ESTCB - Artigos em revistas com arbitragem científica
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Browsing ESTCB - Artigos em revistas com arbitragem científica by Author "Albuquerque, M.T.D."
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- Algae in acid mine drainage and relationships with pollutants in a degraded mining ecosystemPublication . Gomes, Patrícia; Valente, Teresa; Albuquerque, M.T.D.; Henriques, Renato; Flor-Arnau, Núria; Pamplona, Jorge; Macías, FelipeAcid mine drainage represents an extreme environment with high concentrations of potentially toxic elements and low pH values. These aquatic habitats are characterised by harsh conditions for biota, being dominated by acidophilic organisms. The study site, São Domingos mine, located in one of the largest metallogenetic provinces in the world, the Iberian Pyrite Belt, was closed without preventive measures. To identify the algae species and understand the relationships with abiotic parameters of the ecosystem, water and biological material were collected and analysed. Digital terrain models were obtained with an unmanned aerial vehicle for geomorphological and hydrologic characterisation of the mine degraded landscape. The results show two types of algal colours that seem to represent different degrees of photosynthetic activity. Optical and scanning electron microscopy revealed 14 taxa at the genus level, divided into eight classes. The genus Mougeotia is the most abundant multicellular algae. With respect to unicellular algae, diatoms are ubiquitous and abundant. Abiotic analyses expose typical features of acid mine drainage and support an inverse relationship between chemical contamination and biological diversity. Factorial correspondence analysis indicates three groups of attributes and samples by their relationship with specific toxic elements. This analysis also suggests a close association between Spirogyra and Pb, together composing a structurally simple ecosystem. The highest contamination in the river system is related to the hydrologic patterns obtained from photogrammetric products, such as the digital surface model and flow map accumulation, indicating the input of leachates from the section having the finest sulfide-rich wastes. Information about the algae community and their association with flow patterns of toxic elements is a relevant tool from a biomonitoring perspective.
- Assessment of metal and metalloid contamination in soils trough compositional data: the old Mortórios uranium mine area, central PortugalPublication . Neiva, A.M.R.; Albuquerque, M.T.D.; Antunes, I.M.H.R.; Carvalho, Paula; Santos, A.C.T.; Boente, Carlos; Cunha, Pedro Proença; Henriques, S.B.A.; Pato, R.L.Soils from the old Mortórios uranium mine area were studied to look for contamination, as they are close to two villages, up to 3 km away, and used for agriculture. They are mainly contaminated in U and As and constitute an ecological threat. This study attempts to outline the degree to which soils have been affected by the old mining activities through the computation of significant hot clusters, Traditional geostatistical approaches commonly use raw data (concentrations) accepting that the analyzed elements represent the soil's entirety. However, in geochemical studies these elements are just a fraction of the total soil composition. Thus, considering compositional data is pivotal. The spatial characterization, considering raw and compositional data together, allowed a broad discussion about not only the concentrations' spatial distribution, but also a better understanding on the possibility of trends of "relative enrichment" and, furthermore an insight in U and As fate. The highest proportions (compositional data) on U (up to 33%), As (up to 35%) and Th (up to 13%) are reached in the south-southeast segment. However, the highest concentrations (raw data) occur in north and northwest of the studied area, pointing out to a "relative enrichment" toward the south-southeast zone. The Mondego Sul area is mainly contaminated in U and As, but also in Co, Cu, Pb and Sb. The Mortórios area is less contaminated than the Mondego Sul area.
- Assessment of metal and metalloid contamination in the waters and stream sediments around the abandoned uranium mine area from Mortórios, central PortugalPublication . Neiva, A.M.R.; Carvalho, Paula; Antunes, I.M.H.R.; Albuquerque, M.T.D.; Santos, António; Cunha, Pedro Proença; Henriques, S.B.A.In the abandoned Mortórios uranium mine area there are quartz veins containing wolframite and sulphides and basic rock dykes with torbernite and autunite cutting a porphyritic granite. The basic rock dykes were exploited and produced about 27 t of U3O8, from 1982 to 1988. There are an open pit lake and nine dumps. Surface water and groundwater are contaminated in U, As, Cd, Cr, Cu, Fe, Mn, Ni and Pb. Stream sediments are contaminated in U, As, Th and W, which are adsorbed by smectite, kaolinite and iron- and aluminium- oxy-hydroxides. The maximum U concentrations are of 1268 μg/L in the open pit lake, 100 μg/L in surface water, 103 μg/L in groundwater and 81.5 mg/kg in stream sediments all downstream of the open pit lake and dumps. Further downstream the U concentration in water decreases, due to the high mobility of U (VI), but the U concentration in stream sediments increases. Calcium uranyl carbonate dominates in the open pit lake, but uranyl carbonate complexes dominate in surface water and groundwater. The maximum As concentrations are 56.0 μg/L in the open pit lake, 63.4 μg/L in the surface water and 66.7 μg/L in the groundwater, both downstream of the open pit lake and dumps. The arsenic occurs as As (V). The Mortórios area is compared with two other areas exploited from open pits, all located in the uranium-bearing Beira area of central Portugal. Vale de Abrutiga produced 90 t of U3O8 between 1982 and 1989 and Mondego Sul produced 75 t of U3O8 from 1987 to 1991. The two mines consist of quartz veins containing sulphides, saleeite and meta-saleeite at Vale de Abrutiga and with sulphides, autunite, torbernite, meta-uranocircite and meta-saleeite at Mondego Sul cutting the Schist-graywacke Complex. The mine area of Vale de Abrutiga with the highest exploitation of U3O8 has strongly acidic to slight alkaline water, which is the most contaminated. Mortórios with the lowest exploitation presents a higher contamination of slightly acidic to alkaline water than that of acidic to alkaline water from Mondego Sul, but the former has As (V), whereas the latter has As (III), which is toxic. The stream sediments from Mortórios present the lowest contamination, except for Th that has a higher median value than that from Vale de Abrutiga. Stream sediments from Mondego Sul have higher U, Th, Pb and lower Co, Cr, Cu and Zn median values than those of Vale de Abrutiga.
- Avaliação do nível de contaminação nos sedimentos de cursos de água do Sistema Mineiro de Caveira (Grândola)Publication . Silva, R. da; Fonseca1, R.; Araújo, J. F.; Silva, N.; Albuquerque, M.T.D.O presente trabalho, inserido no Projeto GeoMatRe, visa o levantamento das condições mais atualizadas no que toca aos parâmetros físico-químicos numa mina de drenagem ácida. Uma situação crítica que ocorre na área mineira de Caveira, em Grândola, Portugal, abandonada desde a década de 60 do século passado. O objetivo passa por analisar as condições de contaminação de Elementos Potencialmente Tóxicos (EPT) nos sedimentos que ocorrem quer em fases móveis e dissolvidas na água intersticial dos sedimentos, quer em fases mais imóveis. Neste trabalho é realizada uma caracterização geral da área do sistema mineiro, verificando-se um nível de contaminação da área, através da análise do Índice de Geoacumulação (IGEO) e do Fator de Enriquecimento (FE), onde os elementos Cu, Pb, Zn, As e Hg demonstram ser os principais EPT’s na região, apresentando valores, em alguns dos casos, milhares de vezes acima dos estipulados pelas normas nacionais.
- Bioclimatic modeling in the last glacial maximum, mid-holocene and facing future climatic changes in the strawberry tree (Arbutus unedo L.)Publication . Ribeiro, M.M.A.; Roque, Natália; Ribeiro, Sílvia; Gavinhos, Catarina; Silva, Isabel Castanheira; Quinta-Nova, L.C.; Albuquerque, M.T.D.; Gerassis, SakiIncreasing forest wildfires in Portugal remain a growing concern since forests in the Mediterranean region are vulnerable to recent global warming and reduction of precipitation. Therefore, a long-term negative effect is expected on the vegetation, with increasing drought and areas burnt by fires. The strawberry tree (Arbutus unedo L.) is particularly used in Portugal to produce a spirit by processing its fruits and is the main income for forestry owners. Other applications are possible due to the fruit and leaves' anti-oxidant properties and bioactive compounds production, with a potential for clinical and food uses. It is a sclerophyllous plant, dry-adapted and fire resistant, enduring the Mediterranean climate, and recently considered as a possibility for afforestation, to intensify forest discontinuity where pines and eucalypts monoculture dominate the region. To improve our knowledge about the species' spatial distribution we used 318 plots (the centroid of a 1 km2 square grid) measuring the species presence and nine environmental attributes. The seven bioclimatic variables most impacting on the species distribution and two topographic features, slope and altitude, were used. The past, current and future climate data were obtained through WorldClim. Finally, the vulnerability of the strawberry tree to the effects of global climate change was examined in the face of two emission scenarios (RCP 4.5 and 8.5), to predict distribution changes in the years 2050 and 2070, using a species distribution models (MaxEnt). The reduction of suitable habitat for this species is significant in the southern regions, considering the future scenarios of global warming. Central and northern mountainous regions are putative predicted refuges for this species. Forest policy and management should reflect the impact of climate change on the usable areas for forestry, particularly considering species adapted to the Mediterranean regions and wildfires, such as the strawberry tree. The distribution of the species in the Last Glacial Maximum (LGM) and Mid-Holocene (MH) agrees with previous genetic and paleontological studies in the region, which support putative refuges for the species. Two in the southern and coastal-central regions, since the LGM, and one in the east-central mountainous region, considered as cryptic refugia.
- Combining raw and compositional data to determine the spatial patterns of potentially toxic elements in soilsPublication . Boente, Carlos; Albuquerque, M.T.D.; Fernández-Braña, A.; Gerassis, Saki; Sierra, C.; Gallego, J.R.When considering complex scenarios involving several attributes, such as in environmental characterization, a clearer picture of reality can be achieved through the dimensional reduction of data. In this context, maps facilitate the visualization of spatial patterns of contaminant distribution and the identification of enriched areas. A set, of 15 Potentially Toxic Elements (PTEs) – (As, Ba, Cd, Co, Cr, Cu, Hg,Mo, Ni, Pb, Sb, Se, Tl, V, and Zn), was measured in soil, collected in Langreo's municipality (80 km2), Spain. Relative enrichment (RE) is introduced here to refer to the proportion of elements present in a given context. Indeed, a novel approach is provided for research into PTE fate. This method involves studying the variability of PTE proportions throughout the study area, thereby allowing the identification of dissemination trends. Traditional geostatistical approaches commonly use raw data (concentrations) accepting that the elements analyzedmake up the entirety of the soil. However, in geochemical studies the analyzed elements are just a fraction of the total soil composition. Therefore, considering compositional data is pivotal. The spatial characterization of PTEs considering raw and compositional data together allowed a broad discussion about, not only the PTEs concentration's distribution but also to reckon possible trends of relative enrichment (RE). Transformations to open closed data are widely used for this purpose. Spatial patterns have an indubitable interest. In this study, the Centered Log-ratio transformation (clr) was used, followed by its back-transformation, to build a set of compositional data that, combined with raw data, allowed to establish the sources of the PTEs and trends of spatial dissemination.
- Compositional baseline assessments to address soil pollution : an application in Langreo, SpainPublication . Boente, Carlos; Albuquerque, M.T.D.; Gallego, J.R.; Pawlowsky-Glahn, Vera; Egozcue, Juan JoséPotentially Toxic Elements (PTEs) are contaminants with high toxicity and complex geochemical behaviour and, therefore, high PTEs contents in soil may affect ecosystems and/or human health. However, before addressing the measurement of soil pollution, it is necessary to understand what is meant by pollution-free soil. Often, this background, or pollution baseline, is undefined or only partially known. Since the concentration of chemical elements is compositional, as the attributes vary together, here we present a novel approach to build compositional indicators based on Compositional Data (CoDa) principles. 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-pollutant; 3) Computing the spread Aitchison distance from each sample point to the trimmed sample; 4) Performing a compositional balance able to predict the Aitchison distance computed in step 3. Identifying a compositional balance, including pollutant and non-pollutant elements, with sparsity and simplicity as properties, is crucial for the construction of a Compositional Pollution Indicator (CI). Here we explored a database of 150 soil samples and 37 chemical elements from the contaminated region of Langreo, Northwestern Spain. There were obtained three Cis: the first two using elements obtained through CoDa analysis, and the third one selecting a list of pollutants and non-pollutants based on expert knowledge and previous studies. The three indicators went through a Stochastic Sequential Gaussian simulation. The results of the 100 computed simulations are summarized through mean image maps and probability maps of exceeding a given threshold, thus allowing characterization of the spatial distribution and variability of the CIs. A better understanding of the trends of relative enrichment and PTEs fate is discussed.
- Construction of a quality index for granules produced by fluidized bed technology and application of the correspondence analysis as a discriminant procedurePublication . Albuquerque, M.T.D.; Dias, Vítor H.; Poellinger, Norbert; Pinto, João F.The production of granules by wet granulation in a fluidized bed was assessed after the construction of a quality index based on a file of attributes (relevant factors). These attributes are combined by a methodology relying on Correspondence Analysis, as a discriminant procedure, using two extreme simulated active vectors representing, respectively, the best and the worst cases for the granules quality output (“bad” and “good” pole). From those, a single continuous synthetic variable – the quality index – can be produced referring to a more significant set of samples. As an application of the methodology, the work compares the quality of granules produced at a laboratory scale and a pilot scale. The factors contribution to the bad or good pole allowed the identification of the most relevant factors that affect the quality of the granules. The factors studied, according to a center of gravity design, included formulation (solubility of a drug, different grades of polyvinylpyrrolidone, the polarity of the granulation solution) and processing factors (the rate of administration of the granulation solution, the atomizing air pressure and the fluidizing air rate). Granules were evaluated for production yield, drug content, size, densities (true, bulk and tapped), friability, flowability and compressibility. The study has emphasized the differences between the laboratory and pilot scales and the relative importance of each factor for the quality of the granules produced.
- A coupled multivariate statistics, geostatistical and machine-learning approach to address soil pollution in a prototypical Hg-mining site in a natural reservePublication . Boente, Carlos; Albuquerque, M.T.D.; Gerassis, Saki; Rodríguez-Valdés, E.; Gallego, J.R.The impact of mining activities on the environment is vast. In this regard, many mines were operating well before the introduction of environmental law. This is particularly true of cinnabar mines, whose activity has declined for decades due to growing public concern regarding Hg high toxicity. Here we present the exemplary case study of an abandoned Hg mine located in the Somiedo Natural Reserve (Spain). Until its closure in the 1970s, this mine operated under no environmental regulations, its tailings dumped in two spoil heaps, one of them located uphill and the other in the surroundings of the village of Caunedo. This study attempts to outline the degree to which soil and other environmental compartments have been affected by the two heaps. To this end, we used a novel combination of multivariate statistical, geostatistical and machine-learning methodologies. The techniques used included principal component and clustering analysis, Bayesian networks, indicator kriging, and sequential Gaussian simulations. Our results revealed high concentrations of Hg and, secondarily, As in soil but not in water or sediments. The innovative methodology abovementioned allowed us to identify natural and anthropogenic associations between 25 elements and to conclude that soil pollution was attributable mainly to natural weathering of the uphill heap. Moreover, the probability of surpassing the threshold limits and the local backgrounds was found to be high in a large extension of the area. The methodology used herein demonstrated to be effective for addressing complex pollution scenarios and therefore they are applicable to similar cases.
- A coupled multivariate statistics, geostatistical and machine-learning approach to address soil pollution in a prototypical Hg-mining site in a natural reservePublication . Boente, Carlos; Albuquerque, M.T.D.; Gerassis, Saki; Rodríguez-Valdés, E.; Gallego, J.R.The impact of mining activities on the environment is vast. In this regard, many mines were operating well before the introduction of environmental law. This is particularly true of cinnabar mines, whose activity has declined for decades due to growing public concern regarding Hg high toxicity. Here we present the exemplary case study of an abandoned Hg mine located in the Somiedo Natural Reserve (Spain). Until its closure in the 1970s, this mine operated under no environmental regulations, its tailings dumped in two spoil heaps, one of them located uphill and the other in the surroundings of the village of Caunedo. This study attempts to outline the degree to which soil and other environmental compartments have been affected by the two heaps. To this end, we used a novel combination of multivariate statistical, geostatistical and machine-learning The techniques used included principal component and clustering analysis, Bayesian networks, indicator kriging, and sequential Gaussian simulations. Our results revealed high concentrations of Hg and, secondarily, As in soil but not in water or sediments. The innovative methodology abovementioned allowed us to identify natural and anthropogenic associations between 25 elements and to conclude that soil pollution was attributable mainly to natural weathering of the uphill heap. Moreover, the probability of surpassing the threshold limits and the local backgrounds was found to 31 be high in a large extension of the area. The methodology used herein demonstrated to be effective for addressing complex pollution scenarios and therefore they are applicable to similar cases.