@misc{oai:repo.qst.go.jp:00074819,
 author = {Yamada, Masatoshi and Zheng, Jian and Yamada, Masatoshi and Zheng, Jian},
 month = {Feb},
 note = {The plutonium isotopes, 239Pu and 240Pu, have been added to the surface ocean mainly as a consequence of global fallout from atmospheric nuclear weapons testing, while a second source has been close-in fallout from nuclear weapons testing at the Pacific Proving Grounds. Since the 240Pu/239Pu atom ratio depends on the specific weapons design and test yield, it is a powerful fingerprint to identify the sources of Pu in the ocean. The objectives of this study are to determine the 239Pu, 240Pu and 239+240Pu concentrations and 240Pu/239Pu atom ratios in seawater from the Indian Ocean and to discuss the transport processes of plutonium in the ocean. The 239Pu and 240Pu concentrations and 240Pu/239Pu atom ratios were measured with an isotope dilution sector field-inductively coupled plasma-mass spectrometer (SF-ICP-MS), which was equipped with a guard electrode to eliminate secondary discharge in the plasma and to enhance overall sensitivity. The atom ratios in water column from the Indian Ocean were significantly higher than the mean global fallout ratio of 0.180. These high atom ratios proved the existence of close-in fallout plutonium originating from the Pacific Proving Grounds. The Bikini close-in tropospheric fallout Pu could be transported to the eastern Indian Ocean by ocean currents., European Winter Conference on Plasma Chemistry (EWCPS)2019},
 title = {Determination of Pu-239, 240 concentration and Pu-240/Pu-239 atom ratio in seawater using an isotope dilution sector field-inductively coupled plasma-mass spectrometry},
 year = {2019}
}