Deep-sea sediments collected in two areas of the Mediterranean Sea having different sedimentological characteristics have been analyzed to determine present concentrations and inventories of 239,240Pu and to study the main mechanisms controlling them. Plutonium distribution in the deepest part of a submarine canyon (Taranto Valley, Ionian Sea) is compared to that obtained in an abyssal plain (north Algerian Plain). In the latter case, sedimentation is mainly due to the sinking of biogenic particles, while in the former lateral transport of terrigenous material along the slope of the canyon can significantly contribute to sediment accumulation on the bottom. 239,240Pu surface concentration in the canyon ranged from 0.2 to 1 Bq kg-1 (dry weight) and this was lower in the abyssal plain. In this area, plutonium was detectable only in the first 4 cm, while in the canyon it was present down to 11-15 cm. 239,240Pu inventories are 3 Bq m-2 in the plain and 45-60 Bq m-2 in the canyon, indicating considerable input of terrigenous material towards the final part of the Taranto Valley.

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