266 Health Physics August 2010, Volume 99, Number 2 82°E 86°E T q Trajectory Start Heights 1km —a— 3km —G5km —@— 53°N - 7km —O— 9km —A— Russia 51°N Kazakhstan 49°N - TB°E 82° E 86° E Fig. 6. HYPSLIT air mass trajectories illustrating wind shear derived from archival meteorological data that were inconsistent with reported actual weather conditions at the Semipalatinsk Test Site at time of detonation. Symbols are plotted in 1 h intervals. The wind shear resulted in different sized particles depositing in the vicinity of Dolon over a wider area (Fig. 5) than indicated by retrospective soil sample analyses. Table 9. Comparison of HYSPLIT predicted peak '*’Cs deposition density using three different particle size distributions with decay corrected measurements of Yamamotoet al. (2008). HYSPLIT prediction at Measurements of '°’Cs from Yamamotoetal. Distribution HYSPLIT-predicted maximum (kBg m~°) location of Yamamotoetal. (2008) axis (kBq m~*) (2008) at axis (kBq m~’) Ratio: Yamamoto data to HYSPLIT MI(from Table 1) 2.2 Alternate #1 Alternate #2 3.4 1.4 0.5 1.6 0.8 12-16 12-16 12-16 24 to 32 7 to 10 15 to 20 centerline of the Yamamoto et al. (2008) pattern. This could account for a broadening of our predictions. It should also be noted, however, that the Yamamotoet al. (2008) soil sample data were obtained almost a half century after the test and may notaccurately reflect the original deposition pattern because of weathering and redistribution. The Yamamoto measurementdata exhibit significant scatter and many of the samples were taken over bare soil where those processes could have been particularly important. This is particularly true for the samples taken in Dolonitself. Thus, the true width of the original '*’Cs deposition pattern may lie somewhere between that predicted by the contemporary soil measurements and that predicted by the HYSPLIT model. The HYSPLITsimulationsreflect, at least, the same order of magnitude of the peak '°’Cs deposition density in the vicinity of Dolon, taking into account the dilution of the HYSPLIT maximum deposition density as a result of the additional dispersion of the fallout about the axis. They also illustrate the impact of fractionation on the relative deposition density of volatile nuclides such as "Cs (i.e., deposition of small particles) compared to refractory elements such as ~*’**°Pu (i.e., deposition of large particles). As illustrated in Yamamotoet al. (2008), the soil data clearly show a different dispersion (pattern width) about the fallout pattern centerline for ~*’”*°Pu as opposedto '°’Cs, as expected since the **”*°Pu is mostly on large particles. The pattern of particle size and '’’Cs deposition indicated by the HYSPLIT modelis qualitatively consistent with that expected from highly fractionated local fallout (see companion paperby Ibrahim etal. 2010).