Ammonia

About: Ammonia is a research topic. Over the lifetime, 16217 publications have been published within this topic receiving 271940 citations. The topic is also known as: NH3 & azane.

Amino acid extraction and ammonia metabolism by the human kidney during the prolonged administration of ammonium chloride.

Abstract: According to current concepts, renal ammonia synthesis may be attributed to the renal extraction and catabolism of certain plasma amino acids. In 1943, Van Slyke and associates demonstrated in the dog that the amide nitrogen of glutamine was removed from arterial plasma in quantities sufficient to account for approximately 60 per cent of the urinary ammonia excreted during metabolic acidosis (1). It was proposed that the remaining 40 per cent of urinary ammonia could be accounted for by the renal uptake of plasma a-amino nitrogen. In agreement with this hypothesis, many investigators have since shown that the administration of several amino acids other than glutamine is associated with an increased urinary ammonia excretion (2-4). Loading experiments of this type have indicated thatbesides glutamine-glycine, alanine, asparagine, leucine. and histidine may serve as precursors of urine ammonia. The demonstration of appropriate enzyme systems within renal tissue capable of forming ammonia from these substrates has been offered as additional support for the thesis that several plasma amino acids may participate normally in the renal production of ammonia. Nevertheless, the specific amino acids that serve as renal ammonia precursors have not been identified clearly in conditions associated with normal acid-base balance and normal plasma amino acid concentrations. The present study was undertaken for two principal reasons: first, to characterize the' typical patterns of uptake or release

Selective Dinitrogen Conversion to Ammonia Using Water and Visible Light through Plasmon‐induced Charge Separation

Abstract: The generation of ammonia from atmospheric nitrogen and water using sunlight is a preferable approach to obtaining ammonia as an energy carrier and potentially represents a new paradigm for achieving a low-carbon and sustainable-energy society. Herein, we report the selective conversion of dinitrogen into ammonia through plasmon-induced charge separation by using a strontium titanate (SrTiO3) photoelectrode loaded with gold nanoparticles (Au-NPs) and a zirconium/zirconium oxide (Zr/ZrOx ) thin film. We observed the simultaneous stoichiometric production of ammonia and oxygen from nitrogen and water under visible-light irradiation.

Effects of pH and Oxygen and Ammonium Concentrations on the Community Structure of Nitrifying Bacteria from Wastewater

Abstract: Autotrophic nitrifying bacteria that oxidize ammonium to nitrite and nitrate are found in soils, sediments, wastewaters, freshwater, and marine water and on building facades. They are essential components of the nitrogen (N) cycle, linking the most reduced and most oxidized forms of inorganic N. Nitrification occurs as a two-step process carried out by two distinct groups of bacteria; ammonia-oxidizing bacteria convert ammonia to nitrite, and then nitrite oxidizers convert nitrite to nitrate (22, 30). Environmental factors control the rate of nitrification. The most significant environmental factors are substrate concentration, pH, temperature, and oxygen availability (12, 23). Nitrifying bacteria exhibit different substrate concentration sensitivities (26). Media containing low substrate concentrations (10 mg of NH4+ liter−1) can give larger most-probable-number counts of ammonia oxidizers than media containing higher NH4+ concentrations (6, 26). Also, ammonia oxidation is inhibited at high substrate concentrations. The growth rates of Nitrosomonas spp. cultures were reduced in the presence of 1,050 to 2,800 mg of NH4+-N liter−1 (16). Substrate inhibition of ammonia oxidation has also been observed in studies of wastewater systems (23). Natural environments, such as soil and water, usually contain 1 to 10 mg of NH4+-N liter−1 (22), yet liquid wastes from animal farms give rise to concentrations up to 1,600 or 5,600 mg of NH4+-N liter−1 (5, 17). Free ammonia (NH3) rather than the total ammonium concentration inhibits ammonia oxidizers (1). As the ratio between the ionized form and the nonionized form depends on pH, the toxicity of ammonium also depends on the environmental pH. The pH range for growth of pure cultures of ammonia oxidizers is 5.8 to 8.5, and the pH range for growth of nitrite oxidizers is 6.5 to 8.5 (30). Nitrification was inhibited at pH values below 5.8 in our preliminary experiments performed with an enriched culture of nitrifiers obtained from wastewater. Yet in natural environments, such as soil, nitrification has been reported to occur at pH values below 4.0 (7, 29). Limiting amounts of dissolved oxygen (concentrations below 2 mg liter−1) inhibit nitrification and cause nitrite accumulation or nitrous and nitric oxide production (9, 21). Ammonia-oxidizing bacteria are the key functional group in removing ammonium from wastewaters. Knowledge of the effect of oxygen on nitrification and nitrifying populations has economic importance since aeration of activated sludge is one of the most costly items in the operation of a wastewater treatment plant (21). In environments with high inputs of ammonium, such as wastewaters, biooxidation of this substrate increases the oxygen uptake and lowers the pH. Such modifications of the environment not only affect the production of nitrite and nitrate but can also select a different nitrifying community that is perhaps specialized for these new conditions. Nitrification does occur in extreme environments that pure cultures of nitrifiers cannot tolerate (4). In this study we examined extreme environments in which nitrifying bacteria may be viable but have not been cultured thus far. Because of the difficulty of obtaining nitrifier isolates, nucleic acid-based methods have greatly aided studies of the diversity of nitrifiers (11, 20, 27, 28). Recent molecular investigations have provided valuable information concerning the diversity of ammonia oxidizers in natural environments (5, 15, 20, 25). However, no previous study has focused on the structural or compositional responses of nitrifying communities to perturbations in the environment. In the present laboratory study we examined the effects of high ammonium concentrations, different pH values, and different oxygen concentrations on nitrification and on the community structure of nitrifying bacteria from wastewater. To test the abilities of the communities to regain their original structures, growth of nitrifying communities under the new conditions was followed by incubation under the original conditions.

The reduction of mono-coordinated molecular nitrogen to ammonia in a protic environment

Abstract: WE have reduced ligating molecular nitrogen (dinitrogen) to ammonia in yields of up to 90% at a single metal site This reaction is important for its possible application to our understanding of the chemical mechanism of the reduction of dinitrogen to ammonia by nitrogenase, where the reduction may occur at a single molybdenum ion site1 Our reaction occurs when compounds of the type [M(N2)2(PR3)4](I; M =Mo or W; R = alkyl or aryl) are treated at room temperature with sulphuric acid in methanol solution: This reaction was performed in a vacuum so that the evolved gases could be analysed and measured On mixing the reagents, one molecule of nitrogen gas was rapidly evolved with a trace of dihydrogen The remaining dinitrogen was spontaneously reduced to ammonia together with some hydrazine, presumably also with concomitant oxidation of the metal M