title: Historical record of nuclear activities from129I in corals from the northern hemisphere (Philippines).
abstract: Iodine-129 is a long-lived fission product that is majorly released in human nuclear activities (HNA) such as nuclear bomb testing, nuclear fuel reprocessing, and nuclear accidents. It is a good environmental tracer and former measurements of129I in corals from the southern hemisphere show the increasing trend of129I concentrations in the marine environment caused by HNA. Here we show time series of129I/127(stable)I isotopic ratios in two coral cores from the northern hemisphere (Philippines) and how these record129I released from HNA in even greater, unprecedented detail. Corals were taken from the Pacific Ocean (Baler) and South China Sea (Parola) sides of the Philippines. We observed nearly identical peaks (129I/127I ∼ 31.5 × 10-12) in both the Baler and Parola records, each attributed to the year 1962 - the year with the highest recorded amount of129I release from nuclear bomb testing. This 1962129I bomb signal offers a new time marker that can be used to establish or confirm age models of corals, comparable to or possibly better than the well-known coral14C bomb peak. We also observed nuclear fuel reprocessing and Chernobyl accident129I signals in years 1977, 1980, and 1986, concurrently in Parola and with 9 to 11-year lags in Baler. This discrepancy in timing suggests that129I was transported to the South China Sea and Pacific Ocean sides of the Philippines directly from the atmosphere and through prevailing ocean currents, respectively. Lastly, we observed surprisingly high129I/127I isotopic ratios (i.e., 22.8 to 38.9 × 10-12) in the Parola record after the year 1996, which is in contrast to the decreasing trend observed in the Baler record and in published129I releases of different HNA. These results possibly indicate the presence of unknown sources of129I in the South China Sea region.
authors: Department of Nuclear Engineering and Management, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan; Philippine Nuclear Research Institute - Department of Science and Technology, Commonwealth Ave., Diliman, Quezon City 1101, Philippines. Electronic address: atbautistavii@gmail.com.
authors: Angel T
authors: AT
authors: Bautista
authors: Department of Nuclear Engineering and Management, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan; Micro Analysis Laboratory, Tandem Accelerator (MALT), The University Museum, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
authors: Hiroyuki
authors: H
authors: Matsuzaki
authors: Marine Science Institute, University of the Philippines Diliman, Quezon City 1101, Philippines.
authors: Fernando P
authors: FP
authors: Siringan
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000737:chemistry*; D007457:Iodine Radioisotopes / Q000032:analysis*; D013058:Mass Spectrometry; D010679:Philippines; D011834:Radiation Monitoring; D018788:Radioactive Hazard Release; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D007457:Iodine Radioisotopes; D014875:Water Pollutants, Radioactive
keywords: Accelerator mass spectrometry; Coral; Iodine-129; Nuclear accident; Nuclear fuel reprocessing; Nuclear weapons