Spatial variation in annual nitrogen deposition in a rural region in Switzerland

We studied the spatial variation in annual nitrogen deposition to the Seeland region of Switzerland by combining (1) mesoscale atmospheric modeling of gaseous dry deposition, (2) wet deposition data measured within the study area as well as published data, and (3) estimates of dry deposition of aerosol particles based on concentration measurements and sedimentation samples from a nearby region. Gaseous dry deposition shows greatest regional variation. Total nitrogen input to this region is in the range of 22–51 kg N ha−1 year−1 (13–42 kg N gaseous dry deposition; 7–8 kg N wet deposition; ≈ 2 kg N dry deposition of aerosol particles). Gaseous dry deposition is dominated by reduced nitrogen components from agricultural sources. The highest nitrogen inputs were found over lakes (51 kg N ha−1 year−1). Our results indicate that current nitrogen loads exceed the nutrient critical loads by several kg N ha−1 year−1 in all nitrogen-sensitive ecosystem types occurring in our 70×50 km2 study area.