In Row B, the activity for each size fraction is corrected for percent weight contributed by that fraction. off to the nearest whole number. The values have been rounded The sums of the activity of Samples 6A, 6B, and 6C are 353, 129, and 189 dpm/g of soil, respectively. These values may be compared with 296, 136, and 145 dpm/g, which are the concentrations based on analysis of the total soil. values of the analyses are 324, 132, The mean and 166 dpm/g, and the largest standard deviation is 18% for Sample €C. Row C shows the percentage contribution of each size fraction to the total soil activity. The highest contributor is the 53-20 um size fraction. Vegetated Versus Nonvegetated Areas Formations of sandy mounds at the base of desert shrubbery are common at NTS. One characteristic of these mounds is that the portable field survey instrument (FIDLER) | records a higher activity level over a mound than over the surrounding bare soil. Site 2 of the north-south transect (Fig. The sample taken near 1) was no different. Over the mound, the reading was 35,000 counts per minute (cpm); over the bare soil, it was 25,000 cpm. cm depth. A noticeable feature was the uniform texture of the sandy The samples taken represented the 0-5 mound in contrast to the more gravelly nature of the bare nonvegetated soil. Analysis of the gravel content showed that the bare soil contained 19.5% gravel by weight of total soil; the mound soil contained 2.7% gravel by weight of total soil. The particle size distribution is given in Table 3. Note that the percentage distribution is based on the less than 2-mm particles, which excludes the gravel content. samples is almost equal (88%); The total sand content of the two the mound sample shows a high fine sand (53-250 um) content as compared with the bare soil. The plutonium content, also shown in Table 3, is highest in the medium and in the coarse silt sizes (5-53 um). Corrected for the relative abundance of these particle sizes, the medium and coarse silt sizes contribute 66% in the bare soil and 81% in the mound soil; is in the coarse silt size. in the latter case, 75% The activity is 3,800 and 2,573 dpm/g in the bare and mound soils, respectively. 11 Analyses of 10-g soil samples