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Associated with the exploitation of metallic minerals in Europe during the 20th century, several mining areas were abandoned without adequate environmental intervention. Furthermore, these areas lack studies to characterize the impact of pollution on the hydrogeological system. The area surrounding the tungsten mine of Regoufe, in northern Portugal, is one such area exploited during the Second World War. The accumulation of sulfide-rich tailings may have caused an acid mine drainage (AMD), where the leaching processes caused by seepage water led to soil contamination, evidenced by its acid character and anomalous concentrations of some Potentially Toxic Elements (PTE) reported in previous studies. The present research proposes an innovative approach that seeks the integration of different geophysical techniques to characterize the impact of mining activity on the subsurface. Electrical resistivity (ER) and electromagnetic (EM) were used to measure subsurface electrical properties. In addition, seismic refraction and Multichannel Analysis of Surface Waves (MASW) were performed to characterize the geometry, depth, and geomechanical behavior of the soil and rock bodies. The integration of these techniques allowed the interpretation of hydrogeological sections and a 3D resistivity volume to gain insight into the distribution of potentially contaminating fluids and tailings material present in the mining valley.

Coal mining can generate organic and inorganic contaminants that can be disseminated in the surrounding soils by leaching and/or aerial deposition. This study aims to identify and characterize the physicochemical and geochemical changes promoted in soils from the surrounding area of a self-burning waste pile in an abandoned coal mine. A soil sampling campaign was conducted bordering the waste pile, comprising the main drainage areas as well as the areas uphill. The soils were characterized geochemically for major and trace elements and multivariate statistics was used in combination with geostatistical methodologies to study the statistical and spatial relations of the different elements and infer their Potentially Toxic Elements (PTEs) sources. The 16 priority Polycyclic Aromatic Hydrocarbons (PAHs) were identified and quantified in soils according to their spatial distribution, and their pyrogenic/petrogenic sources were inferred. Different sources were identified as contributing to the soil geochemical signature, considering not only the mine but also anthropogenic urban contamination or naturally enhanced regional geochemical background in multiple PTEs. PAHs tend to concentrate downstream of the waste pile, along the runoff areas, presenting a greater variety of the 16 priority PAHs and an increase of High Molecular Weight (HMW) PAHs pointing to its pyrogenic origin, possibly related to the self-combustion phenomenon occurring in the waste pile.

Mountains are universally regarded as key sources of high-quality water resources, fundamental for the local populations as well as for communities living downstream. In recent years, global awareness has been growing among citizens, as well as public and private institutions concerning the need to protect mountain water resources. Many mountain catchments are usually situated in regions of low population density, which are the object of special nature protection status. Water pollution in these regions is often related to road de-icing operations. The objective of this research is to recognise and characterise the environmental implications of water pollution due to road de‐icing in a mountain-protected area (Serra da Estrela, Central Portugal) by means of a geoethical perspective encompassing hydrological and ecological processes along with socioeconomic conditions. A geoethically supported decision-making on road de-icing in Serra da Estrela should bear in mind the local hydrosocial cycle, that is to say, the decision-making should be aware of the complex and dialectic interactions between water flow and quality and the socioeconomic dynamics. Costs and benefits of alternative road de-icing techniques should also be assessed, including the impacts on ecological values. This approach encompasses the ability of the territory to produce fundamental ecosystem services, including hydrological services.

The investigation about wildfires has demonstrated that research should include studies on the overall assessment of the processes, thus promoting the public awareness about impacts. The aim of this study is to assess the changes on the carbon content of soils affected by wildfires in Caramulo Mountain (Portugal) to therefore identify the environmental impacts arisen from those changes. Soils from different parent rocks, affected and non-affected by wildfires, were collected. Petrographic and geochemical methods were used to identify changes caused by the wildfires in the organic fraction of soils. The results demonstrate that changes in soils composition after wildfires include the production of charcoal and pyrogenic polycyclic aromatic hydrocarbons (PAH). The incorporation of charcoal from biomass burning in soils overtime and the production of pyrolytic PAH are of environmental concern since these compounds are known to be harmful to the environment and ecosystems and are human carcinogens. The concentration of BkF-benzo[k]fluoranthene, known as probable human carcinogen, exceeds the reference values for contaminated soils. Once in soils these compounds can be removed by percolation affecting waters and, consequently, biodiversity and human health. This work was developed under the ICT (project UIDB/04683/2020) with the reference POCI-01-0145-FEDER-007690. info:eu-repo/semantics/publishedVersion

The target of this study was the tungsten Regoufe mine, whose exploitation stopped in the 1970s. When the mine closed, an unacceptable legacy constituted of mining waste tailings and the ruins of infrastructure was left behind. This work assessed the soil, plants, and water contamination in the mining area; namely their content in potentially toxic elements (PTEs). The global impact of PTEs in the Regoufe mine surface soil points to a very high to ultrahigh degree of contamination of the area having a serious ecological risk level, mainly related to As and Cd contributions. However, establishing the direct relation between As contamination and the anthropogenic effects caused by the mining process cannot be carried out in a straightforward manner, since the soils were already enriched in metals and metalloids as a result of the geological processes that gave origin to the mineral deposits. The studies performed on the plants revealed that the PTE levels in the plants were lower than in the soil, but site-specific soil concentrations in As and Pb positively influence bioaccumulation in plants. The magnetic studies showed the presence of magnetic technogenic particles concentrated in the magnetic fraction, in the form of magnetic spherules. The magnetic technogenic particles probably result from temperature increases induced by some technological process related to ore processing/mining activity. The PTEs in the surface and groundwater samples were similar and relatively low, being unlikely to pose potential health and environmental risks. Arsenic (As) constituted the exception, with levels above reference for drinking water purposes.

Two water effluents that drain from the abandoned coal mine of São Pedro da Cova (NW Portugal) were characterized in terms of their physic-chemical properties and suitability for irrigation purposes. Samples were also collected in a local surface stream, upstream and downstream from the mine drainage points, also used for irrigation by local farmers. Water samples were analyzed for major and minor ions and for trace element concentrations. Sampling campaigns started in 2017 and ended in 2019 and there were 46 water quality parameters tested. There were also proposed all-inclusive indices (the Water Quality Index and the Contamination Index, and also the Trace Element Toxicity Index) based on specific groups of 18 and 17 physic-chemical parameters, respectively, to achieve adequate monitoring requirements for mine effluents and surface water from coalfield. From the physical and chemical aspects of mine water it is inferred that the mine is not producing acid mine drainage. The coal mine water is of medium to high salinity, having almost neutral pH and a high thermal stability during the year, which is a distinguishing feature of the effluents. When compared to international irrigation water quality standards, as Food and Agriculture Organization of the United Nations admissible concentrations, the impacted waters are unsuitable for irrigation. The major outliers to the guidelines were iron, manganese, potassium, magnesium and bicarbonates, being also detected carcinogenic polycyclic aromatic hydrocarbons. Cost-effective ways of monitoring water quality parameters are needed to help control and manage the impact of coal mine effluents that should be treated before releasing into a ditch system that could be then used by local farmers to irrigate their crops.

The São Pedro da Cova waste pile (Porto, Portugal) is composed of coal mining residues that have been self-burning since 2005 and is located close to an inhabited area and social infrastructures, further adding to effects on the environment and human health. Therefore, there is a great interest in the environmental monitoring of this waste pile. This work describes an integrative multi-approach that allows the environmental monitoring of several parameters of the waste pile, applying several technologies. The temperature measurements were obtained by a thermal infrared (TIR) sensor on board an unmanned aerial vehicle (UAV) and supplemented with field measurements. In order to evaluate the altimetric variations, for each flight, a digital elevation model (DEM) was generated considering a multispectral sensor also on board the UAV. The hydrogeochemical characterization was performed through the analysis of groundwater and surface water samples, with and without the influence of mine drainage. The soil monitoring included the analysis of waste material as well as the surface soil in the surrounding area of the waste pile. All the data were analyzed and integrated in a geographical information system (GIS) open-source application. The adopted multi-approach methodology, given its intrinsic interdisciplinary character, has proven to be an effective way of encompassing the complexity of this type of environmental problem.

Groundwater is one of the most important natural resources in daily life. Geographical Information Systems (GIS)-based methods are commonly used to estimate groundwater vulnerability. There are several methods commonly used to estimate the groundwater vulnerability to pollution. DRASTIC is one of the methods most widely used. Several studies used GIS software to assess the groundwater vulnerability due to its easiness and simplicity to manipulate the spatial information. However, nowadays, with the evolution of web GIS applications, some methods start to be implemented in web mapping services in several research areas. Given the main interest in the assessment and study of the aquifer vulnerability, the main objective of this work was to present a new, simple, and intuitive web GIS application, DRASTIC Web GIS, based on the client-server model, that incorporates the DRASTIC index methodology to assess the groundwater vulnerability to pollution. The web GIS incorporates the input and parameters fields to obtain all the maps involved in the DRASTIC index methodology. DRASTIC Web GIS allows the user to view and interact at each step of creating the DRASTIC index map, also allowing to view and interact with the resulting map for each variable. It is free and open-source and it will be accessible to any user in the world.

A study based on geochemical and environmental isotope data was performed in two low-temperature hydrothermal systems in NW Portugal (Caldelas and Geres hydrothermal systems). This study aims to demonstrate the role of integrated hydrogeological tools for developing conceptual models of groundwater circulation. The studied hydrothermal systems are ascribed to groundwater circulation in fractured calc-alkaline/alkaline granitic contexts, responsible for different groundwater geochemical types. Caldelas hydrothermal system is dominated by Ca/Na-HCO3 waters, while at Geres, the hydrothermal system is characterized by Na-HCO3-type waters. The isotopic signatures indicate that the preferential recharge areas are located at very different altitudes (Caldelas around 171 m a.s.l. and Geres between 912 and 1118 m a.s.l.). The thermomineral waters issue with a mean temperature of 27 °C (Caldelas) and 43 °C (Geres). Several geothermometers were used to estimate the reservoir temperature and the corresponding depth reached by the hydrothermal systems. At Caldelas, the mean estimated reservoir temperature was 42 ± 6 °C, using only the chalcedony and K2/Mg geothermometers, which suggests depths around 0.93 km. In the Geres thermal area, the chalcedony, K2/Mg, and Na/K/Ca (β = 4/3) geothermometers gave a mean estimated reservoir temperature of 96 ± 5 °C, suggesting depths close to 2.8 km. In both case studies, conceptual circulation models are proposed, based on: geological heterogeneities, geochemical and isotopic signatures, mean preferential recharge altitudes, groundwater circulation paths, and mean residence time.

Groundwater data from 15 springs at Serra da Estrela mountain, located at the Seia-Torre-Covilha sector, were collected between 2010 and 2011 along six fieldwork campaigns. Isotopic (2H; 18O, and 3H) and chemical determinations were performed. The data were compared with the isotopic and chemical composition of seven alpine ponds located within the same area. The local meteoric water line (δ2H = 6.58(±0.29) + 1.31(±1.23)) was calculated using groundwater isotopic data. The results show that the springs located at the highest altitudes are more depleted than those located downhill. A slightly different isotopic fractionation with altitude was found between the western and eastern slopes of Serra da Estrela Natural Park (0.12 ‰ versus 0.10 ‰ /100 m in δ18O, respectively). The groundwaters are hyposaline, mainly Cl-Na-type waters, with slightly acidic pH reflecting a shallow and short flow path and small residence time. The alpine ponds also show Cl-Na facies and are mainly recharged by direct precipitation. However, in two alpine ponds (L2 and L6), evidences for groundwater recharge were identified. The physical, chemical, and isotopic composition allowed the identification of: (i) contribution of de-icing into the groundwater and alpine ponds systems; (ii) contribution of the shallow groundwater flow toward the alpine ponds systems recharge.

The investigation about wildfires has demonstrated that research should include studies on the overall assessment of the processes, thus promoting the public awareness about impacts. The aim of this study is to assess the changes on the carbon content of soils affected by wildfires in Caramulo Mountain (Portugal) to therefore identify the environmental impacts arisen from those changes. Soils from different parent rocks, affected and non-affected by wildfires, were collected. Petrographic and geochemical methods were used to identify changes caused by the wildfires in the organic fraction of soils. The results demonstrate that changes in soils composition after wildfires include the production of charcoal and pyrogenic polycyclic aromatic hydrocarbons (PAH). The incorporation of charcoal from biomass burning in soils overtime and the production of pyrolytic PAH are of environmental concern since these compounds are known to be harmful to the environment and ecosystems and are human carcinogens. The concentration of BkF-benzo[k]fluoranthene, known as probable human carcinogen, exceeds the reference values for contaminated soils. Once in soils these compounds can be removed by percolation affecting waters and, consequently, biodiversity and human health.

Peri-urban areas are territories that combine urban and rural features, being particularly vulnerable to wildfire due to the contact between human infrastructures and dense vegetation. Wildfires may cause considerable direct and indirect effects on the local water cycle, but the influence on groundwater quality is still poorly understood. The aim of this study was to characterize the chemistry of several springs connected to small public supply systems in a peri-urban area, following a large wildfire that took place in October 2017. Groundwater samples were collected in four springs that emerged within burned forests, while control samples were from one spring located in an unburned area. Sampling took place from October 2017 until September 2018, starting 15 days after the wildfire occurrence, to evaluate the influence of the time after fire and the effect of precipitation events on groundwater composition. Groundwater samples collected in burned areas presented increased content of sulfate, fluoride and nitrogen and variability in pH values. Iron, manganese and chromium contents also increased during the sampling period. Post-fire concentrations of polycyclic aromatic hydrocarbons (PAHs), mainly the carcinogenic ones, increased especially after intense winter and spring rain events, but the levels did not exceed the guideline values for drinking water.

Water resources in mountain regions are at risk due to demographic and economic growth and climate change. This paper presents an evaluation of the impacts of climate change on the groundwater resources of Serra da Estrela Mountain (Portugal). The changes in the water resources in the last 30 years of the twenty-first century have been evaluated with respect to the hydrometeorological conditions of the control period 1975–2005. The predictions for the period 2069–2099 were made by using the Representative Concentration Pathways RCP4.5 and RCP8.5, which are two climate scenarios of the EURO-CORDEX project. The climate scenarios RCP4.5 and RCP8.5 cover a reasonably wide range of possible future trends. The impacts of the climate change have been assessed by using the simulated daily temperature and precipitation values from the climatic models and by solving the daily hydrological water balance model with the code VISUAL-BALAN. The mean annual temperature for the RCP4.5 and RCP8.5 scenarios will increase 3.1 and 5.4 °C, respectively. The increase of temperature in the winter will reduce snow precipitation and favor the melting of the snow cover in the highest sub-basins. The mean annual precipitation will decrease from 8% (RCP4.5 scenario) to 15% (RCP8.5 scenario). The mean annual snow precipitation will decrease drastically from 54 to 84%. The mean interflow and aquifer recharge will decrease from 12 to 22%. The mean streamflow will decrease from 10 to 18%. The largest decrease in monthly streamflows will occur from March to May due to the decrease of rainfall and snow precipitation. Monthly streamflows during the snow melting season will decrease from 37 to 45%. It can be concluded that the water resources in the Serra da Estrela mountain basin will be very vulnerable to the predicted changes in precipitation and temperature.

The importance of Mountains for the world's water supply has been increasingly recognized. However, in many cases the existing roads require regular de-icing operations which may have a severe impact on the natural hydrogeochemical conditions of the local hydrological systems due to the regular use of substances such as sodium chloride and calcium chloride. The Serra da Estrela Mountain is a strategic area for the water resources management in Portugal because of its geological, geomorphological and climatic framework. This study was carried out in the highest part of the mountain, where road de-icing is frequent during winter. The hydrogeochemical characteristics of several springs, located downstream from roads between 1500 m a.s.l. and 1990 m a.s.l., present clear anthropic signatures which disturbs the quality of the local water resources.

Groundwater is a crucial natural resource for regular socio-economic function. Groundwater vulnerability to pollution can be assessed through Geographical Information System (GIS)-based qualitative methods. GIS-based tools, dedicated to the assessment of groundwater vulnerability, usually present several limitations, such as high cost, unavailable code, and a lack of functionality concerning the flexible application of vulnerability indices and vulnerability map comparison. The objective of this work was to create a new GIS-based open source application for groundwater vulnerability assessment, GVTool, developed using QGIS software, with the capability of creating and comparing groundwater vulnerability maps considering four different methods: DRASTIC, GOD, SINTACS, and Susceptibility Index (SI). This application incorporates features from a previous tool, DRASTIC Model, and new functionalities were included, namely three additional vulnerability assessment methods, map comparative analysis, map statistics, and index interval reclassification and symbology definition. The GVTool functionalities and capabilities are illustrated through a groundwater vulnerability assessment in Serra da Estrela mountain (Central Portugal). GVTool is mostly useful in integrated assessments, helping to verify if the groundwater vulnerability maps are accurate and to decide which is the most suitable method or the combination of methods to express groundwater vulnerability to pollution in a specific area.

Interflow is the shallow sub-horizontal water flow through the saturated/unsaturated zone generally of a short transit time. It is the main component of the water balance in mountain regions. The study of interflow requires the development of appropriate conceptual models. Its quantification involves challenges due to: (1) the lack of methods to detect and measure it; (2) the possibility of mistaking interflow with local short-time groundwater flow. Therefore, the estimation of interflow is subjected to uncertainties, which in turn lead to errors in the evaluation of other hydrological components. A physically based semi-empirical model of interflow is presented here. It has been implemented in the water balance codes VISUAL-BALAN and GIS-BALAN and tested in three Iberian mountain basins: (1) the Valinas river basin in the NW of Spain; (2) the Bernesga basin in the North of Spain; and (3) the Zezere river basin at the Serra da Estrela in central Portugal. Model results show that the mean annual interflow in these mountain basins ranges from 34 to 55 % of the annual precipitation. These basins share the following features, which favour interflow: steep slopes and low-permeability layers in the soil. It can be concluded from this study that the evaluation of groundwater resources in mountain basins requires the proper estimation of interflow.

Mountains are often considered as the world’s water towers. This paper presents a critical review on the research concerning the integrated assessment of groundwater resources of the mountain hydrogeologic system of Serra da Estrela Natural Park (central Portugal). The study area is the Zezere river basin upstream of Manteigas village located at the Serra da Estrela Mountain in Central Portugal. It provides the source of strategic water resources for the Portuguese mainland, including normal groundwaters, thermomineral waters and surface waters. An integrated approach has been used to formulate a conceptual model for this complex mountain hydrogeological system by integrating the geological, morphotectonic, hydroclimatic, unsaturated soil zone, hydrogeological, hydrogeophysical, hydrogeochemical and isotopic data. This model has been useful to: i) evaluate the water resources; ii) provide the basis for a sustainable management of water resources, iii) design measures for groundwater exploitation and contamination control; and iv) set up land-use policies.

Hard-rock catchments are considered to be source of valuable water resources for water supply to inhabitants and ecosystems. The present work aims to develop a groundwater vulnerability approach in the Caldas da Cavaca hydromineral system (Aguiar da Beira, Central Portugal) in order to improve the hydrogeological conceptual site model. Different types of information were overlaid, generating several thematic maps to achieve an integrated framework of key sectors in the study site. Thus, a multi-technical approach was used, encompassing field and laboratory techniques, whereby different types of data were collected from fields such as geology, hydrogeology, applied geomorphology and geophysics and hydrogeomechanics, with the fundamental aim of applying the so-called DISCO index method. All of these techniques were successfully performed and an intrinsic groundwater vulnerability to contamination assessment, based on the multicriteria methodology of GOD-S, DRASTIC-Fm, SINTACS, SI and DISCO indexes, was delineated. Geographic Information Systems (GIS) provided the basis on which to organize and integrate the databases and to produce all the thematic maps. This multi-technical approach highlights the importance of groundwater vulnerability to contamination mapping as a tool to support hydrogeological conceptualization, contributing to improving the decision-making process regarding water resources management and sustainability.

The aim of this paper is to review the results of the assessment of low-temperature geothermal resources (issue temperatures between 41 and 77 °C) that occur in the Portuguese mainland. For this purpose, a multidisciplinary approach, including geologic, tectonic, geochemical, geophysical and isotopic (δ2H, δ18O, δ13C, 3H and 14C) techniques, was applied in order to update local and/or regional conceptual circulation models. Three case studies of N-Portugal are presented and discussed. This paper describes different low-temperature geothermal waters presenting similar hydrogeological conceptual models but rather different geochemical signatures (e.g., HCO3-Na with pH ≈ 8, HCO3/Na/CO2-rich with pH ≈ 7 and HCO3-Na with pH ≈ 9, type waters). In fact, in the studied low-temperature geothermal systems, local/regional high altitude sites associated with highly fractured rocks play an important role in conducting the infiltrated meteoric waters towards the discharge zones near the Spas. The discharge zones are mainly related to the intersection of major regional fault lineaments (and conjugate structures), responsible for creating the mineral waters ascent. In some cases, geochemical and isotopic data point out to the existence of anthropogenic contamination of some geothermal spring waters related to the intense use of fertilizers in areas of widespread agricultural practices.

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. Zezere 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 δ18O 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 Zezere River valley.

The assessment of contaminant dispersion in Controlled Dumps (CD) of Municipal Solid Waste (MSW) is possible through the combination of geophysical, geochemical and statistical methods. The methodology applied in this study will contribute to evaluate the environmental consequences of the Matosinhos CD (N Portugal), which is set in a granitic crystalline geological context with a permeability controlled by differential weathering which, in turn, is associated with fracturing. The statistical methods that we will describe are usually used in geochemical anomaly determination and were adapted to be used with resistivity data obtained from twenty-two 2D profiles performed around the CD. The data set was inverted and the results were processed and visualized by a 3D software application that we are currently developing. Groundwater samples were also collected in piezometers, upstream and downstream of the CD, with the aim of directly confirming the presence of contaminants indirectly detected by the geophysical and geostatistical methods described before. The combination of these different approaches allows, in our opinion, an improved approach towards the detection and delineation of contaminant plumes from these deposits.

Mountains are often recognized as the "world's water towers", due to their exceptional ability to generate water resources or good quality and. frequently, or considerable economic value (e.g. UNESCO IHP-VI Programme: http://www,unesco.org, Aureli 2002).