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  • 04. Solid Earth::04.08. Volcanology::04.08.01. Gases  (5)
  • 2005-2009  (5)
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  • 1
    Publication Date: 2017-04-04
    Description: The city of Rome lies between the two Quaternary volcanic complexes of Mts. Sabatini, to the North, and of Alban Hills to the South. Both these volcanic areas are characterized by zones with a huge endogenous degassing and several accidents have occurred to people and animals in the last 20 years. CO2 is the main component (up to 98 vol.%) of the gas emissions followed by H2S (1-2 vol.%), and N2. The Caldara di Manziana depression hosts the main gas manifestation of Mts. Sabatini. Here a total (diffusive and viscous) CO2 release of ca. 160 tons/day from 0.15 Km2 has been measured. The Colli Albani edifice extends to the south-eastern periphery of Rome. Its main gas emission zones are Cava dei Selci and Solforata di Pomezia. Cava dei Selci is an area located in the suburb of the homonymous village. CO2 diffusive flux from the soil (from 6000 m2) ranged between 25 and 5 tons/day in the last 7 years. The continuous monitoring of CO2 and H2S in air (1m) in the confining village has shown the frequent overcome of the (TWA and STEL) threshold limits for both gases. At Solforata di Pomezia a 44 tons/day CO2 diffusive flux has been estimated from 1.9 hectares, with 0.5 tons/day of H2S. On 2007, two multi-technique surveys have been carried out to estimate the total gas output of these three degassing sites, by measuring CO2 and H2S fluxes from the soil (by accumulation chambers) and the gas flux from bubbling pools. Moreover the CO2 and H2S concentration in air were measured by several TDL profiles. Results confirm the high gas hazard of these areas. Particularly in late afternoon and night, when wind strongly lowers, lethal concentrations are frequently reached by H2S, whereas CO2 remains at high but tolerable values.
    Description: Submitted
    Description: Shimabara, Giappone
    Description: 4.5. Degassamento naturale
    Description: open
    Keywords: Gas hazard, TDL, CO2 and H2S soil flux, Roman volcanic Province ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Poster session
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  • 2
    Publication Date: 2017-04-04
    Description: The northwestern flank of the Colli Albani, a Quaternary volcanic complex near Rome, is characterised by high CO2 values and Rn activities in the groundwater and by the presence of zones with strong emission of gas from the soil. The most significant of these zones is Cava dei Selci where many houses are located very near to the gas emission site. The emitted gas consists mainly of CO2 (up to 98 vol) with an appreciable content of H2S (0.8). The He and C isotopic composition indicates, as for all fluids associated with the Quaternary Roman and Tuscany volcanic provinces, the presence of an upper mantle component contaminated by crustal fluids associated with subducted sediments and carbonates. An advective CO2 flux of 37 tons/day has been estimated from the gas bubbles rising to the surface in a small drainage ditch and through a stagnant water pool, present in the rainy season in a topographically low central part of the area. A CO2 soil flux survey with an accumulation chamber, carried out in February-March 2000 over a 12 000 m2 surface with 242 measurement points, gave a total (mostly conductive) flux of 61 tons/day. CO2 soil flux values vary by four orders of magnitude over a 160-m distance and by one order of magnitude over several metres. A fixed network of 114 points over 6350 m2 has been installed in order to investigate temporal flux variations. Six surveys carried out from May 2000 to June 2001 have shown large variations of the total CO2 soil flux (8/25 tons/day). The strong emission of CO2 and H2S, which are gases denser than air, produces dangerous accumulations in low areas which have caused a series of lethal accidents to animals and one to a man. The gas hazard near the houses has been assessed by continuously monitoring the CO2 and H2S concentration in the air at 75 cm from the ground by means of two automatic stations. Certain environmental parameters (wind direction and speed; atm P, T, humidity and rainfall) were also continuously recorded. At both stations, H2S and CO2 exceeded by several times the recommended concentration thresholds. The highest CO2 and H2S values were recorded always with wind speeds less than 1.5 m/s, mostly in the night hours. Our results indicate that there is a severe gas hazard for people living near the gas emission site of Cava dei Selci, and appropriate precautionary and prevention measures have been recommended both to residents and local authorities.
    Description: - GNV funded research project Gas Hazard of Colli Albani
    Description: Published
    Description: 81^94
    Description: partially_open
    Keywords: Colli Albani ; CO2 flux ; H2S ; gas hazard ; 01. Atmosphere::01.01. Atmosphere::01.01.07. Volcanic effects ; 04. Solid Earth::04.01. Earth Interior::04.01.02. Geological and geophysical evidences of deep processes ; 04. Solid Earth::04.03. Geodesy::04.03.06. Measurements and monitoring ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.02. Experimental volcanism ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 05. General::05.02. Data dissemination::05.02.01. Geochemical data ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Format: 539 bytes
    Format: 660932 bytes
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  • 3
    Publication Date: 2017-04-04
    Description: Significant changes in the helium and carbon isotopic composition of shallow thermal waters vs. gas and a crater fumarolic gas have been recorded at Stromboli prior and during the 2002–2003 eruption. The 3He/4He ratios corrected for air contamination (Rc/Ra), and δ13C of fumarolic gases gradually increased from May to November 2002 before the eruption onset. These variations imply early degassing of a gas-rich magma at depth that likely fed both the intense Strombolian activity and small lava overflows recorded during that period. The lava effusion of late December 2002 was shortly preceded by a marked Rc/Ra decrease both in water and fumarolic gases. Comparison of He/CO2 and CH4/CO2 ratios in dissolved gas and with δ13CCO2 values rules out the Rc/Ra decrease due to an increasing input of radiogenic 4He. The Rc/Ra decrease is attributed to the He isotope fractionation during rapid magma ascent and degassing. A new uprising of 3He-rich magma probably occurred in January to February 2003, when Rc/Ra ratios displayed the highest values in dissolved gases ever measured before (4.56 Rc/Ra). The increase in He/CO2 and CH4/CO2 ratios and decrease in δ13C of dissolved CO2 was recorded after the 5 April 2003 explosive paroxysm, likely caused by enhanced gas-water interaction inducing CO2 dissolution. No anomalous Rc/Ra values were recorded in the same period, when usual Strombolian activity gradually resumed.
    Description: Published
    Description: 118–134
    Description: partially_open
    Keywords: Stromboli ; Eruption ; Geochemistry ; Helium ; Isotopes ; Magma ascent ; Dissolved gases ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Format: 535 bytes
    Format: 482068 bytes
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  • 4
    Publication Date: 2017-04-04
    Description: Recent studies suggested that Alban Hills (Rome) is a quiescent and not an extinct volcano, as it produced Holocene eruptions and several lahars until Roman times by water overflow fromthe Albano crater lake. Alban Hills are presently characterized by high PCO2 in groundwaters and by several cold gas emissions usually in sites where excavations removed the superficial impervious cover. Gas consists mostly of CO2 with minor H2S and the diffuse CO2 soil flux is locally very high. Accidental gas blowouts, occurred during shallow well drillings (tens to hundreds m depth) in zones with no surface gas manifestations, indicate the presence of gas pressurized aquifers confined underneath impermeable layers, within both the volcanic rock pile and the underlying Pleistocene loose sediments. Degassing mostly occurs in correspondence of bordering faults of buried horsts cut in the Mesozoic carbonate basement, hosting the main aquifer. Carbon isotopic composition (δ13CCO2) suggests that CO2 is at least partly originated by thermal decarbonation of these limestones. 3He/4He isotopic ratio of the gas (up to 1.9 Ra) is the same or even slightly higher than that of olivine and clinopyroxene fluid inclusions of the Alban Hills volcanic products, indicating a possible magmatic source for the gas. Low R/Ra values, compared to MORB and island arc magmas, are characteristic of the potassic Roman Comagmatic Province and reflect a deep involvement of crustal material in the magma genesis. The lack of high temperature fumaroles can be explained by an efficient meteoric cold water penetration and circulation in the volcano permeable terrains.
    Description: Published
    Description: 5-16
    Description: 4.5. Degassamento naturale
    Description: JCR Journal
    Description: reserved
    Keywords: Alban Hills ; magma degassing ; CO2 fluxes ; gas blowouts ; C and He isotopes ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
    Publication Date: 2017-04-04
    Description: Systematic CO2 soil flux surveys at Cava dei Selci on the Colli Albani volcano (28 seasonal surveys since the year 2000) have shown a significant variation of diffuse CO2 release, with a marked decrease, from 25 to 4 tonnes/day, from May 2000 to August 2004, followed by a new increase. Over the same period, CO2 flux halved at S. Maria delle Mole (16.8 tonnes/day in 2000 and 8.3 tonnes/day in 2006). Also the quantity of CO2 dissolved in the deep waters of the Albano crater lake decreased by one order of magnitude in the period 1997-2006. The high CO2 flux values in 2000 could represent the “tail” of a strong degassing episode recorded at Colli Albani in 1995 and related to local earthquakes. The following decrease of CO2 flux could reflect a permeability decrease caused by hydrothermal calcite precipitation favored by PCO2 reduction in the deep source
    Description: Published
    Description: Kunming, China
    Description: 4.5. Degassamento naturale
    Description: open
    Keywords: CO2 soil flux, Alban Hills volcano, gas hazard ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Conference paper
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