Distribution of Externally Applied 15NH4 + or 15NO3 − in White Lupins at Different Developmental Stages

White lupins (Lupinus albus L., var. Kievsky mutant) were grown in Mitscherlich pots. ¹⁵NH₄NO₃ or NH₄ ¹⁵NO₃ (10 or 95 at% ¹⁵N exc.) was applied at the late vegetative stage (14–16 leaves) or at the generative stage (end of bloom), respectively. Dry weight increase (ΔDW) of the plants as well as the ¹⁵N distribution in different organs and N fractions (NO_{3 ?}-N, NH₂-N, protein N) were investigated after 5 days and 50 days (maturity). The following results were obtained:

1. In comparison with the ¹⁵N derived from NO₃ ^?, the ¹⁵N derived from NH₄ ⁺ was more strongly retained in the roots. When transported into the shoot, it was more strongly translocated into the tip.

2. More ¹⁵N derived from NH⁴ ₊ was incorporated into proteins and reduced soluble N compounds than ¹⁵N derived from NO₄ ^?. Even in the above-ground plant tissues, a considerable proportion of the latter was found as NO₃ ^?.

3. In the long-term experiment (harvest at maturity 50 days after application), no difference in translocation and incorporation could be found between the two offered ¹⁵N sources.     

Dinitrogen Fixation of Microbe-Plant Associations as Affected by Nitrate and Ammonium Supply

Abstract

The dinitrogen fixation activity of Azospirillum sp., and Pantoea agglomerans strains was determined by ¹⁵N₂ incorporation after incubation with ¹⁵N₂ labeled air or/and by acetylene reduction. These bacterial strains were able to fix N₂ both in pure culture and in association with wheat plants in hydroponics. Nitrogenase activity of Azospirillum sp., in pure culture was more rapidly inhibited by the addition of NH₄ ⁺ than NO₃ ^?. The N₂ fixation of P. agglomerans decreased only by NH₄ ⁺ -addition, but was stimulated by NO₃ ^?. Nitrogen fixation in association with wheat plants remained unaffected by both N compounds. However, nitrogen derived from the atmosphere (N_dfa) contributed only very little to the overall nitrogen nutrition of the plants.     

Quantitative Analysis of Added Ammonium and Nitrate in Silica Sand and Soil Using Diffuse Reflectance Infrared Spectroscopy

Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) in both near infrared (NIR) and mid infrared (MIR) has been previously shown to be effective in quantifying soil nitrogen concentrations when calibrated using numerous field soil samples. However, such an approach incorporates samples that may contain substantial correlations between physical and chemical properties. To address these concerns, the performance of DRIFTS coupled with PLS regression in NIR regions, 5000–4000 cm^? 1 (2000–2500 nm) and 6500–5500 cm^? 1 (1540–1820 nm), and the MIR region, 3400–2400 cm^? 1 (2940–4170 nm), was assessed through analysis of the concentration of ammonium (NH₄ ⁺) (0–50 ppm) and nitrate (NO₃ ^?) (0–200 ppm) artificially incorporated into a series of silica sand samples with a consistent particle size. The influence of different particle sizes of sand was also analyzed quantitatively. The Pima clay loam soil was then evaluated with concentration ranges of 0–200 ppm NH₄ ⁺ and 180–1000 ppm NO₃ ^? added to the soil samples. With sand samples, accurate NH₄ ⁺ measurements could be performed using all three ranges. The MIR region was significantly more useful for NO₃ ^? measurement than those of NIR regions. The MIR region also performed reasonably well with soil samples but both NIR regions provided poor results. The detection limits for NH₄ ⁺ and NO₃ ^? measurements in sand were 9 ppm NH₄ ⁺ and 39 ppm NO₃ ^? with the correlation coefficients (R²) of roughly 97% and 96%, respectively, and in soil were 100 ppm NH₄ ⁺ and 330 ppm NO₃ ^? with the correlation coefficients (R²) of roughly 80% and 90%, respectively.     

The use of stable isotopes in ecosystem research. First results of a field study with 15N

Terrestrial ecosystems, e.g. forest ecosystems, are characterized by a complex and sensitive network of biotic and abiotic factors and their interactions. By using stable isotopes (e.g. labelled nitrogen compounds), very small addition rates of highly enriched compounds can be applied, which do not change or disturb the investigated system, but provide information about single processes, their interactions and especially about their dynamics.

First results of a field study in the Fichtelgebirge, Northeast-Bavaria, Germany, are presented. The distribution of labelled nitrogen (as ¹⁵N-NH₄ ⁺ and ¹⁵N[sbnd]NO₃ ^?) within a spruce ecosystem (Picea abies (L.) Karst. in competition with understory vegetation of Vaccinium myrtillus, Calluna vulgaris and Deschampsia flexuosa) showed maximum ¹⁵N concentrations in tissues of the understory vegetation. During the first six weeks after the ¹⁵N application, the nitrogen uptake of all investigated species was higher after the ¹⁵N[sbnd]NO₃ ^? treatment than after the ¹⁵N[sbnd]NH₄ ⁺ treatment.     

In vivo NMR spectroscopy: in situ 15N pulse labelling NMR spectroscopy with photoautotrophic microorganisms

For studying the nitrogen metabolism in plants ¹⁵N NMR spectroscopy can be used. For in vivo ¹⁵N NMR (natural abundance of ¹⁵N: 0.37%) enrichment of the sample with the isotope ¹⁵N is compulsory. The detection of time courses of ¹⁵N assimilation from cells, which are enriched in culture is restricted in scope. Here, a method, the ¹⁵N pulse labelling NMR spectroscopy, is demonstrated, which permits labelling of different nitrogen compounds in photoautotrophic microorganisms during the NMR spectroscopic measurement. Using an effective illumination system it is possible to maintain photosynthesis in plant samples of high biomass densities in the magnet necessary for ammonia assimilation. The technique thus enables to directly observe ammonia assimilation pathways by application of a ¹⁵NO₃ ^? or ¹⁵NH₄ ^? pulses.

Für das Studium des Stickstoffstoffwechsels der Pflanzen kann die ¹⁵N-NMR-Spektroskopie herangezogen werden. Hierzu ist bei der in-vivo-¹⁵N-NMR (natürliche Häufigkeit von ¹⁵N: 0.37%) eine Anreicherung der Probe mit dem Isotop ¹⁵N unerläßlich. Eine Verfolgung der ¹⁵N-Assimilationskinetik mit Zellen, die in der Kultur angereichert wurden, ist jedoch nur bedingt möglich. In dieser Arbeit wird die ¹⁵N-Pulsmarkierungs-NMR-Spektroskopie als eine Methode vorgestellt, die es erlaubt, eine Markierung von Stickstoffverbindungen in photoautotrophen einzelligen Mikroorganismen während der NMR-Messung im Magneten vorzunehmen. Es wird ein spezielles Beleuchtungssystem verwendet, das eine für die Stickstoffassimilation ausreichende Photosyntheseleistung der Zellen unter NMR-Bedingungen bei hoher Biomassedichte ermöglicht. Diese Technik erlaubt durch die Applikation eines ¹⁵NO₃ ^?-oder ¹⁵NH₄ ⁺-Pulses eine direkte Verfolgung von Ammonium-Assimilationswegen.     

Inkorporation von 15N-markiertem Harnstoff in Organogene Dünge- und Abfallstoffe während der Rotte

Abstract

Eight organic fertilizers and wastes enriched with ¹⁵N labelled urea were stored at 25°C for one year. At the end of the experiment the ¹⁵N recovery rate ranged between 24 and 100%. The distributions of inorganic nitrogen (NH₄- and NO₃-N) and organic nitrogen (fulvic acids, humic acids and non extractable substances) are ascertained. Between the test materials, there are great differences in incorporation parameters.     

Raman scattering study of the low temperature phase of ammonium nitrate

Raman spectra of NH₄NO₃ and ND₄NO₃ have been recorded from room temperature down to 11K. A sluggish transition from phase IV to phase V was clearly observed but no evidence was found for another low temperature phase. Large splitting of the ν₃ mode indicates that the interionic interaction between NH⁺₄ and NO^-₃ is rather strong in both phases. A possible mechanism for the transition involving coupled modes is discussed.     

Matrix reactions of Zn,Cd and Mg atoms with NO2. Infrared spectra of M+NO2− species

Matrix reactions of Mg, Zn and Cd atoms and NO₂ have been performed. Infrared absorptions in the 1220 cm^?1 range show isotopic shifts appropriate for M⁺NO₂^? species. Bands near 950 cm^?1 in the zinc experiments are attributed to a different ion-pair structural isomer.     

Uptake of 15NH3 by Picea abies in Closed Chamber Experiments

Abstract

Above-ground deposition of anthropogenic trace gases like NH₃ and NO_x is considered as a main factor for nitrogen (N) loading of Picea abies ecosystems. In order to quantify NH₃ deposition, tracer experiments with ¹⁵N labelled NH₃ were carried out in fumigation chambers (GSF München).

NH₃ uptake is linearly related to the gas concentration in the air, but the relation differs between organs and depends on N-nutrition of the organs. Plants well supplied with N have a lower NH₃ uptake per g dry weight then plants deprived of N. Only a small amount of the offered gas deposits to the external plant surfaces. The NH₃ uptake rates of spruce indicate that NH₃ may be regarded as being just as or even more important as environmental pollutant than NO_x with respect to N loading of spruce ecosystems.     

15N Distribution in Wheat and Chemical Fractionation of Root-Borne 15N in the Soil

Abstract

Spring wheat plants were grown in split-root containers and labelled with ¹⁵N by fertilizing one compartment of the container with ¹⁵NH₄ ¹⁵NO₃ (95 at.-% ¹⁵N exc.). After the harvest, approx. 90% of the ¹⁵N incorporated by the plants were found in the shoots and 3% in the roots; approx. 7% had been released into the soil of the unlabelled compartment. The ¹⁵N in the soil of the unlabelled compartment was extracted with KCl and hydrolysed with HCl. Approx. 60% of the ¹⁵N was found in the hydrolysable organic N pool of the soil and 9% in the fraction of the soluble and exchangeable inorganic nitrogen.     

Raman study of NH4NO3 and ND4NO3—250–420K

Raman spectra of NH₄NO₃, and ND₄NO₃, were studied from 250 to 420K. The results show that there are four phases separated by first order transitions. No evidence of the previously reported phase II' was observed.The present results combined with the results of other experiments present the following picture of the state of order of the molecules.In phase I, the highest temperature phase, the NH₄⁺ groups are in a free rotation and the nitrate groups are likely in random reorientation among 12-equivalent positions. In phase II, the NH₄⁺ groups are likely in rapid random reorientation under the local force field of S₄ symmetry. The nitrate groups are in hindered rotation but are disordered with one of the O-N bonds directed in one sense or the other along the c-axis. In phase III, the absence of the librational mode indicates that the NH₄⁺ groups are in nearly free rotation but the rotational motion is restricted by the local force field of C₃ symmetry. The nitrate groups are probably ordered as suggested by the well polarized character of the modes associated with the nitrate groups. In phase IV, the nitrate groups are ordered with their molecular planes perpendicular to the b-axis. The NH₄⁺ groups are in orientational disorder but may undergo bindered rotations. An optical mode was observed to couple to an anomalous mode which is believed to be a zone edge acoustical mode.     

Repulsion parameters of ions and radicals—Application to perovskite structures

The compressible ion approach to repulsion which has been shown to work well for the alkali halides (J. Phys. Chem. Solids37, 395 (1976) ; Curr. Sci. 46, 359 (1977)) has been extended to other cubic ionic crystals. Repulsion parameters have been refined for a number of ions and radicals viz., Cu⁺, Ag⁺, Tl⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Sm²⁺, Eu²⁺, Yb²⁺, Pb²⁺, H^?, O^2?, S^2?, Se^2?, Te^2?, NH₄⁺, SH^?, SeH^?, BrO₃^?, ClO₃^?, ClO₄^?, CN^?, NH₂^?, NO₃^?, BH₄^?, BF₄^?, SO₄^2?, NH^2?. Using these parameters, calculations have been made on the lattice spacings and compressibilities of a number of perovskite-like crystals of the form A⁺B²⁺C₃^?. The predicted values agree well with experiment. In the case of four crystals viz., LiBaF₃, LiBaH₃, LiEuH₃ and LiSrH₃, there were large discrepancies between the calculated and observed lattice spacings. When these crystals were assumed to be of the inverse perovskite structure, calculations showed good agreement with the experimental data.     

Incorporation of NH<Subscript>4</Subscript>NO<Subscript>3</Subscript> into MC-PVA blend-based polymer to prepare proton-conducting polymer electrolyte films

Proton-conducting solid polymer blend electrolytes based on methylcellulose-polyvinyl alcohol:ammonium nitrate (MC-PVA:NH₄NO₃) were prepared by the solution cast technique. The structural and electrical properties of the samples were examined by X-ray diffraction (XRD), Fourier transform infrared (FTIR), and electrical impedance (EI) spectroscopy. The shifting and change in the intensity of FTIR bands of the electrolyte samples confirm the complex formation between the MC-PVA polymer blend and the NH₄NO₃ added salt. The observed broadening in the XRD pattern of the doped samples reveals the increase of the amorphous fraction of polymer electrolyte samples. The increase in electrical conductivity of polymer electrolyte samples with increasing salt concentration attributed to the formation of charge-transfer complexes, and to increase in the amorphous domains. A maximum ionic conductivity of about 7.39 × 10^?5 S cm^?1 was achieved at room temperature for the sample incorporating 20 wt% of NH₄NO₃. The DC conductivity of the present polymer system exhibits Arrhenius-type dependence with temperature. The decrease in the values of activation energies with increasing salt concentration indicates the ease mobility of ions. The decrease in dielectric constant with increasing frequency was observed at all temperatures. Optical properties such as absorption edge, optical band gap, and tail of localized state were estimated for polymer blend and their electrolyte films. It was found that the optical band gap values shifted towards lower photon energy from 6.06 to 4.75 eV by altering the NH₄NO₃ salt content.     

The Influence of Ammonium on Nitrate Uptake and Assimilation in 2-Year-Old Ash and Oak Trees - A Tracer-Study with 15N

Abstract

Interactions between ammonium and nitrate as competitive N sources depend on various biotic and abiotic factors. The preference for one of these N sources and the influence of ammonium on nitrate uptake and nitrate reductase activity was investigated in a ¹⁵N labelling experiment using 2-year-old potted plants of ash (Fraxinus excelsior L.) and oak (Quercus robur L.) under greenhouse conditions.

Seedlings of both tree species use ammonium and nitrate in equal amounts when both N forms are supplied in a 1:1 ratio (1.5 mM NH₄ ⁺ + 1.5 mM NO₃ ^?), although there is a slight tendency that ammonium is preferred. In both species total N uptake is higher if ammonium and nitrate are supplied simultaneously when compared with uptake of nitrate alone (3 mM nitrate). If nitrate is the sole N source N uptake is only half as high as if ammonium and nitrate are supplied in a ratio of 1:1.

The distribution of nitrate reductase between shoot and roots is not influenced by the N-form: nitrate reductase activity is always highest in the roots of both species under the conditions of this experiment.

Xylem sap analyses showed that both species transport higher concentrations of amino acids than of nitrate from the roots to the shoot. The amino acid composition is independent of the type of N source. Furthermore, ash trees contain more nitrate in the xylem sap than oak trees, reflecting the higher N uptake and the higher nitrate reductase activity in the leaves of this species.     

Spin-lattice relaxation of protons and deuterons in NH4NO3 and ND4NO3

The spin-lattice relaxation timesT ₁ were measured for protons and deuterons in polycrystalline NH₄NO₃ and ND₄NO₃. The investigation was carried out at temperatures between about 80°K and 430°K using the NMR pulse method. From the measured values ofT ₁ the activation energies for the reorientation motions of NH ₄ ⁺ and ND ₄ ⁺ ions below 200°K were calculated to be 2.07±0.11 kcal/mole and 2.56±0.23 kcal/mole, respectively. The quadrupole coupling constante ² Qq/h of the deuteron in ND ₄ ⁺ ion was found to be 194±30 kc/s.     

Proton magnetic resonance studies of quantum mechanical tunnelling of ammonium ions in several ammonium salts

Proton magnetic resonance spectra were measured at 1·8 K for the compounds NH₄Br, NH₄I, NH₄SCN, (NH₄)₂CrO₄, and NH₄NO₃. The observed derivative curves cannot be explained on the basis only of the dipolar interactions between protons in the NH₄ ⁺ ion held rigidly in the crystal lattices. We considered the effect of quantum mechanical tunnelling on the rotation of an NH₄ ⁺ ion about its C₃-axis and calculated the theoretical lineshapes for various assumed values of the tunnelling splitting constants. Comparison between experiment and theory is quite satisfactory, and the tunnelling splitting constants, Δ, in the librational ground state of the ammonium ion in these salts are determined. It is found that there is a linear relation between the Δ values and the potential barrier to reorientation.     

氢催化的二硝酰胺铵热分解的从头算分子动力学研究

Thermal decomposition of a famous high oxidizer ammonium dinitramide (ADN) under high temperatures (2000 and 3000 K) was studied by using the ab initio molecular dynamics method.Two different temperature-dependent initial decomposition mechanisms were observed in the unimolecular decomposition of ADN,which were the intramolecular hydrogen transfer and N-NO₂ cleavage in N (NO₂)^-.They were competitive at 2000 K,whereas the former one was predominant at 3000 K.As for the multimolecular decomposition of ADN,four different initial decomposition reactions that were also temperature-dependent were observed.Apart from the aforementioned mechanisms,another two new reactions were the intermolecular hydrogen transfer and direct N-H cleavage in NH₄⁺.At the temperature of 2000 K,the N-NO₂ cleavage competed with the rest three hydrogen-related decomposition reactions,while the direct N-H cleavage in NH₄⁺ was predominant at 3000 K.After the initial decomposition,it was found that the temperature increase could facilitate the decomposition of ADN,and would not change the key decomposition events.ADN decomposed into small molecules by hydrogen-promoted simple,fast and direct chemical bonds cleavage without forming any large intermediates that may impede the decomposition.The main decomposition products at 2000 and 3000 K were the same,which were NH₃,NO₂,NO,N₂O,N₂,H₂O,and HNO₂.     

The electron spin resonance spectrum of a γ-irradiated single crystal of glycine

It is shown that γ rays act on glycine to give the free radical NH₃ ⁺-?H-CO₂ ^? which remains trapped in the solid. Electron spin resonance spectra from an irradiated single glycine crystal show marked anisotropy and it is deduced that the radicals are precisely oriented in the crystal lattice. The symmetry shown by the spectra is consistent with that of the crystal lattice. Despite overlapping of lines, the spectra due to the NH₃ ⁺-?H-CO₂ ^? radical have been interpreted in terms of electronnucleus coupling tensors for the N, the H_(C) and the three H_(N) nuclei, the latter being equivalent by virtue of a rotation or tunnelling of the -NH₃ ⁺ grouping. A qualitative interpretation of these tensors in terms of the electronic structure of the radical is given. This is consistent with the negative spin density on the H_(C) atoms and a positive spin density on the H_(N) atoms, as predicted by theoretical treatments. The radicals appear to be oriented in the lattice in approximately the same way as their parent molecules.     

Experimental and modeling study on the ignition delay times of ammonia/methane mixtures at high dilution and high temperatures

Ammonia is a promising alternative clean fuel due to its carbon-free character and high hydrogen density. However, the low reactivity of ammonia and the potential high NO_x emissions hinder its applications. Blending methane into ammonia can effectively improve the reactivity of pure NH₃. In addition, lean combustion, as a high-efficiency and low-pollution combustion technology, is an effective measure to control the potential increase in NO_x emissions. In the present work, the ignition delay times (IDTs) of NH₃/CH₄ mixtures highly diluted in Ar (98%) with CH₄ mole fractions of 0%, 10%, and 50% were measured in a shock tube at an equivalence ratio of 0.5, pressures of 1.75 and 10 bar and a temperature range of 1421 K - 2149 K. A newly comprehensive kinetic model (named as HUST-NH₃ model) for the NH₃/CH₄ mixtures oxidation was developed based on our previous work. Four kinetic models, the HUST-NH₃ model, Glarborg model [19], Okafor model [7], and CEU model [10], were evaluated against the ignition delay times, laminar flame speeds, and species profiles of pure ammonia and ammonia/methane mixtures from the present work and literature. The simulation results indicated that the HUST-NH₃ model shows the best performance among the above four models. Kinetic analysis results indicated that the absence of NH₃ + M = NH₂ + H + M (R819) and N₂H₂ + M = H + NNH + M (R902) in the CEU model and Okafor model cause the deviations between the experimental and simulation results. The overestimation of the rate constants of NH₂ + NO = NNH + OH (R838) in the Glarborg model is the main reason for the overprediction of the NH₃ laminar flame speeds.     

PMR studies of molecular motions,phase transitions and quantum tunnelling in NH4SnCl3 and N(CH3)4SnCl3

Molecular reorientation and low temperature relaxation effects of NH⁺ ₄ ion and the effect of CH₃ substitution (in place of H) are investigated by proton spin lattice relaxation time (T₁) measurements at 10 MHz in NH₄SnCl₃ and N(CH₃)₄SnCl₃ in the temperature range 4.2 K upto the melting points of the compounds (? 440 K). Phase transitions around 360 K in NH₄SnCl₃ and around 361 and 116K in N(CH₃)₄SnCl₃ have been observed. In NH₄SnCl₃, the high temperature minimum at 330.5 K is attributed to the translational diffusion of the NH⁺ ₄ ions, while the other T₁, minima at 103.5, 60 and 50 K are ascribed to the reorientations of the NH⁺ ₄ ion about the C₂ and C₃ axes. The low temperature minimum at 13.5 K is attributed to rotational tunnelling of the NH⁺ ₄ ions. In N(CH₃)₄SnCl₃, in addition to the high temperature minima at 212.2 and 182.6 K due to N(CH₃)₄ tumbling and CH₃ reorientation, a temperature independent T₁ behaviour between 83 and 31 K is observed, below which T₁ decreases and tends to go through a minimum around 5 K. This low temperature minimum is attributed to rotational tunnelling of the CH₃ groups. The motional parameters and tunnel frequencies are estimated.