Distribution and migration characteristics of Cs, Pu, and natural radioactive nuclides in the soil of Leye Tiankeng, China.

To investigate the distribution characteristics of radioactive nuclides in the soil of typical karst Tiankeng areas, two soil core samples and thirty surface soil samples were collected from the Leye Tiankeng Group, northwest Guangxi province in China. The soil's vertical distribution of U, Th, Ra, and K is uniform. Furthermore, the distribution trends of U, Th, and Ra in the surface soil are similar. The activity range of Pu and Cs in surface samples was 0.037 ± 0.008 to 1.680 ± 0.037 Bq/kg and 0.86 ± 0.09 to 17.25 ± 0.38 Bq/kg, respectively. The specific activity ranges of Cs in two core samples were 0.12-4.36 Bq/kg and 0.29-4.76 Bq/kg, respectively, while those of Pu in core samples were 0.001-0.321 Bq/kg and 0.004-0.390 Bq/kg, respectively. The atomic ratios of Pu/Pu and the activity ratios of Cs/Pu both indicate that the artificial radioactive nuclides in this region originated from atmospheric fallout. The sedimentation rates derived from the distribution curve of Pb and distribution of Cs and Pu in soil exhibit considerable parallel. The distribution of Pu and Cs in soil exhibits a high degree of similarity, and the deviations are mainly attributed to the influence of the physical and chemical properties of the soil. Finally, the distribution of two nuclides, Pu and Cs, in the research region after 100 years was predicted using the CDE model.