Distribution of trace elements and radionuclides in the Curonian Lagoon and the Baltic Sea

This study presents the distribution of trace elements (Hg, Cd, Pb, Cr, As, Cu, Ni, Zn, Co, V, Al, Li), organic carbon, δ¹³C_org and radionuclides (⁹⁰Sr, ¹³⁷Cs, ^{239, 240}Pu, ²⁴¹Am) in the Lithuanian part of the Baltic Sea and the Curonian Lagoon. Particulate matter (PM) and bottom sediment samples were collected during the sampling campaigns in the frame of the State monitoring and during several other investigations over the period of 1997-2011. The study area is characterized by variable loading with particulate matter. Averaged concentrations of the particulate matter in the water of the Curonian Lagoon area tended to be approximately 3 times higher in comparison with those measured in the Baltic Sea. Results showed a strong relation between metals and organic carbon in particulate matter (r=0.69-0.98, p<;0.05). The correlation between metals and organic carbon in sediments was not so strong and varied in the range of 0.45-0.84. It was found out that the highest concentrations of trace elements in the Baltic Sea accumulated in the deepest stations of R7, 12A, 46 with the fine-grained, organic-rich sediments. Pollution was strongly pronounced in the Curonian Lagoon (including Klaipeda Strait area), elevated concentrations of metals were also measured in sediments of the plume of the Lagoon water, dumping of dredged material areas and in the aleurite sediments in the Baltic Sea. Higher level of elements accumulated in the surface sediments (0-3 cm), the difference between core layers was more evident at the deepest stations. According to the results, higher concentrations of radionuclides accumulated in PM and sediments as compared to marine water. The correlation of ¹³⁷Cs, ^{239, 240}Pu and ²⁴¹Am with total organic carbon in bottom sediments was found to be 0.75-0.98. δ¹³C_org in particulate matter, surface bottom sediments and humic substances of the Curonian Lagoon and the Baltic Sea ranged from -22.3 ⁰/₀₀ to -31.8 ⁰/₀₀. δ¹³C_org values in the bottom sediment samples well correlated with δ¹³C_org values in PM and humic acid samples.