Birds Bring Radioactivity Ashore 

ANDY COGHLAN / New Scientist 4jan03

DROPPINGS from seabirds could be introducing radioactive isotopes into the food chain. That's the conclusion of researchers who found high levels of radioactivity in droppings and plant an an island dose 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 nutrient for plants, which are then eaten by animals.

Radioactive material get into the oceans tram natural geological processes an 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 test of nuclear weapons.

The evidence that bind droppings are bringing radioactivity ashore comes from Mark Dowdall and his team at the Norwegian Radiation protection Authority in Tromsø. They spent two years between 2000 and 2002 collecting soil, vegetation and guano samples from a remote coastal inlet ailed Kongsfjord an the Arctic archipelago of Svalbard, about halfway between the northern tip of Norway and the North pole. The samples of bind droppings were from vast piles produced by two colonies of seabirds supporting kittiwakes, puffer and fulmars. Tests showed the guano contained 10 limes the concentration of radioactive isotopes found at other sites an 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 doesn't occur naturally. Dowdall suspect this is from the fallout of atmospheric nuclear test carried out decades age. Test an 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.

Dowdall believes the birds eat contaminated fish, and crustaceans, and the radioactive material is then concentrated in their bodies. The extra nutrients the droppings provide encourage plant to grow, and the plant take up and concentrate the radioactive material. This poses a problem, because plant 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 ant 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 an the site of British Nuclear Fuel's Sellafield reprocessing complex in Cumbria were found to contain 40 times the European Union's safe limit of caesium-132 (New Scientist 14 August 1999, p 48).