scholarly journals Degassing at the Volcanic/Geothermal System of Kos (Greece): Geochemical Characterization of the Released Gases and CO2 Output Estimation

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-16 ◽  
Author(s):  
Kyriaki Daskalopoulou ◽  
Antonina Lisa Gagliano ◽  
Sergio Calabrese ◽  
Lorenza Li Vigni ◽  
Manfredi Longo ◽  
...  
Keyword(s):  
Isotope Composition ◽  
Total Output ◽  
Geothermal System ◽  
Geothermal Systems ◽  
Geochemical Parameters ◽  
Co2 Output ◽  
Before And After ◽  
Flux Measurements ◽  
Of Greece

Forty-five gas samples have been collected from natural gas manifestations at the island of Kos—the majority of which are found underwater along the southern coast of the island. On land, two anomalous degassing areas have been recognized. These areas are mainly characterized by the lack of vegetation and after long dry periods by the presence of sulfate salt efflorescence. Carbon dioxide is the prevailing gas species (ranging from 88 to 99%), while minor amounts of N2 (up to 7.5%) and CH4 (up to 2.1%) are also present. Significant contents of H2 (up to 0.2%) and H2S (up to 0.3%) are found in the on-land manifestations. Only one of the underwater manifestations is generally rich in N2 (up to 98.9%) with CH4 concentrations of up to 11.7% and occasionally extremely low CO2 amounts (down to 0.09%). Isotope composition of He ranges from 0.85 to 6.71 R/RA, indicating a sometimes-strong mantle contribution; the highest values measured are found in the two highly degassing areas of Paradise beach and Volcania. C-isotope composition of CO2 ranges from -20.1 to 0.64‰ vs. V-PDB, with the majority of the values being concentrated at around -1‰ and therefore proposing a mixed mantle—limestone origin. Isotope composition of CH4 ranges from -21.5 to +2.8‰ vs. V-PDB for C and from -143 to +36‰ vs. V-SMOW for H, pointing to a geothermal origin with sometimes-evident secondary oxidation processes. The dataset presented in this work consists of sites that were repeatedly sampled in the last few years, with some of which being also sampled just before and immediately after the magnitude 6.6 earthquake that occurred on the 20th of July 2017 about 15 km ENE of the island of Kos. Changes in the degassing areas along with significant variations in the geochemical parameters of the released gases were observed both before and after the seismic event; however, no coherent model explaining those changes was obtained. CO2 flux measurements showed values of up to about 104 g×m−2×d−1 in both the areas of Volcania and Kokkino Nero, 5×104 g×m−2×d−1 at Paradise beach, and 8×105 g×m−2×d−1 at Therma spring. CO2 output estimations gave values of 24.6, 16.8, 12.7, and 20.6 t×d−1, respectively, for the above four areas. The total output of the island is 74.7 t×d−1 and is comparable to those of the other active volcanic/geothermal systems of Greece (Nisyros, Nea Kameni, Milos, Methana, and Sousaki).

scholarly journals Hydrothermal methane fluxes from the soil at Lakki plain (Nisyros Island, Greece)

2016 ◽  
Vol 47 (4) ◽  
pp. 1920
Author(s):  
W. D’Alessandro ◽  
A. L. Gagliano ◽  
K. Kyriakopoulos ◽  
F. Parello
Keyword(s):  
Co2 Flux ◽  
Total Output ◽  
Geothermal System ◽  
Ch4 Flux ◽  
Co2 Output ◽  
Fumarolic Gases ◽  
Methane Fluxes ◽  
Order Of Magnitude ◽  
Flux Measurements ◽  
Accumulation Chamber Method

Methane and CO2 flux measurements from the soils were made with the accumulation chamber method in Lakki plain covering an area of about 0.06 km2 including the main fumarolic areas of Kaminakia, Stefanos and Phlegeton. Flux values measured at 77 sites range from –3.4 to 1420 mg m-2 d-1 for CH4 and from 0.1 to 383 g m-2 d-1 for CO2. The three fumarolic areas show very different methane degassing patterns, Kaminakia showing the highest flux values. Methane output can be estimated in about 0.01 t a-1 from an area of about 2500 m2 at Phlegeton, about 0.1 t a-1 from an area of about 20,000 m2 at Stefanos and about 0.25 t a-1 from an area of about 30,000 m2 at Kaminakia. The total output from the entire geothermal system of Nisyros should not exceed 1 t a-1. Previous estimates of the CH4 output at Nisyros, based on soil CO2 output and CH4/CO2 ratios in fumarolic gases, were more than one order of magnitude higher. The present work further underscores the utmost importance of direct CH4 flux data.

scholarly journals FLUID GEOCHEMISTRY INVESTIGATIONS ON THE VOLCANIC SYSTEM OF METHANA

2007 ◽  
Vol 40 (2) ◽  
pp. 712
Author(s):  
W. D'Alessandro ◽  
L. Brusca ◽  
K. Kyriakopoulos ◽  
M. Margaritopoulos ◽  
G. Michas ◽  
...  
Keyword(s):  
Geothermal System ◽  
Volcanic System ◽  
Spatially Correlated ◽  
Co2 Output ◽  
Active Tectonic ◽  
Soil Site ◽  
Gas Hazard ◽  
Tectonic System ◽  
Cold Groundwaters

An extensive geochemical survey on the fluids released by the volcanic/geothermal system of Methana was undertaken. Characterization of the gases was made on the basis of the chemical and isotopie (He and C) analysis of 14 samples. CO2 soil gas concentration and fluxes were measured on the whole peninsula at more than 100 sampling sites. 31 samples of thermal and cold groundwaters were also sampled and analysed to characterize the geochemistry of aquifers. Anomalies referable to the geothermal system, besides at known thermal manifestations, were also recognized at some anomalous degassing soil site and in some cold groundwater. These anomalies were always spatially correlated to the main active tectonic system of the area. The total CO2 output of the volcanic system has been preliminary estimated in about 0.2 kg s~ . Although this value is low compared to other volcanic systems, anomalous C02 degassing at Methana may pose gas hazard problems. Such volcanic risk, although restricted to limited areas, cannot be neglected and further studies have to be undertaken for its better assessment.

scholarly journals New Conceptual Model for the Magma-Hydrothermal-Tectonic System of Krafla, NE Iceland

Geosciences ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 34 ◽  
Author(s):  
Knútur Árnason
Keyword(s):  
Isotope Composition ◽  
Geological Structure ◽  
Geothermal System ◽  
Geothermal Systems ◽  
Thermal Fluids ◽  
Tectonic History ◽  
Geothermal Activity ◽  
History Of ◽  
Tectonic System ◽  
Altered Basalt

The complexity of the Krafla volcano and its geothermal system(s) has puzzled geoscientists for decades. New and old geoscientific studies are reviewed in order to shed some light on this complexity. The geological structure and history of the volcano is more complex than hitherto believed. The visible 110 ka caldera hosts, now buried, an 80 ka inner caldera. Both calderas are bisected by an ESE-WNW transverse low-density structure. Resistivity surveys show that geothermal activity has mainly been within the inner caldera but cut through by the ESE-WNW structure. The complexity of the geothermal system in the main drill field can be understood by considering the tectonic history. Isotope composition of the thermal fluids strongly suggests at least three different geothermal systems. Silicic magma encountered in wells K-39 and IDDP-1 indicates a hitherto overlooked heat transport mechanism in evolved volcanos. Basaltic intrusions into subsided hydrothermally altered basalt melt the hydrated parts, producing a buoyant silicic melt which migrates upwards forming sills at shallow crustal levels which are heat sources for the geothermal system above. This can explain the bimodal behavior of evolved volcanos like Krafla and Askja, with occasional silicic, often phreatic, eruptions but purely basaltic in-between. When substantial amounts of silicic intrusions/magma have accumulated, major basalt intrusion(s) may “ignite” them causing a silicic eruption.

Time-lapse magnetotelluric monitoring of an enhanced geothermal system

Geophysics ◽  
2013 ◽  
Vol 78 (3) ◽  
pp. B121-B130 ◽  
Author(s):  
Jared R. Peacock ◽  
Stephan Thiel ◽  
Graham S. Heinson ◽  
Peter Reid
Keyword(s):  
South Australia ◽  
Time Lapse ◽  
Fault System ◽  
Fluid Distribution ◽  
Geothermal System ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Hydraulic Stimulation ◽  
Microseismic Data ◽  
Before And After

Realization of enhanced geothermal systems (EGSs) prescribes the need for novel methods to monitor subsurface fracture connectivity and fluid distribution. Magnetotellurics (MT) is a passive electromagnetic (EM) method sensitive to electrical conductivity contrasts as a function of depth, specifically hot saline fluids in a resistive porous media. In July 2011, an EGS fluid injection at 3.6-km depth near Paralana, South Australia, was monitored by comparing repeated MT surveys before and after hydraulic stimulation. An observable coherent change above measurement error in the MT response was present and causal, in that variations in phase predict variations in apparent resistivity. Phase tensor residuals proved the most useful representation for characterizing alterations in subsurface resistivity structure, whereas resistivity tensor residuals aided in determining the sign and amplitude of resistivity variations. These two tensor representations of the residual MT response suggested fluids migrated toward the northeast of the injection well along an existing fault system trending north-northeast. Forward modeling and concurrent microseismic data support these results, although microseismic data suggest fractures opened along two existing fracture networks trending north-northeast and northeast. This exemplifies the need to use EM methods for monitoring fluid injections due to their sensitivity to conductivity contrasts.

scholarly journals Integrated Approach for Detecting Convection Effects in Geothermal Environments Based on TIR Camera Measurements

2021 ◽  
Vol 11 (7) ◽  
pp. 3185
Author(s):  
Susana Del Pozo ◽  
Cristina Sáez-Blázquez ◽  
Ignacio Martín Nieto ◽  
Susana Lagüela
Keyword(s):  
Thermal Conductivity ◽  
Infrared Camera ◽  
Heat Rate ◽  
Thermal Characterization ◽  
Thermal Infrared ◽  
Integrated Approach ◽  
Geothermal System ◽  
Radiometric Calibration ◽  
Geothermal Systems

Thermal characterization of soils is essential for many applications, including design of geothermal systems. Traditional devices focus on the computation of thermal conductivity, omitting the analysis of the convection effect, which is important for horizontal geothermal systems. In this paper, a procedure based on the monitoring of the surface of the soil with a thermal infrared (TIR) camera is developed for the evaluation of the global thermal imbalance on the surface and in-depth. This procedure allows for the computation of thermal conductivity and global convection heat rate, consequently constituting a complete thermal characterization of the geothermal system. The validation of the results is performed through the evaluation of the radiometric calibration of the thermal infrared camera used for the monitoring and the comparison of the thermal conductivity values obtained in-depth, with traditional methods, and for the surface of the system.

scholarly journals Analysis of the Influence of Reducing the Duration of a Thermal Response Test in a Water-Filled Geothermal Borehole Located in Spain

Energies ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 6693
Author(s):  
Ignacio Martín Nieto ◽  
Cristina Sáez Blázquez ◽  
Arturo Farfán Martín ◽  
Diego González-Aguilera
Keyword(s):  
Thermal Response ◽  
Thermal Characterization ◽  
Geothermal System ◽  
Thermal Response Test ◽  
Geothermal Systems ◽  
Time Intervals ◽  
Response Test ◽  
High Investment ◽  
Time Reduction

Usually thermal response tests are restricted to big geothermal projects; the high investment makes them less suitable for designing domestic low-enthalpy geothermal energy systems. The work here presented aims to study the influence of time reduction in thermal response tests on their precision. Due to the importance of the correct assessment of the thermal characterization of the ground for any kind of geothermal system, time reduction in this essay could make it more affordable to be implemented in some domestic systems. A thermal response test has been implemented, and several time intervals of the test have been considered in order to obtain different results for the thermal conductivity of the ground. The mentioned results have been then compared and also the domestic geothermal systems designed from them by the use of the geothermal software GES-CAL. Results have shown that, in some cases (our testing borehole has some singular characteristics), a significant time reduction in the data acquisition process of the thermal response test does not compromise seriously the precision of the results.

An Electron Microscope Study of Interdiffusion and Compound Formation in Ta-Au Thin Films

1973 ◽  
Vol 31 ◽  
pp. 32-33 ◽  
Author(s):  
T. C. Tisone ◽  
S. Lau
Keyword(s):  
Electron Microscope ◽  
Electron Microscope Study ◽  
Thermally Grown Oxide ◽  
Ion Milling ◽  
Compound Formation ◽  
Technology Application ◽  
Transmission Electron ◽  
Before And After ◽  
Au Thin Films

In a study of the properties of a Ta-Au metallization system for thin film technology application, the interdiffusion between Ta(bcc)-Au, βTa-Au and Ta2M-Au films was studied. Considered here is a discussion of the use of the transmission electron microscope(TEM) in the identification of phases formed and characterization of the film microstructures before and after annealing.The films were deposited by sputtering onto silicon wafers with 5000 Å of thermally grown oxide. The film thicknesses were 2000 Å of Ta and 2000 Å of Au. Samples for TEM observation were prepared by ultrasonically cutting 3mm disks from the wafers. The disks were first chemically etched from the silicon side using a HNO3 :HF(19:5) solution followed by ion milling to perforation of the Au side.

scholarly journals Adsorption Studies on Magnetic Nanoparticles Functionalized with Silver to Remove Nitrates from Waters

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1757
Author(s):  
Yesica Vicente-Martínez ◽  
Manuel Caravaca ◽  
Antonio Soto-Meca ◽  
Miguel Ángel Martín-Pereira ◽  
María del Carmen García-Onsurbe
Keyword(s):  
Magnetic Nanoparticles ◽  
Nitrate Content ◽  
Adsorption Efficiency ◽  
Experimental Conditions ◽  
Dependent Behavior ◽  
Before And After ◽  
Naoh Solution ◽  
High Concentrations ◽  
Interference Studies

This paper presents a novel procedure for the treatment of contaminated water with high concentrations of nitrates, which are considered as one of the main causes of the eutrophication phenomena. For this purpose, magnetic nanoparticles functionalized with silver (Fe3O4@AgNPs) were synthesized and used as an adsorbent of nitrates. Experimental conditions, including the pH, adsorbent and adsorbate dose, temperature and contact time, were analyzed to obtain the highest adsorption efficiency for different concentration of nitrates in water. A maximum removal efficiency of 100% was reached for 2, 5, 10 and 50 mg/L of nitrate at pH = 5, room temperature, and 50, 100, 250 and 500 µL of Fe3O4@AgNPs, respectively. The characterization of the adsorbent, before and after adsorption, was performed by energy dispersive X-ray spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller analysis and Fourier-transform infrared spectroscopy. Nitrates can be desorbed, and the adsorbent can be reused using 500 µL of NaOH solution 0.01 M, remaining unchanged for the first three cycles, and exhibiting 90% adsorption efficiency after three regenerations. A deep study on equilibrium isotherms reveals a pH-dependent behavior, characterized by Langmuir and Freundlich models at pH = 5 and pH = 1, respectively. Thermodynamic studies were consistent with physicochemical adsorption for all experiments but showed a change from endothermic to exothermic behavior as the temperature increases. Interference studies of other ions commonly present in water were carried out, enabling this procedure as very selective for nitrate ions. In addition, the method was applied to real samples of seawater, showing its ability to eliminate the total nitrate content in eutrophized waters.

scholarly journals Genetic characterization at the species and symbiovar level of indigenous rhizobial isolates nodulating Phaseolus vulgaris in Greece

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Evdoxia Efstathiadou ◽  
Georgia Ntatsi ◽  
Dimitrios Savvas ◽  
Anastasia P. Tampakaki
Keyword(s):  
Phaseolus Vulgaris ◽  
Common Bean ◽  
Phylogenetic Affiliation ◽  
Rhizobial Inoculation ◽  
Rhizobial Species ◽  
The Common ◽  
First Time ◽  
Of Greece ◽  
Rhizobial Isolates

AbstractPhaseolus vulgaris (L.), commonly known as bean or common bean, is considered a promiscuous legume host since it forms nodules with diverse rhizobial species and symbiovars. Most of the common bean nodulating rhizobia are mainly affiliated to the genus Rhizobium, though strains belonging to Ensifer, Pararhizobium, Mesorhizobium, Bradyrhizobium, and Burkholderia have also been reported. This is the first report on the characterization of bean-nodulating rhizobia at the species and symbiovar level in Greece. The goals of this research were to isolate and characterize rhizobia nodulating local common bean genotypes grown in five different edaphoclimatic regions of Greece with no rhizobial inoculation history. The genetic diversity of the rhizobial isolates was assessed by BOX-PCR and the phylogenetic affiliation was assessed by multilocus sequence analysis (MLSA) of housekeeping and symbiosis-related genes. A total of fifty fast-growing rhizobial strains were isolated and representative isolates with distinct BOX-PCR fingerpriniting patterns were subjected to phylogenetic analysis. The strains were closely related to R. anhuiense, R. azibense, R. hidalgonense, R. sophoriradicis, and to a putative new genospecies which is provisionally named as Rhizobium sp. I. Most strains belonged to symbiovar phaseoli carrying the α-, γ-a and γ-b alleles of nodC gene, while some of them belonged to symbiovar gallicum. To the best of our knowledge, it is the first time that strains assigned to R. sophoriradicis and harbored the γ-b allele were found in European soils. All strains were able to re-nodulate their original host, indicating that they are true microsymbionts of common bean.

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