e plutonium from contaminated environmental surfaces at Rocky Flats (Sehmel and Lloyd, 1976a), e fallout particles in forest fire smoke (Sehmel and Orgill, 1976), « controlled inert tracer particles from selected surfaces on the Hanford reservation (Sehmel and Lloyd, 1976b; Sehmel, 1973a; Sehmel, 1976), and e soil particles from ground surfaces, also at Hanford (Sehmel, 1975a). Most of the wind-caused resuspension research concerns resuspension from vegetated areas. Experiments concerning local resuspension caused by mechanical activity include tracer studies of resuspension rates for a man walking across an asphalt strip and for cars and trucks driven on asphalt HIGH VOLUME SAMPLER SYSTEM SUPPORT ARM or cheat grass. Two different resuspension rates are used, boom) CASCADE IMPACTOR For wind-caused resuspension, resuspension rates are reported as the fraction of particles resuspended/sec. Thus, the total wind-caused resuspension is a product of the surface con- | SPINDLE EXTENSION tamination area, the surface contamination tevel, the duration of resuspen- sion, and the resuspension rate. For mechanical disturbances by vehicular or pedestrian traffic, resuspension was measured each time a car, 3/4-ton truck, or person passed across the length of a 3-m-wide, tracer-contaminated area. Thus traffic resuspension rates are reported as the fraction of particles resuspended/pass. PARTICLES Resuspenston was measured for several types of particles. The particle size distribution of plutonium on the soils at Rocky Flats was uncontrolled since the original release was unplanned. A forest spray operation provided an opportunity to measure resuspension of DDT as tracer particles not specifically controlled for size. The controlled, inert tracer particles used were submicrometer CaMo0q particles and ZnS particles with an 8-ym mass aero- dynamic equivalent.diameter. WIND ORIENTATION TAIL FIN wine t— CYLINDRICAL SAMPLE INLET CYLINDRICAL COWL BODY SPINDLE BEARING ASSEMBLY BOLT AIR SAMPLERS Airborne resuspended particles were either sampled with total air samplers or sized while airborne with particle cascade impactors. Particle cascade impactors were used for plutonium and CaMoOg particles. FIGURE 1. Rotating Cowl and Impactor The particle cascade impactor (@) for sampling respirable particles was attached to a rotating cowl, allowing simultaneous sampling of larger nonrespirable particles. The cowl-impactor system is shown in Figure 1 (Sehmel, 1973b). Particles entering the 15-cm-dia cylindrical sampler (a) Anderson 2000, Inc., Model 65-100 High-Volume Sampler Head, P. 0. Box 20769, AMF, Atlanta, Georgia 30302. 184 185 WIND DIRECTION SENSITIVE ROTATING COWL