Radionuclide Transport Facilitated by Polydispersed Pseudo-Colloids in the Fractured Rock Media

Abstract

One dimensional analytic transport model in the fractured rock media which incorporates advective-dispersive transport, sorption onto stationary solid medium, pseudo-colloid formation, polydispersity of colloids, and radioactive decay was developed by assuming equilibrium sorption of radionuclide and colloids onto the solid medium and constant concentration of natural colloids in the fracture. It was resulted from this model study that transport of radionuclides in a fractured rock medium was accelerated by the presence of colloids and the polydispersity of colloids increased the mobility of radionuclides in the fracture, although the maximum concentration was decreased, comparing to the case of monodispersed colloids. Also it was noted that the effects of pseudo-colloid formation constant and concentration of natural colloids are of great importance in the transport of colloids. This model study could help to evaluate the significance of colloid presence in groundwater and to assess the overall behavior of radionuclides in groundwater.

KEYWORDS:

• colloids
• pseudo-colloids
• natural colloids
• fractured rock
• polydispersed colloids
• log-normal distribution
• distribution coefficients
• radionuclide migration velocity
• dispersion
• diffusion