miércoles, 27 de marzo de 2019

Presence of fallout 236U and plutonium isotopes, 239Pu and 240Pu, in soils from Southern Hemisphere

236U, 239Pu and 240Pu are present in soils mainly as a result of the local- and global-fallout from the atmospheric nuclear weapons tests carried out mainly in the 1950's and 1960's. In this work we provide new data on the presence of 236U and 239,240Pu in surface soils (i.e. up to 5 cm depth) from Chile and Africa. The results were obtained by low-energy Accelerator Mass Spectrometry (AMS). In the case of the Chilean samples, 236U/239Pu atom ratios show a high variability and are in general higher than the reported value for the global fallout in the Northern Hemisphere, ranging from 0.2 to 1.5. The 236U atomic concentrations range from 3.5 × 106 to 9.1 × 106 atoms/g, and are at least two orders of magnitude lower than the reported values in the Northern Hemisphere. The measured 240Pu/239Pu atom ratio in soils from South-Africa and Mozambique are of about 0.17, in agreement with the expected one for global-fallout at those coordinates. To best knowledge of the authors the present work is the first publication on 236U concentrations and 236U/239Pu atom ratios in soils from South-America and Africa. Read more.