The dispersal of colloids in fractured rock

How far do colloids migrate in fractured rock. We present an analysis for colloid migration based on the derivation of macroscopic flow parameters for colloids in single fractures. Dispersion terms, flow rates, and dynamic sorption rates are derived and calculated, depending explicitly upon physical and chemical properties of the colloids, the groundwater, and the fracture. We use such data directly to make predictions of colloid penetration and dispersal. Being based on microscopic theoretical considerations, this approach does not rely on empirically defined KD's for colloid-rock adsorption, or quantitative estimates of dispersivities. We discuss a possible experimental approach to the validation of the present model, and hence to refining the current predictions, which are made on the basis of theory alone. The parameter values obtained will be used as input data for future radionuclide-colloid fracture transport models. The radionuclides are transported both in solution and sorbed to colloids. Thus, reliable estimates for flow rates and dispersion rates are required. This work has been funded by SKI as part of Project 90. 6 figs., 1 tab., 3 refs