RESUSPENSION STUDIES ON FALLOUT LEVEL PLUTONIUM N. W. Golchert and J. Sedlet Argonne National Laboratory--Argonne, L[llinois ABSTRACT Plutonium, uranium, and thorium concentrations in air have been measured for several years. Resuspension factors for uranium and thorium have been calculated and compared to those for plutonium. Using the uranium and thorium in air data, the contribution of plutonium in air from stratospheric fallout and from resuspended surface soil can be determined. Comparison of these data to published measurements at the GMX site is made. Plutonium in air particulates as a function of particle size was measured with an Anderson 2000 high-volume cascade impactor and is presented. INTRODUCTION As part of the Argonne National Laboratory (ANL) Environmental Monitoring Program, air particulate samples are collected to monitor for possible airborne releases of radionuclides. The primary interest is to measure plutonium concentrations in air because of its use at the Laboratory and the importance of public interest in this element as an environmental pollutant. Concentrations are compared to available standards of plutonium in air, DOE Manual Chapter 0524, and to the recent EPA proposed guidelines to determine compliance. The primary source of plutonium in air at the present time is from "fallout." It is estimated that about 325 kCi of plutonium was released to the atmosphere from all the nuclear tests. Because of the monthly variations in the concentrations, it is necessary to continuously monitor. In addition, uranium and thorium concentrations are also determined and the relationship of these elements to that of plutonium provides some interesting comparisons, t.@., the determination of inhalation dose. 723