Numerical analysis of solute migration through fractured clayey deposits into underlying aquifers
- Univ. of Waterloo, Ontario (Canada)
This study examines the degree to which vertically fractured clayey aquitards protect an underlying aquifer from near-surface sources of contamination. Evidence from field studies indicates that many clayey aquitards previously assumed to be unfractured at depth have vertical fractures that actively transmit groundwater. Calculated groundwater velocities within these fractures can exceed several meters per day for apertures in the range of those reported to occur in clays. If this is the case, significant quantities of dissolved contaminants originating in near-surface zones may move rapidly downward through the fracture network into underlying aquifers. A two-dimensional Laplace transform Galerkin finite element model was used to assess the importance of idealized planar vertical fractures on flow and solute transport through a 15-m-thick aquitard and subsequent plume evolution within an underlying aquifer in which groundwater flows horizontally. Sensitivity analyses indicate that solute transport through the aquitard is strongly affected by downward flow in widely spaced deep fractures with apertures as small as 10 {mu}m and that a plume of large lateral extent and significant concentration forms within the underlying aquifer in a few tens of years for apertures of the order of 20 {mu}m or much sooner if the apertures are 50 {mu}m.
- OSTI ID:
- 5150110
- Journal Information:
- Water Resources Research; (United States), Journal Name: Water Resources Research; (United States) Vol. 28:2; ISSN 0043-1397; ISSN WRERA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
540220* -- Environment
Terrestrial-- Chemicals Monitoring & Transport-- (1990-)
AQUIFERS
CLAYS
CONTAMINATION
ENVIRONMENTAL TRANSPORT
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
GROUND WATER
HYDROGEN COMPOUNDS
INTEGRAL TRANSFORMATIONS
LAPLACE TRANSFORMATION
MASS TRANSFER
MATHEMATICAL MODELS
OXYGEN COMPOUNDS
PLUMES
POLLUTION
SOLUTES
TRANSFORMATIONS
WATER
WATER POLLUTION