Differences In Ammonia Concentrations Research Articles

Ammonia level sensor using tapered optical fiber coated with titanium dioxide-incorporated porphyrin

Since ammonia is water-soluble, environmental studies have shown that the industrial waste such as fertilizer manufacturing, food products, palm oil, urea fertilizer industry can cause very serious damage to water body ecosystems if not properly managed, resulting in a decrease in water quality. Devices based on optical technology, especially devices that combine optical fibers and nanomaterials, are identified as highly sensitive to the species of interest by detecting changes in physicochemical properties. A practical, easy-to-use, inexpensive instrument for detecting ammonia level was proposed using tapered optical fiber (TOF) coated with titanium dioxide-incorporated porphyrin. TOF was fabricated by simultaneously stretching and heating. The preparation of TiO2/porphyrin/gelatine was prepared to coat tapered optical fiber by dipping. SEM analysis shows an increase in length and a decrease in diameter, also the successful coating of titanium dioxide and porphyrin in the taper region. The EDX analysis also proves the presence of the Ti element in the TOF layer. The TOF produces significant sensing performances toward the ammonia liquid concentration level. The TOF coated with titanium dioxide-incorporated porphyrin can detect a one ppm difference in ammonia concentration with a certain range of output voltage for every concentration has.

Comparative Metagenomic Analysis of Two Hot Springs From Ourense (Northwestern Spain) and Others Worldwide.

With their circumneutral pH and their moderate temperature (66 and 68°C, respectively), As Burgas and Muiño da Veiga are two important human-use hot springs, previously studied with traditional culture methods, but never explored with a metagenomic approach. In the present study, we have performed metagenomic sequence-based analyses to compare the taxonomic composition and functional potential of these hot springs. Proteobacteria, Deinococcus-Thermus, Firmicutes, Nitrospirae, and Aquificae are the dominant phyla in both geothermal springs, but there is a significant difference in the abundance of these phyla between As Burgas and Muiño da Veiga. Phylum Proteobacteria dominates As Burgas ecosystem while Aquificae is the most abundant phylum in Muiño da Veiga. Taxonomic and functional analyses reveal that the variability in water geochemistry might be shaping the differences in the microbial communities inhabiting these geothermal springs. The content in organic compounds of As Burgas water promotes the presence of heterotrophic populations of the genera Acidovorax and Thermus, whereas the sulfate-rich water of Muiño da Veiga favors the co-dominance of genera Sulfurihydrogenibium and Thermodesulfovibrio. Differences in ammonia concentration exert a selective pressure toward the growth of nitrogen-fixing bacteria such as Thermodesulfovibrio in Muiño da Veiga. Temperature and pH are two important factors shaping hot springs microbial communities as was determined by comparative analysis with other thermal springs.

Increased air velocity in the lying area improves pen hygiene and reduces ammonia emissions from houses with partly slatted pens for growing/finishing pigs

Partly slatted pens can offer growing/finishing pigs a better house environment than pens with fully slatted floors. Under thermoneutral conditions, pigs prefer to rest on a solid area and some litter can be provided as enrichment. Ammonia emissions are lower in systems with partly slatted pens, provided the pens are kept clean. However, under high-temperature conditions, pigs in partly slatted pens may begin lying on the slatted area and fouling on the solid floor area, resulting in increased ammonia emissions. This study examined the effects of increasing the air velocity (IAV) in the lying area from max 0.5 m s−1 to max 1.0 m s−1 on conditions for pigs in partly slatted pens during warm periods. Air velocity was increased by redirecting the inlet air from the ceiling inlets down into the animal zone.The study was performed in a commercial growing/finishing house with 10 identical rooms, each containing 16 pens for 9-14 pigs growing from 25-30 kg to 115-120 kg live weight. Pigs were introduced simultaneously into two parallel rooms, one with IAV in the lying area and one without (control treatment). During two summers with six batches, concentrations of carbon dioxide (CO2) and ammonia (NH3), pig activity and choice of lying area in the pen, pen fouling and NH3 emissions were recorded in both rooms on four measuring occasions (M1-M4) during the growing period. Gas concentrations were measured by photoacoustic analyser, pig activity and pig choice of lying area by machine vision techniques, and pen fouling by visual inspection. Climate parameters (air temperature, relative humidity) were logged continuously during the growing period. Ammonia emissions were calculated from the ventilation rate (determined by the indirect CO2 tracer gas method) and the difference in ammonia concentration between outlet and inlet air.Under high ambient temperatures, pigs in the IAV treatment were observed lying significantly more often (p<0.05) in the part of the lying area with the highest air velocity. Pigs tended to lie less in the slatted area (p=0.052) in the IAV treatment than in the control. Problems with pen fouling were significantly reduced with increased air velocity in the lying area and NH3 emissions were reduced by 21% (p=0.009), from 8.4 to 6.6 g pig−1 day−1, during the late growing period (M4).In conclusion, increasing air velocity in the lying area of partly slatted pens from max 0.5 to max 1.0 m s−1 influenced pigs´ choice of lying area, improved pen hygiene and reduced ammonia emissions.

Optical fiber dislocation ammonia gas sensor based on self-assembled film

This paper presents the ammonia gas sensor of optical fiber dislocation type based on single-walled carbon nanotubes (SWCNTs)-polymer self-assembled composite film. Alone with high-Q resonator, the film has a large number of free carboxyl groups and a large specific surface area, which provides strong interaction between light and the film, as well as high adsorption and selectivity to ammonia. The spectrum from the sensor varies with the effective refractive index affected by the ammonia concentration. In the low concentration range of (10−37)×10−6, the ratio of the spectral change to the ammonia concentration difference (i.e. the sensitivity) is of 13.25 pm/10−6, a detection limit is 3.77×10−6 with good linearity. This work provides an effective method for developing low-concentration and high-selectivity ammonia sensors.

Cooling growing/finishing pigs with showers in the slatted area: Effect on animal occupation area, pen fouling and ammonia emission

Growing and finishing pigs kept in insulated buildings are often exposed to high ambient temperature during summer. In high-temperature conditions, pigs in partly slatted pens change their behaviour to increase lying on the slatted area and fouling on the solid floor area, resulting in increased ammonia emissions. One way to cool the animals is to shower/sprinkle water in the slatted area, allowing pigs to wet their skin to increase heat loss. This study examined the effects of providing showers on pig activity and occupation area in pens, pen fouling and ammonia emission from the room. The investigation was performed in a commercial growing-finishing house with 10 identical rooms, each containing 16 pens for 9–13 pigs growing from 25–30 kg to 115–120 kg. Pigs were introduced into two parallel rooms in the house. During two summers and four batches, one room with showers in the slatted area and one room without per batch were compared in terms of concentrations of carbon dioxide (CO2) and ammonia (NH3), pig activity and occupation area in the pen, pen fouling and NH3 emissions, recorded on four measuring occasions (M1–M4) during the growing period. Gas concentrations were measured using a photoacoustic analyser, pig activity and occupation area detected by machine vision techniques and pen fouling was visually investigated. Climate parameters (air temperature and relative humidity) were logged continuously during the entire growing period. Ammonia emission was calculated from ventilation rate (determined by the indirect CO2 tracer gas method) and the difference in ammonia concentration between outlet and inlet air.The results showed that the pigs spent less time lying on the slats (p < 0.05) and the solid floor was cleaner (p < 0.05) on measuring occasions M2, M3 and M4 in rooms with showers than in control rooms. Mean NH3 emission for the four measurement occasions were 3.0–5.1 g pig−1 day−1 and 4.2–10.0 g pig−1 day−1 for the shower and control rooms, respectively. The differences were significant (p < 0.05) for all measuring occasions. The results also show improved animal environment when using showers to cool pigs at high ambient temperatures.Overall, providing showers in the slatted area in partly slatted pens encouraged growing/finishing pigs to lie in the lying area, reduced problems with pen fouling and decreased NH3 emissions by 45%. The latter could be partly due to reduced pen fouling and partly to dilution of urine on the slatted area and on the surface of slurry in the pit.

THE ORETICAL ANALYSIS ON THE PERFORMANCE OF BRANCHED GAX CHILLER CYCLE

In this study, a branched GAX absorption cycle operating with NH3-H2O pair has beeninvestigated to assess its performance under steady state conditions. The cycle modeling isimplemented using Engineering Equation Solver (EES) software. Analysis includesequations of mass, species and energy conservation. The analysis is used to simulate a GAXabsorption chiller utilization for air conditioning applications with a nominal capacity of 95TR. This chiller uses solar collectors as heat source. The operating parameters are selected atdifferent values of the heat source temperature (140 - 185°C), condenser exit temperature(30 to 48°C), evaporator exit temperature (2 to 11°C) ; split ratio (0 to 0.18); the difference inammonia concentration(0.25-036), mass flow rate in solution pump mr=1 kg/s; heatexchanger effectiveness ? ? 0.8. The results showed that the average COP is sensitive tooperating conditions where the average COP and cooling capacity of the branched GAXabsorption chiller increase with increasing generator and evaporator temperature whereasthey decrease with increasing condenser temperature. Simulation results also show that thesplit ratio and ammonia concentration difference have a significant impact on theperformance of absorption chiller.

Forward osmosis: Evaluation thin-film-composite membrane for municipal sewage concentration

Forward osmosis (FO) is a concentration process based on the natural phenomena of osmosis. It is nowadays considered a breakthrough technology that can be potentially used for concentrating suspensions and solutions, including wastes such as sewage. The diluted nature of sewage restricts the treatment technologies that can be applied. Then, sewage concentration by FO could represent a habilitating technology enabling the application of a wider range of treatment alternatives. This research studied sewage and pre-filtered sewage concentration by a FO. Thin-film-composite (TFC) and cellulose triacetate (CTA) FO membranes were considered. Results showed that TFC membranes presented higher fluxes than CTA, when operated with clean water and sewage. Filtration experiments were done using sewage and filtered sewage as feeds. Even though differences in formed fouling layers were identified by scanning electron microscopy, observed fluxes were similar. Energy dispersive X-ray spectroscopy was done to study the elemental composition of the fouling layers. Results revealed nitrogen contents in the range 10–13%, suggesting a relevant role of protein. At tested conditions, TFC membrane showed little apparent ammonia rejection due to permeation to the draw solution. Ammonia permeation was independent of applied osmotic potential, and was mainly related with the ammonia concentration difference through the membrane. Results show that concentration of sewage by forward osmosis would be technically feasible, and its application could potentially improve energy recovery from sewage. However, main drawback that needs to overcome is a low water-flux, which translates into high membrane requirements.

Effects of different air inlets on indoor air quality and ammonia emission from two experimental fattening pig rooms with partial pit ventilation system – Summer condition

It has previous been demonstrated that a pit ventilation system could improve indoor air quality and reduce ammonia emission significantly from pig production if an air purification system was installed to treat the pit exhaust air. However, the knowledge about the influence of a partial pit exhaust unit treating a small part of the ventilation (10%) in a ventilation system with different types of air inlets on indoor air quality and ammonia emission from pig house is still lacking. In this study, two rooms, both with partial pit exhaust and ceiling-top room exhaust units, were used. One room was equipped with ceiling air inlet (system C) and another room was equipped with wall jet air inlet (system W). Each room had 32 fattening pigs. The maximum ventilation rate in each room was set as 3200 m3 h−1. Room ventilation rate was automatically controlled by a climate control strategy based on indoor thermal conditions, while pit ventilation rate was fixed at 10% of the maximum ventilation rate. Ammonia concentrations were measured in air inlet, room exhaust and pit exhaust for both systems. Air flow rates and ammonia concentrations were measured and recorded continuously. Results showed that ventilation rate requirement was higher in system C than in system W (22.3%, p < 0.001) to maintain the setup indoor thermal condition during the whole fattening period. In the meantime, significant higher ammonia concentrations and emissions in both pit and room exhausts were found in system W than in system C (p < 0.001). The ammonia emission ratio of pit exhaust, defined as the emission via pit exhaust divided by the total emission, in systems C and W was 48% and 47%, respectively. If applying an effective air purification system, a significant reduction of ammonia emission could be achieved. The gap of ammonia concentration difference between system C and W increased in the later stage. Higher room ventilation rate led to smaller difference of ammonia concentration in room air. Slurry depth had a positive effect on the ammonia emission from pit exhaust. No significant difference in the pigs' activity was found between the two ventilation systems.

Avaliação de poluentes aéreos em instalações de creche e terminação de suínos

Esta pesquisa foi desenvolvida em duas instalações para suínos nas fases de creche e terminação, em duas salas cada, em granjas localizadas no município de Salto, SP, com os objetivos de avaliar a concentração de amônia e poeira e a presença de fungos, além de estimar os riscos de exposição ocupacional a esses agentes ambientais. As avaliações foram realizadas conforme preceituam as normas NR-15, NIOSH e ACGIH. Os resultados indicaram diferença significativa nas concentrações de amônia em relação aos horários, às instalações e aos períodos do dia. Estes também indicam negligência para a questão da ventilação sanitária nas instalações de creche, com conseqüentes teores mais altos de amônia, e que estes estão vinculados à circulação de ar no interior das instalações, ao manejo dos dejetos e da cortina, à tipologia da construção e às condições de clima local, além da lotação e da densidade de suínos. A concentração de poeira total foi mais alta nos prédios de creche (0,84-9,16mg m-3) do que nos de terminação (0,84-3,34mg m-3), enquanto que a poeira respirável foi mais alta na creche, ficando inferior a 3,67mg m-3 e dentro dos limites de insalubridade para o trabalhador. Foram encontrados fungos do gênero Aspergillus, Penicillium e Neurospora em suspensão no ambiente interno das instalações estudadas.

Parâmetros da degradação protéica ruminal de diferentes alimentos e rações estimados por técnica in vitro

Foram realizados três experimentos para estudar os parâmetros de degradação protéica ruminal. No primeiro, foram incubadas, em líquido ruminal de bovinos, dietas isoprotéicas contendo capim-elefante, fubá de milho e farelo de soja, em cinco níveis de concentrado (0:100, 25:75, 50:50, 75:25 e 100:0), adicionado ou não de monensina (5µM). Houve efeito linear decrescente do nível de concentrado sobre a concentração de amônia e degradabilidade da proteína bruta (DPB), e efeito cúbico sobre a concentração de proteína solúvel, com máximo valor em dieta com 25% de concentrado. A monensina diminuiu a DPB e a concentração de proteína solúvel, sem afetar a produção de amônia. No segundo experimento, foram incubados cinco diferentes volumosos (silagens de milho - Zea mays L. e de capim-elefante - Pennisetum purpureum, silagem pré-secada de braquiária -Brachiaria decumbens, feno de Tifton 85 -Cynodon sp. amonizado e feno de Tifton 85). A silagem pré-secada de capim-braquiária e o feno de Tifton 85 amonizado apresentaram as maiores concentrações de amônia (8,7 e 5,3mg/dl) e proteína solúvel (5,4 e 7,0mg/dl), devido aos seus maiores teores de PB, seguidos da silagem de capim-elefante e feno de Tifton 85. A DPB variou de 29,6 a 80,6%, para a silagem pré-secada de braquiária e para o feno de Tifton 85, e a degradabilidade potencial da matéria seca de 40,1 a 64,3%, para a silagem de capim-elefante e silagem pré-secada de braquiária, respectivamente. A degradabilidade efetiva da proteína bruta apresentou baixos valores devido à baixa taxa de degradação da fração insolúvel. No terceiro experimento, foram incubados diferentes tipos de camas de frango (casca de café, capim-elefante seco picado, sabugo de milho ou cepilho), contendo ou não monensina (5µM). Não houve diferença nas concentrações de amônia entre as diferentes camas de frango, na ausência de monensina. Entretanto, com monensina, a cama de capim-elefante apresentou o menor nível de amônia e a de cepilho, o maior. As camas influenciaram o conteúdo de proteína solúvel e a DPB, que variaram de 9,0 a 14,5mg/dl e 39 a 63%, respectivamente, sem efeitos da monensina.

Gas exchange between plant canopies and the atmosphere: Case-studies for ammonia

We first present the elements of an inverse Lagrangian model of gas transport in plant canopies. The model allows the inference of sites of gas exchange in the canopy and their source and sink strengths from measured profiles of mean gas concentration and statistics of the canopy turbulence. The practical application of the model is demonstrated through a case study of the fate of ammonia volatilized from fertilizer applied to the floor of a sugarcane crop. Some of the lost ammonia was absorbed by the foliage of the crop; the rest was lost to the atmosphere above. While there was excellent agreement between model predictions of the net flux from the canopy and independent micrometeorological measurements of ammonia flux in the air-layer above it, verification of flux predictions within the canopy was much more difficult. Appeal was made to a process-based model of canopy gas exchange that describes gas transport to and from foliage surfaces in terms of diffusion across aerodynamic, boundary-layer and stomatal resistances in response to a difference in ammonia concentration between the air and leaf sub-stomatal cavities. There was acceptable agreement between the two models in their predictions of foliage ammonia uptake. Next, we apply the process model to a study of the recapture of volatilized ammonia by sugarcane crops with different leaf area indices (LAI). The study indicated recoveries increasing almost linearly with LAI and suggested probable recoveries in excess of 20% for canopies with LAIs of 2 or more. These and other published studies of ammonia exchange between canopy and atmosphere that employed both the inverse Lagrangian and process models suggest that their coupling provides a powerful tool for studying canopy gas exchange.

Inactivation of Ascaris suum Eggs by Ammonia

Uncharged ammonia is known to cause inactivation of a number of wastewater pathogens, but its effect on Ascaris eggs has never been isolated or quantified. The objectives of this research were to determine the conditions under which ammonia inactivates eggs of the swine Ascaris species, Ascaris suum, and to quantify the impact of ammonia on the U.S. EPA's requirements for alkaline treatment to produce Class A sludge. Eggs were incubated in controlled, laboratory solutions such that the effects of ammonia concentration and speciation, pH, and temperature could be separated. With a 24-h incubation, the inactivation at all pH levels (range 7-11) was not statistically different in the absence of ammonia. The presence of ammonia (0-1000 ppm as N) significantly increased Ascaris egg inactivation at pH 9 and 11, and the ovicidal effect was directly related to the concentration of the uncharged NH3 species. Increasing temperatures (32-52 degrees C) caused increased inactivation at all pH levels and ammonia concentrations. The current EPA treatment requirements to produce Class A biosolids by alkaline treatment have temperature, pH, and time requirements, but do not account for the effectof differences in ammonia concentration on inactivation. To illustrate the potential savings in temperature and pH that could be achieved when accounting for ammonia inactivation, the combinations of ammonia concentration, temperature, and pH neededto achieve 99% inactivation after 72 h were determined. The presence of ammonia at concentrations encountered in sludges and feces (up to 8000 ppm as N) allowed for 99% egg inactivation to be achieved at temperatures up to 14 degrees C lower than ammonia-free controls. Thus, environmentally relevant concentrations of ammonia may significantly increase the rate of Ascaris egg inactivation during alkaline stabilization.

Splanchnic and leg exchange of amino acids and ammonia in acute liver failure

Background & Aims: In patients with acute liver failure, hyperammonemia is associated with cerebral herniation. We examined the splanchnic and leg exchange of amino acids, urea, and ammonia in such patients. Methods: Bedside liver vein catheterization was used in 22 patients after development of hepatic encephalopathy grades III-IV. Femoral venous blood was sampled in 7 of these patients. Results: Arterial amino acid concentration (8.1 ± 4.1 mmol/L) was increased 4-fold above normal. Glutamine (2.4 ± 1.8 mmol/L) and alanine (0.57 ± 0.35 mmol/L) were by far the predominant amino acids exchanged in the splanchnic and leg circulation. In the splanchnic circulation, there was a net uptake of glutamine (241 ± 353 μmol/min) and ammonia and alanine were released in an almost 1:1 stoichiometry ( r 2 = 0.47; P < 0.001). In the leg, ammonia and alanine were removed and glutamine released. The leg ammonia concentration difference was correlated to that of glutamine ( r 2 = 0.80; P = 0.008) and alanine ( r 2 = 0.67; P = 0.03). Conclusions: Splanchnic metabolism of glutamine in combination with decreased hepatic function was responsible for the splanchnic release of ammonia and alanine. These processes were reversed in skeletal muscle. Stimulation of skeletal muscle metabolism of ammonia could be a important target for future treatment of patients with acute liver failure. GASTROENTEROLOGY 2000;118:1131-1139

Helicobacter pylori and ammonia concentrations of whole, parotid and submandibular/sublingual saliva.

The aim of this study was to determine the ammonia concentration in whole, parotid and submandibular/sublingual saliva of healthy volunteers using the indophenol direct method. It also investigated the hypothesis that higher saliva ammonia concentrations are associated with the presence of Helicobacter pylori (H. pylori) in the oral cavity. In healthy volunteers, the mean ammonia concentration of whole saliva (2574 mumol/l) was significantly higher (P < 0.0001) than the mean ammonia concentration of both parotid (238 mumol/l) and submandibular/sublingual (355 mumol/l) saliva. In whole saliva, no difference in ammonia concentration was found between healthy controls and dyspeptic patients (mean ammonia values 2574 and 2489 mumol/l respectively, P = 0.7). In addition, no significant differences were observed in the salivary ammonia concentration between dyspeptic patients with and without H. pylori carriage. It is concluded that the ammonia concentration in parotid and submandibular/sublingual saliva does not differ, but is significantly lower than the ammonia concentration of whole saliva. This difference is not due to carriage of H. pylori with its strong urease activity. Therefore, the determination of ammonia in whole saliva is an inappropriate screening test for patients being at risk for (chronic) gastritis and peptic ulcer disease.

Effects of addition of urea to a low nitrogen diet on the rumen digestion of a range of roughages

Four steers were given 2 diets consisting of oat hay and molasses which contained either no urea or 4% urea. Sixteen roughages (including cottonwool, straws, alkali-treated straws, and grass and legumes hays) were incubated in synthetic fibre bags in the rumen for 24 h, and the disappearance from the bags of insoluble organic matter (OM) was determined. In steers given molasses containing 4% urea, rumen ammonia concentrations exceeded 100 mg N/Lfor only about 5 h during the 24-h cycle and were &lt;50 mg N/L within about 4 h after feeding. In steers given molasses without urea, rumen ammonia concentration averaged 7 mg N/L. The depression in OM disappearance from synthetic fibre bags due to the low rumen ammonia concentrations, expressed as a percentage of the disappearance at the higher rumen ammonia concentration, ranged among the roughages from 24 to 87%, and was inversely related to the N content of the roughage. In additional experiments the differences in ammonia concentration between rumen fluid sampled from the ventral sac of the rumen and fluid extracted from synthetic fibre bags were small compared with the differences between diets. These results indicated that the effect of low rumen ammonia concentrations on microbial digestion in the rumen varied widely among roughages.

The differences in ammonia concentration in porcine follicular fluid from varied sizes

The differences in ammonia concentration in porcine follicular fluid from varied sizes

Protein Solubility, In Vitro Ammonia Concentration, and In Situ Disappearance of Extruded Whole Cottonseed and Other Protein Sources

Whole cottonseed extruded at temperatures (°C) and rates (kg/h) of 131, 314; 135, 182; 146, 195; and 156, 286 was evaluated by protein solubility, in vitro ammonia concentration, and in situ disappearance techniques. These techniques were used to estimate potential of extruded whole cottonseed for protein escape from the rumen. In addition, raw whole cottonseed, soybean meal, corn gluten meal, and whole cottonseed and soybean meal heated for 4h at 127, 138, and 149°C were used for comparison. Solubility was by three methods: cold water mixed for 30min, cold water homogenized for 5s, and hot water refluxed for 1h. In vitro ammonia concentration was measured after 2, 4, and 6h of incubation. Dry matter and CP disappearance was estimated using nylon bags suspended in the rumen for 1, 2, 4, 8, 12, and 24h.Extrusion reduced solubility of cottonseed as measured by all three methods. There was no difference in ammonia concentration due to extrusion. Whole cottonseed responded similarly to extruded products at all time intervals. Extruded products differed over time with the in situ technique. The two highest extrusion temperatures resulted in mean DM and CP disappearance rates of 1.32 and 1.32%/h compared with whole cottonseed (1.52, 6.08) and the other extrusion treatments (1.96, 2.92).

Measurement of nitrification rates in lake sediments: Comparison of the nitrification inhibitors nitrapyrin and allylthiourea

A method for measuring rates of nitrification in intact marine sediment cores has been modified and adapted for use in freshwater sediments. The technique involves subsampling a sediment core into minicores. Half of these cores are treated with an inhibitor of chemolithotrophic nitrification and, after incubation, differences in ammonia and nitrate concentration between inhibited and uninhibited systems are calculated. The within-treatment variability of ammonia and nitrate concentrations could be reduced by storing the cores overnight prior to subsampling. Estimates of the nitrification rate using the difference in ammonia concentrations between the inhibited and uninhibited mini-cores were always greater than the rate estimate using the difference in nitrate concentrations. Comparison between the results using the nitrification inhibitors allylthiourea (ATU) and nitrapyrin (N-Serve) indicated that the former appeared to give larger values for the nitrification rate than did the latter. Differences in the efficiency of these inhibitors in the control of nitrification under the conditions used partly explain these results. Data are also presented on the effect of N-Serve and ATU on some other nitrogen transformations affecting ammonia and nitrate concentrations.

The spatial distribution of nutrients in the South Basin of Windermere

SUMMARY. The vertical and horizontal distribution of electrical conductivity, soluble reactive phosphorus (SRP), total phosphorus, ammonia‐nitrogen and nitrate‐nitrogen in the South Basin of Windermere is described and related, where possible, to spatial variations in phytoplankton and zooplankton.For most variables, the maximum range of horizontal variation on a single day was greater than the maximum range of seasonal variation measured at a single station over a full year. Horizontal variations in SRP and ammonia were particularly high, with coefficients of variation often exceeding 100%. The errors associated with sampling at a single station were most pronounced when local accumulations of zooplankton or phytoplankton occurred in the lake.Horizontal variations in conductivity were primarily influenced by the discharge of treated sewage effluent into the central region and the mass transport of water from the more oligotrophic North Basin. Occasionally, more widespread variations in conductivity appeared to be related to spatial variations in photosynthetic activity. The major factor influencing the horizontal distribution of SRP was the discharge of treated effluent into the central region. Despite the intensive recycling of phosphorus, SRP concentrations were nearly always 10–30% higher near the sewage works than elsewhere in the basin. On a few occasions, significant horizontal differences in SRP concentration were also detected within downwind accumulations of crustacean zooplankton. Horizontal variations in total phosphorus were produced by spatial differences in SRP concentration or by local accumulations of phytoplankton or zooplankton. Horizontal differences in ammonia concentration appeared to be produced, both by the effluent discharge and by the turbulent transfer of nutrients from sediments in shallow water.Observations of effluent movement and dispersion demonstrate that wind‐induced water movements tend to recirculate nutrient‐rich water in the central region and limit mixing along the axis of the basin. The statistical implications of nutrient heterogeneity are discussed in relation to sampling strategy and the possible effects of persistent nutrient concentration gradients on phytoplankton patch formation are assessed.

Ammonia toxicity in cattle. V. Ammonia concentration of lymph and portal, carotid and jugular blood after the ingestion of urea.

Four rumen-fistulated Holstein steers were fitted with cannulas for the collection of portal, jugular and carotid blood. In addition, the thoracic duct of one steer was cannulated for the collection of lymph. Steers were given .125, .25 or .5 g urea/kg body weight 16 hr after a previous feeding. Within 5 min after the administration of the .5-g dose, rumen ammonia increased from 9.7 to 32.0 mg/100 ml, rumen pH from 6.47 to 7.87; portal blood ammonia from 1.02 to 8.01 mg/100 ml, carotid blood ammonia from .18 to 1.17 mg/100 ml and jugular blood ammonia from .13 to .36 mg/100 ml. Lymph ammonia increased from .22 to .32 mg/100 ml within 15 minutes. The .125- and .25-g doses or urea produced proportionate changes. In a second experiment, three Jersey cows were given .5 g urea/kg body weight, and the rates at which urea appeared in carotid and jugular blood were determined. Only small amounts of urea appeared in carotid and jugular blood during the first 5 min after dosing, but the concentrations then increased slowly but progressively. We concluded that because carotid blood ammonia concentration increased so rapidly after dosing with urea, ammonia must leak past the liver, and it is therefore unlikely, that there is a liver threshold for ammonia which must be exceeded before ammonia will reach the carotid artery. The marked difference in ammonia concentrations in carotid and jugular blood suggests that the brain takes up ammonia rapidly. While some ammonia is absorbed via the lymph, and thus bypasses the liver, the lymph does not appear to be a major contributor of ammonia to carotid blood.