RAIN SCAVENGING OF PARTICULATES

摘要

The process of collection of particles by falling raindrops is dis¬cussed in detail, and related to the flow field of air about a raindrop, as inferred from the literature. An extensive literature review treats the theoretical predictions of collection efficiencies, and the contributions to collection by both the wake of the drops and by electrical charges. The present state of knowledge of scavenging by impaction in then summarized.nFollowing this introductory material, a field experimental design is given. Special samplers which utilize water-sensitive paper to record individual drops and their particulate content are described and pictured. Several experiments were conducted using artificial rain in the outdoors with zinc sulfide tracer particles. The measured efficiencies obtained therefrom are presented as functions of drop and particle size, and as functions of the dimensionless impaction parameter, K. Comparisons are made to the theoretical predictions of Langmuir, and to the mea¬surements with freely falling drops made by Kinzer and Cobb, Walton and Woolcock, and McCully, et al.