ARS | Publication request: INTERFACIAL AREA ESTIMATES FOR A NAPL-WATER SYSTEM AND THEIR EFFECT ON PREDICTING GROUNDWATER REMEDIATION EFFICIENCY

Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: November 1, 2005
Publication Date: November 1, 2005
Citation: Wildenschild, D., Bradford, S.A. 2005. Interfacial area estimates for a napl-water system and their effect on predicting groundwater remediation efficiency. EOS Transactions, Fall Meeting. 86:H33A-1372. American Geophysical Union.

Technical Abstract: In mass transfer relationships pertaining to immiscible contaminant clean-up, NAPL-water interfacial area is in many cases substituted by the total NAPL-blob surface area because the latter is much easier to measure with various imaging techniques. Apart from results obtained indirectly with interfacial tracer techniques, data on the NAPL-water interfacial area has been difficult to obtain. We have used high-resolution micro-tomography to image NAPL (Soltrol) and water distribution, and quantity, in a system of sintered glass beads. The interfacial areas between NAPL and water and for the total NAPL surface were calculated using various image processing techniques and the results show a significant difference between the NAPL-water and total NAPL interfacial areas. Using the total NAPL area as a proxy for the NAPL-water interfacial area results in an order of magnitude overestimation at low saturations and a factor 5 overestimation at high saturations. This has serious implications for modeled predictions pertaining to clean-up efficiency and resulting concentrations removed during a pump-and-treat clean-up scenario. We have incorporated the different interfacial area estimates in a numerical model (MISER) and simulated NAPL dissolution in a realistic porous medium to illustrate the magnitude of the potential error introduced by using the total NAPL area as a proxy for the NAPL-water interfacial area.