European wet deposition maps based on measurements

Measurement based maps can also be used to validate the long-range transport models. In this report concentration and wet deposition maps of non-marine sulphate, nitrate, ammonium, hydrogen, sodium, chloride, magnesium, potassium and calcium are presented. These components are mapped on a 50×50 km scale over Europe for 1989, based on field measurements made at approximately 750 locations. Point observations are interpolated over Europe using 'kriging'. The patterns observed in the maps agree well with what would be expected from prior knowledge of European emission and climate patterns.

High sulphate deposition is observed in the border area between Germany, Poland and the Czech Republic, and Ukraine and former Yugoslavia, while nitrate deposition is highest in a zone ranging from southern Scandinavia to northern Italy. Ammonium fluxes are largest in Central Europe. The influence of salt water bodies is evident for sodium, chloride and magnesium. Large calcium fluxes are found in southeast Europe. From an extensive uncertainty analysis to assess the quality of the maps uncertainty was estimated to amount approximately 60% for an average 50x50 km grid cell in Europe. Comparison of sulphate, nitrate and ammonium wet deposition with fluxes calculated by the EMEP long-range transport model revealed fluxes obtained in this study to be larger, i.e. on average 75% for sulphate, 20% for nitrate and 55% for ammonium.