Colloid transport and retention in fractured deposits. 1997 annual progress report Page: 2 of 6
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The goal of this project is to identify the chemical and physical factors that control the
transport of groundwater colloids in fractured porous media and develop a generalized capability
to predict colloid attachment and detachment based on hydraulic factors (head, flow rate),
physical structure (fracture aperture), and chemical properties (surface properties of colloids and
fracture surfaces). Understanding the processes that control colloid behavior will increase the
confidence with which colloid-facilitated contaminant transport can be predicted and assessed at
various contaminated U.S. Department of Energy (DOE) sites. An added benefit is the
expectation that this work will yield novel techniques to either immobilize colloid-bound
contaminants in situ or mobilize colloids for enhancing remedial techniques such as pump-and-
treat and bioremediation.
A series of field-scale and laboratory-scale experiments, using both natural undisturbed
samples and simple one-dimension "artificial fractures," are in progress to investigate the
influence of physical and chemical factors on the transport of colloids in fractured materials. The
experimental results will be assessed using a computer model (COLFRAC) developed to
simulate colloid transport in fractured materials. The overall goal is to assess the relative
influence of chemical and physical factors expected to influence colloid transport in fractured
materials and investigate strategies for predictive simulation at the field scale. The experimental
methods each operate at different physical/geological scales and can be used with different
degrees of experimental control. This allows testing of hypotheses in a relatively simple setting
in the laboratory where individual chemical or colloidal characteristics can be varied and then the
results compared with field-scale experiments where the influence of realistic geologic
heterogeneity can be incorporated.
The work is organized into interacting tasks dealing with theoretical descriptions of colloid
transport in fractures, transport studies at three spatial scales (simple one-dimensional fractures,
laboratory columns of intact geological material, and field-scale colloid tracer studies), and
computer modeling of colloid transport processes. A continuing iteration among all tasks and
experimental scales is envisioned throughout the project.
Predictions based on laboratory experiments in simplified artificial fracture systems will be
tested in column and field studies, and, likewise, hypothesized interpretations of the results of the
column or field studies will be tested and verified in additional laboratory studies. Experimental
efforts at all scales will begin with simple binary comparisons (e.g., large vs small colloids with
similar surface chemistry), and proceed with increasing complexity (e.g., varying surface
properties of colloids or fractures) as understanding is developed. It is only through this parallel
iteration at different scales that predictions based on laboratory understanding can be tested in
column and in field studies so that additional research-can be conducted to resolve observations
that were not consistent with the earlier descriptions of controlling processes.
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McCarthy, J.F.; Reimus, P.; Ibaraki, Motomu; Wells, M.J.M. & McKay, L. Colloid transport and retention in fractured deposits. 1997 annual progress report, report, September 1, 1997; Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc619860/m1/2/: accessed April 19, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.