9303385 Klusman It is proposed to measure methane and non-methane hydrocarbon (NMHC) fluxes from the earth in sedimentary basins with a focus on arid and semiarid environments. The microseepage phenomenon is widespread, though not generally recognized as a significant contribution to the atmospheric loading by hydrocarbons. Saturated hydrocarbons, particularly methane, make a significant contribution to the absorption of infrared radiation from the earth. The 14C activity of the atmosphere sets an upper limit to the contribution of methane from all fossil fuel sources in the range of 20-30%. Presumably nearly all of the C2-C5 saturated hydrocarbons in the atmosphere are from fossil fuel sources. Research to date attributes the fossil fuel contribution entirely to man-induced leakage and pollution, but has not measured the natural microseepage rates in the environments where it is likely to occur. The proposal is to measure the natural fluxes of CH4 and NMHC in several sedimentary basins in the western United States using gas chromatography the basins selected are known to have a wide range of concentrations of hydrocarbons in soil gas. The fluxes are expected to be proportional to the soil gas concentrations. The research in the first year will concentrate on preliminary estimates of fluxes using flux chamber techniques. Second year research will focus on more accurate measurement of fluxes from additional basins and application of carbon isotopy to support the nature of the source of methane and NMHCs. The proposed research will be of significance in global change research if it is found that natural microseepage is a major contribution to the methane and C2-C5 emission inventories.
