Dry deposition of particles to a pine plantation |
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| Authors: | R Lorenz C E Murphy Jr |
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| Institution: | (1) E. I. du Pont de Nemours & Co., Savannah River Laboratory, 29808 Aiken, SC, U.S.A. |
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| Abstract: | There has been some controversy concerning the rate of deposition of particles having diameters near 1.0  m to vegetated surfaces. In this size range, the processes of Brownian diffusion and inertial impaction are not effective and deposition to smooth surfaces reaches a minimum. However, most measurements of deposition of micrometer diameter particles to vegetated surfaces indicate a greater deposition than extrapolation of the results from less rough surfaces would suggest. In this study, the aerodynamic profile method was used to estimate deposition to a pine plantation. The deposition velocities were found to be sensitive to the displacement height and the form of the profile stability correction used in the calculations. An analysis of a limited set of Bowen ratio data, collected over the same forest, suggests that the data are reasonably described by using a displacement height of 7.9 m and the stability correction proposed by Raupach (1979).The average deposition velocities, measured over a 9-month period were 0.0043, 0.0078, and 0.0092 m/s for the three diameter classes 0.5\2-1.0, 1.0\2-2.0 and 2.0\2-5.0 \gmm. These deposition velocities are lower than the corresponding aerodynamic conductance for the same periods, indicating that the deposition rate is limited by surface phenomena. Average surface conductances calculated for the three size classes of particles were 0.0060, 0.0141, and 0.0276 m/s, respectively. A multiple regression analysis showed high correlation between deposition velocity and wind speed. No other measured environmental factor or linear combination of factors was significantly correlated with deposition velocity.This paper was prepared in connection with work done under Contract No. DE-AC09-76R00001 with the U.S. Department of Energy. By acceptance of this paper, the publisher and/or recipient acknowledges the U.S. Government's right to retain a nonexclusive, royalty-free license in and to any copyright covering this paper, along with the right to produce and to authorize others to reproduce all or part of the copyrighted paper. |
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