The triple disaster of the March 11, 2011, earthquake, tsunami, and subsequent radiation releases from Japan’s Fukushima Dai-ichi nuclear power plant were unprecedented events for the ocean and society. In this article, the radioactive releases from this event are compared to natural and prior human sources, with particular attention to cesium-137 and -134 radioisotopes. Total releases from Fukushima are not well constrained, with estimates from atmospheric fallout and direct ocean discharge spanning 4 to 90 peta Becquerels (PBq), but are most likely in the 15–30 PBq range. This source is smaller than any 137Cs remaining in the North Pacific from global and close-in fallout from the 1960s. It is of similar magnitude to 137Cs released to the ocean from the Sellafield nuclear reprocessing site on the Irish Sea, though of greater magnitude than fallout that reached the ocean from the 1986 Chernobyl nuclear power plant disaster in the Ukraine. The fate of Cs is largely determined by its soluble nature in seawater, though uptake in sediments does occur via cesium’s association with both detrital particles and biological uptake and sedimentation. A mass balance of Cs supply from rivers and ongoing leakage from nuclear power plants suggests that sediments will remain contaminated for decades. This may be one reason why Cs concentrations in benthic fish stay elevated over predictions, causing fisheries to remain closed near Fukushima and ongoing concern to the public.

Buesseler, K.O. 2014. Fukushima and ocean radioactivity. Oceanography 27(1):92–105, https://doi.org/10.5670/oceanog.2014.02.

Aarkrog, A. 2003. Input of anthropogenic radionuclides into the World Ocean. Deep Sea Research Part II 50:2,597–2,606, https://doi.org/10.1016/S0967-0645(03)00137-1.
1. Aoyama, M., D. Tsumune, and Y. Hamajima. 2013. Distribution of 137Cs and 134Cs in the North Pacific Ocean: Impacts of the TEPCO Fukushima-Daiichi NPP accident. Journal of Radioanalytical and Nuclear Chemistry 296:535–539, https://doi.org/10.1007/s10967-012-2033-2.
2. Bailly du Bois, P., P. Laguionie, D. Boust, I. Korsakissok, D. Didier, and B. Fievet. 2012. Estimation of marine source-term following Fukushima Dai-ichi accident. Journal of Environmental Radioactivity 114:2–9, https://doi.org/10.1016/j.jenvrad.2011.11.015.
3. Behrens, E., F.U. Schwarzkopf, J.F. Lübbecke, and C.W. Böning. 2012. Model simulations on the long-term dispersal of 137Cs released into the Pacific Ocean off Fukushima. Environmental Research Letters 7(3):034004, https://doi.org/10.1088/1748-9326/7/3/034004.
4. Buesseler, K.O. 2012. Fishing for answers off Fukushima. Science 338:480–482, https://doi.org/10.1126/science.1228250.
5. Buesseler, K.O., M. Aoyama, and M. Fukasawa. 2011. Impacts of the Fukushima nuclear power plants on marine radioactivity. Environmental Science & Technology 45:9,931–9,935, https://doi.org/10.1021/es202816c.
6. Buesseler, K.O., S.R. Jayne, N.S. Fisher, I.I. Rypina, H. Baumann, Z. Baumann, C.F. Breier, E.M. Douglass, J. George, A.M. Macdonald, and others. 2012. Fukushima-derived radionuclides in the ocean and biota off Japan. Proceedings of the National Academy of Sciences of the United States of America 109:5,984–5,988, https://doi.org/10.1073/pnas.1120794109.
7. Buesseler, K.O., H.D. Livingston, S. Honjo, B.J. Hay, S.J. Manganini, E.T. Degens, V. Ittekkot, E. Izdar, and T. Konuk. 1987. Chernobyl radionuclides in a Black Sea sediment trap. Nature 329:825–828, https://doi.org/10.1038/329825a0.
8. Casacuberta, N., P. Masqué, J. Garcia-Orellana, R. Garcia-Tenorio, and K.O. Buesseler. 2013. 90Sr and 89Sr in seawater off Japan as a consequence of the Fukushima Dai-ichi nuclear accident. Biogeosciences 10:2,039–2,067, https://doi.org/10.5194/bg-10-3649-2013.
9. Charette, M.A., C.F. Breier, P.B. Henderson, S.M. Pike, I.I. Rypina, S.R. Jayne, and K.O. Buesseler. 2013. Radium-based estimates of cesium isotope transport and total direct ocean discharges from the Fukushima Nuclear Power Plant accident. Biogeosciences 10:2,159–2,167, https://doi.org/10.5194/bg-10-2159-2013.
10. Chartin, C., O. Evrard, Y. Onda, J. Patin, I. Lefèvre, C. Ottlé, S. Ayrault, H. Lepage, and P. Bonté. 2013. Tracking the early dispersion of contaminated sediment along rivers draining the Fukushima radioactive pollution plume. Anthropocene 1:23–34, https://doi.org/10.1016/j.ancene.2013.07.001.
11. Chino, M., H. Nakayama, H. Nagai, H. Terada, G. Katata, and H. Yamazawa. 2011. Preliminary estimation of release amounts of 131I and 137Cs accidentally discharged from the Fukushima Daiichi nuclear power plant into the atmosphere. Journal of Nuclear Science and Technology 48:1,129–1,134, https://doi.org/10.1080/18811248.2011.9711799.
12. Cochran, J.K. 1982. The oceanic chemistry of the U- and Th-series nuclides. Pp. 384–430 in Uranium Series Disequilibrium: Applications to Environmental Problems. M. Ivanovich and R.S. Harmon, eds, Clarendon Press, Oxford.
13. Davoine, X., and M. Bocquet. 2007. Inverse modelling-based reconstruction of the Chernobyl source term available for long-range transport. Atmospheric Chemistry and Physics 7:1,549–1,564, https://doi.org/10.5194/acp-7-1549-2007.
14. Doi, H., T. Takahara, and K. Tanaka. 2012. Trophic position and metabolic rate predict the long-term decay process of radioactive cesium in fish: A meta-analysis. PLoS ONE 7:e29295, https://doi.org/10.1371/journal.pone.0029295.
15. Estournel, C., E. Bosc, M. Bocquet, C. Ulses, P. Marsaleix, V. Winiarek, I. Osvath, C. Nguyen, T. Duhaut, F. Lyard, and others. 2012. Assessment of the amount of cesium-137 released into the Pacific Ocean after the Fukushima accident and analysis of its dispersion in Japanese coastal waters. Journal of Geophysical Research 117, C11014, https://doi.org/10.1029/2012JC007933.
16. Fisher, N.S., K. Beaugelin-Seiller, T.G. Hinton, Z. Baumann, D.J. Madigan, and J. Garnier-Laplace. 2013. Evaluation of radiation doses and associated risk from the Fukushima nuclear accident to marine biota and human consumers of seafood. Proceedings of the National Academy of Sciences of the United States of America 110:10,670–10,675, https://doi.org/10.1073/pnas.1221834110.
17. Fowler, S.W., and G.A. Knauer. 1986. Role of large particles in the transport of elements and organic compounds through the oceanic water column. Progress in Oceanography 16:147–194, https://doi.org/10.1016/0079-6611(86)90032-7.
18. Fowler, S.W., P. Buat-Menard, Y. Yokoyama, S. Ballestra, E. Holm, and H.V. Nguyen. 1987. Rapid removal of Chernobyl fallout from Mediterranean surface waters by biological activity. Nature 329:56–58, https://doi.org/10.1038/329056a0.
19. Hamilton, T.F., J.C. Milliès-Lacroix, and G.H. Hong. 1996. 137Cs(90Sr) and Pu isotopes in the Pacific Ocean: Sources and trends. Pp. 29–58 in Radionuclides in the Oceans: Inputs and Inventories. P. Guéguéniat, P. Germain, and H. Métivier, eds, EDP Sciences, Paris.
20. Hohenemser, C., M. Deicher, A. Ernst, H. Hofsäss, G. Lindner, and E. Recknagel. 1986. Chernobyl: An early report. Environment: Science and Policy for Sustainable Development 28:6–43, https://doi.org/10.1080/00139157.1986.9929911.
21. Honda, M.C., H. Kawakami, S. Watanabe, and T. Saino. 2013. Fukushima-derived radiocesium in western North Pacific sediment traps. Biogeosciences Discussions 10:2,455–2,477, https://doi.org/10.5194/bgd-10-2455-2013.
22. Hou, X., P.P. Povinec, L. Zhang, K. Shi, D. Biddulph, C.-C. Chang, Y. Fan, R. Golser, Y. Hou, M. Ješkovský, and others. 2013. Iodine-129 in seawater offshore Fukushima: Distribution, inorganic speciation, sources, and budget. Environmental Science & Technology 47:3,091–3,098, https://doi.org/10.1021/es304460k.
23. IAEA (International Atomic Energy Agency). 2004. Sediment Distribution Coefficients and Concentration Factors for Biota in the Marine Environment. IAEA Technical Report Series No. 422. Vienna, 103 pp.
24. Kanda, J. 2013. Continuing 137Cs release to the sea from the Fukushima Dai-ichi nuclear power plant through 2012. Biogeosciences Discussions 10:3,577–3,595, https://doi.org/10.5194/bgd-10-3577-2013.
25. Kawamura, H., T. Kobayashi, A. Furuno, T. In, Y. Ishikawa, T. Nakayama, S. Shima, and T. Awaji. 2011. Preliminary numerical experiments on oceanic dispersion 131I and 137Cs discharged into the ocean because of the Fukushima Dai-ichi nuclear power plant disaster. Journal of Nuclear Science and Technology 48:1,349–1,356, https://doi.org/10.1080/18811248.2011.9711826.
26. Kershaw, P., and A. Baxter. 1995. The transfer of reprocessing wastes from north-west Europe to the Arctic. Deep Sea Research Part II 42:1,413–1,448, https://doi.org/10.1016/0967-0645(95)00048-8.
27. Kusakabe, M., T.-L. Ku, K. Harada, K. Taguchi, and S. Tsunogai. 1988. Chernobyl radioactivity found in mid-water sediment interceptors in the N. Pacific and Bering Sea. Geophysical Research Letters 15:44–47, https://doi.org/10.1029/GL015i001p00044.
28. Kusakabe, M., S. Oikawa, H. Takata, and J. Misonoo. 2013. Spatiotemporal distributions of Fukushima-derived radionuclides in surface sediments in the waters off Miyagi, Fukushima, and Ibaraki Prefectures, Japan. Biogeosciences Discussions 10:4,819–4,850, https://doi.org/10.5194/bgd-10-4819-2013.
29. Livingston, H.D., and P.P. Povinec. 2000. Anthropogenic marine radioactivity. Ocean & Coastal Management 43:689–712, https://doi.org/10.1016/S0964-5691(00)00054-5.
    Madigan, D.J., Z. Baumann, and N.S. Fisher. 2012. Pacific bluefin tuna transport Fukushima-derived radionuclides from Japan to California. Proceedings of the National Academy of Sciences of the United States of America 109:9,483–9,486, https://doi.org/10.1073/pnas.1204859109.
30. MAFF (Ministry of Agriculture, Forestry and Fisheries). 2012. Radioactive Materials and Fish. Available online at: http://www.jfa.maff.go.jp/e/q_a/pdf/qa.pdf (accessed October, 2013).
31. Mitchell, P.I., O.M. Condren, L.L. Vintró, and C.A. McMahon. 1999. Trends in plutonium, americium and radiocaesium accumulation and long-term bioavailability in the western Irish Sea mud basin. Journal of Environmental Radioactivity 44:223–251, https://doi.org/10.1016/S0265-931X(98)00135-0.
32. Miyazawa, Y., Y. Masumoto, S.M. Varlamov, T. Miyama, M. Takigawa, M. Honda, and T. Saino. 2012. Inverse estimation of source parameters of oceanic radioactivity dispersion models associated with the Fukushima accident. Biogeosciences Discussions 9:13,783–13,816, https://doi.org/10.5194/bg-10-2349-2013.
33. Morino, Y., T. Ohara, and M. Nishizawa. 2011. Atmospheric behavior, deposition, and budget of radioactive materials from the Fukushima Daiichi nuclear power plant in March 2011. Geophysical Research Letters 38, L00G11, https://doi.org/10.1029/2011GL048689.
34. Nagao, S., M. Kanamori, S. Ochiai, S. Tomihara, K. Fukushi, and M. Yamamoto. 2013. Export of 134Cs and 137Cs in the Fukushima river systems at heavy rains by Typhoon Roke in September 2011. Biogeosciences Discussions 10:2,767–2,790, https://doi.org/10.5194/bg-10-6215-2013.
35. Nakano, M., and P.P. Povinec. 2012. Long-term simulations of the 137Cs dispersion from the Fukushima accident in the world ocean. Journal of Environmental Radioactivity 111:109–115, https://doi.org/10.1016/j.jenvrad.2011.12.001.
36. Oguri, K., K. Kawamura, A. Sakaguchi, T. Toyofuku, T. Kasaya, M. Murayama, K. Fujikura, R.N. Glud, and H. Kitazato. 2013. Hadal disturbance in the Japan Trench induced by the 2011 Tohoku–Oki Earthquake. Scientific Reports 3(1915), https://doi.org/10.1038/srep01915.
37. Pentreath, R.J. 1988. Sources of artificial radionuclides in the marine environment. Pp. 12–34 in Radionuclides: A Tool for Oceanography. Proceedings of an International Symposium Jointly Organized by the Société Française Pour l’Energie Nucléaire (SFEN) and l’Institut National des Techniques de la Mer (INTECHMER-CNAM), June 1987. J.C. Guary, P. Guegueniat, and R.J. Pentreath, eds, Elsevier, Cherbourg, France.
38. Povinec, P.P., A. Aarkrog, K.O. Buesseler, R. Delfanti, K. Hirose, G.H. Hong, T. Ito, H.D. Livingston, H. Nies, V.E. Noshkin, and others. 2005. 90Sr, 137Cs and 239,240Pu concentration surface water time series in the Pacific and Indian Oceans: WOMARS results. Journal of Environmental Radioactivity 81:63–87, https://doi.org/10.1016/j.jenvrad.2004.12.003.
39. Rossi, V., E. Van Sebille, A. Sen Gupta, V. Garçon, and M.H. England. 2013. Multi-decadal projections of surface and interior pathways of the Fukushima Cesium-137 radioactive plume. Deep Sea Research Part I 80:37–46, https://doi.org/10.1016/j.dsr.2013.05.015.
40. Rypina, I.I., S.R. Jayne, S. Yoshida, A.M. Macdonald, E. Douglass, and K. Buesseler. 2013. Short-term dispersal of Fukushima-derived radionuclides off Japan: Modeling efforts and model-data intercomparison. Biogeosciences Discussions 10:1,517–1,550, https://doi.org/10.5194/bgd-10-1517-2013.
41. Schwantes, J.M., C.R. Orton, and R.A. Clark. 2012. Analysis of a nuclear accident: Fission and activation product releases from the Fukushima Daiichi nuclear facility as remote indicators of source identification, extent of release, and state of damaged spent nuclear fuel. Environmental Science & Technology 46:8,621–8,627, https://doi.org/10.1021/es300556m.
42. Smith, J.N., K.M. Ellis, and L.R. Kilius. 1998. 129I and 137Cs tracer measurements in the Arctic Ocean. Deep Sea Research Part I 45:959–984, https://doi.org/10.1016/S0967-0637(97)00107-6.
43. Stohl, A., P. Seibert, G. Wotawa, D. Arnold, J.F. Burkhart, S. Eckhardt, C. Tapia, A. Vargas, and T.J. Yasunari. 2011. Xenon-133 and caesium-137 releases into the atmosphere from the Fukushima Dai-ichi nuclear power plant: Determination of the source term, atmospheric dispersion, and deposition. Atmospheric Chemistry and Physics Discussions 11:28,319–28,394, https://doi.org/10.5194/acpd-11-28319-2011.
44. Tateda, Y., D. Tsumune, and T. Tsubono. 2013. Simulation of radioactive cesium transfer in the southern Fukushima coastal biota using a dynamic food chain transfer model. Journal of Environmental Radioactivity 124:1–12, https://doi.org/10.1016/j.jenvrad.2013.03.007.
45. TEPCO (Tokyo Electric Power Company). 2013. Result of Radioactive Analysis around Fukushima Daiichi Nuclear Power Station. Available online at http://www.tepco.co.jp/en/nu/fukushima-np/f1/smp/index-e.html (accessed August, 2013).
46. Tsumune, D., T. Tsubono, M. Aoyama, and K. Hirose. 2012. Distribution of oceanic 137Cs from the Fukushima Daiichi Nuclear Power Plant simulated numerically by a regional ocean model. Journal of Environmental Radioactivity 111:100–108, https://doi.org/10.1016/j.jenvrad.2011.10.007.
47. Tumey, S.J., T.P. Guilderson, T.A. Brown, T. Broek, and K.O. Buesseler. 2013. Input of 129I into the western Pacific Ocean resulting from the Fukushima nuclear event. Journal of Radioanalytical and Nuclear Chemistry 296:957–962, https://doi.org/10.1007/s10967-012-2217-9.
48. US FDA (US Food and Drug Administration). 2005. Inspections, Compliance, Enforcement, and Criminal Investigations: CPG Sec. 560.750 Radionuclides in Imported Foods—Levels of Concern. Available online at http://www.fda.gov/ICECI/ComplianceManuals/CompliancePolicyGuidanceManual/UCM074576 (accessed August, 2013).
49. Yoshida, N., and J. Kanda. 2012. Tracking the Fukushima radionuclides. Science 336:1,115–1,116, https://doi.org/10.1126/science.1219493.

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