and 137Cs in surface soils which are solely influenced by global fallout. A total of 12 soil
cores from the depths of 0–10, 0–20 and 0–30 cm were collected at a flat forest area in
Japan. Concentrations of 239+ 240Pu and 238U were determined by α-particle
spectrometry, while the 236U/238U ratio was measured with accelerator mass spectrometry
(AMS). Consistent 236U/239Pu ratios between 0.212 and 0.253 were found. Using this ratio …