Deep clathrate

However, the starch solution should not be omitted completely since the color difference between the chromatogram zones, in which the iodine is reduced to colorless iodide according to the iodine azide reaction mentioned above, and the background colored brown by unreacted iodine is considerably less than the difference in color between the deep blue background provided by the starch-iodine clathrate complex and the pale chromatogram zones. 

Some gases have subsurfece sources that are related to physical phenomena, such as inputs from the introduction of hydrothermal fluids in bottom waters or release from warming sediments. The latter is a source of methane, which can occur in sediments in a solid phase called a clathrate hydrate. Biogeochemical reactions in sediments can also produce gases that diffuse from the pore waters into the deep sea. 

Clathrate hydrates Solid cages of water that form around small gas molecules such as methane, hydrogen, or carbon dioxide under conditions of high pressure and low temperature such as found on the deep sea floor and within the sediments. 

Natural hydrate obtained from the deep sea core at Blake Ridge, off the eastern coast of USA, was irradiated by y-rays at 77K.131 A signal at g =2.0014 was observed in addition to those due to H° and CHj-. Preliminary work indicates the interaction of CH3 with nearby H20 in the clathrate and/or paired... 

Clathrate hydrates have been found to occur naturally in large quantities. Around 120 X 10 m (at STP) of methane is estimated to be trapped in deposits of the deep ocean floor [10]. Clathrate hydrates are also suspected to occur in large quantities on some outer planets, moons, and trans-Neptunian objects [11]. In the petroleum industry, hydrocarbon clathrate hydrates are a cause of problems because they can form inside gas pipelines, often resulting in plugging. Deep sea deposition of carbon dioxide clathrate hydrate has been proposed as a method to remove this greenhouse gas from the atmosphere and control climate change [12]. 

As the readily accessible oil and gas reserves are becoming exhausted, it is necessary to be able to consider oil fields prone to more severe conditions and from more remote locations. This includes oil fields previously considered to be uneconomical, like those in deep ocean environments, which are subjected to high pressures and low temperatures. Such extreme conditions promote the formation of a solid non-stoichiometric compound of gas and water - the so-called clathrate of natural gas, or more commonly known as gas hydrates [1]. When hydrates form, they block transmission lines, causing important economic losses due to the production stoppage. 

Methane hydrate is a clathrate compound of water molecules surrounding a methane molecule. Natural methane hydrate is found in permafrost and deep-sea sediment, and has recently attracted much attention as a potential new resource because of the large amount of deposits. Methane hydrate is also expected as new materials for gas storage and transportation due to its unique properties called anomalous preservation, quite slow dissociation from -40 to -10°C at atmospheric pressure, despite of its dissociation over -80"C. ... 

Air bubbles and clathrate hydrates in polar ice cores have attracted considerable interest because they provide the most direct record of past atmospheric gas compositions (e.g., Raynaud et However, the processes of air clathration in polar ice sheets should be taken into account when considering gas analyses. It is known that extreme fractionation of gases in air inclusions occurs when air bubbles change into clathrate hydrates by the diffusive mass transfer of air molecules between bubbles and hydrates. To estimate the effects of hydrate formation on the distribution of atmospheric gases in deep ice, it is essential to understand the structure and physical properties of natural air hydrates. 

Polar deep ice. Polar deep ice is made of snow under a compressing process. The dielectric properties of polar ice core samples have been reported as having small values of relaxation time rand activation energy.The observation of small rvalues for the core ice samples suggests that Bjerrum defects are more numerous in polar ice than in ordinary ice. The impurity concentration of polar ice is not sufficiently high to decrease the rvalue the HCl concentration is about 2x10 mol/1 for Byrd core ice. Since we know that polar deep ice has structures of clathrate gas hydrate, imperfection in the structures and the existence of gas molecules in the ice lattice seem to affect the dielectric properties.It is well known that the dielectric properties of ice samples derived from polar deep ice that has melted and refrozen are similar to those of ordinary ice. ... 

Buffet, B., and Archer, D., 2004. Global inventory of methane clathrate sensitivity to changes in the deep ocean Earth and Planetary Science Letters, 227 185-199. 

Hesse, R., and Harrison, W.E., 1981. Gas hydrates (clathrates) causing pore-water freshening and oxygen istope fractionation in deep-water sedimentary... 

One of the best-characterized links between marine and terrestrial paleoclimate concerns the Paleocene-Eocene thermal maximum (PETM). High-resolution marine cores delineated a rapid drop in benthic foraminifera 5 C and 5 0 at 55 Ma. The drop corresponds to a deep-sea temperature rise of 5-6°C in ten thousand years or less (Kennett and Stott 1991, Bralower et al. 1995, Thomas and Shackleton 1996). The cause is now inferred to be catastrophic methane release from clathrates on the continental margins (Dickens et al. 1995, 1997 Dickens 1999). Because methane is a greenhouse gas and has an extremely low value (—60%o), a large release would affect both temperature (oxygen isotopes) and carbon isotopes. 

Interest in clathrate hydrates was sparked again when it was realized that hydrates might exist naturally in the geosphere, and when this hypothesis was subsequently confirmed. This includes "air" hydrates deep inside glaciers and natural gas hydrates, both under the permafrost and offshore on the continental margins (see Fig. On a more speculative note, it was also... 

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