Cesium-134 and 137 activities in the central North Pacific Ocean after the Fukushima Dai-ichi Nuclear Power Plant accident

Abstract

Abstract. Surface seawater 134 Cs and 137 Cs samples were collected in the central and western North Pacific Ocean during the 2 yr after the Fukushima Dai-ichi Nuclear Power Plant accident to monitor dispersion patterns of these radioisotopes towards the Hawaiian Islands. In the absence of other recent sources and due to its short half-life, only those parts of the Pacific Ocean would have detectable 134 Cs values that were impacted by Fukushima releases. Between March and May 2011, 134 Cs was not detected around the Hawaiian Islands and Guam. Here, most 137 Cs activities (1.2-1.5 Bq m −3 ) were in the range of expected preexisting levels. Some samples north of the Hawaiian Islands (1.6-1.8 Bq m −3 ) were elevated above the 23-month baseline established in surface seawater in Hawaii indicating that those might carry atmospheric fallout. The 23-month time-series analysis of surface seawater from Hawaii did not reveal any seasonal variability or trends, with an average activity of 1.46 ± 0.06 Bq m −3 (Station Aloha, 18 values). In contrast, samples collected between Japan and Hawaii contained 134 Cs activities in the range of 1-4 Bq m −3 , and 137 Cs levels were about 2-3 times above the preexisting activities. We found that the southern boundary of the Kuroshio and Kuroshio extension currents represented a boundary for radiation dispersion with higher activities detected within and north of the major currents. The radiation plume has not been detected over the past 2 yr at the main Hawaiian Islands due to the transport patterns across the Kuroshio and Kuroshio extension currents.

Radiocaesium contaminated sites and possible techniques for remediation

“…Lots of measurements were between 2 and 6 PBq range (Miyazawa et al, 2013;Nair et al, 2014;Prime Minister of Japan & His Cabinet, 2011;Tsumune, Tsubono, Aoyama, & Hirose, 2012 Cs in winter 2012 approximately in one-to-one relationship (slope ¼ 1.009 ± .006) as shown in Figure 1 (Aoyama et al, 2012;Kameník et al, 2013;Kofuji & Inoue, 2013;Ramzaev et al, 2014 ).…”

“…Many efforts to measure and find data of Fukushima resulting radiocaesium contamination at surface and interior oceanic water are constant and some have been reported which showed transportation of Fukushima-derived radiocaesium into the North Pacific Ocean by surface currents. (Buesseler et al, 2012;Aoyama, Uematsu, Tsumune, & Hamajima, 2013;Kameník, Dulaiova, Buesseler, Pike, & Stastn, 2013;Kaeriyama et al, 2014;Kumamoto, Aoyama, Hamajima, Murata, & Kawano, 2015;Ramzaev et al, 2014 Cs (Inoue et al, 2012;Kameník et al, 2013;Ramzaev et al, 2014).…”

Lagrangian simulation and tracking of the mesoscale eddies contaminated by Fukushima-derived radionuclides

“…137 Cs and 134 Cs isotopes with 30.17 and 2.06 years half-life, respectively, were detected over a broad area in the western North Pacific in 2011 and 2012 (Honda et al, 2012;Buesseler et al, 2012;Inoue et al, 2012a, b;Tsumune et al, 2012Tsumune et al, , 2013Kaeriyama et al, 2013;Oikawa et al, 2013;Aoyama et al, 2013;Kameník et al, 2013;Kumamoto et al, 2014;Kaeriyama et al, 2014;Budyansky et al, 2015). 137 Cs concentration levels off Japan before the accident were estimated at the background level to be 1-3 mBq kg −1 , while 134 Cs was not detectable.…”

Risk assessment and distribution research of radionuclide Cs-134 for typical fishing ground in the North Pacific Ocean

“…By detecting the nuclear radiation content in marine organisms and further to estimate the radiation dosage content that human have received through the food chain transmission, so as to learn marine creatures concentration ability and regularity of different radiation is of great significance to estimate the biological radiation dosage rate and protect the health of ecological system [11].Domestic research on Fukushima accident radiation research and testing works is mainly focused on the safety of offshore aquatic products of china. At present our country to Japan Fukushima nuclear leakage radioactive influence on North Pacific high seas marine creatures is less reported, although some has reported [12], they are mainly aiming at the radionuclide content in the water.…”