Budget of 90Sr in the Gulf of Gdańsk (southern Baltic Sea)

In the period from 2005 to 2011 the major source of 90Sr to the Gulf of Gdańsk was the Vistula river. Its contribution was 99.7% of the total load. The main processes responsible for the decrease in 90Sr activity in the Gulf of Gdańsk were: radioactive decay (87%) and sediment deposition (13%). Average increase in the activity of 90Sr in the Gulf of Gdańsk during the study period was 5.0% (114 GBq), which was almost 2 times higher than the loss of 90Sr due to radioactive decay. In the years 1997-2015, the effective half-life of 137Cs was 9.1 years and that of 90Sr was 50.3 years. Assuming a further decrease in 137Cs and maintaining 90Sr concentrations at present level, it is expected that 90Sr will become the major anthropogenic isotope having impact on the level of radioactivity in the Gulf of Gdańsk.