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We examined lateral distributions of 134 Cs, 137 Cs, 226 Ra, and 228 Ra in the surface seawaters around the Kuril Islands and the Kamchatka Peninsula in the northwestern North Pacific Ocean during June 2014. The sampling area included three water current areas, the Oyashio Current, the current from the Okhotsk Sea, and the coastal current along the east Kamchatka Peninsula. 226 Ra and 228 Ra distributions differed along the three currents. Low levels of 134 Cs were detected in the surface waters of the Oyashio Current (0.09–0.35 mBq/L), but it was <∼0.1 mBq/L at the surface along the other two currents. This indicates that the distribution of Fukushima Dai-ichi Nuclear Power Plant (FDNPP)-derived radiocesium in surface waters off the Kamchatka and along the Kuril Islands is predominantly governed by the Oyashio current system. [ABSTRACT FROM AUTHOR]

Abstract: A total of 82 surface seawater samples was collected in the Japan Sea and the southwestern Okhotsk Sea before and after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. Analysis of 134Cs and 137Cs concentrations using low-background γ-spectrometry revealed that the 137Cs concentration of the samples collected in June 2011 was 1.5–2.8mBq/L, which is approximately 1–2 times higher than the pre-accident 137Cs level, while the 134Cs concentration was less than detectable to 1mBq/L. In addition to 134Cs being clearly detected (∼1mBq/L), 137Cs concentration in water samples from the northeastern Japan Sea (2–2.8mBq/L) was also higher than that from the coast in the southwestern Japan Sea (∼1.5mBq/L). These higher concentrations in the northeastern Japan Sea could be ascribed to the atmospheric transport of nuclides from the FDNPP as aerosols and subsequent transport and dilution after delivery to the sea surface. [Copyright &y& Elsevier]