Navegando por Assunto "Chumbo"

Agora exibindo 1 - 5 de 5

Acesso aberto (Open Access)
Adsorção de Pb por caulinita tratada com ácidos acético e cítrico
(Universidade Federal do Pará, 2005) SENA, Luciana Freitas de; LEMOS, Vanda Porpino; http://lattes.cnpq.br/1829861620854008
Acesso aberto (Open Access)
Determinação da composição isotópica de chumbo e estrôncio em petróleo e derivados como ferramenta para o monitoramento ambiental
(Universidade Federal do Pará, 2010-04-13) LIMA, Cristiane Souza de; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
O petróleo e seus derivados são vastamente utilizados nos dias atuais para as mais diversas atividades, entretanto, estas substâncias são também importantes fontes de poluição de compostos orgânicos nocivos aos seres vivos, e de introdução de metais pesados no meio ambiente. Dessa forma, o monitoramento de sedimentos, solos e águas naturais em áreas de processamento, armazenamento, manuseio e transporte de hidrocarbonetos deve ser constante para prevenir a contaminação ambiental decorrentes de pequenos vazamentos. Esse monitoramento é feito com a análise de substâncias orgânicas que são biodegradáveis. Alternativamente, ele pode ser realizado pela análise isotópica de metais presentes em pequenas quantidades nessas substâncias. Entretanto, a especificidade das técnicas analíticas envolvidas na extração de metais de substâncias orgânicas não incentiva o uso da composição isotópica de metais no monitoramento ambiental de hidrocarbonetos. Assim, neste trabalho aplicou-se procedimentos usuais na análise de materiais inorgânicos como rocha e solo na extração de metais em petróleo e derivados, com o objetivo de determinar a composição isotópica de chumbo e estrôncio nessas substâncias. As substâncias utilizadas nos procedimentos analíticos foram petróleo, gasolina, biodiesel, óleo lubrificante novo e óleo lubrificante usado. As duas últimas foram utilizadas para comparar eventuais mudanças na composição isotópica do chumbo e estrôncio após o seu uso em motores automotivos. Durante os procedimentos laboratoriais procurou-se encontrar as quantidades adequadas de cada tipo de amostra, para garantir a exatidão e precisão dos resultados analíticos. A implementação da metodologia de extração de metais de petróleo e derivados é o ponto central deste trabalho, onde procurou-se desenvolver um procedimento usando a infraestrutura laboratorial existente com segurança. Assim, o procedimento adotado envolveu a secura das amostras, seguida de calcinação para eliminação de matéria orgânica; dissolução da amostras com ácidos inorgânicos; separação cromatográfica do chumbo e estrôncio utilizando resina especifica de Sr (Sr.Spec); e determinação da composição isotópica de chumbo e estrôncio por espectrometria de massa. Após a realização de diversos ensaios verificou-se que as seguintes quantidades seriam adequadas para a análise isotópica de chumbo e estrôncio: petróleo (5 mL), gasolina (20 mL), biodiesel (20 mL), óleo lubrificante usado (5 mL), óleo lubrificante novo (30 mL). As composições isotópicas de chumbo e estrôncio variam dentro de um estreito limite para as substâncias estudadas. No caso do chumbo, com a razão 206Pb/207Pb apresentado os seguintes valores: petróleo (1,156), biodiesel (1,153), gasolina (1,136), óleo lubrificante novo (1,148) e o óleo lubrificante usado (1,138). Para o estrôncio a razão 87Sr/86Sr apresentou os seguintes valores: petróleo (0,70795), biodiesel (0,70896), gasolina (0,70769), óleo lubrificante novo (0,70812) e óleo lubrificante usado (0,70762). Os valores da razão 206Pb/207Pb do petróleo e derivados são semelhantes àqueles determinados na região metropolitana de Belém e atribuídos a fontes antropogências (~1,140) e, bastante distintos dos valores encontrados para fontes geogênicas (~1,192) nesta mesma região. Essas diferenças nos valores da razão 206Pb/207Pb tornam possível o uso da composição isotópica de chumbo para investigar eventual contribuição antropogênica em sedimentos e solos, proveniente do manuseio, armazenamento e transporte de petróleo e derivados. Por sua vez, a comparação da composição isotópica do estrôncio em petróleo e derivados com àquelas de água subterrâneas na região bragantina, no estado do Pará, por meio do parâmetro 87Sr(‰) mostra valores de 87Sr negativos para o petróleo e derivados, enquanto que para a água subterrânea eles são positivos. Considerando a significativa diferença apresentada nos valores de 87Sr acredita-se que a composição isotópica do estrôncio pode ser empregada como uma ferramenta alternativa para o monitoramento de águas subterrâneas em áreas onde ocorre ou ocorreu o processamento, armazenamento e o manuseio de petróleo e derivados.
Acesso aberto (Open Access)
Especiação e quimissorção de Pb(II) em rejeito de caulim
(2013) PINHEIRO, Marta Helena Tavares; LEMOS, Vanda Porpino; DANTAS, Kelly das Graças Fernandes; VALENTIM, Taynara Lima
This study assesses the adsorption of Pb(II) on natural kaolin waste (KRnatural) and on that treated with 3 mol L-1 H2SO4 and HCl. Equilibrium and thermodynamic parameters were determined. The results indicate that the values of CEC, specific area and SiO2/Al2O3 ratio (4.6-6.0 cmol kg-1, 14.0-16.0 m² g-1 and 1.16-1.30, respectively) vary only slightly for the adsorbents; the concentration of Pb2+ is much higher than that of other species (PbOH+ and Pb(OH) 2). The values of RL, ΔGº, ΔHº and ΔSº are typical of feasible, spontaneous, exothermic and ordered adsorption. The chemisorption on KR natural is more feasible and ordered.
Acesso aberto (Open Access)
Investigação do registro histórico da composição isotópica do chumbo e da concentração de metais pesados em testemunhos de sedimentos no Lago Água Preta, região metropolitana de Belém-Pará
(Universidade Federal do Pará, 2001-08-02) CARVALHO, Maria Clarindo; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
Lake Água Preta is the main water reservoir, which together with Lake Bolonha, constitute the surface water sources for public supply in the city of Belém. Both reservoirs are dams fed by small drainages and water pumped from the Guamá River. These springs are vulnerable to the release of domestic and industrial effluents due to the disorderly urban occupation in their surroundings and their proximity to the Aurá sanitary landfill. In this work, the historical record of the isotopic composition of lead and the concentration of heavy metals in sediment cores from the Água Preta lake was investigated. Different analytical and spectroanalytical methods such as gravimetry, titrimetry, ion exchange chromatography, atomic absorption spectrometry and mass spectrometry were used to obtain the results. In the chemical separation of lead, specific Sr resin (Sr-Spec) was used in Teflon columns, adapting the methodology of Gale (1996). Through preliminary sampling of bottom sediments along the entire length of the Água Preta lake, the distribution of the isotopic ratios of lead and heavy metals was recognized. The lowest values of the 206Pb/207Pb ratio and the highest levels of heavy metals were identified in the lake ramifications close to the urban occupation zones. In this part of the lake, a 77.5 cm column of sediments, called profile 01, was sampled. The highest values of the 206Pb/207Pb ratio were found near the lake dam, which is constantly influenced by the water pumped from the Guamá River; where profile 02 was witnessed with approximately 110 cm of sediment. The 206Pb/207Pb isotopic ratio values were basically grouped into four segments in profile 01 and in three segments in profile 02. -1.20431 in profile 02, refer to the regional isotopic signature. The 206Pb/207Pb isotopic ratio with values varying between 1.19346-1.19602 in profile 02 correspond to the isotopic signature from the influence of suspended sediments in the water of the Guamá River pumped to the lake and whose 206Pb/207Pb ratio is 1. 19225. The isotopic ratios 206Pb/207Pb varying between 1.16223-1.17621 found only in profile 01, correspond to the anthropogenic contribution. The higher averages of heavy metal concentrations in the upper segment of profile 01 justify the interpretation that the lower values for the 206Pb/207Pb ratio are characteristics of anthropogenic contribution. The average levels of heavy metals, found at the top of profile 02, probably reflect the contribution of suspended sediments from the Guamá River to the Água Preta lake, evidenced by the 206Pb/207Pb ratio. The lower values of the average concentrations of the metals found at the base of two profiles reinforce the interpretation that the higher values of the 206Pb/207Pb ratio reflect a regional contribution, prior to anthropogenic action, basically given by the rocks in the area.
Acesso aberto (Open Access)
Potencialidade das assinaturas isotópicas de Pb por espectrometria de massa ICP-MS e TIMS no estudo da proveniência dos azulejos das fachadas históricas de Belém, PA
(Universidade Federal do Pará, 2010-04-13) OLIVEIRA, Etiana Costa; LAFON, Jean Michel; http://lattes.cnpq.br/4507815620234645
Since the eighteenth century, frontages of old buildings from the city of Belem and others Brazilian cities like Salvador, Recife, Rio de Janeiro and São Luis, have been covered with tiles imported principally from Portugal and from others countries of Western Europe, constituting and valorous historical patrimony. The purpose of this study is to evaluate the potentiality of Pb isotopes as a tool for the identification of the provenience of the tiles of historical building from Belem by lead isotope analyses of the tile’s glaze compared with possible Pb ores deposits sources in Western Europe. The study included a comparison of Pb isotopic results obtained by Thermo-ionization mass spectrometry (TIMS) and ICP- mass spectrometry (ICP-MS) on a Finnigan MAT 262 mass spectrometer and a Thermo-Finnigan Neptune ICP-MS mass spectrometer, respectively. Pb isotopes were determined on 36 samples of tiles (23 tiles from Portugal, 5 tiles from England, 4 tiles from France, 4 from Germany). Six samples of tile from the city of São Luis an of unknowm origin , including from de seventeen century, 4 from the eighteenth century and from nineteenth century were also investigated. Additionaly, Pb isotope analyses were also performed on 8 samples of Brazilian modern tiles to evaluate possible distinction between isotopic signature of original European tiles and national replications. A compilation of isotopic signatures of the main Pb deposits in Western Europe and Brazil was necessary in order to compare the Pb isotope compositions of the deposits and tiles. According to the chemical composition and, principally, the high Pb contents of the glaze a simple analytical procedure by HF leaching was adopted for Pb extraction of the glaze, without chemical separation and purification by ion-exchange chromatography. The measurements of Pb isotopic composition by TIMS and ICP-MS on the same samples displayed some differences but these differences do not affect the interpretations of the results. The 208Pb/206Pb vs. 207Pb/206Pb diagram is shown to be the most helpful for the discussion of the Pb isotopic signatures. When comparing with the field of isotopic signatures of Western Europe deposits as probable source of the Pb of the glazes, isotopic compositions indicate that no direct relationship can be established between the country of fabrication of the tile and the country of production of the Pb. Almost the countries from Western Europe may have furnished glaze’s lead. However, Spain (Alcudia Valley), England / Whales and, probably, France have been the main furnishers. Lead produced by the Portuguese deposits and the Cartagena deposits in Spain were not used for the fabrication of the historical study tiles. The similarities in age and geological context of the Pb ore deposits from Western Europe provoked an overlap between the Pb isotopes fields from several countries, making difficult to distinguish the Pb provenience, principally for England, France, Germany and Belgium. Others factors like overlapping of the Pb isotopic signatures produced by different countries, evidences of Pb mixing from several deposits used for the tile fabrication and the lack of confident historical informations about Pb mining and trading in Western Europe, also limited the use of Pb isotopic composition from the tile provenience. Despite these limitations, this study permitted to identify a specific and homogeneous Pb isotopic signature for the older tiles, made before the nineteenth century. It has been also possible to point out the utilization of Pb imported from other continents for the fabrication of some Portuguese, English and German tiles at the end of 19th century or the beginning of the 20th century which is in good agreement with the declining of Pb mining in western Europe during the second half of the 19th century. Portuguese tiles displayed a roughly homogeneous Pb isotope signature depending on the furnisher as well as distinct Pb signatures from furnisher to another one. Then a refining of the study on the base of a larger set of European tiles would possibly be able to be used as a helpful tool for determination of the age and maker of the tiles covering the frontage of historical buildings in Brazil. Finally, this study indicated that Pb used for the fabrication of modern Brazilian tiles and replications of historical tiles of the city of São Luis came from a mixture of Pb from the State of Bahia (Boquira and Nova Redenção deposits). The overlapping of some of the Brazilian modern samples with the field of Western Europe lead deposits and with some of the historical tiles from Western Europe restrain the capability for Pb isotope signature to be employed for distinction between modern and historical tiles.