4161 research outputs found
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Clean production of microalgae high-value lipid fraction: Influence of different pretreatments on chemical and cytotoxic profiles of Chlorella vulgaris supercritical extracts and life cycle assessment
No full textABSTRACT: Microalgae have emerged as a promising natural resource rich in bioactive compounds. Health-beneficial properties of microalgae, coupled with advantageous characteristics such as high biomass productivity, adaptability, robustness, and carbon dioxide mitigation, position them as a viable solution for global sustainable food production. This study explored clean and environmentally friendly processes to enhance the recovery of lipid bioactive fractions. Microwave (MW), enzymatic (ENZ), and ultrasound (US) pretreatments were applied to improve environmentally friendly extraction of lipid-based components using supercritical CO2. The effects of these pretreatments on extraction yield, chemical profiles, and cytotoxic properties of Chlorella vulgaris (Cv) and smooth C. vulgaris (sCv) extracts were investigated. Additionally, a Life Cycle Assessment (LCA) was conducted to evaluate environmental impacts. MW pretreatment achieved the highest yield increases, from 2.58 times (Cv) to 3.15 times (sCv). UHPLC-ESI-HRMS analysis revealed shifts in the distribution of pigments and derivatives caused by pretreatments, with ENZ extracts showing the most pronounced changes: pigments increased from 9.24% (control Cv) to 40.92% (Cv) and from 12.52% (control sCv) to 71.12% (sCv). Cv extracts exhibited greater activity against MDA-MB-453 cells, while sCv extracts from US pretreatment demonstrated the strongest effect on HeLa cells. The LCA indicated reduced environmental impacts of the pretreatment-enhanced processes up to 65% compared to the control. A scenario analysis was presented to show further possible impact reduction by recirculating the CO2 solvent and substituting the energy source. These findings provide valuable insights into sustainable and scalable green processes for recovering microalgal bioactive components
Detection of corrosion on silvered glass reflectors via image processing
No full textABSTRACT: A novel characterization technique based on image analysis is presented, intended to complement state-of-the-art reflectometer measurements. The technique is developed by experts from different laboratories (OPAC, AGC, CEA and LNEG), which subsequently conduct two Round Robin experiments on corroded solar reflectors for validation. Regarding the inter-comparability, it is found that parameters like the corrosion spot density or the penetration maximum on coated edges exhibit an average coefficient of variation of 62.6 % and 54.9 %. Better agreement is found for parameters like the total corroded area and the maximum edge corrosion penetration, with coefficients of variation of 14.3 % and 13.4 %, respectively. The developed methodology is further applied during a 68-month lasting outdoor exposure campaign of two types of solar reflectors at two representative sites, one exhibiting corrosivity class C2 and the other C3. On the commercial coating RL1, a total corroded area of 59 mm2 and 426 mm2 is measured after the outdoor exposure on the C2 and the C3 site, respectively, while on the novel low-lead coated reflector RL3 corresponding values are 280 mm2 and 1308 mm2. This shows the superior quality of the coating RL1 in terms of corrosion resistance. Furthermore, the analysis highlights the importance of proper edge sealing for corrosion protection, since corrosion penetration is increased by a factor between 1.3 and 4.0 if the edges are unprotected. The reflectance decrease after the outdoor exposure is regarded as negligible (0.000 - 0.005), thus not permitting any of the conclusions that are made from the novel image analysis technique
Thermally modified wood: assessing the impact of weathering on mechanical strength and exposure to subterranean termites
No full textABSTRACT: The main objective of this study was to evaluate the mechanical properties of three thermal-modified wood species when exposed to weathering in urban and maritime/industrial environments and their durability against subterranean termites. The wood species studied were Maritime pine, ash, and blackwood acacia. All wood samples were exposed to two different environments (urban and maritime/industrial) for 24 months. Then, its physical and mechanical properties were evaluated (modulus of elasticity (MOE), modulus of rupture (MOR), compression strength (CS), and modulus of compression (MOC). Thermally modified woods revealed a lower density, which could explain the loss of MOE and MOR. In compression, no significant changes were verified. The weathered samples showed changes in mechanical properties, mostly verified in MOE and MOR, where some decreases were reported in both locations. Tests were performed to evaluate biodegradation and the resistance of all wood samples to subterranean termites. The grade of attack (approximate to 4) and termite survival rate were similar in all wood species (above 75% and lower than 80%), except for modified acacia (59%), which could indicate that thermal modification increased toxic substances. The cellulose degradation was reflected in FTIR-ATR and Py-GC/MS in natural and thermally modified woods. Py-GC/MS showed a decrease in levoglucosan, while lignin suffered some modifications with slight changes in monomeric composition reflected by the reduction of the S/G ratio. No changes were found between the two environments, and thermal modification did not give extra protection against termites and weathering
Potential areas for public domain mineral resources in Portugal
No full textRESUMO: O ordenamento do território é decisivo no processo de garantir o acesso aos recursos minerais. Durante os trabalhos para identificar as ações necessárias para a preparação da Estratégia Nacional para os Recursos Geológicos foi produzido um mapa de áreas potenciais em recursos minerais de Portugal. Constitui um ponto de partida para a implementação de uma metodologia vocacionada para a delimitação de áreas para a salvaguarda de recursos minerais.ABSTRACT: Land-use planning is decisive for granting access to mineral resources. During the work to identify the actions to be taken for preparing the National
Strategy for Geological Resources, a map of mineral potential areas for Portugal was produced. It provides a starting point scenario for the implementation of a
methodology aimed at the delineation of mineral safeguarding areas
Influence of severe drought on surface water indicators
No full textRESUMO: Durante a seca que afetou Portugal no ano hidrológico de 2021/2022, foram realizadas cinco campanhas de monitorização das águas superficiais na bacia hidrográfica do Rio Mondego. A amostragem ocorreu de março a novembro de 2022 e os indicadores de qualidade da água medidos foram comparados com um fundo geoquímico criado a partir de dados abertos. Durante o período de seca, as águas superficiais parecem tendencialmente mais alcalinas potencialmente devido à menor diluição ou a uma influência bicarbonatada proveniente de águas subterrâneas. No mesmo período as concentrações de NO2 tenderam a aumentar, quase sempre acima de teores normais. No início do ano hidrológico seguinte, com eventos de chuva intensa, e um aumento do escoamento, erosão e transporte de partículas do solo, notou-se um aumento da turbidez, com valores acima do normal, associado a concentrações excessivas de Al, Fe e Mn, enquanto se verificou o regresso aos valores normais de pH e NO2.ABSTRACT: During the drought that affected Portugal in the hydrological year 2021/2022, five monitoring campaigns of surface waters were conducted in the Mondego River basin. These monitoring campaigns took place from March to November 2022 and involved measurements of electric conductivity, pH, and turbidity. Additionally, samples were collected for the chemical analysis of major and minor ions, as well as metals and metalloids. The results from these campaigns were then compared with a geochemical background created from open data for nearby quality stations. The reduced water availability, and consequently, the dilution capacity, coupled with an increased influence of groundwater on surface water, appears to have led to shifts towards more alkaline waters and an increase in NO2 concentrations. Reduced precipitation also restricts the mobilization of soil elements into water bodies, resulting in lower concentrations of certain metals (Al, As, Fe, and Mn) in surface water. In the post-drought period, at the beginning of the rainy season, increased runoff, erosion, and sediment transport seem to have caused an increase
in surface water turbidity and concentrations of Al, Fe, and Mn above normal levels. However, during this same period, as water availability increases and the course’s dilution capacity improves, water flow enhances surface water aeration, and NO2 concentrations return to normal levels
Compositional characterisation of urban sediments from Vila Real: environmental implications
No full textRESUMO: No presente estudo procurou-se caracterizar a composição e a textura dos sedimentos urbanos da cidade de Vila Real, através do estudo de lâminas delgadas polidas e superfícies polidas dos sedimentos por microscópia óptica, difração de raios-X e microscopia eletrónica. Os sedimentos urbanos são constituídos, essencialmente, por quartzo, feldspatos (microclina e plagioclase), micas (moscovite e biotite) e, mais raramente, clorite e turmalina. Nas amostras foram ainda identificados minerais opacos/fases opacas, hidróxidos de ferro, fragmentos de cimento/betão, restos de plantas, plásticos e fibras de relva sintética. A análise das fases opacas por microscopia eletrónica indica a ocorrência, entre outras, de partículas
de borracha derivada dos pneus automóveis, ligas de Al-Si com Fe, ferro fundido, ferro fundido nodular, cimento e poeiras ferruginosas derivadas da oxidação de superfícies metálicas. Estas fases resultam da abrasão e desgaste de componentes automóveis e da alteração e erosão de estruturas dos edifícios, constituindo uma componente antrópica significativa na
composição dos sedimentos urbanos.ABSTRACT: This study presents a characterisation of the composition and texture of urban sediments from the city of Vila Real (Northern Portugal), through the study of polished thin sections and polished grain mounts by optical microscopy, X-ray diffraction and electron microscopy. The urban sediments consist of quartz, feldspars, micas and, rarely, chlorite and tourmaline, but they also contain opaque minerals/phases, iron hydroxides, fragments of cement/concrete, plant remains, plastics and synthetic grass fibers. The analysis of opaque phases by electron microscopy indicates the occurrence of rubber particles, derived from automobile tires, Al-Si alloys with Fe, cast iron, nodular cast iron, cement and rust-derived dust from oxidation of metal surfaces. These phases result from the abrasion and wear of automobile components and the weathering and erosion of building structures, constituting a significant anthropogenic component in the composition of urban sediments
Kinematics monitoring of a landslide using a total station and an inclinometric system: the case of Maia (Santa Maria Island, Azores)
No full textRESUMO: Em março de 2010, um deslizamento do tipo rotacional com 18.500 m2 causou vários danos na Maia (ilha de Santa Maria). De forma a avaliar o comportamento cinemático e a geometria da massa instável, foi arquitetada e implementada uma rede de monitorização inclinométrica e uma rede de monitorização geodésica permanente. Os resultados da rede geodésica demonstram um padrão de deformação espacial heterogéneo da massa instável. O deslocamento planimétrico e altimétrico é maior na zona do pé do depósito, próximo da linha de costa, com deslocamentos máximos acumulados desde 2012 de 0,054 m e 0,012 m, respetivamente. A superfície de rotura localiza-se entre 18,0 m e 18,5 m de profundidade no furo de sondagem FSM1 e entre 15,5 m e 16,0 m no furo de sondagem FSM2. O deslocamento máximo acumulado em profundidade é de 0,019 m e 0,020 m no local dos furos FSM1 e FSM2, respetivamente.ABSTRACT: In March 2010, a landslide with 18,500 m2 caused several damages at Maia (Santa Maria Island). In order to evaluate the kinematic behaviour and the geometry of the unstable mass, it was architected and implemented a permanent geodetic and inclinometric monitoring network. The results of the geodetic network demonstrates a heterogeneous spatial deformation pattern in the unstable mass. The planimetric and altimetric displacement is highest at the toe of the deposit, close to the shoreline, with maximum accumulated displacement since 2012 of 0.054 m and 0.012 m, respectively. The failure surface is located between 18.0 m and 18.5 m in
depth in the FSM1 borehole and between 15.5 m and 16.0 m in the FSM2 borehole. The maximum accumulated displacement in depth is 0.019 m and 0.020 m in the FSM1 and FSM2 boreholes, respectively
Padrões de distribuição sedimentar na costa sotavento Algarvia, Portugal
No full textABSTRACT: Sediment grain size gives important information on the origin and evolution of coastal sedimentary environments. This work reports the sediment grain size spatial distribution longshore and cross-shore the Southeastern Algarve coastal area, assessed through the analyses of 395 samples collected in 133 profiles, positioned along a 55 km continuous sector, from Ancão peninsula to Vila Real de Santo António. The results are presented as the mean value of grain size and were clustered into the normalized classes of the Wentworth grain-size scale. The preliminary analysis reveals that the very fine and fine sand clusters are absent for the entire transect, even at the dune area, where the smallest average grain size is within the range of medium sand in the eastern sector and coarse sand at the western edge. General trends in the spatial distribution of sediments exhibit a distinctive variation resulting from the exposure to forcing agents along the study area.RESUMO: A granulometria dos sedimentos fornece indicações importantes sobre a origem e evolução dos ambientes sedimentares da zona costeira. Este trabalho apresenta a distribuição espacial da granulometria dos sedimentos no sotavento algarvio, resultante da análise de 395 amostras recolhidas em 133 perfis posicionados ao longo de uma faixa de 55 km, desde a península do Ancão até Vila Real de Santo António. A análise preliminar dos resultados, apresentados em função do valor da
média e agrupados nas classes normalizadas da escala de tamanho de grão (classificação de Wentworth), revela a ausência das classes granulométricas de areia muito fina e fina, mesmo na zona dunar, onde a classe de areia média domina no sector leste, e a de areia grosseira, no sector ocidental. O padrão geral de distribuição espacial da granulometria dos sedimentos exibe uma variação distinta ao longo da área de estudo, decorrente da exposição aos principais agentes forçadores
Thermoelectric Properties of Tetrahedrites Produced from Mixtures of Natural and Synthetic Materials
No full textABSTRACT: Thermoelectric materials have considerable potential in the mitigation of the global energy crisis, through their ability to convert heat into electricity. This study aims to valorize natural resources, and potentially reduce production costs, by incorporating tetrahedrite-tennantite (td) ores from the Portuguese Iberian Pyrite Belt into synthetic samples. The ore samples were collected in a mine waste at Barrig & atilde;o and as "dirty-copper" pockets of ore from the Neves Corvo mine. Subsequently, high-energy ball milling and hot pressing were employed in the production of thermoelectric materials. These are characterized by XRD, SEM/EDS, and thermoelectrical properties. The complete dissolution of the dump material sulfides with the synthetic tetrahedrite constituents led to an increase in the amount of the tetrahedrite-tennantite phase, which was made up of a tetrahedrite-tennantite-(Fe) solid solution. The thermoelectric characterization of these materials is provided, revealing that most of the combined synthetic ore samples displayed better results than the pristine tetrahedrite, mostly due to higher Seebeck coefficient values. Furthermore, the best thermoelectric performance is achieved with 10% of ore, where a power factor of 268 mu W.K-2.m-1 is reached at room temperature
Detailed in-depth mapping of the world largest anorthositic complex: Magnetic anomalies, 2.5-3D modelling and emplacement constraints of the Kunene Complex (KC), SW Angola
No full textABSTRACT: The Kunene Complex (KC) represents a very large Mesoproterozoic igneous body, mainly composed of anorthosites and gabbroic rocks that extends from SW Angola to NW Namibia (outcropping 18,000 km2 , NE-SW trend, and ca. 350 km long and up to 50 km wide). Little is known about its structure at depth. Here, we use recently acquired aerogeophysical data to accurately determine its hidden extent and to unravel its morphology at depth. These data have been interpreted and modelled to investigate the unexposed KC boundaries, reconstructing the upper crustal structure (between 0 and 15 km depth) overlain by the thin sedimentary cover of the Kalahari Basin. The modelling reveals that the KC was emplaced in the upper crust and extends in depth up to ca. 5 km, showing a lobular geometry and following a large NE-SW to NNE-SSW linear trend, presumably inherited from older Paleoproterozoic structures. The lateral continuation of the KC to the east (between 50 and 125 km) beneath the Kalahari Cenozoic sediments suggests an overall size three times the outcropping dimension (about 53,500 km2 ). This affirmation clearly reinforces the economic potential of this massif, related to the prospecting of raw materials and certain types of economic mineralization (Fe-Ti oxides, metallic sulphides or platinum group minerals). Up to 11 lobes have been isolated with dimensions ranging from 135.5 to 37.3 km in length and 81.9 to 20.7 km in width according to remanent bodies revealed by TMI mapping. A total volume of 65,184 km3 was calculated only for the magnetically remanent bodies of the KC. A long-lasting complex contractional regime, where large strike-slip fault systems were involved, occurred in three kinematic pulses potentially related to a change of velocity or convergence angle acting on previous Paleoproterozoic inherited sutures. The coalescent magmatic pulses can be recognized by means of magnetic anomalies, age of the bodies as well as the lineations inferred in this work: (i) Emplacement of the eastern mafic bodies and granites in a stage of significant lateral extension in a transtensional context between 1500 Ma and 1420 Ma; (ii) Migration of the mantle derived magmas westwards with deformation in a complex contractional setting with shearing structures involving western KC bodies and basement from 1415 Ma to 1340 Ma; (iii) NNW-SSE extensional structures are relocated westwards, involving mantle magmas, negative flower structures and depression that led to the formation of late Mesoproterozoic basins from 1325 Ma to 1170 Ma. Additionally, we detect several first and second order structures to place the structuring of the KC in a craton-scale context in relation to the crustal structures detected in NW Namibia. (c) 2025 China University of Geosciences (Beijing) and Peking University. Published by Elsevier B.V. on behalf of China University of Geosciences (Beijing)