Atmospheric methane

About: Atmospheric methane is a research topic. Over the lifetime, 2034 publications have been published within this topic receiving 119616 citations.

Extreme Compaction Effects on Gas Transport Parameters and Estimated Climate Gas Exchange for a Landfill Final Cover Soil

Abstract: Landfill sites have been implicated in greenhouse warming scenarios as a significant source of atmospheric methane. In this study, the effects of extreme compaction on the two main soil-gas transport parameters, the gas diffusion coefficient (Dp) and the intrinsic air permeability (ka), and the cumulative methane oxidation rate in a landfill cover soil were investigated. Extremely compacted landfill cover soil exhibited negligible inactive soil-air contents for both Dp and ka. In addition, greater Dp and ka were observed as compared with normal compacted soils at the same soil-air content (e), likely because of reduced water-blockage effects under extreme compaction. These phenomena are not included in existing predictive models for Dp(e) and ka(e). On the basis of the measured data, new predictive models for Dp(e) and ka(e) were developed with model parameters (representing air-filled pore connectivity and water-blockage effects) expressed as functions of dry density (ρb). The developed Dp(e) and ka(e) m...

On the Rise: Methane in the Global Atmosphere

Abstract: (1985). On the Rise: Methane in the Global Atmosphere. Environment: Science and Policy for Sustainable Development: Vol. 27, No. 10, pp. 6-33.

Using stable isotopes of hydrogen to quantify biogenic and thermogenic atmospheric methane sources: A case study from the Colorado Front Range†

Abstract: Global atmospheric concentrations of methane (CH4), a powerful greenhouse gas, are increasing, but because there are many natural and anthropogenic sources of CH4, it is difficult to assess which sources may be increasing in magnitude. Here we present a dataset of δ2H-CH4 measurements of individual sources and air in the Colorado Front Range, USA. We show that δ2H-CH4, but not δ13C, signatures are consistent in air sampled downwind of landfills, cattle feedlots, and oil and gas wells in the region. Applying these source signatures to air in ground and aircraft samples indicates that at least 50% of CH4 emitted in the region is biogenic, perhaps because regulatory restrictions on leaking oil and natural gas wells are helping to reduce this source of CH4. Source apportionment tracers such as δ2H may help close the gap between CH4 observations and inventories, which may underestimate biogenic as well as thermogenic sources.

A gas chromatography/pyrolysis/isotope ratio mass spectrometry system for high‐precision δD measurements of atmospheric methane extracted from ice cores

Abstract: Air enclosures in polar ice cores represent the only direct paleoatmospheric archive. Analysis of the entrapped air provides clues to the climate system of the past in decadal to centennial resolution. A wealth of information has been gained from measurements of concentrations of greenhouse gases; however, little is known about their isotopic composition. In particular, stable isotopologues (dD and d 13 C) of methane (CH4) record valuable information on its global cycle as the different sources exhibit distinct carbon and hydrogen isotopic composition. However, CH4 isotope analysis is limited by the largesample size requiredand thedemandinganalysis as highprecision is required.Herewe present a highly automated, high-precision online gas chromatography/pyrolysis/isotope ratio monitoring mass spectrometry (GC/P/irmMS) technique for the analysis of dD(CH4). It includes gas extraction from ice, preconcentration, gas chromatographic separation and pyrolysis of CH4 from roughly 500g of ice with CH4 concentrations as low as 350ppbv. Ice samples with approximately 40mL air and only � 1nmol CH4 can be measured with a precision of 3.4%. The precision for 65mL air samples with recent atmospheric concentration is 1.5%. The CH4 concentration can be obtained along with isotope data which is crucial for reporting ice core data on matched time scales and enables us to detect flaws in the measurement procedure. Custom-made script-based processing of MS raw and peak data enhance the system’s performance with respect to stability, peak size dependency, hence precision and accuracy and last but not least time requirement. Copyright # 2010 John Wiley & Sons, Ltd.

Methane fluxes to the atmosphere from deepwater hydrocarbon seeps in the northern Gulf of Mexico

Abstract: [1] Three deepwater hydrocarbon seep sites in the northern Gulf of Mexico that feature near-seafloor gas hydrates, MC118 (depth = 900 m), GC600 (depth = 1250 m) and GC185 (depth = 550 m), were investigated during the Remote Sensing and Sea-Truth Measurements of Methane Flux to the Atmosphere (HYFLUX) study in July 2009. Continuous measurements of air and sea surface concentrations of methane were made to obtain high spatial and temporal resolution of the diffusive net sea-to-air fluxes. The atmospheric methane fluctuated between 1.70 and 2.40 parts per million (ppm) during the entire cruise except for high concentrations (up to 4.01 ppm) sampled during the end of the occupation of GC600 and the transit between GC600 and GC185. In conjunction with air-mass back trajectory analysis, these high concentrations are likely from a localized methane source to the atmosphere. Methane concentrations in surface seawater and methane net sea-to-air fluxes show high temporal and spatial variability within and between sites. The presence of ethane and propane in the surface seawater indicates a thermogenic source in the plume areas, suggesting the surface methane could be at least partly attributable to transport from the deepwater hydrocarbon seeps. Results from interpolations within the survey areas show the daily methane fluxes to the atmosphere at the three sites range from 0.744 to 300 mol d−1. Extrapolating the highest daily sea-to-air flux of methane to other deepwater seeps in the northern Gulf of Mexico suggests that the net diffusive sea-to-air flux from deepwater hydrocarbon seeps in this region is an insignificant source to the atmospheric methane.