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Isotopic signatures of N2O are increasingly used to constrain the total global flux and the relative contribution of nitrification and denitrification to N2O emissions. Interpretation of isotopic signatures of soil-emitted N2O can be complicated by the isotopic effects of gas diffusion. The aim of our study was to measure the isotopic fractionation factors of diffusion for the isotopologues of N2O and to estimate the potential effect of diffusive fractionation during N2O fluxes from soils using simple simulations. Diffusion experiments were conducted to monitor isotopic signatures of N2O in reservoirs that lost N2O by defined diffusive fluxes. Two different mathematical approaches were used to derive diffusive isotope fractionation factors for 18O (epsilon18O), average 15N (epsilonbulk) and 15N of the central (alpha(-)) and peripheral (beta(-)) position within the linear N2O molecule (epsilon15Nalpha, epsilon15Nbeta). The measured epsilon18O was -7.79 +/- 0.27 per thousand and thus higher than the theoretical value of -8.7 per thousand. Conversely, the measured epsilonbulk (-5.23 +/- 0.27 per thousand) was lower than the theoretical value (-4.4 per thousand). The measured site-specific 15N fractionation factors were not equal, giving a difference between epsilon15Nalpha and epsilon15Nbeta (epsilonSP) of 1.55 +/- 0.28 per thousand. Diffusive fluxes of the N2O isotopologues from the soil pore space to the atmosphere were simulated, showing that isotopic signatures of N2O source pools and emitted N2O can be substantially different during periods of non-steady state fluxes. Our results show that diffusive isotope fractionation should be taken into account when interpreting natural abundance isotopic signatures of N2O fluxes from soils. 相似文献
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Abstract The estimation of denitrification in soil by the 15N tracer technique includes isotope analysis of gas samples with a nonrandom distribution of the N2 mole masses of 28, 29 and 30. In that case the emission of total 15N is underestimated by calculating 15N atom fractions from the 29N2/28N2 ratio if 30N2 is not considered. 30N2 can be measured indirectly in N2 enriched with 15N with nonrandom distribution of mole masses by mass spectrometric analysis. The nitrogen fraction of gas samples was transferred to discharge tubes. Microwaves (60 sec) generated an electrodeless discharge of the gas which caused a temporary split-up of N2 molecules and thus established an equilibrium distribution of the mole masses. The 29N2/28N2 ratio was measured in equilibrated and in untreated samples to calculate the real emission of 15N. The measurements of 15N standard gases by this method satisfactorily coincided with calculated values for 15N atom fraction above a concentration of 50 δ‰. 相似文献
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The precision of the 15N-emission and that of the 15N-balance methods was evaluated and both methods were compared in a denitrification experiment. 15N-analysis was performed with an isotope ratio mass spectrometer which was coupled to an elemental analyzer. The measuring sensitivity in soil and gas analysis was tested by analyzing 15N-standards. The detection limit for gas samples with two different procedures of 15N-gas analysis was δ15N = (4.5 ± 1.0)‰ and (0.5 ± 0.05)‰, respectively. The error in measurement was 19% and 12% respectively. 15N-analysis of a 15N-labelled soil (4.15 ppm 15N) resulted in a CV of 1.32%. The measurements had to be calibrated with soil standards because the 15N-values showed a continuous downward fluctuation in a range of 10–20% within several days, when only acetanilid was used for calibration. Mean 15N-losses which were determined with both methods during the denitrification experiment were in good agreement. The precision of the 15N-emission method was adequate in all variants of the experiment. The precision of the 15N-balance method however was unsatisfactory at low 15N-losses (0.2–2% of added 15N). 相似文献
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Joachim Mohn Benjamin Wolf Sakae Toyoda Cheng‐Ting Lin Mao‐Chang Liang Nicolas Brüggemann Holger Wissel Amy E. Steiker Jens Dyckmans Lars Szwec Nathaniel E. Ostrom Karen L. Casciotti Matthew Forbes Anette Giesemann Reinhard Well Richard R. Doucett Chris T. Yarnes Anna R. Ridley Jan Kaiser Naohiro Yoshida 《Rapid communications in mass spectrometry : RCM》2014,28(18):1995-2007
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Isotope fractionation factors controlling isotopocule signatures of soil‐emitted N2O produced by denitrification processes of various rates 下载免费PDF全文
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Albert Moser Niklas Rotering Wolfram Wellßow Helge Pluntke 《e & i Elektrotechnik und Informationstechnik》2013,130(3):75-80
According to the German federal government’s energy concept renewable energies are to supply 80 % of the gross electricity consumption till 2050. The study “Energiespeicher für die Energiewende” provided by the Association for Electrical, Electronic and Information Technologies (VDE), is focused on the question which storage demand is needed to achieve this goal and what effect the storage plants and their operation will have on the German transmission network. 相似文献