Ammonia fluxes

DENMEAD, O. T., SIMPSON, J.R. (1974). Ammonia flux into the atmosphere from a grazed pasture. Science, 185, 609-610. 

Langford, A. O., F. C. Fehsenfeld, J. Zachariassen, and D. S. Schimel, Gaseous Ammonia Fluxes and Background Concentrations in Terrestrial Ecosystems of the United States, Global Biogeochem. Cycl., 6, 459-483 (1992). 

Gardner, W. S., Seitzinger, S. P., and Malczyk, J. M. (1991). The effects of sea salts on the forms of nitrogen released from estuarine and freshwater sediments Does ion pairing affect ammonia flux Estuaries 14, 157-166. 

The structures with self-organized GaN/AlN QDs were grown by molecular beam epitaxy (MBE) on (0001) sapphire substrates. Ammonia was used as the source of active nitrogen. A single layer of GaN QDs was formed on the AIN buffer surface by a particular MBE growth mode at relatively low substrate temperatures (Ts 540°C). A beam equivalent pressure (BEP) of gallium flux was 5.4T0 Torr and BEP of ammonia flux was 10" Torr. To obtain GaN QDs... 

Figure 5. Ammonia flux versus lagoon temperature comparison between WATER9 modelling results and dynamic chamber experimental calculated results.

Arkinson, H.L., Measurements, Modeling, and Analysis of Ammonia Flux from Hog Waste treatment technologies, M.S. Thesis, pp.l29, 2003. 

Warland JS, Dias GM, Thurtell GW. 2001. A tunable diode laser system for ammonia flux measurements over multiple plots. Environ Pollut 114(2) 215-221. 

Lenhard, U., and G. Gravenhorst (1980). Evaluation of ammonia fluxes into the free atmosphere over Western Germany. Tellus 32, 48-55. 

A gas absorber is used to remove ammonia from air by scrubbing the gas mixture with water at 300 K and 1 atm. At a certain point in the absorber, the ammonia mole fraction in the bulk of the gas phase is 0.80, while the corresponding interfacial ammonia gas-phase concentration is 0.732. The ammonia flux at that point is measured as 4.3 x 10"4 kmol/m2-s. Neglecting the evaporation of water, calculate the mass-transfer coefficient in the gas phase at that point in the equipment. 

Neglecting water evaporation and the solubility of air in water, in the gas phase this is a case of diffusion of A (ammonia) through stagnant B (air). However, because of the high ammonia concentration, -type coefficients should not be used instead, use equation (2-2) to solve for FG. In this case, since the ammonia flux is from the bulk of the gas phase to the interface, yAl = 0.8 and yA2 = 0.732. 

To estimate the ammonia flux and the interfacial concentrations at this particular point in the column, use equation (3-15) to calculate... 

As a double check on the calculations so far, calculate the ammonia flux based on the conditions in the liquid phase,... 

The two estimates of the flux agree within the round-off error. Notice that in this example it was not necessary to calculate the interfacial concentrations to estimate the ammonia flux since the use of overall coefficients was appropriate. They were calcu-... 

Dll. We have steady-state diffusion of ammonia in air across a film that is 0.033 mm thick On one side of the film, the ammonia concentration is 0.000180 and on the other side it is 0.000257 kmol/m. We desire an ammonia flux rate of 9.60 x 10 kmol/(m s). The apparatus is at 0.90 atm. Use the Chapman-Enskog theory to estimate the diffusivity. Find the required operating temperature. 

CoF is used for the replacement of hydrogen with fluorine in halocarbons (5) for fluorination of xylylalkanes, used in vapor-phase soldering fluxes (6) formation of dibutyl decalins (7) fluorination of alkynes (8) synthesis of unsaturated or partially fluorinated compounds (9—11) and conversion of aromatic compounds to perfluorocycHc compounds (see Fluorine compounds, organic). CoF rarely causes polymerization of hydrocarbons. CoF is also used for the conversion of metal oxides to higher valency metal fluorides, eg, in the assay of uranium ore (12). It is also used in the manufacture of nitrogen fluoride, NF, from ammonia (13). 

FIG. 23-3 Temperature and composition profiles, a) Oxidation of SOp with intercooling and two cold shots, (h) Phosgene from GO and Gfi, activated carbon in 2-in tubes, water cooled, (c) Gumene from benzene and propylene, phosphoric acid on < uartz, with four quench zones, 260°G. (d) Mild thermal cracking of a heavy oil in a tubular furnace, hack pressure of 250 psig and sever heat fluxes, Btu/(fr-h), T in °F. (e) Vertical ammonia svi,ithesizer at 300 atm, with five cold shots and an internal exchanger. (/) Vertical methanol svi,ithesizer at 300 atm, Gr O -ZnO catalyst, with six cold shots totaling 10 to 20 percent of the fresh feed. To convert psi to kPa, multiply by 6.895 atm to kPa, multiply by 101.3. 

Steam reforming is an important proeess to generate hydrogen for sueh uses as ammonia synthesis beeause of the high endothermie heat reaetion and its rapidity. High heat fluxes with a direet-fired furnaee are required. Although many steps of reaetions are possible, the typieal reaetion steps are as follows ... 

Fig. 10-13. The links between the cycling of C, N, and O2 are indicated. Total primary production is composed of two parts. The production driven by new nutrient input to the euphotic zone is called new production (Dugdale and Goering, 1967). New production is mainly in the form of the upward flux of nitrate from below but river and atmospheric input and nitrogen fixation (Karl et al, 1997) are other possible sources. Other forms of nitrogen such as nitrite, ammonia, and urea may also be important under certain situations. The "new" nitrate is used to produce plankton protoplasm and oxygen according to the RKR equation. Some of the plant material produced is respired in the euphotic zone due to the combined efforts...

Fig. 12-5 The ammonia-ammonium cycle. Each arrow represents one flux. The magnitude of the flux is given in Tg N/yr Where two numbers are given, the top value is the anthropogenic contribution and the lower is the total flux (natural + anthropogenic).

Recently, high-quality SOD membranes for water separation have been developed by Khajavi etal. [21, 52]. These zeolite membranes should allow an absolute separation of water from almost any mixture since only very small molecules such as water, hydrogen, helium, and ammonia can theoretically enter through the six-membered window apertures. Water/alcohol separation factors 10 000 have been reported with reasonable water fluxes up to 2.25 kg nr h at 473 K in pervaporation experiments. 

Ivey and Morris (1962) reported the ratio of subcooled critical flux to saturated critical flux of pool boiling in water, ethyl alcohol, ammonia, carbon tetrachloride, and isooctane for pressures from 4.5 to 500 psia (0.3 to 34 X 105 Pa) as... 

The neutron activation method for the determination of arsenic and antimony in seawater has been described by Ryabin et al. [66]. After coprecipitation of arsenic acid and antimony in a 100 ml sample of water by adding a solution of ferric iron (10 mg iron per litre) followed by aqueous ammonia to give a pH of 8.4, the precipitate is filtered off and, together with the filter paper, is wrapped in a polyethylene and aluminium foil. It is then irradiated in a silica ampoule in a neutron flux of 1.8 x 1013 neutrons cm-2 s 1 for 1 - 2 h. Two days after irradiation, the y-ray activity at 0.56 MeV is measured with use of a Nal (Tl) spectrometer coupled with a multichannel pulse-height analyser, and compared with that of standards. 

Figure 3. The general nitrogen model for illustrating the bio geochemical cycling in Forest ecosystems. Explanations for the fluxes 1, ammonia volatilization 2, forest fertilization 3, N2-fixation 4, denitrification 5, nitrate respiration 6, nitrification 7, immobilization 8, mineralization 9, assimilatory and dissimilatory nitrate reduction to ammonium 10, leaching 11, plant uptake 12, deposition N input 13, residue composition, exudation 14, soil erosion 15, ammonium fixation and release by clay minerals 16, biomass combustion 17, forest harvesting 18, litterfall (Bashkin, 2002).

The first example of a dynamic flux analysis was a study performed in the 1960s [269]. In the yeast Candida utilis, the authors determined metabolic fluxes via the amino acid synthesis network by applying a pulse with 15N-labeled ammonia and chasing the label with unlabeled ammonia. Differential equations were then used to calculate the isotope abundance of intermediates in these pathways, with unknown rate values fitted to experimental data. In this way, the authors could show that only glutamic acid and glutamine-amide receive their nitrogen atoms directly from ammonia, to then pass it on to the other amino acids. 

K,Rb,Cs) SmGeSe4 and similar compounds have been prepared using K2Se2, Rb2Se3, Cs2Se2 fluxes. These were prepared from the stoichiometric combination of the elements in liquid ammonia (Martin and Dorhout 2004). 

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