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

Abstract Activities of 137 Cs, 241 Am and 239,240 Pu 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 137 Cs 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 238 Pu/ 239,240 Pu and atom 240 Pu/ 239 Pu 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 238 Pu/ 239,240 Pu and atom 240 Pu/ 239 Pu 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 241 Am was found to be similar to that of Pu isotopes.