Multi-effect critical loads used in multi-pollutant reduction agreements in Europe

The scientific support of negotiations on emission reductions under the fra mework of the Convention on Long-range Transboundary Air Pollution of the U N Economic Commission for Europe has been based during the last decade on t he integrated assessment of sources, including abatement costs, and risks t o receptors (e.g. forests, lakes) quantified by critical loads. The shift f rom a single-pollutant (sulfur) protocol in 1994 to a multi-pollutant proto col in 1999 necessitated an extension of the methods by which critical load s were computed and mapped. Instead of a single critical load for acidifica tion, methods were now developed to assess the risk of acidifying effects o f both sulfur and nitrogen deposition as well as the eutrophying effects of nitrogen on sensitive elements of the environment. Collaboration with a sc ientific network of 24 national institutions ensured a successful implement ation of the proposed methodology across countries. This paper summarizes t he methodology, describes the latest input data and presents critical load maps on the basis of which about 98% and 78% of European ecosystems would b e protected against acidification and eutrophication, respectively, by the year 2010 according to the multi-pollutant multi-effect protocol.