Evaluation of the 226Ra transport by river sediments surrounding the Brazilian uranium mining and milling facilities

A study of the 226Ra contamination of the river sediments surrounding the Brazilian uranium mining and milling facilities was carried out. The non-detrital 226Ra concentrations were determined performing a 0.5 N HCl leaching. Some preliminary speciations experiments using Tessier's sequential extraction procedure were also carried out. 228Ra was used as a monitor of the natural variations. In general one could not observe increase in the non-detrital 226Ra fraction between the pre-operational and operational data. Additionally, speciations experiments have shown the exchangeable fraction to be the main one responsible for 226Ra content. Although the results indicate that the sediment is an important means of radium downstream transport, its availability suggests the soluble form to be the main path through the main foodchain. Attention must be paid to the release of 226Ra bound to barium sulphate from the chemical processing effluent since increments of that fraction were observed in bottom sediments. (author)