Transport of 137Cs, 241Am and Pu isotopes in the Curonian Lagoon and the Baltic Sea

Activities of 137Cs, 241Am and 239,240Pu were analyzed with special emphasis on better understanding of radionuclide transport from land via the Neman River estuaries to the Baltic Sea and behavior in the marine environment. Although activity concentrations of 137Cs in water samples collected the Baltic Sea were almost 100 times higher as compared to the Curonian Lagoon, its activities in the bottom sediments were found to be comparable. Activity 238Pu/239,240Pu and atom 240Pu/239Pu ratios indicated a different contribution of the Chernobyl-originated Pu to the suspended particulate matter (SPM) and bottom sediments. The largest amount of the Chernobyl-derived Pu was found in the smallest suspended matter particles of 0.2–1 μm in size collected in the Klaipeda Strait in 2011–2012. The decrease of characteristic activity 238Pu/239,240Pu and atom 240Pu/239Pu ratios towards the global fallout ones in surface soil and the corresponding increase of plutonium (Pu) ratios in the suspended particulate matter and bottom sediments have indicated that the Chernobyl-derived Pu, primarily deposited on the soil surface, was washed out and transported to the Baltic Sea. Behavior of 241Am was found to be similar to that of Pu isotopes. -- Graphical abstract: The Chernobyl-derived Pu in the suspended particulate matter collected in the Klaipėda Strait. Highlights: • The decrease in 137Cs activity concentrations in Baltic Sea waters was determined. • Strong correlation of 239,240Pu and 241Am with TOC was observed. • Amount of the Chernobyl-derived Pu varied in the suspended particles and bottom sediments. • Transport of the Chernobyl-derived Pu to the Baltic Sea was found