Continuous Ammonia Research Articles

Nitrification characteristics of nitrobacteria immobilized in waterborne Polyurethane in wastewater of corn-based ethanol fuel production

A technology to achieve stable and high ammonia nitrogen removal rates for corn distillery wastewater (ethanol fuel production) treatment has been designed. The characteristics of nitrifying bacteria entrapped in a waterborne polyurethane (WPU) gel carrier were evaluated after acclimation. In the acclimation period, nitrification rates of WPU-immobilized nitrobacteria were monitored and polymerase chain reaction (PCR) was also carried out to investigate the change in ammonium-oxidizing bacteria. The results showed that the pellet nitrification rates increased from 21 to 228 mg-N/(L-pellet·hr) and the quantity of the ammonia oxidation bacteria increased substantially during the acclimation. A continuous ammonia removal experiment with the anaerobic pond effluent of a distillery wastewater system was conducted with immobilized nitrifying bacteria for 30 days using an 80 L airlift reactor with pellets at a fill ratio of 15% (V/V). Under the conditions of 75 mg/L influent ammonia, hydraulic retention time (HRT) of 3.7–5.6 hr, and dissolved oxygen (DO) of 4 mg/L, the effluent ammonia concentration was lower than 10 mg/L and the ammonia removal efficiency was 90%. While the highest ammonia removal rate, 162 mg-N/(L-pellet·hr), was observed when the HRT was 1.3 hr.

Sensitive Gas Analysis System on a Microchip and Application for On-Site Monitoring of NH3 in a Clean Room

A portable, highly sensitive, and continuous ammonia gas monitoring system was developed with a microfluidic chip. The system consists of a main unit, a gas pumping unit, and a computer which serves as an operation console. The size of the system is 45 cm width × 30 cm depth × 30 cm height, and the portable system was realized. A highly efficient and stable extraction method was developed by utilizing an annular gas/liquid laminar flow. In addition, a stable gas/liquid separation method with a PTFE membrane was developed by arranging a fluidic network in three dimensions to achieve almost zero dead volume at the gas/liquid extraction part. The extraction rate was almost 100% with a liquid flow rate of 3.5 μL/min and a gas flow rate of 100 mL/min (contact time of ~15 ms), and the concentration factor was 200 times by calculating the NH(3) concentration (w/w unit) in the gas and liquid phases. Stable phase separation and detection was sustained for more than 3 weeks in an automated operation, which was sufficient for the monitoring application. The lower limit of detection calculated based on a signal-to-noise ratio of 3 was 84 ppt, which showed good detectability for NH(3) analysis. We believe that our system is a very powerful tool for gas analysis due to the advantages of portable size, high sensitivity, and continuous monitoring, and it is particularly useful in the semiconductor field.

Effect of pH, temperature and air flow rate on the continuous ammonia stripping of the anaerobic digestion effluent

A stable continuous stripping of ammonia from the anaerobic wastewater treatment plant effluent was obtained in the ammonia stripping bench plant. The effects of temperature, amount of air and pH level on the removal of ammonium from the effluent were examined in the experiments. The operating parameters in the trials were chosen in respect of the economically feasible operating conditions in a biogas plant. The results of ammonium removal were compared with theoretically calculated values of free ammonia in these conditions. Ammonia stripping bench plant continuously removed up to 92.8% of ammonium and 88.3% of total nitrogen from the anaerobic digestion effluent. High pH had the most significant effect on stripping, causing the change of the ammonia/ammonium ratio in favour of ammonia. The second important factor was the amount of air passing through the stripping bench plant promoting the transition of ammonia from the liquid phase to the gas phase. The temperature within the examined range had the least significant effect on ammonia stripping. Continuous stripping of nitrogen from the anaerobic digestion effluent could considerably reduce the area required for the application of nitrogen-rich digestate after the biogas production and enable the treatment of the anaerobically digested effluent in the wastewater treatment plant.

An annular denuder system for the collection of elevated quantities of ammonia to allow for the measurement of inorganic reactive gases and aerosol species inside poultry houses

The annular denuder system (ADS) is an instrument for trapping and subsequently analysing for concentrations of inorganic reactive gases and aerosol species in the atmosphere. Todate its application in the livestock industry is limited primarily by its inability to collect gaseous ammonia at the elevated levels commonly observed in livestock operations. The study’s objective was to improve upon the ammonia collection capabilities of the ADS to determine if it was potentially suitable for in-house sampling. Using a 1% phosphorous acid coating, a single denuder becomes less than 100% efficient at collecting gaseous ammonia after 0.65 mg of ammonia was absorbed on the denuder’s walls. The loading capacity of the denuder was determined to be 2.39 ± 0.23 mg of ammonia. Ammonia saturation problems were alleviated by using seven denuders in series to collect a representative ammonia level (25 ppm) for poultry facilities over an hour sampling period. The extended ADS was calibrated against three ammonia gas standards and an ammonia monitor. The mean error was determined to be 2.39% using the ammonia standards and it was within 5.1%, on average, of the ammonia measurements using the continuous ammonia monitor inside a layer facility.

Continuous gaseous and total ammonia measurements from the southeastern aerosol research and characterization (SEARCH) study

Continuous ammonia (NH 3) measurements with a temporal resolution of 5 min were implemented at selected SEARCH sites in the southeastern U. S. during 2007. The SEARCH continuous NH 3 instrument uses a citric acid denuder difference technique employing a dual-channel nitric oxide-ozone chemiluminescence analyzer. Data from two SEARCH sites are presented, Jefferson Street, Atlanta (JST) (urban), and Yorkville, Georgia (YRK) (rural), for the period July–December, 2007. Highest NH x (total ammonia = gaseous NH 3 + PM 2.5 NH 4 +) values were observed in August and September at both JST and YRK. Highest NH 3 values occurred in August and September at JST, but in August through October at YRK. Lowest NH 3 and NH x values occurred in December at both sites. YRK is significantly impacted by nearby poultry sources, routinely experiencing hourly average NH 3 mixing ratios above 20 ppbv. Wind sector analysis clearly implicates the nearby poultry operations as the source of the high NH 3 values. Weekday versus weekend differences in composite hourly mean diurnal profiles of NH 3 at JST indicate that mobile sources have a measurable but relatively small impact on NH 3 observed at that site, and little or no impact on NH 3 observed at YRK. A distinctive composite mean hourly diurnal variation was observed at both JST and YRK, exhibiting maxima in the morning and evening with a broad minimum during midday. Analysis of observed NH 3 diurnal variations from the literature suggests a hypothesized mechanism for the observed behavior based on interaction of local emissions and dry deposition with the formation and collapse of the dynamically mixed atmospheric boundary layer during the day and shallow nocturnal layer at night. Simple mixed layer concentration box model simulations confirm the plausibility of the suggested mechanism.

Continuous Ammonia Emission Measurements from a Commercial Beef Feedyard in Texas

Ammonia emissions from cattle feedlots pose the potential to react with other compounds such as oxides of nitrogen and sulfur, which lead to detrimental environmental effects. Ambient ammonia (NH3) concentrations were measured continuously at a beef cattle feedyard for 12 months beginning in March 2007. Concentrations were measured every 5 min, 24 hours per day, at a sample intake height of 3.3 m using a chemiluminescence analyzer. On-site weather data were collected concurrently. Modeled emissions of NH3 were compared with the mass balance of N for the feedyard. Mean annual NH3 concentrations were 0.57 ppm, with a monthly average low of 0.37 ppm in December 2007 and a monthly average high of 0.77 ppm in August 2007. Flux densities were calculated using a backward Lagrangian stochastic model (WindTrax 2.0.7.8). Mean annual flux density was 70.7 g m-2 s-1 (2.2 kg m-2 year-1). Mean monthly flux density ranged from 42.7 to 123.1 g m-2 s-1 (0.11 to 0.32 kg m-2 month-1) in November and April 2007, respectively. Both concentration and flux density had a diel distribution with minima during the nighttime hours and maxima during the early afternoon. On an annual basis, 48.8% of fed N was volatilized as NH3. The inverse modeled daily ammonia production per head was 85.3 g NH3-N (head fed)-1 d-1.

Optimisation and validation of the intermittent measurement method to determine ammonia emissions from livestock buildings

In previous studies, a method to reduce the high cost of continuous ammonia emission measurements by using the expensive equipment in several buildings for short periods was developed. Further optimisation and validation of the method of “intermittent measurements” to estimate the ammonia yearly emission from pig houses, based on a limited number of measuring days, are described. The method is tested and improved with new data from three different pig houses. The method of “intermittent measurements” models the relationship between ammonia emission and easily measurable variables such as in- and outdoor temperatures, ventilation rate and weight of the animals. The parameters of the emission model are determined for an individual farm in a time variant manner. They are based on frequent ammonia measurements in combination with the easily measured variables from a limited number of days over a certain time interval. For all other days throughout the year, the emission of ammonia is not measured, but, by using the model, it is calculated from the easily measured variables. In previous studies, the parameters in the emission model for a specific building were calculated only once a year with the data of all selected measuring days throughout the year. In this study, the ammonia emission was modelled in a more precise, stepwise manner such that model parameters were calculated over shorter time periods, such as 70 days. This resulted in an optimised procedure in which, for fattening pigs, each fattening period was modelled in two parts: the first part from day 1 to day 70 and the second part from day 70 to the end of the fattening period. The adapted method was tested on data from seven fattening periods originating from three different pig houses. The accuracy of the method was obtained by evaluating the difference between the ammonia emission calculated from the model with the measured total ammonia emission, sampled every 12 min over a whole fattening period. With 4 measuring days per fattening period, a maximum model error of less than 10% was achieved for all datasets; while previous method with fixed model parameters throughout the year on the new validation datasets resulted sometimes in errors above 25%.

Ammonia fluxes in relation to cutting and fertilization of an intensively managed grassland derived from an inter-comparison of gradient measurements

Abstract. Quantification of ammonia (NH3) land-atmosphere exchange is required for atmospheric modelling and assessment of nitrogen deposition, yet flux measurement methods remain highly uncertain. To address this issue, a major inter-comparison of ammonia fluxes over intensively managed grassland was conducted during the GRAMINAE Integrated Experiment held in Braunschweig, Germany. In order to provide a robust dataset of ammonia exchange with the vegetation, four independent continuous flux gradient systems were operated. Three independently operated continuous wet denuders systems (AMANDA) were compared with a Wet Effluent Diffusion Denuder (mini-WEDD) system. Measurements were made at two distances from an adjacent livestock farm, allowing effects of advection to be quantified in a real landscape setting. Data treatment included filtering for instrument failure, disturbed wind sectors and unsuitable micrometeorological conditions, with corrections made for storage and advection errors. The inter-comparison demonstrated good agreement in measured ammonia concentrations and fluxes (relative standard error <20%) for some periods, although the performance of the ammonia analyzers were variable, with much poorer agreement on particular days. However, by using four systems, the inter-comparison was able to provide a robust mean estimate of continuous ammonia fluxes through the experiment. The observed fluxes were: a) small bi-directional fluxes prior to cutting (−64 to 42 ng NH3 m−2 s−1), b) larger diurnally-varying emissions following cutting (−49 to 703 ng NH3 m−2 s−1) and c) much larger emissions following fertilizer application (0 to 3820 ng NH3 m−2 s−1). The results are a salutary reminder of the uncertainty in unreplicated ammonia flux measurements, while the replication of the present study provides a uniquely robust dataset for the evaluation of ammonia exchange processes. It is clear that consistently reliable determination of ammonia concentrations remains the major measurement challenge.

Baseline ambient gaseous ammonia concentrations in the Four Corners area and eastern Oklahoma, USA

Ambient ammonia monitoring using Ogawa passive samplers was conducted in the Four Corners area and eastern Oklahoma, USA during 2007. The resulting data will be useful in the multipollutant management of ozone, nitrogen oxides, and visibility (atmospheric regional haze) in the Four Corners area, an area with growing oil/gas production and increasing coal-based power plant construction. The passive monitoring data also add new ambient ammonia concentration information for the U.S. and will be useful to scientists involved in present and future visibility modeling exercises. Three week integrated passive ammonia samples were taken at five sites in the Four Corners area and two sites in eastern Oklahoma from December, 2006 through December, 2007 (January, 2008 for two sites). Results show significantly higher regional background ammonia concentrations in eastern Oklahoma (1.8 parts per billion (ppb) arithmetic mean) compared to the Four Corners area (0.2 ppb arithmetic mean). Annual mean ammonia concentrations for all Four Corners area sites for the 2007 study ranged from 0.2 ppb to 1.5 ppb. Peak ambient ammonia concentrations occurred in the spring and summer in both areas. The passive samplers deployed at the Stilwell, Oklahoma site compared favorably with other passive samplers and a continuous ammonia monitoring instrument.

Growth and Foliar Nitrogen Status of Four Plant Species Exposed to Atmospheric Ammonia

A chamber study was conducted to evaluate the growth response and leaf nitrogen (N) status of four plant species exposed to continuous ammonia (NH3) for 12 weeks (wk). This was intended to evaluate appropriate plant species that could be used to trap discharged NH3 from the exhaust fans in poultry feeding operations before moving off-site. Two hundred and forty bare-root plants of four species (Juniperus virginiana (red cedar), Gleditsia triacanthos var. inermis (thornless honey locust), Populus sp. (hybrid poplar), and Phalaris arundinacea (reed canary grass) were transplanted into 4- or 8-L polyethylene pots and grown in four environmentally controlled chambers. Plants placed in two of the four chambers received continuous exposure to anhydrous NH3 at 4 to 5 ppm while plants in another two chambers received no NH3. In each of the four chambers, 2 to 4 plants per species received no fertilizer while the rest of the plants were fertilized with a 100 ppm solution containing 21% N, 7% phosphorus, and 7% potassium. The results showed that honey locust was the fastest-growing species. The superior growth of honey locust among all species was also supported by its total biomass, root, and root dry matter (DM) weights. For all species there was a trend for plants exposed to NH3 to have greater leaf DM than their non-exposed counterparts at 6 (43.0 vs. 30.8%; P = 0.09) and 12 wk (47.9 vs. 36.6%; P = 0.07), and significantly greater (P ≤ 0.05) leaf N content at 6 (6.44 vs. 3.67%) and 12 wk (7.05 vs. 3.51%) when exposed to NH3. Numerically greater leaf DM due to NH3 exposure was also consistently measured in poplar at both sampling periods. Hybrid poplar, as well as honey locust and reed canary grass, deposited 1.5 to 2-fold greater N in their leaves than red cedar tissues as a result of NH3 exposure compared to non-exposed plants. Regardless of the effect of NH3 on foliar color and damage score of the plants, the increase of foliar N content (g 100 g−1 of fresh foliage weight) after NH3 exposure at 6 and 12 wk was 0.45 and 0.87 for grass,1.25 and 1.34 for locust, and 2.67 and 6.09 for poplar. However, only honey locust likely benefited from ambient NH3 as indicated by its consistent leaf color quality and lower damage score, compared with other species that were adversely affected by atmospheric NH3.

Water quality guidance for protection of freshwater mussels (Unionidae) from ammonia exposure.

Ammonia toxicity data for freshwater mussels (Unionidae), a significantly imperiled taxa, were used to derive estimates of concentrations that would not likely be harmful in acute and chronic exposures and to assess the protectiveness of current U.S. Environmental Protection Agency (U.S. EPA) water quality criteria to this family of organisms. Thirty acute (24-96-h) median lethal concentrations (LC50s), covering 10 species in eight unionid genera, were used to calculate genus mean acute values (GMAVs) ranging from 2.56 to 8.97 mg/L total ammonia as N at pH 8. Freshwater mussels are at the sensitive end of the range when added to the GMAVs from the database used to derive the U.S. EPA criteria maximum concentration (CMC). We derived two estimates of acute exposure water quality guidance for the protection of freshwater mussels (CMC(FM)) by a recalculation of the CMC after adding freshwater mussel GMAVs to the U.S. EPA data set. The CMC(FM)s of 1.75 and 2.50 mg/L total ammonia as N at pH 8 average 60% less than the U.S. EPA CMC of 5.62 mg/L total ammonia as N at pH 8 for application when salmonids are present. These values average about 75% less than the CMC for application when salmonids are absent. No chronic ammonia exposure data existed for unionids. Thus, we applied a range of estimated acute:chronic ratios to the acute toxicity data set, expanded with the freshwater mussel GMAVs. to estimate continuous ammonia concentrations that may be protective of freshwater mussels. These estimates ranged from 0.3 to 1.0 mg/L total ammonia as N at pH 8, about 20 to 75% less than the U.S. EPA criteria continuous concentration (CCC) of 1.24 mg/L total ammonia as N at pH 8 and 25 degrees C. The current numeric criteria for ammonia may not be protective of mussels, more than half of whose nearly 300 species are in decline in North America. While the CMC(FM) and CCC(FM) are not equivalent to revised U.S. EPA criteria, they are offered as interim guidance for the protection of freshwater mussels.

Upgrading of Borås wastewater treatment plant based on intelligent process and operation control

Borås wastewater treatment plant is being upgraded to comply with the new effluent standards for nitrogen. Three different configurations have been tested in parallel in full scale in the existing activated sludge plant. The Biodenitro operated line showed the best performance because of the flexible adjustment of the nitrification and denitrification capacity. The adjustment was made off-line with the aid of continuous ammonia and nitrate measurements. On-line sensors are now installed permanently at Borås wastewater treatment plant and will be used for on-line dynamic control of the nitrogen removal in a Biodenitro configuration. The plant capacity will be further increased by settling in the aeration tanks in situations with high hydraulic load.

Upgrading of bors wastewater treatment plant based on intelligent process and operation control

Boras wastewater treatment plant is being upgraded to comply with the new effluent standards for nitrogen. Three different configurations have been tested in parallel in full scale in the existing activated sludge plant. The Biodenitro operated line showed the best performance because of the flexible adjustment of the nitrification and denitrification capacity. The adjustment was made off-line with the aid of continuous ammonia and nitrate measurements. On-line sensors are now installed permanently at Boras wastewater treatment plant and will be used for on-line dynamic control of the nitrogen removal in a Biodenitro configuration. The plant capacity will be further increased by settling in the aeration tanks in situations with high hydraulic load.

Batch cultures of a hybridoma cell line performed with in situ ammonia removal

Batch cultures of a mouse/mouse hybridoma cell line secreting a dimeric IgA were performed in combination with a membrane process for the continuous removal of ammonia from the culture medium. The latter involves hydrophobic porous membranes with an associated pH gradient. The process was shown to be efficient reducing the ammonia concentration by approximately 50% by comparison to control experiments. Two series of experiments were performed with an initial glutamine concentration of 4 m m and 10 m m, respectively. The growth characteristics, antibody productivity, and quality of antibody assayed by Western blotting were not changed by ammonia removal; however, the cellular energy metabolism was affected by reduction of ammonia levels. At the lower initial glutamine concentration, ammonia removal caused an increased glutamine consumption and reduced lactate production. No effect upon glucose uptake was observed, thus resulting in a considerably reduced yield of lactate from glucose. At the high initial glutamine concentration, the reduced ammonia concentration led to a decrease in glucose and glutamine consumption as well as lactate production. This resulted in only a slight increase in the yield of lactate from glucose. Despite the abundance of literature concerning ammonia inhibition of mammalian cell cultures, little has been reported concerning the effect of continuous ammonia removal from such cultures.

Ammonia-induced brain edema and intracranial hypertension in rats after portacaval anastomosis

Brain edema, leading to intracranial hypertension and brain herniation, is a major cause of death in fulminant liver failure. Astrocyte swelling is a prominent neuropathological feature in experimental fulminant liver failure. It has been postulated that the osmotic effects of glutamine, generated in astrocytes from ammonia and glutamate in a reaction catalyzed by glutamine synthetase, could mediate brain swelling. Normal rats and rats that received a portacaval anastomosis were infused with ammonium acetate or a sodium acetate control; brain water in cerebral cortex was measured with the gravimetry method, intracranial pressure by means of a cisterna magna catheter and cortical amino acids using high-performance liquid chromatography. Although brain edema was detected in both groups receiving ammonia, it was of a greater magnitude in portacaval anastomosis rats (80.94% + 0.17% vs. 80.24% + 0.09%, p < 0.01), resulting in the development of intracranial hypertension. When portacaval anastomosis rats were infused with ammonium acetate and pretreated with 150 mg/kg methionine-sulfoximine, an inhibitor of glutamine synthetase activity, brain edema was ameliorated and intracranial pressure did not rise. A dose-dependent reduction in brain glutamine levels was seen with increasing doses of methionine-sulfoximine; however, brain edema did not decrease beyond the 150 mg/kg dose, suggesting that the increase in brain water was not solely a result of glutamine accumulation. We conclude that brain edema of a magnitude that results in intracranial hypertension is more likely to develop in rats after portacaval anastomosis receiving a continuous ammonia infusion. The osmotic effects of glutamine appear to mediate, but only in part, the increase in brain water seen in this preparation.(ABSTRACT TRUNCATED AT 250 WORDS)

Does exercise affect large gut function?

The effect of exercise on large intestinal function has been determined in 14 healthy but normally sedentary men and women, aged 22–34 years while on a constant diet. For an initial 3–5 week period (control) no activity was allowed. Six subjects then undertook a 9 week training schedule by the end of which they were capable of jogging for 1 h/day, 5 days a week. A further six subjects undertook a similar training schedule that lasted for only 7 weeks, at the end of which they were jogging for 45 min/day. Finally, two subjects were studied continuously while taking light exercise for 6 weeks and then jogging for a further 3 weeks. Physical fitness was monitored and showed significant changes with maximum aerobic capacity increasing from 2.4+0.5 to 3.1+0.4 l/min, maximum heart rate after a step test falling from 1524–8 to 129+5 beats/min, and resting pulse rate also falling from 56+4 to 50+5 beats/min. High-density lipoprotein cholesterol also increased significantly. Colonic function was assessed by measurement of stool weight and transit time, using the continuous radio-opaque marker technique, faecal pH, nitrogen excretion, and ammonia concentration. No change was observed overall in mean daily faecal weight (124 + 39 (control) and 129+49 g/day (exercise), transit time (55+20 (control) and 54+23 h (exercise)), nor in faecal frequency, dry stool weight, pH, ammonia, or in total nitrogen excretion. Significant changes did occur in five individuals with significant slowing of transit time in two and speeding up in three. Overall transit time increased in nine subjects and decreased in five. Hence, when diet is constant, exercise has marked effects on physical fitness but no consistent effect on large bowel function.

Anaerobic metabolism of goldfish,Carassius auratus (L.). Influence of anoxia on mass-action ratios of transaminase reactions and levels of ammonia and succinate

Changes in the concentrations of ammonia, glutamate, alanine, aspartate, α-ketoglutarate, oxaloacetate and succinate were measured in freeze-clamped lateralred muscle, dorsal white muscle and liver, and in rapidly cooled blood of goldfish after 12 h of anoxia. Alanine accumulation, succinate accumulation and aspartate depletion are observed in all tissues examined; in the liver the concentrations of glutamate increase and those of ammonia decrease. The mass-action ratio of the glutamate-pyruvate transaminase-catalyzed reaction stays within one order of magnitude from thermodynamic equilibrium in the direction of alanine formation. The mass-action ratio of the glutamate-oxaloacetate transaminase reaction is far from equilibrium when measured oxaloacetate concentrations are used. When levels of free oxaloacetate are calculated from LDH and MDH equilibrium constants, the mass-action ratio of glutamate-oxaloacetate transamination is close to equilibrium in the direction of aspartate formation. Since neither alanine nor glutamate decreases, and since ammonia gradients suggest a continuous ammonia production in all tissues examined, anaerobic proteolysis is assumed. A possible coupling between amino acid catabolism and ethanol production is discussed.

Carbon dioxide, ammonia and the origin of life

Stellar evolution theory predicts that the luminosity of the Sun has increased by ∼30% over the past 4,000 Myr. Yet geological and biological evidence indicates that the climate of the Earth between 3,000 and 4,000 Myr ago was as warm as, or warmer than, today. This apparent contradiction, the ‘faint Sun paradox’, has been resolved by invoking the greenhouse effect of radiatively active gases in the early Earth atmosphere. Sagan and Mullen1 first suggested that the concentration of ammonia in the early atmosphere was around 10–100 p.p.m., sufficiently high to counteract the reduced luminosity. However, because ammonia photodissociates readily and has a short atmospheric residence time2,3, such a concentration could be maintained only by a large continuous ammonia source. For this reason, carbon dioxide is now considered to have been the radiatively active gas4–7. Some atmospheric ammonia is, nevertheless, required to provide conditions conducive to the origin of life8. We now show that, if the early Earth's atmosphere contained high concentrations of CO2, as suggested above, then the chemical conditions required for life to begin can be maintained by very low ammonia partial pressures, rather similar to those observed today.

Continuous ammonia monitor using a Stark microwave cavity resonator

An ammonia monitor has been made by using a rectangular Stark microwave cavity tightly coupled through an iris to a Gunn oscillator. The Stark electrode installed inside the cavity is provided with a 100 kHz sinusoidal modulation voltage and a dc sweep voltage. The oscillation of the Gunn diode is tuned with the coupled Stark cavity to a frequency near a J,K=3,3 transition (23870.1 MHz) of ammonia. By fixing the Stark dc bias to a voltage which gives a peak intensity of the derivative output of the electric-resonance signal, ammonia is continuously monitored. An extremely good long-term stability is obtained. The noise level corresponds to 0.08 ppm of ammonia.

Description and Detailed Discussions of a Continuous Ammonia Monitor Using a Stark Microwave Cavity

Description and Detailed Discussions of a Continuous Ammonia Monitor Using a Stark Microwave Cavity