Distribution of <sup>137</sup>Cs in the Surface Layer of the Black Sea in Summer, 2017
Purpose. The purpose of the study is to investigate distribution of <sup>137</sup>Cs in the coastal and deep-water part of the Black Sea. To achieve this goal, the following scientific problems has to be solved: choosing a method for concentrating <sup>137</sup>Cs from seawater samples, seawater sampling and <sup>137</sup>Cs concentrating, measurements of the obtained samples, discussion of the obtained results and their comparison with the available scientific literature data. Materials and Results. Distribution of <sup>137</sup>Cs activity in the coastal and deep-water part of the Black Sea was studied. The in situ data on spatial-temporal variability of the <sup>137</sup>Cs volumetric activity field in the Black Sea surface layer obtained in course of the 95<sup>th</sup> cruise of the R/V "Professor Vodyanitsky" in June, 14-July 7, 2017 were used. The data on the radionuclide vertical distribution in the sea active layer were obtained at a number of stations. 22 seawater samples were taken and processed at 11 stations. To separate <sup>137</sup>Cs from seawater, a ferrocyanide sorbent of the FCC brand was first applied; it was intentionally developed for selective recovery and separation of <sup>134</sup>Cs and <sup>137</sup>Cs radionuclides from the technological processing solutions and radioactive waste water. Conclusions. According to the results, the volumetric activity of <sup>137</sup>Cs varied spatially in the range 5.7-8.8 Bq/m<sup>3</sup> and amounted on average 6.9 ± 0.2 Bq/m<sup>3</sup>. Within the active layer boundaries, vertical distribution of <sup>137</sup>Cs was found to be uniform.