Effect of potassium ferric hexacyanoferrate in feed on ¹³⁷Cs uptake and excretion by silver Prussian carp

The present work documents potassium ferric hexacyanoferrate (KFCF) KFe[Fe(CN)₆] containing feed to be an effective and inexpensive countermeasure to reduce the ¹³⁷Cs contamination of fish. Laboratory aquarium experiments were performed to investigate the effect of feed containing potassium ferric hexacyanoferrate on ¹³⁷Cs uptake and excretion by silver Prussian carp (Carassius gibelio (Bloch, 1782)). After the 120-day period of ¹³⁷Cs uptake with feed, reaching equilibrium ¹³⁷Cs level in fish, fish in some aquariums received feeds containing either 0.1 % or 1 % KFCF for 180 days in combination with clean feed or with feed containing ¹³⁷Cs. These feeds resulted in 3.6 ± 0.7 and 4.4 ± 0.9 times, respectively, lower activity of ¹³⁷Cs in fish compared to control fish fed ¹³⁷Cs throughout the experiment and receiving feed without KFCF. Following the first 100 days with the KFCF containing feed, the ¹³⁷Cs level in fish fed contaminated feed was even lower than in fish receiving clean feed, with a half-life of ¹³⁷Cs activity in fish of only T_1/2 = 23-35 days. Using clean feed containing 0 %, 0.1 % and 1 % KFCF for 180 days after the 120-day ¹³⁷Cs uptake period, the excretion rates for ¹³⁷Cs activity in fish k_b^' were (6.4 ± 0.2)⋅10^-3 day^-1, (1.08 ± 0.08)⋅10^-2 day^-1, and (1.3 ± 0.1)⋅10^-2 day^-1, respectively (T_1/2 = 108 ± 3 days, 64 ± 5 days, and 53 ± 4 days). The decrease rates for ¹³⁷Cs activity concentrations in fish k_b were (8.4 ± 0.3)⋅10^-3 day^-1, (1.3 ± 0.1)⋅10^-2 day^-1, and (1.5 ± 0.1)⋅10^-2 day^-1, respectively (T_1/2 = 83 ± 3 days, 53 ± 4 days, and 46 ± 3 days). Our results demonstrate a statistically significant effect (p < 0.01) of KFCF on the excretion of ¹³⁷Cs from silver Prussian carp: T_1/2 decreased from 108 days with clean feeding to 53-64 days when KFCF is added.