Dissolved organic nitrogen sources

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). 

The major objective of this chapter is to examine and synthesize the published literature with respect to sources and production of terrestrially derived DOC, its relationship with dissolved organic nitrogen (DON), and the mechanistic controls on their export from terrestrial ecosystems to surface waters. With the exception of wet precipitation (which is ranked by continental landmass), we have classified data for throughfall and soil solution under biome type. Where possible, we have shown mean and standard deviations of some biomes to illustrate the amount of variance within and between biomes. Relationships between DOC and DON are illustrated using only those studies that report both DOC and DON concentration. Because most research on DOC and DON has been accomplished in relatively undisturbed areas, particularly forests, this chapter concentrates on the aspect of diffuse-source allochthonous inputs to surface waters and not point-source inputs from urban and agricultural areas. Recent work by Westerhoff and Anning (2000), however, indicates that more research on effluent or point-source DOC as a contributor to riverine allochthonous inputs may be... 

Here we present one example to illustrate the utility of 15N for providing information about the source of dissolved organic nitrogen in a freshwater ecosystem. The 15N contents of fulvic acid fractions of different size varied slightly and were similar to the value for the 15N content of the synfulvic acid fraction in a eutrophic coastal pond in Antarctica (Table I) (Brown et al., 2002). Continuous production of mucilage by the chlorophyte population in the pond and diffusion of DOM from the sediments are the two main DOM sources these data suggest that the same source predominates for all of these fulvic acid fractions. 

McCarthy, M. D., Benner, R., Lee, C., Hedges, J. I., and Fogel, M. L. (2004). Amino acid carbon isotopic fractionation patterns in oceanic dissolved organic matter An unaltered photoautotrophic source for dissolved organic nitrogen in the ocean Marine Chemistry 92(1-4), 123-134. 

Wong, C. S., Yu, Z., Waser, N. A. D., Whimey, F. A., andjohnson, W. K. (2002). Seasonal changes in the distribution of dissolved organic nitrogen in coastal and open-ocean waters in the North East Pacific sources and sinks. Deep-Sea Research II 49(24—25), 5759—5773. 

Aitkenhead-Peterson, J. A. 2000. Source, production and export of dissolved organic carbon and nitrogen. Ph.D. Dissertation, University of New Hampshire. 

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