AIRBORNE PLUTONIUM-239 AND AMERICIUM-241 TRANSPORT MEASURED FROM THE 125-M HANFORD METEOROLOGICAL TOWER G. A. Sehmel Battelle Memorial Institute, Pacific Northwest Laboratory Richland, Washington ABSTRACT Airborne plutonium-239 and americium-241 concentrations and fluxes were measured at six heights from 1.9 to 122 m on the Hanford meteorological tower. The data show plutonium-239 was transported on nonrespirable and "small" particles at all heights. Airborne americium-241 concentrations on small particles were maximum at the 9i-m height. INTRODUCTION Studies at Rocky Flats and Hanford have shown that plutonium is resuspended. For the time periods investigated in these studies (Krey et al., 1976; Sehmel, 1977a, 1977b, 1977c, 1978; Sehmel and Lloyd, 1976), airborne plutonium-239 concentrations were above fallout levels but never exceeded 2% of the maximum permissible concentration for individu- als, even in an uncontrolled area. Plutonium was transported on both respirable and nonrespirable particles. In controlled areas, plutonium239 transport occurred to at least a 30-m height. The maximum plume height was unknown and the relative transport on respirable and nonrespirable particles could only be estimated. Americium-241 could also be resuspended from plutonium resuspension sites. Although americium-241 resuspension has been reported at lowlevel waste disposal areas on the Hanford area (Sehmel, 1977b, 1977c), there are few reported data showing airborne americium-241 concentrations. Nevertheless, resuspension of americium-241 could become an inhalation concern a hundred years from now after plutonium-241 has decayed to americium-241. 707