HR: 1330h
AN: H22C-0940    [PDF]
TI: Study of DNAPL Pool Morphology Using X-ray Attenuation to Evaluate Limitations of Partitioning Tracer Method in Complex Entrapment Architecture
AU: * Illangasekare, T H
EM: tissa@mines.edu
AF: Center for Experimental Study of Subsurface Environmental Processes (CESEP), ESE, Colorado School of Mines, Golden, CO 80401-1887 United States
AU: Moreno-Barbero, E
EM: emorenob@Mines.EDU
AF: Center for Experimental Study of Subsurface Environmental Processes (CESEP), ESE, Colorado School of Mines, Golden, CO 80401-1887 United States
AU: Hill, E H
EM: ed@eh3.com
AF: Center for Experimental Study of Subsurface Environmental Processes (CESEP), ESE, Colorado School of Mines, Golden, CO 80401-1887 United States
AB: Characterization of sites contaminated with organic waste chemicals that are in the form of DNAPLs (dense non-aqueous phase liquids) still remains a major challenge in the implementation of remediation schemes. The Partition Interwell Tracer Technique (PITT) has been proposed and used as a non-intrusive method for the estimation of total mass of DNAPL in source zones. PITT uses a suite of chemical tracers that are injected into the source zone and the tracer breakthrough curves that are retarded by the tracer partitioning into the entrapped DNAPL are analyzed to determine the average saturation. In existing methods, PITT data are analyzed assuming local equilibrium exists between phases. This assumption may not be applicable at heterogeneous sites that produce complex entrapment architecture that contains high saturation pools. The groundwater flows around pools due to the reduced aqueous relative permeability caused by entrapment. Bypassing water may reduce the contact between the tracer solution and the NAPL and saturation will be underestimated. However, discernable partitioning of tracer may occur in the transition zone of the pool where the saturation of DNAPL varies from full to residual. The purpose of this research is to study the morphology of DNAPL pools and evaluate under what conditions the PITT limits the mass estimate within a pool. As rate limited behavior is expected within the transition zone, PITT under of rate limited partitioning was evaluated. X-ray attenuation provides an effective way to non-destructively measure the saturation distribution of DNAPLs in the laboratory. The high accuracy and the resolution of this technique allows for the measurement of the spatila distribution of saturation within DNAPL pools. Based on experiments that involved the creation of pools with known volumes of DNAPL in a test cell, errors were evaluated by comparing estimates obtained from PITT and the x-ray measurements. The experimental data in conjunction with model analysis were used to make a determination of limitations of PITT technique for characterization of DNAPL source zones where a significant fraction may be entrapped in the form of high-saturation pools.
UR: http://cesep.mines.edu
DE: 0994 Instruments and techniques
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2003 Fall Meeting