BATTELLE Dr. Rudolf J. Engelmann NORTHWEST -4- March 12, 1971 The real questions then are firstly, is radioactive particle resuspension by saltation important for longterm tracer translocation, secondly, can particle resuspension be handled within the framework of existing diffusion models, and thirdly and most importantly, do we now need to develop a resuspension model which can be mathematically matched at an interface height which separates upward particle movement by energy from saltation as opposed to particle motion by conventional eddy diffusion. We interpret saltation and surface creep as an important mode of surface translocation of tracer. This interpretation has some support in the aerial surveys of ground level activity after the Schooner test (pp. 21-23, UCRL-50718). The contour of 5X of background activity showed a downwind migration of up to about 9 miles from the 13th to the 20th day. This translocation could not be attributed to particle movement by true suspension, but could have been caused by removal of inert soil from the base cloud which initially covered the tracer. Nevertheless, saltation + surface creep are believed to be the means of translocation since the 5X contour movement occurred over a broad area. Small (<3 um diameter) high density (10 g/cc) 2>®Pu0, can definitely be resuspended to attain a level of 1 meter or higher above the ground. A 3 um particle corresponds to a soil particle of 5 um diameter of density 2 g/cc. Soil particle concentrations measured at the BNW tower (1959) showed that over 2 x 103 par- ticles/ft3 were collected at the 400 foot level. Concentrations at ground level were over 5 x 103 ft73, The question we propose and cannot answer is: "Do these small particles retain their identity as a tracer or does the tracer attach to the soil particle." If the tracer particles were attached to the host sand particle, the large host particle may never (unless wind speeds are very high) present an immediate inhalation hazard. In this case, the problem of inhalation would arise if the tracer were to subsequently detach from the host sand particle. if