Cs-137 and Co-60 isotopes and sedimentation rates in Late Holcene sediments from the Northwestern Black Sea

Results of measurements of Cs-137 and Co-60 concentrations in bottom sediments of the Northwestern Black Sea indicate inhomogenity of their distribution both over the studied area and along sediment cores. Intermittency of sediment layers with different concentration of radionuclides in the cores reflects active horizontal movements and redistribution of sediments on the shelf and continental slope. As a result sediment layers dated by the Chernobyl mark as seven years old were found in the 5-7 cm depth layer. Maximum Cs-137 concentration in the surface sedimentary layer on the shelf was 42 mBq/g. Maximum Co-60 concentration of 1320 mBq/g was measured due to a hot particle. No correlation was found between Cs-137 and the Co-60 contents.对西北黑海海底沉积物中铯-137（Cs-137）与钴-60（Co-60）活度浓度的测量结果显示，二者在研究区域内以及沉积岩芯中的分布均存在不均匀性。岩芯中放射性核素浓度各异的沉积层呈现间断分布特征，这反映出陆架与大陆坡区域内沉积物发生了活跃的水平运移与再分配过程。据此，在5~7 cm深度的层位中发现了以切尔诺贝利核事故为年代标记、形成年限为7年的沉积层。陆架表层沉积层中铯-137的最高活度浓度为42 mBq/g；因存在单个放射性热粒子，测得钴-60的最高活度浓度达1320 mBq/g。未观测到铯-137与钴-60的含量之间存在相关性。