Evidence for bismuth-207 in global fallout

Samples of lichen, moss, soil and air collected since 1961 in Greenland, Svalbard, Iceland, the Faroe Islands, Sweden and Denmark have been remeasured for γ-emitting radionuclides by Ge(Li) spectroscopy. The samples have shown the presence of ²⁰⁷Bi (physical half-life 38 years), a nuclide which has not been reported earlier in world-wide fallout. The concentrations of ²⁰⁷Bi have been compared with those of ⁶⁰Co, ¹²⁵Sb, and ¹³⁷Cs. From this comparison the production of ²⁰⁷Bi is estimated at 1 PBq. It is assumed that the ²⁰⁷Bi is created in thermonuclear tested explosions in general and that in particular the 55Mt detonation of 30 October 1961 at Novaya Zemlya may have produced this activation product.