Wettability and mass transfer effects on flow and transport of mixed DNAPL in Hanford Site sediments
EMSL Project ID
25598
Abstract
Approximately 750,000 kg of DNAPL containing carbon tetrachloride (CCl4) was discharged to the vadose zone at the Hanford site. Assuming equilibrium partitioning among phases, an estimated 64% remains as a nonaqueous phase liquid (NAPL) in the vadose zone. However, the presence of DNAPL has not been observed in soil cores, and efforts to remove CCl4 using soil vapor extraction have resulted in removal of only 10% of the estimated original mass. These observations indicate that either the conceptual model used to calculate CCl4 mass is incorrect, or DNAPL volatilization during SVE is far below what one would expect. Recently, a DOE-ERSP project entitled: "Influence of wetting and mass transfer properties of organic chemicals in vadose zone materials on groundwater contamination by NAPLs" was funded (Werth, Valocchi, Oostrom, co-PIs). In this project, it was postulated that critical information on DNAPL mixtures using site-specific materials must be determined before an accurate conceptual model, and mass estimate of CCl4 distribution, at the Hanford site is possible. Specifically, new saturation-capillary pressure (S-P) data for relevant wastewater/DNAPL mixtures, and new constitutive relationships for DNAPL mass transfer are required to accurately describe the effects of chemical mixtures on DNAPL migration, entrapment, and volatilization. The wastewater and DNAPL mixtures discharged at the Hanford site contain chemicals with the potential to change surface wettability, and their proportions likely change over time due to reaction-facilitated aging. The specific objectives of the DOE-ERSP project are to accurately determine the migration, entrapment, and volatilization of organic chemical mixtures, and to determine the effect of these organic chemical mixtures on surface wettability and CCl4 volatilization rates.We propose a combination of experimental and modeling activities to achieve our project objectives. Our experimental efforts focus on pore-scale analysis of wetting and mass transfer properties, capillary pressure - saturation (S-P) measurements, and on imaging DNAPL migration and entrapment in columns and intermediate-scale flow cells. The pore-scale studies will be conducted at the University of Illinois. For the S-P measurements, 1-D column and 2-D intermediate-scale studies, we propose to use the facilities at Subsurface Flow and Transport Laboratory (SFTL), which is part of the Environmental Molecular Sciences Laboratory (EMSL) at Pacific Northwest National Laboratory (PNNL). Our modeling efforts focuses on adding new constitutive equations and capillary pressure-saturation parameters to the existing Subsurface Transport Over Multiple Phases (STOMP) simulator (White and Oostrom, 2006), on modifying the code to account for multicomponent mixtures, and on validating the changes by comparison with the column and intermediate-scale flow cell experiments. In all experiments, we will use DNAPL mixtures that are similar to the ones discharged at the DNAPL disposal sites at Hanford. Where applicable, we will use Hanford materials including the Hanford coarse sand, fine sand, and Cold Creek caliche. The hydraulic properties will be determined using EMSLs Hydraulic Properties Apparatus, located in the SFTL.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2007-05-25
End Date
2009-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Brusseau ML, EL Difilippo, C marble, and M Oostrom. 2008. "MASS-REMOVAL AND MASS-FLUX-REDUCTION BEHAVIOR FOR IDEALIZED SOURCE ZONES WITH HYDRAULICALLY POORLY-ACCESSIBLE IMMISCIBLE LIQUID." Chemosphere 71(8):1511-1521.
Nellis S, H Yoon, C Werth, M Oostrom, and AJ Valocchi. 2009. "Surface and Interfacial Properties of Nonaqueous-Phase Liquid Mixtures Released to the Subsurface at the Hanford Site ." Vadose Zone Journal 8(2):344-351.
Oostrom M, MJ Truex, and GD Tartakovsky. 2009. "Three-Dimensional Simulation of Volatile Organic Compound Mass Flux from the Vadose Zone to Groundwater ." PNNL-SA-68431, Pacific Northwest National Laboratory, Richland, WA.
Schroth, M.H., M. Oostrom, R. Dobson, and J. Zeyer. 2008. "Thermodynamic model for predicting fluid/fluid interfacial areas in porous media for arbitrary drainage/imbibition sequences." Vadose Zone Journal 7(3): 966-971.
Werth CJ, C Zhang, ML Brusseau, M Oostrom, and T Baumann. 2010. "A Review of Non-Invasive Imaging Methods and Applications in Contaminant Hydrogeology Research." Journal of Contaminant Hydrology 113(1-4):1-24. doi:10.1016/j.jconhyd.2010.01.001
Yoon , H., C. J. Werth , M. Oostrom, and A. J. Valocchi . 2009. Estimation of interfacial tensions between organic liquid mixtures and water. Env. Sci. & Tech. 43(20): 7754-7761.
Yoon H, C Werth, AJ Valocchi, and M Oostrom. 2008. "Impact of nonaqueous phase liquid (NAPL) source zone architecture on mass removal mechanisms in strongly layered heterogeneous porous media during soil vapor extraction ." Journal of Contaminant Hydrology 100(1-2):58-71. doi:10.1016/j.jconhyd.2008.05.006
Yoon, H., M. Oostrom, T.W. Wietsma, A.J. Valacchi, and C.J. Werth. 2009. Numerical and experimental investigation of the impact of organic chemical mixtures on DNAPL migration and distribution in unsaturated porous media. Eos Trans. American Geophysical Union, 90(52), Fall Meet. Suppl., Abstract H13C-0981.
Yoon, H., M. Oostrom, T.W. Wietsma, C.J. Werth, and A.J. Valocchi. 2009. Numerical and experimental investigation of DNAPL removal mechanisms in a layered porous medium by means of soil vapor extraction. J. Contam. Hydrol. 109: 1?13.
Zhang, Z.F., M. Oostrom, and A.L. Ward. 2007. Saturation-dependent anisotropy in soil permeability for multi-fluid systems. Vadose Zone J. 6: 925-934.
Zhong, L., M. Oostrom, T.W. Wietsma, and M.A. Covert. 2008. Enhanced Remedial amendment delivery through fluid viscosity modifications: Experiments and numerical simulations. J. Contam. Hydrol. 101: 29-41, doi:10.1016/j.jconhyd.2008.07.007.