Plutonium concentration in sediment cores collected in the Mediterranean Sea

As is well known, the determination of plutonium isotopes in the marine environment is of great importance to calculate the contamination due to the nuclear industry and to better understand sedimentation processes. In the last 20 years sea sediment cores have been collected in different areas of the Mediterranean Sea by four Italian research teams. The sampling depth ranged from 50 to 2800 m and the core lengths were 10–30 cm. The radioanalytical procedures were based on plutonium separation by anion exchange resins or by extraction chromatography with Microthene-TOPO; plutonium electroplating was performed before α-spectrometry. The final chemical yields were determined by spiking with 236Pu or 242Pu. In some cases 238Pu could be detected. As far as the vertical profiles are concerned, no significant subsurface maxima resulted for the cores collected at greatest depth; on the contrary interesting peaks were found for cores collected at 50–100 m depth.