Dynamics of ¹³⁷Cs uptake from water to Prussian carp (Carassius Gibelio)

The rate constants of ¹³⁷Cs uptake in Prussian carp (Carassius gibelio) from the water with a potassium content of 2 mg∙L ^-1 at T = 5 °C without feeding (k_w = 0.045 ± 0.001 day^-1 ), at T = 12 °C with «clean» feeding (0.046 ± 0.002 day^-1 ) and at T = 22 °C with «clean» feeding (0.062 ± 0.006 day^-1 ) were obtained in a series of aquarium experiments. The results showed that rates of ¹³⁷Cs uptake in fish from water without and with feeding did not significantly differ at different temperatures of water (T = 5 - 22 °C) and were two orders of magnitude lower than the rate constants of ¹³⁷Cs uptake in Prussian carp with feed in Chornobyl exclusion zone (11.4 ± 2.6 day^-1 ). This makes it possible to obtain products with ¹³⁷Cs content below the permissible level (150 Bq∙kg^-1 ) while providing fish with clean feeds even in the most radioactively contaminated reservoirs of the exclusion zone. A decrease in the potassium content in water from 2 to 0.2 mg∙L ^-1 (no feeding, T = 5 ± 1 °C) resulted in an increase in the rate of ¹³⁷Cs uptake into the fish from the water by 1.6 times. An increase in the potassium content in water by 10 times up to 20 mg L ^-1 resulted just in a decrease of 20 % in the rate. The levels of ¹³⁷Cs activity concentration in fish in contaminated water at temperatures below 10 °C will be two orders of magnitude lower compared to radioactive contamination of water in the summer season (T = 22 °C). This is extremely important for the correct prediction of fish contamination in the autumn-winter-spring period at a water temperature of less than 10 °C when some fish stop feeding. (author)