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.

New approaches to prepare nitrogen-doped TiO2 photocatalysts and study on their photocatalytic activities in visible light

Abstract: Nitrogen-doped TiO2 nanocatalysts were successfully synthesized by adjusting a pH range using the ammonium nitrate and ammonia water as the nitrogen source. The samples were characterized by XRD, XPS and UV-DRS. When the total amount of ammonium nitrate and ammonia water was unchanged, different pH values were modified by changing the NH4NO3/NH3·H2O ratio to prepare nitrogen-doped TiO2. The prepared photocatalyst showed the highest photo-activity for the degradation of 2,4-dichlorophenol (2,4-DCP) under visible light when prepared at pH 5.87. XPS analysis showed the presence of nitrogen in two states doped in TiO2. The results indicated the photocatalytic activity of N-TiO2 is varied with the change of pH values, the amount of the nitrogen sources and water. The experimental results showed that the higher activity is due to the variation in the concentration and states of nitrogen-doped in TiO2. In the preparation methods, the photocatalyst was treated with the hydrogen peroxide before calcination, resulting in the decrease of nitrogen doped into the lattice and the photo-degradation rate of 2,4-DCP. The results suggested that the nitrogen source could be doped into the crystal lattice only in the form of reduction state as NH4+ ion during the calcination process.

Mechanistic analysis of ammonium inhibition of atmospheric methane consumption in forest soils.

Abstract: Methane consumption by forest soil was studied in situ and in vitro with respect to responses to nitrogen additions at atmospheric and elevated methane concentrations. Methane concentrations in intact soil decreased continuously from atmospheric levels at the surface to 0.5 ppm at a depth of 14 cm. The consumption rate of atmospheric methane in soils, however, was highest in the 4- to 8-cm depth interval (2.9 nmol per g of dry soil per day), with much lower activities below and above this zone. In contrast, extractable ammonium and nitrate concentrations were highest in the surface layer (0 to 2 cm; 22 and 1.6 μmol per g of dry soil, respectively), as was potential ammonium-oxidizing activity (19 nmol per g of dry soil per day). The difference in zonation between ammonium oxidation and methane consumption suggested that ammonia-oxidizing bacteria did not contribute significantly to atmospheric methane consumption. Exogenous ammonium inhibited methane consumption in situ and in vitro, but the pattern of inhibition did not conform to expectations based on simple competition between ammonia and methane for methane monooxygenase. The extent of ammonium inhibition increased with increasing methane concentration. Inhibition by a single ammonium addition remained constant over a period of 39 days. In addition, nitrite, the end product of methanotrophic ammonia oxidation, was a more effective inhibitor of methane consumption than ammonium. Factors that stimulated ammonium oxidation in soil, e.g., elevated methane concentrations and the availability of cosubstrates such as formate, methanol, or β-hydroxybutyrate, enhanced ammonium inhibition of methane oxidation, probably as a result of enhanced nitrite production.

Response of Inorganic PM to Precursor Concentrations

Abstract: An inorganic aerosol equilibrium model is used to investigate the response of inorganic particulate matter (PM) concentrations with respect to the precursor concentrations of sulfuric acid, ammonia, and nitric acid over a range of temperatures and relative humidities. Diagrams showing regions of PM response to precursor concentrations are generated, thus allowing the qualification of assumptions concerning the response of PM to sulfate and overall sensitivity to ammonia and nitric acid availability. The PM concentration level responds nonlinearly to sulfate and shows overall sensitivity to ammonia and nitric acid availability for specific atmospheric conditions and precursor concentrations. The generated diagrams are applied as a means of approximating the PM response to precursor concentrations for two urban polluted areas. In both cases, reductions in ammonia emissions have the most significant impact on the total PM level. However, such a reduction will result in significant increases in atmospheric acidity.

Ammonia Volatilization from Ammonium or Ammonium-Forming Nitrogen Fertilizers

Abstract: Ammonia (NH3) loss is only one of several ways nitrogen (N) can be lost from the plant environment. Nitrogen can leach below the root zone with water, nitrate can be reduced to gaseous forms in anaerobic environments, and NH3 can be lost to the atmosphere when N fertilizer is applied to the soil surface. The intensity of loss from each mechanism depends on water content, temperature, soil texture, form of nitrogen, and other environmental factors. Fertilizer N use efficiency can vary from one environment to another. An agricultural producer can reasonably expect half of the applied N fertilizer to be recovered by the current crop. It is the portion that is unaccounted for in the crop that is addressed by much of the current research. Effective use of applied N by the crop will reduce input cost per unit of product harvested.