Temporal Changes in Radioactive Cs Concentration in Sea Sediment off East Japan, after the Fukushima Dai-Ichi Nuclear Accident

Measurement techniques using a towed gamma ray spectrometer allows to map the continuous distribution of ¹³⁷ CS on the seafloor within 30 km of the F1NPP. This study has revealed that the temporal change in the ¹³⁷ Cs concentration does not show a constant rate of decrease. Furthermore, the local ¹³⁷ Cs anomalies, with concentrations of ¹³⁷ Cs one or two order of magnitude higher than the surrounding seafloors, is influenced by local features of the bathymetric feature.