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Atmospheric methane

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


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TL;DR: Highly enriched methanotrophic communities obtained from acidic ombrotrophic peat bogs from four boreal forest sites are moderate acidophiles rather than acidotolerant organisms, since their growth rate and methane uptake were much lower at neutral pH.
Abstract: Northern wetlands have attracted considerable attention in the last decade as a possible significant source of atmospheric methane (12). Acidic ombrotrophic peat bogs are the most extensive type of wetland, occupying about 3% of total land area and being one of the dominant terrestrial ecosystems in the boreal forest zone of North America and Eurasia. There is a great body of evidence that peat bogs are inhabited by active methanotrophic bacteria that reduce the emission of methane to the atmosphere to 10 to 90% of that generated in the anaerobic layers of the bog profile (9, 17, 19, 21, 22). Although intensive methanotrophic activity in this habitat was recognized many years ago, the microorganisms responsible for this process have eluded isolation. All described methanotrophs are incapable of growth at pH values below 5.0 (7) and thus apparently are unable to oxidize methane in these Sphagnum peat bogs, which have a pH of 3.5 to 5. Other characteristic features of the Sphagnum bog potentially important to the microbial community are the low content of mineral elements in peat water (5 to 50 mg/liter), the presence of inhibitory products from mosses, and a broad annual temperature range from −30 to +30°C. Methane consumption, in particular, is very sensitive to temperature variation, especially during cold seasons. Routine enrichment techniques have failed to yield isolates of methanotrophs from this hostile environment. The only exception is a report on the isolation of a bacterium ascribed to the genus Methylosinus from an acidic peat lake (9), but no experimental confirmation of its activity at low pH was provided. Furthermore, no evidence was provided that the isolated bacterium exhibited any activity in situ, an especially important point since Methylosinus has the ability to form exospores and survive for a long time under unfavorable conditions (6). The ecological application of molecular techniques has opened up a new opportunity for direct detection of methane-oxidizing bacteria in environmental samples. Indeed, primers designed for amplification of the soluble methane monooxygenase (sMMO) gene cluster have shown the predicted PCR products from DNA from acidic peat, suggesting that these habitats contain numerous methanotrophs (13). Other evidence for the existence of acidophilic methanotrophs was obtained by screening 16S rDNA libraries from several peat samples by means of hybridization with specific probes (14). A few of these clones were found to be representatives of a potentially novel group of methanotrophs related to the Methylosinus-Methylocystis cluster. Our recent studies (4, 5) dealt with measurements of methanotrophic activity in samples of native peat from four different bogs under various environmental conditions. We found that indigenous methanotrophic populations, as reflected by their activity in peat, have temperature optima of 15 to 20°C and pH optima of 4.5 to 5.5 and are extremely sensitive to salt stress. The aim of the present study was to undertake the next step in the characterization of acidophilic methanotrophs and obtain a highly enriched methanotrophic population able to grow in acidic peat. We also report on the kinetic and physiological features of the organisms adapted to this unique habitat.

172 citations

Journal ArticleDOI
TL;DR: In this paper, trace gas fluxes of N2O and CH4 were measured weekly over 12 months on cultivated peaty soils in southern Germany using a closed chamber technique, and the authors quantified the effects of management intensity and of soil and climatic factors on the seasonal variation and the total annual exchange rates of these gases between the soil and the atmosphere.
Abstract: Trace gas fluxes of N2O and CH4 were measured weekly over 12 months on cultivated peaty soils in southern Germany using a closed chamber technique. The aim was to quantify the effects of management intensity and of soil and climatic factors on the seasonal variation and the total annual exchange rates of these gases between the soil and the atmosphere. The four experimental sites had been drained for many decades and used as meadows (fertilized and unfertilized) and arable land (fertilized and unfertilized), respectively. Total annual N2O-N losses amounted to 4.2, 15.6, 19.8 and 56.4 kg ha–1 year–1 for the fertilized meadow, the fertilized field, the unfertilized meadow and the unfertilized field, respectively. Emission of N2O occurred mainly in the winter when the groundwater level was high. At all sites maximum emission rates were induced by frost. The largest annual N2O emission by far occurred from the unfertilized field where the soil pH was low (4.0). At this site 71% of the seasonal variation of N2O emission rates could be explained by changes in the groundwater level and soil nitrate content. A significant relationship between N2O emission rates and these factors was also obtained for the other sites, which had a soil pH between 5.1 and 5.8, though the relation was weak (R2 = 15–27%). All sites were net sinks for atmospheric methane. Up to 78% of the seasonal variation in CH4 flux rates could be explained by changes in the groundwater level. The total annual CH4-C uptake was significantly affected by agricultural land use with greater CH4 consumption occurring on the meadows (1043 and 833 g ha–1) and less on the cultivated fields (209 and 213 g ha–1).

172 citations

Journal ArticleDOI
11 Aug 2011-Nature
TL;DR: Measurements in firn (perennial snowpack) air from Greenland and Antarctica are used to reconstruct the atmospheric variability of ethane (C2H6) during the twentieth century, finding that this variability was primarily driven by changes in ethane emissions from fossil fuels.
Abstract: Methane is a greenhouse gas with a significant warming effect on climate only water vapour and carbon dioxide are more important yet the factors influencing its atmospheric concentration are poorly understood. In particular, a rapid rise in methane levels in the mid-twentieth century gradually (but temporarily) levelled off around the turn of the millennium; the reasons for this decline in growth rate are still being debated. Two new studies shed light on this conundrum but reach conflicting conclusions. Fuu Ming Kai et al. measure differences in the concentration and isotopic signature of methane between the Northern and Southern Hemispheres and conclude that reduced microbial activity in wetlands was primarily responsible. Changing rice agricultural practices seem to explain about half of the Northern Hemispheric trend. By contrast, Murat Aydin et al. combine measurements of ethane trapped in Antarctic ice with a simple atmospheric model and conclude that the slow-down was caused by reduced methane emissions from fossil-fuel production. In News and Views, Martin Heimann discusses the differing findings of these two studies.

171 citations

Journal ArticleDOI
TL;DR: In this paper, the authors constructed a regional prediction for China's rice paddy methane emissions using the DNDC biogeochemical model and combined results of continuous flooding and mid-season drainage simulations for all paddy fields in China were combined with regional scenarios for the timing of the transition from continuous flooding to predominantly midseason drainage to generate estimates of total methane flux for 1980-2000.
Abstract: [1] Decreased methane emissions from paddy rice may have contributed to the decline in the rate of increase of global atmospheric methane (CH4) concentration over the last 20 years. In China, midseason paddy drainage, which reduces growing season CH4 fluxes, was first implemented in the early 1980s, and has gradually replaced continuous flooding in much of the paddy area. We constructed a regional prediction for China's rice paddy methane emissions using the DNDC biogeochemical model. Results of continuous flooding and midseason drainage simulations for all paddy fields in China were combined with regional scenarios for the timing of the transition from continuous flooding to predominantly mid-season drainage to generate estimates of total methane flux for 1980–2000. CH4 emissions from China's paddy fields were reduced over that period by ∼5 Tg CH4 yr−1.

168 citations

Journal ArticleDOI
27 Sep 1985-Science
TL;DR: Measurements of the methane concentration in air extracted by two different methods from ice samples from Siple Station in western Antarcitica allow the reconstruction of the history of the increase of the atmospheric methane during the past 200 years.
Abstract: Air entrapped in bubbles of cold ice has essentially the same composition as that of the atmosphere at the time of bubble formation. Measurements of the methane concentration in air extracted by two different methods from ice samples from Siple Station in western Antarcitica allow the reconstruction of the history of the increase of the atmospheric methane during the past 200 years.

166 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202395
2022153
202175
202077
201974
201872