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  • 1
    Publication Date: 2023-08-29
    Description: Karst hydrosystems represent one of the largest global drinking water resources, but they are extremely vulnerable to pollution. Climate change, high population density, intensive industrial, and agricultural activities are the principal causes of deterioration, both in terms of quality and quantity, of these resources. Samples from 172 natural karst springs were collected in the whole territory of Greece. To identify any geogenic contamination and/or anthropogenic pollution, analyses of their chemical compositions, in terms of major ions and trace elements, were performed and compared to the EU limits for drinking water. Based on chloride content, the collected karst springs were divided into two groups: low-chloride (〈 100 mg L-1) and high-chloride content (〉 100 mg L-1). An additional group of springs with calcium-sulfate composition was recognised. Nitrate concentrations were always below the EU limit (50 mg L-1), although some springs presented elevated concentrations. High contents in terms of trace elements, such as B, Sr, As, and Pb, sometimes exceeding the limits, were rarely found. The Greek karst waters can still be considered a good quality resource both for human consumption and for agriculture. The main issues derive from seawater intrusion in the aquifers along the coasts. Moreover, the main anthropogenic pollutant is nitrate, found in higher concentrations mostly in the same coastal areas where human activities are concentrated. Finally, high levels of potentially harmful trace elements (e.g. As, Se) are very limited and of natural origin (geothermal activity, ore deposits, etc.).
    Description: Published
    Description: 11191
    Description: 6A. Geochimica per l'ambiente e geologia medica
    Description: JCR Journal
    Keywords: Greece ; Hydrogeochemistry ; trace elements ; water quality ; karst springs ; 03.04. Chemical and biological
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Publication Date: 2023-10-26
    Description: Samples of efflorescences and encrustations of hydrothermal origin were collected at Sousaki (Greece) and analysed for their mineralogical (XRD) and chemical composition. Solutions obtained both from mineralization with HNO3 and from leaching with deionised water were analysed for major (ICP-OES), minor and trace metals (ICP-MS) and sulfate contents (IC). Results evidence the dependence of the chemical and mineralogical composition on micro-environmental conditions i.e. humidity, oxygen-rich or -poor environment, exposed or sheltered from meteoric agents. In fact, the presence of highly soluble sulfate minerals with elevated contents of many metals (e.g. Mg, Al, Fe, Mn, Cr, Ni, etc.) further underscores the important influence of hydrothermal activity on elements' mobility, whilst the sometimes very high concentrations in toxic elements like Al, Cr, Ni suggest also possible environmental impacts.
    Description: Published
    Description: 107121
    Description: 6A. Geochimica per l'ambiente e geologia medica
    Description: JCR Journal
    Keywords: Hydrothermal alteration products ; Sulfates ; Toxic metals ; Elements' mobility ; 04. Solid Earth
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Publication Date: 2023-10-26
    Description: Greece belongs to the most geodynamically active regions of the world and as such, it has to be considered an area of intense geogenic degassing. In terms of carbon, the territory is characterized by the high hydrothermal and volcanic activity of the South Aegean Active Volcanic Arc (SAAVA), and by widespread geological seeps of buried carbon dioxide and methane. In the present work, we investigate the island of Gyali located in the volcanic system Kos-Gyali-Nisyros. Nine gas samples have been collected on the island of Gyali in areas found both on land, in a small lake (~2000 m2) along its beach, and in the sea close to the shore at shallow depths (〈20 m). Results show that CO2 is the prevailing gas species with concentrations above 833,000 μmol/mol, whilst minor enrichments in N2 are noticed in some of the samples. Helium isotope ratio suggests an up to 70% mantle origin (considering a MOR type source) with the contribution of the atmospheric component being negligible, whereas C presents a mixed mantle-limestone origin with organic sediment being unimportant. Such isotope values fall in the range that characterizes the Kos-Gyali-Nisyros Volcanic Field. First estimations on the CO2 release suggest an output in the range from 18 to 28 t/d for Gyali Island, which is much lower than the total output of Kos ~75 t/d and Nisyros ~100 t/d. However, such results highlight that Gyali is an active system and, despite its small size, its degassing is not trivial.
    Description: Published
    Description: 16-28
    Description: 6A. Geochimica per l'ambiente e geologia medica
    Description: JCR Journal
    Keywords: flux measurements ; carbon degassing ; SAAVA ; 05.09. Miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
    Publication Date: 2023-01-24
    Description: The concepts of CO2 emission, global warming, climate change, and their environmental impacts are of utmost importance for the understanding and protection of the ecosystems. Among the natural sources of gases into the atmosphere, the contribution of geogenic sources plays a crucial role. However, while subaerial emissions are widely studied, submarine outgassing is not yet well understood. In this study, we review and catalog 122 literature and unpublished data of submarine emissions distributed in ten coastal areas of the Aegean Sea. This catalog includes descriptions of the degassing vents through in situ observations, their chemical and isotopic compositions, and flux estimations. Temperatures and pH data of surface seawaters in four areas affected by submarine degassing are also presented. This overview provides useful information to researchers studying the impact of enhanced seawater CO2 concentrations related either to increasing CO2 levels in the atmosphere or leaking carbon capture and storage systems.
    Description: Published
    Description: 775247
    Description: 6V. Pericolosità vulcanica e contributi alla stima del rischio
    Description: JCR Journal
    Keywords: CO2 emissions ; submarine gas vents ; geogenic degassing ; environmental impac ; Greek Islands ; gas flux
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
    Publication Date: 2023-08-29
    Description: Natural thermal and mineral waters are widely distributed along the Hellenic region and are related to the geodynamic regime of the country. The diverse lithological and tectonic settings they are found in reflect the great variability in their chemical and isotopic composition. The current study presents 276 (published and unpublished) trace element water data and discusses the sources and processes affecting the water by taking into consideration the framework of their geographic distribution. The dataset is divided in groups using temperature- and pH-related criteria. Results yield a wide range of concentrations, often related to the solubility properties of the individual elements and the factors impacting them (i.e. temperature, acidity, redox conditions and salinity). Many elements (e.g. alkalis, Ti, Sr, As and Tl) present a good correlation with temperature, which is in cases impacted by water rock interactions, while others (e.g. Be, Al, Cu, Se, Cd) exhibit either no relation or an inverse correlation with T possibly because they become oversaturated at higher temperatures in solid phases. A moderately constant inverse correlation is noticed for the vast majority of trace elements and pH, whereas no relationship between trace element concentrations and Eh was found. Seawater contamination and water-rock interaction seem to be the main natural processes that influence both salinity and elemental content. All in all, Greek thermomineral waters exceed occasionally the accepted limits representing in such cases serious harm to the environment and probably indirectly (through the water cycle) to human health.
    Description: Published
    Description: 78376–78393
    Description: 6A. Geochimica per l'ambiente e geologia medica
    Description: JCR Journal
    Keywords: Greece ; Hydrogeochemistry ; Mineral waters ; Natural contaminants ; Trace elements ; Water-rock interaction ; Thermal waters ; 03.04. Chemical and biological
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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