[en] Karst and other sensitive aquifers contribute up to 90% to the total drinking water supply in some European regions. However, they are more vulnerable to contamination than other aquifers due to short transfer times from recharge to source. Therefore, the main objective of this paper is to show possibilities to quantify the impact, even small of long distance air pollution on sensitive water resources (e.g. karst) even in relatively pristine and remote areas as the front-range of the Northern Calcareous Alps in Austria. The monthly precipitation (May and September 2005) samples show ¹⁸O-rich nitrate and sulphate ions, whereas the soil nitrate shows variable contribution of atmospheric nitrogen with depth. Sulphate in the soil profile changes in the direction to lower ¹⁸O and higher ³⁴S values with depth. Assuming the values of precipitation and soil for nitrate and precipitation and the dolomite rocks for sulphate and end-members the contribution of atmospheric nitrate and sulphate in the groundwater are estimated in the range of 20-40%. In addition, strontium isotopes support that up to 25% more atmospheric radiogenic Sr is added to the groundwater. Isotope data confirm that considerable amounts of atmospheric pollution is added to sensitive karst-groundwater by preferential flow. (author)