Plutonium and americium in the deep Black Sea bottom sediments.

The new data on Pu, Pu, Pu, Am vertical distribution in the deep western Black Sea sediments was analyzed. The sediment dating, obtained by means of Pu/Pu activity ratio vertical distribution, suggested the upper 3 cm layer of sediments to be formed during 27 years after the Chernobyl accident and the deeper layers to be formed earlier in pre-Chernobyl time (before 1986). The whole data set on profiles of radionuclides studied was shown to reflect the history of their input into the basin and elimination of these radionuclides from the water column. Analysis of inventories of plutonium alpha-emitting nuclides ensured a more significant contribution of Chernobyl fallout into the present total Pu inventory than into Pu one. The Am inventory after-deposition enhancement due to Pu decay was estimated at 74% in pre-Chernobyl sediment layer and the general contribution of Pu support in the total Am inventory in situ enhancement was estimated at 49%.