Concentration and vertical flux of Fukushima-derived radiocesium in sinking particles from two sites in the Northwestern Pacific Ocean
Concentration and vertical flux of Fukushima-derived radiocesium in sinking particles from two sites in the Northwestern Pacific Ocean
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DOI：
10.5194/bg-10-3525-2013
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发表时间：
2013-01-01
期刊：
影响因子：
4.9
通讯作者：
Saino, T.
中科院分区：
文献类型：
--
作者：
Honda, M. C.;Kawakami, H.;Saino, T.
2011年3月11日福岛第一核电站事故发生时，在北太平洋西部的两个站，即亚北极环流的K2站和亚热带环流的S1站，时间序列沉积物收集器正在收集沉降颗粒。2011年3月下旬和2011年4月上旬，在两个观测站500米和4810米处收集的沉降粒子中检测到了来自FNPP 1事故的放射性铯（Cs-134和Cs-137）。Cs-134和Cs-137的沉降速度在地表至500 m之间为22 ~ 71 m/d，在500 m至4810 m之间为>180 m/d。Cs-137浓度范围为0.14至0.25 Bq g（-1）干重。这些数值高于2011年4月采集的表层海水、悬浮颗粒物和浮游动物的数值。虽然放射性铯可能被吸附到粘土矿物上或掺入粘土矿物中，但Cs-134和成岩物质之间的相关性并不总是显著的;因此，与下沉颗粒相关的铯的形式仍然是一个悬而未决的问题。6月下旬在K2和7月下旬在S1的Cs-137总存量为0.5至1.7 Bq m（-2）。与截至2011年4月来自两个站点的Cs-137输入相比，根据表面Cs-137浓度和混合层深度估计，并假设观测到的Cs-137通量全年恒定，估计Cs-137从上层的去除率（在上层的停留时间）为0.3至1.5% yr（-1）（68至312 yr）。估计的去除率和停留时间与切尔诺贝利事故后以前报告的值相当（去除率：0.2- 1%，停留时间：130-390年）。
At two stations in the western North Pacific, K2 in the subarctic gyre and S1 in the subtropical gyre, time-series sediment traps were collecting sinking particles when the Fukushima Daiichi Nuclear Power Plant (FNPP1) accident occurred on 11 March 2011. Radiocesium (Cs-134 and Cs-137) derived from the FNPP1 accident was detected in sinking particles collected at 500 m in late March 2011 and at 4810 m in early April 2011 at both stations. The sinking velocity of Cs-134 and Cs-137 was estimated to be 22 to 71 m day(-1) between the surface and 500 m and >180 m day(-1) between 500 m and 4810 m. Cs-137 concentrations varied from 0.14 to 0.25 Bq g(-1) dry weight. These values are higher than those of surface seawater, suspended particles, and zooplankton collected in April 2011. Although the radiocesium may have been adsorbed onto or incorporated into clay minerals, correlations between Cs-134 and lithogenic material were not always significant; therefore, the form of the cesium associated with the sinking particles is still an open question. The total Cs-137 inventory by late June at K2 and by late July at S1 was 0.5 to 1.7 Bq m(-2) at both depths. Compared with Cs-137 input from both stations by April 2011, estimated from the surface Cs-137 concentration and mixed-layer depth and by assuming that the observed Cs-137 flux was constant throughout the year, the estimated removal rate of Cs-137 from the upper layer (residence time in the upper layer) was 0.3 to 1.5% yr(-1) (68 to 312 yr). The estimated removal rates and residence times are comparable to previously reported values after the Chernobyl accident (removal rate: 0.2-1%, residence time: 130-390 yr).