Lateral distributions of Th-228 activity and Ra-228/Ra-226 activity ratio of surface water within the Sea of Japan, the East China Sea, and the Sea of Okhotsk

Yoshida, Keisuke*; Inoue, Mutsuo*; Minakawa, Masayuki*; Nakano, Yusuke*; Kofuji, Hisaki*; Otosaka, Shigeyoshi; Kiyomoto, Yoko*; Shiomoto, Akihiro*; Hamajima, Yasunori*; Yamamoto, Masayoshi*

no journal, , 

The authors have developed an analytical method for Th-228, Ra-226 and Ra-228 measurements in seawater using an ultra-low background -ray detector. In this study, the authors measured the three radionuclides in surface seawater obtained from 16 stations in the Japan Sea, East China Sea and Okhotsk Sea. Concentrations of Ra-228 and Th-228 in surface waters in the southern Japan Sea were lower than those in the northern regions. Considering that the Th-228/Ra-228 activity ratios were not different between the northern and southern regions of the Japan Sea, we could conclude that (1) input of terrestrial materials from the East China Sea has not affected the distribution of the radionuclides in the Japan Sea, and (2) the efficiency of scavenging was not different between the regions.