Dissolved organic nitrogen

Total dissolved nitrogen/dissolved organic nitrogen analysis 1226... 

Ammonia may be estimated by dissolving the gas in a known volume of standard acid and then back-titrating the excess acid. In a method widely used for the determination of basic nitrogen in organic substances (the Kjeldahl method), the nitrogenous material is converted into ammonium sulphate by heating with concentrated sulphuric acid. The ammonia is then driven off by the action of alkali and absorbed in standard acid. 

Hedges, J. I. and Lee, C. (1993). Measurement of dissolved organic carbon and nitrogen in natural waters. Mar. Chem. 41, 290pp. 

McCarthy, M., Pratum, T., Hedges, J. and Bermer, R. (1997). Chemical composition of dissolved organic nitrogen in the ocean. Nature 390,150-154. 

Jackson, G. A. and Williams, P. M. (1985). Importance of dissolved organic nitrogen and phosphorus in biological nutrient cycling. Deep Sea Res. 32, 223-235. 

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...

Yano Y, McDowell WH, Aber JD (2000) Biodegradable dissolved organic carbon in forest soil solution and effects of chronic nitrogen deposition. Soil Biol Biochem 32 1743-1751... 

Dissolved Organic Nitrogen is Commonly Determined in Four Stages ... 

Shepherd and Davies [26] have described a semiautomated version of the alkaline peroxodisulfate procedure for the determination of total dissolved organic nitrogen in seawater. These workers carried out experiments on a range of contaminated and clean seawaters using a version [27] of Koroleff s [24] alkaline peroxodisulfate oxidation technique. 

The ability to make analytical measurements depends intimately on the availability of well-defined standards and calibrants. Many measurements of analytes in seawater (such as dissolved organic carbon and dissolved organic nitrogen) cannot be compared among laboratories because of the lack of appropriate reference materials and blanks for instrument calibration and testing. Intercomparison exercises are critical (NRC, 1993, p. 75). 

Ammonification The microbial process by which dissolved organic nitrogen is converted to ammonium. 

DON, dissolved organic nitrogen The fraction of the organic nitrogen pool in seawater that is dissolved. 

Kaiser, K. Zech, W. (2000a) Sorption of dissolved organic nitrogen by acid subsoil horizons and individual mineral phases. Fur. J. Soil Sci. 51 403-411... 

Generally, N03 dominates over NH4+ at sites close to emission sources (8,12). Dissolved organic nitrogen (DON) concentrations are highly variable in precipitation but often amount to 25-50% of inorganic N deposition (8, 12-14). In some areas, DON can occur in greater concentrations than the inorganic species (15). 

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