mg/g for (7) SC10-AI and 0.755 mg/g for (8) SC10-ACl) materials did not perform efficiently enough, thus were not used further for the HCl study. Within synthesis route 2, three sorbent materials were evaluated, which had varying quantities of the cation: SSC10NO2Benz-A (having a quantity previously used in our research and denoted A), SSC10NO2Benz-HoA (having a quantity Half of A) and SSC10NO2Benz-DoA (having a quantity double of A). SSC10NO2Benz-A showed the highest loading capacity than SSC10NO2Benz-HoA and SSC10NO2Benz-DoA; HCl studies were carried out using SSC10NO2Benz-A. HCl solution having different concentrations (5, 5.5 , 6 , 6.6 and 6.8 M) were used to prepare the metal solutions. This was done to assess which HCl concentration gave the best metal solution containing high amounts of [IrCl6]2- and [RhCl5(H2O)]2-, which would result in a more efficient separation. An auto titrator was used to standardize the HCl concentrations, and the metal ion chloride species solutions were determined by UV-Vis, and their concentrations were confirmed with ICP-OES. Column sorption of iridium and rhodium on SSC10NO2Benz-A using these HCl solutions was carried out, and loading capacities of [IrCl6]2- were obtained. The loading capacities of the 5 M, 5.5 M, 6 M, 6,6 M and 6.8 M HCl solutions for [IrCl6]2- were 2.64, 4.01, 13.89, 18.15 and 7.23 mg/g, respectively. The optimum separation conditions were thus determined by investigating effective parameters such as the method of synthesis, silica to cation ratio, HCl concentration and flow rate. This thesis presents quaternary diammonium sorbent materials that could be applied in feed solutions from ore processing for iridium recovery. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Ngayeka, Mbokazi Zizipho
- Date: 2021-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54089 , vital:46284
- Description: The separation of [IrCl6]2- from [RhCl5(H2O)]2- by silica microparticles functionalized with 1,10-diamindecane (C10) and quaternized with 4-nitrobenzylchloride (NO2Benz) in various hydrochloric acid mediums was investigated by continuous column studies. The sorbent materials were synthesized using three different routes: Synthesis route 1 (NaI catalyzed synthesis of diammonium functionalized silica microparticles), Synthesis Route 2 (via silylazation of silica followed by functionalization) and Synthesis Route 3 (silane-based sorbent material). The functionalized sorbent materials were characterized by NMR, Microanalysis, SEM-EDS, FT-IR, TGA and BET surface area. The separation efficiency of the quaternary diammonium cations was investigated under dynamic flow adsorption conditions. Preliminary ICP-OES runs were done, at 6 M HCl, to assess which synthesis route gave the best performing sorbent material. [IrCl6]2- selectivity of the sorbent materials was achieved by washing with an HCl solution to remove unadsorbed metal species, then stripping off the [RhCl5(H2O)]2- with 0.05 M of sodium chlorate and the iridium species was eluted with a 20% HCl solution. From the preliminary ICP-OES, loading capacities were calculated, and it was observed that the three sorbent materials from synthesis route 2 (13.89 mg/g for (4) SSC10NO2Benz-A, 1.44 mg/g for (5) SSC10NO2Benz-HoA, and 1.0859 mg/g for (6) SSC10NO2Benz-DoA) showed the highest uptake of [IrCl6]2- and route 1 (1.89 mg/g for (1) SSC10NO2Benz-A, 1.25 mg/g for (2) SSC10NO2Benz-HoA and 0.99 mg/g for (3) SSC10NO2Benz-DoA ) and Route 3 (0.55 mg/g for (7) SC10-AI and 0.755 mg/g for (8) SC10-ACl) materials did not perform efficiently enough, thus were not used further for the HCl study. Within synthesis route 2, three sorbent materials were evaluated, which had varying quantities of the cation: SSC10NO2Benz-A (having a quantity previously used in our research and denoted A), SSC10NO2Benz-HoA (having a quantity Half of A) and SSC10NO2Benz-DoA (having a quantity double of A). SSC10NO2Benz-A showed the highest loading capacity than SSC10NO2Benz-HoA and SSC10NO2Benz-DoA; HCl studies were carried out using SSC10NO2Benz-A. HCl solution having different concentrations (5, 5.5 , 6 , 6.6 and 6.8 M) were used to prepare the metal solutions. This was done to assess which HCl concentration gave the best metal solution containing high amounts of [IrCl6]2- and [RhCl5(H2O)]2-, which would result in a more efficient separation. An auto titrator was used to standardize the HCl concentrations, and the metal ion chloride species solutions were determined by UV-Vis, and their concentrations were confirmed with ICP-OES. Column sorption of iridium and rhodium on SSC10NO2Benz-A using these HCl solutions was carried out, and loading capacities of [IrCl6]2- were obtained. The loading capacities of the 5 M, 5.5 M, 6 M, 6,6 M and 6.8 M HCl solutions for [IrCl6]2- were 2.64, 4.01, 13.89, 18.15 and 7.23 mg/g, respectively. The optimum separation conditions were thus determined by investigating effective parameters such as the method of synthesis, silica to cation ratio, HCl concentration and flow rate. This thesis presents quaternary diammonium sorbent materials that could be applied in feed solutions from ore processing for iridium recovery. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text:
- Date Issued: 2021-04
Recreating a wetland at an abandoned saltworks : towards a rehabilitation plan
- Authors: Wasserman, Johan
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52146 , vital:43450
- Description: A saltworks at Swartkops Estuary was abandoned in 2018. While operational, the saltworks hosted some of the largest breeding colonies of several shorebird species in southern Africa and hosted thousands of Palearctic migrant waterbirds annually. The abandonment of the saltworks has resulted in the loss of the artificially managed hydrological regime and therefore the wetland function and habitat value of the site, and the rich and diverse avifauna that once occurred at the site have not returned. The rehabilitation of the saltworks as a wetland that functions as a waterbird sanctuary is currently being organised, and this research aimed to create a plan for implementing and monitoring the rehabilitation. In order to do so, the baseline environmental condition of the abandoned saltworks was established, the possible rehabilitation interventions necessary for rehabilitating the site were assessed, and the potential ecological implications of any interventions were investigated. The assessment of the saltworks’ baseline condition revealed that the site is now characterised by vast expanses of dry hypersaline sediment with sparse patches of monospecific vegetation and depauperate avifauna. The once rich and diverse waterbird communities have all but disappeared since the site was abandoned and are unlikely to return unless a managed hydrological regime is reinstated. Furthermore, it is improbable that salt marsh vegetation will cover the abandoned saltworks primarily due to the high sediment salinity that will persist unless the saltpans are flooded. The area will likely remain barren with little ecological value if no rehabilitation action is taken. Two potential rehabilitation options for reinstating a hydrological regime at the saltworks were identified: (1) pumping estuary water into all of the saltpans; or (2) pumping estuary water into some of the saltpans, while allowing the largest one to be filled with stormwater. Both options were deemed to be feasible; however, the second option will likely have lower running costs. The use of stormwater to fill the one saltpan is expected to result in brackish conditions initially, while the saltpans filled with estuary water would have salinity levels ranging from euhaline to slightly hypersaline. Both the stormwater and estuary water are rich in inorganic nutrients – the estuary water is rich in both dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP), while the stormwater has an exceptionally high DIN content. This raised concerns of creating eutrophic wetlands with detrimental conditions such as algal blooms and a hypoxic water column. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Wasserman, Johan
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52146 , vital:43450
- Description: A saltworks at Swartkops Estuary was abandoned in 2018. While operational, the saltworks hosted some of the largest breeding colonies of several shorebird species in southern Africa and hosted thousands of Palearctic migrant waterbirds annually. The abandonment of the saltworks has resulted in the loss of the artificially managed hydrological regime and therefore the wetland function and habitat value of the site, and the rich and diverse avifauna that once occurred at the site have not returned. The rehabilitation of the saltworks as a wetland that functions as a waterbird sanctuary is currently being organised, and this research aimed to create a plan for implementing and monitoring the rehabilitation. In order to do so, the baseline environmental condition of the abandoned saltworks was established, the possible rehabilitation interventions necessary for rehabilitating the site were assessed, and the potential ecological implications of any interventions were investigated. The assessment of the saltworks’ baseline condition revealed that the site is now characterised by vast expanses of dry hypersaline sediment with sparse patches of monospecific vegetation and depauperate avifauna. The once rich and diverse waterbird communities have all but disappeared since the site was abandoned and are unlikely to return unless a managed hydrological regime is reinstated. Furthermore, it is improbable that salt marsh vegetation will cover the abandoned saltworks primarily due to the high sediment salinity that will persist unless the saltpans are flooded. The area will likely remain barren with little ecological value if no rehabilitation action is taken. Two potential rehabilitation options for reinstating a hydrological regime at the saltworks were identified: (1) pumping estuary water into all of the saltpans; or (2) pumping estuary water into some of the saltpans, while allowing the largest one to be filled with stormwater. Both options were deemed to be feasible; however, the second option will likely have lower running costs. The use of stormwater to fill the one saltpan is expected to result in brackish conditions initially, while the saltpans filled with estuary water would have salinity levels ranging from euhaline to slightly hypersaline. Both the stormwater and estuary water are rich in inorganic nutrients – the estuary water is rich in both dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP), while the stormwater has an exceptionally high DIN content. This raised concerns of creating eutrophic wetlands with detrimental conditions such as algal blooms and a hypoxic water column. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
Rheology behaviour of slurries as a function of particle size and ion concentration
- Authors: Kondlo, Princess Kholiwe
- Date: 2021-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53333 , vital:45141
- Description: In this work, the rheological properties of alumina slurries milled to different particle sizes were investigated. Viscosity increases as the particle size decreases. When increasing amounts of calcium hydroxide, strontium hydroxide or barium hydroxide are added, the viscosity first goes down and then goes up. This can be explained in terms of changes in pH and changes in ionic strength impacting on the surface potential of the particles in suspension. Adding the same concentration of different cations results in different viscosities, with the order being (from high to low viscosity) Ba>Sr>Ca. Effects of partial dissolution of and structural changes to the alumina particles at high pH cannot be excluded. In order to better understanding the different effects, it was attempted to measure the zeta potential of the slurries at different pH values. This resulted in highly positive zeta potential values over the complete pH range, without the observationof an iso-electric point. This does not fit to the observed changes in rheology and contrasts withliterature data. One explanation would be that the measurement system used is unsuitable to yield correct zeta potential values for the materials under investigation. , Thesis (MSc) -- Faculty of Science, Department of Chemistry, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Kondlo, Princess Kholiwe
- Date: 2021-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53333 , vital:45141
- Description: In this work, the rheological properties of alumina slurries milled to different particle sizes were investigated. Viscosity increases as the particle size decreases. When increasing amounts of calcium hydroxide, strontium hydroxide or barium hydroxide are added, the viscosity first goes down and then goes up. This can be explained in terms of changes in pH and changes in ionic strength impacting on the surface potential of the particles in suspension. Adding the same concentration of different cations results in different viscosities, with the order being (from high to low viscosity) Ba>Sr>Ca. Effects of partial dissolution of and structural changes to the alumina particles at high pH cannot be excluded. In order to better understanding the different effects, it was attempted to measure the zeta potential of the slurries at different pH values. This resulted in highly positive zeta potential values over the complete pH range, without the observationof an iso-electric point. This does not fit to the observed changes in rheology and contrasts withliterature data. One explanation would be that the measurement system used is unsuitable to yield correct zeta potential values for the materials under investigation. , Thesis (MSc) -- Faculty of Science, Department of Chemistry, 2021
- Full Text:
- Date Issued: 2021-04
Spatial fisheries management options for inclusion in marine spatial planning in South Africa
- Authors: Reed, Jodie Romay
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/52068 , vital:43451
- Description: Integration of sectoral based management into a coherent and coordinated spatial management framework is one of the central challenges of marine spatial planning ȋMSPȌǤ MSP initiatives aim to provide operational frameworks to promote sustainable use of the economic potential of the ocean while maintaining the value of marine biodiversity and the integrity of marine ecosystems to provide servicesǤ The ecosystem services associated with fisheries in terms of food and job provision are some of the most well recognised and highly valued in the marine realm and maintaining these benefits depends on a holistic understanding of the ecosystemǡ human uses and the management thereofǡ including areaǦbased managementǤ In ͲͰͱǡ South Africa was the first African country to enact MSP legislationǤ The development of MSP was advanced through a Presidential ocean economy initiative ȋOperation Phakisaǣ Oceans EconomyȌ that aimed to fast track marine transport and manufacturingǡ aquacultureǡ and the development of oil and gasǡ small harbourǡ and coastal and marine tourismǤ A dedicated ocean governance component was included to develop an overarchingǡ integrated ocean governance frameworkǤ The absence of fisheries in the plans and initiatives was conspicuousǤ The implementation of MSPǡ howeverǡ provides an opportunity to safeguard the ecosystem services provided by fisheries but only if the interests of fisheries can be adequately reflected in spatial plans and analysesǤ Furthermoreǡ the implementation of MSP may provide new opportunities for innovation in spatial approaches to local fisheries management that could address numerous spatial conflicts that have been reportedǤ Integration of spatial fisheries management approaches into MSP can also support the implementation of ecosystemǦbased management ȋEBMȌǡ by including mechanisms such as habitat protectionǡ effective management of areas important for vulnerable life history stagesǡ and bycatch managementǤ This study aimed to identifyǡ assess and further develop spatial management options for fisheries to facilitate the integration of fisheries management and MSPǤ This was achieved by firstlyǡ identifying existing spatial management instruments and assessing the way in which these instruments may be implemented to support spatial fisheries managementǤ Secondlyǡ the application of two contrasting spatial management optionsǡ applied to two pelagic fisheriesǡ was examined to assess their effectiveness at achieving fisheries management objectives with a focus on bycatch reductionǡ while minimising the costs to the fisheries. , Thesis (PhD) -- Faculty of Science, Ocean Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Reed, Jodie Romay
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/52068 , vital:43451
- Description: Integration of sectoral based management into a coherent and coordinated spatial management framework is one of the central challenges of marine spatial planning ȋMSPȌǤ MSP initiatives aim to provide operational frameworks to promote sustainable use of the economic potential of the ocean while maintaining the value of marine biodiversity and the integrity of marine ecosystems to provide servicesǤ The ecosystem services associated with fisheries in terms of food and job provision are some of the most well recognised and highly valued in the marine realm and maintaining these benefits depends on a holistic understanding of the ecosystemǡ human uses and the management thereofǡ including areaǦbased managementǤ In ͲͰͱǡ South Africa was the first African country to enact MSP legislationǤ The development of MSP was advanced through a Presidential ocean economy initiative ȋOperation Phakisaǣ Oceans EconomyȌ that aimed to fast track marine transport and manufacturingǡ aquacultureǡ and the development of oil and gasǡ small harbourǡ and coastal and marine tourismǤ A dedicated ocean governance component was included to develop an overarchingǡ integrated ocean governance frameworkǤ The absence of fisheries in the plans and initiatives was conspicuousǤ The implementation of MSPǡ howeverǡ provides an opportunity to safeguard the ecosystem services provided by fisheries but only if the interests of fisheries can be adequately reflected in spatial plans and analysesǤ Furthermoreǡ the implementation of MSP may provide new opportunities for innovation in spatial approaches to local fisheries management that could address numerous spatial conflicts that have been reportedǤ Integration of spatial fisheries management approaches into MSP can also support the implementation of ecosystemǦbased management ȋEBMȌǡ by including mechanisms such as habitat protectionǡ effective management of areas important for vulnerable life history stagesǡ and bycatch managementǤ This study aimed to identifyǡ assess and further develop spatial management options for fisheries to facilitate the integration of fisheries management and MSPǤ This was achieved by firstlyǡ identifying existing spatial management instruments and assessing the way in which these instruments may be implemented to support spatial fisheries managementǤ Secondlyǡ the application of two contrasting spatial management optionsǡ applied to two pelagic fisheriesǡ was examined to assess their effectiveness at achieving fisheries management objectives with a focus on bycatch reductionǡ while minimising the costs to the fisheries. , Thesis (PhD) -- Faculty of Science, Ocean Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
Testing alternative Pinus species and hybrids for the South African structural pole market
- Authors: Ndovela, Lisakhanya Sizo
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52002 , vital:43435
- Description: According to the South African National Standards, only Pinus canariensis, Pinus pinaster and Pinus radiata are suitable to be used as structural softwood poles. Of the three Pinus species mentioned, only P. radiata is still planted in South Africa and its future and availability is uncertain. The lack of availability of structural pine poles necessitates the South African forestry industry to look at alternative softwood species to plant. The broad aim of this study was to determine whether there are alternative Pinus species or hybrids that can be planted in South Africa’s Western and Southern Cape areas that will have suitable properties to be used as a resource for structural poles. This document reports on the testing of the strength and stiffness, as well as other relevant properties, of poles from several Pinus species and Pinus hybrids. The poles were derived from thinned eight-year-old tree stands in Knysna, Western Cape. Poles were peeled, kiln dried and graded before bending tests were carried out. Species and hybrids were also assessed for differences within a tree along the length. Also, the correlation between modulus of rupture (MOR), modulus of elasticity (MOE) and wood grading properties was evaluated. The results showed that there was a highly significant effect of species and log position on the mean MOR of the poles. In general, poles from the bottom of the tree had a higher mean MOR than poles from the top of the tree. There was also a highly significant effect of species and pole position on the mean MOE of poles, with poles at the top of the trees generally having higher MOE values. A very concerning finding was that the 5th percentile MOR and mean MOE values of all the species were far lower than required by SANS 10163-1 (2003). Even for the best performing species, P. radiata, the MOR 5th percentile value was less than half the required value, while the mean MOE was also 39% lower than the required mean MOE. Apart from P. radiata, the P. maximinoi performed the best of all species and hybrids since it had a statistically similar mean MOR and MOE to P. radiata. P. elliottii and the hybrid P. elliottii x caribaea had statistically significant lower MOR and MOE than P. radiata. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Ndovela, Lisakhanya Sizo
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52002 , vital:43435
- Description: According to the South African National Standards, only Pinus canariensis, Pinus pinaster and Pinus radiata are suitable to be used as structural softwood poles. Of the three Pinus species mentioned, only P. radiata is still planted in South Africa and its future and availability is uncertain. The lack of availability of structural pine poles necessitates the South African forestry industry to look at alternative softwood species to plant. The broad aim of this study was to determine whether there are alternative Pinus species or hybrids that can be planted in South Africa’s Western and Southern Cape areas that will have suitable properties to be used as a resource for structural poles. This document reports on the testing of the strength and stiffness, as well as other relevant properties, of poles from several Pinus species and Pinus hybrids. The poles were derived from thinned eight-year-old tree stands in Knysna, Western Cape. Poles were peeled, kiln dried and graded before bending tests were carried out. Species and hybrids were also assessed for differences within a tree along the length. Also, the correlation between modulus of rupture (MOR), modulus of elasticity (MOE) and wood grading properties was evaluated. The results showed that there was a highly significant effect of species and log position on the mean MOR of the poles. In general, poles from the bottom of the tree had a higher mean MOR than poles from the top of the tree. There was also a highly significant effect of species and pole position on the mean MOE of poles, with poles at the top of the trees generally having higher MOE values. A very concerning finding was that the 5th percentile MOR and mean MOE values of all the species were far lower than required by SANS 10163-1 (2003). Even for the best performing species, P. radiata, the MOR 5th percentile value was less than half the required value, while the mean MOE was also 39% lower than the required mean MOE. Apart from P. radiata, the P. maximinoi performed the best of all species and hybrids since it had a statistically similar mean MOR and MOE to P. radiata. P. elliottii and the hybrid P. elliottii x caribaea had statistically significant lower MOR and MOE than P. radiata. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text: false
- Date Issued: 2021-04
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