Showing papers on "Methane published in 1982"

Methanothrix soehngenii gen. nov. sp. nov., a new acetotrophic non-hydrogen-oxidizing methane bacterium

Abstract: A new genus of methanogenic bacteria is described, which was isolated from a mesophilic sewage digester. It is most probably the filamentous bacterium, earlier referred to asMethanobacterium soehngenii, “fat rod” or “acetate organism”. The single non-motile, non-sporeforming cells are rod-shaped (0.8×2 μm) and are normally combined end to end in long filaments, surrounded by a sheath-like structure. The filaments form characteristic bundles.Methanothrix soehngenii decarboxylates acetate, yielding methane and carbon dioxide. Other methanogenic substrates (H2−CO2, formate, methanol, methylamines) are not used for growth or methane formation. Formate is split into hydrogen and carbon dioxide. The temperature optimum for growth and methane formation is 37°C and the optimal pH range is 7.4–7.8. Sulfide and ammonia serve as sulfur and nitrogen source respectively. Oxygen completely inhibits growth and methane formation, but the bacteria do not loose their viability when exposed to high oxygen concentrations. 100 mg/l vancomycin showed no inhibition of growth and methanogenesis. No growth and methane formation was observed in the presence of: 2-bromoethanesulfonic acid, viologen dyes, chloroform, and KCN. The bacterium has a growth yield on acetate of 1.1–1.4 g biomass per mol acetate. The apparent “K S ” of the acetate conversion system to methane and carbon dioxide is 0.7 mmol/l. The DNA base composition is 51.9 mol% guanine plus cytosine. The nameMethanothrix is proposed for this new genus of filamentous methane bacterium. The type species,Methanothrix soehngenii sp. nov., is named in honor of N. L. Sohngen.

Methane production and simultaneous sulphate reduction in anoxic, salt marsh sediments

Abstract: It has been generally believed that sulphate reduction precludes methane generation during diagenesis of anoxic sediments1,2. Because most biogenic methane formed in nature is thought to derive either from acetate cleavage or by hydrogen reduction of carbon dioxide3–6, the removal of these compounds by the energetically more efficient sulphate-reducing bacteria can impose a substrate limitation on methanogenic bacteria7–9. However, two known species of methanogens, Methanosarcina barkeri and Methanococcus mazei, can grow on and produce methane from methanol and methylated amines10–13. In addition, these compounds stimulate methane production by bacterial enrichments from the rumen11,14 and aquatic muds13,14. Methanol can enter anaerobic food webs through bacterial degradation of lignins15 or pectin16, and methylated amines can be produced either from decomposition of substances like choline, creatine and betaine13,14 or by bacterial reduction of trimethylamine oxide17, a common metabolite and excretory product of marine animals. However, the relative importance of methanol and methylated amines as precursors of methane in sediments has not been previously examined. We now report that methanol and trimethylamine are important substrates for methanogenic bacteria in salt marsh sediments and that these compounds may account for the bulk of methane produced therein. Furthermore, because these compounds do not stimulate sulphate reduction, methanogenesis and sulphate reduction can operate concurrently in sulphate-containing anoxic sediments.

Methane flux in the Great Dismal Swamp

Abstract: The paper reports measurements made over a 17-month period of the methane flux in the Great Dismal Swamp of Virginia in light of the potential implications of variations in atmospheric methane concentrations. Gas flux measurements were made by a technique combining a gas filter correlation IR absorption analyzer with improved sampling chambers that enclose a soil area under conditions ranging from totally flooded soils to dry soils resulting from drought conditions. Methane emissions are found to range from 0.0013 g CH4/sq m per day to 0.019 g CH4/sq m per day, depending on temperature and season, when the soil is in a waterlogged state. During drought conditions, the peat soils in the swamp were a sink for atmospheric methane, with fluxes from less than 0.001 to 0.005 g CH4/sq m per day and decreasing with decreasing temperature. Results illustrate the potential complexity of the processes which regulate the net flux of methane between wetland soils and the atmosphere.

Solubilities of inert gases and methane in H2O and in D2O in the temperature range of 300 to 600 K

Abstract: The solubility of inert gases and methane in H2O and D2O has been measured between room temperature and 600 K. The calculation of Henry’s constants kH, from the solubility data is analyzed in detail; if due account is taken of the nonideality in the gas phase, they can be determined unambiguously up to 520 K. Above this temperature, the ambiguity in kH increases sharply as contributions of third and higher order virial coefficients to the equation of state of the gaseous mixture become more important. The differences of gas solubilities in light and heavy water essentially disappear above the temperature of minimum solubility of the gases. The characteristic thermodynamic features of the aqueous solutions of gases (i.e., large values of −ΔS02 and of ΔC0p2) are still present at 520 K. It is shown that mean‐field theories can account for the

Termites: a potentially large source of atmospheric methane, carbon dioxide, and molecular hydrogen.

Abstract: Termites may emit large quantities of methane, carbon dioxide, and molecular hydrogen into the atmosphere. Global annual emissions calculated from laboratory measurements could reach 1.5 x 10(14) grams of methane and 5 x 10(16) grams of carbon dioxide. As much as 2 x 10(14) grams of molecular hydrogen may also be produced. Field measurements of methane emissions from two termite nests in Guatemala corroborated the laboratory results. The largest emissions should occur in tropical areas disturbed by human activities.

Multiple-phase equilibria in hydrates from methane, ethane, propane and water mixtures

Abstract: Phase-equilibrium conditions for multicomponent hydrocarbon-water mixtures were experimentally determined, demonstrating that both structure I and structure II hydrates can form from a single mixture. Model parameters were optimized to allow prediction of the hydrate structure, and prediction of the pressure and temperature of hydrate formation for the experimental mixtures.

Role of Diffusion in Primary Migration of Hydrocarbons

Abstract: The following effective diffusion coefficients D(cm2/sec) were determined for the diffusion of light hydrocarbons through the water-saturated pore space of shales: methane (2.12 × 10-6), ethane (1.11 × 10-6), propane (5.55 × 10-7), iso-butane (3.75 × 10-7), n-butane (3.01 × 10-7), n-pentane (1.57 × 10-7), n-hexane (8.20 × 10-8), n-heptane (4.31 × 10-8), and n-decane (6.08 × 10-9). On the basis of these new data, a deterministic, dynamic model was set up to simulate the diffusive transport of light hydrocarbons (C1 to C10) from source rocks. For eight documented source-rock units, representing a wid range of geologic conditions (maturities of 0.40 to 1.35% mean vitrinite reflectance; oil- to gas-prone kerogens), the cumulative amounts of hydrocarbons escaping with time were calculated. Thus, it was shown that diffusion represents an effective process for primary migration of gas but not for oil. The rate of mass transport for gas from source rocks with geologic time can be sufficiently high to account for the origin of commercial-size gas fields. For example, a cumulative amount of 109 kg of methane (1.5 × 109 std m3 or 5.3 × 1010 scf) has escaped by diffusion in 540,000 years from a certain volume (1,000 km2 by 200 m thick) of a high-mature gas-prone Mesozoic source rock in western Canada. The origin of hydrocarbon accumulations with high gas-to-oil ratios in low-mature sediments in geologically young basins ("early gases and condensates") can be explained by an early phase of primary migration predominantly based on diffusion. During the initial stages of the accumulation history of those fields (extending up to millions of years under certain conditions), the reservoir gas changes with geologic time from a methane-rich to a wet-gas composition. At low-maturity levels (below about 0.6% Rm), even oil-prone source rocks yield methane-rich light-hydrocarbon mixtures by migration through diffusion. Compositional trends among reservoir gases of several multiple-pay gas fields in Louisiana represent evidence for diffusive transport of hydrocarbons. The variation in gas composition between the individual pay zones is controlled by increasing distances of diffusive transport of the hydrocarbons from a uniform source rock at depth to their present accumulation sites. In the shallow pay zones, compounds of high diffusivity are enriched. For example, in the Sligo gas field of Louisiana, the methane/ethane and the iso-butane/n-butane ratios increase from 10.2 to 36.0 and from 0.86 to 1.13, respectively, from the deepest to the shallowest of the five productive reservoir sands, which are spread over a a depth interval of 5,500 ft (1,676 m). Diffusion of light hydrocarbons in the subsurface can also have economically adverse effects. For example, existing gas accumulations can be destroyed by dissipation. The rate of this destruction was calculated for the Harlingen gas field, Holland. By diffusive loss through 400 m of shale cap rock, the initial amount of methane in place of 1.93 × 109 std m3 (6.8 × 1010 scf) is reduced by one half over a period of 4.5 million years. This leads us to propose the concept that large gas accumulations can persist through extended periods of geologic time only as dynamic systems reaching some kind of steady-state equilibrium between diffusive loss through the cap rock and continuous replenishment from the source rock.

Nitrated polycyclic aromatic hydrocarbons in urban air particles.

Abstract: The organic extract of urban air particles from St. Louis, MO, was fractionated by high-performance liquid chromatography. The moderately polar fraction was characterized by gas chromatography-electron impact and methane negative ion chemical ionization mass spectrometry. The compounds identified in the sample included nitronaphthalene, 9-nitroanthracene, 3-nitrofluoranthene, 1-nitropyrene, arenecarbonitriles, and several polycyclic ketones, quinones, and anhydrides. These studies represent the first mass spectrometric evidence of nitroaromatics in urban air particles.

The carbon isotopic composition of atmospheric methane

Abstract: Recent measurements of the carbon isotopic abundance of atmospheric methane give a value of δ(13C/12C) = −47.0 ± 0.3‰, which is significantly different from earlier values measured by others between 1950 and 1970. The isotopic composition of various sources and the possibility of a temporal trend are discussed. The average methane concentration measured was 1.66 ppm, which is in accord with the increase in concentration since 1965–1970 observed in other studies.

Is the CH 4 , H 2 and CO venting from submarine hydrothermal systems produced by thermophilic bacteria?

Abstract: Submarine hydrothermal vents are a major source of methane to the oceans1,2 The methane, as well as H2 and CO, are generally believed to result from degassing of the mantle or from abiogenic water–rock reactions1, a conclusion supported by direct correlations between 3He and CH4, and generally between CH4, H2 and CO and dissolved silicate in hydrothermal waters2,3 An alternative source for these gases might be microbiological This would imply that active bacterial communities exist in deep-sea hot water environments, some of which have temperatures exceeding 100 °C; this inference is without precedent We have now found that the super-heated waters emanating from sulphide chimneys at 21 °N along the East Pacific Rise and samples from the sulphide chimneys themselves harbour complex communities of bacteria capable of growing with generation times of 37–65 min, producing CH4, CO, H2 and traces of N2O in media containing S2O2−3, Mn2+ and Fe2+ as energy sources, and oxidizing CH4, at 100 ± 2 °C at 1 atm These microbial communities consist of three to five morphologically distinct types and include both oxidative and anaerobic species These mixed cultures will not grow at temperatures below 70–75 °C Even though some of the communities originated from water of temperatures >300 °C, it is not known if they can grow and produce CH4, CO and H2 in super-heated waters kept liquid due to hydrostatic pressure The discovery of these obligately thermophilic, gas-producing and consuming bacterial communities associated with submarine volcanic environments has interesting and important implications for prokaryotic evolution, marine geochemistry, industrial microbiology and exobiology

Inventory of global methane sources and their production rates

Abstract: On the basis of 17 ecosystems, it is estimated that 9.1×1014 g CH4/year are emitted into the atmosphere from the biosphere. Enteric fermentation in animals and humans, decomposition of organic wastes, and biomass burning contribute an additional 2.0×1014 g CH4/yr. Various fossil sources emit another 1×1014 g CH4/yr. When all sources are considered, they emit 12.1×1014 g CH4 each year. As with earlier inventories, this study indicates that the fossil methane contribution is less than 10% of the total annual global production rate. Chemical kinetic relationships are established between the bacteriamediated anaerobic decomposition of humic matter, the mean residence time (MRT) of humus, and methane fluxes. These equations and the 14C specific activity are used to obtain an average MRT of 1365 years for the earth's 1.8×1018 grams of humic carbon. Use of the global methane production rate and the concentration of atmospheric methane results in an average 3.3 year residence time and an average global hydroxyl radical concentration of 2.7×106 per cm3.

Methane from cattle waste: Effects of temperature, hydraulic retention time, and influent substrate concentration on kinetic parameter (k)

Abstract: The effects of temperature (35 and 55 degrees C), influent volatile solids (VS) concentration (S(0) = 43, 64, 82, 100, and 128 kg VS/m(3)) and hydraulic retention time (HRT = 4, 5, 8, 10, 15, and 25 days) on methane (CH(4)) production from cattle waste were evaluated using 3-dm(3) laboratoryscale fermentors. The highest CH(4) production rate achieved was 6.11 m(3) CH(4) m(-3) fermentor day(-1) at 55 degrees C, four days HRT, and S(0) = 100 kg VS/m(3). Batch fermentations showed an ultimate CH(4) yield (B(0)) of 0.42 m(3) CH(4)/kg VS fed. The maximum loading rates for unstressed fermentation were 7 kg VS m(-3) day(-1) at 35 degrees C and 20 kg VS m(-3) day(-1) at 55 degrees C. The kinetic parameter (K, an increasing K indicates inhibition of fermentation) increased exponentially as S(0) increased, and was described by: K = 0.8 + 0.0016 e(0.06S(0) ). Temperature had no significant effect on K for S(0) between 40 and 100 kg VS/m(3). The above equation predicted published K values for cattle waste within a mean standard error of 7%.

Chemical kinetic prediction of critical parameters in gaseous detonations

Abstract: A theoretical model including a detailed chemical kinetic reaction mechanism, for hydrogen and hydrocarbon oxidation is used to examine the effects of variations in initial pressure and temperature on the kinetic induction properties of gaseous fuel-oxidizer mixtures. Fuels considered include hydrogen, methane, ethane, ethylene, and acetylene. Induction lengths are computed for initial pressures between 0.01 and 10.0 atmospheres and initial temperatures between 200 K and 500 K. These induction lengths are then compared with available experimental data for critical energy and critical tube diameter for initiation of spherical detonation, as well as detonation limits in linear tubes. Combined with earlier studies concerning variations in fuel-oxidizer equivalence ratio and degree of dilution with N2, the model provides a unified treatment of fuel oxidation kinetics in detonations.

Partial oxidation of methane by nitrous oxide over molybdenum oxide supported on silica

Abstract: Methanol and formaldehyde were formed as major products at a moderate conversion level (16%) in the partial oxidation of methane by nitrous oxide in the presence of water over molybdenum oxide supported on silica.

Methane on Triton: Physical State and Distribution.

Abstract: Abstract Infrared spectrophotometric measurements of Neptune's satellite Triton obtained between 1980 and 1982 in the spectral range 0.8–2.5 μm show six individual absorption bands attributable to methane. An additional band in the Triton data is not methane. The Triton spectral data conform more closely to a laboratory spectrum of frozen methane than to a synthetic spectrum of methane gas computed for conditions of low temperature expected at the satellite. Additionally, the strength of the bands vary with Triton's orbital position. The data thus suggest that methane in the ice phase is mostly responsible for the bands in Triton's spectrum, and that the ice is distributed nonuniformly around the satellite's surface.

Process for recovery of natural gas liquids from a sweetened natural gas stream

Abstract: A sweet natural gas stream is stripped of water and hydrocarbon components heavier than methane to substantially any selected degree by countercurrent extraction with polyethylene glycol dimethyl ether while at pipeline pressures The stripped natural gas meets pipeline specifications The rich polyethylene glycol dimethyl ether is let down in pressure through selected successive stages which respectively isolate fractions that are rich in ethane, propane, butanes, and hydrocarbons heavier than butane Lastly, waste water is removed from the solvent to regenerate the polyethylene glycol dimethyl ether The separated gas streams of ethane, propane, butanes, and hydrocarbons heavier than butanes are individually compressed, combined, condensed and cooled to form a natural gas liquid stream, suitable for pipeline shipment A sour natural gas stream may also be treated in the same equipment if adequate solvent quantities are employed to remove water and acidic components from the sour gas and if a sweetening unit is added to remove the acidic components from the combined liquid hydrocarbon stream

Field observations of methane concentrations and oxidation rates in the southeastern bering sea.

Abstract: Measurements of methane oxidation rates were made in southeastern Bering Sea water samples with [14C]methane. The rate at which 14CO2 evolved from samples exposed to one methane concentration was defined as the relative methane oxidation rate. Rate determinations at three methane concentrations were used to estimate methane oxidation kinetics. The rate constant calculated from the kinetics and the observed methane concentration in the same water sample were used to calculate an in situ methane oxidation rate and the turnover time. First-order kinetics were observed in essentially all experiments in which methane oxidation kinetics were measured. Relative methane oxidation rates were greater in waters collected at inshore stations than at the offshore stations and were greater in bottom samples than in surface samples. In most water samples analyzed, there was essentially no radioactivity associated with the cells. The resulting respiration percentages were therefore very high with a mean of >98%. These data suggest that most of the methane was used by the microflora as an energy source and that very little of it was used in biosynthesis. The relative methane oxidation rates were not closely correlated with methane concentrations and did not appear to be linked to either oxygen or dissolved inorganic nitrogen concentrations. However, there was a significant correlation with relative microbial activity. Our data suggest that the methane oxidizers were associated with the general microbial heterotrophic community. Since these organisms did not appear to be using methane as a carbon source, it is unlikely that they have been isolated and identified as methane oxidizers in the past.

Gas hydrates in ocean bottom sediments

Abstract: Gas hydrates belong to a special category of chemical substances known as inclusion compounds. An inclusion compound is a physical combination of molecules in which one component becomes trapped inside the other. In gas hydrates, gas molecules are physically trapped inside an expanded lattice of water molecules. The pressures and temperatures beneath Arctic water depths greater than 1,100 ft (335 m) and subtropical water depths greater than 2,000 ft (610 m) are suitable for the formation of methane hydrate. Theoretical depths to the base of a gas hydrate layer in ocean bottom sediments are determined by assuming: (1) a constant hydrostatic pressure gradient, (2) two typical hydrothermal gradients, (3) variable geothermal gradients, and (4) pure methane hydrated with conna e seawater. In addition to pressure and geothermal gradient, other variables affecting the stability of gas hydrate are examined. These variables are hydrothermal gradient, sediment thermal conductivity, heat flow, hydrate velocity, gas composition, and connate water salinity. If these variables are constant in a lateral direction and the above assumptions are valid, a local geothermal gradient can be determined if the depth to the base of a gas hydrate is known. The base of the gas hydrate layer is seen on seismic profiles as an anomalous reflection nearly parallel to the ocean bottom, cross-cutting geologic bedding plane reflections, and generally increasing in sub-ocean bottom time with increasing water depth. The acoustic impedance is a result of the relatively fast velocity hydrate layer overlying slower velocity sediments. In addition, free gas may be trapped beneath the hydrate, thereby enhancing the reflection.

Dissolved hydrogen, carbon monoxide, and methane at the CEPEX site

Abstract: Concentrations of three trace gases—H2, CO, and CH4—were measured in the upper waters and in the near-surface atmosphere at the Controlled Ecosystem Population Experiment (CEPEX) site in Saanich Inlet, B.C., Canada. The upper 20 m of water contained these reduced gases at concentrations significantly higher than atmospheric equilibrium values in the presence of high levels of dissolved oxygen. Because vertical mixing was quite weak within the CEPEX container, distributions of CO, CH4, and H2 were most strongly influenced by in situ production and consumption. Concentrations of hydrogen and carbon monoxide were generally highest at or near the surface in all containers. Daily cycles of CO concentrations in the CEPEX enclosures and in the water outside the enclosures were observed. A similar, but less pronounced, H2 cycle was seen only inside the enclosure. In the CEPEX container that received no nutrient additions, a methane maximum was commonly found at depths between 8 and 12m. Methane concentrations and distributions in this container showed little change over a period of several weeks. Methane distribution did undergo significant change in the nutrient enriched containers. In Saanich Inlet, the CH4 maxima occurred deeper in the water column. No excess of H2 or CO was found in this methane-rich deeper water. Within the containers, changing hydrogen concentrations seem related to phytoplankton abundance, but the hydrogen distribution suggests zooplankton play a role. Carbon monoxide abundance varies with the amount of illumination received by the waters. Probably a variety of factors influence the distribution of each of the gases. Seawater samples collected at the site and incubated in dark containers, at in situ temperature, showed rapid decreases of CO and H2 levels to below air equilibrium. Carbon monoxide in these incubated samples reached subequilibrium levels within 12 hours. Shallow and deep water samples that had been briefly exposed to sunlight during sample handling subsequently showed higher levels of dissolved CO than did samples that were carefully shielded from outside light. Care is needed to avoid such artifacts when studying diurnal variations in dissolved CO.

Dissolved hydrogen and methane in Saanich Inlet, British Columbia

Abstract: Hydrogen, methane, and relevant microbiological and hydrographic observations were made to study the processes responsible for the observed distributions of the gases in Saanich Inlet, a seasonally anoxic fjord. Concentrations of surface waters were up to 22 (H2) and 13 (CH4) times atmospheric saturation. Below the surface hydrogen fell to undersaturation, rising to above saturation in the anoxic layer. Methane increased to a maximum at 30 m, and after a minimum at 125 m, increased greatly in the anoxic layer. Microbes cultured from inlet surface water produced hydrogen under experimental conditions, not by nitrogen fixation but while apparently denitrifying. Large numbers of protozoa present may provide anaerobic microniches for hydrogen and methane production, as might the intestinal tracts of the large populations of higher organisms in the inlet. Methane profiles in the upper 50 m are typical of waters outside the inlet, indicating regional sources and sinks. Hydrogen production and consumption rates, inferred to be rapid in the anoxic waters, nearly balance so that only slight increases in hydrogen occur there.

CH 4 , H 2 , CO and N 2 O in submarine hydrothermal vent waters

Abstract: Hydrothermal circulation systems of mid-ocean ridges profoundly influence the chemistry of the oceans and the oceanic crust1–3. This has been demonstrated for several major and minor constituents of seawater4 and trace metals5. In addition, several volatile compounds including helium6,7 as well as methane and hydrogen8–11 are introduced to the sea floor in concentrations greatly exceeding that of ambient bottom water. We present here our measurements of concentrations of methane, hydrogen, carbon monoxide and nitrous oxide in the hydrothermal vent waters from the Galapagos Spreading Centre (GSC). The relationships of these constituents to silicon were unique for each vent field, with nitrous oxide at East of Eden being the only instance of negative correlation. These gases could serve as important energy sources, in addition to hydrogen sulphide, for the chemosynthetic bacteria which support the extensive and diverse animal population living in these environments12,13.