Distribution and flux of 238Pu, 239,240Pu, 241Am, 137Cs and 210Pb to high arctic lakes in the Thule district (Greenland)

Environmental samples (soil, sediment and lake water) in the Thule area (NW Greenland) have been studied to assess the contamination of radionuclides originating from a nuclear weapons accident (the Thule accident in 1968). Four lakes were chosen at different distances from the point of impact with the Thule air base community situated in between. The sedimentation rates in the lakes varied from 0.4 mm a−1 (5 mg cm−2 a−1) to 1.6 mm a−1 (82 mg cm−2 a−1). With these sedimentation rates, it is not possible to resolve the 239,240Pu global fallout peak from a possible 239,240Pu “accident” peak in the sediment depth profiles. However, the 239,240Pu/137Cs and the 238Pu/239,240Pu ratios agreed well with global fallout ratios, indicating that plutonium originating from the accident had not reached these lakes. This also indicates that the Thule air base community has probably only been exposed to radionuclides from the accident to a very limited extent. A limited study showed that 210Pb could not be used as a normalizing nuclide to explain the transport of transuranic elements from the catchment area to the lake, i.e. 210Pb has a different transport mechanism from that of the transuranic elements studied in this investigation.