Effect of bentonite and ammonium-ferric(III)-hexacyanoferrate(II) on uptake and elimination of radiocaesium in reindeer

Eight male reindeer calves were used in two experiments to evaluate the effect of commonly used doses of two caesium binders, bentonite (25 g day(-1)) and ammonium-ferric(III)-hexacyanoferrate(II) (AFCF, 0.5 g day(-1)), on (A) the absorption of ingested radiocaesium, and (B) the rate of reduction of already absorbed radiocaesium. The animals were fed commercial reindeer feed and also, during Experiment A, lichens contaminated with radiocaesium. Radiocaesium levels in the animals were determined weekly. The excretion of Cs-137 in faeces and urine was measured during 3-day or 4-day periods on altogether seven occasions. The absorption factor of Cs-137 from lichens was reduced from 0.61, when no caesium binder was given, to 0.21 when the reindeer were given bentonite. AFCF appeared to prevent absorption almost completely. The biological half-life of radiocaesium was about 3 weeks when the reindeer were not given caesium binder. The addition of bentonite or AFCF to the diet seemed to reduce this half-life by at least 4 days.