Nitrogen riverine export

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... 

Figure 36.5 Comparison of global estimates of total riverine N export (Tg N year ) during the early to mid 1990 s from studies reported in the literature. Note that these estimates include loadings to inland regions that don t reach the oceans in addition to the coastal loadings. For the Boyer et al. study, riverine nitrogen flows to the coasts represent 80% of the total global riverine nitrogen fluxes. Modified from Boyer et al. (2006).

Figure 36.10 Comparison of anthropogenic nitrogen inputs and associated riverine N exports (kg per km of watershed area per year) in two contrasting water regions of the USA The northeast USA and the Mississippi River hasin. Modified from NRC (2000) based on data from Howarth et al. (1996).

Boyer E. W., Goodale C. L., JaworsM N. A., and Howarth R. W. (2002) Anthropogenic nitrogen sources and relationships to riverine nitrogen export in the Northeastern USA. Biogeo-chemical 57, 137—169. 

Boyer, E.W., Goodale, C.L., Jaworski, N.A. and Howarth R.W. (2002). Effects of anthropogenic nitrogen loading on riverine nitrogen export in the northeastern US. Biogeochemistry, 57 58, 137-169. 

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