人工放射性核素在珊瑚岛礁系统中的富集与评估

Assessment and Enrichment of Artificial Radionuclides in Coral Reef Ecosystems

珊瑚礁生态系统拥有较高的生物多样性,为人类提供了丰富的生物资源及生态服务功能与价值。我国多处滨海核电站周边存在造礁珊瑚,而南海珊瑚岛礁也是未来海上漂浮核电站重要的潜在应用场景。基于在珊瑚礁中^(14)C、^(90)Sr和^(137)Cs的已有研究,分析了珊瑚礁中关键人工放射性核素的研究动态,提出了基于核素在珊瑚骨骼与海水分配系数的分类原则,探索了低度(^(137)Cs)、中度(^(129)I)和高度(^(14)C>^(239+240)Pu>^(90)Sr,^(236)U)富集的三大类核素在珊瑚骨骼中的富集规律,利用欧盟的ERICA模型开展上述人工放射性核素和天然放射性核素^(210)Po对珊瑚虫的辐射剂量评估,定量计算不同核素对珊瑚虫的剂量率排序依次为^(14)C>^(90)Sr>^(137)Cs>^(239+240)Pu>^(236)U>^(129)I,发现珊瑚虫中人工放射性核素造成的总剂量率(4.73×10^(-4)μGy/h)显著低于天然放射性核素^(210)Po产生的剂量率(6.60μGy/h)和无影响的筛选基准水平(10μGy/h),说明人工放射性核素不会对珊瑚虫种群产生显著的电离辐射危害。系统探讨了人工放射性核素在海水和珊瑚骨骼中的活度水平、分配系数和剂量率,定量揭示了珊瑚岛礁系统中人工放射性核素的富集特征,可为滨海核电对周边造礁珊瑚的影响评估和未来海上漂浮型核电站在南海珊瑚岛礁应用场景下的珊瑚礁生态安全和岛礁居民辐射环境安全评估提供一定的技术支撑。

Coral reef ecosystems are characterized by high primary production and biodiversity,providing rich biological resources and valuable ecosystem goods and services for humans.Reef-building corals survive in coastal areas near several nuclear power plants in China.Additionally,coral islands can potentially support future applications of floating nuclear power plants in remote marine environments for energy supply.Although artificial radionuclides derived from nuclear power plants are released into coral reef ecosystems,there is limited information on the biogeochemical behavior of artificial radionuclides and their radiological impacts on coral reef ecosystems.In this study,key artificial radionuclides,including^(14)C,^(239+240)Pu^(90)Sr,^(236)U,^(129)I,and^(137)Cs,were carefully selected and comprehensively investigated from the perspectives of activity concentration,coral skeletonseawater distribution coefficient(K_(d)value indicating the ability of enrichment),and radiation dose rates derived from the ERICA model.Based on our previous studies on^(14)C,^(90)Sr,and^(137)Cs in coral reef ecosystems,we reviewed and analyzed the research progress on key artificial radionuclides,which were classified into low-level(K_(d)≤1 L/kg),medium-level(1 L/kg<K_(d)<1000 L/kg),and high-level(K_(d)≥1000 L/kg)enrichment groups according to the Kd value.The Kd values were ranked in descending order as^(14)C>^(239+240)Pu>^(90)Sr and^(236)U>^(129)I>^(137)Cs.The radiation dose rates of the above-mentioned artificial radionuclides and naturally occurring radionuclides of^(210)Po in coral polyps were simultaneously calculated using the ERICA tool and ranked in the order^(14)C>^(90)Sr>^(137)Cs>^(239+240)Pu>^(236)U>^(129)I.The total radiation dose rate of artificial radionuclides was estimated to be 4.73×10^(-4)μGy/h,which was much lower than the radiation dose rate of^(210)Po(6.60μGy/h)and the screening benchmark level of no effect(10μGy/h).Therefore,artificial radionuclides in the surface seawater of the South China Sea should not pose significant radiological risks to coral polyp populations.Overall,our results provide technical support for the assessment of nuclear safety in coral reef ecosystems in the context of the potential application of floating nuclear power plants in coral islands in the South China Sea.