A geochemical investigation of the waters and sediments of De Hoop Vlei, Bredasdorp district, South Africa

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dc.contributor.advisorWillis, Jamesen_ZA
dc.contributor.advisorFey, Martin Ven_ZA
dc.contributor.authorLanz, Johannen_ZA
dc.date.accessioned2016-07-04T08:42:00Z
dc.date.available2016-07-04T08:42:00Z
dc.date.issued1997en_ZA
dc.descriptionBibliography: pages 117-121.en_ZA
dc.description.abstractDe Hoop Vlei is a saline coastal lake situated 53 kilometres north-east of Cape Agulhas in the Western Cape Province of South Africa. It is probably of estuarine origin but is now separated from the sea by mobile sand dunes and, therefore, has no surface outflow. Inflow to the vlei is from a catchment area of approximately 1200 km2 in which intensive grain farming is practised. The vlei is situated within the De. Hoop Nature Reserve and its ecological value, particularly as a breeding ground for water birds, has been recognised in its designation as an international RAMSAR conservation site. Agricultural practices in the catchment have been identified as a potential threat to the ecology of the vlei. The overall objective of this study was to provide a geochemical characterisation of De Hoop Vlei. It focused on identifying the geochemical factors and processes which control the water chemistry of the vlei and attempted to identify any influence of agricultural activities on water quality. This was achieved through a geochemical interpretation of the results obtained from analyses of water and sediment samples collected during the study. Use was also made of Department of Water Affairs and Forestry monitoring data in order to examine long term behaviour of the system, particularly with respect to the effect of evaporative concentration on water composition. Furthermore, chemical equilibrium was modelled, using the geochemical model MINTEQA2, in order to give an indication of processes likely to occur in the water as well as the behaviour of certain possible pollutants in the vlei. Water and sediment core samples, collected during two separate sampling trips, were taken along the entire length of the vlei and some water samples were taken in the catchment. Interstitial waters were obtained by suction from sediment cores. Samples of secondary precipitates, found along the edge of the vlei, were also taken. The following laboratory analyses were performed on water samples: pH, EC, alkalinity, major cations and anions, dissolved P, fluoride, and the trace metals Fe, Mn, Al, Ni, Cu, Zn, and Pb. The following laboratory analyses were performed on sediment samples: pH of wet and dried sediments, organic C content, carbonate content, total elemental concentrations of major and trace elements, mineralogy, clay percentage and extractable P, Zn and K. Scanning electron microscopy and mineralogical analyses were performed on samples of secondary precipitates.en_ZA
dc.identifier.apacitationLanz, J. (1997). <i>A geochemical investigation of the waters and sediments of De Hoop Vlei, Bredasdorp district, South Africa</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Geological Sciences. Retrieved from http://hdl.handle.net/11427/20190en_ZA
dc.identifier.chicagocitationLanz, Johann. <i>"A geochemical investigation of the waters and sediments of De Hoop Vlei, Bredasdorp district, South Africa."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Geological Sciences, 1997. http://hdl.handle.net/11427/20190en_ZA
dc.identifier.citationLanz, J. 1997. A geochemical investigation of the waters and sediments of De Hoop Vlei, Bredasdorp district, South Africa. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Lanz, Johann AB - De Hoop Vlei is a saline coastal lake situated 53 kilometres north-east of Cape Agulhas in the Western Cape Province of South Africa. It is probably of estuarine origin but is now separated from the sea by mobile sand dunes and, therefore, has no surface outflow. Inflow to the vlei is from a catchment area of approximately 1200 km2 in which intensive grain farming is practised. The vlei is situated within the De. Hoop Nature Reserve and its ecological value, particularly as a breeding ground for water birds, has been recognised in its designation as an international RAMSAR conservation site. Agricultural practices in the catchment have been identified as a potential threat to the ecology of the vlei. The overall objective of this study was to provide a geochemical characterisation of De Hoop Vlei. It focused on identifying the geochemical factors and processes which control the water chemistry of the vlei and attempted to identify any influence of agricultural activities on water quality. This was achieved through a geochemical interpretation of the results obtained from analyses of water and sediment samples collected during the study. Use was also made of Department of Water Affairs and Forestry monitoring data in order to examine long term behaviour of the system, particularly with respect to the effect of evaporative concentration on water composition. Furthermore, chemical equilibrium was modelled, using the geochemical model MINTEQA2, in order to give an indication of processes likely to occur in the water as well as the behaviour of certain possible pollutants in the vlei. Water and sediment core samples, collected during two separate sampling trips, were taken along the entire length of the vlei and some water samples were taken in the catchment. Interstitial waters were obtained by suction from sediment cores. Samples of secondary precipitates, found along the edge of the vlei, were also taken. The following laboratory analyses were performed on water samples: pH, EC, alkalinity, major cations and anions, dissolved P, fluoride, and the trace metals Fe, Mn, Al, Ni, Cu, Zn, and Pb. The following laboratory analyses were performed on sediment samples: pH of wet and dried sediments, organic C content, carbonate content, total elemental concentrations of major and trace elements, mineralogy, clay percentage and extractable P, Zn and K. Scanning electron microscopy and mineralogical analyses were performed on samples of secondary precipitates. DA - 1997 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1997 T1 - A geochemical investigation of the waters and sediments of De Hoop Vlei, Bredasdorp district, South Africa TI - A geochemical investigation of the waters and sediments of De Hoop Vlei, Bredasdorp district, South Africa UR - http://hdl.handle.net/11427/20190 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/20190
dc.identifier.vancouvercitationLanz J. A geochemical investigation of the waters and sediments of De Hoop Vlei, Bredasdorp district, South Africa. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Geological Sciences, 1997 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/20190en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Geological Sciencesen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherEnvironmental Geochemistryen_ZA
dc.titleA geochemical investigation of the waters and sediments of De Hoop Vlei, Bredasdorp district, South Africaen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMScen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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