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.

Ammonia emission from young barley plants: influence of N source, light/dark cycles and inhibition of glutamine synthetase

Abstract: Barley (Hordeum vulgare L cv Golf) plants were grown at two different relative addition rates ; 01 and 02 d -1 of nitrate Three to five days before measurements started the plants were transferred to a nutrient solution with 2 mM nitrate or ammonium The ammonium-grown plants showed increased ammonium levels in both shoots and roots and also increased ammonium concentrations in xylem sap Ammonia emission measured in cuvettes connected to an automatic NH 3 monitor was close to zero for nitrate-grown plants but increased to 059 and 088 nmol NH 3 m -2 s -1 for plants transferred to ammonium after growing at RA = 02 and 01 d -1 , respectively In darkness, NH 3 emission decreased together with photosynthesis and transpiration, but increased rapidly when the light was turned on again Addition of 05 mM methionine sulphoximine (MSO) to the plants caused an almost complete inhibition of both root and shoot glutamine synthetase (GS) activity after 24 h Ammonia emission increased dramatically and photosynthesis and transpiration decreased in both nitrate- and ammonium-grown plants as a result of the GS inhibition At the same time plant tissue and xylem sap ammonium concentrations increased, indicating the importance of GS in controlling plant ammonium levels and thereby NH 3 emission from the leaves

Effect of Media Nitrogen Concentration on Biofilter Performance

Abstract: A pilot-scale biofilter was used to determine important design and operational parameters related to biofiltration of volatile organic compounds (VOCs). The importance of nitrogen availability in terms of biofilter performance was determined. Results showed that microbially accessible nitrogen (ammonia and nitrate) in the areas of highest microbial activity were depleted when toluene loading rates were 30 g/m3-h or greater. This depletion led to a marked reduction in performance in terms of the VOC elimination rate of the biofilter. The amount of nitrogen available to microorganisms can be depleted by microbial uptake of soluble nitrogen to make new biomass, stripping of ammonia, denitrification of nitrate, and leaching. Nitrogen is made available by mineralization of biomass, mineralization of organic nitrogen to soluble nitrogen, and addition of nitrogen fertilizers. Mineralization of biomass to ammonia results in the recycle of nitrogen through the system. Even though organic nitrogen in the m...

Nitrate reduction and assimilation in Chlorella

Abstract: 1. Nitrate reduction and assimilation have been studied in Chlorella pyrenoidosa under growth conditions by observing effects on the CO(2)/O(2) gas exchange quotient. 2. During assimilation of glucose in the dark, nitrate reduction is noted as an increase in the R.Q. to about 1.6 caused by an increased rate of carbon dioxide production. 3. During photosynthesis at low light intensity nitrate reduction is evidenced by a reduction in the CO(2)O(2) quotient to about 0.7 caused by a decreased rate of carbon dioxide uptake. 4. Chlorella will assimilate nitrogen from either nitrate or ammonia. When both sources are supplied, only ammonia is utilized and no nitrate reduction occurs. It is inferred that under the usual conditions of growth nitrate is reduced only at a rate required for subsequent cellular syntheses. The effect of nitrate reduction on the CO(2)O(2) quotient therefore provides a measure of the relative rate of nitrogen assimilation. 5. Over-all photosynthetic metabolism may be described from elementary analysis of the cells since excretory products are negligible. The gas exchange predicted in this way is in good agreement with the observed CO(2)/O(2) quotients.

Electrocatalytic reduction of nitrate on activated rhodium electrode surfaces

Abstract: Electrodeposited rhodium films on titanium substrates have been electrochemically activated to produce a high area surface with a specific activity for nitrate electroreduction directly to N2. The activation process involves oxidation/reduction cycles in an alkaline, KCl electrolyte containing nitrate ions. Surfaces of up to 230 times the geometric area are achieved, together with a surface morphological modification. While the active surface, once formed, is intrinsically unstable during long-term nitrate reduction, its activity can be maintained in situ by an electrochemical cycling procedure. The high area rhodium has the form of a nano-structured ‘sponge’, with a surface area of ca. 19 m2 g−1. The morphological modification is evidenced by a change in the hydrogen UPD structure, changes in the surface redox behaviour associated with OH adsorption, and a reduction in the activation energy for nitrate reduction from ca. 47 to 20 kJ mol−1. The reduction in activation energy, however, is accompanied by a decrease in the pre-exponential factor, and this apparent compensation effect results in similar rate constants on the activated and unactivated surfaces. The enhancement in the catalyst's activity for nitrate reduction results from an increase in the relative activity of nitrate reduction over water reduction. The activated catalyst sustains steady state nitrate reduction at an increased over-potential before the reaction to N2 decays, and hydrogen evolution and reduction to ammonia take place. The presence of nitrate ions is essential for the formation of the active surface, and specifically adsorbed nitrate ions and reductive intermediates are present at the surface when it is reformed. A mechanism for the elementary surface reaction steps involved in nitrate reduction, and the apparent ‘habit’ growth of the active surface phase in the nitrate containing solution is discussed.