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Publications

Publications by CRAS

2022

PRELIMINARY RESULTS OF ELECTRICAL RESISTIVITY FOR SUBSOIL ENVIRONMENTAL ASSESSMENT OF THE ALIJÓ LITHIUM RICH PEGMATITE QUARRY, BARROSO, PORTUGAL

Authors
Marques M.C.; Moura R.; Lima A.; Patinha C.;

Publication
International Multidisciplinary Scientific GeoConference Surveying Geology and Mining Ecology Management, SGEM

Abstract
In recent years, with the rise of a growing economic and technological interest in lithium mineral resources, there has been a parallel concern, on the part of some local populations and even national environmental groups, for a hypothetical contamination problem that this type of exploitations may cause on the quality of groundwater. Thus, the present study was based on an evaluation of an open-pit quarry, in the so-called Alijó quarry, located in the North of Portugal, in the parish of Canedo, Ribeira de Pena municipality and Vila Real district. This exploitation, under concession by the company José Aldeia Lagoa & Filhos, SA, has been going on for at least 11 years and mainly supplies the ceramic and glass industry. It is in this context that this work is carried out. The general objectives are to assess signs of impacts that extractive activities, carried out in the open-pit exploitation area of Alijó, may have caused on the surrounding subsoil. In this sense, it was necessary to consider the aforementioned hypothesis of the existence of possible sources of water drainage with ionic anomalies for the surrounding environment. If this hypothesis were confirmed, then the level of underground conductivity would have to be proportionally high and obtainable through equivalent low values of electrical resistivity (high electrical conductivity). The current study was limited to geophysical tools along with a few chemical analysis of water samples collected in the open-pit exploration for control purposes. The signs we sought for could possibly be manifested in the form of anomalous concentrations of some of the elements of the mineralization of this lithiniferous pegmatite and whose effects could, hypothetically, be measured in the form of anomalous low values of underground electrical resistivity, as well as anomalous pH valuespresent in the drainage water. To this end, a study mainly supported by the electrical resistivity method was carried out. This method is based on the measurement of electrical resistivity variations of different subsoil geological materials, since rocks and soils, depending on their mineralogical composition, texture, porosity, fracturing and the content/chemical composition of the water contained in them, could exhibit anomalous, low electrical resistivity. The results revealed that no low resistivity values were found, typical of areas that normally exhibit natural or anthropogenic geochemical anomalies, or even, in more extreme cases, contaminations with acid drainages whose acidity and resistivity would be even lower and more anomalous.

2022

GEOPHYSICAL EXPLORATION OF ANTIMONY MINERALIZATIONS: ALTO DO SOBRIDO AND RIBEIRO DA SERRA MINES (PORTUGAL)

Authors
Carvalho A.; Ribeiro R.; Moura R.; Lima A.;

Publication
International Multidisciplinary Scientific GeoConference Surveying Geology and Mining Ecology Management, SGEM

Abstract
The Alto do Sobrido and Ribeiro da Serra Mines, are two antimony-gold mines located in Gondomar, Portugal, and are part of the Dúrico-Beirão Mining District (DBMD). In this work, we use four geophysical methods, such as gravity, radiometry, magnetic and electromagnetic, to improve the knowledge about these mineralizations and the lithologies and structures associated with them. These four methods allowed us to study these mineralizations through different physical properties. The gravimetric method allowed us to add more data to the hypothesis that the gold-antimony mineralizations of the DBMD could be genetically associated with a non-outcropping granite intrusion, which functioned either as a heat engine that promoted the circulation of fluids and/or as a source of fluids and metals itself. A 2D model was proposed, created with both modelling and inversion, to show that the presence of this granite could indeed fit the response of the negative anomalies found in the residual anomaly. The radiometric method was used mainly as a mapping tool, where we were able to distinguish between some of the lithologies of the area, like the Lower Ordovician quartzites and the metasediments of the Middle Ordovician to the Carboniferous, but also to observe different element concentrations within the Pre-Ordovician Schist-Greywacke Complex (SGC). These variations within the SGC lithology don’t have a clear explanation as to why they occur. Still, we believe that they could occur due to the influence of the abovementioned non-outcropping granite. With the very low frequency (VLF) electromagnetic method, it was possible to locate areas of lower resistivities that correspond to the location of several known mineralized veins, as well as the probable location for a new vein. It was also possible to observe some weathered rocks near faults and fractures associated with the Dúrico-Beirão Shear Zone (DBSZ). With the magnetic method, it is possible to contribute to areas with the prevalence of lithologies and minerals with higher magnetic susceptibilities. Several magnetic anomalies found near the Alto do Sobrido mining works correspond to the mineralized veins paragenesis. Other anomalies appear to be related to the location of faults and fractures associated with the DBSZ. The use of all these methods allowed us to observe the mineralization responses and its associated lithologies and structures through the different geophysical properties while adding knowledge about the genesis of these mineralizations and possibly the location of new mineralized veins.

2022

Geophysics and drilling in the tectonic and geological study of the region West of Estarreja [Geofísica e sondagens no estudo tectónico e geológico da região a Oeste de Estarreja]

Authors
Marques, T; Moura, R; Machadinho, A; Matias, M;

Publication
Comunicacoes Geologicas

Abstract
The region West of Estarreja is topographically flat and, from the geological point of view, characterized by Quaternary and Cretaceous formations that lie discordantly over Pre-Cambrian schists. The topography of this contact is poorly known and, therefore, is investigated here. Data from drilling, electrical resistivity profiles and gravity mapping, over a 30 km2 area bounded on the Eastern side by the “Norte” Railway line and on the Western by the Ria de Aveiro that separates Murtosa from Torreira, are jointly interpreted to produce a robust model for the topography of the bedrock. Hence, NW-SE alignments, inferred by previous works, are clearly identified. Bedrock depressions are also proposed and agree with previous geophysical models from areas to the South of the region herein investigated. © 2022 LNEG – Laboratório Nacional de Energia e Geologia IP.

2022

The Challenge of Long-Distance Over-the-Air Wireless Links in the Ocean: A Survey on Water-to-Water and Water-to-Land MIoT Communication

Authors
Dinis, H; Rocha, J; Matos, T; Goncalves, LM; Martins, M;

Publication
APPLIED SCIENCES-BASEL

Abstract
Robust wireless communication networks are a cornerstone of the modern world, allowing data to be transferred quickly and reliably. Establishing such a network at sea, a Maritime Internet of Things (MIoT), would enhance services related to safety and security at sea, environmental protection, and research. However, given the remote and harsh nature of the sea, installing robust wireless communication networks with adequate data rates and low cost is a difficult endeavor. This paper reviews recent MIoT systems developed and deployed by researchers and engineers over the past few years. It contains an analysis of short-range and long-range over-the-air radio-frequency wireless communication protocols and the synergy between these two in the pursuit of an MIoT. The goal of this paper is to serve as a go-to guide for engineers and researchers that need to implement a wireless sensor network at sea. The selection criterion for the papers included in this review was that the implemented wireless communication networks were tested in a real-world scenario.

2022

Underwater Energy Harvesting to Extend Operation Time of Submersible Sensors

Authors
Faria, CL; Martins, MS; Matos, T; Lima, R; Miranda, JM; Goncalves, LM;

Publication
SENSORS

Abstract
A linear electromagnetic energy harvesting device for underwater applications, fabricated with a simple manufacturing process, was developed to operate with movement frequencies from 0.1 to 0.4 Hz. The generator has two coils, and the effect of the combination of the two coils was investigated. The experimental study has shown that the energy capture system was able to supply energy to several ocean sensors, producing 7.77 mJ per second with wave movements at 0.4 Hz. This study shows that this energy is enough to restore the energy used by the battery or the capacitor and continue supplying energy to the sensors used in the experimental work. For an ocean wave frequency of 0.4 Hz, the generator can supply power to 8 sensors or 48 sensors, depending on the energy consumed and its optimization.

2022

Active Neutralizing Mats for Corrosive Chemical Storage

Authors
Fernandes, RDV; Melro, L; Padrao, J; Ribeiro, AI; Mehravani, B; Monteiro, F; Pereira, E; Martins, MS; Dourado, N; Zille, A;

Publication
GELS

Abstract
Laboratories and industries that handle chemicals are ubiquitously prone to leakages. These may occur in storage rooms, cabinets or even in temporary locations, such as workbenches and shelves. A relevant number of these chemicals are corrosive, thus commercial products already exist to prevent material damage and injuries. One strategy consists of the use of absorbing mats, where few display neutralizing properties, and even less a controlled neutralization. Nevertheless, to the authors' knowledge, the commercially available neutralizing mats are solely dedicated to neutralizing acid or alkali solutions, never both. Therefore, this work describes the development and proof of a completely novel concept, where a dual component active mat (DCAM) is able to perform a controlled simultaneous neutralization of acid and alkali leakages by using microencapsulated active components. Moreover, its active components comprise food-grade ingredients, embedded in nonwoven polypropylene. The acid neutralizing mats contain sodium carbonate (Na2CO3) encapsulated in sodium alginate microcapsules (MC-ASC). Alkali neutralizing mats possess commercial encapsulated citric acid in hydrogenated palm oil (MIRCAP CT 85-H). A DCAM encompasses both MC-ASC and MIRCAP CT 85-H and was able to neutralize solutions up to 10% (v/v) of hydrochloric acid (HCl) and sodium hydroxide (NaOH). The efficacy of the neutralization was assessed by direct titration and using pH strip measurement tests to simulate the leakages. Due to the complexity of neutralization efficacy evaluation based solely on pH value, a thorough conductivity study was performed. DCAM reduced the conductivity of HCl and NaOH (1% and 2% (v/v)) in over 70%. The composites were characterized by scanning electron microscopy (SEM), differential calorimetry (DSC) and thermogravimetric analysis (TGA). The size of MC-ASC microcapsules ranged from 2 mu m to 8 mu m. Finally, all mat components displayed thermal stability above 150 degrees C.

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