Molar Ratio Of NH Research Articles

Source of nitrogen in wet deposition to a rice agroecosystem at Tai lake region

Nitrogen (N) in wet deposition can provide significant nutrients to algae, which potentially contributes to eutrophication in waterbodies, and to nutrient surplus of rice–wheat crops in the Tai lake region, Jiangsu Province, China. Quantifying the N compounds in wet deposition and determining their sources is important to understand how to control eutrophication in lakes and to improve recommendations for fertilizer use. In this study, the concentrations of inorganic N, molar ratios of NH 4 +/NO 3 − and the natural 15N abundance of NH 4 + ( δ 15NH 4 +) in wet deposition were determined for 78 precipitation events between June 2003 and July 2005. Samples were collected at two sites in Tai lake region, a watershed rice agroecosystem currently experiencing eutrophication. The average N wet deposition amounted to 27 kg N ha −1 yr −1, with 60% in the form of NH 4 +. Annually, two cycles of depleted and enriched δ 15NH 4 + indicate the shifting of main source of NH 3 volatilization between chemical fertilizer and excreta of local residents and domestic animals, surface waters, and other organic N. The peak in NH 4 +/NO 3 − ratio, coupled with depleted δ 15NH 4 + in mid-June, coincided with the rice-transplanting period, which is indicative of surplus fertilizer application. Enriched δ 15NH 4 + values in August–October and in April–May were indicative of enhanced emissions from excreta and polluted waterbodies in the warmer seasons. Findings suggest that δ 15NH 4 + could be used to indicate the sources of NH 3 volatilization, and the NH 4 +/NO 3 − ratio to indicate the intensity of wet N deposition.

Vanadium-loaded carbon-based monoliths for the on-board NO reduction: Experimental study of operating conditions

Abstract Selective catalytic reduction (SCR) with NH 3 and most probably with urea is unanimously regarded as one of the most promising technologies for the abatement of NO x on-board. For this application at low temperatures, carbon-based monolithic catalysts have been prepared using a blend of polymers on cordierite monoliths, doped with two different vanadium compounds and two different loadings (3 and 5%). The active phase precursors were either the ashes of a petroleum coke (PCA) or a commercial NH 4 VO 3 . An experimental design was carried out to study the reduction of NO emissions, the selectivity towards N 2 and the release of ammonia-slip in the outlet reactor gasses. Both primary measures (temperature, gas space velocity per hour (GSVH) and the molar ratio of NH 3 /NO) as well as secondary SNR influences were evaluated using a 2 3 factorial design for the two types of catalysts. Polinomial modellings were deducted from statistical analysis of the experiments, and a good agreement between models and measured data was obtained. The evaluation showed that the temperature is the variable which has a greater influence on all the response variables studied. Spatial velocity shows approximately an equal importance on NO conversion and selectivity towards N 2 whereas the molar ratio of NH 3 /NO is only an important factor in the interaction to other parameters. Catalysts prepared using PCA have similar catalytic behaviour than those prepared with NH 4 VO 3 . Although they show a slightly lower catalytic activity, similar selectivity towards N 2 and higher values of ammonia-slip. The physical–chemical features of the catalysts, analysed by N 2 physisorption, ammonia adsorption and temperature programme desorption have a close relation with the catalysts behaviour. The physical–chemical features are of key importance for achieving a considerable catalytic activity. The values of apparent activation energy calculated for the catalysts presented in this paper were similar to other carbon-based catalysts and smaller than the ones corresponding to TiO 2 -supported systems.

A simple method for the removal of thiols on gold surfaces using an NH4OH–H2O2–H2O solution

The removal behavior of self-assembled monolayers (SAMs) of thiol molecules on a gold substrate by an NH(4)OH-H(2)O(2)-H(2)O solution was studied using attenuated total reflectance infrared spectroscopy (ATR-IR) and atomic force microscopy (AFM). Furthermore, the impact of the concentration of NH(4)OH and H(2)O(2) in the solution and reaction temperature on the SAM removal rate and efficiency was explored. The SAM removal rate and efficiency were significantly influenced by the concentration of NH(4)OH rather than H(2)O(2). The solution containing the 2 : 1 molar ratio of NH(4)OH : H(2)O(2) among three different solutions showed the highest removal rate and efficiency in the removal of 11-mercapto-1-undecanol. The increase in the reaction temperature resulted in the enhancement on the SAM removal rate, but it led to the fast delamination of the gold layer. These results may be useful in the regeneration of sensor surfaces relying on gold/thiol chemistry.

Influence of Ammonium and Nitrate Nutrition on Plant Growth and Zinc Accumulation by Indian Mustard

ABSTRACT The source of nitrogen (N) used in soil fertility practices affects plant growth, nutrient absorption, and the availability of nutrients. Consequently, the potential of plants to extract zinc (Zn) from soils may be increased by controlling the ratio of NH4 + to NO3 − to maximize growth and Zn accumulation. The objectives of this research were to determine the effects of Zn supply and different molar ratios of NH4 + to NO3 − on growth and Zn accumulation in Indian mustard (Brassica juncea Czern.). In a factorial experiment with solution culture, Indian mustard (accession 182921) was supplied with two concentrations of Zn (0.05 and 4.0 mg L−1) in combination with six N treatments with different molar percentage ratios of NH4 + to NO3 − (0:100, 10:90, 20:80, 30:70, 40:60, and 50:50) for three weeks. Zinc supplied at 0.05 mg Zn L−1 represented a common concentration of Zn in solution culture, whereas 4.0 mg Zn L−1 was excessive for plant nutrition. If the supply of Zn in solution was excessive, plants developed symptoms of foliar chlorosis, which became severe if plants were supplied with 80% of N as NO3 −. Supplying high proportions of NO3 − in the nutrient medium stimulated Zn accumulation, whereas increasing proportions of NH4 + (up to 50% of the total N) enhanced shoot growth. The pH of nutrient solutions generally decreased with increasing proportion of NH4 + in solutions and with increased Zn supply. The Zn phytoextraction potential of Indian mustard was maximized, at about 15 mg Zn plant−1, if plants received 10% of the total N as NH4 + and 90% as NO3 −.

Preparation of homodispersed nano zirconia

Direct precipitation was used to prepare nano zirconia in this experiment. The influences of five experimental parameters upon the mean size, yield and dispersity of the product were investigated via uniform design. These parameters were molar ratio of NH 3·H 2O to ZrOCl 2, C 2H 5OH percentage in reacting and washing solutions, ZrOCl 2 concentration, precipitation temperature and surfactant PEG-800 dosage. The condition experiments demonstrated that C 2H 5OH played a significant role in improving the dispersity of the product in the absence of surfactant PEG-800 and the higher the C 2H 5OH percentage, the better the dispersity. By using C 2H 5OH to dissolve ZrOCl 2·8H 2O and conc. NH 3·H 2O respectively and mixing them, we carried out the precipitation in the C 2H 5OH medium to generate hydroxide precursor, which was filtrated, washed with C 2H 5OH, dried and calcined to form well-dispersed uniform nano zirconia.

Transport of liquids using superhydrophobic aerogels

The experimental results of the studies on the transportation of water droplets on a superhydrophobic silica aerogel-powder-coated surface are reported. The superhydrophobic silica aerogels were prepared using sol–gel processing of methyltrimethoxysilane (MTMS) precursor, methanol (MeOH) solvent, and base (NH 4OH)-catalyzed water followed by supercritical drying using methanol solvent. The molar ratio of NH 4OH/MTMS, H 2O/MTMS, and MeOH/MTMS were varied from 1.7 × 10 −1 to 3.5 × 10 −1 , 2 to 8, and 1.7 to 14, respectively, to find out the best-quality aerogels in terms of higher hydrophobicity and high droplet velocity. A specially built device was used for the measurement of velocity of water droplet of size 2.8 mm ( ± 0.2 mm ) on an inclined surface coated with superhydrophobic aerogel powder. Liquid marbles were prepared by rolling water droplets on aerogel powder and the marble(s) velocities on a noncoated inclined surface were compared with that of the water droplets. It was observed that the microstructure of the aerogel affects the droplet as well as marble velocities considerably. For an aerogel with uniform and smaller particles, the water droplet and marble velocities were observed to be maximum, i.e., 144 and 123 cm/s, respectively, whereas for the aerogels with bigger and nonuniform particles, the water droplet and marble velocities were observed to be minimum, i.e., 92 and 82 cm/s, respectively. The results have been discussed by taking into account the contact angles and microstructural observations.

Aerosol Ion Characteristics During the Big Bend Regional Aerosol and Visibility Observational Study

The ionic compositions of particulate matter with aerodynamic diameter ≤2.5 μm (PM2.5) and size-resolved aerosol particles were measured in Big Bend National Park, Texas, during the 1999 Big Bend Regional Aerosol and Visibility Observational study. The ionic composition of PM2.5 aerosol was dominated by sulfate (SO4 2−) and ammonium (NH4 +). Daily average SO4 2− and NH4 + concentrations were strongly correlated (R2 = 0.94). The molar ratio of NH4 + to SO4 2− averaged 1.54, consistent with concurrent measurements of aerosol acidity. The aerosol was observed to be comprised of a submicron fine mode consisting primarily of ammoniated SO4 2− and a coarse particle mode containing nitrate (NO3 −). The NO3 − appears to be primarily associated with sea salt particles where chloride has been replaced by NO3 −, although formation of calcium nitrate (Ca(NO3)2) is important, too, on several days. Size-resolved aerosol composition results reveal that a size cut in particulate matter with aerodynamic diameter ≤1 μm would have provided a much better separation of fine and coarse aerosol modes than the standard PM2.5 size cut utilized for the study. Although considerable nitric acid exists in the gas phase at Big Bend, the aerosol is sufficiently acidic and temperatures sufficiently high that even significant future reductions in PM2.5 SO4 2− are unlikely to be offset by formation of particulate ammonium nitrate in summer or fall.

Study on size distribution of total aerosol and water-soluble ions during an Asian dust storm event at Jeju Island, Korea.

Soil dust particles transported from loess regions of the Asian continent, called Asian dust, highly influences the air quality of north-eastern Asia and the northern Pacific Ocean. In order to investigate the effects of these dust storms on the chemical composition of atmospheric aerosol particles with different size, measurements of size distributions of total aerosol and major ion species were carried out on Jeju Island, Korea during April 2001. Juju Island was chosen for the study because the levels of emissions of anthropogenic air pollutants are very low. A 5-stage cascade impactor was used to sample size-fractionated aerosol particles. Samples were analyzed for major water-soluble ions using Dionex DX-120 ion chromatograph. The average mass concentration of total aerosol was found to be 24.4 and 108.3 microg m(-3) for non-Asian dust and Asian dust periods, respectively. The total aerosol size distribution, measured during the non-Asian dust period, was bimodal, whereas the coarse particles dominated the size distribution of total aerosol during the Asian dust period. It was found that SO4(2-), NH4+ and K+ were mainly distributed in fine particles, while Cl-, NO3-, Na+, Mg2+ and Ca2+ were in coarse particles. Although SO4(2-) was mainly distributed in fine particles, during the Asian dust period, the concentrations in coarse particles were significantly increased. This indicates heterogeneous oxidation of SO2 on wet surfaces of basic soil dust particles. The NH4+ was found to exist as (NH4)2SO4 in fine particles, with a molar ratio of NH4+ to SO4(2-) of 2.37 and 1.52 for non-Asian dust and Asian dust periods, respectively. Taking into account the proximity of the sampling site to the sea, and the observed chloride depletion, coarse mode nitrate, during the non-Asian dust period, is assumed to originate from the reaction of nitric acid with sodium chloride on the surfaces of sea-salt particles although the chloride depletion was not shown to be large enough to prove this assumption. During the Asian dust period, however, chloride depletion was much smaller, indicating coarse nitrate particles were mainly produced by the reaction of nitric acid with surfaces of basic soil particles. Most chloride and sodium components were shown to originate from sea-salt particles. Asian dust aerosols, arriving at Jeju Island, contained considerable amounts of sea-salt particles as they passed over the Yellow Sea. Ca2+ was shown to be the most abundant species in Asian dust particles.

Technological parameters of the ammonolysis of waste 1,2-dichloropropane

The ammonolysis of waste 1,2-dichloropropane (DCP) using liquid ammonia has been investigated. The influence of temperature, molar ratio of NH 3/1,2-dichloropropane and reaction time was examined. The highest yield of the synthesis was achieved at a temperature of 140 °C, for the reaction time of 3 h and the molar ratio of NH 3/1,2-dichloropropane as 20:1. Under these conditions the degree of 1,2-dichloropropane conversion amounted to 97.1 mol% and the selectivity of transformation to 1,2-diaminopropane (DAP) in relation to consumed 1,2-dichloropropane was 25.3 mol%, whereas in relation to consumed ammonia 17.9 mol%. The remaining 1,2-dichloropropane reacts to form polypropyleneamines.

Superhydrophobic silica aerogels based on methyltrimethoxysilane precursor

The experimental results on the synthesis and physicochemical properties of superhydrophobic silica aerogels, with the highest ever obtained contact angle (∼173°), using methyltrimethoxysilane (MTMS) precursor, methanol (MeOH) solvent and ammonium hydroxide (NH 4OH) catalyst, are reported. The molar ratios of NH 4OH/MTMS ( N), H 2O/MTMS ( H) and MeOH/MTMS ( M) were varied from 4.25 × 10 −2 to 3.5 × 10 −1, 2 to 10 and 1.75 to 17, respectively. It has been found that the gelation time decreases with increase in N and H values and it increases with increase in M values. The bulk density of the aerogels was found to decrease with increase in N, H and M values. It has been observed that the volume shrinkage increases with decrease in N and H values and increases with M values. In the case of catalyst concentration variation, the contact angle ( θ) increases slightly from 159° to 167° with increase in N values. On the other hand, in the case of H 2O and MeOH variations, the θ first increases from 162° and 160° up to the values of 173° and 167° and then decreases to 160° and 159° with increase in H and M values, respectively. All the MTMS aerogels are opaque to the visible light. The aerogels retain their hydrophobicity up to a temperature of ∼480 ° C. The thermal conductivity of the aerogels was found to be around 0.095 W/m K except for the aerogels with higher bulk density (>0.3 g/cm 3, at a lower H value of 2) whose thermal conductivity was around 0.109 W/m K. The aerogels have been characterized by Fourier transform infrared spectra (FTIR), thermogravimetric and differential thermal analyses (TGA-DTA) and scanning electron microscopy (SEM) techniques. The results have been discussed by taking into account the hydrolysis and condensation reactions and SEM observations.

Temporal Change in Ammonium/sulfate Ratios for Free Tropospheric Aerosols from Early Winter to Spring at a High Elevation Site in the Japanese Alps.

Samples of water-soluble ionic species in size-separated aerosol particles, acidic gases and ammonia were collected at Murododaira (2450 m a.s.l.) and Daikanbou (2320 m a.s.l.) near Mt. Tateyama, Japan, during the winter to spring season. The field observations consist of 2 to 14 days in November through April of 1995 to 2000. Median concentrations of the water-soluble ions in the aerosol particles and gases in the spring were about 2 to 8 times higher than those in the winter. The concentrations of NH+4, nssK+, C2O2-4 and nssF- in fine (<2. 1 μm) particles showed good correlations with nssSO2-4, suggesting that nssSO2-4 observed at Mt. Tateyama originated from anthropogenic sources. The molar ratios of NH+4 /nssSO2-4 for the fine particles at Mt. Tateyama changed from about 1 in the winter to about 2 in the spring, suggesting that atmospheric sulfate aerosols were present as ammonium bisulfate in the winter and as ammonium sulfate in the spring.

Nitrogen and phosphorus removal for swine wastewater using intermittent aeration batch reactor followed by ammonium crystallization process

A process for the crystallized precipitation of ammonium by adding magnesium salt and phosphate were carried out in order to remove nitrogen and phosphorus as well as to improve the C N ratio in swine wastewater. The optimal operation conditions were obtained as follows: reaction temperature (25°C), reaction time (1 h), pH (7.5) and the molar ratio of NH 4N:PO 4P:M g = 1.0:0.9:0.9. Under these conditions, the maximum quantity of the crystallized precipitation occurred, the removal ratio of NH 4N increased to more than 90% and the C N ratio increased from 1.98 to more than 8, but phosphorus was not removed. On the other hand, when the molar ratio of NH 4N:PO 4P:M g = 1.0:0.6:0.9, the ammonium and phosphorus removal ratio would be 79.32–87.45% and 40.3–88.5%, respectively. After completion of the crystallized precipitation of ammonium, an intermittent aeration process with an aeration to anaerobic time ratio of 1:1 h is used for this improved swine wastewater (T-N/BOD = 0.14, in which BOD = 8200 mg/l, T-N = 1166 mg/l, and NH 4N = 519 mg/l). The results obtained from these experiments showed that the removal ratio of T-N and NH 4N are 91 and 99%, respectively. T-P is not removed, while the removal ratio of PO 4P is 60% when 3% CaCl 2 liquid is added.

Relationships between Microstructure and Surface Acidity of Ti-Si Mixed Oxide Catalysts

The surface acidities and reactivities of titania, silica, and a series of Ti-Si mixed oxides have been investigated with a variety of surface-sensitive techniques, including temperature-programmed desorption/reaction of ammonia and 2-propanol, IR spectroscopy of adsorbed ammonia, and catalytic reaction of 1-butene. Results from TPD, TPR, and IR spectroscopy indicated that total acidity and relative acid strength decreased as silica was incorporated into titania. However, the areal rate of 1-butene isomerization was almost four times greater over a titania-rich mixed oxide than over pure titania. Infrared spectroscopy of adsorbed ammonia revealed that all of the acid sites on pure titania were of the Lewis type, whereas about 80% of the sites on the mixed oxides were of the Bronsted type. Therefore, the enhancement of butene isomerization activity over titania-rich mixed oxides was attributed to the Bronsted acid sites that were not present on pure titania. The appearance of Bronsted acidity in titania-rich mixed oxides was due to the local charge imbalance associated with tetrahedrally coordinated silica chemically mixing with the octahedral titania matrix. In silica-rich mixed oxides, Ti substituted isomorphously for Si in the tetrahedral silica matrix, thus eliminating the local charge imbalance that caused Bronsted acidity. The molar ratio of NH 3(ads) /Ti for a silica-rich mixed oxide was approximately 0.3, which was nearly the same as the fraction of nontetrahedrally coordinated Ti in the sample.

Cultures ofGinkgo biloba, effect of nutritional and hormonal factors on the growth of cultured cells derived fromGinkgo biloba

Calli and suspension cultures were obtained following inoculation of the explant from leaves ofGinkgo biloba L. on the supplemented MS basal medium. The obtained calli and suspension cultured cells were able to produce detectable amounts of ginkgolides which are known as natural specific PAF antagonists. The production of ginkgolides in the calli and suspension cultured cells were identified using GC/MS, GC and HPLC with authentic compounds. Since the production of ginkglides A and B in the calli and suspension cultured cells had been confirmed, effects of types and concentration of plant growth regulators, media and illumination on the induction and growth of the callus were studied. The concentrations of growth regulators for optimal callus induction were 1.0 to 2.0 mg/L for NAA and 0.1 mg/L for kinetin. The growth of the callus seemed to be more stimulated with the combination of NAA and kinetin than NAA and BA with illumination at all concentration ranges of 1.0 to 4.0 mg/L for NAA and 0.1 to 1.0 mg/L for kinetin or BA studied. Among 8 different media used, the induction rate of callus on Anderson, Eriksson, and Schenk and Hildebrant at 4 weeks after the innoculation was almost the same as that of MS. However, callus was rarely induced on Heller or White medium. Suspension cultures were easily initiated with 3 g of callus (fresh weight) derived from ginkgo leaves on supplemented MS medium. A typical growth curve of suspension cultured cells could be obtained by measuring the fresh weight of the suspension cultured cells at every 3 days. To improve the growth of suspension cultured cells of ginkgo, effects of concentrations of NAA, sucrose, phosphate ions and molar ratio of NH4+ to NO3− ions in the culture medium were studied. The maximum growth of the cells was achieved when the culture medium contained 1.0 mg/L of NAA, 30 g/L sucrose, 1.75 mM phosphate ions and 1∶5 molar ratio of NH4+ to NO3− ions.

Low temperature growth of GaN single crystal films using electron cyclotron resonance plasma excited metalorganic vapor phase epitaxy

A novel low-temperature-growth technique for GaN single crystal films has been developed utilizing electron cyclotron resonance (ECR) plasma excitation. The GaN film is grown in a low pressure metalorganic vapor phase epitaxy (MOVPE) system employing the reaction of trimethylgallium (TMG) with highly activated nitrogen produced by ECR excitation of ammonia. Using this ECR excitation technique, GaN single crystal films are grown on a sapphire basal plane at low substrate temperatures from 300 to 400° C under a molar ratio of NH 3 to TMG of 100 and a growth pressure of 2 × 10 −4 Torr. Furthermore, Zn-doped GaN single crystal films are successfully grown by adding dimethylzinc. The surface morphology of the GaN film is very smooth and the electrical properties of the undoped film are comparable to those with a MOVPE technique at high growth temperatures. Photoluminescence experiments at room temperature reveal that a blue luminescence peak appears in Zn-doped GaN and that the peak shifts to longer wavelengths with increases in the Zn-doping level.