Radioactive plutonium remains from US military accident in Spain

Researchers from the Physics Department and the Institute of Environmental Science and Technology (ICTA) of the Universitat Autònoma de Barcelona have detected concentrations of radioactive plutonium and americium in plankton from the coast of Palomares (south-east coast of Spain), with an activity level five times higher than the average of other samples taken from the Mediterranean. This is residual contamination from the air accident that occurred on 17 January 1966, when two US military aircraft collided. However, the radioactivity levels are still within safety margins.

Radioactive elements from the marine environment may pass into the human food chain via plankton when marine products are consumed. With the aim of studying this transference, scientists have established the concentrations of radioelements plutonium (Pu-239,240) and americium (Am-241) in plankton samples taken from different areas of the north-west Mediterranean. Specifically, researchers compared samples from the gulf of Vera (in the area of Palomares, Almeria), Garrucha beach (Almeria), Mallorca, the Gulf of Sant Jordi (Baix Ebre, Catalonia), the coast of Barcelona, and the Golf of Lyon (France).

The results of the research clearly show that plankton from the coast of Palomares, obtained from a depth of 50 metres, contains radioactive plutonium and americium with an activity up to five times higher than the average of the other samples studied. Thus, while average radioactivity in western Mediterranean plankton is around 452 units (millibequerels per kilogram of dried plankton), at Palomares this figure is 2,046 units. This is still within the safety margins recommended by the International Atomic Energy Agency, but serves as a reminder that the area is not free of residual contamination arising from the accident that occurred on 17 January 1966, when two US planes, a B-52 bomber, loaded with 4 nuclear warheads, and a refuelling plane collided in mid-flight.

Other sources of radioactive elements present in small quantities in Mediterranean plankton are the remains of nuclear tests carried out between 1952 and 1963 around the world, residues from nuclear power stations, and the Chernobyl accident of 1986. These activities have gradually left radioactive elements in the marine environment which, in simple terms, have been transferred to the phytoplankton (plant plankton), then to the zooplankton (animal plankton), and from here to certain marine products that we consume. Therefore, it is vital that checks are made on radioactivity levels in plankton in order to provide global assurances of the safety of marine products.

This research, directed by the UAB lecturer Joan Albert Sánchez Cabeza, and in which researchers from the Institute of Marine Sciences of Barcelona and two research centres in Eire and the United States have also participated, is published in the journal The Science of the Total Environment.