Temporal variations in ¹³⁴Cs and ¹³⁷Cs concentrations in seawater along the Shimokita Peninsula and the northern Sanriku coast in northeastern Japan, one year after the Fukushima Dai-ichi Nuclear Power Plant accident

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• 作者：Hisaki Kofuji ; Mutsuo Inoue
• 关键词：134Cs ; 137Cs ; Coastal seawater ; Northern Sanriku ; Fukushima Dai-ichi Nuclear Power ; Plant accident
• 刊名：Journal of Environmental Radioactivity
• 出版年：2013
• 出版时间：October, 2013
• 年：2013
• 卷：124
• 期：Complete
• 页码：239-245
• 全文大小：4005 K

文摘

Ninety-six seawater samples were collected between May 2011 and March 2012 at 6 sites along the Shimokita Peninsula and the northern Sanriku coast, 250-450?km north of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP). Cesium-134 and ¹³⁷Cs concentrations were determined by low-background ¦Ã-spectrometry. During May-June 2011, ¹³⁴Cs and ¹³⁷Cs concentrations in surface waters decreased from 1.0-2.8 to 0.7-1.5?mBq/L and from 2.1-3.9 to 1.9-3.0?mBq/L, respectively. These decreases were due to diffusion and advection in the ocean after atmospheric input of the FDNPP-derived radionuclides. However, in July-August 2011, the concentrations of both radionuclides in the water samples collected on the Pacific?side of the Shimokita Peninsula and the northern Sanriku coast exhibited 30-50-fold increases (¡«40?mBq/L for ¹³⁴Cs and ¡«50?mBq/L for ¹³⁷Cs) over concentrations observed at these sampling sites in June 2011 in contrast to the gradual decreases in the concentrations on the Tsugaru Strait side of the Shimokita Peninsula. These results suggest that radiocesium-contaminated waters offshore in the Pacific Ocean were transported to coastal regions along the Pacific side of the Shimokita Peninsula and the northern Sanriku coast by ocean currents.