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  • 03. Hydrosphere::03.04. Chemical and biological::03.04.05. Gases
  • AGU  (3)
  • Copernicus  (1)
  • MDPI Publishing
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Years
  • 1
    Publication Date: 2017-04-04
    Description: The rcsults from measurements of extensive parameters (steam output and exhaling surface area) taken at the crater fumarolic field of Vulcano Island (Aeolian arc, southern Italy)are repoded along with a detailed description of the measuring method. The stem emission rate increased by 1 order of magnitude during the observation time (1983-19951, wlde its concenkation in the released gases was only slightly changed. During the same period the total exhaling surface expanded from 50 m2 to more than 2400 m2 and evolved following preferential trends that coincide with the maul tectonic structures of the island. The observed peaks in steam output slow a positive correlation with episodes of volcanic activity unrest. The temporal increase of steam output and the observed development in the exhaling surface areas are consistent with a volcaxo-tectonic triggering or the exhalating tivity. Particularly, the peaks in the steam outpuat re interpreted as a consequence of degassing from an active magma, slowly moving toward the surface.
    Description: Published
    Description: 29829-29842
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: steam output ; fumaroles ; active volcano ; 03. Hydrosphere::03.04. Chemical and biological::03.04.05. Gases
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Publication Date: 2017-04-04
    Description: Etna volcano, Italy, hosts one of the major groundwater systems of the island of Sicily. Waters circulate within highly permeable fractured, mainly hawaiitic, volcanic rocks. Aquifers are limited downwards by the underlying impermeable sedimentary terrains. Thickness of the volcanic rocks generally does not exceed some 300 m, preventing the waters to reach great depths. This is faced by short travel times (years to tens of years) and low thermalisation of the Etnean groundwaters. Measured temperatures are, in fact, generally lower than 25 °C. But the huge annual meteoric recharge (about 0.97 kmˆ3) with a high actual infiltration coefficient (0.75) implies a great underground circulation. During their travel from the summit area to the periphery of the volcano, waters acquire magmatic heat together with volcanic gases and solutes through water-rock interaction processes. In the last 20 years the Etnean aquifers has been extensively studied. Their waters were analysed for dissolved major, minor and trace element, O, H, C, S, B, Sr and He isotopes, and dissolved gas composition. These data have been published in several articles. Here, after a summary of the obtained results, the estimation of the magmatic heat flux through the aquifer will be discussed. To calculate heat uptake during subsurface circulation, for each sampling point (spring, well or drainage gallery) the following data have been considered: flow rate, water temperature, and oxygen isotopic composition. The latter was used to calculate the mean recharge altitude through the measured local isotopic lapse rate. Mean recharge temperatures, weighted for rain amount throughout the year, were obtained from the local weather station network. Calculations were made for a representative number of sampling points (216) including all major issues and corresponding to a total water flow of about 0.315 kmˆ3/a, which is 40% of the effective meteoric recharge. Results gave a total energy output of about 140 MW/a the half of which is ascribable to only 13 sampling points. These correspond to the highest flow drainage galleries with fluxes ranging from 50 to 1000 l/s and wells with pumping rates from 70 to 250 l/s. Geographical distribution indicates that, like magmatic gas leakage, heat flow is influenced by structural features of the volcanic edifice. The major heat discharge through groundwater are all tightly connected either to the major regional tectonic systems or to the major volcanic rift zones along which the most important flank eruptions take place. But rift zones are much more important for heat upraise due to the frequent dikes injection than for gas escape because generally when dikes have been emplaced the structure is no more permeable to gases because it becomes sealed by the cooling magma.
    Description: Published
    Description: Vienna, Austria
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: open
    Keywords: groundwaters ; volcanic surveillance ; water chemistry ; dissolved gases ; 03. Hydrosphere::03.02. Hydrology::03.02.03. Groundwater processes ; 03. Hydrosphere::03.02. Hydrology::03.02.04. Measurements and monitoring ; 03. Hydrosphere::03.04. Chemical and biological::03.04.03. Chemistry of waters ; 03. Hydrosphere::03.04. Chemical and biological::03.04.05. Gases ; 03. Hydrosphere::03.04. Chemical and biological::03.04.06. Hydrothermal systems
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Oral presentation
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  • 3
    Publication Date: 2017-04-04
    Description: Converging evidence from new top-down and bottomup estimates of fossil "radiocarbon-free" methane emissions indicates that natural geologic sources account for a substantial component of the atmospheric methane budget. Comparing emission estimates based on atmospheric 14CH4 ("radiomethane") with geologic emissions from seepage, including terrestrial macroseeps, microseepage, marine seeps, and geothermal/volcanic emissions from the Earth’s crust, shows that such "geo-CH4" sources can be conservatively estimated at 53 ± 11 Tg yr 1 globally. This makes geo-CH4 second in importance to wetlands as a natural methane source. Such a new appraisal can easily be accommodated within the uncertainty of the global methane budget as recently compiled, and recognizes the importance of geophysical out-gassing of methane generated within the lithosphere. We propose a new coherent contemporary budget in which 30 ± 5% (based on atmospheric radiomethane measurements) of the global source of 582 ± 87 Tg yr 1 has fossil origin, both natural and anthropogenic.
    Description: Published
    Description: L09307
    Description: 3.8. Geofisica per l'ambiente
    Description: JCR Journal
    Description: reserved
    Keywords: methane ; greenhouse-gas ; lithosphere degassing ; 03. Hydrosphere::03.04. Chemical and biological::03.04.05. Gases
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
    Publication Date: 2017-04-03
    Description: Molecular composition, CH4 isotopes and gas flux of all main terrestrial mud volcanoes and other methane seeps in Italy are being assessed for the first time. Whereas 74% of the Italian gas reservoirs are biogenic, about 80% of the seeps release thermogenic gas. Dry-seep gas generally maintains the reservoir C1/(C2 + C3) ‘‘Bernard’’ ratio while mud volcanoes show molecular fractionation likely occurring during advective migration. Accordingly, a simple and direct use of the ‘‘Bernard’’ parameter might be misleading when applied to mud volcanoes as it could not always reflect the reservoir composition. Methane flux into the atmosphere from macro-seep areas is in the order of 102–106 t km-2y-1. Microseepage is widespread throughout large areas and, on a regional scale, it provides the main methane output. A first emission estimate for the total hydrocarbon-prone area of Italy suggests levels of 105 t y-1, comparable to national sources fromfossil fuel industry
    Description: Published
    Description: L14303
    Description: 4.5. Degassamento naturale
    Description: JCR Journal
    Description: reserved
    Keywords: Methane ; Seeps ; mud volcanoes ; 03. Hydrosphere::03.04. Chemical and biological::03.04.05. Gases
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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