PLUTONIUM AND TRACER PARTICLE RESUSPENSION: AN OVERVIEW OF SELECTED BATTELLE-NORTHWEST EXPERIMENTS G. A. Sehmel Battelle, Pacific Northwest Laboratories, Richland, Washington ABSTRACT Plutonium resuspension at Rocky Flats was determined in July 1973, by measuring airborne plutonium as a function of sampling height and of wind speed. The maximum airborne plutonium-239 concentration was 3700 aCi/m>. The maximum plutonium-239 activity per gram of collected airborne soil was 50 pCi/g. Airborne plutonium concentrations were shown to increase as the sixth power of wind speed, but the data were very imprecise. In_measurement of fallout resuspension caused by burning vegetation, the 37Cs concentration in a forest fire smoke plume was 22 times the concen- tration in ambient air. Resuspension rates for a_man walking across a tracer area on an asphalt sur- face ranged from 1 x 1075 to 7 x 10-4 fraction of tracer resuspended/pass. For vehicular traffic driven on a tracer lane, resuspension rates from the asphalt surface ranged from 10-4 to 10-2 fraction resuspended/pass. When the vehicle was driven on the lane adjacent to the tracer lane, resuspension rates were smaller, ranging from 10-5 to 10-3 fraction resuspended/pass. Resuspension rates decreased when the tracer had been on the ground for several days. In comparison to the asphalt surface, vehicle-caused tracer resuspension rates from a cheat grass area were lower, ranging from 10-° to 10-4 fraction resuspended/pass. Wind caused tracer resuspension rates were on the order of 10711 fraction resuspended/sec for nonrespirable particles. Resuspension rates for respirable particles increased as the 4.8th power of wind speed, ranging from 10-11 to 10-7 fraction resuspended/sec. In another study, airborne respi- rable soil concentrations measured as a function of wind speed increased as the 0.6 to 3.2 power of wind speed. 80 181