84 resultados para Mercúrio
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Pós-graduação em Química - IQ
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Worldwide environmental degradation is an undesirable byproduct resulting from the increasing demand for natural resources. Water sources are suffering intense contamination since they usually receive a huge amount of domestic and industrial effluents - which are mostly wasted without proper treatment - inserting a large number of pollutants in the environment, heavy metals included. Mercury holds great toxicological importance because, under some physicochemical conditions in a water environment, Hg (II) ion turns into methylated compounds stemming from this element, such as methylmercury CH3Hg, which is highly toxic for the aquatic community in which bioaccumulation occurs. Nowadays passive sampling techniques are being developed to enable the analytical procedures which are applied in environmental monitoring. Diffusive gradients in thin-films technique (DGT) has been proven an interesting tool for the determination of labile metal species due to its in situ application. The DGT technique consists of a piston-like device on which the following series of agents is disposed: a binding agent (conventionally Chelex 100 resin), a diffusive agent, usually a polyacrylamide gel, and a membrane filter. Nevertheless, the agents conventinally used for this technique don't usually show satisfactory results in mercury sampling. The main goal of this study was to evaluate the phosphate-treated cellulose membrane (Whatman P 81), an alternative material, as binding agent in the DGT to determine labile mercury fractions in aquatic systems. In this context, we conducted a study of the behavior of this material in relation with system variables, pH and ionic strength. Afterwards we performed immersions of the DGT devices in real and enriched samples and in situ aiming the determination of mercury
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To verify the levels of concentration of some heavy metals in fishes from Sorocaba river (São Paulo, Brazil) and evaluate if this contamination offers health risks to the fishermen, 63 samples of fishes collected from four points along the river were studied for cadmium, lead, chromium, nickel and mercury, with emphasis in this last, since it is the most toxic and most probable as a fish contaminant. Analyzing muscle samples by cold vapor atomic absorption spectrometry it was shown that the fishes are not contaminated. None of the five metals studied were present in prohibitive level and the fishes could be judged secure for human consume. It was also analyzed data from four years of cadmium, lead, chromium, nickel and mercury monitoring made by CETESB, from 1997 to 2000, in water from the main rivers of the State of São Paulo. The study pointed out that the majority of the monitored rivers still present contamination by those metals in a level that requires an improvement of the pollution control actions.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Pós-graduação em Geociências e Meio Ambiente - IGCE
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The activation of aluminum surface has the most various purposes as for example the search for the surface activation mechanism and the corrosion products by mercury ions. The objective of this work is to study the reactivity of the surface of aluminum metal when activated by mercury ions (Hg2+), with the consequent formation of an Al-Hg amalgam. Results demonstrate that the kinetics of the reaction, by measuring the mass change with time of the corrosion product formed between Al and Hg, and analysis by infrared spectroscopy (IR) that the product of the reaction between the amalgam, located on the surface, and the atmospheric oxygen is Al2O3 (aluminum hydroxide). The results also indicate that the kinetics of the reaction between the amalgam (Hg-Al) and atmospheric oxygen is of first order and reach a region where there is no more formation of product
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Este estudo foi realizado com o objetivo de se estimar o conteúdo de elementos metálicos presentes em três macrófitas aquáticas submersas, procurando avaliar a participação destas plantas na remoção destes elementos na água e criar base de dados que permita prever o impacto ambiental do descarte delas em solo ou na própria água. As amostras foram desidratadas, moídas e encaminhadas aos laboratórios para análise e quantificação dos elementos. Para as três espécies, a maior concentração de elementos foi observada durante o verão, ocorrendo declínio nas concentrações durante o inverno, principalmente para os elementos vanádio e chumbo. Não foi detectada presença do elemento mercúrio em nenhuma das amostras.
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O objetivo deste trabalho foi avaliar alguns atributos químicos do solo e a disponibilidade de cádmio (Cd), cromo (Cr), níquel (Ni), mercúrio (Hg), chumbo (Pb) e arsênio (As), por meio da extração pelo DTPA, em conseqüência da aplicação superficial de escória de aciaria, lama cal e lodos de esgoto centrifugados e de biodigestores, nas doses 0 (testemunha), 2, 4 e 8 Mg ha-1 e um tratamento adicional composto pela calagem superficial na dose 2 Mg ha-1. O experimento foi conduzido em delineamento de blocos ao acaso, em condições de campo, em área sob sistema plantio direto, durante 2003 e 2004. A aplicação superficial de escória de aciaria, lama cal, lodo de esgoto centrifugado e de biodigestor, até a dose 8 Mg ha-1, assim como o calcário na dose 2 Mg ha-1, não trazem problemas de disponibilidade ao ambiente, com relação aos metais pesados Cd, Cr, Hg, Pb, Ni e As, quando aplicados sobre a superfície em Latossolo Vermelho distrófico, no sistema plantio direto. A fitodisponibilidade de metais pesados às culturas da soja e aveia-preta foi nula, quando foram aplicadas doses de até 8 Mg ha-1 de lodo de esgoto, escória e lama cal sobre a superfície do solo, no sistema plantio direto.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)