MATERIALS AND METHODS Particulate air samplers are run continuously at two perimeter locations and at one off-site location. Collections are made on a polystyrene filter medium. Individual samples are combined by location on a monthly basis to give a typical filtered air volume of about 25,000 m3. Samples are ignited at 600° C. to remove organic matter and prepared for analysis by using a leach procedure employing combinations of hydrochloric, hydrofluoric, and nitric acids. A radiochemical separation procedure is used to sequentially isolate plutonium, thorium, and uranium. After separation, the fractions are electrodeposited and their isotopic composition determined by alpha spectrometry. Chemical recoveries are monitored by added known amounts of plutonium-242, thorium-234, and uranium-232 prior to ignition. The monthly amount of plutonium deposited on the surface from the air is also determined by the above method. Wet and dry deposited material is collected in a container of known area and the residue analyzed for plutonium. Surface soil of known area is analyzed for plutonium, uranium, and thorium. After drying, grinding, and mixing, an aliquot of soil is analyzed by a leach method similar to that used above for the air-filter residues. RESULTS AND DISCUSSION The concentration of plutonium-239,240 in air at ANL (Sedlet et al., 1973, 1974, 1975; Golchert et al., 1976, 1977) for the last five years is depicted in Figure 1. The fluctuations are primarily due to recent atmospheric nuclear tests conducted by the People's Republic of China. The approximate dates of these tests are indicated by arrows at the bottom of the figures. The concentrations in air of other fission products for which measurements were made, t.e., strontium-89, strontium-90, ete., show a similar distribution. Measurements of this type for this period and earlier have been made by the Environmental Measurements Laboratory (EML) (Hardy, 1978), formerly HASL, at various locations. The monthly variations exhibit the expected maximum in the spring and the magnitude of the peak is determined by the quantity and yield of atmospheric testing the previous year. Another way of looking at this type of information is to examine ground deposition of plutonium-239, 240 for the same period. This is illustrated in Figure 2. This data was generated by analyzing the contents of a known area sample collector for plutonium and expressing the results in terms of deposition (pCi/m*). 724