Measured Ammonia Concentrations Research Articles

Improved Passive Flux Samplers for Measuring Ammonia Emissions from Animal Houses, Part 1: Basic Principles

At present, precise, expensive and laborious methods with a high resolution in time are needed, to determine ammonia emission rates from animal houses. The high costs for equipment, maintenance and labour limit the number of sites that can be measured. This study examines a new, simpler concept for carrying out these measurements. The basis of the concept is a passive ammonia flux sampler, which improves on Ferm's original design by having a central orifice (thus halving the number of tubes per sampler and hence halving the number of analyses needed) and also by having a greatly increased ammonia-capturing capacity. Sets of the samplers can be placed in ventilation ducts, or in openings of a naturally ventilated animal house, to give a direct and simple measure of ammonia flux and hence of overall ammonia emission rate. Calibration of any sampler design based on this new concept is quick and easy: this is important because of the huge variation in designs of systems for ventilation in animal houses. Moreover, no power source is needed to perform cheap and accurate time-integrated ammonia emission measurements. The high ammonia-capturing capacity, allowing a long-term exposure, of at least 1 week, is achieved by using a glass-fibre insert to hold a large charge of a mineral acid. First results from validation tests with the simplest possible sampler design on the farm were promising. The flux samplers proved easy to handle and deploy, and gave results which agreed closely with those from a reference method based on fan-wheel anemometers to give ventilation rate and on the continuous measurement of ammonia concentration by chemiluminescence. In a companion paper, the performance of different forms of the flux sampler as a function of angle of incidence of airflow is reported.

Lidar Measurement of Ammonia Concentrations and Fluxes in a Plume from a Point Source

A field experiment was performed that demonstrated the ability of a scanning carbon dioxide (CO2) coherent lidar system to measure the concentration distribution of ammonia in a plume from a point source. This application of the differential absorption lidar (DIAL) method used wavelengths of CO2 lasers at 10.288 μm (online) and 10.274 μm (offline). The addition of wind information, which was obtained from Doppler measurements with the same lidar, permitted ammonia flux measurements through a vertical plane. The measurements were performed in the early morning when the atmosphere was stable, cool, and dry. Ammonia fluxes calculated from the lidar data showed satisfactory agreement with the ammonia release rates measured by a flowmeter. Modifications are planned to improve sensitivity and to enable measurement of ambient ammonia concentrations in polluted regions.

Measurement of atmospheric ammonia at a dairy using differential optical absorption spectroscopy in the mid-ultraviolet

Ammonia is the most abundant basic gas in the atmosphere, and after N 2 and N 2O is the most abundant nitrogen-containing specie (Seinfeld and Pandis, 1998. Atmospheric Chemistry and Physics: from air pollution to climate changes. Wiley, New York). Typical concentrations of ammonia in the boundary layer range from <1 part per billion by volume (ppbv) in the free continental troposphere to parts per million (ppmv) levels over animal waste lagoons and near animal stalls. Agricultural activities are the dominant global source of ammonia emissions and a major environmental concern. In the US, ≈85% of ammonia emissions come from livestock operations (EPA Trends, 1998. www.epa.gov/ttn/chief/trends98/chapter2.pdf). Dairy farms constitute a large fraction of the livestock inventory. Current estimates of ammonia emissions to the atmosphere are characterized by a high degree of uncertainty, and so it is very important to obtain better estimates of ammonia emissions. We are working at the Washington State University research dairy to quantify ammonia emissions and investigate the effects of various mitigation strategies on those emissions. We describe here a new instrument utilizing the differential optical absorption spectroscopy (DOAS) technique to measure ammonia in the mid-ultraviolet with a detectability limit of about 1 ppb. DOAS avoids many of the problems that have thwarted past ammonia concentration measurements. Initial results show concentrations in the barn/concrete yard areas in the tens of parts per million range, over the slurry lagoons of hundreds of parts per billion to low parts per million, and low parts per million levels after initial slurry applications onto pastureland. Future papers will report on emission fluxes from the various parts of the dairy and the results of mitigation strategies; we show here initial data results. For a recent review of ammonia volatilization from dairy farms, see Bussink and Oenema (Nutrient Cycling in Agroecosystems 51(1998) 19).

SOME POTENTIAL PROBLEMS FOR MEASURING AMMONIA EMISSIONS FROM FARM STRUCTURES

The ability to accurately measure ammonia emissions from farm buildings is an important issue both forestablishing emissions regulations and for effective evaluation of mitigation techniques. Most techniques for measuringemissions rely on subsampling within a space. This study examines the influence of subsampling under a variety ofconditions on estimated ammonia recoveries. Tests were made using a large environmental chamber with controlled releasesof ammonia from a gas cylinder from one of two positions within the chamber. Ammonia concentrations were measured incontinuous air samples from either a single exhaust duct or a sampling port in the exhaust plenum where exhaust gases werewell mixed. The chamber temperature was maintained at 22.2. C with an airflow of 10.5 air exchanges per hour. Formeasurements made in the exhaust duct, ammonia recoveries were 217% when the release position and the sampling ductwere aligned in terms of chamber airflow, and were 52% when the positions were not aligned. Placing a wooden barrierbetween aligned release and measurement positions only reduced ammonia recoveries to 173%. In contrast, using anoscillating fan to disperse the ammonia release reduced ammonia recoveries to 78%. When measurements were made in theplenum, recoveries were essentially 100%, and placement of a continuously wetted barrier between the release position andthe exhaust ducts did not influence recoveries. It is suggested that measurement of ammonia emissions be restricted to farmstructures with welldefined airflows and a limited number of exhaust openings, and that the most accurate method forestimating ammonia emission rates would be to collect and mix all of the exhaust streams from a structure prior tocontinuously measuring ammonia concentration and airflow.

Measuring ammonia concentration over a grassland near livestock facilities using a semiconductor ammonia sensor

We demonstrated the effectiveness of a semiconductor ammonia sensor capable of performing diachronic measurements; its characteristics were checked in the laboratory by means including comparison with standard gases. We found as a result that the ammonia sensor's readings increased with increasing water vapor pressure. We compared sensor readings with values obtained by chemical analysis of samples collected in situ and checked sensor reading accuracy. Ammonia concentration was determined by combining ammonia sensor readings with measured values for water vapor pressure. In situ conditions were ammonia concentration of under 100 ppbv and water vapor pressure of 4–16 hPa. There was a good correlation with the concentration of samples trapped with boric acid and analyzed by indophenol colorimetry. We discerned a relationship between ammonia concentration and local meteorological conditions such as wind direction and speed. The estimated error of the ammonia sensor's measurements was ±9.7 ppbv when ammonia concentration as measured by acid sampling and colorimetry was regarded as correct. This demonstrated that it is possible to detect in situ fluctuations in low ammonia concentrations of about 10 ppbv, which was the background concentration in farming areas. We have shown a monitoring method for ammonia in situ that is both easy to operate and low-cost.

Automated indirect method of ammonia flux measurement for agriculture: effect of incident wind angle on airflow measurements

Cost effective, distributed instrumentation arrays have to be developed to realise a robust automated ammonia flux measurement system suitable for use at the periphery of naturally ventilated livestock buildings. The new system is designed to permit the calculation of ammonia flux indirectly from measurements of ammonia concentration, using conducting polymer sensors, and wind speed with direction, via a commercially available airflow sensor. This paper discusses the problems associated with calculating external wind speed from measurement of airflow rates within a fixed sampler tube. It is necessary to be able to compensate for anomalous flow regimes within the sampler system, which can arise from changes to the external wind direction. Wind conditions, across the site of interest, should be faithfully recorded throughout the experiment, otherwise models based upon the acquired data may be unrealistic.

Measurement of ammonia concentrations in horse stalls

The effect of treating stall floors with an ammonia-absorbingcompound (AAC) on aerial ammonia levels was tested during two 14-day periods in a four-stall barn. In the first period, two stalls were treated with the AAC and the other two stalls remained as the non-treated controls. In the second period, the stalls were switched. Four geldings were used in each period and were randomly assigned to the stalls. The horses remained in the stalls at all times except for 30 min of turn-out per day at which time the stalls were cleaned. Ammonia levels at the stall floor were measured by a Bruel and Kjacr 1302 gas monitor on day 0 before the horses were admitted to the barn and on days 1, 3, 5, 7, 10 and 14. Ammonia diffusion tubes were attached to the horses' halters on days 1, 7, 11 and 13 for 8 hours to determine the level of ammonia exposed to the horse. On day 14, ammonia concentrations near the stall floor were 25% lower in treated stalls than in control stalls (P<0.1). Ammonia concentrations measured at the halter were much lower than those at the floor, but horses in treated stalls had lower ammonia exposure than horses in control stalls (P<0.1).

Measurements of ammonia concentrations, fluxes and dry deposition velocities to a spruce forest 1991–1995

The dry deposition velocities and fluxes of ammonia have been estimated from measurements of the vertical gradient of ammonia and micrometeorology above a spruce forest in western Jutland, Denmark. Measurements have been made in seven periods, each lasting about one week and covering all seasons and different meteorological situations. Different deposition characteristics were observed, depending on the ammonia concentration and the relative humidity. At conditions with westerly winds, the wind brings air masses from the North Sea with low concentration levels of ammonia to the site, while at conditions with easterly winds, the air have passed central Jutland with large emission areas. Some of the relatively low deposition velocities or emissions were observed during conditions with low ammonia concentration and westerly winds. These observations might relate to a compensation point of the forest, i.e. an ammonia concentration below which the trees and/or the surface emit ammonia due to an equilibrium with the ammonia inside the needles or on the surface. Emission of ammonia was also observed at relatively high ammonia concentration levels (above 2 μg NH 3–N m -3), mainly during one measuring period characterized by easterly winds with dry conditions and high ammonia concentrations, and the emissions might relate to evaporation from ammonia saturated surfaces or emission from mineralization in the forest soil. In general, relatively high net deposition velocities were observed during conditions with relative humidity above 80% or at ammonia concentrations moderate higher than a given (temperature dependent) compensation point. During stable conditions some observations revealed that the gradient above the canopy not necessarily represents the exchange with the canopy.

High concentrations of ammonia, but not volatile amines, in gastric juice of subjects with Helicobacter pylori infection.

Helicobacter pylori (H. pylori) produces large amounts of ammonia. Based on higher readings obtained with an ammonia-sensitive electrode when compared to a specific enzymatic assay, it has been claimed that H. pylori also produces potentially toxic volatile amines. We measured ammonia concentrations (NH3) in gastric aspirates from 11 H. pylori positive subjects (22-40 y, 6 M), using an ammonia electrode sensitive to ammonia and amines, and an enzymatic assay specific for ammonia. Continuous aspiration was performed overnight and 220 aspirates were analyzed before and 6 weeks after cure of H. pylori. Gastric samples were diluted 1:3 (before cure) and 1:1 (after cure) according to dilution curves constructed prior to the assays. Median (95% CI) NH3 detected by the electrode/enzymatic assay were 4.34 mM[4.12-4.61]/4.50 mM [4.28-4.68] (p > .05) before cure and 0.54 mM[0.42-0.60]/0.73 mM[0.71-0.81] after cure (p > .05). Intra-class correlation coefficient between the two methods was 0.91 before cure and 0.90 after cure (p < .001). Without dilution, the enzymatic assay was linear for NH3 from 0.01 to 1 mM and saturated at 2.5 mM; the electrode was linear for NH3 from 0.01 to 20 mM. When appropriate dilutions were performed, the enzymatic assay was accurate for NH3 greater than 2.5 mM. In subjects with H. pylori infection there is a high NH3 in gastric juice; production of volatile amines appears to be negligible in vivo. An ammonia-sensitive electrode and a specific enzymatic assay are both suitable methods for determining NH3 in the gastric juice of subjects with H. pylori infection.

First experiences with methods to measure ammonia emissions from naturally ventilated cattle buildings in the U.K.

A method has been developed to measure the emission rate of ammonia from naturally ventilated U.K. livestock buildings. The method is based on measurements of ammonia concentration and estimates of the ventilation rate of the building by continuous release of carbon monoxide tracer within the building. The tracer concentration is measured at nine positions in openings around the perimeter of the building, as well as around a ring sampling line. Two criteria were evaluated to decide whether, at any given time, a given opening in the building acted as an air inlet or as an air outlet. Carbon monoxide concentration difference across an opening was found to be a better criterion than the temperature difference across the opening. Ammonia concentrations were measured continuously at the sampling points using a chemiluminescence analyser. The method was applied to a straw-bedded beef unit and to a slurry-based dairy unit. Both buildings were of space-boarded construction. Ventilation rates estimated by the ring line sample were consistently higher than by the perimeter samples. During calm weather, the ventilation estimates by both samples were similar (10–20 air changes h -1). However, during windy conditions (>5 m s -1) the ventilation rate was overestimated by the ring line sample (average 100 air changes h -1) compared to the perimeter samples (average 50 air changes h -1). The difference was caused by incomplete mixing of the tracer within the building. The ventilation rate estimated from the perimeter samples was used for the calculation of the emission rate. Preliminary estimates of the ammonia emission factor were 6.0 kg NH 3 (500 kg live-weight) -1 (190 d) -1 for the slurry-based dairy unit and 3.7 for the straw-bedded beef unit.

Measurements of the horizontal gradient of ammonia over a conifer forest in Denmark

Horizontal gradients of ammonia have been measured in order to determine the spatial variation of the concentration above a forest as a function of distance from ammonia emitting areas. Measurements were carried out in June 1994 during conditions with winds from north and west. Concentration levels of ammonia were generally low, ranging from 0.04 to 0.7 μg NH 3-N m -3. At northerly winds the concentration levels were about four times higher than at westerly winds, which relates well to more intensive and larger areas of ammonia emission towards north of the forest. The ammonia concentration decreases in the forest; in general the percentage decreases were lower during northerly winds (16%) than those obtained during westerly winds (67%). This is probably due to the larger extension of emitting areas towards north than towards the west. Model calculations are comparable with the measured ammonia concentration gradients, although calculated concentration levels may be higher than measured due to the use of yearly average emissions as input to the model calculations.

Ammonia variation in sediments: Spatial, temporal and method‐related effects

AbstractIn aquatic systems, ammonia is a common nutrient and pollutant that originates from both natural and anthropogenic sources. The effects of sediment and pore‐water collection methods, and sediment spatial and temporal variability on ammonia concentrations, were evaluated. Sediment and pore‐water collection methods included grab sampling with an Ekman dredge and hand corer followed by centrifugation, in situ suction, and in situ peeper methods. Samples were collected from three sites over a period of several months, with site replicates spaced from 30 to 60 cm and from 6 to 9 m apart. Pore‐water ammonia concentrations differed significantly between the collection methods on most occasions. Ammonia concentrations were highest in the Ekman and corer pore‐water samples as compared to the in situ pore waters collected from the peepers and by suction. Spatial heterogeneity in sediment ammonia concentrations was significant and generally increased with distance. Seasonal fluctuations in ammonia concentrations were evident, with high values in warmer months. Storage effects were observed with pore‐water ammonia over a 1‐ to 4‐week period. Results show that collection methods and natural variability contribute significantly to measured ammonia concentrations and are important considerations in aquatic ecosystem assessments.

Mass Transfer Coefficient and Equilibrium Concentration as Key Factors in a New Approach to Estimate Ammonia Emission from Livestock Manure

A new micrometeorological method is presented of estimating ammonia emission from soil following manure spreading by means of the stirred dynamic chamber technique in combination with passive diffusion sampling. Ammonia volatilization can be parameterized in the expression (Ceq - Ca )Kz,a where P;Ceq = ammonia equilibrium concentration in the air;Ca = ambient ammonia concentration;Kz,a = mass transfer coefficient between the air and the soilCeq is obtained from ammonia concentration measurements in the chamber. Ca and Kz,a can be measured directly in the field by using a new simple technique described in the paper. All three terms are determined by applying the passive diffusion sampler technique. A simple battery-operated chamber for field use was developed and the measuring system was tested in field experiments. The results were positive as regards replicability, simplicity in use and cost effectiveness. The relative standard deviation for duplicate determinations of concentration in the chamber was approximately 4% and the corresponding figure for the average equilibrium concentration obtained in different chambers placed in the same field was approximately 18%. This uncertainty is owing to the fact that the surface areas on which the chambers are placed are not representative of the whole areas.

In situ measurement of ammonia concentration in industrial combustion systems

In the case of noncatalytic reduction of NOx by ammonia, urea or other nitrogen containing compounds, a fast responding ammonia detection system is needed to control the NH3-addition, since the reaction of any residual NH3 with sulfur oxide also present in the flue gas leads to the formation of solid ammonium hydrogen sulfate. This can cause severe damage to plants, especially deposition at heat exchanger surfaces. A laser monitoring system has therefore been developed to measure in situ concentrations of ammonia at temperatures up to 600° C. The NH3 concentration is determined by measuring absorption of 13CO2 emission lines from a tunable 13CO2 waveguide laser. By varying the resonator length, the laser is frequency modulated between two neighboring emission lines. One line coincides with a strong ammonia absorption line while the other is used as a reference. By this referencing the system is autocalibrated continuously. The high spectral resolution of the laser supresses interferences by other species. A detection limit of 1 ppm could be reached at a time constant of 10 s. The system was built up for use in industrial environments and has been applied successfully in several power plants, the chemical industry and waste incinerators.

Ammonia Concentration Measurement by Catalytic Oxidation

An ammonia converter was constructed using a commercially available platinum catalyst, with the aim of applying it for the measurement of ammonia concentrations. The dependence of the ammonia converter efficiency on the reaction temperature and the ammonia concentration was investigated by measuring the concentration of the converted nitric oxide. The results showed that the catalyst almost completely oxidized ammonia into nitric oxide at temperatures above 600°C in the tested range of ammonia concentrations. In addition, by combining the ammonia converter with a chemiluminescent NOx analyzer we were able to measure the ammonia concentration in an ammonia-nitric oxide mixture to an accuracy of within 3% by making a correction due to the oxygen concentration.

Ammonia concentration measurement using oxidizing catalyst.

With the aim of application to the measurement of ammonia concentration, an ammonia converter was constructed using commercially available platinum catalyst. The dependences of the ammonia converter efficiency on reaction temperature and ammonia concentration were investigated by measuring the concentration of the converted nitric oxide. The results have shown that the catalyst used almost completely oxidizes ammonia into nitric oxide at temperatures above 600°C in the tested range of ammonia concentration. In addition, the combination of the ammonia converter and a chemiluminescent NOx analyzer was found to be able to measure ammonia concentration in an ammonia-nitric oxide mixture with a precision within 3% by making a correction due to oxygen concentration.

Evidence for direct repression of nitrogenase by ammonia in the cyanobacterium Anabaena cylindrica

The nitrogenase activity of the cyanobacterium Anabaena cylindrica was repressed upon addition of ammonium salts after preincubation in the presence of a concentration of L-methionine-DL-sulfoximine sufficient to totally inhibit glutamine synthetase. Repression was also observed when urea was added to cells in the presence of the glutamine synthetase inhibitor. Measurements of ammonia concentrations were made in each case and provided evidence that ammonia itself is a primary regulator of nitrogenase levels in A. cylindrica.

Rumen protein degradation and biosynthesis. I. A new method for determination of protein degradation in rumen fluid in vitro.

A method is described for the determination of protein degradation based on measurements of ammonia concentration and gas production (Menke et al. 1979) when a feedingstuff was incubated with rumen fluid in vitro. NH3 liberated during incubation is in part used for microbial protein synthesis. Production of carbon dioxide and methane can be regarded as a measure of energy available for protein synthesis. The ratio, gas production: incorporation of NH3-nitrogen was estimated by addition of starch to the substrate. The response in gas production was linear in the range 0-200 mg starch, when starch was added to 0-200 mg feedingstuff dry matter and 30 ml rumen fluid-medium mixture. Linear regression between NH3-N concentration (y, mg) and gas production (x, ml) yielded an intercept (bo) representing that amount of NH3-N which would be released when no fermentable carbohydrates were available and consequently no bacterial protein synthesis took place. The difference between this intercept bo and NH3-N content in the blank (rumen fluid without substrate added) indicated the amount of NH3 liberated from protein and other N-containing compounds of the feeding-stuff incubated. In vitro-degradable N (IVDN) was calculated as a proportion of total N by the equation: (formula; see text).

Disruption of magnesium regulation in the crab Cancer productus exposed to chlorinated seawater

Exposure of the crab Cancer productus to chlorinated seawater resulted in alterations in haemolymph sodium and magnesium concentrations. At the highest chlorination levels, which approached the 96-h LC 50, regulation of both ions was essentially abolished. Reciprocal changes in the sodium and magnesium levels suggested an effect on the activity of the bladder wall, which has been implicated in the regulation of haemolymph magnesium in crustaceans. Additionally, exposure to 1·19 μg/ml applied Cl (0·68 μg/ml TRO) for 96 h resulted in a fourfold increase in the ammonia excretion rate. Crabs also contributed considerable chlorine demand to the exposure seawater. Measurements of TRO in the inhalant seawater and water exiting the crabs' branchial chambers indicated a reduction in TRO equivalent to 57% of that initially present in the inhalant water (0·51 μg/ml TRO). Measurements of ammonia concentrations in the exposure water indicated that ammonia in seawater was consumed in reactions with oxidants. This was especially evident at higher levels of chlorination. At 0·58 μg/ml applied Cl and above, chlorination resulted in near disappearance of ammonia from the water.

Application of the Phenol—Hypochlorite Reaction to Measurement of Ammonia Concentrations in Kjeldahl Digests of Serum and Various Tissues

Abstract Conditions have been defined that enable the use of nitroprusside as a catalyst for the phenol-hypochlorite reaction when the latter is applied to measurement of nitrogen in Kjeldahl digests containing mercury. This is accomplished by lowering the concentration of mercury to a range where it remains effective in accelerating the destruction of organic matter during digestion but no longer reacts with nitroprusside. In addition, the use of minimal concentrations of nitroprusside diminishes further the possibility of interference by mercury and has the added advantage of decreasing the pH dependence of indophenol blue formation. The sensitivity of the reaction makes possible measurement of nitrogen in very small samples with relatively short digestion times.