Background and fingerprint characteristics of anthropogenic 236U and137Cs in soil and road dust samples collected from Beijing and Zhangjiakou, China

U-236 has attracted more attention as an environmental tracer in recent years. However, in-depth study of U-236 in terrestrial environments is still rare in China. Data on U-236 and Cs-137 concentrations in soil and road dust samples collected from Beijing and Zhangjiakou, China were obtained to demonstrate the background and distinct characteristics of anthropogenic U-236 and Cs-137. U-236 and Cs-137 were detected in the range of (1.10-7.90) x 10(7) atoms g(-1) and below the method limits of detection to 5.30 Bq kg(-1). A clear characteristic was observed in road dust, where U-236 concentrations increased with decreasing of sample particle size. Soil samples showed an irregular characteristic, but the highest U-236 concentrations were observed in particle size fraction of <0.053 mm in both samples. This phenomenon was caused by U chemical properties, higher specific surface areas and organic compounds in fine particles. Anthropogenic radionuclides fingerprint characteristics in <0.053 mm samples were specially discussed. U-236/U-238 atom ratios were detected in the range of (0.627-3.38) x 10(-8). A weak correlation between anthropogenic U-236 and natural U isotopes were observed. The intermediate correlation between U-236 and Cs-137 indicated somewhat distinct migration behavior of these two radionuclides in soil after release to the environment. The released amount of U-236 from global fallout during the period of atmospheric nuclear weapons testing was roughly estimated to be 1300 +/- 448 kg. These results could be used as fingerprint information for anthropogenic U-236 migration behavior and tracer application in environment. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The study focused on the measurement of U-236 and Cs-137 in soil and road dust samples from Beijing and Zhangjiakou in China, demonstrating varying concentration characteristics and migration behaviors of U-236 and Cs-137 in different samples. A pattern of increasing U-236 concentrations with decreasing particle size was observed in some samples, while others exhibited irregular characteristics.