Biogeochemical Flows: Nitrogen

Planetary Boundary

  • Global boundary: 62 Tg N/year
  • Source: *Steffen, W., K. Richardson, J. Rockström, S.E. Cornell, et.al. 2015. Planetary boundaries: Guiding human development on a changing planet. Science 347: 736, 1259855
  • Overall, the fixation of nitrogen through Haber–Bosch (120 Tg N yr−1) in 2010 was double the natural terrestrial sources of Nr (63 Tg N yr−1).
  • The overall magnitude of anthropogenic relative to natural sources of fixed nitrogen (210 Tg N yr−1 anthropogenic and 203 Tg N yr−1natural) is so large it has doubled the global cycling of nitrogen over the last century. 
  • The overall magnitude of anthropogenic relative to natural sources of fixed nitrogen (210 Tg N yr−1 anthropogenic and 203 Tg N yr−1 natural) is so large it has doubled the global cycling of nitrogen over the last century.
  • Source: Fowler, et al., The global nitrogen cycle in the twenty-first century, Philos Trans R Soc Lond B Biol Sci. 2013 Jul 5; 368(1621): 20130164.

Significance

The supply of Nr–reactive nitrogen (NH3, NH4, NO, NO2, HNO3, N20, HONO, PAN and other organic N compounds) is essential for all life forms, and increases in nitrogen supply have been exploited in agriculture to increase the yield of crops and provide food for the growing global human population. It has been estimated that almost half of the human population at the beginning of the twenty-first century depends on fertilizer N for their food. (Source: Fowler, et al.)

As nitrogen is a major nutrient, changes in its supply influence the productivity of ecosystems and change the competition between species and biological diversity. Nitrogen compounds as precursors of tropospheric ozone and atmospheric particulate material also degrade air quality. Their effects include increases in human mortality, effects on terrestrial ecosystems and contribute to the radiative forcing of global and regional climate. (Source: Lee, et al., see figure below)


Global N budget. Numbers represent global land N storage in TgN or annual N exchange fluxes in TgN yr−1 for contemporary (1991–2005 average) and preindustrial (1831–1860 average in parenthesis) times. See notes for this figure and the table below in:  Lee, et al., Prominence of the tropics in the recent rise of global nitrogen pollution.  Nature Communications (2019)10:1437 https://doi.org/10.1038/s41467-019-09468-4  and Supplementary Table 1 (modified below) and Supplementary Note 1 (https://doi.org/10.1038/s41467- 019-09468-4.)
Nitrogen Stores & Fluxes Published Estimates 1990’s Published Estimates 2000’s
Biological N Fixation 112; 139  
Agricultural 32 50-70
Preindustrial 58; 195  
Non-agricultural NA  
Natural 107; 128  
     
Atmospheric Deposition 59  
     
Haber-Bosch (Synthetic fetilizers) 100 120
     
Fluxes to the ocean 48 45
     
Fluxes to the atmosphere 189  
Denitrification N2 115 96
Other emissions 74 70
     
Fluxes to the land storage 60 27
     
Soils/litter storage 95,000  
     
Fluxes:  TgN/year    
Storage:  TgN    
Source: https://sedac.ciesin.columbia.edu/data/set/ferman-v1-nitrogen-fertilizer-application/maps

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