Transport of plutonium in surface and sub-surface waters from the Arctic shelf to the North Pole via the Lomonosov Ridge

New data on the levels and long-range transport of plutonium in the Arctic Ocean, recorded in the course of two expeditions to this zone in, 1994 and 1996, are discussed in this paper. Specifically, approximately 100 plutonium measurements in surface and sub-surface water sampled at 58 separate stations throughout the Kara, Laptev and East Siberian Seas, as well as along latitudinal transects across the Lomonosov Ridge, are reported and interpreted in terms of the circulation pathways responsible for the transport of this element from the North Atlantic to the Arctic Shelf and into the Arctic interior. In addition, the behaviour of plutonium in its transit through the vast Arctic shelf seas to open waters under extreme environmental conditions is discussed in terms of the partitioning of plutonium between filtered (<0.45 mum) seawater and suspended particulate, and its association with colloidal matter. Finally, limited evidence of the presence of a colloidal plutonium component in Arctic waters subject to direct riverine input is adduced.