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Mineralogical attenuation for metallic remediation in a passive system for mine...
Valente, Teresa Maria Fernandes; Antunes, M.; Braga, M. A. Sequeira; Prudêncio, M. I.; Marques, R.; Pamplona, J.Passive systems with constructed wetlands have been consistently used to treat mine water from abandoned mines. Long-term and cost-effective remediation is a crucial expectation for these water treatment facilities. To achieve that, a complex chain of physical, chemical, biological, and mineralogical mechanisms for pollutants removal must be designed to simulate natural attenuation processes. This paper aims to...
Prediction of the mechanical behavior of the Oporto granite using data mining t...
Martins, Francisco F.; Begonha, Arlindo; Braga, M. A. SequeiraThe determination of mechanical properties of granitic rocks has a great importance to solve many engineering problems. Tunnelling, mining and excavations are some examples of these problems. The purpose of this paper is to apply Data Mining (DM) techniques such as multiple regressions (MR), artificial neural networks (ANN) and support vector machines (SVM), to predict the uniaxial compressive strength and the ...
Mineralogical and geochemical study of clay and calcite veins in a shear zone r...
Lima, Manuela Fonte; Pamplona, J.; Braga, M. A. SequeiraIn the Terras de Bouro area, in Northwest Portugal, the role of water-rock interaction, either by the mineralization of the sulphur spring, or by the nature of the granite secondary minerals, was studied as a complement to exploration for mineral water. This approach is justified by the peculiar mineral paragenesis found, which is very different from those of the regional weathering products. Calcite and montmo...
Mineralogical composition and metals retention in the fine-fraction streambed p...
Alves, Raquel Cepeda; Valente, Teresa Maria Fernandes; Braga, M. A. Sequeira; Gomes, C. LealThis work presents data from an abandoned mine (Valdarcas, NW Portugal) that, although submitted to environmental rehabilitation, stills presenting marks of AMD. Water and sediment samples from the riverine system were analyzed for chemical composition and mineralogy. Chemical contents of Fe, As and W in the < 20μm fraction indicate strong enrichment relatively to the water. Proportions of iron oxide-oxyhydroxi...
Manganese oxides as biominerals in a granitic subterranean environment
Miller, A.; Dionísio, A.; Braga, M. A. Sequeira; Afonso, M. J.; Jurado, V.; Fernandez-Cortes, A.; Cuezva, S.; Sanchez-Moral, S.; Saiz-Jimenez, C.Black coatings were detected on granite surfaces in groundwater catch work tunnels from Porto city (NW Portugal). XRD, FTIR, Micro-Raman, ICP-MS, TEM-EDS, SEM-EDS and SEM-FIB were the analytical procedures carried out to investigate the origin of the black coatings. In this subterranean environment, the enrichment in metals and other trace elements, such as Mn and Fe, and clay minerals characterize the black mi...
Origem dos filmes negros sobre património construído : diversos olhares
Oliveira, B. Pereira de; de la Rosa, J.; Miller, A.; Dionísio, A.; Silveira, T.; Braga, M. A. SequeiraOs filmes negros desenvolvem-se sobre substrato granítico com morfologia idêntica ao mesmo. A sua eliminação requer métodos abrasivos e/ou químicos por forma a superar a impermeabilidade e dureza característica. A génese de formação dos filmes negros é o elemento fundamental para contribuir para a preservação e sustentabilidade do património construído granítico na perspectiva de minimizar o seu desenvolvimento...
Laboratory-induced endolithic growth in calcarenites : biodeteriorating potenti...
Miller, A. Z.; Rogerio-Candelera, M. A.; Laiz, L.; Wierzchos, J.; Ascaso, C.; Braga, M. A. Sequeira; Hernández-Mariné, M.; Maurício, A.; Dionísio, A.This study is aimed to assess the formation of photosynthetic biofilms on and within different natural stone materials, and to analyse their biogeophysical and biogeochemical deterioration potential. This was performed by means of artificial colonisation under laboratory conditions during 3 months. Monitoring of microbial development was performed by image analysis and biofilm biomass estimation by chlorophyll ...
A disjunção colunar na chaminé vulcânica de Penedo de Lexim (Complexo Vulca...
Brilha, J. B.; Braga, M. A. Sequeira; Proust, Dominique; Dudoignon, PatrickA disjunção colunar na chaminé vulcânica do Penedo de Lexim é caracterizada por apresentar um Indice de Hexagonalidade de 1.03 o que lhe confere um padrão de fracturação próximo do ‘maturo’. O facto do processo de arrefecimento ter ocorrido a 2000 m de profundidade induziu alguns factores que condicionaram decisivamente a génese da disjunção colunar, pelo que as colunas do Penedo deLexim apresentam ...
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