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Dive into the research topics where Maria Amália Sequeira Braga is active.

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Featured researches published by Maria Amália Sequeira Braga.


Chemosphere | 2015

Geochemistry of rare earth elements in a passive treatment system built for acid mine drainage remediation

M.I. Prudêncio; Teresa Maria Fernandes Valente; R. Marques; Maria Amália Sequeira Braga; J. Pamplona

Rare earth elements (REE) were used to assess attenuation processes in a passive system for acid mine drainage treatment (Jales, Portugal). Hydrochemical parameters and REE contents in water, soils and sediments were obtained along the treatment system, after summer and winter. A decrease of REE contents in the water resulting from the interaction with limestone after summer occurs; in the wetlands REE are significantly released by the soil particles to the water. After winter, a higher water dynamics favors the AMD treatment effectiveness and performance since REE contents decrease along the system; La and Ce are preferentially sequestered by ochre sludge but released to the water in the wetlands, influencing the REE pattern of the creek water. Thus, REE fractionation occurs in the passive treatment systems and can be used as tracer to follow up and understand the geochemical processes that promote the remediation of AMD.


International Journal of Phytoremediation | 2014

Metal Uptake by Native Plants and Revegetation Potential of Mining Sulfide-Rich Waste-Dumps

Patrícia Gomes; Teresa Maria Fernandes Valente; J. Pamplona; Maria Amália Sequeira Braga; José Pissarra; José Antonio Grande Gil; María Luisa de la Torre

Waste dumps resulting from metal exploitation create serious environmental damage, providing soil and water degradation over long distances. Phytostabilization can be used to remediate these mining sites. The present study aims to evaluate the behavior of selected plant species (Erica arborea, Ulex europaeus, Agrostis delicatula, and Cytisus multiflorus) that grow spontaneously in three sulfide-rich waste-dumps (Lapa Grande, Cerdeirinha, and Penedono, Portugal). These sites represent different geological, climatic and floristic settings. The results indicate distinctive levels and types of metal contamination: Penedono presents highest sulfate and metal contents, especially As, with low levels of Fe. In contrast, at Lapa Grande and Cerdeirinha Fe, Mn, and Zn are the dominant metals. In accordance, each waste dump develops a typical plant community, providing a specific vegetation inventory. At Penedono, Agrostis delicatula accumulates As, Pb, Cu, Mn, and Zn, showing higher bioaccumulation factors (BF) for Mn (32.1) and As (24.4). At Cerdeirinha, Ulex europaeus has the highest BF for Pb (984), while at Lapa Grande, Erica arborea presents high BF for Mn (9.8) and Pb (8.1). Regarding TF, low values were obtained for most of the metals, especially As (TF < 1). Therefore, the results obtained from representative plant species suggest appropriate behavior for phytostabilization measures.


Geochemistry-exploration Environment Analysis | 2011

Geochemistry and mineralogy of ochre-precipitates formed as waste products of passive mine water treatment

Teresa Maria Fernandes Valente; Marcel D. Antunes; Maria Amália Sequeira Braga; J. Pamplona

ABSTRACT Passive systems with constructed wetlands are designed to simulate natural attenuation processes in order to treat mine water in a long-term and cost-effective manner. In this way, they are especially appropriate to treat mine water discharging from abandoned mines. This paper presents geochemical and mineralogical data obtained from a recently constructed passive system in the Jales abandoned mine, north Portugal. It shows the role of fresh ochre-precipitates, formed as waste products from the neutralization process, in the retention of trace elements. Chemical analysis of these waste products revealed strong enrichment factors for metals and arsenic, relative to the water from which they precipitate. The mineralogical study shows that ochre-precipitates are poorly ordered iron-rich material, such as ferrihydrites, that occur as small spherical aggregates (<0.1 μm in diameter). Heating experiments on these precipitates gave rise to hematite and to a crystalline arsenate. This provides evidence for the scavenging of arsenic by means of a precursor arsenic-rich amorphous compound. The results reveal that ochre-precipitates are wastes of environmental concern, which should be taken into account when considering the possibilities for reuse or disposal.


Chemical Geology | 1993

REE mobilization, fractionation and precipitation during weathering of basalts

M.I. Prudêncio; Maria Amália Sequeira Braga; M. A. Gouveia


Environmental Earth Sciences | 2011

Limestones under salt decay tests: assessment of pore network-dependent durability predictors

Carlos Alves; Carlos Figueiredo; António Maurício; Maria Amália Sequeira Braga; Luís Aires-Barros


Applied Clay Science | 2009

Clay minerals and iron oxides-oxyhydroxides as fingerprints of firing effects in a limestone monument

A. Dionísio; Maria Amália Sequeira Braga; J.C. Waerenborgh


Archive | 2016

Caracterização e proveniência dos materiais de construção e dos fragmentos cerâmicos do povoado da Idade do Ferro do Outeiro do Castro da Bóca (Vila Nova de Famalicão)

J. Pamplona; Teresa Maria Fernandes Valente; Maria Amália Sequeira Braga


Archive | 2014

Indicadores de drenagem ácida num sistema afetado por contaminação mineira: o caso da escombreira de Santo António de Penedono Indicators of Acid Mine Drainage in an affected system: the case of the mine Santo António de Penedono

Patrícia Gomes; Teresa Maria Fernandes Valente; Maria Amália Sequeira Braga; J. Pamplona; J. A. Grande Gil


Energy and Environment Knowledge Week 2014 | 2014

Metals and arsenic enrichment processes in sulfide-rich waste dumps - the role of the clay size fraction

Patrícia Gomes; Teresa Maria Fernandes Valente; Maria Amália Sequeira Braga; J. A. Grande; M. L. De la Torre


Comptes Rendus Geoscience | 2011

Mineralogical and geochemical study of clay and calcite veins in a shear zone related to a sulphur spring (NW Portugal)

Manuela Fonte Lima; J. Pamplona; Maria Amália Sequeira Braga

Collaboration


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M.I. Prudêncio

Instituto Superior Técnico

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A. Dionísio

Instituto Superior Técnico

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António Maurício

Instituto Superior Técnico

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Carlos Figueiredo

Instituto Superior Técnico

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J.C. Waerenborgh

Instituto Superior Técnico

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