A method of measurement of 239Pu, 240Pu, 241Pu in high U content marine sediments by sector field ICP-MS and its application to Fukushima sediment samples

An accurate and precise analytical method is highly needed for the determination of Pu isotopes in marine sediments for the long-term marine environment monitoring that is being done since the Fukushima Dai-ichi Nuclear Power Plant accident. The elimination of uranium from the sediment samples needs to be carefully checked. We established an analytical method based on anion-exchange chromatography and SF-ICP-MS in this work. A uranium decontamination factor of 2×106 was achieved and the U concentrations in the final sample solutions were typically below 4 pg mL-1, thus no extra correction of 238U interferences from the Pu spectra was needed. The method was suitable for the analysis of 241Pu in marine sediments using large sample amounts (> 10 g). We validated the method by measuring marine sediment reference materials and our results agreed well with the certified and the literature values. Surface sediments and one sediment core sample collected after the nuclear accident were analyzed. The characterization of 241Pu/239Pu atom ratios in the surface sediments and the vertical distribution of Pu isotopes showed that there was no detectable Pu contamination from the nuclear accident in the marine sediments collected 30 km off the plant site