DRY DEPOSITION OF NONSPHERICAL PARTICLES ON NATURAL AND SURROGATE SURFACES

Deposition velocities of prolate and oblate spheroids and dust particl es to a smooth surrogate surface, a surface with microroughness and to a sea surface are obtained by a two-layer model, consisting of consta nt flux layer and deposition layer submodels. The deposition layer mod el includes the mechanism of interception. Interception depends on par ticle shape and aspect ratio. Deposition velocities of nonspherical pa rticles and of the equivalent spheres and the ratio between these velo cities, the ''shape effect ratio,'' were calculated for a range of aer odynamical diameters (0.001 to 100 mu m), particle shapes (particle as pect ratio from 3 to 10), particle density (0.1-10 g/cc), wind speed ( 5-20 m/s), and height of microroughness elements (0-22 mu m). Intercep tion is most significant for particles with large particle aspect rati os depositing to a smooth surface, under conditions of strong turbulen ce. Spray droplets from white caps on a sea surface or microroughness on a land surface reduce the effect of interception. The ''shape effec t ratio'' obtains values larger than 1.10 in the range of aerodynamica l diameters from 0.080 to 42 mu m. For spheroids possessing an aspect ratio equal to 3 (10), the ''shape effect ratio'' is smaller or equal to 2.2 (9.8). For dust particles possessing an aspect ratio of 3, the ''shape effect ratio'' is smaller than or equal to 3.6. (C) 1997 Ameri can Association for Aerosol Research.