HR: 16:30h
AN: H14B-03    [Abstracts]
TI: Scaling up a Conceptual Model of Matrix Diffusion from Laboratory to Field
AU: * Gwo, J
EM: jgwo@umbc.edu
AF: University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250 United States
AU: Mayes, M
EM: mayesma@ornl.gov
AF: Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831 United States
AU: Jardine, P
EM: jardinepm@ornl.gov
AF: Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831 United States
AB: For the movement of solutes in fractured rocks, it remains challenging to scale up laboratory experiment results and conceptual models to field scale studies. Heterogeneities in the field are often multiscale and more complex than those captured in undisturbed soil and rock columns. The objective of this research is to scale up a conceptual model derived from laboratory soil column experiments to a field tracer release study. The study site is located at Oak Ridge National Laboratory in eastern Tennessee, USA. For years, undisturbed soil columns obtained near the field site have been used in the laboratory to elucidate the effect of matrix diffusion on the movement of radioactive chemicals through fractured rocks and macroporous soils. Conceptual models thus derived have not been rigorously tested in the field until a recent field tracer release has been completed and the experiment results are analyzed. In particular, it has not been clearly demonstrated that matrix diffusion, a diffusive mass transfer process, is the dominating mechanism of moving solutes between fractures and the rock matrix under natural flow conditions. Previous studies have identified that, under transient flow conditions, advective mass transfer as a result of inter-pore-structure hydraulic gradients may also contribute to the movement of solutes between the fracture and rock matrix. Our results suggest that, at the field scale, matrix diffusion indeed dominates the movement of solutes into the rock matrix within the area of developed fracture networks that constitute a preferred flow path. However, it is likely that movement of solutes into bedrocks surrounding the preferred flow path is mainly a result of advection and dispersion through the microfractures in the bedrocks.
DE: 5104 Fracture and flow
DE: 3210 Modeling
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting