ESTCB - Comunicações em encontros científicos e técnicos
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- Soil stabilization with sisal fibresPublication . Luzia, Rosa; Gardete, Dinis; Diogo MonteiroSoil stabilization using natural fibres is a solution that can have environmental and technical advantages. Among the natural fibres that have adequate characteristics are sisal fibres. In this work, were used sisal fibres to evaluate its potential to improve the characteristics of soils for embankment and road pavement layers construction. Was characterized a clayey sand soil, in its natural state and after mixing it with sisal fibres. The mixture with 0.5%, 1.0% and 1.5% of sisal fibres with 15mm length was characterized and the bearing capacity of the soil was determined using CBR tests (California Bearing Ratio). The results from the tests show that sisal fibre stabilization leads to a decrease, although slight, in the CBR values, for 2.5mm and 5.0mm of penetration. However, when observing the penetration/force curves, the natural soil performed better between 0.0mm and 6.0mm of penetration, suffering a break after 6.0mm, while mixtures with 1.0% and 1.5% of fibres maintained a practically linear progress up to 12mm of penetration.
- Impacto do aumento das temperaturas na vida útil dos pavimentos – análise para as condições de Castelo BrancoPublication . Gardete, Dinis Correia; Rosa Luzia; Capitão, Silvino; De Picado Santos, Luis G.; Autor correspondente: Gardete, Dinis Correia.As consequências das alterações climáticas no desempenho e vida útil dos pavimentos rodoviários flexíveis poderão ser muito significativas. Entre os vários fatores com potencial para impactar na manutenção e desempenho destes está o aumento das temperaturas. Neste trabalho foram recolhidos dados sobre as temperaturas históricas e estimadas para Castelo Branco para as trajetórias de concentração de gases de efeito estufa (Representative Concentration Pathways) RCP4.5 e RCP8.5. Utilizando o método da Shell foi avaliado o impacto no dimensionamento dos pavimentos da subida estimada das temperaturas até ao fim do século. Foi determinada a influência desta subida na temperatura ponderada do ar, na temperatura de serviço para dimensionamento, no módulo de deformabilidade de misturas betuminosas utilizadas em Portugal e na vida útil de uma estrutura típica de pavimento flexível. Os resultados obtidos indicam que mesmo no cenário RCP4.5 o efeito da subida de temperaturas é significativo, cerca de 12% de redução no módulo de deformabilidade e 3 anos de redução na vida útil. Para o cenário RCP8.5 os efeitos são significativamente ampliados com a redução do módulo de rigidez de cerca de 35% e com uma redução da vida útil do pavimento superior a 6 anos.
- Stream sediments as a contamination repository around an abandoned uranium mine, central PortugalPublication . Carvalho, Paula; Boente, Carlos; Albuquerque, M.T.D.; Santos, António; Cunha, Pedro ProençaIn central Portugal, some abandoned uranium mines were already remediated [1]. However, some others may be responsible for potential environmental risks due to geochemical dynamics. The abandoned Barrôco D. Frango uranium mine has an open pit lake 50 m long and 10 m wide, and a ~40,020 m3 mine dump. A contamination assessment was carried out along the main stream, by collecting water samples in four seasons (2016 - 2017) and stream sediments (2016). Surface waters are generally near-neutral to alkaline (5.83 - 7.55), with uranium, thorium and arsenic concentration ranges of 4.5 - 37.3 µg/L, 2.7 -11.0 µg/L and 4.8 - 39.5 µg/L, respectively. Water´s uranium concentrations tend to be higher in winter due to the dissolution of uranium minerals in dumps, while any distinction is observed with thorium. Water has arsenic and heavy metals lower than the permitted values for agricultural irrigation. However, sediments with median uranium concentration of 53.3 mg/kg (41.9 - 189 mg/kg) and thorium of 49.0 mg/kg (27.2 - 81.9 mg/kg), present moderate to considerable ecological risk (RI= 34.31 - 78.79), mainly due to arsenic concentrations (25.4 - 60.6 mg/kg).
- Soil pollution: A compositional baseline approach in Langreo, SpainPublication . Albuquerque, Maria Teresa; Boente, Carlos; Gallego, J.R.; Pawlowsky-Glahn, Vera; Egozcue, Juan José; Thomas-Agnan, Ch.; Pawlowsky-Glahn, VeraThe complex geochemical behavior associated to the spatial distribution of potentially toxic elements (PTE) in soils can affect ecosystems and/or human health. However, before considering the measurement of soil pollution, there is a need to understand what is meant by pollution-free soil. In many cases, this context, or the basis of pollution, is not defined or only partially known. Since the concentration of the chemical elements is compositional, as the attributes vary together, a new approach is introduced aiming at the construction of compositional indicators based on the principles of Compositional Data Analysis (CoDa). The steps of this new methodology are: 1) Exploratory data analysis through variation matrix, biplots, or CoDa dendrograms; 2) Selection of geological background in terms of a trimmed subsample that can be assumed as non-polluted; 3) Computing the Aitchison distance from each sample point to the trimmed sample; 4) Finding a compositional balance able to predict the Aitchison distance computed in step 3. The identifi cation of a compositional balance, including pollutants and non-polluting elements, with sparse and simple properties, is crucial for building a Compositional Pollution Index (CI). A 150 soil samples dataset, from the contaminated region of Langreo, northwest Spain, corresponding to 37 chemical elements was used as a pilot survey. As a first approach, three CIs were obtained. The corresponding spatial distribution was computed using Gaussian sequential stochastic simu lation. The results of the 100 obtained scenarios are summarized through mean image maps and probability maps of exceeding a given threshold. The characterization of the spatial distribution and variability of the CIs allowed a better understanding of relative enrichment patterns and the fate of PTEs.
- Stream sediments geochemistry in the Valongo anticline, northern Portugal: Arsenic as a proxy to outline new exploration targetsPublication . Carvalho, Paula; Albuquerque, Maria Teresa; Chambel, L.; Silva, M.; Rocha, F.O anticlinal de Valongo é conhecido pela ocorrência de vários depósitos minerais de Sb-Au e As-Au, muitos deles explorados desde os tempos romanos. Os depósitos de Sb-Au e As-Au ocorrem nos filões de quartzo com estrutura brechóide com direção predominante NE-SW, NNW-SSE, e ENE-WSW cortando formações do Câmbrico ao Carbónico. Uma campanha de 801 sedimentos de corrente foi obtida nesta área. A krigagem factorial foi aplicada como um método de interpolação, usando o Arsénio (As) como proxy para delinear novos alvos de exploração. Os resultados permitem a identificação de alinhamentos NW-SE e NE-SW, como preferenciais para teores elevados de As. Estudos futuros irão usar informação estrutural e a distribuição das antigas escombreiras para obter uma maior precisão nas áreas para prospeção mineira.
- Influência dos rejeitos de uma mina de sulfuretos na qualidade da água de drenagem, 60 anos após o seu abandono: Caso de estudo no SW de PortugalPublication . Araújo, J.; Fonseca, R.; Albuquerque, Maria Teresa; Silva, N.; Silva, R.The GeoMatRe project aims to find low-cost solutions for water and sediment rehabilitation using raw geomaterials, in abandoned mines of the Iberian Pyritic Belt. One of our case studies is the Caveira mine in southwestern Portugal, where large piles of mining waste, containing significant amounts of metals, record the long history of its exploitation for Au and Ag. After the exhaustion of its reserves, the extraction of the remaining metals (Cu, Pb, Zn) and S continued, until its abandonment during the 60s of XX century. This work has two objectives: (i) to study the influence of mine and mine tailings drainage on water quality by analyzing the dissolved and particulate material in drainage waters, and (ii) to determine whether there are differences in these waters according to the different climatic conditions of the last two winters. Therefore, we will conduct a new sampling campaign, which will allow us to make a comparative study.
- Observação do nível de contaminação nos sedimentos de cursos de água do Sistema Mineiro de Caveira (Grândola)Publication . Fonseca, R.; Araújo, J.; Silva, N.; Albuquerque, Maria TeresaFollowing the present work inserted in the GeoMatRe Project, an ongoing project funded by Fundação La Caixa, the conditions of the most updated physical and chemical parameters of an Acid Mine Drainage are analysed, a critical situation which occurs in the mining area of Caveira (Grândola, Portugal), abandoned since the 60’s. It is intended, within the scope of the project, to observe the conditions of contamination by Potentially Toxic Elements in the sediments, both dissolved and suspended forms in the water column, in order to carry out a general characterization of the mining system, based on the nature and amounts of the contaminating elements, as well as the conditions of acidification occurring on sediments present in the environment that surrounds the mining area. The aim is to understand, based on the existing conditions, the best environmental remediation technology to be applied in the region.
- Mobility of uranium in groundwater-surface water systems in a post-mining context (Central Portugal)Publication . Antunes, I.M.H.R.; Carvalho, Paula; Albuquerque, Maria Teresa; Santos, A.C.T.In uranium abandoned mine areas, particularly with mine tailings and open-pit lakes, the mobility of potentially toxic elements still acts as a source of surface and groundwater contamination. e water of open-pit lakes from Ribeira de Bôco mine and associated groundwater and surface water from the area is neutral and with low metal contents. However, some water samples are contaminated with Cd, Cr, Cu, Fe, Mn, As, and U and should not be used for human consumption or in agricultural activities. e baseline uranium threshold is considerably high for groundwater, which is supported by geogenic features and mining activities.
- Unpacking occupational health data in the tertiary sector. From spatial clustering to bayesian decision makingPublication . Pazo, María; Boente, Carlos; Albuquerque, M.T.D.; Roque, Natália; Gerassis, Saki; Taboada, Javier; Zanini , Andrea; D'Oria, MarcoThe health status of the service sector workforce is a great unknown for medical geography. Despite the advances carried out by spatial epidemiology to predict spatial patterns of disease incidence, there are important challenges unsolved. In particular, the main issue resides in the ability to effectively simplify and visually represent the problem domain, given the need to cover very different service activities and, at the same time, consider the impact of numerous emerging risk factors such as those stemming from bioclimatic and socioeconomic variables. This article proposes a new approach that allows to consider, simplify, prioritise and visualise multiple occupational health risk factors giving rise to not healthy workers. For that, it is used a twofold approach based on an innovative synergy between Bayesian machine learning and geostatistics, to analyse up to 74.401 occupational health surveillance tests gathered between 2012-2016 in Spain. This solution allows to extract relevant patterns over those risk factors that cannot be further discriminated in the Bayesian network, such as spine or limbs observations, depicting distribution maps of key differentiating variables computed by an ordinary kriging approach.
- Stream sediments pollution: A compositional baseline assessment at the Caveira mine, PortugalPublication . Araújo, Joana; Fonseca, Rita; Mota, Natália; Araújo, Alexandre; Antunes I.M.H.R.; Valente, Teresa; Barroso, Ana; Albuquerque, Maria Teresa; Zanini , Andrea; D'Oria, MarcoA high concentration of Potentially Toxic Elements (PTE) can affect ecosystem health. It is therefore essential that spatial trends of pollutants are assessed and controlled. River sediment pollution is widespread in mining communities around the world, including in developing countries. This study, as part of the GeoMaTre project, restoration of water bodies impacted by mine drainage, an ongoing collaborative project (2021-2024) between the Polytechnic Institute of Castelo Branco and the University of Évora, Portugal, aimed to evaluate the potential risk of PTEs pollution in stream sediments under the direct influence of Caveira mine, a Cu-Pb Zn-Ag-Au old mine included in the Iberian Pyrite Belt, South Portugal. Quantifying pollution implies first the understanding of pollution-free stream sediment. Often, this background, or pollution baseline, is undefined or only partially known. Given that the concentration of chemical elements is compositional, as the attributes vary together, a compositional approach was used aiming to find a compositional balance, based on Compositional Data (CoDa) principles. A dataset of 33 samples was collected from within 0 to 10 cm depth, in a grid of 1Km x 1Km and thirteen chemical elements, including PTEs of variable toxicity (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Zn, V) and major elements from lithogenic sources (Fe, Al), were analyzed in preservedsamples at about 4°C. The most extractable forms of metals (except for Hg) were obtained by partial digestion with aqua regia (HCl and HNO3) in a high-pressure microwave digestion unit, followed by ICP-OES analysis. Hg was analyzed determined by a mercury analyzer based on thermal decomposition, gold amalgamation, and cold vapor atomic absorption spectroscopy detection.