Natural microseepage of methane to the atmosphere from the Denver‐Julesburg basin, Colorado

Abstract

Abstract. Methane fluxes were measured at locations across the Denver-Julesburg (DJ) basin of northeastern Colorado, which is in a semiarid climate. There is a potential for microseepage of thermogenically derived methane and light hydrocarbons to the atmosphere, which during drier or colder seasons may exceed the capacity for methanotrophic oxidation in the shallow soils. Triplicate measurements of methane flux in three seasons across the basin found areas of positive and negative fluxes in a patchy pattern which averaged +0.57 mg CH 4 m -2 d -1. The possibility of drier areas of the continents, which are underlain by thick sedimentary units seasonally producing positive methane fluxes to the atmosphere, represents a second-order effect in the estimation of the terrestrial sources/sinks for atmospheric methane. The chambers were operated in a static mode, shaded from the Sun, and air under the chamber mixed using an externally 28,041

Seasonal Variability in CH4Emissions from a Landfill in a Cool, Semiarid Climate

“…The increased range and standard deviation in the winter were also consistent with the background data of Klusman et al 21,24 Cumulative frequency plots suggested that in each season there were a high-flux and a low-flux population.…”

“…10,16 Due to the reliance of methanotrophs on diffusion from both the atmosphere and the subsurface, the habitat of these microbes can be expected to be in a relatively narrow band in the shallow interval of the landfill cover. This is also consistent with lower winter rates of methanotrophic oxidation found in native soils with grass/shrub cover, and in a semiarid climate found by Klusman et al [20][21][22][23][24] EXPERIMENTAL METHODS Static flux chamber methods were utilized in this study to evaluate seasonal CH 4 fluxes over the Rooney Road landfill in Jefferson County, CO. The landfill had received MSW with a high proportion of CH 4 -prone materials such as paper and food wastes.…”

“…The populations were apparently conditioned to a substantial supply and, consequently, are more efficient at atmospheric extraction of CH 4 than methanotrophs in background areas. It should be noted that the most negative values in the fall and winter (-60.5 and -65.0 mg CH 4 /m 2 /day) and four others were more negative than the most negative value (-41 mg CH 4 /m 2 /day) found in 1032 individual chamber measurements from the background studies of Klusman et al 21,24 Most of the negative values were observed in the winter sampling. This was also consistent with the previous studies in background areas exhibiting extreme variability, particularly as winter was transitioning into spring.…”

“…This was consistent with the CH 4 flux data for 1032 background chamber measurements in the region. 21,24 In that study, there was a mean of -0.12, a median of -0.08, and a range of -41 to +43 mg CH 4 /m 2 /day. The flux rates in Table 2 are comparable to those found in a seasonal study in Scandinavia by Börjesson and Svensson, 35 in which four chambers had mean fluxes of 13.1 to 7699 mg CH 4 /m 2 /day.…”

Biogenic methane and carbon dioxide generation in organic-rich shales from southeastern Brazil

“…On the other hand, they also represent potential sources of greenhouse gas emissions to the atmosphere. Large emissions of CH 4 from hydrocarbon prolific basins to the atmosphere were already detected in several places (Klusman and Jakel, 1998;Etiope, 2004;Etiope et al, 2008;Etiope and Klusman, 2010). Methane emissions from hydrocarbon reservoirs and source rocks may also affect the potential of soils as carbon sink and the groundwater chemistry.…”