Multi-Region Reactive Transport Due To Strong Anisotropy In Unsaturated Soils With Evolving Scales of Heterogeneity
EMSL Project ID
6290
Abstract
Standard practices for predicting reactive transport under unsaturated conditions do not account for the random heterogeneity and strong anisotropy that can be expected under the extremes of nonlinear flow behavior typical of the vadose zone at DOE site such as Hanford. Variable anisotropy, an extreme of nonlinear behavior, can both subdue and enhance predicted migration rates depending on local stratigraphy; enhance nonequilibrium flow; limit access to reactive surfaces; and lead to the costly over-engineering of remediation and risk-management strategies through its effect on lateral flow processes. Even though lateral flow has dominated every field experiment (both planned and unplanned) at Hanford, it is unaccounted for in all but a few models. Those models that consider this mechanism are formulated on the presumption that flow can be linearized and treated as a small perturbation to the unsaturated flow dynamics and, therefore, are in contradiction of our prevailing knowledge of field manifestations. In this project, we are investigating a range of microscopic flow structures, measuring their three-dimensional pore morphology, topology, and pore-scale anisotropy, with the goal of generating a hierarchical pore-scale model. These data will be used, with exactly specified physics, to simulate flow and transport and to find suitably averaged (up-scaled) parameters to describe macroscopic transport with continuum models. The core-scale properties will be used to parameterize large-scale continuum models (e.g. STOMP) to investigate the use of up-scaled parameters to transient flow processes that occur at spatial and temporal scales that are impractical to observe experimentally. Results of this study will bridge the gap between pore-scale fluid migration and field-scale displacement behavior and, thereby, will improve our prediction capability for systems characterized by strong anisotropy. Without improved conceptualizations, remediation and risk-management strategies will be over-engineered at great expense, and corrective and remedial actions will be indefensible. These simulations cannot be conducted on available workstations and successful completion of this work will rely on access to EMSL computing facilities. This work is currently funded under an Environmental Management Science (EMSP) grant through DOE's office of Science.
Project Details
Project type
Exploratory Research
Start Date
2003-12-19
End Date
2006-12-24
Status
Closed
Released Data Link
Team
Principal Investigator