Factors influencing NO3 concentrations in rain, stream water, ground water and podzol profiles of eight small catchments in the European Arctic

Levels and regional distribution of NO3 concentrations in rain, stream water, ground water and soil collected in eight small (12-30 km2) catchment- s, located in severely polluted (near Nikel/Zapoljarnij and Monchegorsk, Kola Peninsula, Russia) to nearly pristine (Northern Finland) parts of the European Arctic are discussed. Yearly atmospheric NOx emissions on the Kola Peninsula exceed 24,000 t. Still wet deposition of NO3-N is very low compared to Central Europe. The atmospheric NOx emissions have no detectable regional influence on the NO3 level in rain. The NO3-N pool present in the soil profiles exceeds the annual input from precipitation by a factor of 4-100. Variations of the nitrate content in soil are higher within catchments than between catchments, indicating that NO3-concentrations in soil are rather governed by local site character- istics (water retention capacity and drainage conditions as some of the most important factors) than distance to major emitters. The nitrate concentration in stream and ground water is very low. The disruption of the bio-productive processes and mineralisation of plant debris and soil humus in the most damaged ecosystem result in a significant increase of NO3 concentrations in soils, stream and ground water.