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Row surfaces over sunken nuclear sub

作者:公冶钺    发布时间:2019-03-02 08:10:04    

By DEBORA MacKENZIE in BRUSSELS The Komsomolets, a Soviet nuclear submarine that sank north of Norway in 1989, is lying in deep, placid waters and is unlikely to contaminate fisheries. These are the conclusions of a report, released last week, by an international team of scientists which surveyed the area around the submarine. But Norwegian oceanographers argue that the wreck is far from harmless. It sits, they say, near an unusual undersea ‘highway’ that could carry contaminants directly to rich fishing grounds. Norwegian, Dutch, American and Russian scientists spent a month aboard a Russian research vessel studying the wreck with remote-controlled submarine cameras and measuring currents and contamination. They found that the wreck is leaking small amounts of radioactive caesium from its reactor, and plutonium from its two nuclear warheads. Forty-two people died when the submarine sank near Bear Island, 500 kilometres from the Norwegian coast. It now lies at a depth of 1670 metres. No commercially exploited fish live this deep. But Igor Spassky of the Rubin Institute in St Petersburg, which designed the Komsomolets, has argued that currents as fast as 150 centimetres per second, combined with extensive mixing of deep and surface water in the region, could carry radioactive contamination from the wreck to fishing grounds. Spassky and others have called for the Komsomolets to be raised (This Week, 13 February). Charles Hollister, of the Woods Hole Oceanographic Institution in Massachusetts, says the Komsomolets is best left where it is. Last month’s expedition measured currents near the wreck of at most 50 centimetres per second, heading north. These will carry radioactive substances away from most significant fisheries, he says. And, judging from the density and temperature of the water, material transported upwards would rise only 500 metres from the seabed. This ‘suggests there is no significant present or future threat to human health’, says Hollister. But Peter Haugan of the Nansen Environmental and Remote Sensing Centre in Smolheimsviken, Norway, says bottom currents and upwelling are not the problem. There is a dome-shaped mass of deep, dense water in the Greenland Sea, with its apex in the middle of the sea, and its edges on the sea bottom. ‘It is well known,’ says Haugan, ‘that substances in the ocean are carried preferentially along the boundary between two masses of water of different densities.’ Such ‘density surfaces’ usually lie horizontally in the ocean, between deep, dense water masses and surface water masses that are less dense because they are warmer and diluted with inflowing fresh water. But in the Greenland Sea the ‘density surface’ is inclined. Haugan says this creates a highway for contaminants from the sea bed towards the surface. And the start of the highway is located close to where the Komsomolets lies. The top of the dome lies only 200 metres beneath the surface of the Greenland Sea, in a rich fishing area. ‘We don’t want to say there will be significant contamination there, because we don’t know how much is leaking out,’ says Haugan. ‘But if anything is released, it will be carried to that location, in less than ten years.’ aterial is being released. The warheads especially are badly damaged and leaking plutonium. But, says Hollister, plutonium is likely to remain bound to sediment, which is shifting down the slope on which the wreck sits. ‘At worst, it might be a few metres away in 500 years,

 

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