Effects and empirical critical loads of nitrogen for ecoregions of the United States
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In: de Vries, W.; Hettelingh, J.-P.; Posch, M., eds. Critical loads and dynamic risk assessment. Dordrecht, The Netherlands: Springer: 129-169. Chapter 5.
Human activity in the last century has led to a significant increase in nitrogen (N) emissions and deposition (Galloway et al. 2004). Total N emissions in the United States have increased significantly since the 1950s (Galloway 1998, Galloway et al. 2003). As S deposition has declined in response to regulation, the rate of N deposition relative to S deposition has increased since the 1980s (Driscoll et al. 2001, 2003) followed by a general decrease in NOx emissions from electric utilities since the early 2000s. More recently, the relative proportion of NHx (NH4+ + NH3 ) to NOx (NO + NO2) emissions has also increased for many areas of the United States (Kelly et al. 2005; Lehmann et al. 2005).
Pardo, Linda H.; Robin-Abbot, Molly J.; Fenn, Mark E.; Goodale, Christine L.; Geiser, Linda H.; Driscoll, Charles T.; Allen, Edith B.; Baron, Jill S.; Bobbink, Roland; Bowman, William D.; Clark, Christopher M.; Emmett, Bridget; Gilliam, Frank S.; Greaver, Tara L.; Hall, Sharon J.; Lilleskov, Erik A.; Liu, Lingli; Lynch, Jason A.; Nadelhoffer, Knute J.; Perakis, Steven J.; Stoddard, John L.; Weathers, Kathleen C.; Dennis, Robin L. 2015. Effects and empirical critical loads of nitrogen for ecoregions of the United States. In: de Vries, W.; Hettelingh, J.-P.; Posch, M., eds. Critical loads and dynamic risk assessment. Dordrecht, The Netherlands: Springer: 129-169. Chapter 5. https://doi.org/10.1007/978-94-017-9508-1_5.