| The anthropogenic radionuclides 137Cs are mainly produced by atmospheric nuclear tests and unclear accidents,the main source of Pu in the ocean is from atmospheric nuclear test and the Pacific Proving Grounds input.Therefore,the radionuclides 137Cs and 239+24opu in the ocean are widely studied and are often used to evaluate the ocean radioactive contamination and trace the ocean process.Bohai as the enclosed sea in China,there is rare study about 137Cs in the seawater,and the 239+24opu activities in Bohai Sea have not been reported.So the human radionuclide in Bohai Sea still needs to be further studied.In this work,the surface seawater samples are collected from the coastal waters of Liaodong Bay and Shandong Peninsula.The activities of 137Cs and 239+240Pu are measured,the distribution is analyzed,and the source of Pu is identified according to the 240Pu/239Pu atom ratio.Besides,the similarities and differences of chemical behavior between 137Cs arnd 239+240Pu in seawater are obtained according to the ratio of 239+240pPu/131Cs.and also the relationships between 137Cs,239+240Pu and water mass in seawater are discussed.The study of anthropogenic radionuclides in the costal surface seawater of Liaodong Bay and Shandong Peninsula can provide important information for ocean radioactive pollution assessment and also can be used as the basic data for water mass movement.In addition,we also cited the data of 137Cs,239+240Pu and 240Pu/239Pu in the other marginal seas of China,the data are compared with the spatial distribution and temporal variation of the coastal waters of Liaodong Bay and Shandong Peninsula.What's more,the different chemical behavior of 137Cs and 239+240Pu in the study area and other marginal seas are analyzed,and the source of Pu in the nearby sea is systematically studied as well.The main results are as follows:(1)The mean activity of 137Cs in the coastal waters of Liaodong Bay is slightly higher than Shandong Peninsula,which may be affected by the seasonal variation of coastal flow and the input of Liaohe River Basin.The mean specific activity of 239+240pu in the Liaodong Bay is similiar to the mean 239+24oPu activity in Shandong Peninsula.(2)The source of Pu in the seawater of Liaodong Bay and Shandong Peninsula is different.The 240pPu/239Pu ratio in the surface sediments of the west coast(L3)of Liaodong Bay is 0.182+0.023,which may not have been affected by Pacific Proving Grounds(PPG);Pu of Liaohe estuary(L2)is mainly from the basin input;What's more,Pu of costal water in Dalian and the Shandong Peninsula(L3)is effected by PPG.We use the end-member model to evaluate the proportion of Pu from this source,which is about 40.1%.(3)It is difficult to identify the source of seawater radionuclides according to the 239+240Pu/137Cs autom ratio.Because 239+24oPu is susceptible to the removal of particulate matter in water,1nd meaIwhile 137Cs is not suitable for trace Cater mass movement in enclosed sea.(4)The activities of 137Cs and 239+240Pu in the coastal waters of Liaodong Bay and Shandong Peninsula are lower than those in the Yellow Sea and East China Sea.Besides,the precipitation rate of surface 137Cs in Bohai Sea is 0.0481 which is larger than other marginal seas.The high value is related to the turbidity and suspended particulate matter in Bohai Sea. |
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