Effect of biotite, zeolite, heavy clay, bentonite and apatite on the uptake of radiocesium by grass from peat soil

Biotite is a potassium rich mineral, which is used as a fertilizer in organ ic farming and as a soil amendment in conventional farming. Its ability to reduce Cs-134 uptake by ryegrass from peat soil was studied in pot experime nts and compared with zeolite, heavy clay, bentonite and apatite. In additi on, the long-term effect of biotite on Cs-137 uptake from peat soil was stu died in the peat field. In the pot experiments in the first cut of ryegrass, the minerals decreased Cs-134 uptake by plants in the following order: zeolite > heavy clay > ben tonite > biotite > apatite. Apatite did not have any effect on the plant Cs -134 level. In the later cuts, the uptake of Cs-134 from biotite-treated so il decreased further while that from soils treated with other minerals rema ined unchanged or even increased. In general, Cs-134 uptake by plants decre ased with increasing mineral level. The decrease of Cs-134 uptake became mo re efficient, especially at the early growth stage, by mixing small amounts of zeolite in biotite. The results of the field experiment indicated the l ong-term effect of biotite on reducing Cs-134 uptake by plants. Biotite app lication rate was 30 t ha(-1). The five-year mean of the plant/soil concent ration ratio of Cs-137 was 0.05 for biotite-treated soil, in contrast to 0. 14 for the control soil. On the whole, biotite reduced considerably the Cs- 137 level of plants on peat soil and this effect was long-lasting. For an e ffective reduction of plant radiocesium a great quantity of biotite is need ed and therefore it is most suitable for greenhouse cultivation where conta minated slightly decomposed peat is used as a growing medium.