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对南沙海域表层水中溶解态(<0.45μm)和颗粒态(>0.45μm)210Po和210Pb进行了研究.结果表明,南沙海域表层水中溶解态和颗粒态210Po平均比活度分别为0.61Bq/m3(n=24)和0.43Bq/m3(n=23).溶解态和颗粒态210Pb平均比活度分别为1.66Bq/m3(n=24)和0.23Bq/m3(n=23).颗粒态210Pb比活度约占总210Pb比活度的12%,与开阔大洋相应值吻合;而颗粒态210Po占总210Po的比例约40%,明显高于开阔大洋和富营养海域.根据稳态不可逆模型得到总210Po和210Pb的停留时间分别为0.82和1.16a.清除过程中210Po和210Pb的平均分馏因子由清除速率常数法和固-液分配系数法计算分别为5.42和6.69,揭示了210Po和210Pb从溶解相清除至颗粒相的过程中发生了明显的分馏.进一步的研究证明了南沙海域210Po和210Pb的分馏主要由微生物控制,与富营养海域的分馏机制不同:在富营养海域,浮游植物颗粒和粪粒充当210Po和210Pb清除和迁出过程的主要载体,210Po和210Pb的分馏主要发生于浮游植物颗粒和粪粒对两核素的清除过程;在寡营养南沙海域,由于浮游植物颗粒和粪粒的相对贫乏,使微生物对210Po的清除作用相对突出,并在此过程中使210Po和210Pb产生明显的分馏效应.这与寡营养的马尾藻海的研究结果极为相似,进一步证实寡营养海域和富营养海域210Po生物地球化学行为和循环路径的差异.这表明210Po可能是研究与微生物有关的海洋学过程,尤其是研究硫族元素(S,Se,Te和Po)生物地球化学循环的有用示踪剂.
210Po and 210Pb in the surface water of the Nansha Sea were studied.The results showed that the average specific activities of dissolved and particulate 210Po in the surface water of Nansha Sea were 0.61Bq / m3 (n = 24) and 0.43 Bq / m3 (n = 23) .The average specific activities of dissolved and particulate 210Pb were 1.66Bq / m3 (n = 24) and 0.23Bq / m3 210Pb specific activity accounted for about 12% of the total 210Pb specific activity, and consistent with the corresponding values of the open ocean; while the 210Po particle state accounted for about 40% of the total 210Po, significantly higher than the open ocean and eutrophic waters.According to the steady-state irreversible model The retention times of total 210Po and 210Pb were 0.82 and 1.16a, respectively.The average fractionation factors of 210Po and 210Pb during the removal were 5.42 and 6.69, respectively, by the clearance rate constant method and the solid-liquid partition coefficient method, revealing that the 210Po and 210Pb transitions from Fractionation of the dissolved phase to the particulate phase took place.Further studies have shown that the fractionation of 210Po and 210Pb in the Nansha Sea is dominated by microorganisms, which is different from the fractionation mechanism in the eutrophic waters. In the eutrophic waters, phytoplankton and Fecal pellets act as a major carrier for the removal and removal of 210Po and 210Pb The fractionation of 210Po and 210Pb mainly occurred during the scavenging of two nuclides by phytoplankton and fecal pellets. In the oligotrophic Nansha sea area, due to the relative lack of phytoplankton and fecal pellets, the scavenging effect of 210Po on microorganisms was relatively prominent, And 210Po and 210Pb produced obvious fractionation effects during the process, which is very similar to that of the oligotrophic Sargasso Sea, further confirming the difference of 210Po biogeochemical behaviors and cycling pathways between oligotrophic and eutrophic waters. This suggests that 210Po may be useful in the study of microbial-related oceanographic processes, especially useful tracers for studying biogeochemical cycling of chalcogenides (S, Se, Te and Po).