Thule Expedition 2003 - Studies on Radioactive Contamination and Particles

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Abstract

Analyses of marine and terrestrial samples collected in August 2003from Bylot Sound at Thule, Northwest Greenland, showed that plutonium fromnuclear weapons in the American B52 plane, which crashed on the sea ice inJanuary 1968, persists in the environment. The highest concentrations ofplutonium were found in the marine sediments under the location where theplane crashed. The distribution of plutonium in the marine sediment is veryinhomogeneous and associated with hot particles with activities found up to1500 Bq 239,240Pu. Sediment samples collected in Wolstenholme Fjord northof the accident site showed plutonium concentrations, which illustrate theredistribution of plutonium after the accident. Seawater and seaweed samplesshowed increased concentrations of plutonium in Bylot Sound. The increasedconcentrations are due to resuspension of plutonium-containing particles fromthe seabed and transport further away from the area. Plutonium concentrationsin seawater, seaweed and benthic animals in Bylot Sound were low but clearlyabove background levels. All soil samples collected from Narssarssuk showedaccident plutonium with levels above background. Plutonium was very inhomo-geneously distributed and associated with particles in the surface layers. Hotparticles were found in soil with activities up to 150 Bq 239,240Pu. Varioustechniques were applied in studying and characterising hot particles, mainlythose found in sediments during earlier expeditions. These techniques includedelectron microscopy (SEM-EDX/WDX), secondary ion mass spectrometry(SIMS), and various synchrotron radiation induced techniques including microX-ray fluorescence spectrometry (SR-μ-XRF), micro X-ray fluorescencetomography and micro X-ray absorption near-edge structure spectrometry (SR-μ-XANES). The techniques proved successful in assessing the source of theparticles and their environmental behaviour. Overall, it can be concluded that plutonium in the marine environment at Thule presents an insignificant risk toman. Most plutonium remains in the seabed under Bylot Sound far from manunder relatively stable conditions and concentrations of plutonium in seawaterand animals are low. However, the plutonium contamination of surface soil atNarssarssuk could constitute a small risk to humans visiting the location ifradioactive particles are resuspended in the air so that they might be inhaled.