Labelling of fine sediment (phi < 62.5 microm) with 99mTc was achieved through laboratory experiments described in a previous work (Proceedings of an International Symposium on Isotope Techniques in Water Resources Development and Management. IAEA-SM-361/13, Vienna, Proceedings of the XIIIth Brazilian Symposium on Water Resources. Brazilian Association for Water Resources (ABRH), Belo Horizonte, paper 176, CD-rom (in Portuguese)). Comparative studies of the hydrodynamic behaviour of the labelled and unlabelled sediment, in order to validate the application of the labelled sediment in field studies, were further performed by means of sedimentation tests using the Andreasen pipette technique, and are presented here. Labelling without flocculation, which promotes the same sedimentation behaviour of the labelled and the natural sediment was only achieved using small quantities of SnCl2 dissolved in proportionately small volumes of HCI (0.3%), in the reduction of a 99mTcO4- eluted from a 99Mo generator.
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