Browsing Faculty of Military Sciences by browse.metadata.advisor "Bezuidenhout, J."
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- ItemICP-MS analysis of trace metals in pacific oysters (Crassostrea gigas) within the port of Saldanha, South Africa(Stellenbosch : Stellenbosch University, 2022-12) Dhlalani, Nomcebo Marry; Bezuidenhout, J.; Stellenbosch University. Faculty of Military Sciences. School of Science and Technology. Dept. of Physics.ENGLISH ABSTRACT: The aim of the study was to monitor the accumulation of the trace metals, Manganese(Mn), Cadnium (Cd), Zinc (Zn), Copper (Cu) and Mercury (Hg) in oysters that were cultivated in Saldanha Bay over the period 2018 until 2020. Eight strategic positions were selected in Saldanha Bay for biomonitoring; three at the oyster growers lease areas in Small Bay, one at the oyster growers lease areas in Big Bay and four close to the Multi-purpose Terminal. At each monitoring station a cohort tower was deployed which contained the oysters used for biomonitoring. At most, ten of these oyster spat were selected and assessed for trace metal content to establish a baseline condition to measure trace metal accumulation. The oysters were analysed for trace metal content over long- and short-term intervals. Long-term monitoring entailed deploying the long-term oyster cohort for a total period of 24 months. After every three months of deployment, the oyster towers were retrieved and a sample of five oysters was selected from the long-term cohort, placed in a labelled plastic bag, and sent for analysis. The short-term monitoring, on the other hand, entailed deploying a fresh oyster cohort every three months over a period of 24 months. After three months of deployment, the oyster tower was retrieved and a fresh batch of oyster tower was replaced in the same sampling point for both long-term and short-term intervals. The samples of both long-term and short-term monitoring were sent to the ICP-MS laboratory, University of Stellenbosch, where tissue was extracted from the oysters, frozen and submitted for trace metal analysis using an Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). It was found that the average concentration of Mn ranges between 1.14 mg/kg and 1.80 mg/kg and Zn ranges between 55.45 mg/kg and 97.90 mg/kg. It was assumed that the anti-fouling products used in the Small Bay influenced the concentration of Cu, which gave high values ranging from 2.18 mg/kg up to 4.49 mg/kg. Concentration of Cd range from 0.75 mg/kg to 1.20 mg/kg and Hg was between 0.00 mg/kg and 0.01 mg/kg. When looking at short-term trends, generally after deployment, oysters recorded an increase in concentrations for the following metals, Mn, and Zn, while Hg, Cu, and Cd recorded a general decrease in concentrations over the same short-term deployments. Not all general trends were omnipresent as spatial and temporal specific variations were observed during the study. This suggested that in some cases trace metal supply intake coupled with seasonal variation could influence the amount of trace metal present in the oyster at any time. The average trace metal concentrations in oysters presented were in a decreasing trend of Zn > Cu > Mn> Cd > Hg. The oyster proved to be good biomonitors due to its ability to accumulate trace metals over time. There were however, oyster mortalities over the period of the study, but these mortalities were related to parasitic infections.
- ItemThe influence of geographic factors on the distribution of natural radionuclides(Stellenbosch : Stellenbosch University, 2017-12) Geyser, Alwyn Petrus; Bezuidenhout, J.; Smit, H.A.P.; Stellenbosch University. Faculty of Military Science. Dept. of Military Geography. School for Geospatial Studies and Information Systems.ENGLISH SUMMARY: The primordial radionuclides 40K, 232Th, and 238U have been present in almost all rocks, soils, and minerals since the formation of Earth. These radionuclides emit gamma radiation that is detectable by means of a scintillation detector. By measuring the concentrations of 40K, 232Th, and 238U in an area it is possible to draw radioelement maps. These radioelement maps were then used in a qualitative analysis to establish the influence of local geographic factors on the distribution of natural radionuclides. The research site is a granite outcrop, Baviaansberg, and the immediate area surrounding the outcrop. Baviaansberg is situated in the Saldanha Bay Military Area on the West Coast of South Africa. The available literature on the impact of geographic factors on the distribution of natural radionuclides are limited. Scientific radioelement mapping in military areas in South Africa has only been completed by Bezuidenhout (2012). The research provided the opportunity to study the feasibility of establishing a link between natural radionuclide concentrations and geographic factors within a military area. Hence, the aim of the research was to investigate the relationship between geographic factors and the distribution of natural radionuclides of a particular area. Radioelement maps were used to analyse the impact of the respective geographic factors “geology”, “topography”, “soil type”, “hydrology”, “wind” and “human activity” on the distribution of the concentrations of natural radionuclides. Radiation measurements of the natural radionuclides in the research site were completed by means of in situ measurements using a NaI(Tl) scintillation detector connected to a tablet computer. Once the natural radionuclide concentrations were extracted by means of Full Spectrum Analysis (FSA), radioelement maps were created from the results. Qualitative analysis was performed on the radioelement maps by means of comparing it to the slope raster, slope profiles, a flow accumulation raster, wind data, Google Earth images, a human activities map, a soil type map, Spline vs Kriging raster, Th vs K raster, U vs K raster, and a U vs Th raster. The qualitative analysis aimed to establish the influence of the identified geographic factors on the spread of natural radionuclide concentrations. The results indicated that the geology of an area influences the distribution of natural radionuclides. The highest concentrations of natural radionuclides were found close to the granite outcrops on Baviaansberg. Slope was used to determine the influence of topography. The results revealed that slope influences 40K concentrations to a greater extent than 232Th and 238U concentrations due to the solubility of 40K. The different soil types within Baviaansberg also displayed unique associated natural radionuclide concentrations. According to the research results, the hydrology of Baviaansberg impacted on the spread of 40K, 232Th and 238U concentrations. However, 40K was influenced to a greater extent because of its solubility. The impact of the dry summer winds on the distribution of natural radionuclides became apparent through a comparison of the leeward and windward slopes of Baviaansberg. On the leeward slope higher concentrations of natural radionuclides were recorded than on the windward slope due to small particles that are removed from the windward slope and deposited on the leeward slope. Research results concerning the influence of human activities on the distribution of natural radiation were inconclusive. Further research needs to be conducted in order to confirm a definite relationship, should it in fact exist. True to the aim of the research, the study established that it is feasible to validate the influence of geographic factors on the distribution of natural radionuclides by analysing the natural radionuclide concentrations of an area.