Correlation Analysis between the ¹³⁷Cs Concentration and Chemical/Physical Factors of Bottom Sediments in the Coastal Waters around Japan

Abstract

Chemical and physical factors were measured in bottom sediments taken in coastal waters around Japan. They include concentration of ¹³⁷Cs, stable elements, particle size distribution, organic carbon, nitrogen contents and density. Intercorrelations among the factors were calculated in order to study the relationship between the concentration of ¹³⁷Cs and the physical and chemical factors of bottom sediments. Significant correlations (r > 0.8) existed between the ¹³⁷Cs concentration and some factors such as total organic carbon, 75 μm passing rate and specific surface area in samples taken in areas without any impact of the Fukushima Dai-ichi Nuclear Power Station accident. However, the sediment samples taken in the waters off Miyagi, Fukushima and Ibaraki Prefectures, where accident-derived ¹³⁷Cs was found, did not show any good relationships between ¹³⁷Cs and any other factors, suggesting that newly added Fukushima-derived ¹³⁷Cs, which was unevenly distributed in seawater, deposited onto the sediment irrespective of the pre-accident relationships among the chemical and physical factors.