Assessing the Impacts of Long-Range Sulfur and Nitrogen Deposition on Arctic and Sub-Arctic Ecosystems |
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Authors: | Martin Forsius Maximilian Posch Julian Aherne Gert Jan Reinds Jesper Christensen Lars Hole |
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Institution: | 1.Finnish Environment Institute (SYKE),Helsinki,Finland;2.Coordination Centre for Effects (CCE), PBL,Bilthoven,The Netherlands;3.Environmental and Resource Studies,Trent University,Peterborough,Canada;4.Alterra, Wageningen University and Research Centre (WUR),Wageningen,The Netherlands;5.Department of Atmospheric Environment, National Environmental Research Institute,University of Aarhus,Roskilde,Denmark;6.Norwegian Institute for Air Research, Troms? office, Polar Environment Center,Troms?,Norway |
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Abstract: | For more than a decade, anthropogenic sulfur (S) and nitrogen (N) deposition has been identified as a key pollutant in the
Arctic. In this study new critical loads of acidity (S and N) were estimated for terrestrial ecosystems north of 60° latitude
by applying the Simple Mass Balance (SMB) model using two critical chemical criteria (Al/Bc = 1 and ANCle = 0). Critical loads were exceeded in large areas of northern Europe and the Norilsk region in western Siberia during the
1990s, with the more stringent criterion (ANCle = 0) showing the larger area of exceedance. However, modeled deposition estimates indicate that mean concentrations of sulfur
oxides and total S deposition within the Arctic almost halved between 1990 and 2000. The modeled exceeded area is much reduced
when currently agreed emission reductions are applied, and almost disappears under the implementation of maximum technically
feasible reductions by 2020. In northern North America there was no exceedance under any of the deposition scenarios applied.
Modeled N deposition was less than 5 kg ha−1 y−1 almost across the entire study area for all scenarios; and therefore empirical critical loads for the eutrophying impact
of nitrogen are unlikely to be exceeded. The reduction in critical load exceedances is supported by observed improvements
in surface water quality, whereas the observed extensive damage of terrestrial vegetation around the mining and smelter complexes
in the area is mainly caused by direct impacts of air pollution and metals. |
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Keywords: | Arctic Critical loads Exceedance Acidity Nitrogen Modelling |
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