Washing of the spinach with water by the Nishizawa method resulted in the removal of about 13 ± 2% of the
131I and 45 ± 20% of the
134Cs and
137Cs. Removal rates of
131I of approximately 76 ± 3% after further washing with 1.2 wt% Na
2S
2O
4 for 2 days and 47 ± 2% washing with 10 wt% Na
2S
2O
4 for 2 days were obtained. These values agreed with the dissolution rates of
131I in the liquid used for washing within 2 to 3% error. The removal rates of
134Cs and
137Cs after washing with 1.2 wt% Na
2S
2O
4 for 2 days were 69 ± 47% and 100 ± 52%, respectively, which were in poor agreement with the corresponding dissolution rates. The removal rate of
131I after brief washing with 10 wt% Na
2S
2O
4 was negligible and the dissolution rate was 5 ± 2%. The removal rates of
134Cs and
137Cs for 10 wt% Na
2S
2O
4 increased from 26 ± 11% to 42 ± 11% and from 30±20% to 42 ± 20% after washing with Na
2S
2O
4 for 2 days. The high removal rates in 1.2 wt% Na
2S
2O
4 may be due to the effective reduction of the I
2 on the surface of the leaves by Na
2S
2O
4 (1.2 wt%) during the 2 day immersion, which occurred without the bleaching of the leaves and stalks, which occurred in the case of 10 wt% Na
2S
2O
4.
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