This study examined the temporal variations in radiocesium concentration associated with sinking particles in the northeastern Japan Sea between September 2010 and July 2012. We analyzed sediment trap samples from this period after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in March 2011. Cesium-134 was detected in samples collected between May and July 2011 at a depth of 1100 m (4.2–11 mBq g-dry⁻¹) but not in other periods at 1100 m or deeper (3100 and 3500 m). These results confirmed the deposition of FDNPP-derived radiocesium on the surface water in the late April 2011, which rapidly sank with sinking particles to a depth of at least 1100 m, in the northeastern Japan Sea, about 40 days after the deposition in the North Pacific. If FDNPP-derived ¹³⁷Cs was excluded, no seasonal changes were detected in the ¹³⁷Cs activity concentration of the sinking particles, and the ¹³⁷Cs activity concentration of the particles increased with increasing depth. Judging from the concentration of ¹³⁷Cs of sinking particle and seasonal variation of total mass flux and organic matter content, the lithogenic particle seems to be important for radiocesium associated with sinking particles. These data also strongly suggest a difference in sinking features of particles between 2010–2011 and 2011–2012 deployments. Due to the existence of benthic front, shallow water (1100 m) and deep water (3500 m) are separated during 2010–2011 deployment, but in the winter of 2011–2012, this front disappeared and the particles in surface water seem to have sunk to the depth of 3100 m. The sinking velocity of the particles at 1100 m was estimated to be 33–62 m day⁻¹, with a mean sinking velocity of 43 m day⁻¹. These values were comparable to those estimated at depths shallower than 1000 m in the North Pacific after the FDNPP accident, or in the Mediterranean, North, and Black Seas after the Chernobyl accident.

这项研究调查了2010年9月至2012年7月日本东北海与下沉颗粒相关的放射性铯浓度的时间变化。我们分析了2011年3月福岛第一核电站事故发生后这段时期的沉积物陷阱样品。在2011年5月至2011年7月之间收集的样本中检测到铯134的深度为1100 m（4.2-11 mBq g-dry ^-1），但在其他时期未检测到1100 m或更深（3100和3500 m）。这些结果证实了FDNPP衍生的放射性铯在2011年4月下旬沉积在地表水上，并在下沉约40天后迅速沉没在日本东北部至少1100 m处的沉没颗粒中。太平洋。如果FDNPP衍生¹³⁷排除了Cs，未发现沉降颗粒的¹³⁷ Cs活性浓度有季节性变化，并且颗粒¹³⁷ Cs的活性浓度随深度的增加而增加。从浓度¹³⁷来看下沉粒子的Cs以及总质量通量和有机物含量的季节性变化，致石粒子对于与下沉粒子相关的放射性铯似乎很重要。这些数据还强烈表明，2010-2011年部署与2011-2012年部署之间粒子的下沉特征​​有所不同。由于存在底栖锋，因此在2010–2011年部署期间浅水（1100 m）和深水（3500 m）是分开的，但是在2011–2012冬季，该锋消失了，地表水中的颗粒似乎具有下沉至3100 m的深度。颗粒在1100 m处的下沉速度估计为33–62 m day ^-1，平均下沉速度为43 m day ^-1。这些值与FDNPP事故发生后北太平洋，或切尔诺贝利事故发生后地中海，北海和黑海中小于1000 m的深度的估计值相当。