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