Evolution of radiocontamination in the Mediterranean Sea in the period 1985-1995

Investigations were carried out on several biotic and abiotic samples to de termine the environmental radiocontamination of the Mediterranean Sea after the Chernobyl accident. Special emphasis was put on the determination of C s-137 in the Adriatic Sea. This caesium isotope was the most abundant radio nuclide in a wide variety of samples (seawater, sediment, pelagic and benth ic species). Attention was also paid to the neutron activation products Ag- 110m and Cs-134, which were first discovered in the Adriatic ecosystem afte r the Chernobyl event. In particular, although the Ag-110 fallout depositio n over the area was neglegible in comparison with that of Cs-137, its conce ntration factors and bioaccumulation in macroalgae and molluscs were much h igher, suggesting some particular physiological accumulation mechanism. Con centrations of Sr-90, Pu-238 and Pu-239+240 were monitored in sediment samp les collected in the period 1990-1993. A comparison of the radionuclide con centrations between the open sea area and the Po river estuarine ecosystem is also reported.