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SCALLOPS and fish around Antarctica have been contaminated with radioactive
pollution from nuclear weapons testing and a NASA satellite accident, marine
biologists have found. Although the levels of radioactivity are not hazardous,
Antarctic marine life may be particularly susceptible, they say.

Antarctica is a largely unspoilt and pristine environment, and the Antarctic
Treaty was designed to keep it that way. Military activity is banned from the
continent as is disposing of radioactive waste on or around it. But
鈥渓ong-distance transport of radioactive fallout by winds has brought a general
contamination of the ecosystem鈥�, says Francesco Nonnis Marzano of the University
of Parma in Italy.

Nonnis Marzano and his colleagues measured the accumulation of certain
radioisotopes in the marine life of Terra Nova Bay in the Ross Sea. The isotopes
the researchers tested do not occur naturally and usually come from weapons
testing.

Using a new extraction technique, the researchers found that over 25 per cent
of the plutonium in Antarctic scallops and fish is plutonium-238 rather than
plutonium-239. But only 4 per cent of the fallout from weapons testing is
plutonium-238, which suggests that plutonium is also coming from somewhere else.
The researchers traced the plutonium-238 to a US defence department weather
satellite that failed to reach polar orbit in 1964.

The satellite was carrying a SNAP 9-A radioisotopic thermoelectric generator
(RTG), which used heat from the decay of plutonium-238 dioxide to generate
electricity via a thermocouple. If anything went wrong the satellite was
designed to burn up and disperse its nuclear payload in the upper
atmosphere鈥攚hich it did over the southern hemisphere.

After the accident, NASA changed the design of its RTGs to make sure
radioactive material would be contained. 鈥淩TGs are still required to power
spacecraft, particularly in the exploration of the outer Solar System,鈥� says
Douglas Stetson of the Jet Propulsion Laboratory in Pasadena, California. But
NASA now follows guidelines designed to protect pristine and potentially
biologically interesting environments such as Jupiter鈥檚 moon Europa, he
says.

Antarctic scallops rest during the winter, but make up for it with an intense
burst of filter feeding during the summer months. As a result, the animals can
concentrate up to 9 times as much radioactive material from their environment as
similar species in temperate waters. This contamination is then passed on to the
fish that feed on the scallops.