MODELING THE DRY DEPOSITION VELOCITY OF AEROSOL-PARTICLES TO A SPRUCE FOREST

A mathematical model is presented to calculate the size-specific deposition velocity of aerosol particles to coniferous forests, taking into account the plant morphology and micrometeorological parameters. In contrast to former studies on this topic the diffusion of the particles through laminar sublayers surrounding the plant surfaces was considered in detail. This necessitated the introduction of a formulation of the microscale roughness of the needle surfaces. Furthermore, the ability of bursts in the sublayer to accelerate the particle transport was included. In order to calculate the overall deposition velocity the canopy was subdivided into a variable number of homogeneous height intervals. An analytical solution of the mass transfer equations containing the measured parameters was applied to each interval. The calculation scheme was then based on an initial value approach. The input parameters were the vertical profiles of wind speed and temperature and the height-specific vegetation density. The model was applied to a Teal spruce stand (Picea abies (L.) Karst.), and some typical results are presented. Finally, errors associated with inhomogeneities of the terrain are discussed.