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| Titel |
Effects of global change during the 21st century on the nitrogen cycle |
| VerfasserIn |
D. Fowler, C. E. Steadman, D. Stevenson, M. Coyle, R. M. Rees, U. M. Skiba, M. A. Sutton, J. N. Cape, A. J. Dore, M. Vieno, D. Simpson, S. Zaehle, B. D. Stocker, M. Rinaldi, M. C. Facchini, C. R. Flechard, E. Nemitz, M. Twigg, J. W. Erisman, K. Butterbach-Bahl, J. N. Galloway |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 24 ; Nr. 15, no. 24 (2015-12-16), S.13849-13893 |
| Datensatznummer |
250120229
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| Publikation (Nr.) |
 copernicus.org/acp-15-13849-2015.pdf |
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| Zusammenfassung |
The global nitrogen (N) cycle at the beginning of the 21st century has
been shown to be strongly influenced by the inputs of reactive nitrogen
(Nr) from human activities, including combustion-related NOx,
industrial and agricultural N fixation, estimated to be 220 Tg N yr−1 in
2010, which is approximately equal to the sum of biological N fixation in
unmanaged terrestrial and marine ecosystems. According to current
projections, changes in climate and land use during the 21st century
will increase both biological and anthropogenic fixation, bringing the total
to approximately 600 Tg N yr−1 by around 2100. The fraction contributed
directly by human activities is unlikely to increase substantially if
increases in nitrogen use efficiency in agriculture are achieved and control
measures on combustion-related emissions implemented.
Some N-cycling processes emerge as particularly sensitive to climate change.
One of the largest responses to climate in the processing of Nr is the
emission to the atmosphere of NH3, which is estimated to increase from
65 Tg N yr−1 in 2008 to 93 Tg N yr−1 in 2100 assuming a change
in global surface temperature of 5 °C in the absence of increased
anthropogenic activity. With changes in emissions in response to increased
demand for animal products the combined effect would be to increase NH3
emissions to 135 Tg N yr−1. Another major change is the effect of
climate changes on aerosol composition and specifically the increased
sublimation of NH4NO3 close to the ground to form HNO3 and
NH3 in a warmer climate, which deposit more rapidly to terrestrial
surfaces than aerosols. Inorganic aerosols over the polluted regions
especially in Europe and North America were dominated by
(NH4)2SO4 in the 1970s to 1980s, and large reductions in
emissions of SO2 have removed most of the SO42− from the
atmosphere in these regions. Inorganic aerosols from anthropogenic emissions
are now dominated by NH4NO3, a volatile aerosol which contributes
substantially to PM10 and human health effects globally as well as
eutrophication and climate effects. The volatility of NH4NO3 and
rapid dry deposition of the vapour phase dissociation products, HNO3 and NH3,
is estimated to be reducing the transport distances,
deposition footprints and inter-country exchange of Nr in these
regions.
There have been important policy initiatives on components of the global N
cycle. These have been regional or country-based and have delivered
substantial reductions of inputs of Nr to sensitive soils, waters and
the atmosphere. To date there have been no attempts to develop a global
strategy to regulate human inputs to the nitrogen cycle. However,
considering the magnitude of global Nr use, potential future increases,
and the very large leakage of Nr in many forms to soils, waters and the
atmosphere, international action is required. Current legislation will not
deliver the scale of reductions globally for recovery from the effects of
Nr deposition on sensitive ecosystems, or a decline in N2O
emissions to the global atmosphere. Such changes would require substantial
improvements in nitrogen use efficiency across the global economy combined
with optimization of transport and food consumption patterns. This would
allow reductions in Nr use, inputs to the atmosphere and deposition to
sensitive ecosystems. Such changes would offer substantial economic and
environmental co-benefits which could help motivate the necessary actions. |
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