Uptake and distribution of radioruthenium in plants for the exposure pathway air/plants

Laboratory examinations were carried out in green vegetables and lettuce to determine the penetration and translocation behaviour of ruthenium compounds (RuO4, RuCl3, RuO2, Ru(NO)(NO3)3 labelled with Ru-106. Particular attention was focused on sorption and desorption (extraction by washing), translocation on leaf surfaces and within the distribution system as well as on the depth of penetration. Compound extractability, rather than being determined by ruthenium's chemical form, was largely dependent upon the kind of vegetable examined and the surface structure of its leaves. In all plants, desorption was seen to have reached a maximum after approx. 1 week. Translocation through leaf surfaces did not appear to take place, nor was Ru-106 seen to be moved from its binding sites within the distribution systems. Almost all of the ruthenium used was found in the upper 40 μm of the leaves, from which fact it was concluded that its uptake by plants is practicable negligible. Contaminated above-ground parts of plants may by cleansed by washing. Shifts of activity within the plant were not detected. Contaminated fruits can safely be eaten after removal of the peel, as can any leaves growing after contamination. The results obtained permit a reliable evaluation of ruthenium-related health hazards from the fallout of waste management plants. (HP)