Fluid mechanical aspects of the pollutant transport to coniferous trees

Forest decline in some parts of Europe gave rise to various environmental studies concerning the intake and uptake of pollutants in the ecosphere. As far as fluid mechanics is concerned, the current interest is centered on flow-induced phenomena, e.g., the flow-enhanced deposition of pollutants to trees. In order to understand better the mechanisms of pollutant dispersion and deposition to trees, wind tunnel experiments carried out with small real coniferous trees and model trees are summarized in this paper. The flow around single trees and tree stands, both in flat terrain and on hillsides, has been analysed. The measurements were performed with a two-component laser Doppler anemometer system installed in an atmospheric boundary-layer wind tunnel. A chemical tracer method based on an ammonia-manganese chloride reaction was applied to visualize the deposition patterns around trees and modeled forest stands.