Radioactivity data analysis of 137Cs in marine sediments near severely damaged Chernobyl and Fukushima nuclear power plants

Using several accessible published data sets, we analyzed the temporal change of Cs-137 radioactivity (per unit mass of sample) in marine sediments and investigated the effect of the water content of sediment on the Cs-137 radioactivity, to understand the behavior of Cs-137 present in marine environments. The Cs-137 radioactivity in sediments decreased more slowly in the Baltic Sea (near the Chernobyl nuclear power plant) than in the ocean near the Fukushima Daiichi nuclear power plant (FDNPP). The Cs-137 radioactivity in the sediment near the FDNPP tended to increase as the water content increased, and the water content decreased at certain sampling sites near the FDNPP for several years. Additionally, the decrease in the water content contributed to 51.2% of the average Cs-137 radioactivity decrease rate for the same period. Thus, it may be necessary to monitor both the Cs-137 radioactivity and the water content for marine sediments to track the Cs-137 that was discharged from the sites of Chernobyl and Fukushima nuclear power plants where severe accidents occurred. (C) 2019 Korean Nuclear Society, Published by Elsevier Korea LLC.