Plutonium Isotopes in Soils Across China : Level, Regional Distribution and Sources

Plutonium isotopes are artificial radionuclides in the environment, which have drawn significant attentions due to its high radiotoxicity and the possibility of sources linked with nuclear accidents in recent years. The level, regional distribution, sources and transport pathway of plutonium (239Pu, 240Pu) in soils of China are summarized and discussed in this study. A database of plutonium activity concentrations, isotopic ratios, and inventories in soils across China is established. The 239,240Pu activities in 500 surface soil samples ranged from 0.002 mBq/g to 4.824 mBq/g, lying in the range of the reported results in the countries with similar latitude. The distribution of 239,240Pu in soils across China is influenced by organic matter and particle size and so on. Most of the 240Pu/239Pu atom ratios (>76%) and average 240Pu/239Pu atom ratios (0.183±0.002) for all soil samples were comparable to the ratio in the global fallout (0.180), indicated that global fallout is the major source of plutonium in China. However, results also demonstrated that the inventory of 239,240Pu and isotopic composition in soils in Northwest China were obviously different with other regions, indicate that a portion of radionuclides in Northwest China were originated from Lop Nor Chinese Nuclear Testing site (CNTs) or Semipalatinsk Nuclear Testing site (SNTs). The nuclear debris released from Nuclear Testing sites were transported by the west and northwest wind, and were affects by topography and terrain to a certain extent. The analytical results could be used as the baseline data for the assessment of the impact of nuclear activities in the past and the future