HR: 10:20h
AN: H22C-01 INVITED     [Abstracts]
TI: Prediction of Mass Flux Emission From DNAPL Source Zones Using Up-scaled Models of Mass Transfer
AU: * Illangasekare, T H
EM: tillanga@mines.edu
AF: National Science Foundation, Hydrologic Sciences, 4201 Wilson Blvd, Room 785, Arlington, VA 22230, United States
AB: Organic waste chemicals that are in the form of dense non-aqueous phase liquids (DNAPLs), when released into the subsurface produce complex entrapment architecture containing pools and zones of residual saturation (ganglia and residues). A variety of factors contribute to the development of the DNAPL architecture and the subsequent mass transfer that occurs within the source zone, which eventually contributes to the plume development and longevity. Experimental and modeling studies were conducted to evaluate how source factors such as heterogeneity, soil texture, texture contrasts, entrapment architecture, entrapment morphology, source aging, source modification due to remedial action, composition of the DNAPL, and groundwater flow, contributes to mass transfer, with the goal of predicting the mass flux emission form source zones. The processes that incorporate these factors into simulation models are generally defined and characterized at scales other than the field scale where the predictions are to be made for remedial decision-making and site management. Questions as to which of these parameters are important and which have to be up-scaled when the mass transfer occurs under natural conditions and under remedial action had to be answered. The study involved the development of Gilland-Sherwood type empirical models for mass transfer at column scale. Experiments were conducted in intermediate-scale test systems under controlled conditions prior to, during and post remediation. The changes in the source zone architecture were accurately monitored using x-ray and gamma attenuation methods. DNAPL spills were conducted in test aquifers with different degrees of heterogeneity to create different entrapment architecture. Models of groundwater flow and transport coupled with various reaction packages simulating the physical, chemical and biological transformations that occur in source zone during remediation, were developed and validated. The hypothesis that Gilland-Sherwood empirical models developed for natural dissolution in conjunction with models of reaction and degradation kinetics associated with remediation could be used to predict mass transfer during and after remediation was tested. This knowledge in conjunction with modeling tools and experimental data were used to develop and validate an up-scaling method to simulate the field-scale effective mass transfer. The proposed technique uses dissolution parameters measured at the laboratory scale, parameters that describe the DNAPL entrapment architecture and the geostatistical parameters of the aquifer heterogeneity.
DE: 1828 Groundwater hydraulics
DE: 1829 Groundwater hydrology
DE: 1832 Groundwater transport
DE: 1846 Model calibration (3333)
DE: 1847 Modeling
SC: Hydrology [H]
MN: 2007 Joint Assembly