Geochemical Characterization of Geothermal Systems: Multidisciplinary Approaches to Define Source Processes, Evolution and Environmental Issues

A special issue of Geosciences (ISSN 2076-3263). This special issue belongs to the section "Geochemistry".

Deadline for manuscript submissions: closed (25 July 2022) | Viewed by 15611

Special Issue Editors


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Guest Editor
Department of Earth Sciences, University of Calabria, Rende, Italy
Interests: origin and evolution of fluids in geothermal areas; water geochemistry; isotopic geochemistry; environmental geochemistry; geothermobarometry; water-rock interaction; coastal management
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Guest Editor
Institute of Polar Sciences, Italian National Research Council (CNR-ISP), Venice-Mestre, Italy
Interests: water chemistry; atmospheric pollution; environmental analytical chemistry; mercury (Hg); trace and toxic elements

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Guest Editor
Department of Biology, Ecology and Earth Sciences (DiBEST), University of Calabria (UNICAL), Via P. Bucci, 15B-87036 Arcavacata di Rende(CS), Italy
Interests: environmental geochemistry; origin and evolution of fluids in geothermal areas; isotopic geochemistry; water–rock interaction
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The main scope of this Special Issue of Geosciences is the exploration and evaluation of both innovative and long-validated approaches to the geochemical characterization of geothermal areas.

Drilling is the only direct method to access the subsurface features of a given system (and its physical state), but various techniques have been developed to investigate the targeted reservoir before drilling. The most commonly used methods for investigating high, medium and low enthalpy geothermal systems are geological field observations, structural geology, geophysical methods and geochemical characterization of fluids and gases. The latter allows detailed broad-spectrum information to be obtained at a relatively low cost. This is useful for preliminary reconstruction of the geothermal conceptual model and represents the starting point for its efficient exploitation and adequate management.

Specifically, this Special Issue aims to provide an outlet for the dissemination of peer-reviewed studies utilizing multidisciplinary geochemical approaches to study water and gas geochemistry, isotopic compositions, geothermobarometric funtions and both classical and geostatistical elaboration of major and trace constituents (including toxic elements such as Cr, Ni, As, Cd and Hg).

Topics of interest include, but are not limited to, the following areas:

  • Hydrogeochemical characterization: sampling technics of water and gas, new and/or standard analytical methods for trace elements (including mercury and other toxic elements) and elaboration approaches;
  • Mercury biogeochemical survey of geothermal areas in populated and remote sites;
  • Geostatistical analisys;
  • Geothermometric and geobarometric approaches: chemical and isotopic geothermometers and geochemical modelling;
  • Stable and radioactive isotope studies;
  • Environmental issues/impacts (also due to harmful levels of trace elements) linked to geothermal systems exploitation and management;
  • Geochemical modeling;
  • Geothermal source-specific on long and short term air pollution level (gaseous and particulate emission).

Dr. Giovanni Vespasiano
Dr. Massimiliano Vardè
Dr. Carmine Apollaro
Guest Editors

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Keywords

  • geothermal systems
  • hydrogeochemical characterization
  • geostatistical approach
  • stable and radioactive isotopes
  • geothermometric and geobarometric approach
  • major, trace and toxic elements
  • mercury geochemistry
  • residence time of water
  • heavy metal distribution
  • geothermal reservoir volume
  • geothermal exploitation
  • environmental issues in geothermal areas

Published Papers (5 papers)

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Research

18 pages, 8478 KiB  
Article
Shallow Geothermal Potential of the Sant’Eufemia Plain (South Italy) for Heating and Cooling Systems: An Effective Renewable Solution in a Climate-Changing Society
by Giovanni Vespasiano, Giuseppe Cianflone, Marco Taussi, Rosanna De Rosa, Rocco Dominici and Carmine Apollaro
Geosciences 2023, 13(4), 110; https://doi.org/10.3390/geosciences13040110 - 5 Apr 2023
Cited by 4 | Viewed by 2610
Abstract
In this work, the shallow geothermal heat-exchange potential of a coastal plain in southern Italy, the Sant’Eufemia plain (Calabria region), was evaluated. Stratigraphic and hydrogeological data and thermophysical properties of the main geological formations of the area have been averaged over the first [...] Read more.
In this work, the shallow geothermal heat-exchange potential of a coastal plain in southern Italy, the Sant’Eufemia plain (Calabria region), was evaluated. Stratigraphic and hydrogeological data and thermophysical properties of the main geological formations of the area have been averaged over the first 100 m of subsoil to define the thermal conductivity, the specific heat extraction rates of the ground and the geothermal potential of the area (MWh·y−1) for both cooling and heating modes. The investigation revealed that the crystalline bedrock and the saturated conditions of the sedimentary infill mainly control the heat-exchange potential. The range of the geothermal potential in the investigated Sant’Eufemia plain is 3.61–10.56 MWh·y−1 and 3.72–11.47 MWh·y−1 for heating and cooling purposes, respectively. The average depth drilled to supply a standard domestic power demand of 5.0 kW is ~90 m for heating and ~81 m for cooling modes. The different depth also drives the final drilling costs, which range from EUR 3200 to 8700 for the heating mode and from EUR 2800 to 7800 for the cooling mode. Finally, the mean values of drilling depth and costs for both heating and cooling modes are provided for the main municipalities and strategic sites. Full article
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18 pages, 2580 KiB  
Article
87Sr/86Sr Ratios and Atmospheric Noble Gases in Theistareykir Geothermal Fluids: A Record of Glacial Water
by Daniele Luigi Pinti, Marie Haut-Labourdette, André Poirier, Marion Saby, Vincent J. van Hinsberg, Kim Berlo, Maria Clara Castro, Bjarni Gautason and Ásgerður K. Sigurðardóttir
Geosciences 2022, 12(3), 119; https://doi.org/10.3390/geosciences12030119 - 4 Mar 2022
Cited by 4 | Viewed by 2706
Abstract
The determination of the current and past recharge sources, as well as the reconstruction of the timing of the recharge in geothermal reservoirs, is required in order to correctly assess the resource potential of these systems. Theistareykir is a newly developed geothermal field [...] Read more.
The determination of the current and past recharge sources, as well as the reconstruction of the timing of the recharge in geothermal reservoirs, is required in order to correctly assess the resource potential of these systems. Theistareykir is a newly developed geothermal field close to the well-known exploited fields of Krafla and Námafjall in NE Iceland. In this study, the 87Sr/86Sr ratios measured in deep geothermal fluids are presented and, together with the Cl and noble gas signatures, are used to place constraints on the fluid sources. The Cl/Sr and 87Sr/86Sr ratios show a peculiar and unique composition among Icelandic geothermal fluids. The 87Sr/86Sr ratios range from 0.70355 to 0.70671, suggesting the presence of a significant seawater component—possibly marine aerosols added to rain or snowfall—as well as an additional source of Sr leached from local basalts. Moreover, a correlation between the atmospheric noble gas (ANGs) elemental ratios Ne/Ar, Kr/Ar and Xe/Ar, and the 87Sr/86Sr ratios is observed. The latter results from the mixing of meteoric water with Sr leached from local basalts, meteoric water containing unrelated Sr from seawater, and recharge water with ANGs derived from trapped air bubbles in snow. We suggest that the combined ANGs and Sr seawater signatures are representative of a glacial water source derived from the melting of compacting snow. Full article
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31 pages, 7996 KiB  
Article
An Attempt to Study Natural H2 Resources across an Oceanic Ridge Penetrating a Continent: The Asal–Ghoubbet Rift (Republic of Djibouti)
by Gabriel Pasquet, Rokiya Houssein Hassan, Olivier Sissmann, Jacques Varet and Isabelle Moretti
Geosciences 2022, 12(1), 16; https://doi.org/10.3390/geosciences12010016 - 29 Dec 2021
Cited by 15 | Viewed by 3844
Abstract
Dihydrogen (H2) is generated by fluid–rock interactions along mid-ocean ridges (MORs) and was not, until recently, considered as a resource. However, in the context of worldwide efforts to decarbonize the energy mix, clean hydrogen is now highly sought after, and the [...] Read more.
Dihydrogen (H2) is generated by fluid–rock interactions along mid-ocean ridges (MORs) and was not, until recently, considered as a resource. However, in the context of worldwide efforts to decarbonize the energy mix, clean hydrogen is now highly sought after, and the production of natural H2 is considered to be a powerful alternative to electrolysis. The Afar Rift System has many geological features in common with MORs and offers potential in terms of natural H2 resources. Here, we present data acquired during initial exploration in this region. H2 contents in soil and within fumaroles were measured along a 200 km section across the Asal–Ghoubbet rift and the various intervening grabens, extending from Obock to Lake Abhe. These newly acquired data have been synthesized with existing data, including those from the geothermal prospect area of the Asal–Ghoubbet rift zone. Our results demonstrate that basalt alteration with oxidation of iron-rich facies and simultaneous reduction in water is the likely the source of the hydrogen, although H2S reduction cannot be ruled out. However, H2 volumes at the surface within fumaroles were found to be low, reaching only a few percent. These values are considerably lower than those found in MORs. This discrepancy may be attributed to bias introduced by surface sampling; for example, microorganisms may be preferentially consuming H2 near the surface in this environment. However, the low H2 generation rates found in the study area could also be due to a lack of reactants, such as fayalite (i.e., owing to the presence of low-olivine basalts with predominantly magnesian olivines), or to the limited volume and slow circulation of water. In future, access to additional subsurface data acquired through the ongoing geothermal drilling campaign will bring new insight to help answer these questions. Full article
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29 pages, 13439 KiB  
Article
Geochemical Study on the Annual Variation of Oxygen Isotope and Chemical Composition of Groundwater in the Sho River Alluvium Fan, Toyama, Japan, as an Investigation of Selected Qualitative Aspects of Efficient Utilization of Groundwater Heat
by Kaname Iwatake and Akira Ueda
Geosciences 2021, 11(8), 352; https://doi.org/10.3390/geosciences11080352 - 23 Aug 2021
Cited by 1 | Viewed by 2315
Abstract
Seasonal variations of water temperature, electric conductivity, and oxygen isotope and chemical composition of shallow groundwaters and river waters were determined in the Sho River alluvial fan, western Toyama Prefecture, Japan, to examine groundwater heat utilization for indoor climate control. Samples were collected [...] Read more.
Seasonal variations of water temperature, electric conductivity, and oxygen isotope and chemical composition of shallow groundwaters and river waters were determined in the Sho River alluvial fan, western Toyama Prefecture, Japan, to examine groundwater heat utilization for indoor climate control. Samples were collected at 31 sites every 2 months for 1 year and at 11 representative sites monthly. In addition, the results of monthly precipitation amount and oxygen isotope composition of precipitation collected within the region during the same period were also taken into account. The sources of the shallow groundwaters are a mixture of river water and precipitation. The contribution of precipitation to groundwater is generally small along the Sho River but reaches as much as 80% along the Oyabe River and in the south and west of the alluvial fan. Though the origin of the groundwater differs regionally, water temperature is fixed at around 15 °C throughout the year in the northern part of the alluvial fan, and open-type ground source heat pump systems can be used for cooling and heating there, if adequate quantitative aquifer properties (exploitable groundwater amounts) are present. Full article
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22 pages, 4948 KiB  
Article
Geochemical, Geological and Groundwater Quality Characterization of a Complex Geological Framework: The Case Study of the Coreca Area (Calabria, South Italy)
by Giovanni Vespasiano, Francesco Muto and Carmine Apollaro
Geosciences 2021, 11(3), 121; https://doi.org/10.3390/geosciences11030121 - 8 Mar 2021
Cited by 17 | Viewed by 2506
Abstract
Hydrogeochemical characterization and statistical methods were used to investigate the groundwater quality and the origin of constituents (anthropic or natural) in groundwater of the Coreca area (Calabria, South Italy). Coreca is characterized by an articulated geological setting where the three main geological complexes [...] Read more.
Hydrogeochemical characterization and statistical methods were used to investigate the groundwater quality and the origin of constituents (anthropic or natural) in groundwater of the Coreca area (Calabria, South Italy). Coreca is characterized by an articulated geological setting where the three main geological complexes that distinguish the Northern Calabria Peloritan Orogen (CPO) outcrop. This complex asset affects the quality of groundwater mainly exploited for irrigation use. In particular, the presence of ultramafic rocks (e.g., serpentinite and metabasite) promotes the release of harmful elements such as Cr and Ni. In the studied area, two groups of waters were identified: Ca-HCO3 waters strongly controlled by the interaction with Ca-rich phases (e.g., limestone), and Mg-HCO3 waters related to the interaction of meteoric water with the metamorphic units. Statistical elaboration allowed to detect, in the Mg-HCO3 group, a good correlation between Cr and Ni (not observed in Ca waters) and a negative correlation between Cr, Ca and Al, in agreement with direct interaction with ultramafic rocks characterized by low concentrations of CaO and Al2O3. The concentration of major and trace elements has been compared with the Italian law limit values and the drinking water guidelines provided by the World Health Organization (WHO). Only three samples showed Mn and Ni concentration higher than the Italian law threshold. Furthermore, the assessment of groundwater quality was carried out using salinity and metal indexes. The groundwater quality assessment for irrigation allowed to classify the resource as “excellent to good” and “good to permissible”; nevertheless, a salinity problem and a magnesium hazard were found. Lastly, a metal index (MI) calculation revealed values <1 for almost all samples, pointing to good overall quality. Only a few samples showed a value extremely higher than 1, attributable to prolonged interaction with ultramafic rocks and/or localized anthropogenic pollution. From a general point of view, groundwater showed a generally good quality except for limited areas (and limited to the set of constituents analyzed) and a mild exceedance of the maximum salinity thresholds that must be monitored over time. Through a multidisciplinary approach, it was possible to ascertain the main anomalies attributable to the interaction with the hosting rocks and not (with few exceptions) to anthropic processes. Full article
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