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The evidence that bird droppings are bringing radioactivity ashore comes from Mark Dowdall and his team at the Norwegian Radiation Protection Authority in Tromsų. 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.
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.
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