An experiment to test the addition of potassium to a non-draining lake as a countermeasure to ¹³⁷Cs accumulation in fish

¹ Institute of Geological Sciences, Kuprevich Str. 7, Minsk 220141, Belarus
² Centre for Ecology and Hydrology, Winfrith Technology Centre, Dorchester, Dorset DT2 8ZD, U.K.

Abstract

Lake Svyatoye, a non-draining (closed) lake in Belarus was selected for a whole-lake experiment into the effect of potassium on ¹³⁷Cs accumulation in fish. The lake is in a zone of ¹³⁷Cs contamination of more than 1,480 kBq/m², K⁺ concentration of the lake water (1.0 mg/l) prior to the experiment was relatively low, and ¹³⁷Cs activity concentration ranged from 3.8 to 4.9 Bq/l. Prior to the experiment, the ¹³⁷Cs activity concentrations in fish were amongst the highest of all aquatic systems affected by Chernobyl, being from 8.4 to 17.5 kBq/kg (wet weight) for rudd, from 12.4 to 16.7 kBq/kg for roach; from 58 to 105 kBq/kg for perch and up to 56 kBq/kg for pike. To study the effect of the dissolved K⁺ concentration upon ¹³⁷Cs accumulation and retention in fish, 14,535 kg of potassium fertilizer was spread over the ice cover of the lake. After the application of KCl fertilizer, the K⁺ concentration in the lake water increased to 10 mg/l. An increase of [K⁺] in water resulted, as expected, in an increase in ¹³⁷Cs activity concentration in water (to 9.55-15.1 Bq/l, with average 12.17 Bq/l), as a result of ¹³⁷Cs desorption from bottom sediments. In spite of the increase in ¹³⁷Cs in the water, the K⁺ addition resulted in a steady decrease of ¹³⁷Cs activity concentration in different fish species during the experiment (from 1998-2000) to approximately 30% to 50% of their original values.