Bestimmung der 15N Häufigkeit bei nichtstatistischer 15N-verteilung in N2 sowie bei N2O in Bodenluftproben mittels GC-R-IRMS-Kopplung in einem Probenlauf

Abstract

An analysis technique based on GC-R-IRMS coupling (Gas-Chromatography-Reduction-Isotope Ratio Mass Spectrometry) is demonstrated. The ¹⁵N abundance of N² and N²O in atmospheric air or soil atmosphere from nitrification or denitrification processes with nonrandom distribution is determined in one run. The 12 ml sample is separated from CO² and transported by a helium gas stream through a cooling trap. The N²O is trapped in the cooling trap while the N² passes through it and enters the GC. After GC separation and O² removal in a reduction column, part of the N² enters an isotope mass spectrometer to determine the masses m/z 28,29 and 30. The interferences on mass 30 by the formation of NO in the ion source of the mass spectrometer are eliminated by a calibration and a correction procedure. Upon removing the cooling trap, the N²O is injected into the GC, where it is separated and then quantitatively reduced to N² in a reduction column. The measurement of one sample takes 16 minutes. The detection limit of the ³⁰R_t in alteration N₂ is Δ³⁰R_t = 5 · 10^?7. The detection limit of the N₂O is 3.6 nl.     

Production of a0-mesons in the reactions πN↦a0N and pp↦da0 + at GeV energies

We investigate the reactions πN↦a ₀ N and pp↦da ₀ ⁺ near threshold and at medium energies. An effective Lagragian approach and the Regge pole model are applied to analyze different contributions to the cross-section of the reaction πN↦a ₀ N. These results are used to calculate the differential and total cross-sections of the reaction pp↦da ₀ ⁺ within the framework of the two-step model in which two nucleons produce an a₀-meson via π-meson exchange and fuse to a deuteron. The necessity of new measurements on a₀ production and branching fractions (of its decay to the K and πη channels) is emphasized for clarifying the a₀ structure. Detailed predictions for the reaction pp→da ₀ ⁺ are presented for the energy regime of the proton synchrotron COSY-Jülich. Received: 4 August 2000 / Accepted: 17 September 2000     

15N（p,n)15O反应中子源0°角激发函数测量

利用中国原子能科学研究院HI-13串列加速器上的多探测器快中子飞行时间谱仪, 测量了38个不同入射质子能量点下15N（p, n)15O反应0°角方向的激发函数。 测量数据用蒙特卡罗方法进行了模拟, 以进行中子注量衰减和入射窗厚度的不确定度修正。 实验在入射质子能量位于6.029—8.056 MeV之间时发现了3个共振峰, 这一点与DROSG 2000评价数据及PTB数据相符合, 但三家的截面数值存在差异, 对这些差异需要作进一步深入探讨。 The excitation function of 15N（p, n)15O reaction at 0 degree was measured at 38 energy points using the fast neutron Time of Flight (TOF) spectrometer at the HI 13 Tandem Accelerator in the China Institute of Atomic Energy（CIAE）. The measured data were analyzed by Monte Carlo simulation for the corrections of neutron flux attenuation and uncertainty of the thickness of the entrance foil. Three resonance peaks were observed in this experiment in the energy range from 6.029 to 8.056 MeV,which is comparable with the DROSG 2000 evaluated data and the PTB data. However,more experimental studies are needed since the cross sections deviate with each other.     

Experimental plant for simultaneous production of 14N and 15N by 15N/14N exchange in NO,NO2–HNO3 system under pressure

An experimental study on ¹⁴N and ¹⁵N simultaneous separation using the chemical exchange in NO, NO₂–HNO₃ system under pressure is presented. The influence of the pressure and of the interstage 10 M HNO₃ flow rate on the separation of ¹⁴N and ¹⁵N was measured on a packed column with product and waste refluxers. At steady state and 1.8 atm (absolute), the isotopic concentration at the bottom of the separation column was 0.563 at% ¹⁵N, and in the top of the column was 0.159 at% ¹⁵N. The height equivalent to a theoretical plate and interstage 10 M HNO₃ flow rate values, obtained in these experimental conditions, allows the separation of ¹⁴N highly depleted of ¹⁵N and of ¹⁵N at 99 at% ¹⁵N concentration.     

15N16O的激光磁共振谱与同位素分子15N17O和15N18O的光谱分析

采用内腔式饱和吸收技术获得 Ｌａｍ ｂ 凹陷,使 Ｃ Ｏ 激光磁共振谱仪的灵敏度及分辨率大大提高．利用该技术对自然丰度下１５ Ｎ １６ Ｏ 的 Ｘ２Π（ υ＝ １） ← Ｘ２Π（ υ＝ ０） 塞曼跃迁进行测量,实现了包括Λ双分裂在内的各种精细结构的谱分辨．结合已发表的１５ Ｎ Ｏ 同位素分子光谱实验数据进行分析计算,拟合得到迄今最完备、最精确的各相关同位素分子１５ Ｎ ｍ Ｏ（ ｍ ＝ １６ —１８）的结构参数．     

15N-Markierung von Plasmaaminosäuren nach oraler Applikation von [15N]Glycin, [15N]Leucin und [15N]Hefeprotein-Thermitase-Hydrolysat

For the biosynthetic preparation of ¹⁴C-erucic acid (C₂₁H₄₁COOH) by means of rape plants cv. sollux the plants were supplied with ¹⁴CO₂ and additionally fed with ¹⁴C-Sodium acetate after anthesis. After saponification of the extracted lipids the erucic acid was isolated and purified. The substance was identified by gas chromatography. The incorporation of the applied radioactivity (34 MBq ¹⁴CO₂; 37 MBq¹⁴C-natrium acetate) into the fatty acids amounted to 1,2 per cent. The eruric acid could be isolated from the fatty acids mixture with a specific radioactivity of 1,001 MBq/mmol and a purity of 97,2 per cent.     

[15N]Methacetin-und [15N]Ammoniumtest zur Leberfunktionsprüfung im Kindesalter

The stable isotope content of samples of precipitation and of the river water throughout the Piracicaba basin in Brazil was measured over a two-year period. The isotope values of precipitation follow a consistent pattern of relatively depleted values of both deuterium and oxygen 18 during the rainy summers and enriched ones during the dry winters, with all values aligned slightly above the Global Meteoric Water Line. The isotopic composition of the river water throughout the basin shows a remarkable spatial coherence and much smaller scatter of data than those of the precipitation. The isotope composition of river water is close to that of the precipitation in the rainy season, however, with a consistent lower d-excess value by 1‰–2‰. This is attributed to evaporative water loss in the basin, in part an expression of the recycling of water due to the anthropogenic activity in the region. The more divergent values are recorded during high-water stages in the rivers. In many cases, the floods during the beginning of the rainy season are characterized by an enrichment of the heavy isotopes and lower d-excess values when compared to the precipitation, with the opposite situation later in the rainy season. This is interpreted as resulting from the watershed/riverflow interaction pattern, and it thus suggests that the isotope composition can monitor the hydrologic situation in the basin and its changes.     

Spatial variations in larch needle and soil δ15N at a forest–grassland boundary in northern Mongolia

The spatial patterns of plant and soil δ¹⁵N and associated processes in the N cycle were investigated at a forest–grassland boundary in northern Mongolia. Needles of Larix sibirica Ledeb. and soils collected from two study areas were analysed to calculate the differences in δ¹⁵N between needle and soil (Δδ¹⁵N). Δδ¹⁵N showed a clear variation, ranging from ?8?‰ in the forest to ?2?‰ in the grassland boundary, and corresponded to the accumulation of organic layer. In the forest, the separation of available N produced in the soil with ¹⁵N-depleted N uptake by larch and ¹⁵N-enriched N immobilization by microorganisms was proposed to cause large Δδ¹⁵N, whereas in the grassland boundary, small Δδ¹⁵N was explained by the transport of the most available N into larch. The divergence of available N between larch and microorganisms in the soil, and the accumulation of diverged N in the organic layer control the variation in Δδ¹⁵N.     

Soil δ15N patterns in old-growth forests of southern Chile as integrator for N-cycling

Old-growth forests of southern Chile represent an important reserve of temperate (rain) forests in the world. Wetter and colder forest ecosystems appear to be more efficient in conserving and recycling N such that mostly non-plant available N species are lost, which could be indicated by more depleted δ¹⁵N values of the soil and plants. Hydrological N loss from the old-growth forests in southern Chile occurs mainly via dissolved organic nitrogen and not via dissolved inorganic N. Forest disturbances (e.g. fire, clear-cutting or enhanced N deposition) cause (abrupt) changes in ecosystem N-cycling processes. In this study, we hypothesized that δ¹⁵N signatures of soil profiles under old-growth forests could be used as an integrator for ecosystem N-cycling, and changes of these δ¹⁵N profiles could be valuable to assess ecosystem resilience towards disturbances. Six old-growth forests were selected in the phytogeographical region of the Valdivian rain forest in southern Chile. One of the sites has been partly burned in February 2002. First, we observed that ecosystems with higher mean annual precipitation and lower mean annual temperature were relatively more depleted in ¹⁵N. Secondly, we found that a forest fire caused a 100-fold increase of the nitrate export and induced an enrichment of the soil δ¹⁵N signal in the upper 20 cm.     

SHA+脉冲序列用于g-C3N4样品15N-15N相关性的固体核磁共振研究

利用固体核磁共振实验研究了15N标记的g-C3N4样品中的15N-15N空间相关性,在高场和魔角旋转条件下对比两种不同的脉冲序列PDSD和SHA+的实验效果。发现当某个氮上连有质子的时候,脉冲序列SHA+比PDSD可以更好地检测15N原子间的极化转移。该研究可以为材料科学领域,特别是含氮掺杂的碳材料,提供一种有价值的研究方法。     

Untersuchungen mit 15N im Dauerdüngungsfeldversuch

Abstract

Long-term static fertilizer experiments are important for the soil fertility research, particular for using nitrogen problems. There are several possibilities for ¹⁵N-traces in such experiments. One example is the International Organic Nitrogen Long-Term Experiment at Berlin-Dahlem in which ¹⁵N-tracers are used, involving organic and inorganic fertilizers. By analyzing the soil and the plant biomass, it was possible to distinguish between nitrogen originating from the soil and that from the fertilizer. Some results are published.     

同位素~(15)N光电光谱分析

氮在自然界中有两种稳定性同位素,~(14)N(99.635%)和~(15)N(0.365%)。由于同位素~(15)N具有非放射性的特点,已被广泛用作标记原子,进行农业、土壤、生物、医学等过程研究。在各种同位素~(15)N分析方法中,光谱法由于仪器简单,操作方便,灵敏度和准确度较高,已成为一种广泛应用的重要方法,并生产了专门分析仪器。     

Использование изотопа N15 в изученпи усвояемости азотньіх минеральньіх удобрений

The effect of contamination of a cyanide, phosphate-buffered gold-plating bath with iron, cobalt, or nickel on the codeposition of these metals with gold, was investigated using ⁵⁹Fe, ⁵⁸Co and ⁶³Ni. It was shown that cobalt and nickel were practically not codeposited in gold if present in the solution in amounts up to 1000 or 2000 mg/dm³ respectively. Iron deposited in high amounts (up to 18%) depending on its concentration and the cathode current density. The diminishing in current efficiency of the plating process is proposed as an early signal of the contamination of gold deposit with iron.     

GdHO_（0．15）合金电阻率研究

本文利用纯Ｇｄ掺ＨＯ构成ＧｄＨＯ０１５合金，研究居里温度变化．居里温度由纯Ｇｄ的Ｔｃ＝２９３Ｋ，变化到ＧｄＨＯ．１５合金的Ｔｃ＝２７８Ｋ．并在１．５Ｔ外磁场下，液氮温区，研究磁阻变化规律．结果纯Ｇｄ的磁阻在此范围内为负的，而掺ＨＯ后，ＧｄＨＯ０．１５合金的磁阻力正，证明了掺杂ＨＯ原子影响了Ｇｄ的自旋涨落．