Atmospheric deposition and riverine load of 90Sr and 137Cs to the Gulf of Gdańsk (southern Baltic Sea) in the period 2005-2011

In the period 2005-2011 total atmospheric fallout and the riverine input to the Gulf of Gdańsk was 1168.8 GBq of 90Sr and 424.1 GBq 137Cs. The major source of both radionuclides to the Gulf of Gdańsk is the Vistula river; its contribution reached 99.7% in the case of 90Sr and 95.8% regarding 137Cs. The atmospheric load of 137Cs, 18.1 GBq, was nearly 4 times bigger than in the case of 90Sr (3.75 GBq). In the period 2005-2010, the average annual atmospheric load were at the levels 2-3 GBq for 137Cs and 0.4-0.6 GBq for 90Sr, while in 2011, due to the Fukuchima Dai-ichi power plant break down, an increase of annual atmospheric loads was noted to 5.3 GBq of 137Cs and to 0.87 GBq of 90Sr. The additional loads did not have an increasing effect on the activity concentrations of 137Cs and 90Sr in seawater of the Gulf of Gdańsk, where mean activity concentrations in seawater were equal to 31.1 Bq m−3 and 7.6 Bq m−3 in the case of 137Cs and 90Sr respectively.