Calculation of the stability and solubility of methane hydrate in seawater

Tishchenko, P. Ya.; Hensen, Christian; Wallmann, Klaus; Wong, C. S.

doi:10.1016/j.chemgeo.2005.02.008

Cited by 216 publications

(214 citation statements)

References 27 publications

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“…The aim of this simulation was to assess rates of fluid advection and bioirrigation. The site was chosen for simulation runs because gas hydrates were found within 40-100 cm sediment depth in several gravity cores within a radius of less than 1 km around Flare 2 and thus the lower boundary concentration of methane in equilibrium with gas hydrates (85 mM) could be estimated following Tishchenko et al (2005). This approach is consistent, for example, with estimates of in situ methane concentrations used for pore water modeling at gas hydrate-bearing cold seeps on Hydrate Ridge off Oregon, USA and at the Hikurangi Margin off New Zealand (Dale et al, 2010).…”

Section: Geochemical Modeling With "Cotrem"mentioning

confidence: 99%

Interaction between hydrocarbon seepage, chemosynthetic communities, and bottom water redox at cold seeps of the Makran accretionary prism: insights from habitat-specific pore water sampling and modeling

et al. 2012

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Abstract. The interaction between fluid seepage, bottom water redox, and chemosynthetic communities was studied at cold seeps across one of the world's largest oxygen minimum zones (OMZ) located at the Makran convergent continental margin. Push cores were obtained from seeps within and below the core-OMZ with a remotely operated vehicle. Extracted sediment pore water was analyzed for sulfide and sulfate concentrations. Depending on oxygen availability in the bottom water, seeps were either colonized by microbial mats or by mats and macrofauna. The latter, including ampharetid polychaetes and vesicomyid clams, occurred in distinct benthic habitats, which were arranged in a concentric fashion around gas orifices. At most sites colonized by microbial mats, hydrogen sulfide was exported into the bottom water. Where macrofauna was widely abundant, hydrogen sulfide was retained within the sediment.Numerical modeling of pore water profiles was performed in order to assess rates of fluid advection and bioirrigation. While the magnitude of upward fluid flow decreased from 11 cm yr −1 to <1 cm yr −1 and the sulfate/methane transition (SMT) deepened with increasing distance from the central gas orifice, the fluxes of sulfate into the SMT did not significantly differ (6.6-9.3 mol m −2 yr −1 ). Depth-integrated rates of bioirrigation increased from 120 cm yr −1 in the central habitat, characterized by microbial mats and sparse macrofauna, to 297 cm yr −1 in the habitat of large and few small vesicomyid clams. These results reveal that chemosynthetic macrofauna inhabiting the outer seep habitats below the core-OMZ efficiently bioirrigate and thus transport sulfate down into the upper 10 to 15 cm of the sediment. In this way the animals deal with the lower upward flux of methane in outer habitats by stimulating rates of anaerobic oxidation of methane (AOM) with sulfate high enough to provide hydrogen sulfide for chemosynthesis. Through bioirrigation, macrofauna engineer their geochemical environment and fuel upward sulfide flux via AOM. Furthermore, due to the introduction of oxygenated bottom water into the sediment via bioirrigation, the depth of the sulfide sink gradually deepens towards outer habitats. We therefore suggest thatin addition to the oxygen levels in the water column, which determine whether macrofaunal communities can develop or not -it is the depth of the SMT and thus of sulfide production that determines which chemosynthetic communities are able to exploit the sulfide at depth. We hypothesize that large vesicomyid clams, by efficiently expanding the sulfate zone down into the sediment, could cut off smaller or less mobile organisms, as e.g. small clams and sulfur bacteria, from the sulfide source.

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Section: Geochemical Modeling With "Cotrem"mentioning

confidence: 99%

Interaction between hydrocarbon seepage, chemosynthetic communities, and bottom water redox at cold seeps of the Makran accretionary prism: insights from habitat-specific pore water sampling and modeling

et al. 2012

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“…Based on the pump rate, methane concentration, and surface area of the sediment, a methane flux of 0.28 and 2.81 mmol m −2 d −1 was calculated for the LFC and HFC, respectively. These methane concentrations were lower than those potentially encountered under in situ conditions because the cores were not pressurized, resulting in lower methane fluxes (after Tishchenko et al, 2005;Karaca et al, 2012). After 260 d the first experimental phase ended and the pump rates were increased from low to high flow velocities for the LFC, and vice versa for the HFC.…”

Section: Sediment-flow-through Systemmentioning

confidence: 99%

“…Carbonate precipitation was implemented in the model (Krause et al, 2014) but was not used in the present study, since carbonate precipitation does not affect the efficiency of the microbial benthic methane filter within the studied timescales (several months to years). Because the sampling sites were located above the GHSZ , dissolved methane concentrations at the lower boundary were calculated from the equilibrium concentration with free gas (Tishchenko et al, 2005). Table 2 provides an overview of other boundary conditions as well as fitted, measured, and calculated parameters of the model.…”

Section: Numerical Modelmentioning

confidence: 99%

Efficiency and adaptability of the benthic methane filter at Quepos Slide cold seeps, offshore of Costa Rica

et al. 2015

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Abstract. Large amounts of methane are delivered by fluids through the erosive forearc of the convergent margin offshore of Costa Rica and lead to the formation of cold seeps at the sediment surface. Besides mud extrusion, numerous cold seeps are created by landslides induced by seamount subduction or fluid migration along major faults. Most of the dissolved methane migrating through the sediments of cold seeps is oxidized within the benthic microbial methane filter by anaerobic oxidation of methane (AOM). Measurements of AOM and sulfate reduction as well as numerical modeling of porewater profiles revealed a highly active and efficient benthic methane filter at the Quepos Slide site, a landslide on the continental slope between the Nicoya and Osa Peninsula. Integrated areal rates of AOM ranged from 12.9 ± 6.0 to 45.2 ± 11.5 mmol m −2 d −1 , with only 1 to 2.5 % of the upward methane flux being released into the water column.Additionally, two parallel sediment cores from Quepos Slide were used for in vitro experiments in a recently developed sediment-flow-through (SLOT) system to simulate an increased fluid and methane flux from the bottom of the sediment core. The benthic methane filter revealed a high adaptability whereby the methane oxidation efficiency responded to the increased fluid flow within ca. 170 d. To our knowledge, this study provides the first estimation of the natural biogeochemical response of seep sediments to changes in fluid flow.

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“…Methane concentrations determined during this study are well below saturation (1.2 mmol L -1 at 1 bar, 35 psu, 20°C; calc. after Tishchenko et al 2005) hence loss of methane due to pressure release during recovery of the lander can be excluded.…”

Section: Sommer Et Al Oxygen Controlled Benthic Flux Measurementsmentioning

confidence: 99%

Gas exchange system for extended in situ benthic chamber flux measurements under controlled oxygen conditions: First application—Sea bed methane emission measurements at Captain Arutyunov mud volcano

Sommer¹,

Türk²,

Kriwanek³

et al. 2008

Limnology & Ocean Methods

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Mass transfer rates of many gases, nutrients, and trace metals across the sediment water interface are dependent on environmental oxygen conditions. In this article, a novel gas exchange system for extended in situ flux and respiration measurements in benthic chambers under defined oxygen conditions is described. Integrated within a GEOMAR modular lander, the gas exchange system was used to perform in situ measurements of the total oxygen uptake and sea bed methane emission rates under constant oxygen conditions at Captain Arutyunov mud volcano (Gulf of Cadiz) in a water depth of 1320 m. During two separate lander deployments, the oxygen concentration within the benthic chambers was kept constant for 37 and 47 h, respectively. Under these conditions total oxygen uptake rate remained constant at 4.4 and 13.2 mmol m -2 d -1 . Seabed methane emission was low, in the range 0 to 0.2 mmol m -2 d -1. The system is suited for prolonged (days) in situ flux determinations under natural background oxygen conditions and offers a wide range of experimental applications.

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Calculation of the stability and solubility of methane hydrate in seawater

Cited by 216 publications

References 27 publications

Interaction between hydrocarbon seepage, chemosynthetic communities, and bottom water redox at cold seeps of the Makran accretionary prism: insights from habitat-specific pore water sampling and modeling

Interaction between hydrocarbon seepage, chemosynthetic communities, and bottom water redox at cold seeps of the Makran accretionary prism: insights from habitat-specific pore water sampling and modeling

Efficiency and adaptability of the benthic methane filter at Quepos Slide cold seeps, offshore of Costa Rica

Gas exchange system for extended in situ benthic chamber flux measurements under controlled oxygen conditions: First application—Sea bed methane emission measurements at Captain Arutyunov mud volcano

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