Vertical distribution and migration of plutonium in the Loess Plateau, North Shaanxi, China

The vertical distribution and migration behavior of Pu239+240 in a soil core in northern Loess Plateau in Shaanxi Province was investigated. The results showed that the Pu239+240 activity concentration was in the range of 0.02-0.75 mBq/g. The measured atom ratios of Pu-240/Pu-239 in the soil profile varied from 0.179 to 0.201 and were consistent with the typical global fallout. The inventory of Pu239+240 was 66 Bq/m(2) in the sampling site and the proportion of Pu in the first 10 cm top layer accounted for around 75%. The apparent convection velocity and effective dispersion coefficient were 0.19 cm/year and 0.12 cm(2)/year by the convection dispersion equation model, respectively. Further investigation is still highly required to clarify the dominant factors that control Pu migration.