Radioactivity in the Baltic Sea: inventories and temporal trends of 137Cs and 90Sr in water and sediments

Abstract

The Baltic Sea is ecologically unique as one of the world's largest brackish water basins. It was signifi- cantly contaminated by radioactivity following the Cher- nobyl accident in 1986, the major contaminant being long- lived 137 Cs. Due to the slow exchange of water between the Baltic Sea and the North Sea and the relatively rapid sed- imentation rates, radionuclides have prolonged residence times in the Baltic Sea. 137 Cs levels are consequently still clearly higher than in other water bodies around the world. In addition to the Chernobyl accident, artificial radionuc- lides in the Baltic Sea originate from the global fallout following nuclear weapons testing in the 1950s and 1960s, while discharges into the Baltic Sea from nuclear power plants and other facilities are of minor importance. Here, inventories and the temporal evolution of radionuclides both in seawater and sediments of the Baltic Sea are pre- sented and discussed.