The Contribution of Sources to the Sustained Elevated Inventory of 137Cs in Offshore Waters East of Japan after the Fukushima Dai-ichi Nuclear Power Station Accident

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• 作者：Hyoe Takata ; Masashi Kusakabe ; Naohiko Inatomi ; Takahito Ikenoue ; Kazuyuki Hasegawa
• 刊名：Environmental Science & Technology
• 出版年：2016
• 出版时间：July 5, 2016
• 年：2016
• 卷：50
• 期：13
• 页码：6957-6963
• 全文大小：442K
• 年卷期：0
• ISSN：1520-5851

文摘

We have evaluated the contribution of sources of ¹³⁷Cs to the inventory of radiocesium in waters (surface area: 6160 km², water volume: 753 km³) off Fukushima Prefecture and neighboring prefectures from May 2011 to February 2015. A time-series of the inventory of ¹³⁷Cs in the offshore waters revealed a clearly decreasing trend from May 2011 (283.4 TBq) to February 2015 (1.89 TBq). The ¹³⁷Cs inventory about four years after the accident was approximately twice the background inventory of 1.1 TBq. The magnitudes of the ¹³⁷Cs influxes from sources into offshore waters for periods of 182–183 days were estimated from the first period (1 October 2011 to 31 March 2012: 15.3 TBq) to the last period (1 October 2014 to 31 March 2015: 0.41 TBq). We assumed that three sources contributed ¹³⁷Cs: continuous direct discharge from the Fukushima Dai-ichi Nuclear Power Station (FNPS) even after the massive discharge in late March 2011, desorption/dissolution from sediments, and fluvial input. Quantification of these sources indicated that the direct discharge from the FNPS is the principal source of ¹³⁷Cs to maintain the relatively high inventory in the offshore area.