Dissolved organic nitrogen volatilization

The fate of ammonium nitrogen in wetland soils is summarized in Figure 8.25. Ammonification of organic nitrogen results in the release of ammonium into the soil solution, which is readily partitioned into dissolved phase and an adsorbed phase, maintaining a certain level of equilibrium between these two pools. Depending on the conditions found in wetlands, the fate of ammonium in soil solution includes (1) loss via volatilization as ammonia, (2) oxidation of ammonia by nitrifiers,... 

An amount of enzyme preparation equivalent to 900 mg of wet cells was made up to 25 ml with the above potassium phosphate buffer solution. 150 mg (1.15 mmol) of 5-fluorouracil and 1.0 gram of thymidine (4.12 mmol) were dissolved in 15 ml of the above potassium phosphate buffer solution. The mixture was incubated at 37°C for 18 hours. After this time, enzyme action was stopped by the addition of four volumes of acetone and one volume of peroxide-free diethyl ether. The precipitated solids were removed by filtration, and the filtrate was evaporated under nitrogen at reduced pressure until substantially all volatile organic solvent had been removed. About 20 ml of aqueous solution, essentially free of organic solvent, remained. This solution was diluted to 100 ml with distilled water. 

In addition to the volatile organic compounds found in water, ammonia is an inorganic compound that may occur in drinking water supplies and is frequently present in waste-waters. Ammonia nitrogen exists in both the dissolved gas form (NH3) and in true solution (NHp. These two species are present in a dynamic equilibrium according to the equation ... 

It is essential to preserve the integrity of the sample between the time of collection and the time of analysis. There are, however, several processes that can cause changes in the chemical composition. Examples of these include biodegradation (e.g., of nitrogen- and phosphorus-containing compounds), oxidation (e.g., of Fe(II) and organic compounds), absorption (e.g., of CO2 which affects pFl and alkalinity), precipitation (e.g., removal of CaC03, Al(OH)3), volatilization (e.g., loss of NH3, HCN), and adsorption (e.g., of dissolved metals on the walls of the container). 

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