8.4.1 Investigation of Cesium- 137 Distribution in 

 Seawater 



VLADIMIR I. MEDINETS\ VLADIMIR G. SOLOVIEV\ and BORIS V. GLEBOV 



'Odessa Branch of Slate Oceaiwgraphic Institute, Odessa, USSR 



'Institute of Global Climate and Ecology, State Committee for Hydrometeorology and Academy of Sciences, Moscow, USSR 



Introduction 



Nuclear exercises during the last 30 years and modem 

 development of nuclear energy are the main sources of global 

 and regional nuclear pollution of the biosphere, especially the 

 world oceans. The main potential hazard is the accumulation 

 of long-lived radionuclides of anthropogenic origin, such as 

 Sr'*", Cs'", and Pt"", in various natural objects. 



The stable level of nuclear pollution in the environment 

 (after the banning of nuclear exercises in the atmosphere) was 

 disturbed in 1986 by the accident at the Chernobyl nuclear 

 power station, which led to a massive input of radioactive 

 substances. As a result of this accident, very high concentrations 

 of radionuclides were found in the environment of Europe and 

 the whole of the Northern Hemisphere (Uematsu & Duce, 

 1986: Buesseler, 1987; Kusakabe et ai, 1988; Nikitin et al., 

 1988). 



During the 47th cruise of the Soviet research vessel 

 Akademik Korolev. we investigated the present state of 

 radionuclide contamination in the waters of the Chukchi and 

 Bering Seas based on the distribution of the long-lived 

 radionuclide Cs'". 



Methods 



Sampling of large volumes of water (0.8-1.1 m') was 

 carried out at depths of to 170 m with immersion pumps, 

 models 'NIVA' and 'MALYSH.' To selectively concentrate 

 the Cs'" from the sea water, we used fibrous sorbents, 

 "MILTON-T," impregnated with copper ferrocyanide 

 (Vakulovsky, 1986). Aftersampling. the sorbent was ashed in 

 an oven at temperatures not exceeding 450°C. The ash 

 ( 1 0- 1 3 g) was packed hermetically in polyethylene film. Later 

 these samples were transported to the special laboratory of the 

 State Oceanographic Institute (Odessa Branch), where analyses 

 were carried out using the following gamma-spectrometer: 



— scincilatic (firm LKL WALL AC type COMPU- 

 GAMMA 1282) 



— semiconductoric (analyzer AMA-0202 with detector 



DGDK-IOOB) 

 The accuracy was in the range of 10%, and the detection limit 

 was 0.1 Becquerel (Bq). 



The concentration of Cs'" (the natural radioactive form of 

 cesium) in every sample was less than the detection limit. 

 Therefore, we suggest that the maximum possible concentration 



of Cs' " in the investigated samples could not be any higher than 

 0.015 Bq/m\ 



Results and Discussion 



The concentrations of Cs' " that were measured during this 

 investigation of the Bering and Chukchi Seas are given in 

 Table 1 . 



Assuming that the detection limit of Cs'** was the maximum 

 possible concentration of this radionuclide in the investigated 

 areas, and basing this concentration on the initial correlation of 

 Cs'"/Cs"'' activities during the Chernobyl accident, we 

 estimated its influence on the radioactive pollution of the 



TABLE 1 



Concentration of Cs'" in the Bering and 

 Chukchi Seas, summer, 1988. 



Date 



Location 



lat. long. 



Layer, 

 (ml 



Average 



concentration, 



(Bq/m') 



327 



