showed 3,907 and 2,677 dpm/g, respectively. are taken into account, If the gravel contents the values are reduced by 2.7% for the mound samples and by 19.5% in the bare soil. The analyses show that the bare soil contains a slightly higher plutonium content even though the field readings showed the reverse situation. These findings of plutonium association with particle size contrast with earlier studies of mound and bare soil samples (Tamura, 1975a). There, from Area 5 (GMX) the coarse silt in the mound samples contri- buted only about 11% of the activity as compared with 75% in the sample from Area 13. About 75% of the activity from the mound in GMX was in the coarser sand fractions. The likely explanation for the difference is the distance from GZ of the samples; at GMX, the distance was 250 ft; and at Area 13, 590 ft. At GMX, particles of coarse silt and larger sizes in the surrounding soil contributed 947% of the activity; at Area 13, the same particles contributed about 74%. Since closer distance to GZ would permit larger particles to be deposited, the difference in the bare soil and mound may be ascribed to this difference in source term, To date, particle size segregations have been made without benefit of any dispersive treatment. In order to evaluate differences in par- ticle size distribution and possible differences in plutonium distribution, the samples of bare soil and mound were given 5 min of ultrasonic treatment. Table 4, The results of this treatment are given in By comparing results in Tables 3 and 4, the notable feature of the size distribution is the reduction in sand content and the increase in silt and clay. Overall, the plutonium concentration in the respective size fractions was not greatly different in the bare soil. In the mound sample, the plutonium concentration in the size fractions appears tohave decreased; this would suggest that the particles being contributed by the coarser fractions to the finer silt and clay were not highly contaminated particles and, thus, these particles proportionately changed the concentration in the different Size fractions. The effect of the ultrasonic treatment on the plutonium distribution in the soil is that the contribution from the sand fractions decreased and the silt and clay fractions increased. The largest increase in 13