This report provides a summary of an assessment of nitrogen sinks in boreal ecosystems. The mass balances are based on unpolluted parts of the boreal Scandinavia and do not consider vegetation changes of microbiological changes in soil. Empirical thresholds for nitrate leaching are based on European and American data. The key process of N mineralization and nitrification is recommended to be studied in the Athabasca Oil Sands Region, to assess the nitrification potential of the soils and understand the fate of deposited nitrogen.