Methane source

Methane (CH4), the Earth s third most important greenhouse gas (behind water vapor and CO2) is produced almost exclusively by terrestrial sources (see Chapters 7 and 11). Natural methane sources include anaerobic microbial... 

Longer ice-core records show that methane concentrations have varied on a variety of time scales over the past 220 000 years (Fig. 18-15) Qouzel et al, 1993 Brook et al, 1996). Wetlands in tropical (30° S to 30° N) and boreal (50° N to 70° N) regions are the dominant natural methane source. As a result, ice-core records for preanthropogenic times have been interpreted as records of changes in methane emissions from wetlands. Studies of modem wetlands indicate that methane emissions are positively correlated with temperature, precipitation, and net ecosystem productivity (Schlesinger, 1996). 

Figure 6-8 Experimental flammability diagram for methane. (Source C. V. Mashuga, Ph.D. dissertation (Michigan Technological University, 1999).

Clay samples were collected at areas of high-redox gradient at the edge of the Thorn-north ring and the Bean ring, which are H2S sourced and methane sourced, respectively. These samples were preserved under anoxic conditions and... 

Houweling S, Kaminski T, Dentener F, Lelieveld I, Heimann M. 1999. Inverse modeling of methane sources and sinks using the adjoint of a global transport model. Journal of Geophysical Research-Atmospheres 104 26137-26160. 

Methane is produced by bacteria under anaerobic conditions in wet environments such as wetlands, swamps and rice fields. It is also produced in the stomachs of cattle and by termites. Typical anthropogenic sources are from fossil fuels such as coal mining and as a byproduct in the burning of biomass. The latter sources are considerably heavier in C than the former. Recently, Keppler et al. (2006) demonstrated that methane is formed in terrestrial plants under oxic conditions by an unknown mechanism. The size of this methane source is stiU unknown but it might play an important role for the methane cycle. 

TABLE 14.1 Estimated Methane Sources during the Mid-1980s ... 

Wahlen, M., N. Tanaka, R. Henry, B. Deck, J. Zeglen, J. S. Vogel, J. Southon, A. Shemesh, R. Fairbanks, and W. Broecker, Carbon-14 in Methane Sources and in Atmospheric Methane The Contribution from Fossil Carbon, Science, 245, 286-290 (1989). 

Figure 2 Microreactor for parallel screening of catalysts for partial oxidation of methane. (Source D. Honicke, TU Chemnitz.)... 

Figure 4.15. Block diagram for formation and transport of methane in waterlogged country. Notation FlCHi is the methane flux across the atmosphere/water body interface F2CHi is the oxidation of methane in aerobic zones FCH is the intensity of the methane source M is methane concentration.

Thus, estimation of flux Fxcm as a function of a given territory with account of the natural and anthropogenic processes taking place there requires first of all a detailed inventory of methane sources as well as natural and technogenic systems functioning on this territory. Examples of such an inventory as the one given above serve as the basis for development of studies in this direction. 

Table 9.2. Global methane sources and sinks fluxes in units of 10 2 moles C y. ...

Khalil M. A. K. (ed.) (1993) Atmospheric Methane Sources, Sinks and Role in Global Change, In Proceedings of the NATO Advanced Science Workshop on the Atmospheric Methane Cycle Sources, Sinks, Distributions, and Role in Global Change, Held at Mt. Hood near Portland, OR, Oct. 7-11, 1991. Springer, Berlin. 

There is also evidence for the presence of methanotrophs in the 2.8 Ga old Mount Roe palaeosol. This contains highly fractionated organic carbon, probably recording the activity of methanotrophs living near ephemeral ponds this implies that significant biological methane sources existed in the late Archean (Rye and Holland, 2000). Oil is also present in some Archean sandstone (Dutkeiwicz et al, 1998, Rasmussen and Buick, 2000). 

Minami K. and Takata K. (1997) Atmospheric methane sources, sinks, and strategies for reducing agricultural emissions. Water Sci. Technol. 36, 509-516. 

The involvement of folate in the methane fermentation is less clear. 5-Methyltetrahydrofolate is used only moderately as a methane source by extracts of M. barkeri 14). No folate-containing factor has been demon-... 

Fig. 5.61 Methane sources based on isotopic composition and relative abundance (abiogenic = derived from mande C02 ...

Global strength of biological methane sources according to Ehhalt (1974)... 

The simplest alkane is methane (CH4). Methane oxidation is the essential chemistry of the background troposphere (Logan et al., 1981 Thompson and Cicerone, 1986). Ice-core records show that methane concentrations in the atmosphere have more than doubled since preindustrial times (Khalil and Rasmussen, 1987), reaching a rate of increase of 1% yr-1 in the last decade (Khalil et al., 1989). Methane is emitted to the atmosphere by ruminants, wetlands, tundra, open waters, termites, rice paddies, biomass burning, natural gas production, and coal mining [see Jacob (1991) for a review of the literature on methane sources] the principal sink of CH4 is reaction with OH. 

Sheppard, J. C., H. Westberg, J. F. Hopper, K. Ganesan, and P. Zimmerman (1982). Inventory of global methane sources and their productions rates. J. Geophys. Res. 87, 1305-1312. Shneour, E. A. (1966). Oxidation of graphitic carbon in certain soils. Science 151, 991-992. Shugard, W. J., R. H. Heist, and J. J. Reiss (1974). Theory of water phase nucleation in binary mixtures of water and sulfuric acid. J. Chem. Phys. 61, 5298-5307. 

Figure 3.3-2 Pressure-enthalpy diagram for methane. Source W. C. Reynolds, Tlieniwdv-namic Properties in SI, Department of Mechanical Engineering, Stanford University, Stanford, CA, 1979. Used with permi.ssion.) (This figure appears as an Adobe PDF file on the CD-ROM accompanying this book, and may be enlarged and printed for easier reading and for use in solving problems.)...

S. E, Chapin, F. S., Chapin, M. C., Trumbore, S., and Tyler, S. (1997). North Siberian lakes—A methane source fueled by Pleistocene carbon. Science 111, 800-802. 

Wahlen, M., Tanaka, N., Henry, R., Deck, B., Zeglen, J., Vogel, J. S., Southon, J., Shemesh, A., Fairbanks, R., and Broecker, W., Carbon-14 in methane sources and in atmospheric methane the contribution from fossil carbon. Science, 245, 236-245, 1989. 

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