Natural radioactivity of surface sediments by source regions of the asian dust

Radioactivity of naturally occurring radioactive nuclides (NORN) such as Ra-226, Ac-228 and K-40 were investigated for surface sediments collected from Ordos, Alashan, Taklimakan deserts and Loess plateau regions in China. By a Gamma-ray spectrometry, specific activity (SA) and SA ratio (SAR) of the NORN were determined for each source region of Asian dust. Characterization of the source regions of Asian dust was performed with the SA and SAR values. SA of Ra-226 in the three desert regions have almost same values in the range of mean value 17.9 similar to 21.9 Bq/kg, however, the SA in Loess Plateau has much higher values in the mean value of 35 Bq/Kg. SA of Ac-228 in the Ordos and Alashan desert regions have almost same values in the range of mean value 27.1 similar to 27.2 Bq/kg, and those in Taklimakan desert and Loess Plateau were 31.7 and 49.0 Bq/kg, respectively. In case of 40 K, the SA in all regions have similar values in the range of 636 similar to 943 Bq/kg. The mean SAR value of (226) Ra/Ac-228 in four source regions was almost same in the range of 0.708-0.721. It is shown that relationship between Ra-226 and 228 Ac is clearly presented in the source regions. The mean SAR values of Ra-226/(40) K, Ac-228/K-40 are 0.0209-0.056, 0.0287-0.0773, respectively.