Mixed Ammonium Research Articles

Enhanced Recovery of Technetium(VII) by Primary Amine Extraction from Aqueous Fluoride Solutions and Aqueous Alkaline Solutions

AbstractThe extraction behavior of technetium from aqueous hydrofluoric acid solution has been investigated. The recovery of Tc using two techniques, primary amine extraction in mixed heptane and 1–octanol solution and stripping with a mixed aqueous ammonium hydroxide – ammonium carbonate solution has been studied. The determination of distribution ratios and percentages of technetium in both extraction and stripping cycles was established as were the volume ratios between organic and aqueous phases. The stripping mechanism in the aqueous solution has also been investigated by the slope analysis method.

Root Morphology and Nitrogen Uptake of Maize Simultaneously Supplied with Ammonium and Nitrate in a Split-root System

We studied the response of maize (Zea mays L. cv. Anjou 256) to a simultaneous, but separated supply of ammonium and nitrate (localized supply, LS). A split-root system was used to supply half of the roots with ammonium and the other half with nitrate. A homogeneously distributed supply of both nitrogen forms (HS) was the control treatment. Seedlings were grown for 12 d from the two-leaf to the three-leaf stage in hydroponics at three pH levels (4, 5·5 and 7). The total N concentration was 3 mol m-3. The split-root system was established by removing the seminal root system and using only four nodal roots per plant. Total root length and root surface area were recorded automatically with a modified Delta- T area meter. Other morphological root traits (such as main axis length and diameter, number, density, and length of laterals) were recorded manually. Uptake of ammonium and nitrate was measured by the depletion of the nutrient solution. As compared with LS, HS was superior in shoot and root DM, total root length and root surface area, ammonium and nitrate uptake and shoot nitrogen concentration, irrespective of pH level. This indicates that, also under field conditions, mixed ammonium and nitrate fertilization is only beneficial to plant growth if both N forms are evenly distributed in the soil. At both HS and LS, ascending pH increased the ammonium:nitrate uptake ratio. At LS, declining pH induced a considerable shift in the distribution of root DM, root length, and root surface area the nitrate-fed compartment.

Water activities of NH4NO3/(NH4)2SO4 solutions

Water activities for mixed ammonium nitrate/ammonium sulfate solutions at relative humidities of 0.35–0.75 were measured using a spherical void electrodynamic balance. The concentrations of singly levitated droplets of nitrate to sulfate mole ratio of n= 15, 13, 12, 1, 2 and 4 in equilibrium with an ambient environment of prescribed relative humidity were measured. To avoid uncertainty in determining the composition of the solid particles, solution properties were determined relative to the known properties at about 80% relative humidity. The concentration of this reference state was estimated by three models of mixed electrolyte solutions, the Zdanovskii-Stokes-Robinson (ZSR), the Kusik and Meissner (KM) and the Pitzer models. The measured total mass fraction of solute of the mixed solutions differed by less than 0.5% when different models were used to calculate the reference state concentration. The water activity data were obtained at ionic strengths as high as 108 molal and used to evaluate predictions from these three models. For n =15and13, deviations of model predictions from experimental data are within 2%. Generally, predictions of the ZSR model are most consistent with our data. Maximum deviations occur at n=2; 6% for ZSR, 8% for KM and 5% for Pitzer. The deviations can be attributed to binary and ternary solute-solute interactions that the ZSR, KM and elementary version of the Pitzer models do not consider. However, no simple characterization of the interaction parameters is possible; they seem to be strong functions of the fractional ionic strength of the solute and the total ionic strength of the solutions.

Molecular nitrogen formation by electron-beam processing of flue gas

The irradiation of combustion flue gas with electrons leads to simultaneous oxidation of NO x and SO 2. Upon ammonia addition, the major product is a mixed ammonium nitrate/sulfate aerosol. In side reactions, NO is reduced to molecular nitrogen. Experiment and numerical model agree quantitatively. Further studies are proposed.

Increasing salt tolerance of wheat by mixed ammonium nitrate nutrition

Abstract In a greenhouse experiment with wheat, sandy loam or clay soils were salinized by additions of 0, 3. or 8 g NaCl/3L pot. Ammonium and nitrate nitrogen mixtures in ratios of 0/100, 25/75 and 50/50 together with DCD, a nitrification inhibitor, were applied with irrigation water. Salinity significantly reduced dry matter yields, and N and P content in grain and stover. In accordance with previous reports, a mixed ammonium and nitrate N source produced larger dry matter and protein yields than nitrate alone, particularly in grains. The relative increases in yields and N and P accumulation, due to mixed N nutrition, were significantly higher in salinized soils and increased with increasing proportions of ammonium. Grain dry matter and N yields at medium salinity with a 50/50 N mixture, were equal to, or higher than those in non‐salinized soil fertilized with nitrate only. Chloride concentrations in stover increased with salinity and proportion of ammonium in the mixed source indicating that the advantage of mixed N nutrition is not due to nitrate‐chloride antagonism. Sodium concentration in plant tissues increased with salinity, but was reduced by increasing proportions of ammonium in the medium. This effect may be attributed to competition between ammonium and sodium for root uptake sites. The results obtained emphasize the effectiveness of mixed N sources to increase salt tolerance of crops such as wheat.

Review of interaction of ammonium ‐ nitrate and potassium nutrition of crops

Abstract Literature review indicates that higher crop yields may be obtained with a mixture of nitrate and ammonium than with either source alone. An adequate supply of potassium enhances ammonium utilization and thus improves yields, when a mixed ammonium‐nitrate nitrogen nutrition is applied. Nitrate reduction in plant tissues consumes either chemical energy and organic acids, or competes for products of photolysis. When ammonium is applied to the roots, high concentrations of it may accumulate having a strong toxic effect. Potassium activates plant enzymes functioning in ammonium assimilation and transport of amino acids. A summary of the experiments performed by the authors indicates that a mixed ammonium, nitrate and potassium nutrition affects especially N uptake and thus production of organic nitrogen compounds.

Physiological aspects of ammonium and nitrate fertilization

Abstract Various physiological effects of ammonium, nitrate and mixed ammonium‐nitrate nutrition of plants have been studied in this laboratory during the last years. Some of the characteristic distinctions observed between plants growing on these nitrogen sources are described and discussed. Biomass production of ammonium‐grown plants increased with K+ concentration in the nutrient medium between 0.1 to 3 mM , while nitrate‐fed plants reached maximal growth around 0.25 mM K+ . The water use efficiency (WUE) of ammonium‐fed plants was lower and also more dependent on K+ than that of plants receiving nitrate. At low K+ levels (0.1 mM) in the medium, plants growing on ammonium‐N spent nearly twice as much water through transpiration per unit mass than nitrate‐fed plants. WUE of plants receiving NH4NO3 was poor at low K+ (similar to ammonium‐fed plants) but at high K+ this plants grew even better than nitrate‐grown plants. Overall transpiration per plant was little affected by K+ levels in the medium. Consequently, the main effect of K+ was on the overall photosynthetic capacity of the shoot. Similar studies were carried out on the efficiency of the plants to convert inorganic nitrogen taken up from the nutrient media into organic nitrogen. Ammonium‐fed plants assimilated into organic compounds only between 20% and 30% of the nitrogen taken up from the solution. NUE of nitrate‐fed plants was much higher (about 100%) regardless of the K+ levels in the medium. In additional studies to characterize the preferential growth rate of plants fed mixed ammonium and nitrate sources, we examined root respiration rates, oxidation of 14C‐labeled assimilates by the root, balance between root respiration and leaf net photosynthesis, patterns of assimilate allocation and effect of CO2 level.

Elastic constants of mixed ammonium halides

In the present communication a method based on the three body forces for the evaluation of second and third order elastic constants of mixed ammonium halides has been described. The Lundqvist three body potential is used along with long range Coulombian and short-range overlap repulsive potentials. The latter is taken of the Born-Mayer type and effective up to first neighbours only. It has been assumed that the charge transfer and short-range parameters depend linearly on the composition of solid solutions. Theoretical results obtained, for the entire range of compositions of mixed NH4Cl and NH4Br, have been compared with the recently measured experimental values and the theoretical results of other workers, whenever these are available.

Quantum effects and competing interactions in crystals of the mixed rubidium and ammonium dihydrogen phosphate system.

Quantum corrections are introduced in a simple two-sublattice model, which describes well both para-ferro (${T}_{C}$) and para-antiferroelectric (${T}_{N}$) phase transitions in mixed crystals of the potassium dihydrogen phosphate family, leading to a determination of the phase diagram in satisfactory agreement with that observed in rubidium and ammonium dihydrogen phosphate mixed crystals.

The inhibition of ammonium uptake by nitrate in wheat

summaryThe improvement of root growth in hydroponically grown crop plants such as wheat when nitrate is added to an ammonium‐only nitrogen source is possibly brought about by a suppression of the over‐rapid absorption of ammonium by nitrate, thus alleviating the stress imposed by root‐based ammonium assimilation on the supply of carbon skeletons required for root growth.The degree of suppression of ammonium absorption by nitrate in hydroponically grown wheat was investigated by measuring the relative rates of absorption of 15N from nutrient solutions containing 2 mM l6N nitrate, 2 HIM 15N ammonium, 2 mM 14N nitrate + 2 mM 15N ammonium, 2 mM 14N nitrate + 2mM 14N ammonium or 3 mM 14N nitrate + 1 mM 15N ammonium.After 8 h 15N feeding, 24% more 15N was found in ammonium‐only fed plants than in nitrate‐only fed plants. The l5N content of plants fed equal concentrations of 14N nitrate and l5N ammonium was 44 % lower than that of 15N ammonium‐only fed plants; those fed a 3:1 mixture of 14N nitrate and l5N ammonium had a 15N content 68%, lower than that of 15N ammonium‐only fed plants. The l5N nitrate +14N ammonium fed plants possessed a 15N content 32% below that of 15N nitrate‐only fed plants.It thus appears that not only is there a measure‐able suppressive effect of ammonium on the uptake of nitrate ions by wheat plants but that the inverse effect is even more pronounced and could account for observed effects of mixed ammonium + nitrate nutrition on root growth.

Ammonium and nitrate nutrition inPlantago lanceolata L. andPlantago major L. ssp.major

With the aims (1) to test whether the different natural occurrence of two Plantago species in grasslands is explained by a different preference of the species for nitrate or ammonium; (2) to test whether the different occurrence is explained by differences in the flexibility of the species towards changes in the nitrogen form; (3) to find suitable parameters as a tool to study ammonium and nitrate utilization of these species at the natural sites in grasslands, plants of Plantago lanceolata and P. major ssp. major were grown with an abundant supply of nitrate, ammonium or nitrate + ammonium as the nitrogen source (0.5 mM). The combination of ammonium and nitrate gave a slightly higher final plant weight than nitrate or ammonium alone. Ammonium lowered the shoot to root ratio in P. major. Uptake of nitrate per g root was faster than that of ammonium, but from the mixed source ammonium and nitrate were taken up at the same rate. In vivo nitrate reductase activity (NRA) was present in both shoot and roots of plants receiving nitrate. When ammonium was applied in addition to nitrate, NRA of the shoot was not affected, but in the root the activity decreased. Thus, a larger proportion of total NRA was present in the shoot than with nitrate alone. In vitro glutamate dehydrogenase activity (GDHA) was enhanced by ammonium, both in the shoot and in the roots. In vitro glutamine synthetase activity (GSA) was highest in roots of plants receiving ammonium. . Both GDHA and GSA were higher in P. lanceolata than in P. major. The concentration of ammonium in the roots increased with ammonium, but it did not accumulate in the shoot. The concentration of amino acids in the roots was also enhanced by ammonium. Protein concentration was not affected by the form of nitrogen. Nitrate accumulated in both the shoot and the roots of nitrate grown plants. When nitrate in the solution was replaced by ammonium, the nitrate concentration in the roots decreased rapidly. It also decreased in the shoot, but slowly. It is concluded that the nitrogen metabolism of the two Plantago species shows a similar response to a change in the form of the nitrogen source, and that differences in natural occurrence of these species are not related to a differential adaptation of nitrogen metabolism towards the nitrogen form. Suitable parameters for establishing the nitrogen source in the field are the in vivo NRA, nitrate concentrations in tissues and xylem exudate, and the fraction of total reduced nitrogen in the roots that is in the soluble form, and to some extent the in vitro GDHA and GSA of the roots. 'Grassland Species Research Group. Pubi, no 118.

Chemical preparation of PLZT powders by the carbonate method

PLZT powders were prepared by the adsorption-type coprecipitation method, in which mixed ammonium carbonate and ammonium hydroxide aqueous solution was used as a precipitant. The resulting precipitates are mixtures of carbonates and hydroxides. After calcining at 600°C a powder was obtained, consisting of two phases of the zirconium-rich and the titanium-rich perovskite structures with lattice parameters of about 4·13 Å and 3·99 Å, respectively. As calcination temperature increased, these two phases tended to dissolve each other gradually, and then a single perovskite structure appeared as the temperature rose above 900°C. By the results of X-ray diffraction, SEM, TEM and DTA/TGA, the behavior of coprecipitated powders and calcining treatments have been discussed. The atmosphere sintering technique was used to examine the sinterability of the PLZT powders, and a transparent PLZT ceramic was thus obtained.

Measurement of the water cycle in mixed ammonium acid sulfate particles

A single ammonium-hydrogen-sulfate particle is levitated in an evacuated quadrupole trap at room temperature and the temperature of an attached tube containing bulk water is slowly cycled introducing then removing water vapor. With increasing pressure the particle dissolves in stages, then grows as a solution droplet by water absorption. With decreasing pressure the droplet supersaturates, crystallizes, then dehydrates completely to return to its initial state. Particle mass, and thus composition, is measured continuously with an electrostatic balance. Twenty-six cycles were studied as solute composition ranged from ammonium bisulfate through letovicite to ammonium sulfate in roughly equal steps. Composition was changed in situ by reaction with ammonia at low partial pressure. With solute composition characterized by x = [NH 4]/[SO 4], deliquescence was found to occur at water activity a w = 0.394−0.029 ( x− 1) for 1 ⩽ x < 1.5 and a w = 0.710−0.023( x−1.5) for 1.5 ⩽ x < 2. Particle growth occurs at deliquescence and subsequently is in excellent agreement with that predicted in a model proposed by Tang for dissolution of a two-component mixed solute. Water activities of the solution droplets are measured up to a w = 0.9. The results are compared with those predicted by the Zdanovskii-Stokes-Robinson method of interpolation from binary data and with those obtained using the mixing rule of Meissner and Kusik. Particle crystallization from supersaturated solution is analyzed thermodynamically using measured water activities, the Gibbs-Duhem equation, and classical nucleation theory. The specific free energy barrier to crystallization, ΔG/ n, is found to increase from near zero to 0.04 eV as composition ranges from x = 1 to 2, where n is the number of formula units in the critical nucleus. New phase diagrams are presented and used to discuss the dynamics of mixed sulfate particles in the atmosphere.

Physico-chemical speciation and transformation reactions of particulate atmospheric nitrogen and sulphur compounds

Using X-ray powder diffraction it is possible to identify a number of discrete compounds of nitrogen and sulphur in atmospheric aerosols. The compounds observed include ammonia neutralization products of airborne acids, including mixed ammonium nitrate-sulphate salts. Products of hydrogen halide displacement by HNO 3 and H 2SO 4 are identified both from size-differentiated ion balance studies and X-ray diffraction. A number of mixed metal-ammonium sulphate salts are attributed to reactions of ammonium sulphate subsequent to aerosol coagulation processes.

Root respiration and bacterial population of roots I. Effect of nitrogen source, potassium nutrition and aeration of roots

AbstractSpring wheat was grown in nutrient solution culture to investigate the influence of aeration, different sources of nitrogen and discontinuation of potassium supply on root respiration and on the number of root bacteria. By definition root respiration included oxygen consumption of the excised roots and their microbial colonizers.Root respiration was subject to diurnal variations. It was low towards the end of the dark period and increased within two hours during the light period.Independent of the nutrient supply the respiration rate and bacterial number were considerably higher in unaerated than in aerated nutrient solution. Root respiration was lowest when using nitrate as a source of nitrogen and highest with ammonium nutrition. Intermediate respiration rates were obtained for mixed nitrogen nutrition. Respiration corresponded to the bacterial colonization of the roots.The discontinuation of potassium supply led in plants supplied with nitrate to an insignificant increase in root respiration, whereas a marked increase in respiration was observed in plants with mixed ammonium and nitrate nutrition. In contrast, Root respiration of plants supplied with ammonium declined when potassium was discontinued.Discontinuation of potassium supply caused an increase in root respiration and bacterial numbers in both aerated and unaerated media.

Quantitative determination of sulphate in individual aerosol particles

The vapour-deposited thin-film method of analysing individual aerosol particles is shown to provide a method for quantitative determination of sulphate. The method utilizes a calibration curve which relates the mass of sulphate in a particle to the diameter of the reaction ring it produces with a thin layer of barium chloride. A single calibration curve was shown to apply to ammonium sulphate, sulphuric acid and mixed ammonium sulphate/sodium chloride particles. Masses of as little as 10 −17 g sulphate, corresponding to particle diameters of ~0.03 μm, were determined to +41%, −29% accuracy with this technique.

On the concentration and size distribution of atmospheric sulfate particles under rural conditions

The concentration and size distribution of ammonium sulfate particles were studied at a rural sampling site by using morphological identification. The size distribution of pure and mixed ammonium sulfate particles as well as the sulfate fraction of total aerosol and its size dependence were determined in the 0.02–0.3 μm radius range. The averaged results are presented for the summer and winter months.