As part of the Agreement on Environmental Cooperation between Norway and Poland critical loads of acidity and their exceedance to two lakes in the Polish Tatra Mountains have been calculated after an extensive programme on water chemistry and precipitation. The critical load of acidity is exceeded in Dlugi Staw, one of the two lakes in study. The main diffference between the comparable areas is the great importance of nitrogen deposition in the Tatra Mountains. The nitrogen leaching of Dlugi Staw is about 90% of the incoming nitrogen, i.e. almost all incoming nitrogen is leaving the lake as nitrate, while Zielony Staw is retaining about 50% of the incoming nitrogen. The nitrate leaching in the two Tatra lakes is much higher than the nitrate leaching of high mountain lakes in Norway subjected to similar sulphur and nitrogen deposition. Here, we find maximum leaching values of less than 30 % of the incoming nitrogen. We have no reasonable explanation for this at the present time. To be able to understand this differences, further studies are needed
