Laboratory investigation of buoyancy-induced flow (plume sinking) during two-well tracer tests
- Oregon State Univ., Corvallis, OR (United States). Dept. of Civil Engineering
The occurrence of buoyancy-induced vertical flow (sinking) of a bromide (Br{sup {minus}}) tracer plume at small injection concentrations is investigated in transport experiments conducted in a large-scale physical aquifer model containing a homogeneous and isotropic sand pack. Two-well tracer tests are conducted using Br{sup {minus}} at concentrations ranging from 50 to 1,000 mg/l, corresponding to relative densities between 7.5 {times} 10{sup {minus}5} and 1.5 {times} 10{sup {minus}3}. Analysis of three-dimensional solute concentration data indicates that the center of mass of the Br{sup {minus}} plume was displaced downward as the denser tracer solution sank through the sand pack. Plume sinking occurred at all solute concentrations investigated; the magnitude of the vertical displacement increased with increasing Br{sup {minus}} concentration of the injected tracer solution. The dynamic collapse of the Br{sup {minus}} plume caused by buoyancy forces resulted in increased apparent transverse and longitudinal dispersivities. The results suggest that the possibility of buoyancy-induced flow must be considered when interpreting tracer tests conducted with anion concentrations as low as 50 mg/l. The occurrence of buoyancy-induced flows at such low relative densities also suggest that the phenomenon may be more widespread than is generally recognized.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 94287
- Journal Information:
- Ground Water, Vol. 33, Issue 4; Other Information: PBD: Jul-Aug 1995
- Country of Publication:
- United States
- Language:
- English
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