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We assessed the repeatability and reproducibility of methods for determining low dissolved radiocesium concentrations in freshwater in Fukushima. Twenty-one laboratories pre-concentrated three of 10 L samples by five different pre-concentration methods (Prussian-blue-impregnated filter cartridges, coprecipitation with ammonium phosphomolybdate, evaporation, solid-phase extraction disks, and ion-exchange resin columns), and activity of radiocesium was measured. The z-scores for all of the 137Cs results were within ± 2, indicating that the methods were a good degree of precision. The relative standard deviations (RSDs) indicating the reproducibility among different laboratories were larger than the RSDs indicating the repeatability in each separate laboratory.

We assessed the repeatability and reproducibility of methods for determining low dissolved radiocesium concentrations in freshwater in Fukushima. Twenty-one laboratories pre-concentrated three of 10 L samples by ve di erent pre-concentration methods (Prussian-blue-impregnated lter cartridges, coprecipitation with ammonium phosphomolybdate, evaporation, solid-phase extraction disks, and ion-exchange resin columns), and activity of radiocesium was measured. The z-scores for all of the 137Cs results were within ± 2, indicating that the methods were a good degree of precision. The relative standard deviations (RSDs) indicating the reproducibility among di erent laboratories were larger than the RSDs indicating the repeatability in each separate laboratory.

A large amount of radiocesium was released from the accident at Fukushima Daiichi Nuclear Power Plant of Tokyo Electric Power Company. The determination of dissolved and particulate radiocesium concentrations in water is important, which can be used as basic information for understanding the long-term radiocesium dynamics in the environment and the transfer of radiocesium to crops. Conventional quantitative methods include the evaporative concentration to the dryness method and the AMP method. These methods need to concentrate about 20–200 L of water due to the low concentration of the dissolved radiocesium. After the accident, several new methods, such as the Prussian blue filter cartridge method and the solid-phase disk method, have been developed and put to practical use. In this study, we carried out an accuracy evaluation test to assess five methods (i.e., the evaporative concentration to dryness method, the AMP method, the Prussian blue filter cartridge method, the solid-phase disk method, and the ion-change resin method) using 3 types of water samples containing 0.01-1.0 Bq L−1 of dissolved radiocesium. Our results showed that the z-scores of over 80 % of the measured data were within ±2 and their CVs in the range of 8-13 %, indicating good reproducibility of these methods.