Colloid Transport Through Hanford Sediments Under Steady-State, Variably-Saturated Flow

We studied the transport of two types of colloids through variably-saturated Hanford sediments under well-controlled hydraulic conditions. The colloids are (1) native colloidal material (< 2 μm) separated from Hanford sediments, and (2) colloidal material (< 2 μm) separated from Hanford sediments that have been contacted with simulated Hanford waste tank liquors. These two types of colloids differed in their mineralogical composition. Transport of colloids through Hanford sediments was studied in packed laboratory columns in which water saturations were adjusted in 10% intervals, so that the effect of water saturation on colloid transport could be systematically evaluated. Results indicate that both native and waste-liquor-contacted colloids have a high mobility in Hanford sediments, but that mass of colloids transported decreased with decreasing water saturation. Water flow in the variably-saturated sediments corresponded well with the mobile-immobile water concept.