Guan Yongjing, Wei Xiaomin, Wang Shenzhen, Lai Jianhui, Huang Chunping, Wang Shuyi, Wang Lingyi, Li Gang, Liu Zhiyong
Guangxi Key Laboratory for Relativistic Astrophysics, School of Physical Science and Technology, Guangxi University, Nanning 530004, China.
State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510300, China.
Mar Pollut Bull. 2025 Oct;219:118278. doi: 10.1016/j.marpolbul.2025.118278. Epub 2025 Jun 9.
Hydrodynamic conditions, material sources, and redox environments vary significantly across different bays. Plutonium, with multiple valence states and particle-reactive properties, exhibits sediment distribution patterns highly sensitive to environmental controls. The activity concentration and vertical distribution of Pu and Cs in sediments from six bays in the northern South China Sea (Zhanjiang Bay, Daya Bay, Leizhou Bay, Shantou Bay, Liusha Bay, Dapeng Bay) were analyzed with respect to local environmental conditions. The activity concentration of Pu and Cs in sediment cores were analyzed by SF-ICP-MS and γ spectrometry, respectively. Distinct Pu peaks were observed in the sediment cores, with Cs profiles showing similar vertical patterns. Activity concentration distributions differed markedly between the two radionuclides, showing inventory ranges of 14 Bq/m to 261 Bq/m for Pu and 480 Bq/m to 2888 Bq/m for Cs across the bays. The Pu/Pu atomic ratios indicated that 35 % to 66 % of Pu originated from the Pacific Proving Grounds (PPG) source. The advection-dispersion equation (ADE) model was employed to quantify transport parameters, yielding dispersion rates (D) and sedimentation rates (v) for Pu and Cs corresponding to the maximum deposition peak observed in 1963. Through ADE - model based fitting of the vertical distribution of Pu, v ranges from 0.12 ± 0.07 cm/a to 1.02 ± 0.07 cm/a, and D varies from 0.13 ± 0.01 cm/a to 1.15 ± 0.24 cm/a. The v value derived from the ADE model fitting of Cs exhibits a similar range to that of Pu.
不同海湾的水动力条件、物质来源和氧化还原环境差异显著。钚具有多种价态和颗粒反应特性，其沉积物分布模式对环境控制高度敏感。针对南海北部六个海湾（湛江湾、大亚湾、雷州湾、汕头湾、流沙湾、大鹏湾）的当地环境条件，分析了沉积物中钚和铯的活度浓度及垂直分布。分别采用 SF-ICP-MS 和 γ 能谱分析法对沉积物岩心中钚和铯的活度浓度进行分析。在沉积物岩心中观察到明显的钚峰值，铯的剖面显示出相似的垂直模式。两种放射性核素的活度浓度分布明显不同，各海湾钚的存量范围为 14 Bq/m 至 261 Bq/m，铯为 480 Bq/m 至 2888 Bq/m。钚/钚原子比表明，35%至 66%的钚源自太平洋试验场（PPG）源。采用平流扩散方程（ADE）模型量化输运参数，得出与 1963 年观测到的最大沉积峰值相对应的钚和铯的扩散率（D）和沉积率（v）。通过基于 ADE 模型对钚垂直分布的拟合，v 的范围为 0.12±0.07 cm/a 至 1.02±0.07 cm/a，D 的范围为 0.13±0.01 cm/a 至 1.15±0.24 cm/a。由铯的 ADE 模型拟合得出的 v 值与钚的 v 值范围相似。
