Change Cyclicity of Volumetric Activity of Radionuclide 137cs in Coastal Waters of the Baltic Sea and Its Possible Reasons

Abstract

Monitoring of the volumetric activity 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 hydrometeorological 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 sea‐coast. 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.

Comparison and Analysis of Investigation Results on Volumetric Activity of 137cs at the Baltic Sea Coast in 2003–2005

“…The detailed measurements of 137 Cs VA in the coastal waters of the SEPBS were carried out in 2004. The obtained results showed that the measurement values exceeded calculated data two times or more [20]. However, a satisfactory coincidence of measured and calculated results in the summer and autumn of 2005 was observed.…”

“…The highest values are registered in 2004, when the greatest instability of absolute values of 137 Cs VA was observed [20]. The curves presented in Fig 2 define a possible tendency of changes in 137 Cs VA in coastal waters of the Baltic Sea.…”

“…In 1986 a growth in the VA of artificial radionuclides was also observed [11], but the surface waters of the Baltic Sea were practically purified from these radionuclides within rather short periods [2]. The publications [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23], etc present the distribution of the 137 Cs radionuclide VA after the accident at the ChPP.…”

“…During a period of time, a levelling of the 137 Cs VA in the surface waters took place; the end of this process may be ascribed to 1989, when its VA appeared to be about 150 Bq/m 3 [12]. Until now an increased 137 Cs VA (45-50 Bq/m 3 ) in the southeastern part of the Baltic Sea (SEPBS) considerably exceeded the radioactive background formed by the global fallout [20]. By 1996 the 137 Cs VA in the SEPBS appeared to be vertically homogeneous [22].…”

On variations of volumetric activity of 90Sr and 137Cs in the Baltic Sea coastal waters near the shore of Lithuania in 2005–2009

“…Thus, in 2004 the extreme values of 137 Cs VA were 94 and 49 Bq/m 3 [ 10 ] and 90 Sr VA were 17 and 7 Bq/m 3 [ 11 ]. They indicate major changes in the absolute values of the radionuclide VA.…”