The spatial variations of low-level ¹³⁴Cs concentrations (activities) in seawater off the Japanese Archipelago, particularly in the eastern East China Sea (ECS), in 2018 and 2019 were examined. The ¹³⁴Cs concentrations, decay-corrected to the date of the Fukushima Dai-ichi Nuclear Power Plant accident, in seawaters were 0.5–2.0 mBq/L. High ¹³⁴Cs concentrations (1.1–2.0 mBq/L) of the Kuroshio Current subsurface water (densities of 25–26σ_θ) in the eastern ECS could indicated the contribution of the subtropical mode water from the Pacific Ocean side, and total column inventories were 330–426 Bq/m². In contrast, as indicated by the same ¹³⁴Cs concentration level at the surface of the eastern ECS and Sea of Japan, larger portions of the subsurface waters remained in the ECS and Yellow Sea side in response to the existence of the shallow Tsushima Strait.

研究了2018年和2019年日本群岛以外，特别是东海东部（ECS）海水中¹³⁴ Cs浓度低水平（活动）的空间变化。在福岛第一核电站事故发生之前，经过海水衰变校正的¹³⁴ Cs浓度为0.5–2.0 mBq / L。高^134种黑潮地下水的铯浓度（1.1-2.0活度/ L）（25-26σ的密度_θ）在ECS东部可能表明从太平洋边的亚热带模式水的贡献，总列库存为330–426 Bq / m ²。相反，如相同的^134所示东ECS和日本海表面的Cs浓度水平，响应浅海的对马海峡的存在，大部分水下水留在ECS和黄海侧。