Sources of plutonium isotopes and Cs in coastal seawaters of Liaodong Bay and Bohai Strait, China and its environmental implications.

In order to investigate the sources of plutonium in seawaters of Liaodong Bay and Bohai Strait, China, surface seawater samples were collected and analyzed for Pu and Cs by radiochemical separation combined with ICP-MS and γ-spectrometry, respectively. A large variation of Pu activities was observed, ranging from 1.993 to 29.677 mBq/m in the Liaodong Bay and from 0.932 to 10.183 mBq/m in the Bohai Strait. Cs activities showed little variation between the investigated locations, which was attributed to the different behavior characteristics of Pu and Cs in seawaters. The Pu/Pu atom ratios showed a significant variation between the Liaodong Bay (0.185) and Bohai Strait (0.225), indicating that Pu derived from the Pacific Proving Grounds might have been transported to the Bohai Strait but not yet to the Liaodong Bay, which could further provide valuable reference for evaluating the seawater exchange cycle between the Bohai Sea and Yellow Sea.