Central Laboratory , Marine Ecology Research Institute , 300 Iwawada , Onjuku-machi, Isumi-gun , Chiba 299-5105 , Japan.
Environ Sci Technol. 2018 Mar 6;52(5):2629-2637. doi: 10.1021/acs.est.7b03956. Epub 2018 Feb 14.
Monitoring of Cs in seawater in coastal areas around Japan between 1983 and 2016 yielded new insights into the sources and transport of Fukushima Daiichi Nuclear Power Plant (FDNPP)-derived Cs, particularly along the west coast of Japan. Before the FDNPP accident (1983-2010), the activity concentrations of Cs, mainly from fallout, were decreasing exponentially. Effective Cs half-lives in surface seawater ranged from 15.6 to 18.4 yr. After the FDNPP accident (March 2011) Cs activity concentrations in seawater off Fukushima and neighboring prefectures immediately increased. Since May/June 2011, Cs activity concentrations there have been declining, and they are now approaching preaccident levels. Along the west coast of Japan remote from FDNPP (i.e., the Japan Sea), however, radiocesium activity concentrations started increasing by 2013, with earlier (May/June 2011) increases at some sites due to airborne transport and fallout. The inventory of Cs in the Japan Sea (in the main body of the Tsushima Warm Current) in 2016 was calculated to be 0.97 × 10 Bq, meaning that 0.44 × 10 Bq of FDNPP-derived Cs was added to the estimated global fallout Cs inventory in 2016 (0.53 × 10 Bq). The net increase of Cs inventory in the Japan Sea through the addition of FDNPP-derived Cs accounts for approximately 0.2% of the total Cs flux from the plant to the ocean from the accident.
1983 年至 2016 年期间，对日本沿海地区海水中的 Cs 进行监测，为了解福岛第一核电站（FDNPP）衍生 Cs 的来源和输运提供了新的认识，尤其是在日本西海岸。在 FDNPP 事故（1983-2010 年）之前，Cs 的活度浓度主要来自沉降物，呈指数衰减。海水中 Cs 的有效半衰期范围为 15.6 至 18.4 年。FDNPP 事故（2011 年 3 月）后，福岛及周边地区海水中 Cs 的活度浓度立即增加。自 2011 年 5/6 月以来，其浓度一直在下降，现已接近事故前水平。然而，远离 FDNPP 的日本西海岸（即日本海），Cs 放射性活度浓度自 2013 年开始增加，部分站点由于空气传播和沉降，2011 年 5/6 月浓度更早开始增加。2016 年，日本海（对马暖流主体部分）Cs 的库存量估计为 0.97×10 Bq，这意味着 2016 年 FDNPP 衍生 Cs 增加了 0.44×10 Bq，加入了全球沉降 Cs 库存（0.53×10 Bq）。通过添加 FDNPP 衍生的 Cs，日本海 Cs 库存的净增加量约占该事故中从核电站到海洋的 Cs 总通量的 0.2%。
