The contribution of sedimentation to aerosol deposition to vegetation with a large leaf area index

Abstract

The deposition to vegetative canopies of aerosols of dia. 30 μm and less generally increases with wind speed. This phenomenon is due in part to deposition by impaction, but is also due to more sedimentation to lower leaves of the canopy as a result of enhanced turbulent mixing of the air amongst the foliage. A physical model of deposition by sedimentation alone is derived which shows how the deposition velocity, vg, would be expected to vary with wind speed in the absence of deposition by impaction. The results are compared with experimental observations of deposition of Lycopodium powder to dry and wet vegetation (Chamberlain and Chadwick, 1972). The comparison suggests that for wet vegetation in high wind speeds impaction is a major cause of deposition; but for dry vegetation and for wet vegetation in moderate wind speeds, the rise in vg may be caused mainly by increased sedimentation to lower leaves. © 1980.