Atmospheric methane

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

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.

Characterization of Methanotrophic Bacterial Populations in Soils Showing Atmospheric Methane Uptake

Abstract: The global methane cycle includes both terrestrial and atmospheric processes and may contribute to feedback regulation of the climate. Most oxic soils are a net sink for methane, and these soils consume approximately 20 to 60 Tg of methane per year. The soil sink for atmospheric methane is microbially mediated and sensitive to disturbance. A decrease in the capacity of this sink may have contributed to the approximately 1%. year(-1) increase in the atmospheric methane level in this century. The organisms responsible for methane uptake by soils (the atmospheric methane sink) are not known, and factors that influence the activity of these organisms are poorly understood. In this study the soil methane-oxidizing population was characterized by both labelling soil microbiota with (14)CH(4) and analyzing a total soil monooxygenase gene library. Comparative analyses of [(14)C]phospholipid ester-linked fatty acid profiles performed with representative methane-oxidizing bacteria revealed that the soil sink for atmospheric methane consists of an unknown group of methanotrophic bacteria that exhibit some similarity to type II methanotrophs. An analysis of monooxygenase gene libraries from the same soil samples indicated that an unknown group of bacteria belonging to the alpha subclass of the class Proteobacteria was present; these organisms were only distantly related to extant methane-oxidizing strains. Studies on factors that affect the activity, population dynamics, and contribution to global methane flux of "atmospheric methane oxidizers" should be greatly facilitated by use of biomarkers identified in this study.

δ13C depth profiles from paleosols across the Permian-Triassic boundary: Evidence for methane release

Abstract: Stable carbon isotopic analyses of organic carbon (δ 13 C) in individual paleosol profiles from Permian–Triassic sequences of Antarctica reveal systematic isotopic variations with profile depth. These variations are in many cases analogous to those in modern soils, which are functions of redox conditions, soil development, and degree and type of microbial decay. In modern soils, these isotopic depth functions develop independently from vegetation changes (C 3 versus C 4 vegetation) and can be diagnostic of soil orders. This study shows that soil-intrinsic functions can be preserved in the δ 13 C values of paleosols as old as 260 Ma and constitute valuable data for paleoecological interpretations. A large carbon isotopic offset of as much as 10‰ in whole paleosol profiles across the Permian-Triassic boundary indicates significant changes in the soil biogeochemistry and the soil-atmosphere system. Early Triassic paleosols are distinctive in their extremely low δ 13 C values (to −42‰) and often show an anomalous δ 13 C depth distribution compared to both Permian paleosols and modern soils. Highly depleted δ 13 C values, as the ones in Early Triassic paleosols, are suggested to be associated with microbial methane oxidation (methanotrophy). This hypothesis implies increased methane concentrations in the Early Triassic soil-atmosphere system. Increased atmospheric methane was probably partly responsible for the global carbon isotopic shift documented in marine and terrestrial sediments across the Permian–Triassic boundary.

The growing role of methane in anthropogenic climate change

Abstract: Unlike CO2, atmospheric methane concentrations are rising faster than at any time in the past two decades and, since 2014, are now approaching the most greenhouse-gas-intensive scenarios. The reasons for this renewed growth are still unclear, primarily because of uncertainties in the global methane budget. New analysis suggests that the recent rapid rise in global methane concentrations is predominantly biogenic-most likely from agriculture-with smaller contributions from fossil fuel use and possibly wetlands. Additional attention is urgently needed to quantify and reduce methane emissions. Methane mitigation offers rapid climate benefits and economic, health and agricultural co-benefits that are highly complementary to CO2 mitigation.