Exploration of the potential application of plutonium isotopes in source identification of sandstorm in the atmosphere of Beijing

Plutonium (Pu) is an anthropogenic radionuclide which mainly derived from atmospheric nuclear tests in the environment. In this study, the Pu isotopes (239Pu and 240Pu) in aerosol samples collected during the sandstorm and non-sandstorm period were measured by accelerator mass spectrometry (AMS) and the behavior of Pu was studied. The activity concentrations of 239Pu and 240Pu in the aerosol samples of Beijing were ranged from 0.62 nBq/m3 to 99.6 nBq/m3 for 239Pu and 3.51 nBq/m3 to 60.23 nBq/m3 for 240Pu, respectively. 239Pu and 240Pu concentrations exhibited a remarkable seasonal variation trend, with the higher results showed in spring, and the relatively lower concentrations in winter. The observed higher concentration of 239Pu and 240Pu detected in sandstorm samples further indicated Pu was closely related to the occurrence of sandstorms. The global fallout characteristics of 240Pu/239Pu atom ratios (average 0.20, ranging from 0.16 to 0.27) in aerosol samples indicating that global fallout was the major source of Pu in the atmosphere. Using aluminum (Al) as an indicator of soil resuspension, significant positive correlation between 239Pu and Al (r2 = 0.934), 240Pu and Al (r2 = 0.525) revealed that soil resuspension was a primary source of atmospheric Pu in Beijing. These results implied that the combination of 239Pu, 240Pu and Al could be used as the potential tracer of sandstorm.