Ammonium concentration

Fig. 2 Longitudinal changes in nutrient concentrations below the effluent input of a WWTP without tertiary treatment in La Tordera Stream. Values are the average ( SEM) of monthly measurements done over a year (see more details in [47]). In the left panel, note the net decline of ammonium concentration with concomitant net increases in nitrate concentration, suggesting a potential hot spot for nitriflcation. However, in the latest meters downstream, dissolved inorganic nitrogen (DIN) tends to decrease, which indicates net lost of DIN possibly due to denitrification. The right panel shows net changes in phosphate and dissolved organic carbon (DOC) concentrations. While phosphate does not exhibit any clear trend on an annual basis, DOC seems to decline similarly to DIN, which supports the relative dominance of denitrification...

Most plant species are able to absorb and assimilate nitrate, ammonium, urea, and amino acids as nitrogen sources, but the response to a particular form of nitrogen varies from species to species (114). For example, optimal growth of tomato roots occurs in soil with a ratio of nitrate to ammonium of 3 1 and is inhibited if the ammonium concentration is too high (115). By contrast, white spruce has a strong preference for ammonium (116), whereas some arctic sedges prefer amino acids (117). 

A microhole-based ITIES has been used by Osborne et al. for amperometric determination of ionic species in aqueous solutions [12]. They studied the assisted ammonium transfer with DB1816 at the water-DCE interface. Because the concentration of iono-phore in the organic phase was high, the measured steady-state current was proportional to the concentration of ammonium in the aqueous phase. The time required to reach a steady state was relatively short (e.g., 5 s for an 11/xm hole). A linear relationship was found between the steady-state plateau current and the ammonium concentration over the range 1 to 500/aM. 

Metals have been shown to negatively affect nitrogen transformation and urea hydrolysis. For example, Antil et al.69 discovered that the microbial biomass in a soil receiving sewer water or industrial wastewater decreased with increasing concentrations of cadmium and nickel. The rate of urea hydrolysis was 1.6 times greater in an uncontaminated soil than in a soil containing 0.026 mg Ni g 1. Ammonium concentrations increased for up to 14 days in a soil containing over... 

The ammonium dynamics showed that the initial concentrations of N were reduced after the first 3 days, and after that, a release of the mineral occurred from day 3 up to day 14. Later still, the concentration of ammonium decreased by up to < 14 mg N kg 1 dry soil for all the treatments in both the Otumba and Texcoco soils, and the ammonium concentration decreased by up to < 2 mg N kg 1 dry soil for all treatments, except for the soil treated with sterilized sludge, < 31 mg N kg 1 dry soil. The contour of the ammonium dynamics was similar in both the Otumba and Texcoco soils. Many abiotic and biotic processes might affect the concentration of NH4+ in soil, such as NH4+ fixation in the soil matrix, volatilisation of NH3, and immobilization or oxidation of NH4+. Some soil processes were occurring at too low a level to be detectable, such as NH4+ fixation and the volatilisation of NH3. The nitrate dynamics were similar in both soils. The concentration of N03 was 120 mg N kg 1 dry soil in the control treatment in both soils. The ammonium concentration was similar in both soils, > 200 mg N kg 1 dry soil, treatments with sludge reached > 255 mg N kg 1 dry soil and > 300 mg N kg 1 dry soil in the Texcoco and Otumba soils respectively, and soils treated with sterilized sludge increased the concentration... 

If ammonium concentrations in seawater are low, phytoplankton will assimilate nitrate and nitrite using chemical-specific permeases. Once inside the cell, these DIN species are transformed into ammonium via redox reactions in which nitrogen is reduced to the -III oxidation state ... 

The stepwise nature of nitrification during the aerobic decomposition of detrital PON is illustrated in Figure 24.6. Initially, the degradation of PON produces ammonium, which stimulates the growth of the nitrate oxidizers. These bacteria transform the ammonium into nitrite, causing ammonium concentrations to decline and nitrite concentrations to rise. The elevated nitrite levels stimulate the growth of the nitrite oxidizers. These bacteria transform the nitrite into nitrate. Eventually all of the DIN is oxidized to nitrate. The residual pool of PON includes microbial biomass and any PON too inert to be degraded by aerobic marine bacteria. 

Turner Designs Inc. [Online], Ammonium Concentration Determination, available http //www.tumerdesigns.com/ t2/doc/appnotes/S-0025.pdf accessed 20 November 2009. 

The onset of FE ordering in D-RADP-30 is shifted down to 80 K. Another feature of this composition is that the FE volume fraction grows much less on lowering the temperature than in D-RADP-0.25 and seems to saturate at 30% for temperatures below 40 K. For ammonium concentrations above about 33% no FE domains or clusters are formed from room temperature down to low temperatures in the pseudo-spin glass D-RADP-x. 

Reflectance measurements provided an excellent means for building an ammonium ion sensor involving immobilization of a colorimetric acid-base indicator in the flow-cell depicted schematically in Fig. 3.38.C. The cell was furnished with a microporous PTFE membrane supported on the inner surface of the light window. The detection limit achieved was found to depend on the constant of the immobilized acid-base indicator used it was lO M for /7-Xylenol Blue (pAT, = 2.0). The response time was related to the ammonium ion concentration and ranged from 1 to 60 min. The sensor remained stable for over 6 months and was used to determine the analyte in real samples consisting of purified waste water, which was taken from a tank where the water was collected for release into the mimicipal waste water treatment plant. Since no significant interference fi-om acid compounds such as carbon dioxide or acetic acid was encountered, the sensor proved to be applicable to real samples after pH adjustment. The ammonium concentrations provided by the sensor were consistent with those obtained by ion chromatography, a spectrophotometric assay and an ammonia-selective electrode [269]. 

Exchange was measured at typical pore-water concentrations of Ca2+ and NH4 +. For the Ca2+-saturated and NH4+-saturated sediments, KG was calculated by mass balance from measurements of initial and final calcium and ammonium concentrations in solution the total concentration of exchange sites was known. On the untreated sediment, KG could be determined only after these simplifying assumptions were made ... 

The product portion of the total effluent is that fraction containing less chloride than the feed. In general, the chloride content starts at a value slightly less than in the feed, decreases to a minimum, and then more slowly rises to the feed value as the ion exchange process slows down. The ammonium concentration decreases with volume through in this fraction. 

Ammonium ions. Ammonium bromide reacted with cesium, but the reaction was too rapid to be studied in our system, even at an ammonium concentration of 10 4 M. This indicates that the bimolecular rate constant is greater than 106 M l sec.-1... 

A 61-year-old man with epilepsy had altered consciousness after his dose of valproate was increased because of poor seizure control. Electroencephalography showed triphasic waves and high-amplitude delta-wave activity with frontal predominance. Although serum aspartate transaminase and alanine transaminase were normal, the serum ammonium concentration was high at 960 ng/ml (reference range 30-470). Serum amino acid analysis showed multiple minor abnormalities. Valproate was withdrawn. He improved within 4 days... 

It is difficult to establish a relation between valproate encephalopathy and increased serum ammonium concentrations. Valproate-induced hyperammonemic encephalopathy has been reported in several single case reports, but still it is difficult to ascertain whether hyperammonemia or valproic acid is the cause of the encephalopathy. In one case valproate was used in combination with lithium, which in itself could have caused encephalopathy by displacement of protein binding or other mechanisms, regardless of hyperammonemia (1181). In a second case it was also impossible to evaluate the effect of hyperammonemia on the level of consciousness, since it involved a woman who took valproic acid (30 g) in addition to... 

Holmes, R.M., McClelland, J.W., Sigman, D.M., Fry, B., and Peterson, B.J. (1998) Measuring 15N-NH4+ in marine, estuarine and fresh waters an adaptation of the ammonia diffusion method for samples with low ammonium concentrations. Mar. Chem. 60, 235-243. 

FIGURE 7.17 Experimental test of the reduction of the ammonium concentration C[%] in 5L vessels, containing 500 g of young Tilapia fish, to which 40% (A), 20% ( ), and 10% ( ) of the zeolite sample CMT were added. The concentration C[%] was measured using for comparisson a container with 0% of zeolite added where the ammonium concentration was taken as C = 100%. 

Another method for the reduction of NH4 levels in fish culture installations is the addition of clinoptilolite directly to fish culture tanks [5,85], Figure 7.17 shows a decrease in the ammonium concentration, C[%], versus time in a 5L vessel containing 500g of Tilapia juvenile fishes, where 40%, 20%, and 10% of the zeolite sample CMT were added, and where the percent (%) decrease is represented by [85]... 

The concentration was measured by comparing against a container (% = 0) having no zeolite, where the ammonium concentration in this container was taken as C [%] = 100%. A similar test was carried out in the aquaculture experimental station in Manzanillo, Cuba [85], Even though natural zeolites are inexpensive, it has limited NH4 removal capacity and cannot be easily regenerated when exhausted therefore, synthetic ion-exchange resins have been proposed for NH4 removal [79],... 

Several preanalytical factors can cause a false elevation of the measured plasma ammonium concentration. These include prolonged tourniquet application, hemolysis, specimen transportation at room temperature, delay in plasma separation, and even ambient ammonium from cleaning agents or cigarette smoke. These fac-... 

Consideration of other plasma amino acids also informs the diagnosis of inborn errors of urea synthesis. The plasma concentrations of glutamine and alanine are often elevated in parallel with or prior to the ammonium concentration as they act as a nitrogen buffer. Plasma arginine concentrations are low since the only synthetic route for arginine in humans is via the urea cycle. In contrast, the arginine concentration is elevated in ARG-1 deficiency. Hyperornithinemia and homocitrullinuria are the characteristic features of the hyperammonemia, hyperornithinemia, and homocitrullinuria (HHH) syndrome caused by a defect in the ornithine transporter (ORNT-1). 

Using BDD anodes and MIO cathodes, enrichment of ammonia was also observed - in contradistinction to other studies using higher ammonium concentration and an Ir02 anode (Kim et al. 2005). In the combination of BDD anode/BDD cathode, nitrite was oxidised but only relatively slowly. When nitrate was electrolysed, its depletion was lower than 1 ppm for current densities lower than 200 A m-2. An explanation for the relatively low reaction rate between radicals and nitrite is the assumption that ozone or radicals are consumed in faster reactions such as peroxide formation and chlorine oxidation. OH radicals are also able to oxidise chloramines (Huie et al. 2005). 

It should be noted that a large fraction of the ammonia that is converted to urea in the liver comes from metabolism in the extrahepatic tissues, though only a small fraction leaves these tissues as ammonia. The absorptive cells of the small intestine are exceptional in that they release ammonia into the portal vein there the ammonium concentration may reach 0.26 mmol L-1, accounting for 30 percent of the urea synthesized in the liver. The flow of nitrogen compounds to the liver where urea is synthesized is shown in Fig. 15-12. 

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