Influence of Calcium Chloride on 90Sr Vertical Migration in Gray Forest Soil

Vertical migration of Sr-90 was studied in gray forest soil in the forest landscape, in the East Ural radioactive trace region (EURT), at various application doses of CaCl2 on the soil surface. The Sr-90 penetration depth along the soil profile depended ambiguously on the time of migration and salt dose in the three dynamic models. Nevertheless, gradual fixation of Sr-90 and consequent migration slowing down over time were the most likely processes. The range of estimates of medians of diffusion parameters in three migration models for all doses of salt was (6.5-115) x 10(-8) cm(2)/s for the five-year period after salt application (eight years after contamination) and (1.7-145) x 10(-8) cm(2)/s for the nine-year period after salt application (12 years after contamination). The range of median estimates of the fixation parameters was (3.5-15) x 10(-9) 1/s (0.11-0.47 1/year) and (5.5-7) x 10(-9) 1/s (0.17-0.22 1/year) for the five- and nine-year periods, respectively. These ranges mainly indicate incomplete fixation of Sr-90 over these periods. The values of the diffusion parameters decreased along with an increase in the distribution coefficient in the first period; no such dependence was observed for the second period.