Sediment mixing and burial of the 239,240Pu pulse from the 1968 Thule, Greenland nuclear weapons accident

A suite of sediment cores was collected in 1984 in Bylot Sound, Greenland, at the site where a US B-52 bomber crashed on the ice in 1968 resulting in the rupture of four nuclear weapons and the release of 1 TBq of plutonium to the underlying seawater/sediment environment. Measurements of 239,240Pu indicate that weapons-plutonium has been preferentially deposited in the fine-grained bottom sediments covering the basins in the vicinity of the crash site. Only minimal dispersal of 239,240Pu to distances greater than 1 km from the crash site can be inferred from comparisons of the 1984 sediment core studies with those undertaken in 1974 and 1979. 210Pb distributions measured in the sediment cores have been simulated using a bio-diffusion model which indicates that burial of 239,240Pu has occurred by the processes of bioturbation and sediment accumulation (at rates of 0.09-0.40 g cm-2 year). Bioturbation has both enhanced the rate of burial of 239,240Pu in the sediments and also maintained an elevated 239,240Pu concentration in the mixing zone at the sediment-water interface. (author)