Time Scales of DNAPL Migration in Sandy Aquifers Examined via Numerical Simulation
Article first published online: 30 NOV 2006
2006 National Ground Water Association
Volume 45, Issue 2, pages 147–157, March–April 2007
How to Cite
Gerhard, J. I., Pang, T. and Kueper, B. H. (2007), Time Scales of DNAPL Migration in Sandy Aquifers Examined via Numerical Simulation. Ground Water, 45: 147–157. doi: 10.1111/j.1745-6584.2006.00269.x
- Issue published online: 30 NOV 2006
- Article first published online: 30 NOV 2006
- Received February 2006, accepted August 2006.
The time required for dense nonaqueous phase liquid (DNAPL) to cease migrating following release to the subsurface is a valuable component of a site conceptual model. This study uses numerical simulation to investigate the migration of six different DNAPLs in sandy aquifers. The most influential parameters governing migration cessation time are the density and viscosity of the DNAPL and the mean hydraulic conductivity of the aquifer. Releases of between 1 and 40 drums of chlorinated solvent DNAPLs, characterized by relatively high density and low viscosity, require on the order of months to a few years to cease migrating in a heterogeneous medium sand aquifer having an average hydraulic conductivity of 7.4 × 10−3 cm/s. In contrast to this, the release of 20 drums of coal tar (ρD= 1061 kg/m3, μD= 0.161 Pa·s) requires more than 100 years to cease migrating in the same aquifer. Altering the mean hydraulic conductivity of the aquifer results in a proportional change in cessation times. Parameters that exhibit relatively little influence on migration time scales are the DNAPL–water interfacial tension, release volume, source capillary pressure, mean aquifer porosity, and ambient ground water hydraulic gradient. This study also demonstrates that low-density DNAPLs (e.g., coal tar) give rise to greater amounts of lateral spreading and greater amounts of pooling on capillary barriers than high-density DNAPLs such as trichloroethylene or tetrachloroethylene.