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  • Methane
  • Elsevier  (6)
  • Wiley  (1)
  • Institute of Electrical and Electronics Engineers (IEEE)
  • Springer Science + Business Media
  • 2020-2023  (3)
  • 2005-2009  (4)
  • 1955-1959
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Year
  • 1
    Publication Date: 2017-04-04
    Description: The “methane-led hypotheses” assume that gas hydrates and marine seeps are the sole geologic factors controlling Quaternary atmospheric and climate changes. Nevertheless, a wider class of geologic sources of methane exist which could have played a role in past climate changes. Beyond offshore seepage, relevant geologic emissions of methane (GEM) are from onshore seepage, including mud volcanism, microseepage and geothermal flux; altogether GEM are the second most important natural source of atmospheric methane at present. The amount of methane entering the atmosphere from onshore GEM seems to prevail on that from offshore seepage. Onshore sources inject a predominantly isotopically heavy (13C-enriched) methane into the atmosphere. They are controlled mainly by endogenic (geodynamic) processes, which induce large-scale gas flow variations over geologic and millennial time scales, and only partially by exogenic (surface) conditions, so that they are not affected by negative feedbacks. The eventual influence on atmospheric methane concentration does not necessarily require catastrophic or abrupt releases, as proposed for the “clathrate gun hypothesis”. Enhanced degassing from these sources could have contributed to the methane trends observed in the ice core records, and could explain the late Quaternary peaks of increased methane concentrations accompanied by the enrichment of isotopically heavy methane, as recently observed. This hypothesis shall be tested by means of robust multidisciplinary studies, mainly based on a series of atmospheric, biologic and geologic proxies.
    Description: Published
    Description: On line First
    Description: 4.5. Degassamento naturale
    Description: JCR Journal
    Description: reserved
    Keywords: Methane ; climate change ; seepage ; Quaternary ; 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: 2017-04-03
    Description: Central to any study of climate change is the development of an inventory that identifies and quantifies natural and anthropogenic sources and sinks of greenhouse gases (GHG). Recent studies have demonstrated that geologic emissions of methane (GEM), although not considered in the inventories of the IntergovernmentalPanel on Climate Change (IPCC), are an important GHG source. Etiope and Klusman (2002, Chemosphere 49, 777–789) documented that significant amounts of methane, produced within the Earth crust, are released naturally into the atmosphere through faults and fractured rocks. Major GEMs are related to hydrocarbon production in sedimentary basins (biogenic and thermogenic methane), through continuous exhalation and eruptions from more than 1200 onshore and offshore mud volcanoes (MVs), through diffuse soil microseepage, and shallow marine seeps; secondarily, methane is released from geothermal and volcano-magmatic systems. Minor geologic sources are those related to natural exhalation from coal-bearing rocks (influenced by mining activities), degassing from crystalline basement and mantle. While marine seeps have been studied for decades, methane flux from MVs has been the object of detailed measurements only since 2001, when hundreds of gas flux measurements were performed from vents and soilin the main terrestrial MVs of Europe, in Romania and Italy (Etiope et al.,2003, Geophysical Research Letters 30, 1094, doi:10.1029/2002GL016287; and references therein). In 2003 gas flux was measured in Azerbaijan, which hosts the world’s biggest MVs and densest MV population (Etiope et al., 2004, Geology, in press). In all areas investigated around 102–103 tons of methane per km2 are annually injected into the atmosphere. The global estimates of GEM from MVs range from 5 to 13Tg yr-1 (Etiope and Milkov, 2004, Environmental Geology, in press).
    Description: Published
    Description: 3099-3100
    Description: 4.5. Degassamento naturale
    Description: JCR Journal
    Description: reserved
    Keywords: Methane ; atmospheric gas budget ; 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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  • 3
    Publication Date: 2017-04-04
    Description: It has recently been demonstrated that methane emission from lithosphere degassing is an important component of the natural greenhouse-gas atmospheric budget. Globally, the geological sources are mainly due to seepage from hydrocarbon-prone sedimentary basins, and subordinately from geothermal/volcanic fluxes. This work provides a first estimate of methane emission from the geothermal/volcanic component at European level. In Europe, 28 countries have geothermal systems and at least 10 countries host surface geothermal manifestations (hot springs, mofettes, gas vents). Even if direct methane flux measurements are available only for a few small areas in Italy, a fair number of data on CO2, CH4 and steam composition and flux from geothermal manifestations are today available for 6 countries (Czech Republic, Germany, Greece, Iceland, Italy, Spain). Following the emission factor and area-based approach, the available data have been analyzed and have led to an early and conservative estimate of methane emission into the atmosphere around 10,000 ton/yr (4000–16,000 ton/yr), basically from an area smaller than 4000 km2, with a speculative upper limit in the order of 105 ton/yr. Only 4–18% of the conservative estimate (about 720 ton/yr) is due to 12 European volcanoes, where methane concentration in volcanic gases is generally in the order of a few tens of ppmv. Volcanoes are thus not a significant methane source. While the largest emission is due to geothermal areas, which may be situated next to volcanoes or independent. Here inorganic synthesis, thermometamorphism and thermal breakdown of organic matter are substantial. Methane flux can reach hundreds of ton/yr from small individual vents. Geothermal methane is mainly released in three countries located in the main high heat flow regions: Italy, Greece, and Iceland. Turkey is likely a fourth important contributor but the absolute lack of data prevents any emission estimate. Therefore, the actual European geothermal–volcanic methane emission could be easily projected to the 105 ton/yr levels, reaching the magnitude of some other natural sources such as forest fires or wild animals.
    Description: Published
    Description: 76-86
    Description: 4.5. Degassamento naturale
    Description: JCR Journal
    Description: reserved
    Keywords: Methane ; volcanoes ; Geothermal vents ; 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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  • 4
    Publication Date: 2017-04-04
    Description: The atmospheric methane budget is commonly defined assuming that major sources derive from the biosphere (wetlands, rice paddies, animals, termites) and that fossil, radiocarbon-free CH4 emission is due to and mediated by anthropogenic activity (natural gas production and distribution, and coal mining). However, the amount of radiocarbon- free CH4 in the atmosphere, estimated at approximately 20% of atmospheric CH4, is higher than the estimates from statistical data of CH4 emission from fossil fuel related anthropogenic sources. This work documents that significant amounts of ‘‘old’’ methane, produced within the Earth crust, can be released naturally into the atmosphere through gas permeable faults and fractured rocks. Major geologic emissions of methane are related to hydrocarbon production in sedimentary basins (biogenic and thermogenic methane) and, subordinately, to inorganic reactions (Fischer-Tropsch type) in geothermal systems. Geologic CH4 emissions include diffuse fluxes over wide areas, or microseepage, on the order of 100–102 mgm 2 day 1, and localised flows and gas vents, on the order of 102 t y 1, both on land and on the seafloor. Mud volcanoes producing flows of up to 103 t y 1 represent the largest visible expression of geologic methane emission. Several studies have indicated that methanotrophic consumption in soil may be insufficient to consume all leaking geologic CH4 and positive fluxes into the atmosphere can take place in dry or seasonally cold environments. Unsaturated soils have generally been considered a major sink for atmospheric methane, and never a continuous, intermittent, or localised source to the atmosphere. Although geologic CH4 sources need to be quantified more accurately, a preliminary global estimate indicates that there are likely more than enough sources to provide the amount of methane required to account for the suspected missing source of fossil CH4.
    Description: Published
    Description: 777-789
    Description: 4.5. Degassamento naturale
    Description: JCR Journal
    Description: reserved
    Keywords: Methane ; seepage ; 03. Hydrosphere::03.04. Chemical and biological::03.04.02. Carbon cycling
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
    Publication Date: 2022-10-27
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Sanders‐DeMott, R., Eagle, M., Kroeger, K., Wang, F., Brooks, T., Suttles, J., Nick, S., Mann, A., & Tang, J. Impoundment increases methane emissions in Phragmites‐invaded coastal wetlands. Global Change Biology, 28(15), (2022): 4539– 4557. https://doi.org/10.1111/gcb.16217.
    Description: Saline tidal wetlands are important sites of carbon sequestration and produce negligible methane (CH4) emissions due to regular inundation with sulfate-rich seawater. Yet, widespread management of coastal hydrology has restricted tidal exchange in vast areas of coastal wetlands. These ecosystems often undergo impoundment and freshening, which in turn cause vegetation shifts like invasion by Phragmites, that affect ecosystem carbon balance. Understanding controls and scaling of carbon exchange in these understudied ecosystems is critical for informing climate consequences of blue carbon restoration and/or management interventions. Here, we (1) examine how carbon fluxes vary across a salinity gradient (4–25 psu) in impounded and natural, tidally unrestricted Phragmites wetlands using static chambers and (2) probe drivers of carbon fluxes within an impounded coastal wetland using eddy covariance at the Herring River in Wellfleet, MA, United States. Freshening across the salinity gradient led to a 50-fold increase in CH4 emissions, but effects on carbon dioxide (CO2) were less pronounced with uptake generally enhanced in the fresher, impounded sites. The impounded wetland experienced little variation in water-table depth or salinity during the growing season and was a strong CO2 sink of −352 g CO2-C m−2 year−1 offset by CH4 emission of 11.4 g CH4-C m−2 year−1. Growing season CH4 flux was driven primarily by temperature. Methane flux exhibited a diurnal cycle with a night-time minimum that was not reflected in opaque chamber measurements. Therefore, we suggest accounting for the diurnal cycle of CH4 in Phragmites, for example by applying a scaling factor developed here of ~0.6 to mid-day chamber measurements. Taken together, these results suggest that although freshened, impounded wetlands can be strong carbon sinks, enhanced CH4 emission with freshening reduces net radiative balance. Restoration of tidal flow to impounded ecosystems could limit CH4 production and enhance their climate regulating benefits.
    Description: This project was supported by USGS-NPS Natural Resources Preservation Program #2021-07, U.S. Geological Survey Coastal & Marine Hazards and Resources Program and the USGS Land Change Science Program's LandCarbon program, and NOAA National Estuarine Research Reserve Science Collaborative NA14NOS4190145. R Sanders-DeMott was supported by a USGS Mendenhall Fellowship and partnership with Restore America's Estuaries.
    Keywords: Blue carbon ; Coastal wetland ; Dike ; Eddy covariance ; Impoundment ; Methane ; Net ecosystem exchange ; Phragmites ; Restoration ; Static chambers
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 6
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Lin, H. T., Hsieh, C. C., Repeta, D. J., & Rappé, M. S. Sampling of basement fluids via circulation obviation retrofit kits (CORKs) for dissolved gases, fluid fixation at the seafloor, and the characterization of organic carbon. Methodsx, 7, (2020): 101033, doi:10.1016/j.mex.2020.101033.
    Description: The advanced instrumented GeoMICROBE sleds (Cowen et al., 2012) facilitate the collection of hydrothermal fluids and suspended particles in the subseafloor (basaltic) basement through Circulation Obviation Retrofit Kits (CORKs) installed within boreholes of the Integrated Ocean Drilling Program. The main components of the GeoMICROBE can be converted into a mobile pumping system (MPS) that is installed on the front basket of a submersible or remotely-operated-vehicle (ROV). Here, we provide details of a hydrothermal fluid-trap used on the MPS, through which a gastight sampler can withdraw fluids. We also applied the MPS to demonstrate the value of fixing samples at the seafloor in order to determine redox-sensitive dissolved iron concentrations and speciation measurements. To make the best use of the GeoMICROBE sleds, we describe a miniature and mobile version of the GeoMICROBE sled, which permits rapid turn-over and is relatively easy for preparation and operation. Similar to GeoMICROBE sleds, the Mobile GeoMICROBE (MGM) is capable of collecting fluid samples, filtration of suspended particles, and extraction of organics. We validate this approach by demonstrating the seafloor extraction of hydrophobic organics from a large volume (247L) of hydrothermal fluids. • We describe the design of a hydrothermal fluid-trap for use with a gastight sampler, as well as the use of seafloor fixation, through ROV- or submersible assisted mobile pumping systems. • We describe the design of a Mobile GeoMICROBE (MGM) that enhances large volume hydrothermal fluid sampling, suspended particle filtration, and organic matter extraction on the seafloor. • We provide an example of organic matter extracted and characterized from hydrothermal fluids via a MGM.
    Description: We dedicate this work to Dr. James P. Cowen, who had envisioned and constructed the integrated instrumentation, GeoMICROBE, to monitor the sub-basement biosphere. We thank the chief scientists, captains, crews, and science teams on board R/V Atlantis cruises AT15-35, AT15-51, AT15-66, AT18-07, MSM20-5, AT26-03, and AT26-18, and the pilots and crews of ROV Jason II and HOV Alvin. We thank our student assistants, Natalie Hamada, Kathryn Hu, Ryan Matzumoto, Everette Omori, and Fan-Chieh Chuang. This work was supported by the National Science Foundation-Microbial Observatory Project (NSF-MCB06-04014 to J. P. Cowen), Center for Dark Energy Biosphere Investigations (C-DEBI; NSF award OCE-0939564 to M. S. Rappé), NSF award OCE-1260723 (to M. S. Rappé), and the Ministry of Science and Technology of Taiwan award (MOST 105-2119-M-002-034, MOST 107-2611-M-002-002, MOST 108-2611-M-002-006, and MOST109-2611-M-002-008 to H.-T. Lin). Ministry of Education (MOE) Republic of China (Taiwan) 109L892601 to H.-T. Lin. NSF award OCE-1634080 (to D. J. Repeta), the Simons Foundation-Simons Collaboration on Ocean Processes and Ecology (SCOPE) award 329108 (to D. J. Repeta), the Gordon and Betty Moore Foundation award 6000 (to D. J. Repeta). This paper is SOEST contribution number 11121, HIMB contribution 1804 and C-DEBI contribution number 543.
    Keywords: GeoMICROBE ; Hydrothermal fluid ; Crustal fluid ; Mobile pumping system ; Helium ; Methane ; Dissolved organic matter ; Extraction and preconcentration ; Deep subseafloor
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 7
    Publication Date: 2022-11-03
    Description: This paper presents new chemical and isotopic data on gases from deep oil and gas fields, bubbling gases, dissolved gases in groundwaters and dry seeps of the Southern Po River Basin (Emilia-Romagna, Italy), aiming to (i) characterize and differentiate the various types of deep natural gases; (ii) identify the source(s) of methane and light hydrocarbons in shallow aquifers and surface gas-rich emissions; (iii) propose a conceptual model of natural fluid migration pathways in the sedimentary prism of the Southern Po River Basin. Based on the isotopic composition of CH4 and C2–C4 n-alkanes, CH4/(C2H6+C3H8) ratio, relative proportion of the C7 hydrocarbons and relative concentration of cyclic compounds with respect to the total cyclic abundance, three main deep reservoirs of hydrocarbons are identified in the subsurface of the Southern Po River Basin: (1) microbial gas hosted in Pliocene-Pleistocene marine sediments, (2) thermogenic gas hosted in Miocene deposits and (3) thermogenic gas produced in Triassic carbonates. Helium isotopes of these deep fluids indicate an almost pure crustal origin (Rc/Ra values = 0.014–0.04), with negligible contributions from mantle-derived helium. A variable contribution of atmosphere-derived fluids is highlighted by low 4He/20Ne (down to 5.42) and 40Ar/36Ar (≤319.5) values. Comparison of chemical and isotopic signatures of deep and surficial hydrocarbon occurrences suggests that methane in shallow groundwaters or gas seeps is sourced by microbial gas migrating upward from deep Plio-Pleistocene reservoirs, with no detectable contributions of Triassic or Miocene thermogenic hydrocarbons. At shallow depths (roughly around 20–50 m.b.g.l.), Plio-Pleistocene microbial methane appears to be mainly stored in anoxic aquifers. However, where CH4 further migrates upwards and reaches aerobic environments (e.g., aquifers or soils), it readily undergoes a process of exothermic microbial oxidation mediated by methanotrophic bacteria. Where the structural architecture of the sedimentary sequence favors the migration of fluids, the methanotrophic biofilter is bypassed and CH4 is discharged through soil diffuse degassing or gas bubbling at water wells. We argue that microbial consumption might be able to bio-sequester significant amounts of Plio-Pleistocene deep-sourced methane in the form of CO2 and biomass. Such process might be widespread in the subsurface of the Southern Po River Basin and, possibly, in other foreland basins worldwide.
    Description: Published
    Description: 105981
    Description: 9T. Geochimica dei fluidi applicata allo studio e al monitoraggio di aree sismiche
    Description: JCR Journal
    Keywords: Methane ; Po river basin ; Emilia-romagna region ; Natural gas geochemistry ; Hydrocarbon source rocks ; Gas accumulation and migration ; Thermogenic gas ; Microbial gas
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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