Polydisperse colloid transport in fractured media

The initial phase of the study analytically solves for the transport characteristics of finitely sized particle in a uniform aperture fracture. Results show that the larger the constituents of a colloid plume, the greater the mean plume velocity and the lesser the plume dispersion. Incorporating these parameters into analytical solutions for the transport of polydisperse colloid plumes in a uniform aperture fracture shows that not only does the size of the constituents affect the transport of the plume, but that a distribution of particle sizes increases the spreading of the plume.; Next, a new constant spatial step particle tracking equation is developed to solve for the transport characteristics of both monodisperse and polydisperse reactive colloids in a single fracture. Using both the traditional and the new particle tracking algorithms, the transport characteristics of colloid plumes in a uniform aperture fracture are investigated. Matrix diffusion and surface sorption characteristics are incorporated into the model. Both perfect sink and kinetic colloid sorption onto fracture surfaces are investigated. The finite size of a colloid particle as well as the size distribution of the colloid plume will implicitly change the transport characteristics of a plume as its constituents travel through a fracture, sorbs onto the fracture surface, or diffuses through the rock matrix.; As an extension to this, the parallel plate model is generalized to the more realistic case of polydisperse colloid transport in a fracture with spatially variable aperture. The fracture aperture spatial variability is considered a stochastic variable and finite differencing techniques are used to develop the flow field through each fracture. These flow fields are used as input data for the new particle tracking algorithm. Cumulative normalized number breakthrough curves for polydisperse colloid plumes are produced by repeatedly tracking a plume of particles through unique realizations of stochastically generated fractures and incorporating results into an ensemble average. Further, the effects of kinetic sorption of colloids onto the walls of a variable aperture fracture are studied. It is shown that not only does the variability in size of the polydisperse colloids affect their transport, but that the variability of the fracture aperture has a significant influence as well.