Chernobyl still with us : (137)Caesium activity contents in seabed sediments from the Gulf of Bothnia, northern Baltic Sea

Anthropogenic radionuclides are among those human impacts, which can be seen widely in the marine and terrestrial ecosystems. Fallout from the 1986 Chernobyl nuclear power plant accident has rendered the Baltic Sea as the most polluted marine body in the world with respect to Cs-137. This research investigated sediment cores from 56 sites around the Gulf of Bothnia, Baltic Sea. Radioactivity from Cs-137 in sediments has generally declined due to natural/radioactive decay of Cs-137 over the last decades. However, Cs-137 contents in subsurface sediments remain at elevated levels compared to pre-Chernobyl levels. The highest Cs-137 activity contents in subsurface sediments (>4000 Bg kg(-1)) occur in coastal areas including estuaries. These areas often experience severe anthropogenic pressure. The southern Bothnian Sea, Kvarken archipelago, and southern Bothnian Bay all show elevated Cs-137 values in subsurface sediments. Sedimentary Cs-137 can also help constrain recent rates of sedimentation. Post-Chernobyl sedimentation rates in the Gulf of Bothnia varied from 0.1 to 4.8 cm/year with an average sedimentation rate of 0.54 cm/year.Peer reviewe