Geological and geophysical investigations of groundwater resource in the area of Ndlambe Municipality, Eastern Cape Province, South Africa.
- Authors: Mpofu, Mthulisi
- Date: 2020
- Subjects: Groundwater Geophysical surveys
- Language: English
- Type: Thesis , Masters , MSc (Geology)
- Identifier: http://hdl.handle.net/10353/18755 , vital:42730
- Description: Groundwater is an essential resource contributing extensively to overall total annual supply. However, overexploitation has depleted groundwater availability significantly and also brought about land subsidence at some places. The evaluation of groundwater potential zones is essential in protecting the quality of water and managing of groundwater structures. The Eastern Cape Province is one of the provinces faced with the challenge of supplying clean fresh water to the communities residing in it. Ndlambe municipality is a case in point where people rely on groundwater for agriculture and domestic activities. Few studies have been undertaken to evaluate groundwater resource in the study area. This study aims to assess groundwater resources as a way of achieving the goal of water sustainability. In the southeast of the Cape Fold Belt (CBF), is the Ndlambe municipality underneath folded Cape and Karoo Supergroup rocks. The rock sequence in the region reflects the geological history over a considerable period. In general, the area of study comprises of the Bokkeveld and Witteberg groups. The Bokkeveld comprises of shale along with sandstone whilst the Witteberg Group consists predominantly of quartzites with minor interbedded shales. The aims of the study were to target potential zones for groundwater exploration, analyse zones of lineaments, investigate the networks of fractures and the mineralogy of the area of study. In line with studies for groundwater exploration, a number of methods were undertaken for obtaining the results. These included literature review, remote sensing and geographic information system, thin section analysis, scanning electron microscope (SEM), X-ray fluorescence (XRF), structural analysis and geophysical investigations (magnetic and vertical electrical sounding). Potential zones for groundwater were identified using remote sensing techniques and geographical information systems (GIS). Maps were generated using GIS tools. Geology, slope, lineaments and Normalised Difference Vegetation Index (NDVI) were considered as parameters for determining groundwater potential zones. A geological and geophysical study was conducted in the Ndlambe municipality. Twelve samples for thin sections, 12 samples for XRF analysis and 4 samples for SEM analysis were collected at different locations in the area of study and were analysed. Thin section analysis revealed that quartz arenite has been metamorphosed to quartzite due to high pressure and temperatures and the cracks in the quartz grains are due to pressure and brittle deformation that has in turn enhanced secondary porosity resulting in joints and fractures which are good for groundwater movement. Scanning electron microscopy complemented the findings from optical microscopy by revealing splatter pores which are due to intense fracturing and these contribute to increasing permeability of the rock structures. XRF revealed the chemical composition of various rock types in the area of study. The analysed samples were dominated by silica reflecting their source from weathering of silicate rocks. The Chemical Index of Alteration (CIA) and Al2O3 values of the analysed samples reflected moderate to intensive weathering. In the study area, three main hydrogeologically important structures were taken into account. These included primary structures (bedding), contacts (geological) and secondary structures like fractures and folds. The study area comprises of several faults that are an important factor for porosity and permeability. The study area is dominated by blocky quartz veins that have been crushed due to compression hence higher permeability of groundwater. The Syscal Pro multichannel resistivity equipment was used to conduct the survey using the Schlumberger- Dipole-dipole array on three lines of varying length (350 m, 530 m and 340 m). Data collected were processed using RES2DINV software, producing a subsurface 2-D geoelectrical model from the pseudosections of apparent resistivity. Low resistivities in the study area were inferred to be weathered moist sandstone while low resistivities with depth indicated an overlying zone of fractured sandstone and quartzite which may be hosting some groundwater. An area of low resistivity zones between two large bodies suggests that the massive rock bodies are being weathered and fractured and fractures act as conduits for groundwater. High resistivity values indicate hard rock bodies that are unweathered hence low potential zone for groundwater localisation. The ground magnetic survey was used to delineate the subsurface structures as these control groundwater potential.
- Full Text:
- Date Issued: 2020
- Authors: Mpofu, Mthulisi
- Date: 2020
- Subjects: Groundwater Geophysical surveys
- Language: English
- Type: Thesis , Masters , MSc (Geology)
- Identifier: http://hdl.handle.net/10353/18755 , vital:42730
- Description: Groundwater is an essential resource contributing extensively to overall total annual supply. However, overexploitation has depleted groundwater availability significantly and also brought about land subsidence at some places. The evaluation of groundwater potential zones is essential in protecting the quality of water and managing of groundwater structures. The Eastern Cape Province is one of the provinces faced with the challenge of supplying clean fresh water to the communities residing in it. Ndlambe municipality is a case in point where people rely on groundwater for agriculture and domestic activities. Few studies have been undertaken to evaluate groundwater resource in the study area. This study aims to assess groundwater resources as a way of achieving the goal of water sustainability. In the southeast of the Cape Fold Belt (CBF), is the Ndlambe municipality underneath folded Cape and Karoo Supergroup rocks. The rock sequence in the region reflects the geological history over a considerable period. In general, the area of study comprises of the Bokkeveld and Witteberg groups. The Bokkeveld comprises of shale along with sandstone whilst the Witteberg Group consists predominantly of quartzites with minor interbedded shales. The aims of the study were to target potential zones for groundwater exploration, analyse zones of lineaments, investigate the networks of fractures and the mineralogy of the area of study. In line with studies for groundwater exploration, a number of methods were undertaken for obtaining the results. These included literature review, remote sensing and geographic information system, thin section analysis, scanning electron microscope (SEM), X-ray fluorescence (XRF), structural analysis and geophysical investigations (magnetic and vertical electrical sounding). Potential zones for groundwater were identified using remote sensing techniques and geographical information systems (GIS). Maps were generated using GIS tools. Geology, slope, lineaments and Normalised Difference Vegetation Index (NDVI) were considered as parameters for determining groundwater potential zones. A geological and geophysical study was conducted in the Ndlambe municipality. Twelve samples for thin sections, 12 samples for XRF analysis and 4 samples for SEM analysis were collected at different locations in the area of study and were analysed. Thin section analysis revealed that quartz arenite has been metamorphosed to quartzite due to high pressure and temperatures and the cracks in the quartz grains are due to pressure and brittle deformation that has in turn enhanced secondary porosity resulting in joints and fractures which are good for groundwater movement. Scanning electron microscopy complemented the findings from optical microscopy by revealing splatter pores which are due to intense fracturing and these contribute to increasing permeability of the rock structures. XRF revealed the chemical composition of various rock types in the area of study. The analysed samples were dominated by silica reflecting their source from weathering of silicate rocks. The Chemical Index of Alteration (CIA) and Al2O3 values of the analysed samples reflected moderate to intensive weathering. In the study area, three main hydrogeologically important structures were taken into account. These included primary structures (bedding), contacts (geological) and secondary structures like fractures and folds. The study area comprises of several faults that are an important factor for porosity and permeability. The study area is dominated by blocky quartz veins that have been crushed due to compression hence higher permeability of groundwater. The Syscal Pro multichannel resistivity equipment was used to conduct the survey using the Schlumberger- Dipole-dipole array on three lines of varying length (350 m, 530 m and 340 m). Data collected were processed using RES2DINV software, producing a subsurface 2-D geoelectrical model from the pseudosections of apparent resistivity. Low resistivities in the study area were inferred to be weathered moist sandstone while low resistivities with depth indicated an overlying zone of fractured sandstone and quartzite which may be hosting some groundwater. An area of low resistivity zones between two large bodies suggests that the massive rock bodies are being weathered and fractured and fractures act as conduits for groundwater. High resistivity values indicate hard rock bodies that are unweathered hence low potential zone for groundwater localisation. The ground magnetic survey was used to delineate the subsurface structures as these control groundwater potential.
- Full Text:
- Date Issued: 2020
Mineralogy, geochemistry and pebble morphology of the Katberg Formation around Graaff Reinet and East London, Eastern Cape province of South Africa
- Authors: Ndlazi, Nondumiso Zandile
- Date: 2020
- Subjects: Mineralogy|
- Language: English
- Type: Thesis , Masters , MSc (Geology)
- Identifier: http://hdl.handle.net/10353/18631 , vital:42615
- Description: The Katberg Formation forms the upper part of the Tarkastad Subgroup in the Beaufort Group of the main Karoo Supergroup. The Katberg Formation consists of siliciclastic sedimentary rocks mostly dominated by greyish sandstone, red mudstone with minor siltstone occurrences. The Katberg Formation also consists of calcareous and ferruginous concretions that formed during diagenesis. Braided streams deposited the Katberg Formation with a predominantly sand bed load. The Katberg Formation sandstones contain pebbles with no true conglomerates identified in the study area. This study was conducted in the Katberg Formation to understand the mineralogy, geochemistry, and pebble morphology around Graaff Reinet and East London areas. The major and trace elements were analyzed through X-Ray Fluorescence (XRF) to deduce the source rock provenance, tectonic setting, paleo-weathering conditions, climatic conditions, and sediment maturity. The X-Ray Diffraction (XRD) was used to highlight a detailed distribution and variation of mineralogical polymorphs of the minerals present in sandstones and mudstones. The pebble morphology was used to confirm the depositional environment of the Katberg Formation. The use of The bivariate plots of the Maximum Projection Sphericity Index (MPSI) and the Oblate-Prolate Index (OPI) showed that 79 % of pebbles fall in the fluvial environment, whereas 21 % of pebbles fall in the beach environment. A small proportion of beach pebbles within the Katberg Formation suggests that the river reached the marginal marine environment during its flow. The majority of the pebbles yielded a bladed shape with a dominating Sphericity Index symptomatic of fluvial sediments. All the bivariate plots illustrate the fluvial depositional environment for the sediments of the Katberg Formation. Petrographic studies based on the prepared 15 thin sections indicated that the Katberg Formation rocks are dominated by quartz, feldspar, and clay minerals. However, they show more plagioclase feldspar than k-feldspars. The grains are poorly sorted and immature, with irregular grain sizes and shapes. The angularity of clasts indicates that the grains have travelled shorter distances. The abundance of feldspar minerals suggests that the arkose sandstone was derived either from situ or from a short distance. The albitization of plagioclase to illite and the replacement of plagioclase feldspars by calcite and laumontite is very common in the Katberg Formation, which points out deep burial diagenesis. The XRD analysis revealed the occurrence of 14 minerals in the siliciclastic rocks of the Katberg Formation, namely: quartz, albite, clinochlore, muscovite, phlogopite, annite, illite, orthoclase, anorthoclase, laumontite, calcite, and ankerite. Amongst these minerals, albite, clinochlore, muscovite, and phlogopite show variation in crystal forms known as polymorphs. Geochemical analysis of the Katberg Formation sandstones and mudrocks revealed that all samples show a high concentration of SiO2, Al2O3, Fe2O3, K2O, Na2O, CaO, and MgO. The trace elements: TiO2, MnO, P2O5, BaO, SrO, ZrO2, and V2O5 are depleted with values ranging below 1 wt %. The geochemical classification of the Katberg Formation sandstones revealed the origin from wacke and arkose sources. The geochemical diagrams and indices of paleoweathering conditions suggested that the Katberg Formation underwent a moderate degree of chemical weathering. The geochemistry revealed that the sediments were 4 Final Submission of Thesis, Dissertation or Research Report/Project, Conference or Exam Paper deposited during the arid climate conditions. The studied sandstone and mudstone samples pointed an active continental margin and passive margin tectonic setting of the Katberg Formation.
- Full Text:
- Date Issued: 2020
- Authors: Ndlazi, Nondumiso Zandile
- Date: 2020
- Subjects: Mineralogy|
- Language: English
- Type: Thesis , Masters , MSc (Geology)
- Identifier: http://hdl.handle.net/10353/18631 , vital:42615
- Description: The Katberg Formation forms the upper part of the Tarkastad Subgroup in the Beaufort Group of the main Karoo Supergroup. The Katberg Formation consists of siliciclastic sedimentary rocks mostly dominated by greyish sandstone, red mudstone with minor siltstone occurrences. The Katberg Formation also consists of calcareous and ferruginous concretions that formed during diagenesis. Braided streams deposited the Katberg Formation with a predominantly sand bed load. The Katberg Formation sandstones contain pebbles with no true conglomerates identified in the study area. This study was conducted in the Katberg Formation to understand the mineralogy, geochemistry, and pebble morphology around Graaff Reinet and East London areas. The major and trace elements were analyzed through X-Ray Fluorescence (XRF) to deduce the source rock provenance, tectonic setting, paleo-weathering conditions, climatic conditions, and sediment maturity. The X-Ray Diffraction (XRD) was used to highlight a detailed distribution and variation of mineralogical polymorphs of the minerals present in sandstones and mudstones. The pebble morphology was used to confirm the depositional environment of the Katberg Formation. The use of The bivariate plots of the Maximum Projection Sphericity Index (MPSI) and the Oblate-Prolate Index (OPI) showed that 79 % of pebbles fall in the fluvial environment, whereas 21 % of pebbles fall in the beach environment. A small proportion of beach pebbles within the Katberg Formation suggests that the river reached the marginal marine environment during its flow. The majority of the pebbles yielded a bladed shape with a dominating Sphericity Index symptomatic of fluvial sediments. All the bivariate plots illustrate the fluvial depositional environment for the sediments of the Katberg Formation. Petrographic studies based on the prepared 15 thin sections indicated that the Katberg Formation rocks are dominated by quartz, feldspar, and clay minerals. However, they show more plagioclase feldspar than k-feldspars. The grains are poorly sorted and immature, with irregular grain sizes and shapes. The angularity of clasts indicates that the grains have travelled shorter distances. The abundance of feldspar minerals suggests that the arkose sandstone was derived either from situ or from a short distance. The albitization of plagioclase to illite and the replacement of plagioclase feldspars by calcite and laumontite is very common in the Katberg Formation, which points out deep burial diagenesis. The XRD analysis revealed the occurrence of 14 minerals in the siliciclastic rocks of the Katberg Formation, namely: quartz, albite, clinochlore, muscovite, phlogopite, annite, illite, orthoclase, anorthoclase, laumontite, calcite, and ankerite. Amongst these minerals, albite, clinochlore, muscovite, and phlogopite show variation in crystal forms known as polymorphs. Geochemical analysis of the Katberg Formation sandstones and mudrocks revealed that all samples show a high concentration of SiO2, Al2O3, Fe2O3, K2O, Na2O, CaO, and MgO. The trace elements: TiO2, MnO, P2O5, BaO, SrO, ZrO2, and V2O5 are depleted with values ranging below 1 wt %. The geochemical classification of the Katberg Formation sandstones revealed the origin from wacke and arkose sources. The geochemical diagrams and indices of paleoweathering conditions suggested that the Katberg Formation underwent a moderate degree of chemical weathering. The geochemistry revealed that the sediments were 4 Final Submission of Thesis, Dissertation or Research Report/Project, Conference or Exam Paper deposited during the arid climate conditions. The studied sandstone and mudstone samples pointed an active continental margin and passive margin tectonic setting of the Katberg Formation.
- Full Text:
- Date Issued: 2020
Evaluation of groundwater potential based on hybrid approach of geology, geophysics, and geoinformatics: Case study of Buffalo Catchment area, Eastern Cape, South Africa
- Authors: Owolabi,Solomon T
- Date: 2019
- Subjects: Hydrogeology Geology
- Language: English
- Type: Thesis , Doctoral , PhD (Geology)
- Identifier: http://hdl.handle.net/10353/12238 , vital:39218
- Description: This study focuses on the feasibility of exploring potential groundwater zones through assessment of catchment geo-hydrodynamic processes, using hydro-statistic principles and geographic information system-based approaches. The research work integrated analysis of hydrologic variables, geologic structures, and geomorpho-tectonic processes that provide information on spatial variability of hydrologic units in a watershed. The study is aimed at improving conceptual knowledge and presenting the technical feasibility of exploring potential groundwater zones through geo-hydrodynamic perspectives in hydrogeologically challenged environments. The study adopted a case design approach at the Buffalo hydrologic basin headwater in Eastern Cape, South Africa. The methods used in this study include: field mapping of geologic units and structures, digital processing of aeromagnetic map, cross-section profiling of borehole logs, auto-extraction of lineament, streamflow variability and recession assessment, geomorpho-tectonic analysis of surficial drainage pattern, vertical electrical sounding for imaging shallow subsurface layers, and geospatial integration of thematic maps of groundwater multi-influencing factors. The results indicate that the hydrogeological settings of Buffalo watershed comprised of good, moderate, fair, poor and very poor groundwater potential zones which cover 187 km2 , 338 km2 , 406 km2 , 185 km2 , and 121 km2 respectively. The results report that the groundwater system of Buffalo watershed is mainly hosted by the well-drained fractured dolerite and the shallow unconfined sandstone aquifer. The aquifer is bounded by two parallel impermeable valley walls in the north and south. Also, the Buffalo drainage system constitutes a variable head boundary as a groundwater discharge zone. The groundwater discharge which mostly occurs at the Tshoxa upper course, Mgqakwebe, Quencwe, Yellowwoods upper course and the Buffalo River center influence the status of the Buffalo River as a perennial river system. vi The groundwater recharge occurs through the networks of surficial lineaments and fractures concentrated on the sandstone lithosome, mostly in the northern half of the watershed. The surficial tectonic features trend in a WNW-ESE and E-W direction. The groundwater flow system is controlled by the subsurface lineaments which are oriented in west-northwest – eastsoutheast direction. Most of the groundwater recharge is driven by rain which is extreme at the north. The hydro-climatic pattern of the region influences the dendritic drainage system of Buffalo watershed. The geologic characterization and geomorpho-tectonic analysis indicate that the geologic settings are made up of upward-fining lithologic material and siliciclastic materials that were deposited as fill in paleochannels by braided and meandering fluvial systems. The variability in dissection property and the fluvial system indicates that Buffalo hydrologic and geomorphic systems are heterogeneous and complex. The possible impact of these variabilities aligns with the report of geoelectric sections which revealed the heterogeneity of the aquifer intrinsic properties and variability in groundwater yield. The electric resistivity tomography revealed the existence of a fault system and variation in the thickness of the aquifer. Hydrologic characterization indicates the vulnerability status of the rivers within the watershed. In particular, the Ngqokweni River is vulnerable to diminution while Quencwe River has the potential for a flash flood. Buffalo station is an important surface water capture zone. Delineation of groundwater potential zone should incorporate geologic, hydrologic, geophysical, geomorphotectonic, and environmental perspectives due to the inherent relationship among influencing factors. The study therefore identifies groundwater capture zones which can be further explored for groundwater development and to mitigate the stake of water shortage. The study therefore recommends the approach here to the department of water affairs for adoption to map the zones of groundwater potential at a regional scale. The study also provides resourceful information on vii groundwater recharge zones and therefore recommends that the environment and water stakeholders work together to protect the recharge zones from groundwater contamination due to land use
- Full Text:
- Date Issued: 2019
- Authors: Owolabi,Solomon T
- Date: 2019
- Subjects: Hydrogeology Geology
- Language: English
- Type: Thesis , Doctoral , PhD (Geology)
- Identifier: http://hdl.handle.net/10353/12238 , vital:39218
- Description: This study focuses on the feasibility of exploring potential groundwater zones through assessment of catchment geo-hydrodynamic processes, using hydro-statistic principles and geographic information system-based approaches. The research work integrated analysis of hydrologic variables, geologic structures, and geomorpho-tectonic processes that provide information on spatial variability of hydrologic units in a watershed. The study is aimed at improving conceptual knowledge and presenting the technical feasibility of exploring potential groundwater zones through geo-hydrodynamic perspectives in hydrogeologically challenged environments. The study adopted a case design approach at the Buffalo hydrologic basin headwater in Eastern Cape, South Africa. The methods used in this study include: field mapping of geologic units and structures, digital processing of aeromagnetic map, cross-section profiling of borehole logs, auto-extraction of lineament, streamflow variability and recession assessment, geomorpho-tectonic analysis of surficial drainage pattern, vertical electrical sounding for imaging shallow subsurface layers, and geospatial integration of thematic maps of groundwater multi-influencing factors. The results indicate that the hydrogeological settings of Buffalo watershed comprised of good, moderate, fair, poor and very poor groundwater potential zones which cover 187 km2 , 338 km2 , 406 km2 , 185 km2 , and 121 km2 respectively. The results report that the groundwater system of Buffalo watershed is mainly hosted by the well-drained fractured dolerite and the shallow unconfined sandstone aquifer. The aquifer is bounded by two parallel impermeable valley walls in the north and south. Also, the Buffalo drainage system constitutes a variable head boundary as a groundwater discharge zone. The groundwater discharge which mostly occurs at the Tshoxa upper course, Mgqakwebe, Quencwe, Yellowwoods upper course and the Buffalo River center influence the status of the Buffalo River as a perennial river system. vi The groundwater recharge occurs through the networks of surficial lineaments and fractures concentrated on the sandstone lithosome, mostly in the northern half of the watershed. The surficial tectonic features trend in a WNW-ESE and E-W direction. The groundwater flow system is controlled by the subsurface lineaments which are oriented in west-northwest – eastsoutheast direction. Most of the groundwater recharge is driven by rain which is extreme at the north. The hydro-climatic pattern of the region influences the dendritic drainage system of Buffalo watershed. The geologic characterization and geomorpho-tectonic analysis indicate that the geologic settings are made up of upward-fining lithologic material and siliciclastic materials that were deposited as fill in paleochannels by braided and meandering fluvial systems. The variability in dissection property and the fluvial system indicates that Buffalo hydrologic and geomorphic systems are heterogeneous and complex. The possible impact of these variabilities aligns with the report of geoelectric sections which revealed the heterogeneity of the aquifer intrinsic properties and variability in groundwater yield. The electric resistivity tomography revealed the existence of a fault system and variation in the thickness of the aquifer. Hydrologic characterization indicates the vulnerability status of the rivers within the watershed. In particular, the Ngqokweni River is vulnerable to diminution while Quencwe River has the potential for a flash flood. Buffalo station is an important surface water capture zone. Delineation of groundwater potential zone should incorporate geologic, hydrologic, geophysical, geomorphotectonic, and environmental perspectives due to the inherent relationship among influencing factors. The study therefore identifies groundwater capture zones which can be further explored for groundwater development and to mitigate the stake of water shortage. The study therefore recommends the approach here to the department of water affairs for adoption to map the zones of groundwater potential at a regional scale. The study also provides resourceful information on vii groundwater recharge zones and therefore recommends that the environment and water stakeholders work together to protect the recharge zones from groundwater contamination due to land use
- Full Text:
- Date Issued: 2019
Geological and geophysical assessment of groundwater vulnerability to contamination in selected general landfill sites in the Eastern Cape Province, South Africa
- Authors: Mepaiyeda, Seyi
- Date: 2019
- Subjects: Groundwater -- Pollution Sanitary landfills
- Language: English
- Type: Thesis , Doctoral , PhD (Geology)
- Identifier: http://hdl.handle.net/10353/12227 , vital:39217
- Description: Increasing expansion, population and urbanization have resulted in high volume of waste generated daily in South Africa. Most municipalities in the Eastern Cape are experiencing challenges in effective waste disposal, thus resulting in pollution of the air, soil and groundwater by the percolation of harmful contaminants into the environment from landfill leachate. Groundwater resources are limited in South Africa due to itssemi-arid nature. Also, there islimited information available, not only about where it occurs but how to manage it so that its quality does not depreciate to unacceptable levels. A combination of these factors coupled with a gap between waste policy and its subsequent implementation may be disastrous to South Africa. This research examines the impact of landfill sites on groundwater resources at three selected sites in the Eastern Cape Province using an integrated geological and geophysical approach. The methodology adopted include: an exhaustive literature review on waste management policies and practices in South Africa and Eastern Cape specifically. It also involved remote sensing for the study of geomorphology and structural interpretations of lineaments. Field excursions, analysis of physico-chemical and geochemical properties of groundwater obtained from monitoring boreholes and leachate pond in the vicinity of the landfill sites was also carried out. Combined induced polarization (IP) and electrical resistivity measurements for geophysical assessment of groundwater vulnerability and petrographical analysis was alos adopted. Data analysis and interpretation of the obtained results showed that the selected landfill sites are generally characterized by a 4-layer Earth structure with an average depth to top of the bedrock between 15 m - 30 m. Plant-rock association observed from the aerial photo-interpretation showed groundwater potential around the locality of the landfill sites with a dendritic to poorly drained x patterns and moderate to high topography. Structural controls such as the presence of lineaments and a fractured bedrock beneath, which are excellent pathways for the migration of leachate, particularly at the Berlin and King Williams Town landfill sites were observed. Analysis of physico-chemical and geochemical properties of water samples showed contamination of the groundwater by heavy metals and some of the physico-chemical properties were above the generally acceptable limits (WHO). These include high electrical conductivity (EC) and total dissolved solid (TDS) values observed in the groundwater samples from the King Williams Town landfill which indicated a downward transfer of leachate into the groundwater. The difference in EC and TDS values for boreholes BH2 and BH1 (9892 µS/cm, 4939 mg/L and 6988 µS/cm, 3497 mg/L respectively), showed that concentration of contaminants increased towards the centre of the landfill. Interpretation of the obtained results from the Berlin landfill showed the presence of heavy metals in groundwater samples in high concentrations. This indicated the dumping of toxic and hazardous waste substances on the landfill, contrary to the landfill design and classification. This could have harmful effect on plants and animals. Integrated geophysical assessment showed the presence of leachate plumes on pseudosections across the landfill sites. This was further corroborated on the chargeability pseudosections. Resistivity and IP pseudosections from the Berlin landfill showed a 4-layered Earth structure and anomalous zones of resistivity (≤ 112 Ώ-m) and low chargeability (≤1.25 ms) in the top layers. This is indicative of percolating leachate plume in the unsaturated zone. Contaminants ranging from unsaturated waste with high ion content to dense aqueous phase liquid contaminants, characterized by low resistivity (34 Ώm to 80 Ώ-m) and low chargeability values (0.05 ms to 5.75 ms) were identified across the Alice landfill. Results from the King Williams Town Landfill revealed plume contamination to a depth of about 75 m, well within the aquiferous zone. xi It is suggested that waste disposal practices should be improved by proper waste inspection and classification at landfills prior to disposal, use of lining and cap material to prevent leaching of contaminants into the groundwater below and the construction of waste cells and containment structures. This will go a long way in mitigating groundwater contamination due to landfilling at the study areas
- Full Text:
- Date Issued: 2019
- Authors: Mepaiyeda, Seyi
- Date: 2019
- Subjects: Groundwater -- Pollution Sanitary landfills
- Language: English
- Type: Thesis , Doctoral , PhD (Geology)
- Identifier: http://hdl.handle.net/10353/12227 , vital:39217
- Description: Increasing expansion, population and urbanization have resulted in high volume of waste generated daily in South Africa. Most municipalities in the Eastern Cape are experiencing challenges in effective waste disposal, thus resulting in pollution of the air, soil and groundwater by the percolation of harmful contaminants into the environment from landfill leachate. Groundwater resources are limited in South Africa due to itssemi-arid nature. Also, there islimited information available, not only about where it occurs but how to manage it so that its quality does not depreciate to unacceptable levels. A combination of these factors coupled with a gap between waste policy and its subsequent implementation may be disastrous to South Africa. This research examines the impact of landfill sites on groundwater resources at three selected sites in the Eastern Cape Province using an integrated geological and geophysical approach. The methodology adopted include: an exhaustive literature review on waste management policies and practices in South Africa and Eastern Cape specifically. It also involved remote sensing for the study of geomorphology and structural interpretations of lineaments. Field excursions, analysis of physico-chemical and geochemical properties of groundwater obtained from monitoring boreholes and leachate pond in the vicinity of the landfill sites was also carried out. Combined induced polarization (IP) and electrical resistivity measurements for geophysical assessment of groundwater vulnerability and petrographical analysis was alos adopted. Data analysis and interpretation of the obtained results showed that the selected landfill sites are generally characterized by a 4-layer Earth structure with an average depth to top of the bedrock between 15 m - 30 m. Plant-rock association observed from the aerial photo-interpretation showed groundwater potential around the locality of the landfill sites with a dendritic to poorly drained x patterns and moderate to high topography. Structural controls such as the presence of lineaments and a fractured bedrock beneath, which are excellent pathways for the migration of leachate, particularly at the Berlin and King Williams Town landfill sites were observed. Analysis of physico-chemical and geochemical properties of water samples showed contamination of the groundwater by heavy metals and some of the physico-chemical properties were above the generally acceptable limits (WHO). These include high electrical conductivity (EC) and total dissolved solid (TDS) values observed in the groundwater samples from the King Williams Town landfill which indicated a downward transfer of leachate into the groundwater. The difference in EC and TDS values for boreholes BH2 and BH1 (9892 µS/cm, 4939 mg/L and 6988 µS/cm, 3497 mg/L respectively), showed that concentration of contaminants increased towards the centre of the landfill. Interpretation of the obtained results from the Berlin landfill showed the presence of heavy metals in groundwater samples in high concentrations. This indicated the dumping of toxic and hazardous waste substances on the landfill, contrary to the landfill design and classification. This could have harmful effect on plants and animals. Integrated geophysical assessment showed the presence of leachate plumes on pseudosections across the landfill sites. This was further corroborated on the chargeability pseudosections. Resistivity and IP pseudosections from the Berlin landfill showed a 4-layered Earth structure and anomalous zones of resistivity (≤ 112 Ώ-m) and low chargeability (≤1.25 ms) in the top layers. This is indicative of percolating leachate plume in the unsaturated zone. Contaminants ranging from unsaturated waste with high ion content to dense aqueous phase liquid contaminants, characterized by low resistivity (34 Ώm to 80 Ώ-m) and low chargeability values (0.05 ms to 5.75 ms) were identified across the Alice landfill. Results from the King Williams Town Landfill revealed plume contamination to a depth of about 75 m, well within the aquiferous zone. xi It is suggested that waste disposal practices should be improved by proper waste inspection and classification at landfills prior to disposal, use of lining and cap material to prevent leaching of contaminants into the groundwater below and the construction of waste cells and containment structures. This will go a long way in mitigating groundwater contamination due to landfilling at the study areas
- Full Text:
- Date Issued: 2019
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