Browsing by Author "Valente, Teresa"
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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.
- A geostatistical approach for mercury spatial patterns assessment in sediments in an old mining region: The Caveira Mine case study, PortugalPublication . Mota, Natália; Fonseca, Rita; Araújo, Joana; Isabel Margarida Horta Ribeiro Antunes; Valente, Teresa; Barroso, Ana; Araújo, Alexandre; Albuquerque, Maria Teresa; Zanini , Andrea; D'Oria, MarcoMercury pollution is significant in many former mining communities worldwide, including in developing countries. Anthropic contributions to environmental Hg pollution are mostly connected to fuel fossil emissions, industrial and mining activities. Among mining operations, gold exploration contributes to the highest Hg contamination rates, given the processes, widely used in the past, of mixing Hg with the gold containing ore, to separate this metal from the bulk impurities. This study, as part of the GeoMaTre project, an ongoing collaborative network (2021-2024) between the Polytechnic Institute of Castelo Branco and the University of Évora, Portugal, aimed to evaluate the potential risk of mercury pollution in stream sediments in the Caveira area, an abandoned Cu, Pb, Zn, Ag, and Au mine, included in the Iberian Pyrite Belt, at South Portugal. This mine corresponds to a Gossan developed on pyrite mineralization, with high gold and silver content at the official beginning of its exploitation, in 1863, having exhausted the reserves in these precious metals in the 1920s. Until the date of its abandonment (1966) the exploitation focused on the remaining metals (Cu, Pb, Zn) and S. Currently, the surrounding area of Caveira mine is essentially composed of areas of waste accumulation, from mining activity, with little or no vegetation. Thirty-three sediment samples were collected from within 0 to 10 cm depth, in a grid of 1Km x 1Km. Hg was determined in samples preserved at about 4ºC at the time of collection, through a mercury analyzer (NIC MA 3000) based on thermal decomposition, gold amalgamation, and cold vapor atomic absorption spectroscopy detection.
- Spatial mobility of U and Th in a U-enriched area (Central Portugal)Publication . Antunes, I.M.H.R.; Santos, António; Valente, Teresa; Albuquerque, M.T.D.Uranium and thorium are toxic in different environments. The exploitation of uranium mines and associated mine drainage leaching towards streams, sediments, and soils cause relevant pollution. The U-mine areas present high concentrations of potentially toxic elements with several consequences to ecosystems and human health. Physicochemical and potentially toxic elements of mine dumps, stream sediments, and soils from the Canto Lagar uranium mine area (Central Portugal) were analyzed. Stream sediments, soils, and mine dumps show a large range in the concentration values of Fe, U, As, Cu, Zn, Pb, and Th, suggesting geological and mine contributions. Most of the selected potential toxic elements from sediments present a low to moderate contamination degree, except for As, W, and U, which vary between high and very high contamination index. The soils must not be used in agricultural or residential activities due to contamination in As and U. This abandoned mine represents an environmental risk due to the spatial mobility and dispersion of potentially toxic elements from the dumps to the sediments and soils, as well as by surface runoff and wind.
- 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.
- Water-rock interaction and potential ontamination risk in a U-enriched areaPublication . Antunes, I.M.H.R.; Teixeira, Rui; Albuquerque, M.T.D.; Valente, Teresa; Carvalho, Paula; Santos, AntónioThe Picoto mining area is in the village of Vilar Seco (Viseu), central Portugal. Mineralization occurs mainly in quartz veins with meta-torbernite and uranophane and some U-bearing minerals, cutting a Variscan granite. Exploitation took place in two phases, between 1917 and 1953, and since the closure, the area has never been remediated. Water–rock interaction processes, including the mobility of potentially toxic elements through soil and water (surface and groundwater), were identified with the determination in situ of physicochemical parameters and selected anions and cations, by ICP-OES. The soils are contaminated with As (>44 mg/kg), Cu (>23 mg/kg), and U (>40 mg/kg) and cannot be used for agricultural or domestic purposes. The waters are generally weakly mineralized and have pH values ranging from acidic to neutral. However, some of them are contaminated with NO2 (up to 2.3 mg/L), Fe (up to 1849 mg/L), Mn (up to 777 mg/L), Cu (up to 5.4 g/L), As (up to 14.7 g/L), and U (up to 66.2 g/L) and cannot be used for human consumption or agricultural activities. The soil and water contamination are mainly related to the old mine activities and the subsequent human activities that have developed in the area.