Excerpt
Reactive nitrogen (i.e., organic nitrogen and biologically and chemically active forms of inorganic nitrogen) has huge beneficial effects, particularly for humans, but it also has equally disastrous effects for humans (Birch et al. 2011) and for the environment, which sustains our presence on this planet (Moomaw 2002; Galloway et al. 2003). Since World War II, the anthropogenic release of reactive nitrogen to the atmosphere, land, and water has greatly increased (Howarth et al. 2005). This has adversely affected atmospheric visibility, climate, and human health, while at the same time led to the acidification of land and water and eutrophication of fresh and salt water ecosystems (Galloway et al. 2003). As troubling as they appear to be, these effects have not been well documented or quantified. Nitrogen (N) loads to streams and rivers in the Mississippi River Watershed are of particular importance because of hypoxia in the Gulf of Mexico (Rabalais 2002; Rabalais et al. 2002a, 2002b) and the associated ecological and economic consequences (Diaz and Solow 1999). Of the N transported by the Mississippi River and its tributaries, about 60% of the total is in the form of nitrate (NO3) (Goolsby and Battaglin 2000). Both point and non-point sources significantly…
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