A pertinent question which remains unsettled is the variation Jn fallout from place to place in a given locality. A satisfactory oregr: replication has not been possible up to the present time. how Logan, Utah, we did collact replicates from two pastures about one mii apart, The total radiostrontium assay of these soils was ,22 Gd 28 d/min/zm. Retention by Gummed Films of Particulates in oimilated Rain An experiment was designed to measure the rention by of radioactive particulates suspended in raindrops, d films When we f rst began to use gummed sampling media in our fallout studies, field that the activity collected by gummed paper was comparable ducible than the results obtained using trays desimgmed for of the rain water. However, reliable controlled data have previously, The following procedure was adopted: tas 8 demondtrated +0, and more reprs= to co1iecuan no been availabls Normal radioactive debris was simulated by finely divided pilsef irradiated iron having a mass median diameter of 3A. To suspend the iro a few milligrams were added to two liters of distilled water Particle size control over the suspended particulates was obt alutriation of the original suspension. At a given time, 700 at the top of the cylinder was decanted into a sprinkling arr (Figure 5) which provides for continued agitation of the suspe the sample enters a capillary tube from which droplets are perpi fall to the gummed film. Under the conditions reported here, of "rainfall" was 1" per hour. The retention of the gummed fi expressed as the percentage of suspended activity recovered by A cumulative frequency curve of particle size versus time was using Stokes Law (with Cunningham's correction as necessary). curve, and the data on retention at various times, Figure 6 w alculated, From this developed, The retention of the gummed films in these tests was not as high as was expected. This may be because of the heavy rate of simulated Similar tests at lower rainfall rates are being planned out ha yet gotten under way. Experiments to determine the effect of 24 hours of temperature conditions of the gummed papers are given in Table 3. Conditioning at 5° and at 85°C do not appear to significantly influence the retentivity f the films. In order to datermine if the iron was going into solution, s suspensions of various ages were passed through a Millipore fi Essentially 100% of the activity was recovered on the filters,] indicating Nita that solubility is not a factor in the above procedure. anal