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

The vertical distribution and migration behavior of 239+240Pu in a soil core in northern Loess Plateau in Shaanxi Province was investigated. The results showed that the 239+240Pu activity concentration was in the range of 0.02–0.75 mBq/g. The measured atom ratios of 240Pu/239Pu in the soil profile varied from 0.179 to 0.201 and were consistent with the typical global fallout. The inventory of 239+240Pu was 66 Bq/m2 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 cm2/year by the convection dispersion equation model, respectively. Further investigation is still highly required to clarify the dominant factors that control Pu migration.