Plutonium isotopes in the northwestern South China Sea: Level, distribution, source and deposition

• Published in: Environmental pollution (1987) 2022-04, Vol.298, p.118846-118846, Article 118846
• Main Authors: Zhang, Mengting, Qiao, Jixin, Zhang, Weichao, Zhu, Liuchao, Hou, Xiaolin
• Format: Article
• Language: English
• Subjects: 240Pu/239Pu atomic ratio; China; Deposition; Geologic Sediments; Pacific Proving Ground; Plutonium; Plutonium - analysis; Radiation Monitoring; Radioactive Fallout - analysis; Rivers; South China Sea; Water Pollutants, Radioactive - analysis
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2022.118846

The spatial distribution of plutonium isotopes (239Pu, 240Pu) in the surface sediments collected from the northwestern South China Sea (SCS) in 2018 was investigated. The 239,240Pu concentrations in surface sediments vary from 0.048 to 0.960 mBq/g (with mean of 0.282 ± 0.242 mBq/g) depending on the geographical feature of the sampling location such as the river estuary, continental shelf, slope and deep basin. Higher 240Pu/239Pu atomic ratios (0.24–0.31) in the surface sediment of the SCS compared to the global fallout value of 0.18 were observed, this is attributed to the input of close-in fallout of the Pacific Proving Ground (PPG) transported by the North Equatorial Current and Kuroshio Current to the northern SCS. The contribution of the PPG derived plutonium in the SCS sediment was estimated to be 39%–78% using a simple two-end member mixing model based on the measured 240Pu/239Pu atomic ratios in the sediment. Besides the soluble 239,240Pu level in seawater, load of suspended particulate matter from the river runoff and biological debris, hydrographic and hydrodynamic conditions are key parameters influencing the deposition process of plutonium to the sediment. [Display omitted] •Distribution of 239,240Pu and 240Pu/239Pu ratio in the SCS sediment were reported.•The close-in fallout of PPG contributed 39–78% of Pu in the SCS.•PPG derived Pu was transported to the SCS through NEC and KC.•Pu in the estuary sediment dominated by the global fallout Pu from the catchment.•Suspended particles and hydrodynamics influenced the deposition of Pu in the shelf.