Concentration and characterization of plutonium in soils of Hubei in central China

To study the Pu concentration and isotope ratio distributions present in China, the Pu239+240 total activities and Pu-240/Pu-239 atom ratios in core soil samples from Hubei Province in central China were investigated using Accelerator Mass Spectrometry (AMS). The activities ranged from 0.019 to 0.502 mBq g(-1) and the Pu239+240 inventories of 45 and similar to 55 Bq m(-2) agree well with that expected from global fallout. The Pu-240/Pu-239 atom ratios in the soil ranged from 0.172 to 0.220. The ratios are similar to typical global fallout values. Hence, any close-in fallout contribution from the Chinese nuclear weapons tests, mainly conducted in the 1970s, must have either been negligible or had a similar Pu-240/Pu-239 ratio to that of global fallout. The top 10 cm layer of the soil contributes similar to 90% of the total inventory and the maximum concentrations appeared in the 2-4 cm or 4-6 cm layers. It is suggested that climatic conditions and organic content are the two main factors that affect the vertical migration of plutonium in soil. (C) 2009 Elsevier Ltd. All rights reserved.