Change cyclicity of volumetric activity of radionuclide 137Cs in coastal waters of the Baltic sea and its possible reasons

Monitoring of the volumetric activity (VA) of a radionuclide 137Cs in the coastal waters of the Baltic Sea was carried out near the settlement of Juodkrante in the summer - autumn of 2004. Three measurement stages of the VA of this radionuclide were carried out and hydro meteorological situations were considered simultaneously. 137Cs VA change cyclicity was found out near the seacoast. Extreme data for the whole period of observation were 48 and 94 Bq/m3. Maximal values exceeded minimal data approximately two times, which practically coincided with the radioactive 'background'. The method of mathematical modeling was used to find out possible reasons of 137Cs VA change near the seacoast. Because of lack of information about the location and power of a possible 'source' of radioactive pollution, repeated calculations were carried out, assuming its various places of formation and various power, i e search of optimum coincidence of calculation and measurement data was selected. Optimum coincidence of theoretic and measurement results was found at the location of a radioactive 'source' in the southern part of the Lithuanian sea area at a distance of 25-35 km from Juodkrante. The VA of the radioactive 'source' was 5000 Bq/m3 in the summertime and 15000 Bq/m3 in October of 2004. Agreement of measurement and calculation results was satisfactory for all the observation stages. (author)