Effect of different Prussian Blue compounds in feed on ¹³⁷Cs uptake and excretion by silver Prussian carp

This paper documents that adding different hexacyanoferrate compounds, commonly referred to as Prussian Blue (PB), to feed is an effective and inexpensive countermeasure to reduce contamination of fish with ¹³⁷Cs. Laboratory aquarium experiments were conducted to investigate the effects of feed containing either 0.1 % or 1 % ammonium ferric hexacyanoferrate (AFCF, NH₄Fe [Fe(CN)₆]), potassium ferric hexacyanoferrate (KFCF, KFe [Fe(CN)₆]), or Ferrocyn (mixture of 95 % ferric hexacyanoferrate (FCF, Fe₄ [Fe(CN)₆]₃) and 5 % KFCF) on the uptake and excretion of ¹³⁷Cs by silver Prussian carp (Carassius gibelio (Bloch, 1782)). The experiments lasted for 2 months at a constant water temperature of 24 ± 2 °C. In each aquarium, at 9 a.m., fish received 0.2 g of feed per day (about 0.2 % of fish weight) containing 19 ± 2 Bq of ¹³⁷Cs. In addition, at 3-4 p.m., fish in different aquariums received 0.8-1.0 g of feed (about 1 % day^-1) containing 0 %, 0.1 % or 1 % of different PB compounds. The use of feed with 0.1 % and 1 % of PB compounds resulted in a 1.8-2.1 and 2.2-2.8-fold decrease in ¹³⁷Cs in the fish body compared to the control group of fish receiving feed without PB compounds after one month of the experiment and a 2.3-3.0 and 2.8-3.7 decrease after two months (at the end of the experiments). The reduction factors when using PB compounds can reach maximum values, 5-10, when ¹³⁷Cs activities in the treated and control groups of fish reach the maximum (stable) levels. The method of feed granulation, dry or wet, did not affect the effectiveness of PB, and no statistically significant differences were found between the efficiencies of the studied PB compounds. The results obtained, along with the results of our previous studies, demonstrate that, unlike in mammals, the use of PB compounds in feed does not significantly reduce the resorption of radiocesium in the gut (by 1.4-1.8 times), but substantially reduces the effective half-life of ¹³⁷Cs activity in fish (from 100 to 16-28 days).