Fisher,L.S., Mays,P.A. and Wylie,C.L.(2007): An overview of nitrogen critical loads for policy makers, stakeholders, and industries in the United States. Water Air Soil Pollut., 179, 3-18.

『米国の政策立案者・ステークホルダー（利害関係者）・産業界に対する窒素臨界負荷量のレビュー』

『Abstract
　Critical load values are calculated to determine ecosystem responses to deposition in a given area; these values may act as a tool to identify sensitive ecosystems in further need of protection. This overview provides an introduction to nitrogen critical loads for policy makers and parties involving in managing nitrogen deposition including electric utility generators, transportation managers and automobile manufacturers, and large-scale agricultural operators in the United States. It examines the use of the critical loads concept in European nations for establishing policy guidelines, current research on nitrogen critical loads in the U.S., and the development of nitrogen critical loads modeling and mapping.

Keywords: chemical criteria limit; critical loads; nitrogen deposition; simple mass balance』

『要旨
　臨界負荷量が、示された地域での沈着量に対する生態系の反応を決定するために計算されている；これらの値は、影響を受けやすい生態系について将来の保護の必要性を確認するための手段としての役割を担うかもしれない。このレビューは、米国の発電業者や運輸管理者や自動車製造業者や大規模農業経営者を含む、窒素沈着を管理すべき政策決定者と組織に対して窒素の臨界負荷量に対する基本を提供するものである。政策指針を確立するためのヨーロッパの諸国家における臨界負荷量の概念の使用のしかた、米国における窒素臨界負荷量についての現在の研究、および窒素臨界負荷のモデル化と図化手法の開発、について検討している。』

1 Introduction
　1.1 Deposition and transportation of nitrogen compounds
2 What are critical loads?
3 European and Canadian development of nitrogen critical loads
4 U.S. research on nitrogen critical loads
　4.1 Nitrogen critical loads research in regions of the U.S.
5 How are critical loads established?
　5.1 Sensitive indicators
　5.2 Chemical criteria and thresholds
　　5.2.1 Acidification in the terrestrial environment
　　5.2.2 Acidification in the aquatic environment
　　5.2.3 Critical loads based on acidity
　5.3 Effects of nutrient-nitrogen enrichment in terrestrial and aquatic environments
6 Regional variation in ecological response for nitrogen critical loads
7 Conclusions
Acknowledgments
References

Table I Select European critical load limits for nutrient-nitrogen established by UNECE Convention on Long-range Transboundary Air Pollution (adapted from Achermann & Bobbink, 2003)
Trees (including coniferous, deciduous, and temperate forest) 15-20 kg N/ha/year
Ground vegetation (temperate and boreal forest) 10-15
Soil processes 10-15
Mycorrhiza (10-20)
Lichens and algae (10-15)
Overall critical values for the: Temperate forest (10-20)
Overall critical values for the: Boreal forest (10-20)

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