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| Titel |
Present and future nitrogen deposition to national parks in the United States: critical load exceedances |
| VerfasserIn |
R. A. Ellis, D. J. Jacob, M. P. Sulprizio, L. Zhang, C. D. Holmes, B. A. Schichtel, T. Blett, E. Porter, L. H. Pardo, J. A. Lynch |
| 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 ; 13, no. 17 ; Nr. 13, no. 17 (2013-09-10), S.9083-9095 |
| Datensatznummer |
250085687
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| Publikation (Nr.) |
 copernicus.org/acp-13-9083-2013.pdf |
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| Zusammenfassung |
| National parks in the United States are protected areas wherein the natural
habitat is to be conserved for future generations. Deposition of
anthropogenic nitrogen (N) transported from areas of human activity (fuel
combustion, agriculture) may affect these natural habitats if it exceeds an
ecosystem-dependent critical load (CL). We quantify and interpret the
deposition to Class I US national parks for present-day and future (2050)
conditions using the GEOS-Chem global chemical transport model with
1/2° × 2/3° horizontal resolution over North America. We
estimate CL values in the range 2.5–5 kg N ha−1 yr−1 for the
different parks to protect the most sensitive ecosystem receptors. For
present-day conditions, we find 24 out of 45 parks to be in CL exceedance
and 14 more to be marginally so. Many of these are in remote areas of the
West. Most (40–85%) of the deposition originates from NOx emissions
(fuel combustion). We project future changes in N deposition using
representative concentration pathway (RCP) anthropogenic emission scenarios
for 2050. These feature 52–73% declines in US NOx emissions
relative to present but 19–50% increases in US ammonia (NH3)
emissions. Nitrogen deposition at US national parks then becomes dominated
by domestic NH3 emissions. While deposition decreases in the East
relative to present, there is little progress in the West and increases in
some regions. We find that 17–25 US national parks will have CL exceedances
in 2050 based on the RCP8.5 and RCP2.6 scenarios. Even in total absence of
anthropogenic NOx emissions, 14–18 parks would still have a CL
exceedance. Returning all parks to N deposition below CL by 2050 would
require at least a 50% decrease in US anthropogenic NH3 emissions
relative to RCP-projected 2050 levels. |
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