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Made available in DSpace on 2014-10-09T12:54:40Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:21Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:54:40Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:21Z (GMT). No. of bitstreams: 0 / A ocorrência de produtos farmacêuticos no ambiente aquático pode causar efeitos adversos à saúde humana e às comunidades aquáticas. Propranolol, -bloqueador não seletivo, é largamente prescrito no tratamento de doenças ligadas ao coração como angina e hipertensão. Simples medidas de efeito, como a CL50, não fornece informações sobre o impacto de contaminantes em populações. A taxa de crescimento populacional (r) é uma ferramenta importante para estudos que objetiva determinar os efeitos em nível populacional. Este trabalho foi desenvolvido com o objetivo de estabelecer a toxicidade aguda e crônica de Propranolol para a espécie autóctone Ceriodaphnia silvestrii (CLADOCERA, CRUSTACEA) com ênfase em efeitos nas populações. Os valores determinados para CE(I)50;48H foram de 2,87 e 2,63 mg.L-1 para água destilada e natural reconstituídas, respectivamente. Para a toxicidade crônica, os valores obtidos para CENO e CEO encontraram-se na faixa de 0,62-1,25 e 1,25-2,50 mg.L-1 para água natural reconstituída. Como critérios de aceitabilidade para os ensaios crônicos populacionais foram estabelecidos para o controle 73 neonatas (±10 DP) e taxa intrínseca de aumento natural de 0,596 (±0,13 DP) em sete dias de experimento com água natural reconstituída. No teste de sensibilidade, os valores obtidos para CENO e CEO populacional foram 0,275 e 0,723 g.L-1 de NaCl, respectivamente, semelhante aos valores nos ensaios crônicos individuais. Para Propranolol, as análises indicaram que os ensaios populacionais foram iguais ou mais sensíveis que a exposição individual. Os resultados nos ensaios crônicos populacionais e com indivíduos encontraram-se entre 1,25 (CENO) e 2,50 mg.L-1 (CEO), respectivamente. Os endpoints populacionais parecem ser medidas mais sensíveis. Comparando-se os valores de ICP para populações e indivíduos, observa-se que as populações foram mais sensíveis na ordem de 70%. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN/CNEN-SP

Recent advances in high-resolution analytical methods have brought about a paradigm shift in our understanding of how crystalline materials are formed. The scientific community now recognizes that many earth materials form by multiple pathways that involve metastable intermediates. Biogenic calcium carbonate minerals are now recognized to develop by aggregating molecules or clusters to form amorphous phases that later transform to one or more crystalline polymorphs. Amorphous calcium carbonate (ACC) is now recognized as a precursor to CaCO₃ biominerals in a wide variety of natural environments. Recent studies suggest an ACC pathway may imprint a different set of dependencies from those established for classical growth processes. Previous ACC studies provided important insights, but a quantitative understanding of controls on ACC composition when formed at near-physiological conditions is not established. The Mg content of ACC and calcite is of particular interest as a minor element that is frequently found in final crystalline products in calcified skeletons. This three-part dissertation investigated biological and well-characterized synthetic ACC using high-energy x-ray methods, Raman spectroscopy, and mechanical tests. The findings establish chemical and physical properties of ACC in the exoskeleton of crustaceans and show Mg and P levels are tuned in the mineral component to optimize exoskeleton function that could be sensitive to ecological or environmental conditions. Calcite and chitin crystallinity exhibit a similar body-part-specific pattern that correlates directly with the mechanical strength of the exoskeleton. Insights from this study suggest precise biological control of ACC chemistry in the to regulate exoskeleton properties. Laboratory measurements using quantitative methods and compositions that approximate the physiological conditions of crustaceans, demonstrate at least two types of ACC are formed by controlling Mg concentration and alkalinity. We also find temporal changes in the short-range ordering of ACC after precipitation that is dependent upon carbonate content. The findings from this study provide a quantitative basis for deciphering relationships between ACC structures, solution chemistry, and the final transformation products under biologically relevant conditions. / Ph. D. / With the development of new imaging methods for nano-scale materials, scientists across diverse disciplines have recognized that many earth materials can form complex shapes by the formation and aggregation of nanocrystals or structureless (amorphous) particles. Biological minerals, such as shells and skeletons, are well-documented to form CaCO₃ via both of these attachment pathways, particularly amorphous calcium carbonate (ACC). However, little is known about the ACC properties and the factors that determine the final composition of skeletal minerals. This three-part dissertation focuses on ACC and calcite in the exoskeletons of crustaceans to understand how animals form composite exoskeletons of calcium carbonate minerals. This knowledge is important because CaCO₃ minerals are the primary component of the shells and skeletons of many economically important marine species. These minerals are also prevalent in the geological record as roadmaps for the evolutionary record. Amorphous and crystalline forms of CaCO₃ are also used as inert 'filler' materials for pharmaceutical products. By designing a series of experiments to characterize ACC in exoskeletons from lobsters and crabs, one part of the dissertation shows relationships between chemical composition and physical behavior of the materials. Building on this biomineral information, a separate experimental study synthesizes ACC under near-physiological conditions to show how amorphous CaCO₃ forms under controlled conditions. The findings have far-reaching consequences for understanding the complex chemistry that underlies the formation of calcium carbonate as a component of shells and skeletons, and what physical properties are optimized by the composition of these materials.

Thesis (MTech (Environmental Health))--Cape Peninsula University of Technology, 2018. / Soil ecosystems in urban, rural and agricultural environments receive chemical input from diverse sources of contamination, such as wastewater, industrial discharge, agricultural and urban runoff, fertilizers, vehicle leakages, landfill seepage, and animal waste overspill. Agricultural activities, transportation and industrial activities are suspected to be the highest sources of metal contamination in Cape Town. Although scientists generally have a good understanding of the toxicity of individual chemical pollutants, there is a great need to bridge the gap between our understanding of the toxic effects of exposure to individual contaminants and those effects from exposure to mixtures of chemicals. Woodlice and other soil detritivores have a particularly important ecosystem function in mineralising organic matter. Woodlice experience stress when exposed to toxic levels of metals in the diet, which can reduce feeding rates and may combine with natural stresses to reduce fitness and lower 'performance', thereby possibly resulting in these organisms being unable to completely fulfil their ecological function. The objectives of this study were: to compare how aluminium and manganese are bioaccumulated in Porcellio scaber in terms of the contribution of the hepatopancreas in metal storage compared to the rest of the body; and to determine whether mixtures of aluminium and manganese affect each other’s bioaccumulation and distribution in Porcellio scaber. Woodlice collected from a clean field site (Kirstenbosch Botanical Garden) were experimentally exposed in the laboratory to a range of environmentally relevant aluminium and manganese concentrations. The woodlice were exposed to these metals in single and mixed metal experiments. Oak leaves, collected from a clean site, were contaminated with aluminium and manganese. Therefore, the woodlice were exposed via their food source. A control experiment, where oak leaves were not contaminated, was also prepared. At week 0 and after five weeks of exposure, a sample of the woodlice (5 per exposure group) were dissected to remove the hepatopancreas. Hepatopancreas and rest of the body samples were acid digested and analysed for the metals by means of the ICP-MS. Contrary to the existing knowledge of metals accumulating in the hepatopancreas of woodlice when ingested, this study showed a higher bioaccumulation of aluminium in the rest of the body of woodlice after 5 weeks of exposure than in the hepatopancreas. This result was interpreted as a possible detoxification mechanism by woodlice through the use of the exoskeleton during the moult cycle. A similar result was found when woodlice were exposed to mixtures of aluminium and manganese. This translated to the fact that woodlice were unable to effectively deal with the toxicity caused by the mixture of aluminium and manganese. In the group of woodlice exposed to manganese alone, it was found that manganese concentrations in the rest of the body of woodlice exposed for 5 weeks were statistically higher than the manganese concentrations in the rest of the body of woodlice at the start of the exposure (week 0). However, in the hepatopancreas, there were no statistical differences between the manganese concentrations in week 0 woodlice and the manganese concentrations in week 5 woodlice. Furthermore, manganese concentrations in the rest of the body of week 5 woodlice were statistically higher than manganese concentrations in the hepatopancreas of week 5 woodlice. This was interpreted as further proof that woodlice would accumulate certain metals (aluminium and manganese in this case) in their exoskeleton so that elimination can follow during the moult cycle.