The dry deposition of gaseous and participate nitrogen compounds to a spruce stand

The dry deposition of particle-bound NH₄ ⁺ and NO₃ ^– and of gaseous NH₃ and HNO₃ to a 45 year old Norway Spruce forest was determined by the inferential method. Deposition velocities were calculated from meteorological data and plant morphology by a multi-layer model which combines the transfer of the trace substances within the canopy and their absorption probabilities due to a variety of deposition mechanisms. For gaseous deposition the same mathematical concept was adopted as for particles. That means that this approach is an alternative to the common concept of resistance analogy. The mean deposition velocities found were 0.47 cm s^–1 for NH₄ ⁺ and 1.85 cm s^–1 for NO₃ ^–. While these values are in the range found in other studies, the mean deposition velocities for the gases were quite large. For NH₃ 13 cm s^–1 were found and for HNO₃ 11 cm s^–1. It is suggested that the absorption of these gases on the plant surfaces is not as effective as assumed in the model.