Colloid Investigations in the ‘Pocos De Caldas” Natural Analogue Project

ABSTRACTPreliminary data are presented on colloids in groundwaters from two radioactive ore deposits (C-09 mine and Morro do Ferro) situated in the Pocos de Caldas plateau in the state of Minas Gerais, Brazil. Ultrafiltration with flat membranes of different nominal MW cutt-off limits (450 nm to 1, 000 dalton) was used to prepare colloid concentrates from 40 to 50 1 water samples. The colloidal retentates as well as the original groundwaters were analysed for relevant ‘major’ and trace element concentrations and for DOC. Distribution characteristics of elements like Si, Fe, Mn, DOC, U, Th and rare earths between colloidal phases and ‘solution’ as result of different groundwater chemistry will be discussed.