Mapping Critical Loads for Europe

Bilthoven

1991

200 S.

zahlr. Lit. Ang.

Bandaufführung

60935

The work plan for the implementation of the UN ECE Convention on Long-Range Transboundary Air Pollution includes the production of maps of critical loads, critical levels, and exceedances as a basis for developing potential abatement strategies for sulphur and nitrogen.The Coordination Center for Effects (CCE) was created to assist the United Nations Economic Commission for Europe (UN ECE) in the effects-related work conducted under its Working Groups on Effects and on Abatement Strategies and their subsidiary bodies, particularly the Task Force on Mapping. Since its start in April 1990, the CCE has produced a Mapping Vademecum and held two training sessions in order to obtain consensus among experts involved in the mapping exercise concerning the methods used. The first critical load maps presented in this report have the following characteristics: 1. Application of different methods: The critical loads maps of Europe have in majority been obtained using one method, i.e., the steady state mass balance method. Only 3 of 13 countries which submitted data applied a different method. The application of different methods has not lead to loss of comparability of displayed results. The maps of critical loads of sulphur have been obtained from the critical load map of acidity by applying a fraction computed from actual acid deposition. The maps of critical loads of nitrogen have been obtained by applying the earlier mentioned fraction as well as European data on nitrogen uptake. Therefore the map of critical loads of nitrogen reflects acidifying as well as nutrifying characteristics of nitrogen for forest soils. 2. Application of different data resolutions: European soil data are available for 25 countries. National critical load computations using national data were provided by 13 countries. These 13 countries provided critical loads for surface waters, forest soils or a combination of these ecosystems. The remaining 12 countries were mapped using European data for forest soils. All critical loads data were aggregated to EMEP grid areas (approximately 150km x 150km) by constructing cumulative distributions of critical loads for every EMEP grid cell. 3. Display of critical loads percentiles: 1 and 5 percentile maps of critical loads of acidity, sulphur and nitrogen have been produced. The 1 (or 5) percentile map of critical loads reflects the upper bound of the range of critical loads in each EMEP grid cell which covers 1% (or 5%) of the area in an EMEP grid cell. By choosing a low percentile (i.e., 1 or 5) a large share of sensitive ecosystems, including the most sensitive ones, will be protected. The application of higher percentiles will increase the uncertainty with respect to the area coverage of protected ecosystems. The main reason for the latter is the lack of areal data. 4. Shading of EMEP grid cells: The shading of EMEP grid cells is....