INFOTERRA: Fw: Sea birds drop radioactivity on land
> http://www.newscientist.com/news/news.jsp?id=ns99993220 The World's
> No.1 Science & Technology News Service
>
> Sea birds drop radioactivity on land
>
> 14:45 04 January 03
>
> Exclusive from New Scientist Print Edition
>
> Droppings from seabirds could be introducing radioactive isotopes
> into the food chain. That is the conclusion of researchers who found
> high levels of radioactivity in droppings and plants on an island
> close to the Arctic.
>
> If tests confirm that the guano is bringing radioactivity ashore,
> it will need to be factored into pollution assessments that gauge
> radiation risks to human health and ecosystems. The risk is probably
> low at temperate latitudes, but could be much greater in the fragile
> wastes of the Arctic.
>
> There, guano is a major source of nutrients for plants, which are
> then eaten by animals.
>
> Radioactive material gets into the oceans from natural geological
> processes on the sea floor, but radioactive isotopes from human
> nuclear activity can add to this. In the Arctic, radioactive material
> has been dumped in the Kara Sea to the east of the Barents Sea.
>
> And radioactive material from nuclear accidents such as the 1986
> Chernobyl disaster has reached the seas, along with particles from
> atmospheric tests of nuclear weapons.
>
> Vast piles
>
> The evidence that bird droppings are bringing radioactivity ashore
> comes from Mark Dowdall and his team at the Norwegian Radiation
> Protection Authority in Tromsx. They spent two years between 2000
> and 2002 collecting soil, vegetation and guano samples from a remote
> coastal inlet called Kongsfjord on the Arctic archipelago of Svalbard,
> about halfway between the northern tip of Norway and the North Pole.
>
> The samples of bird droppings were from vast piles produced by two
> colonies of seabirds supporting kittiwakes, puffins and fulmars.
> Tests showed the guano contained 10 times the concentration of
> radioactive isotopes found at other sites on the island.
>
> The researchers found unusually high concentrations of the natural
> radioisotopes uranium-238 and radium-226, which decay to form more
> hazardous isotopes. But they also found high concentrations of the
> isotope caesium-137, which does not occur naturally. Dowdall suspects
> this is from the fallout of atmospheric nuclear tests carried out
> decades ago.
>
> Tests on vegetation growing near the guano also revealed high
> concentrations of radioactive material. "It means that low levels
> in the Arctic environment don't stay low, they become concentrated,"
> he says.
>
> Fish and crustaceans
>
> Dowdall believes the birds eat contaminated fish and crustaceans,
> and the radioactive material is then concentrated in their faeces.
> The extra nutrients the droppings provide encourage plants to grow,
> and the plants take up and concentrate the radioactive material.
>
> This poses a problem, because plants make up the bulk of the diet
> of many animals, especially that of indigenous reindeer. "We're
> talking about a very vulnerable environment, and when reindeer eat
> the [contaminated] vegetation, it's in the food chain," says Dowdall.
>
> Environmental researchers are intrigued by the finding. "I don't
> think people have looked at this particular pathway before," says
> Scott Fowler at the International Atomic Energy Authority's Marine
> Environmental Lab in Monaco.
>
> However, in 1999, pigeons roosting in contaminated buildings on the
> site of British Nuclear Fuels' Sellafield reprocessing complex in
> Cumbria were found to contain 40 times the European Union's safe
> limit of caesium-137.
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