Natural colloids and suspended particles in the Whiteshell Research Area, Manitoba, Canada, and their potential effect on radiocolloid formation

Natural colloids (1-450 nm) and suspended particles (>450 nm) were characterized in groundwaters of the Whiteshell Research Area of southern Manitoba to evaluate their potential role in radionuclide transport through fractured granite. Data on particle concentrations, size distributions, compositions and natural radionuclide content were collected to predict radionuclide formation and to provide a database for future colloid migration studies. The concentrations of colloids, between 10 and 450 nm ranged between 0.04 and 1 mg/l. The concentrations of suspended particles, which require higher groundwater velocities for transport, varied from 0.04 to 14 mg/l. Colloid (10-450 nm) concentrations as low as these observed in Whiteshell Research Area groundwater would have a minimal effect on radionuclide transport, assuming that radionuclide sorption on colloids is reversible. If radiocolloid formation is not reversible, and radionuclide-containing colloids cannot sorb onto fracture walls, the importance of natural colloids in radionuclide transport will depend upon particle migration properties. (author)