Depositional records of plutonium and 137Cs released from Nagasaki atomic bomb in sediment of Nishiyama reservoir at Nagasaki

In a sediment core of Nishiyama reservoir at Nagasaki city, depth profiles of 240Pu/239Pu isotopic ratio, 239+240Pu and 137Cs activities were determined. Sediments containing plutonium and 137Cs, which were deposited immediately after a detonation of Nagasaki atomic bomb, were identified in the core. Observed below the sediments were macroscopic charcoals, providing evidence for initial deposit of the fallout of the Nagasaki atomic bomb. This is the first entire depositional records of plutonium and 137Cs released from the Nagasaki atomic bomb together with those from atmospheric nuclear tests.