HR: 0800h
AN: H31B-0378    [Abstracts]
TI: Pre and Post Treatment Characterization of DNAPL Source Zone Architecture in Heterogeneous Aquifers Using Mass Flux and Tracer Data
AU: * Kim, Y
EM: ykim@mines.edu
AF: Yongcheol Kim, Colorado school of mines, 1500 illinois street, golden, co 80401 United States
AU: saenton, s
EM: ssaenton@mines.edu
AF: Yongcheol Kim, Colorado school of mines, 1500 illinois street, golden, co 80401 United States
AU: Moreno-barbero, E
EM: emorenob@mines.edu
AF: Yongcheol Kim, Colorado school of mines, 1500 illinois street, golden, co 80401 United States
AU: Illangasekare, T H
EM: tissa@mines.edu
AF: Yongcheol Kim, Colorado school of mines, 1500 illinois street, golden, co 80401 United States
AB: Dense non-aqueous phase liquid (DNAPL) in source zones generates continuous mass flux long after the initial spill. Dissolved concentration observed in monitoring wells downstream of a DNAPL source zone alone provides very little information on the entrapment architecture that is needed to design effective remediation schemes. A method was developed to analyze measured vertical distribution of mass flux using a modified mass transfer model based on MODFLOW and RT3D and inverse modeling code PEST to determine DNAPL entrapment architecture as well as the hydrodynamically accessible DNAPL mass. This paper presents the validation of this method using experiments conducted in an intermediate-scale test tank. A 1.2 m high and 4.5 m long two-dimensional tank was packed with five test sands to represent a spatially correlated random field. The heterogeneity is characterized using the variance, correlation length and the anisotropy ratios in the vertical and horizontal directions. After wet-packing the tank, pressure measurements were made at 45 locations and a conservative tracer study was conducted to calibrate the flow and transport parameters of the test aquifer. A test DNAPL was spilled to create an entrapment zone. A tracer study using partitioning tracers was conducted for comparative purposes and to identify its limitations in characterizing source zones with complex entrapment architecture containing residual zones as well as pools. The DNAPL distribution was measured using a scanning gamma attenuation system. The solute mass flux emanating from the source zone and the tracer concentrations were monitored at multilevel observation ports placed downstream of the source zone at various distances. A surfactant flood was implemented to remove the entrapped DNAPL by enhancing dissolution. Flow by-passing as controlled by the heterogeneity of the aquifer as well as DNAPL entrapment will not produce complete mass removal, thus creating a different entrapment architecture that needed to be characterized to determine the treatment effectiveness. The same pre-treatment source zone characterization was implemented to determine the post-treatment state of the source zone. This comprehensive data set was used to validate the inverse modeling based characterization technique. The conclusions that are derived from this validations study are presented.
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting