Methane Concentration Profiles Research Articles

Stratospheric methane concentration profiles measured during the Balloon Intercomparison Campaigns

Following the Balloon Intercomparison Campaigns carried out from the NSBF, Palestine, Texas, in the fall of 1982 (BIC1) and spring of 1983 (BIC2), three instruments have reported infrared measurements (one in emission and two in absorption) from which results on the concentration of methane between 20 and 40 km altitude have been deduced. While the absorption-retrieved concentration profiles are in excellent agreement, the results from the emission measurements are significantly lower. Recent methane profiles obtained by satellite and from Spacelab 1 are in satisfactory agreement with the absorption data reported here.

Soil atmosphere concentration profiles and methane emission rates in the restoration covers above landfill sites: Equipment and preliminary results

In an investigation into the microbial oxidation of methane in soils, a simple and robust sampling device for the collection of small samples of soil atmosphere was used. The method has the potential for determining small-scale variations in depth profiles of gases, without the potential problems of sample migration during collection. Measurements of methane concentration profiles at a number of points along a transect in a restored landfill site in Essex correlated well with the measured emission of landfill gas from the surface of the soil. Emissions were only detected where methane concentrations reached the soil surface.

Soil Atmosphere Concentration Profiles and Methane Emission Rates in the Restoration Covers Above Landfill Sites: Equipment and Preliminary Results

In an investigation into the microbial oxidation of methane in soils, a simple and robust sampling device for the collection of small samples of soil atmosphere was used. The method has the potential for determining small-scale variations in depth profiles of gases, without the potential problems of sample migration during collection. Measurements of methane concentration profiles at a number of points along a transect in a restored landfill site in Essex correlated well with the measured emission of landfill gas from the surface of the soil. Emissions were only detected where methane concentrations reached the soil surface.

The surface reaction rate of methane on a platinum catalyst.

An experimental study was carried out for the surface reaction of methane on the platinum catalyst which is placed on the stagnation point of a circular cylinder. By paying much attention to the reproducibity of the catalyst activity, a stable and well activated catalytic surface was obtained. by measuring the methane concentration profile near the catalytic surface, diffusion flux to the surface and surface concentration of methane were obtained. From these results, the dependence of surface reaction on surface temperature and surface methane concentration was made clear. The rate of surface reaction on surface shows a linear dependence of surface reaction rate on temperature can be represented by the Arrhenius' equation. Activation energy for this surface reaction was determined to be 80 kJ/mol.

A model for coupled sulfate reduction and methane oxidation in the sediments of Saanich Inlet

A methane-sulfate coupled reaction diffusion model has been developed to describe the inverse relationship commonly observed between methane and sulfate concentrations in the pore waters of anoxic marine sediments. The sediment column was divided into two zones; an upper zone where diagenetic reaction rates are limited by the concentration of oxidizable organic matter and a lower zone in which reaction rates are limited by the concentration of oxidizing agent—sulfate. For each zone differential equations describing the distribution of methane and sulfate were derived. The boundary conditions used to solve these equations resulted in a set of four coupled equations. When fit to data from Saanich Inlet (B.C., Canada) and Skan Bay (Alaska) the model not only reproduces the observed methane and sulfate pore water concentration profiles but also accurately predicts the methane oxidation and sulfate reduction rates. Maximum methane oxidation rates occur at the transition boundary from the upper to the lower layer. In Saanich Inlet sediments from 23 to 40% of the downward sulfate flux is consumed in methane oxidation while in Skan Bay this value is only about 12%.

Flame/Wall Interface: Theory and Experiment

Abstract The interface region of a steady-state methane-air flame near a cooled, moving wall has been studied using laser spectroscopy in conjunction with a theoretical analysis. Theory and experiment are qualitatively similar for the methane concentration profile parallel to and 100 μm from the wall. Both show rapid methane decay with the experimental decay being weakly dependent on wall speed. The quantitative discrepancies between theory and experiment are most likely due to the overly simple one-step reaction mechanism used in the theory. Species diffusion is found to be an important effect in fuel decay near cooled walls.