Please read the "Background" (p v) in the section 00front of this document Copyright 2002, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Bartie, C 2002, The life and career of the South African dramatric soprano Marita Napier, DPhil thesis, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-11142007-125718 / > / Thesis (DPhil (Microbiology))--University of Pretoria, 2007. / Microbiology and Plant Pathology / unrestricted

Ph.D. (Chemistry) / In this study, carbon based electrode materials such as glassy carbon, graphene, diamond and exfoliated graphite were explored as suitable electrode materials for electrochemical detection, electrochemical and photoelectrochemical degradation of organic water pollutants. Graphene modified glassy carbon electrode sensor was developed for bisphenol A. Cyclic voltammetry was used to study the electrochemical properties of the prepared graphene- modified glassy carbon electrode using potassium ferricyanide as a redox probe. The prepared graphene- modified glassy carbon electrode exhibited more facile electron kinetics and enhanced current of about 75% when compared to the unmodified glassy carbon electrode...

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Contaminants can exist in a wide range of states in aqueous environments, especially in surface waters. They can be freely dissolved or associated with dissolved or particulate organic matter depending on their chemical and physical characteristics. The freely dissolved fraction represents the most bioavailable fraction to an organism. These freely dissolved contaminants can cross biomembranes, potentially exerting toxic effects. Passive sampling devices (PSDs) have been developed to aid in sampling many of these contaminants by having the ability to distinguish between the freely dissolved and bound fraction of a contaminant. A new PSD, the Lipid-Free Tube (LFT) sampler was developed in response to some of the shortcomings of other current PSD that sample hydrophobic organic contaminants (HOCs). The device and laboratory methods were original modeled after a widely utilized PSD, the semipermeable membrane device (SPMD), and then improved upon. The effectiveness, efficiency, and sensitivity of not only the PSD itself, but also the laboratory methods were investigated. One requirement during LFT development was to ensure LFTs could be coupled with biological analyses without deleterious results. In an embryonic zebrafish developmental toxicity assay, embryos exposed to un-fortified LFT extracts did not show significant adverse biological response as compared to controls. Also, LFT technology lends itself to easy application in monitoring pesticides at remote sampling sites. LFTs were utilized during a series of training exchanges between Oregon State University and the Centre de Recherches en Ecotoxicologie pour le Sahel (CERES)/LOCUSTOX laboratory in Dakar, Senegal that sought to build "in country" analytical capacity. Application of LFTs as biological surrogates for predicting potential human health risk endpoints, such as those in a public health assessment was also investigated. LFT mass and accumulated contaminant masses were used directly, representing the amount of contaminants an organism would be exposed to through partitioning assuming steady state without metabolism. These exposure concentrations allow for calculating potential health risks in a human health risk model. LFT prove to be a robust tool not only for assessing bioavailable water concentrations of HOCs, but also potentially providing many insights into the toxicological significance of aquatic contaminants and mixtures. / Graduation date: 2010

Call number: LD2668 .T4 1984 K55 / Master of Science

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

A comprehensive literature survey looking at different aspects of organic contaminants in sewage sludge is incorporated in the thesis. It is clear from the data available that plants do not take up most of the organic pollutants. However, a risk of contamination of the food chain exists when sludge is spread directly onto crops that are to be consumed raw or semi-cooked. The major source of human exposure to sludge-borne organic pollutants is through the consumption of animal products such as meat and milk through the bioaccumulation of compounds such as polychlorinated dibenzo-p-dioxins and -furans (PCDD/Fs), polychlorinated biphenyls (PCBs) or polynuclear aromatic hydrocarbons (PAHs). This is due to the ingestion of soil and sludge by livestock due to the spreading of sludge on the land used for grazing. Currently little is known about the plant uptake of phthalates and nonylphenols, which are present in relatively high levels in sludge. Included in the literature survey is a list of the most common methods normally used for extraction of organic compounds and the possible methods of analysis. What is noted is that there is no universally accepted and validated analytical method for analysing most of the organic compounds. In addition, data concerning levels of organic pollutants is scarce worldwide. The methods selected for this project were EPA Methods 35IOC (Liquid-liquid extraction) and 3540C (Soxhlet extraction) for the aqueous and solid sewage sludge respectively. These two methods were chosen because they are simple, inexpensive and effective. The chosen purification method was the sulfur clean-up process (EPA Method 3660B). This is because sulfur precipitates were observed in most of the concentrated extracts, especially from the solid samples. A total of 109 samples from 78 sewage works were extracted, using Soxhlet extraction for solids and liquid-liquid extraction for liquid samples. All the extracts were analysed using GC-MS. The identification of the organic compounds was made possible by the use of GC-MS Wiley library. A total of 712 organic compounds were identified in the South African sewage sludge. These included Phenols, Pesticides, PAHs, Phthalates, PCBs, Furans, Amines, Aldehydes, Esters, Acids, Chlorinated Hydrocarbons, Alcohols, Hydrocarbons and Others (all sorts of organic compounds that did not belong to the named categories). The extraction efficiency and reproducibility using a "clean" sludge matrix was carried out. The results showed that the method chosen for extraction i.e. Soxhlet method had an efficiency of over 80% and the results were reproducible. A total of 14 samples were selected for the quantification of p-cresol, nonylphenol and pesticides listed in the current legislation. The results showed negative results for pesticides, confirming that the pesticides listed in the legislation are not the compounds that need to be regulated as far as organic pollutants are concerned. The reasons for this are most likely due to the fact that most of the pesticides listed are banned or their use is severely restricted. The results for the quantification of p-cresol and nonylphenol, when comparing the liquid and the solid extracts of the liquid sludge, show that 99% of p-cresol is concentrated in the liquid phase. The opposite is true when looking at nonylphenol where 90% of it is trapped in the solid matrix leaving 10% in the liquid phase. It is also noted that liquid sludge contains high concentrations of both p-cresol and nonylphenol when compared to the solid sludge. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.

Orientador: Luíz Vicente de Andrade Scalvi / Banca: Valmor Roberto Mastelaro / Banca: Joelma Perez / Banca: Fenelon Martinho Lima Pontes / Banca: Luiz Henrique Dall'Antonia / Resumo: Os semicondutores BiVO4 e NiO vem sendo bastante estudados nos últimos anos para aplicação em fotoeletrocálise, mais especificamente na degradação de poluentes orgânicos em meio aquoso, implicando em sustentabilidade ambiental. Neste trabalho, estes materiais foram obtidos na forma de filmes finos pelas técnicas: Síntese de Combustão em Solução e Co-precipatação, combinadas ao processo de deposição via molhamento (dip-coating). A composição, microestrutura e morfologia dos filmes foram avaliadas por TG-DTA, DTX e MEV. Os resultados de TG-DTA e DRX permitiram verificar a temperatura de formação das classes desejadas, 287ºC para o BiVO4 e 305ºC NiO. Imagens MEV mostram que os filmes são compostos por partículas de formato aproximadamente eférico, com boa dispersão sobre o suporte. Espectros UV-VIS mostraram que filmes de BiVO4 absorvem na região do visível com bandgap da ordem de 2,5 eV, e filmes de NiO absorvem no ultravioleta no ultravioleta com bandgap da ordem de 3,0 eV. A caracterização elétrica, trouxe resultados surpreendentes, particularmente no filme de NiO, onde iluminação com luz de energia acima do gap aumentou a resistividade do material, o que está ligado a variâncias de Ni2+. A caracterização eletroquímica, realizada por voltametria cíclica e cronoamperometria, mostrou que ambos os filmes respondem à excitação à excitação com luz de determinado comprimento de onda, além de apresentar estabilidade na corrente fotogerada. Ambos os filmes se mostraram eletroativos frente à reação de degradação do azul de metileno, sendo que na presença de luz ocorre a maior degradação. Um eletrodo com heterojunção p-n foi confeccionado utilizando estes dois materiais. O eletrodo FTO/p-NiO/n-BiVO4 apresentou excelente desempenho frente à degradação do azul de metileno, em... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The semiconductor BiVO4 and NiO have been extensively studied in recent years for the photoelectrocatalysis application, more specifically in the organics polluants degradation in aqueous solution, which leads to sustainability environment. In this work, these materials were obtained in the form of thin films by Solution Combustion Systhesis and co-precipitation techniques, combinee with the dip-coating deposition process. The composition, microstructure and morphology of these films was evaluated by TG-DTA, XRD and SEM. TG-DTA and XRD results were important to verify the temperature of the desired phase formation, which tuned out as 287ºC and 305ºC for the BiVO4 and NiO, respectively. SEM images show that the films consist of spherical particles with good dispersion on the support . UV-VIS Spectroscopy, have shown that BiVO4 thin film absorbs in the viable region with bandage energy of about 2.5 eV, whereas the NiO thin film absorbs in the ultraviolet region with bandagap energy about 3.0 eV. The electrical characterization has shown striking results, particularly on the NiO film, where irradiation with above bandgap light leads to a resistivity increase, which was related to the presence of Ni2+ vacancies. The electrochemical characterization, carried out by cyclic voltammetry and chronoamperometry, has shown that both the films respond to excitation with light of specific wavelength and provides stability in the photocurrent. Both the films are electroactive in the methylene blue dedradation reaction and that the greatest degradation takes place in the presence of light. A p-n heterojunction electrode was made using these two materials. The FTO/p-NiO/n-BiVO4, electrode showed excellent performance in the methylene blue degradation in different electrolytes under visible and UV light ilumination. The percentages of... (Complete abstract click electronic access below) / Doutor

Orientador: Eduardo Alves de Almeida / Banca: Gisela de Aragão Umbuzeiro / Banca: Lilian Castiglioni / Resumo: Ambientes naturais próximos a áreas urbanas e industrializadas são comumente contaminadas com descargas de poluentes, as quais são muitas vezes compostas por agentes químicos que não são removidos por sistemas de tratamento de efluentes convencionais, resultando num grande aporte de substâncias potencialmente tóxicas no ambiente aquático. Os metais são componentes naturais presentes nos ecossistemas. Estes elementos são indispensáveis para processos bioquímicos e fisiológicos nos seres vivos. No entanto, muitos desses elementos, quando em níveis elevados, podem ter efeitos adversos na saúde humana. Sabe-se que as enzimas esterases são fortemente inibidas por praguicidas organofosforados (OP) e carbamatos (CM), porém estudos recentes apontam o potencial efeito de alguns metais como compostos interferentes na atividade das esterases. Portanto, a avaliação da inibição de esterases em organismos aquáticos tem sido amplamente utilizada como um indicador de contaminação ambiental por esses compostos. O presente trabalho teve como objetivo o estudo da interferência dos metais cobre, chumbo, ferro e cádmio, na atividade da acetilcolinesterase (AChE) e carboxilesterase (CbE), em zebrafish. A AChE foi significantemente inibida in vitro pelo cobre, ferro, chumbo e cádmio nas maiores concentrações testadas (10 e 20 mmol/L), enquanto CbE foi inibida apenas na concentração de 20 mmol/L. In vivo somente o chumbo e o cádmio foram capazes de causar inibição na AChE nas maiores concentrações testadas, o ferro não causou nenhuma alteração e o cobre promoveu um aumento na atividade da AChE na concentração de 0,06 mg/L. A CbE não sofreu nenhuma alteração em nenhum dos tempos e concentrações testadas, exceto na exposição ao cobre, onde apresentou decréscimo em sua atividade. Além disso, de acordo com dados cinéticos obtidos, observa-se que todos os inibidores... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Natural environments close to urbanized and industrialized areas are commonly contaminated by discharges of pollutants, which are often composed by chemicals that aren't removed by conventional wastewater treatment systems. Metals are natural components in the ecosystems, being essential to biochemical and physiological process in living organisms. However, if these elements are in excess, they can impose adverse effects on living organisms. Esterases are strongly inhibited by organophosphate (OP) and carbamate (CM) pesticides, but recent studies pointed to the potential effect of some metals as interfering compounds on the esterases activity. The present work aimed to study the interference of the metals copper, lead, iron and cadmium in the activity of acetylcholinesterase (AChE) and carboxylesterase (CbE) in zebrafish. AChE was significantly inhibited in vitro by copper, iron, lead and cadmium at higher concentrations (10 and 20 mmol/L), whereas CbE was inhibited only at a concentration of 20 mmol/L. In vivo, only lead and cadmium were able to cause AChE inhibition at higher concentrations, iron didn't cause any changes and copper promoted an increase in the AChE activity at concentration of 0.06 mg/L. CbE activity did not change in any of the times and concentrations tested, except in the copper exposure, which showed a decrease in its activity. Furthermore, according to kinetic data obtained, it is noted that all inhibitors showed mixed inhibition type. Indeed, iodoacetamide treatment did not change AChE neither CbE activities, indicating that the metal inhibiting effect is probably not due to biding to thiol groups close the active site of the enzyme. These results indicate metals as important inhibitors of esterase in zebrafish, and should be considered in environmental monitoring studies that uses esterase inhibition as OP and CM exposure biomarkers / Mestre

Studying the interactions between bacteria and soil colloidal particles in the environment is important for bioaugmentation purposes. Different factors affect the transport of the bacteria in porous media. For example, the soil type, the ionic strength of the substrate, and biological properties, such as the bacterial cell motility. Since organic materials are present in almost all subsurface media, the presence of natural organic matter (NOM) is considered an important factor influencing bacterial transport in porous media. In this work, a model system was developed to examine the interactions between natural colloidal particles and environmental bacteria using Atomic Force Microscopy (AFM). The natural colloids in the environment were modeled by a surface film of adsorbed NOM onto spherical SiO2 particles. Poly(methacrylic acid) (PMA), a simple linear polyelectrolyte, was used to mimic NOM since both are dominated by carboxylic acid functional groups. Soil Humic Acid (SHA) and Suwannee River Humic Acid (SRHA), two acidic polyelectrolytes, were used in further experiments to represent more complicated NOM. A smooth strain of Pseudomonas aeruginosa (PAO1) that coexpresses A-band and B-band polysaccharides, and its rough mutant (AK1401) that only expresses the A-band polysaccharides, were chosen to represent environmental bacteria. The model system was characterized through analysis of the measured forces between the chemically-modified colloidal probes and the bacterial cells. Interestingly, we found that PMA was not a good model for the more complex NOM substances. Differences were also observed in how each bacterium interacted with the three forms of NOM. For example, P. aeruginosa PAO1 had the highest adhesion with both complex forms of NOM, while P. aeruginosa AK1401 had the lowest adhesion with the complex forms of NOM. Since the lipopolysaccharide (LPS) structure is the only difference between the two strains, we attribute the different interactions to differences in LPS structure. The polymer density on the bacterial surface was found to be the most important factor in controlling the nature of the interaction forces.