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A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in fulfilment of the requirements for the degree of Master of Science in, Microbiology and Biotechnology 2016. / Heavy metal contamination, of natural water resources, resulting from the large amounts of toxic waste generated by industrial practices is of great environmental concern. Lead (Pb) in particular is one of the most toxic heavy metals that leads to several health deficiencies upon human exposure. The reduction of heavy metals like Pb to acceptable levels in the water therefore becomes critical for potable and agricultural use. Removal of heavy metals by conventional methods is expensive and results in secondary pollution. Bioremediation, a process that passively removes heavy metals from solution through microbial biosorption, is a much sought after alternative because it is more eco-friendly and cost-effective. Micrococcus luteus and Paenibacillus castaneae are two bacterial species reported to be highly resistant to Pb making them favourable as metal biosorbents. The present study aimed to further characterise these species as biosorbents by evaluating the influence of environmental conditions on their rate of biosorption of Pb. Each bacterial isolate was heat-killed and exposed to 0.5 mM (150 mg/L) Pb and the maximal rate of metal uptake calculated when the pH, temperature and biomass concentration were varied. Additionally, the initial metal concentration was increased from 0.005 to 1.25 mM to determine its effect on Pb uptake by each species. The influence of competing cations (Ni2+, Co2+, Mn2+ and Zn2+) on the rate of Pb uptake by each isolate was also established. Both bacterial isolates resulted in the biosorption of at least 50% of 0.5 mM Pb ions when used at a pH of 7, temperature of 25 oC, and a biomass concentration of 2 g/L. The rate of metal uptake for M. luteus at the above mentioned parameters was found to be 24.51 mg/g biomass, while the rate of metal uptake for P. castaneae was 15.63 mg/g biomass. These findings indicated that M. luteus took up more Pb at a faster rate in comparison to P. castaneae. The present study furthermore elucidated that as the metal concentration of Pb was increased, the amount of Pb biosorbed by M. luteus decreased from 84.76% to 46.10%. Similarly, P. castaneae yielded 81.39% biosorption from 0.005 mM Pb but only 34.29% of Pb was taken up when the concentration was increased to 1.25 mM. When the bacteria were exposed to various competing cations an increase in the rate of Pb biosorption was observed for P. castaneae while the opposite effect was noted for M. luteus. Findings from this study show that under high metal concentrations, both M. luteus and P. castaneae are capable of significantly reducing the level of Pb from pure solution. The results warrant further treatment of several industrial effluents using these biosorbents for subsequent application in wastewater treatment. / MT2017

ABSTRACT Childhood lead exposure is increasingly becoming a public health concern in developing and developed countries. Children are particularly vulnerable because of their developing body systems and mouthing behaviours. Recent studies have shown that lead exposure during pregnancy could cause harmful effects in unborn babies, subsequently causing ill health during later childhood. Lead poisoning prevention strategies should address exposures before, during and after pregnancy. To develop an appropriate framework for childhood lead exposure preventive strategies, the knowledge, perceptions, and behaviours of pregnant women in relation to child lead hazards had to be explored. The purpose of this study was to investigate the knowledge, perceptions and behaviours of pregnant women in relation to child lead hazards. To answer the research question, objectives were formulated which were to explore the knowledge of pregnant women regarding the sources and routes of exposure, the health effects of lead and mechanisms to protect children against lead exposure. The study objectives were achieved by administering an exploratory structured questionnaire. A non-probability convenience sample of 119 pregnant women was selected for data collection. Data was analysed using STATA 9.0 software. The results showed that only 13 participants (11%) had heard of lead before and the majority of participants (89%, n=107) had not heard of lead before. Four participants (31%, n=13) did not know if lead could be harmful to the health of children. Nine participants (69%, n=13) however, thought that lead could harm the health of children. Six participants (46%, n=13) did not know the health and social problems that lead exposures could cause in children. High risk factors in the living environment of the study population included informal housing, overcrowded living conditions, flaking and peeling paint, poor hand wash behaviour and smoking. The study concluded that there were low levels of knowledge, lacking perceptions and high-risk behaviours and practices amongst pregnant women in relation to child lead hazards. It further concluded that there were high-risk activities and conditions in the living environment of the studied population.

Introduction Lead exposure continues to be a major public health issue in South Africa, and other low and middle income countries. Environmental lead exposure has been associated with detrimental health effects in children. The aim of this thesis was to assess the prevalence of lead exposure and its association with various risk factors, its effects on puberty and socio-behavioural adjustment in adolescents. Methods The Birth to Twenty (Bt20) cohort study started in 1990, and is a long-term prospective follow-up study of children’s health and well-being. Mothers were recruited from antenatal clinics in the Johannesburg-Soweto metropolitan area between April and June 1990 (n=3273). Lead levels were analysed in samples of cord blood collected at birth (n=618) and whole venous blood collected at 13 years of age (n=1546). Data on selected child, maternal and household factors were collected using a structured questionnaire in the third trimester of pregnancy and at 13 years of age. Additional data on puberty (attainment of menarche and self-reported Tanner staging for breast and pubic development) and behaviour using the Youth Self Report was obtained at 13 years of age. Results In the Bt20 cohort the mean blood lead level at birth was 5.9 μg/dl, and at 13 years of age it was 5.7 μg/dl. The majority of children had blood lead levels above 5.0 μg/dl (52% at birth and 56% at 13 years). At birth, being a teenage mother and having low educational status were strong predictors for elevated cord blood lead levels. Being a male child, having an elevated cord blood level, and lack of household ownership of a phone were significant risk factors for high blood lead levels at 13 years. In 13 year old females with pubertal data (n= 682) the mean blood lead level was 4.9 μg/dl. Fifty percent had blood lead levels < 5.0 μg/dl, 49 % were ≥5.0 μg/dl and 1% was > 10.0 μg/dl. The average age of menarche was 12.7 years. At 13 years, 4% and 7% had reached Tanner stage 5 for pubic hair and breast development, respectively. Analyses showed that higher blood lead levels were significantly associated with delays in all measures of puberty (p <0.001). In the 13 year old sample with data on the Youth Self Report (n= 1041), the geometric mean blood lead level was significantly (P value<0.001) higher in boys (6.0 μg/dl) compared to girls (4.5 μg/dl). The bivariate analyses stratified by gender showed that boys’ blood lead levels were significantly associated with four types of aggressive behaviour. There were no significant associations found in girls. A multivariate analysis was conducted in the sample of boys and after adjusting for socio-economic factors ”Attacking People” remained significantly associated with blood lead levels. Conclusion Significant associations found in the study point to the low socio-economic status of lead exposed children. These poor circumstances frequently persist into adolescence resulting in continued high lead levels. Higher blood lead levels were associated with a delay in the onset of puberty in girls, and with anti-social behaviour among boys in early adolescence. Lead exposure in low and middle countries is generally higher compared to high income countries, and thus the effects of high blood levels are much greater and have larger personal and public health significance.

Lead (Pb²⁺) is an environmental toxin that is known to cause lasting cognitive deficits following early life exposure. Previously, our laboratory demonstrated increased sensitivity to the psychostimulant effects of cocaine in animals with elevated blood Pb²⁺ levels (BLL). This effect was abolished following introduction of dopamine (DA) receptor antagonists, indicating that the dopaminergic (DAergic) system may be a target of Pb²⁺’s toxic effects. However, the biological mechanisms through which Pb²⁺ increased sensitization to cocaine’s psychostimulant effects have not been fully elucidated. There is some disagreement regarding the magnitude and direction of Pb²⁺’s effects on the DAergic system. Furthermore, many studies to date have measured the effects of Pb²⁺ in only one sex (usually male), one exposure, and one or two time-points, making it difficult to determine any potential sex-, age-, and exposure-dependent effects. In the present study, we used a well-validated animal model and Pb²⁺ exposure paradigm that uses chronic dietary exposure to 180ppm and 1500ppm Pb²⁺ acetate (PbAC) in the diet. These levels of Pb²+ in the diet resulted in low and moderate levels of BLLs that on average approximated 4.5 and 22.0µg/dl in young adult rats. These levels of Pb²⁺ exposure are relevant to contemporary levels of BLL in intoxicated children in many cities in the United States and in many parts of the world where Pb²⁺ exposure continues to be a major public health concern. It should be noted that at the low level of Pb²⁺ exposure, the resulting BLL of 4.5µg/dl is just below the current CDC level of action. Using this well-defined rat model of chronic Pb²⁺ exposure, in Aim 1, we measured DA concentration and turnover in the dorsal striatum (STR) of juvenile (PN14), adolescent (PN28), and young adult (PN50) male and female rats. Tyrosine hydroxylase (TH) protein, the rate-limiting step in the synthesis of DA, and phosphorylation of TH at serine 40 (pser40TH) were assessed as an indirect measure of TH activity. Thus, we measured the ratio of pser40TH to total TH protein. We also measured vesicular monoamine transporter-type 2 (VMAT2) levels in the STR, nucleus accumbens (NAC), and olfactory tubercle (OT) since this protein is critical for the sequestration of DA in presynaptic vesicles and has been used as a biomarker for DA terminal integrity. In Aim 2, we examine the effect of chronic Pb²⁺ exposure on D1 and D2 dopamine receptor (D1R and D2R) in the OT, NAC, and STR. Analysis of D1R and D2R is important since the downstream effects of DA are dependent on the DA receptor subtype it activates. In Aim 1, we observed significant increases in DA and its metabolites homovanillic acid (HVA) and 3,4-Dihydroxyphenylacetic acid (DOPAC) in the STR of adolescent and young adult male rats with BLL as low as 4.5µg/dl in the absence of phosphorylation at the serine 40 residue of TH or altered VMAT2 levels. In Aim 2, a significant increase in D2R was detected in the juvenile male rat STR. We also observed increases in D1R expression in adolescent male rats in the NAC, OT, STR, and in the OT of adolescent female rats. Together, these results demonstrate that chronic Pb²⁺ exposure alters DA receptor levels in a manner characteristic of a hyperactive DAergic state. The observations presented in this work suggest that a hyperactive DAergic system underlies the heightened sensitization to cocaine we previously observed in Pb²⁺-exposed animals. This work builds upon the current understanding of how Pb²⁺ modulates the DAergic system and provides some elucidation of the mechanisms underlying increased drug sensitization our laboratory has previously observed in rats exposed to Pb²⁺.

Resumo: O método de Pechini bem como o uso da adição simultânea de partículas sementes (BaTiO3 ou PbTiO3) e de solução dopante contendo íons Ba2+ e Ti4+ ou Pb2+ e Ti4+ foram usados para preparar o niobato de zinco e chumbo (PZN). Com a finalidade de se estudar a influência do tamanho das partículas sementes na obtenção da fase PZN perovskita estável e na microestrutura da cerâmica, trabalhou-se com dois intervalos de tamanhos das partículas sementes: 1- entre 40 nm < φ < 100 nm, denominadas sementes de menor tamanho (frequência de 1015 partículas por cm3); 2- entre 100 nm< φ < 900 nm, denominadas sementes de maior tamanho (frequência de 1013 partículas por cm3). Os difratogramas de raios X obtidos para as amostras calcinadas a 800 oC ou a 900 oC permitiram identificar a formação das fases perovskita e pirocloro, sendo que a 900 oC predomina a fase perovskita. As amostras preparadas com as sementes de maior tamanho, menor frequência de núcleos cristalinos, apresentaram maior porcentagem de fase pirocloro que as preparadas com as sementes de menor tamanho após a calcinação. Os pós foram compactados isostaticamente e sinterizados entre 950 a 1100 oC. Para a sinterização utilizou-se um sistema fechado contendo atmosfera de pó de PbZnO3 + 5% PbO para controlar a evaporação do chumbo estequiométrico, durante a sinterização. A forma na qual os aditivos foram adicionados ao polímero (se como íons ou como sementes), assim como a frequência de núcleos cristalinos influeciaram no processo de sinterização e na microestrutura desenvolvida. As amostras preparadas com as sementes de maior tamanho exigiram uma temperatura mais elevada para a sinterização e apresentaram uma microestrutura mais heterogênea que as amostras preparadas com as sementes de menor tamanho. A microestrutura dos compactos obtidos a partir de pós contendo 50% dos aditivos na forma...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Pechini method as well as the simultaneous addition of seeds particles (BaTiO3 or PbTiO3) and dopant solutions containing Ba2+ and Ti4+ or Pb2+ and Ti4+ were used to prepare the perovskite phase of lead zinc niobate (PZN). To study the influence of seed particle size in the formation of stable PZN phase and in the ceramic microstructure, two range of seed particle size were considered: a) in the range of 30 to 100 nm, named small seed particles (frequency of 1015 particles/cm3); and b) in the range of 50 to 900 nm, named large seed particles (frequency of 1013 particles/cm3). The perovskite and pyroclore phases were identified for powder calcined at 800 oC and at 900 oC with predominance of perovskite phase for powder calcined at 900 oC. Powders prepared with large seed particles, smaller crystalline nuclei frequency, showed large amount of pyroclore phase after calcining, compared with the powder prepared with small size seeds. Calcined powders were isostaticaly pressed and sintered at temperatures ranging from 900 to 1100 oC. A close system containing powder with PbZnO3 + 5 PbO, to control the lead evaporation from the compacted samples, was used during sintering. Both, the way in which the additives were added to the polymer (seeds or ions) as well as the crystalline nuclei frequency influenced in the sintering process and in the microstructure. Samples prepared with large seeds need higher temperatures for sintering and showed a more heterogeneous microstructure compared with samples prepared with small seed particles. The microstructure of ceramics prepared for powder containing 50% of additives as seed and 50% of additives as ions is more homogeneous. The microstructure of ceramics obtained from powders containing 80% of additives as seeds and 20% as ions showed grains with well-defined crystalline planes. All the sintered samples showed a second phase segregated to the grain boundary...(Complete abstract click electronic access below) / Coorientador: José Arana Varela / Orientador: Maria Aparecida Zaghete Bertochi / Mestre

Tese de mestrado. Inovação e Empreendedorismo Tecnológico. Faculdade de Engenharia. Universidade do Porto. 2010

Thesis (M.Sc.)--York University, 2004. Graduate Programme in Geography. / Typescript. Includes bibliographical references (leaves 98-103). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL:http://gateway.proquest.com/openurl?url%5Fver=Z39.88-2004&res%5Fdat=xri:pqdiss&rft%5Fval%5Ffmt=info:ofi/fmt:kev:mtx:dissertation&rft%5Fdat=xri:pqdiss:MQ99353