Estimation of recent sediment accumulation rates in the Baltic Sea using artificial radionuclides 137Cs and 239,240Pu as time markers

This study reviews sediment data obtained from the Baltic Sea from 1995–2003. Recent sediment accumulation rates (SAR) were estimated at 69 stations in the Baltic Sea from 99 sediment cores using concentration peaks of 137Cs and 239,240Pu as time markers of the years 1986 and 1963, respectively. SAR values varied widely between 60–6160 g m–2 yr–1. The highest SAR values were observed at stations in the northern part of the Bothnian Sea, river estuaries and the eastern part of the Gulf of Finland. Generally, the SAR (median) of stations in the Bothnian Sea was two times higher than values in the Gulf of Finland or the Bothnian Bay, and about seven times higher than in the Baltic Proper. A strong correlation was detected between the SAR and total 137Cs activities. The usability of estimation methods has been considered and, e.g., unstable sedimentation could limit the use of radionuclides in sediment dating and estimation of the SAR at stations in the Baltic Sea.