HR: 0830h
AN: H21E-0899    [PDF]
TI: Uncertainty in Characterization of Source Zone DNAPL Entrapment Architecture Using Mass Flux Measurements Due to Geologic Heterogeneity
AU: * Saenton, S
EM: ssaenton@mines.edu
AF: Center for Experimental Study of Subsurface Environmental Processes (CESEP), ESE, Colorado School of Mines, Golden, CO 80401-1887 United States
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
AB: The presence of dense non-aqueous phase liquids (DNAPL) in source zones in the subsurface generates continuous mass flux long after the initial spill. Observed dissolved concentration in a screened monitoring well downstream of a DNAPL source zone will provide very little information on the entrapment architecture that is needed to design effective remediation schemes. Non-intrusive techniques based on partitioning tracer methods will only provide volume estimates that are in error under complex entrapment architecture that may include pools. The possibility of using mass flux measurements downstream of the source zone to determine DNAPL entrapment architecture is investigated. Determination of locations where mass flux is generated within the source zone will assist in targeting the hotspots for DNAPL mass removal through remediation. Using stochastic methods, we have demonstrated that mass flux emanating from the entrapment zone is controlled largely by the vertical distribution of the DNAPL. The proposed method involves vertical sampling of the solute mass flux by collecting concentration and water flux data downstream of the source zone using multilevel samplers. The mass flux data are analyzed using an experimentally validated mass transfer model incorporated into MODFLOW and RT3D and inverse modeling using UCODE to determine DNAPL entrapment architecture as well as the hydrodynamically accessible mass in the source zone. The accuracy of the method in relation to the distance from the source zone where flux measurements are made and vertical distribution of the sampling ports is evaluated. This theoretical study also evaluated possible errors associated with uncertainty resulting from our inability to fully characterize the heterogeneity of the subsurface below the spill.
UR: http://cesep.mines.edu
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
DE: 1869 Stochastic processes
SC: Hydrology [H]
MN: 2003 Fall Meeting