Biogeosciences Discuss., 10, 5223-5244, 2013
www.biogeosciences-discuss.net/10/5223/2013/
doi:10.5194/bgd-10-5223-2013
© Author(s) 2013. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Biogeosciences (BG). Please refer to the corresponding final paper in BG.
Cesium-134 and 137 activities in the central North Pacific Ocean after the Fukushima Dai-ichi nuclear power plant accident
J. Kameník1, H. Dulaiova1, K.O. Buesseler2, S. M. Pike2, and K. Št'astná3
1Department of Geology and Geophysics, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, 1680 East-West Road, Honolulu, HI-96822, USA
2Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA-02543, USA
3Department of Nuclear Chemistry, Czech Technical University in Prague, Břehová 7, 115 19 Prague 1, Czech Republic

Abstract. Surface seawater 134Cs and 137Cs samples were collected in the central and western North Pacific Ocean during the 1.5 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 134Cs that were impacted by Fukushima releases. Between March and May 2011, 134Cs was not detected around the Hawaiian Islands and Guam. Here, most 137Cs 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 18-month baseline established in surface seawater in Hawaii indicating that those might carry atmospheric fallout. The 18-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, 17 values). In contrast, samples collected between Japan and Hawaii contained 134Cs activities in the range of 1–4 Bq m−3 and 137Cs 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 1.5 yr at the main Hawaiian Islands due to the transport patterns across the Kuroshio and Kuroshio extension currents.

Citation: Kameník, J., Dulaiova, H., Buesseler, K.O., Pike, S. M., and Št'astná, K.: Cesium-134 and 137 activities in the central North Pacific Ocean after the Fukushima Dai-ichi nuclear power plant accident, Biogeosciences Discuss., 10, 5223-5244, doi:10.5194/bgd-10-5223-2013, 2013.
 
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