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  • 1
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    Gas seepage and seismogenic structures along the North Anatolian Fault in the eastern Sea of Marmara (2012)
    Wiley
    Details
    Publikationsdatum: 2012-10-25
    Beschreibung: We carried out a combined geophysical and gas-geochemical survey on an active fault strand along the North Anatolian Fault (NAF) system in the Gulf of İzmit (eastern Sea of Marmara), providing for the first time in this area data on the distribution of methane (CH4) and other gases dissolved in the bottom seawater, as well as the CH4 isotopic composition. Based on high-resolution morphobathymetric data and chirp-sonar seismic reflection profiles we selected three areas with different tectonic features associated to the NAF system, where we performed visual and instrumental seafloor inspections, including in situ measurements of dissolved CH4, and sampling of the bottom water. Starting from background values of 2–10 nM, methane concentration in the bottom seawater increases abruptly up to 20 nM over the main NAF trace. CH4 concentration peaks up to ∼120 nM were detected above mounds related probably to gas and fluids expulsion. Methane is microbial (δ13CCH4: −67.3 and −76‰ versus VPDB), and was found mainly associated with pre-Holocene deposits topped by a 10–20 m thick draping of marine mud. The correlation between tectonic structures and gas-seepages at the seafloor suggests that the NAF in the Gulf of İzmit could represent a key site for long-term combined monitoring of fluid exhalations and seismicity to assess their potential as earthquake precursors.
    Digitale ISSN: 1525-2027
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Publiziert von Wiley im Namen von American Geophysical Union (AGU).
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  • 2
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    European seafloor observatory offers new possibilities for deep-sea studies (2000)
    In:  Eos, Trans., Am. Geophys. Un., San Francisco, Pergamon, vol. 81, no. 5, pp. 45, 48, 49, pp. 1246
    Details
    Publikationsdatum: 2000
    Schlagwort(e): Seismology ; OBS ; GEOSTAR ; EU ; CEC ; Geomagnetics ; Oceanography ; GeodesyY ; climate ; abyssal
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    BIBLIOGRAFIE SEISMOLOGIE
  • 3
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    Tiber delta CO2-CH4 degassing: a possible hybrid, tectonically active sediment-hosted geothermal system near Rome (2015)
    Wiley
    Details
    Publikationsdatum: 2015-12-13
    Beschreibung: Fiumicino town in the Tiber River delta, near Rome International Airport (Italy) is historically affected by large amounts of carbon dioxide (CO 2 ) in the ground and gas eruptions triggered by shallow drilling. While it is known that CO 2 originates from carbonate thermo-metamorphism and/or mantle degassing, the origin of methane (CH 4 ) associated with CO 2 is uncertain, and the outgassing spatial distribution is unknown. Combining isotope gas geochemistry, soil-gas and structural-stratigraphic analyses, we provide evidence for a hybrid fluid source system, classifiable as Sediment-Hosted Geothermal System (SHGS), where biotic CH 4 from sedimentary rocks is carried by deep geothermic CO 2 through active segments of a half-graben. Molecular and isotopic composition of CH 4 and concentration of heavier alkanes (ethane and propane), obtained from gas vents and soil-gas throughout the delta area, reveal that thermogenic CH 4 (up to 3.7 vol.% in soil gas; δ 13 C CH4 : -37 to -40‰ VPDB, and δ 2 H CH4 : -162 to -203‰ VSMOW in gas vents), prevails over possible microbial and abiotic components. The hydrocarbons likely result from known Meso-Cenozoic petroleum systems of the Latium Tyrrhenian coast. Over-maturation of source rocks or molecular fractionation induced by gas migration are likely responsible for increased C 1 /C 2+ ratios. CO 2 and CH 4 soil-gas anomalies are scattered along NW-SE and W-E alignments, which, based on borehole, geomorphologic and structural-stratigraphic analyses, coincide with active faults of a half-graben that seems to have controlled the recent evolution of the Tiber delta. This SHGS can be a source of considerable greenhouse gas emissions to the atmosphere and hazards for humans and buildings.
    Print ISSN: 0148-0227
    Thema: Geologie und Paläontologie , Physik
    Publiziert von Wiley im Namen von American Geophysical Union (AGU).
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  • 4
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    Geologic carbon sources may confound ecosystem carbon balance estimates: Evidence from a semiarid steppe in the southeast of Spain (2012)
    Wiley
    Details
    Publikationsdatum: 2012-09-27
    Beschreibung: At a semiarid steppe site located in the SE of Spain, relatively large CO2 emissions were measured that could not be attributed to the ecosystem activity alone. Since the study site was located in a tectonically active area, it was hypothesized that a part of the measured CO2 was of geologic origin. This investigation included a survey of soil CO2 efflux, together with carbon isotope analyses of the CO2 in the soil atmosphere, soil CO2 efflux (i.e., Keeling plots), groundwater and local thermal springs. These measurements confirmed the hypothesis of degassing from geologic sources. In areas with local faults and ancient volcanic structures, soil CO2 efflux rates were significantly higher (i.e., up to 6.3 and 1.4 μmol CO2 m−2 s−1) than measurements in a comparable site that was some distance from fault sites (means of 1.0 and 0.43 μmol CO2 m−2 s−1 in March and June, respectively). The CO2 concentration in the soil atmosphere at the eddy covariance site reached 0.14% v/v at 0.70 m soil depth with a 13C-enriched isotopic composition (δ13C from −10.2‰ to −16.6‰), consistent with the isotopic composition of the soil CO2 efflux estimated by Keeling plots (i.e., −16.6‰). 13C-enriched CO2 also occurred in local aquifers, and there was evidence of degassing from deep crust and mantle at regional scale by the helium isotopic ratio in spring waters located about 30 km (R/Ra: 0.12) and 200 km (R/Ra: 0.95) NW of the eddy covariance site. This study highlights the importance of considering CO2 sources of geologic origin when assessing the net ecosystem carbon balance of sites that may possibly be affected by circulation of such CO2-rich fluids.
    Print ISSN: 0148-0227
    Thema: Biologie , Geologie und Paläontologie
    Publiziert von Wiley im Namen von American Geophysical Union (AGU).
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  • 5
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    Wind as a main driver of the net ecosystem carbon balance of a semiarid Mediterranean steppe in the South East of Spain (2011)
    Wiley
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    Publikationsdatum: 2011-08-29
    Beschreibung: Despite the advance in our understanding of the carbon exchange between terrestrial ecosystems and the atmosphere, semiarid ecosystems have been poorly investigated and little is known about their role in the global carbon balance. We used eddy covariance measurements to determine the exchange of CO 2 between a semiarid steppe and the atmosphere over three years. The vegetation is a perennial grassland of Stipa tenacissima L. located in the SE of Spain. We examined diurnal, seasonal and interannual variations in the net ecosystem carbon balance (NECB) in relation to biophysical variables. Cumulative NECB was a net source of 65.7, 143.6 and 92.1 g C m −2 yr −1 for the three years studied, respectively. We separated the year into two distinctive periods: dry period and growing season . The ecosystem was a net source of CO 2 to the atmosphere, particularly during the dry period when large CO 2 positive fluxes of up to 15 μmol m −2 s −1 were observed in concomitance with large wind speeds. Over the growing season, the ecosystem was a slight sink or neutral with maximum rates of -2.3 μmol m −2 s −1 . Rainfall events caused large fluxes of CO 2 to the atmosphere and determined the length of the growing season . In this season, photosynthetic photon flux density (PPFD) controlled day-time NECB just below 1000 μmol m −2 s −1 . The analyses of the diurnal and seasonal data and preliminary geological and gas-geochemical evaluations, including C isotopic analyses, suggest that the CO 2 released was not only biogenic but most likely included a component of geothermal origin, presumably related to deep fluids occurring in the area. These results highlight the importance of considering geological carbon sources, as well as the need to carefully interpret the results of eddy covariance partitioning techniques when applied in geologically active areas potentially affected by CO 2 -rich geofluid circulation.
    Print ISSN: 1354-1013
    Digitale ISSN: 1365-2486
    Thema: Biologie , Energietechnik , Geographie
    Publiziert von Wiley
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  • 6
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    Earth's degassing: a missing ethane and propane source (2009)
    American Association for the Advancement of Science (AAAS)
    Details
    Publikationsdatum: 2009-01-24
    Beschreibung: Current emission inventories require an additional "unknown" source to balance the global atmospheric budgets of ethane (C2H6). Here, we provide evidence that a substantial part of the missing source can be attributed to natural gas seepage from petroliferous, geothermal, and volcanic areas. Such geologic sources also inject propane (C3H8) into the atmosphere. The analysis of a large data set of methane (CH4), ethane, and propane concentrations in surface gas emissions of 238 sites from different geographic and geologic areas, coupled with published estimates of geomethane emissions, suggests that Earth's degassing accounts for at least 17% and 10% of total ethane and propane emissions, respectively.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Etiope, Giuseppe -- Ciccioli, Paolo -- New York, N.Y. -- Science. 2009 Jan 23;323(5913):478. doi: 10.1126/science.1165904.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma 2, via V. Murata 605, 00143 Rome, Italy. Etiope@ingv.it〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19164741" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
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  • 7
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    Emission of methane and heavier alkanes from the La Brea Tar Pits seepage area, Los Angeles (2017)
    Wiley
    Details
    Publikationsdatum: 2017-10-27
    Beschreibung: Natural hydrocarbon (oil and gas) seeps are widespread in Los Angeles, California, due to gas migration, along faults, from numerous subsurface petroleum fields. These seeps may represent important natural contributors of methane (CH 4 ) and heavier alkanes (C 2 -C 4 ) to the atmosphere, in addition to anthropogenic fossil fuel and biogenic sources. We measured the CH 4 flux by closed-chamber method from the La Brea Tar Pits park (0.1 km 2 ), one of the largest seepage sites in Los Angeles. The gas seepage occurs throughout the park, not only from visible oil-asphalt seeps, but also diffusely from the soil, affecting grass physiology. About 500 kg CH 4 day -1 are emitted from the park, especially along a belt of enhanced degassing that corresponds to the 6 th Street Fault. Additional emissions are from bubble plumes in the lake within the park (order of 10 2 -10 3 kg day -1 ) and at the intersection of Wilshire Blvd. and Curson Ave. (〉130 kg day -1 ), along the same fault. The investigated area has the highest natural gas flux measured thus far for any onshore seepage zone in the USA. Gas migration, oil biodegradation and secondary methanogenesis altered the molecular composition of the original gas accumulated in the Salt Lake Oil Field (〉300 m deep), leading to high C 1 /C 2+ and i-butane/n-butane ratios. These molecular alterations can be important tracers of natural seepage and should be considered in the atmospheric modelling of the relative contribution of fossil fuel (anthropogenic fugitive emission and natural geologic sources) vs biogenic sources of methane, on local and global scales.
    Print ISSN: 0148-0227
    Thema: Geologie und Paläontologie , Physik
    Publiziert von Wiley im Namen von American Geophysical Union (AGU).
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  • 8
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    Geologic carbon sources may confound ecosystem carbon balance estimates: Evidence from a semiarid steppe in the southeast of Spain (2013)
    Wiley
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    Publikationsdatum: 2013-01-03
    Beschreibung: [1]  At a semiarid steppe site located in the SE of Spain, relatively large CO 2 emissions were measured that could not be attributed to the ecosystem activity alone. Since the study site was located in a tectonically active area, it was hypothesized that a part of the measured CO 2 was of geologic origin. This investigation included a survey of soil CO 2 efflux, together with carbon isotope analyses of the CO 2 in the soil atmosphere, soil CO 2 efflux (i.e., Keeling plots), groundwater and local thermal springs. These measurements confirmed the hypothesis of degassing from geologic sources. In areas with local faults and ancient volcanic structures, soil CO 2 efflux rates were significantly higher (i.e., up to 6.3 and 1.4  μ mol CO 2 m −2  s −1 ) than measurements in a comparable site that was some distance from fault sites (means of 1.0 and 0.43  μ mol CO 2 m −2  s −1 in March and June, respectively). The CO 2 concentration in the soil atmosphere at the eddy covariance site reached 0.14% v/v at 0.70 m soil depth with a 13 C-enriched isotopic composition ( δ 13 C from −10.2‰ to −16.6‰), consistent with the isotopic composition of the soil CO 2 efflux estimated by Keeling plots (i.e., −16.6‰). 13 C-enriched CO 2 also occurred in local aquifers, and there was evidence of degassing from deep crust and mantle at regional scale by the helium isotopic ratio in spring waters located about 30 km (R/Ra: 0.12) and 200 km (R/Ra: 0.95) NW of the eddy covariance site. This study highlights the importance of considering CO 2 sources of geologic origin when assessing the net ecosystem carbon balance of sites that may possibly be affected by circulation of such CO 2 -rich fluids.
    Print ISSN: 0148-0227
    Thema: Biologie , Geologie und Paläontologie
    Publiziert von Wiley im Namen von American Geophysical Union (AGU).
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  • 9
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    Gas flux to the atmosphere from mud volcanoes in eastern Romania (2004)
    Oxford, UK : Blackwell Science Ltd
    Terra nova 16 (2004), S. 0 
    Details
    ISSN: 1365-3121
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie
    Notizen: Gas flux measurements have for the first time been taken from vents and soil of eastern Romania mud volcanoes, the largest geological structures in Europe releasing methane into the atmosphere. In the quiescent phase, the methane emission from single vents is up to 28 t yr−1. Diffuse soil microseepage is of the order of 102−105 mg m−2 day−1. A total output of at least 1200 tonnes of CH4 per year can be conservatively estimated over the area investigated alone (∼ 2.3 km2). Helium fluxes are up to five orders of magnitude higher than the average flux in a stable continental area, pointing to a close link between mud volcanoes and crustal degassing through faults crossing the deep hydrocarbon reservoirs. These data represent a key contribution towards refining global CH4-emission estimates, which indicate mud volcanoes as a significant and unavoidable source of greenhouse gases for the atmosphere.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-3121.2004.00542.x
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  • 10
    Digitale Medien
    Digitale Medien
    Laboratory simulation of geogas microbubble flow (1996)
    Springer
    Environmental geology 27 (1996), S. 226-232 
    Details
    ISSN: 1432-0495
    Schlagwort(e): Key words: Geogas ; Microbubbles ; Radionuclide transport ; Gas advection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie
    Notizen: Abstract Preliminary laboratory tests provided first data on the behavior of gas microbubbles through porous media in the framework of the geogas theory. Under experimented conditions with laboratory equipment arranged for pressure controlled gas-tracer injection and sampling, gas microbubbles moved up to ten times faster than single-phase flow in dry media under the same injection pressure. Microbubbles were determined to be very sensitive to changes in injection pressure and their terminal velocity seems to be described with good approximation by the Stokes formula. The capability of microbubbles to pick up and transport upward for short distances solid ultra-small particles (metallic and radionuclide compounds) has been proved. Results are consistent with a time-dependent process linked to the transport properties of microbubbles (e.g. flotation), such as that reported by some authors.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002540050055
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