We started monitoring the radiocesium released from Fukushima in the North Pacific surface water from May 2011 after the accident soon to June 2016, using the cruise of the Oshoro-maru of Hokkaido University. We found that the reducing rate from the ocean surface of ¹³⁷Cs regardless of the distance from Fukushima was almost constant at 0.0033 ± 0.0005 day⁻¹. This finding indicated that 96% of ¹³⁷Cs in the surface water over the North Pacific were removed by 1000 days after the accident from the surface water to the ocean interior excluding the decrease by radioactive disintegration.

中文翻译：

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东电福岛第一核电站事故后北太平洋地表水中放射性铯 137Cs 的降低率

我们从事故发生后不久的 2011 年 5 月至 2016 年 6 月，开始使用北海道大学的Oshoro-maru的巡航监测北太平洋地表水中从福岛释放的放射性铯。我们发现，无论距福岛有多远，海洋表面^{137 Cs 的减少率几乎恒定在 0.0033 ± 0.0005 天-1}。这一发现表明，在事故发生后 1000 天，北太平洋地表水中 96% 的¹³⁷ Cs 从地表水转移到海洋内部，不包括放射性分解造成的减少。