Search results for "METHANE"
showing 10 items of 1763 documents
Stable carbon isotopic composition of peat columns, subsoil and vegetation on natural and forestry-drained boreal peatlands.
2018
We studied natural and forestry-drained peatlands to examine the effect of over 34 years lowered water table on the δ13C values of vegetation, bulk peat and subsoil. In the seven studied sites, δ13C in the basal peat layer was 1.1 and 1.2 ‰ lower than that of the middle-layer and surface layer, respectively. Furthermore, there was a positive correlation between the δ13C values of the basal and surface peat layers, possibly due to carbon (C) recycling within the peat column. In the same mire complex, natural fen peat δ13C values were lower than those of the nearby bog, possibly due to the dominance of vascular plants on fen and the generally larger share of recycled C in the fens than in the…
A synthesis of methane emissions from 71 northern, temperate, and subtropical wetlands
2014
Wetlands are the largest natural source of atmospheric methane. Here, we assess controls on methane flux using a database of approximately 19 000 instantaneous measurements from 71 wetland sites located across subtropical, temperate, and northern high latitude regions. Our analyses confirm general controls on wetland methane emissions from soil temperature, water table, and vegetation, but also show that these relationships are modified depending on wetland type (bog, fen, or swamp), region (subarctic to temperate), and disturbance. Fen methane flux was more sensitive to vegetation and less sensitive to temperature than bog or swamp fluxes. The optimal water table for methane flux was consi…
Methanotrophy induces nitrogen fixation during peatland development
2013
Significance In peatlands, the external sources of nitrogen are mainly atmospheric, but the atmospheric nitrogen deposition alone cannot explain the long-term annual nitrogen accumulation rates to these ecosystems. Because of methodological problems, methane-induced fixation of atmospheric dinitrogen gas has been previously overlooked as an additional nitrogen input mechanism. We found that the activity of methane-oxidizing bacteria provides not only carbon but also nitrogen to peat mosses and, thus, contributes to carbon and nitrogen accumulation in peatlands, which store approximately one-third of the global soil carbon pool. Our results imply that nitrogen fixation in wetlands may be str…
Exploring the mechanisms by which reindeer droppings induce fen peat methane production
2021
Abstract Peatlands, especially fens, are known to emit methane. Reindeer (Rangifer tarandus) use mires mainly as spring and summer pastures. In this work we observed that adding reindeer droppings to fen peat increased the potential methane production by 40%. This became apparent when droppings originating from reindeer kept in pen or pasture in winter were added to methanogenic fen peat samples. The droppings introduced Methanobacteriaceae (Methanobrevibacter; > 90% of the mcrA MiSeq reads) to the peat, which was originally populated by Methanosarcinaceae, Methanosaetaceae, Methanoregulaceae, Methanobacteriaceae, Methanomassiliicoccaceae, Methanocellaceae and Methanomicrobiaceae. The origi…
Exposure to trihalomethanes through different water uses and birth weight, small for gestational age, and preterm delivery in Spain
2011
Background: Evidence associating exposure to water disinfection by-products with reduced birth weight and altered duration of gestation remains inconclusive. Objective: We assessed exposure to trihalomethanes (THMs) during pregnancy through different water uses and evaluated the association with birth weight, small for gestational age (SGA), low birth weight (LBW), and preterm delivery. Methods: Mother–child cohorts set up in five Spanish areas during the years 2000–2008 contributed data on water ingestion, showering, bathing, and swimming in pools. We ascertained residential THM levels during pregnancy periods through ad hoc sampling campaigns (828 measurements) and regulatory data (264 me…
Apaf-1 deficient mouse fibroblasts are resistant to MNNG and MMS-induced apoptotic death without attenuation of Bcl-2 decline.
2005
Abstract Simple alkylating agents induce cell death by activating the apoptotic pathway. In rodent fibroblasts, apoptosis triggered by DNA methylation lesions is executed via the mitochondrial damage pathway. Here, we studied cell death induced by the methylating agents methyl methanesulfonate (MMS) and N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) in mouse fibroblasts wild-type (wt) and deficient for Apaf-1 (apaf-1 knockout cells). Apaf-1 is an essential component of the apoptosome complex that becomes activated upon cytochrome c release from mitochondria. We show that apaf-1 knockout cells are more resistant to the cytotoxic effect (as measured by WST assay) of methylating agents. This is d…
Preparation and Structure of Bicycloalkane-Condensed Aryldiaziridines Accompanied by Pyrimidines
2007
Di-exo- and di-endo-2-aminonorbomane/enemethanamines 1-3, di-exo-oxanorbomene derivative 4 and cis-cyclohexane and trans-4-cyclohexene analogues 5, 6 were reacted with p-chlorobenzaldehyde in the presence of N-bromosuccinimide in dichloromethane. Via the reactions of 1-6, condensed diaziridines 7-12 accompanied by pyrimidine derivatives 13-16 were prepared after isolation with column chromatography. The mechanisms proposed for alternative transformations were supported by DFT calculations. The structures of the new compounds were proved by IR and NMR spectroscopy and, for 7, 9 and 12, also by means of X-ray crystallography.
Efficient orange light-emitting electrochemical cells
2012
We report the first bis-cyclometalated cationic iridium(III) complex with N-aryl-substituted 1H-imidazo [4,5-f][1,10]phenanthroline. The complex emits yellow-orange phosphorescence with a maximum at 583 nm, a quantum yield of 43%, and an excited-state lifetime of 910 ns in argon-saturated dichloromethane. Optimized orange light-emitting electrochemical cells with the new Ir(III) complex exhibit fast turn-on, a peak luminance of 684 cd m(-2) and a peak efficacy of 6.5 cd A(-1); in 850 h of continuous operation their luminance and efficacy decrease only by 20%.
Horseradish peroxidase-catalyzed oxidation of chlorophyll a with hydrogen peroxide
2010
Horseradish peroxidase was verified to catalyze, without any phenol, the hydrogen peroxide oxidation of chlorophyll a (Chl a), solubilized with Triton X-100. The 13(2)(S) and 13(2)(R) diastereomers of 13(2)-hydroxyChl a were characterized as major oxidation products (ca. 60%) by TLC on sucrose, UV-vis, (1)H, and (13)C NMR spectra, as well as fast-atom bombardment MS. A minor amount of the 15(2)-methyl, 17(3)-phytyl ester of Mg-unstable chlorin was identified on the basis of its UV-vis spectrum and reactivity with diazomethane, which converted it to the 13(1),15(2)-dimethyl, 17(3)-phytyl ester of Mg-purpurin 7. The side products (ca. 10%) were suggested to include the 17(3)-phytyl ester of M…
Towards simulation of high temperature methane spectra
2002
Methane plays a central role in gas layers of temperatures up to around 3000 K in a number of astrophysical objects ranging from giant planets to brown dwarfs, over proto-solar nebulae, to several classes of cool stars. In order to model and analyse these objects correctly, an accurate and complete list of spectral lines at high temperature is demanded. Predicting high temperature spectra implies, however, predicting hot bands and thus modelling highly excited vibrational states. This is a real challenge in the case of methane. We report the preliminary results of a theoretical study combining the global effective Hamiltonian approach and its computational implementation (STDS package: http…