Plutonium and americium in the deep Black Sea bottom sediments

The new data on ^239+240Pu, ²³⁸Pu, ²⁴¹Pu, ²⁴¹Am vertical distribution in the deep western Black Sea sediments was analyzed. The sediment dating, obtained by means of ²³⁸Pu/^239+240Pu 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 ²³⁸Pu inventory than into ^239+240Pu one. The ²⁴¹Am inventory after-deposition enhancement due to ²⁴¹Pu decay was estimated at 74% in pre-Chernobyl sediment layer and the general contribution of ²⁴¹Pu support in the total ²⁴¹Am inventory in situ enhancement was estimated at 49%.