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内容記述 |
237Np (t1/2=2.14×106 y) has the potential to act as a tracer for water mass circulation for decadal and even longer time scales owing to its similar conservatism to 137Cs. Hence, we developed a new method for the determination of 137Cs, 237Np, and Pu isotopes in small volume (15?20L) seawater, including the 137Cs analysis using AMP adsorption method, separation ? purification of 237Np and Pu isotopes using anion exchange chromatography of AG MP-1M resin, and 237Np quantification using 242Pu as a pseudo isotope dilution tracer by SF-ICP-MS analysis. After Fe(OH)2 and CaF2/LaF3 co-precipitation, most of the matrixes were removed, and the interference U was efficiently separated from Pu isotopes and 237Np with a decontamination factor of 106 level. The negligible chemical fractionation between 237Np and 242Pu of 1.02 ? 0.06 (k=2) was obtained with sophisticated control of redox reaction and chromatographic elution optimization. The analytical results of IAEA-443 standard reference materials obtained by this method are in good agreement with the reference values, and the chemical yields of Np and Pu are as high as 76 ± 7%. Meanwhile, the low limits of detection of 237Np, 239Pu, and 240Pu were 1.3?10-3, 0.065, and 0.15 μBq L-1 for 15L seawater, respectively, which provides a powerful analytical method for studying marine material cycling using Np tracer and evaluating the impact of the marine discharge of Fukushima nuclear wastewater on marine ecological system, and the 237Np activity concentration in the Pacific Ocean seawater near the FDNPP was first reported to be 0.122?0.154 μBq L-1. |
