Modelling nitrogen deposition: dry deposition velocities on various land-use types in Switzerland

Abstract

In this study, we analysed nitrogen deposition in Switzerland obtained from a modelling study in Europe for 2006 with the CAMx model. Comparison of modelled ammonia with measurements showed a relatively good agreement for annual concentrations whereas an overestimation was found in spring due to the meteorological conditions prevailing in 2006. The modelled average annual nitrogen deposition of 12.2 kg N ha−1 a−1 in Switzerland was dominated by the deposition of reduced nitrogen compounds (74%) and the largest contribution to nitrogen deposition was from dry deposition of ammonia. Dry deposition velocities of oxidised and reduced nitrogen compounds were calculated for specific land-use types found in Switzerland. The highest annual deposition velocities for ammonia and nitric acid were estimated over evergreen shrubs whereas the deposition was lowest over water surfaces. Deposition velocities over various land surfaces were shown to vary seasonally and the values in spring and summer were higher than in winter by a factor of up to 2.7.