Carbon and Pu isotopes in Baltic Sea sediments.

Distributions of 137Cs, 239,240Pu, Δ14C and δ13C measured in sediments indicated low 137Cs and 239,240Pu activities in the Curonian Lagoon and higher levels in the open Baltic Sea. Depleted δ13CTOC values were found in the Curonian Lagoon as compared with the open Baltic Sea, while the most depleted Δ14CTOC values were found in the Gotland Deep. The global fallout Pu dominated in the deeper zones of the Baltic Sea, while higher 240Pu/239Pu atom ratios were characteristic of the coastal regions.

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

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.