Cs, Am and Pu isotopes as tracers of sedimentation processes in the Curonian Lagoon–Baltic Sea system

137 Cs, 241 Am and Pu isotopes were analyzed in seawater, bottom sediments (BS) and suspended particulate matter samples collected in the Baltic Sea during 1997–2011. The particle size distribution and sequential extraction studies were carried out with the aim to better understand the association of radionuclides with particles and their bonding patterns in the BS. δ 13 C org was applied for identification of sources of organic matter in the studied area. It has been found that massic activities of 137 Cs in BS varied from 2.1 to 588 Bq/kg. High correlation of 137 Cs massic activities with total organic carbon (TOC) in BS ( r = 0.75) and with clay minerals ( r = 0.95) was found. 239,240 Pu massic activities in BS varied from 0.03 to 7.5 Bq/kg. High correlation with TOC was found for 239,240 Pu ( R = 0.98) as well as for 241 Am ( r = 0.96). δ 13 C org in the studied samples ranged from −22.3 to −31.8 ‰.