2012
Authors
Moura, RM; Senos Matias, MJS;
Publication
GEOPHYSICAL PROSPECTING
Abstract
In recent years some authors have given a certain amount of attention to towed seismic reflection acquisition systems. Based on some of these works we sought to design and test a system making use of currently available geophones instead of specifically designed sensors as employed in some previous works. Thus, bearing in mind that the geophone's characteristics are achieved in the conditions that they are originally designed to be employed in, i.e., coupled with a spike driven into the ground, we devoted our attention to some of the variables involved in the geophone's performance, namely the total weight, the effect of a spikeless geophone and the surfaces on which the geophone is placed. Previously, we had experimentally verified some variations in the signal response due to coupling geophones in different surface materials, such as hard soil, asphalt and concrete pavement and we noticed that these surface materials were in fact an important factor in the overall response. Hence, these materials, or as we also called them coupling agents, could be employed as a base material in the construction of a mobile seismic acquisition device composed of blocks of a certain size, on which the geophone would be then inserted and thus making it into a spikeless surface towable system. Therefore, various materials were tested in order to select one that could maintain a similar fidelity to that of the spike coupled geophone and thus contribute towards building a more time efficient and towable geophone and block system. Pinging tests revealed variations in the coupling frequency and damping characteristics of each coupling agent and from all of these tested materials one was selected for field comparative tests with the normally planted geophones with spike coupling. Finally a seismic reflection profile was acquired simultaneously with both systems, i.e., spike coupling versus cement block coupled geophones.
2012
Authors
Goncalves, V; Fontoura, MJ; Dias, P; Moura, R; Santos, BS;
Publication
Proceedings of the International Conference on Information Visualisation
Abstract
Geophysical data represent subsoil structure in a specific area and can be used to extract subsoil information for various purposes. In this work we used this data type to detect anomalies/contamination in the subsoil. Our case study was based on data acquired around a landfill and the main objective is identifying contaminated areas as a result of leakage in landfill. This involves the application of statistical methods to detect anomalous values taking into account the whole data set, subdividing it in sublevels in relation to the surface, instead of using a single threshold (as usual). This work combines in the same software package the anomaly statistical analysis and several 3D representations of the results to validate and also helps understanding the final results of the analysis. Given that the original data used in the analysis, resistivity sections, is normally very sparse, a kriging geostatistical process was used to interpolate data in order to provide a volumetric representation of the subsoil in the area, providing a continuous spatial visualization. © 2012 IEEE.
2011
Authors
Carreira, PM; Marques, JM; Marques, JE; Chamine, HI; Fonseca, PE; Santos, FM; Moura, RM; Carvalho, JM;
Publication
HYDROGEOLOGY JOURNAL
Abstract
In a multidisciplinary approach, geological, geomorphologic, structural, hydrogeochemical and isotopic surveys were conducted on the Serra da Estrela groundwater system (central Portugal) in order to establish/develop a conceptual circulation model of the Caldas de Manteigas thermomineral system. A detailed study of the isotopic and geochemical composition of surface waters (e.g. Zzere River), shallow groundwaters (cold dilute springs), and thermomineral waters was carried out to characterize the distribution of isotopes in waters of this mountainous region, and to determine the origin and possible recharge locations of the thermomineral system. Special attention was dedicated to isotopic tracers and their role in the definition of the thermomineral waters' conceptual model, considering: (1) the delta(18)O fractionation gradient; (2) the mean isotopic composition of the thermomineral waters in the region; and (3) the estimation of snowmelt contribution as a source of groundwater recharge at Serra da Estrela. The recharge of the thermomineral aquifer takes place on the more permeable zones of the granitic massif, associated with the main tectonic structures, whereas the recharge of the shallow aquifers seems to take place mostly in the plateaus, although another part of the recharge may occur in the slopes of the Zzere River valley.
2012
Authors
Carvalho, A; Espinha Marques, J; Marques, JM; Carreira, PM; Moura, R; Guerner Dias, A; Chamine, HI; Rocha, F; Saraiva, R; Tavares, M; Mansilha, C;
Publication
Comunicacoes Geologicas
Abstract
In the present moment, the sustainable water management is a major concern throughout the world. Mountain areas are more and more recognized as the world's water towers (UNESCO IHP-VI PROGRAMME). Since a large number of mountains are located at high altitude and are crossed by roads, deicing operations are inevitable. The use of deicing chemicals such as sodium chloride and calcium chloride to promote snow and ice melting in roads is an environmental problem of scientific, economic and social relevance. Due to its geological, geomorphological and climate characteristics, the Serra da Estrela mountain plays a strategic role in the water management in Portugal. This paper presents hydrogeochemical results that illustrate the process of groundwater contamination by road deicing salts in this mountain area. © 2012 LNEG.
2011
Authors
Fontoura, MJ; Moura, RMM; Dias, AG;
Publication
Comunicacoes Geologicas
Abstract
The main goal of this study is to assess the current environmental state of the Matosinhos Controlled Dump (CD) and its surroundings. Until the end of last century the Matosinhos CD was an open area where all the wastes produced in Matosinhos were deposited. The CD lies in a granitic crystalline geological context with fissure controlled type permeability, which is not common (Mota et al., 2004) in the Portuguese context. With our set of 2D resistivity profiles was possible to detect the presence of two resistivity anomalies indicative of contamination in the Matosinhos CD surrounding, with particular emphasis in the downstream area (unsealed part). The upstream anomaly, with resistivity values lower than 30 O.m, is vertically limited by a more resistive material, a few meters from the northern boundary of the CD. The other one, more extensive, is located in the southern part of the CD, with resistivity values lower than 7 O.m. It was possible to detect that both contamination anomalies were decreasing with the increasing distance of the CD. Comparing the conductivity measurements in water samples collected from upstream piezometers with the values of downstream piezometer the presence of a strong influence of contamination downstream of the CD was found and thus confirmed and correlated with the electrical resistivity data. © 2011 LNEG - Laboratório Nacional de Geologia e Energia, IP.
2011
Authors
Marques Espinha, J; Carvalho, A; Marques, JM; Chamine, HI; Guerner, A; Moura, R; Carreira, P; Neves, O; Samper, J; Rocha, FT;
Publication
Cadernos do Laboratorio Xeoloxico de Laxe
Abstract
Mountain areas are the source of high quality and socioeconomic relevance water resources. The sustainable management of such regions is fundamental to maintain the water supply to populations in wide areas all over the planet. Serra da Estrela is the origin of water resources of strategic importance to Portugal. In the highest part of the mountain, especially above 1400 m a.s.l., the use of road de-icing chemicals (NaCl and, accessorily, CaCl) may affect both groundwater and surface water as well as soils and therefore is a major environmental concern that should be investigated. This article presents a multidisciplinary methodology meant to support the study of water pollution as a result of the use of road de-icing salts in a mountain environment. This methodology encompasses contributions from Hydrogeology, Hydrogeochemistry, Isotope Geochemistry, Hydrogeophysics, GIS supported geological mapping and mathematical modelling. The main purpose of the application of this methodology in Serra da Estrela is to prepare a hydrogeological conceptual model focused in the processes related to groundwater pollution by NaCl from road de-icing. Another objective is to improve the sustainability of water resources and to provide new guidelines for water exploration and exploitation in the region.
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