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Magister Scientiae (Biodiversity and Conservation Biology) / Heavy metal contamination tends to be a problem in inner city agricultural areas and gardens. High levels of certain heavy metals have been found in the soil and vegetables in the Cape Town Metropolitan area. The aim of this project was twofold. Firstly to ascertain whether water (ground or surface) was responsible for the heavy metal problem found in vegetables in the Philippi and Kraaifontein-Joostenbergvlakte farming areas in Cape Town; and secondly to evaluate the efficacy of two possible remediation methods, namely chelation (with EDTA) and precipitation (using phosphate), aimed at tackling the problem. In order to achieve this a water survey and greenhouse experiment were conducted. The water survey involved collecting a number of samples; both from surface dams and boreholes, from the two farming areas. Results showed minimal heavy metals in both, and therefore ruled this out as the source of the heavy metal problem. The greenhouse sand culture experiment tested the effects of the two remediation methods on the growth, development and elemental content of turnip and spinach plants treated with two cadmium and lead concentrations. In summary, Cd reduced growth more than Pb; Cd accumulated in roots and leaves, and Pb in roots. Several treatments, both metal and mitigation enhanced the chlorophyll content. The difference between the EDTA and phosphate mitigation treatments were not significant in the case of cadmium but in the case of lead, high phosphate resulted in increased growth. The large variation of results in this study, and indeed those of the available literature, indicate that the remedial treatments investigated here are not necessarily the most effective and that other treatments should be investigated to control the uptake of either cadmium or lead, as agricultural soils in future become more contaminated with either or both of these heavy metals.

Magister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv and Cons Biol) / Heavy metals and nutrients have long been regarded as pollutants to freshwater ecosystems. These elements have a detrimental effect on plants, animals and the water quality of rivers in South Africa. The Berg River flows from the mountains of Franschhoek to the West Coast of the Western Cape. It is an important river in Cape Town, as it is essential for water distribution to town, for agriculture and industry and also supports a rich diversity of organisms in the ecosystem. Along the river, many farms and towns are situated and many tributaries enter the river. The Berg River dam provides for a water supply during the drier periods of the year. Therefore it is crucial to maintain a good water quality. The study was driven by the need to increase the knowledge of water quality in the upper Berg River after the construction of a new major Berg River dam, constructed in 2007. This study investigated oxygen, water temperature, electrical conductivity, pH, ammonium, nitrate, nitrite in the water and cadmium, copper, lead, iron, zinc, potassium, sodium, calcium, magnesium and phosphorus found in water, sediment and three plant species at ten sites along the upper Berg River, Western Cape. The results showed that the electrical conductivity, pH and the concentrations of nitrate, calcium and magnesium increased downstream, whereas the water temperature decreased downstream. Nitrate, cadmium, copper, potassium, sodium, calcium and magnesium displayed a general increase towards the colder period in the water. Seasonally, copper and magnesium showed significant winter increase within the sediment. Nitrogen, iron and calcium levels within Salix sp., Acacia mearnsii and Brabejum stellatifolium increased downstream. Nitrogen, cadmium, copper, potassium, calcium, magnesium and phosphorus in the three species were higher in the warmer seasons and decreased in the colder. Sources of pollution stem from the Franschhoek and Dwars tributaries, urban and farm runoff.

The removal of lead from aqueous solution and lead-acid battery manufacturing waste-water by the non-viable biomass of the water fern Azolla filiculoides was investigated in both batch and column reactors. The maximum lead uptake by the Azolla biomass at a pH value of approximately 5, was found to be 100 mg lead/g biomass from aqueous solution. Lead removal varied from 30% of the initial lead concentration at pH 1.5 to approximately 95% at pH values of 3.5 and 5.6. Lead removal from aqueous solution decreased to 30% of the initial lead concentration if the lead concentration was initially over 400 mg/l. At initial lead concentrations of less than 400 mg/l, percentage lead removal was found to be over 90% of the initial lead concentration. Lead removal remained at approximately 90% between 10°C and 50°C. Biomass concentration (4-8 mg/l) had little effect on lead removal. The presence of iron (Fe) and lead, copper (Cu) and lead or all three metal ions in solution at varying ratios to each other did not appear to have any significant effect on lead removal. Percentage lead, copper and iron removal from aqueous solution was 80-95, 45-50 and 65-75% respectively for the different multiple-metal solutions studied. No break-through points were observed for lead removal from aqueous solutions in column reactors, with initial lead concentrations of less than 100 mg/l at varying flow rates of 2, 5 and 10 ml/min. This suggested that flow rate, and therefore retention time, had little effect on percentage lead removal from aqueous solution, which was more that 95%, at low initial lead concentrations (less than 100 mg/l). At initial lead concentrations of 200 mg/l or more, an increase in flow rate, which equates to a decrease in column retention time, resulted in break-through points occurring earlier in the column run. Percentage lead removal values, from lead-acid battery efiluent in column systems, of over 95% were achieved. Desorption of approximately 30% and 40% of bound lead was achieved, with 0.5 M HNO₃ in a volume of 50 ml, from two lead-acid battery. Repeated adsorption and desorption of lead by the Azalia biomass over 10 cycles did not result in any decrease in the percentage lead removal from effluent, which strongly suggested that the Azalla biomass could be re-used a number of times without deterioration in its physical integrity, or lead removal capacity. No evidence of deterioration in the Azolla biomass's physical integrity after 10 successive adsorption and desorption procedures was observed using scanning electron microscopy. The Azolla filiculoides biomass was, therefore, found to be able to effectively remove lead from aqueous solution and lead-acid battery effluent repeatedly, with no observed reduction in it's uptake capacity or physical integrity.

Accumulation and toxicity of cadmium, lead and thallium in duckweed (Lemna minor L.) The toxicity and accumulation of lead, cadmium and thallium in the aquatic plant Lemna minor was investigated, using a modification of the Organisation for Economic Co-operation and Development (OECD) standard growth inhibition test. Plants were cultured in modified Swedish Institute Standard (SIS) at pH 6.5±0.5 under 85 µmol m-2 S-1 at 25°C and exposed to a wide range of lead, cadmium, and thallium concentrations from environmentally realistic to very high concentrations (0.001, 0.01,0.1, 1, 10, 100, 1000 and 10 000 µmol L-1) for seven days. Various physico-biochemical endpoints were measured after seven days of exposure. The concentrations of dissolved lead, cadmium, and thallium remaining in the residual solutions, and accumulation of lead, cadmium and thallium in fronds and roots were assessed using Inductively Couple Plasma – Mass Spectroscopy (ICP-MS). Over the exposure duration, lead, cadmium, and thallium concentrations in solution decreased rapidly and chlorosis was observed in fronds exposed to the three highest lead, cadmium, and thallium concentrations. After seven days of exposure, there were significant decreases in the relative growth rate (RGR), relative frond area (RFA), pigment content (chlorophyll a, b and total carotenoid) and activity of photosystem II (Fv/Fm) at concentrations of 0.1, 1, 10, 100, 1000 and 10 000 µmol L-1Pb, 10, 100, 1000 and 10 000 µmol L-1cd, 0.01,0.1, 1, 10, 100, 1000 and 10 000 µmol L-1TI. However, our results suggested that root elongation based on relative growth rate of L. minor will be an optimal and relevant endpoint in compare to other endpoints. As expected, results demonstrated that root elongation was concluded that root length was most predictive of a dose response model compared to the rest of growth endpoints and physiological and biochemical endpoints when assessing toxicity of lead, cadmium and thallium using L. minor. Toxicity testing for the floating macrophytes should include root elongation measurement which alone will be sufficient to meet sensitivity and variability requirements for toxicity testing. Cellular concentrations of lead, cadmium, and thallium were higher in roots than fronds, whereas more lead, cadmium, and thallium was adsorbed to the extracellular matrix of fronds than roots. The bio - concentration factor (BCF; i.e. lead concentration in plant tissue at day seven relative to residual lead concentration in the growth medium at day seven) indicates that L. minor is a good accumulator of lead, cadmium, and thallium particularly at lower concentration, but the physiological data shows that these metals toxic at concentrations that can be encountered in wastewater treatment facilities. The translocation factor (TF) value was found to be less than 1. Though, lead, cadmium and Thallium was mostly stored in roots, only minor amounts of lead, cadmium and thallium were trans located to fronds.

This thesis explains a method based on the homogenisation of zeta potential charges on carbon supports for the production of hierarchical structured zeolitic composites. The modification of carbons’ surface chemistry allowed zeolite particles to be fixed to the support by electrostatic interactions. In order to achieve this, the size reduction of zeolite particles was carried out by two different methods: a) ball milling and b) a synthetic route to produce zeolite colloidal dispersions. Also, the seeding method, based on hydrothermal growth was compared. The prepared materials in this work were designed to be used in the sorption of cations, and to allow vitrification and thereby reduce the final adsorbent volume. Results showed that a large pollutant amount can be trapped using a lower volume of material reducing costs and final waste disposal. The zeolites used in this work were selected based on their low density framework and low Si/Al ratio. Synthetic zeolites A, Y and clinoptilolite were successfully produced. Natural clinoptilolite was also utilised in this work. Also, zeolite A was produced at nanometre scale following the clear solutions method. All materials were successfully incorporated onto supports to produce multimodal porosity materials. The hierarchical modification of natural clinoptilolite, following a straightforward and nonexpensive methodology, is one the most significant contributions of this work. Carbons are used as supports due to their high surface area, they can be obtained from low-cost sources such as agroindustrial wastes and carbons allow volume reduction if materials are vitrified at high temperatures. In this work, carbons were produced from corn cob and husk, sugar cane bagasse, cherry stones, date stones and hazelnut shells. The prepared composite materials were tested in the removal of toxic ions from water solutions: cobalt, copper and caesium ions were effectively removed from aqueous media. Adsorption experiments showed that the distribution of supported zeolite particles improved their uptake efficiency and capacity. The kinetic studies revealed an enhanced rate constant for carbon-zeolites composites in comparison with pure zeolites. Diffusivity results suggested that mass transfer characteristics are modified by using hierarchical porous materials; results showed that particle size or support nature can modify diffusion resistances, reducing intraparticle diffusion and accelerating the overall kinetic processes. Adsorption equilibrium data was correlated using Langmuir and Freundlich models.

M.Sc. (Zoology) / Tilapia sparrmanii (Smith) was exposed to sub-lethal doses of chromium, manganese, zinc and iron for 96 hours at an acidic pH (5), a physiological pH (7,4) and an alkaline pH (9), as well as a prolonged exposure (2 - 4 weeks) at an uncontrolled pH. In the laboratory fish were kept in aquaria which were supplied with continuously flowing borehole water. Controlled laboratory conditions existed during experimentation. Blood and liver samples of the experimental fish were sampled after exposure. The bioconcentration and the effect of the selected metals at the mentioned conditions, were thereby determined on bloodcoagulation, total and differential leucocyte counts, and liver enzYmes to investigate the possible damage to the liver. As metals have the ability to enter and concentrate in the body, the bioconcentration of each metal was determined by atomic absorption sPectrophotometry in the blood and liver. Chromium showed an increase in concentration in both the blood and liver, with an increase in pH after short term (96h) exposure. The statistical significant increases of manganese concentration in the blood over a short term were not reflected in the liver. It may be indicative of homeostatic control. A similar phenomenon was found with .zd.nc , The concentration of zinc in the liver did not reflect the progressive decrease in the blood wi th a increase in pH. Iron revealed a statistical significant increase in bioconcentration in the liver with, an increase in pH, which is indicative of the activity of the liver. The long term exposure of fish to chromium and manganese caused a significant increase in the concentration of the metals in the blood and liver. The only significant increase in concentration after exposure to iron, occured . in the Iiver. Exposure to zinc however caused a statistical significant decrease in concentration in both the blood and liver. Differential leucocyte counts reflected lymphocytosis, eosinophilia, monocytopenia and neutropenia, after short term exposure. These conditions nearly always resulted in leucopenia. Long term exposure to manganese and zinc reflected both eosinophilia and neutropenia. Chromium reflected eosinophilia, and iron, neutropenia. The only statistically significant change in the number of leucocytes after long term exposure, was caused by zinc and resulted in leucopenia. According to the photokymographic observation of blood coagulation by the thrombelastograph, exposure to the selected heavy metals lead to a prolonged clotting time and thrombocytopenia. Long term exposure (4 weeks) to manganese caused another bleeding disease, called hemophilia. It was thus evident that the exposure to heavy metals led to clotting defects, which caused bleeding.

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Heavy metals in wastewater can cause serious environmental problems and could beharmful to the human body. Therefore, heavy metals need to be removed from thewastewater. Coagulation based methods are popularly used nowadays with provedeffects. New methods such as the application of nanomaterials have brought morepossibilities to increase the removal effects for certain heavy metals. Among thesenanomaterials, graphene oxide has gained a lot of interest because of its large surfacearea and unique structure. Moreover, graphene oxide is an environmentally friendlymaterial. However, most of the reported studies did not use real wastewater samplesbut simulated ones prepared in labs. Therefore, the removal effects need to beexperimentally evidenced by using real wastewater samples. In this project, I studiedthe removal effects of pristine and modified graphene oxide using wastewatercollected at the wastewater treatment plant in Sundsvall (Fillan wastewater treatmentplant). Moreover, I have also studied the heavy metal removal effects of combinedcoagulation method and graphene oxide. Results have shown that graphene oxide hassimilar removal effects to the coagulation method, indicating the enormous potentialof graphene oxide in wastewater treatment. / <p>2021-09-19</p>

The topic of this master’s thesis is design of detector for electrochemical detection of heavy metals. Design meets the technical, aesthetic and ergonomic requirements and is developed in collaboration with other members of the research team involved in the grant project TACR named DETEKO TH01030389.