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Remediation & Closure Science Project/ Subsurface Science Tasks (Zachara/Freshly, EM-closure, PNNL Scope #47040). [was aka S & T Road Mapping for Needs From All Sources (PNNL Scope #30998)].

EMSL Project ID


Hanford Remediation and Closure Science Project

The Hanford Site Groundwater Protection Program, formerly the Groundwater/ Vadose Zone Integration Project, was established in 1997 to develop the integrated approach, technical capability, and scientific information needed to perform site-wide assessments of the potential effects of Hanford Site soil and groundwater contaminants on people and the ecology. To complete this mission, gaps in scientific understanding and technologies were identified, and research to close those gaps was initiated.

The S&T Project is conducting field and laboratory studies and developing and applying numerical models that:

- result in improved conceptual and numerical models of important aspects of contaminant the vadose zone

- include evaluations of water and contaminant movement at representative, contaminated, uncontaminated field sites and targeted investigations to define controlling physical processes, including recharge, lateral spreading, and contaminant attenuation

- provide focused laboratory experiments on waste-sediment interactions and chemical develop improved (multiphase reactive) transport models to forecast the future migration contaminants and to influence remedial actions

- provide opportunities to deploy and test advanced characterization tools and methodologies identify mechanisms and processes that control the depth and extent of contaminant.

Specific capabilities and projects involving EMSL instumentation include:

1. The wettability of a porous medium has a large effect on DNAPL retention either as a residual saturation in the vadose zone or as pools in saturated regions. It has been hypothesized that the wettability of key Hanford subsurface materials rich in calcium carbonate (e.g, caliche) may not be water wet but intermediate wet. Intermediate-wet materials have the potential to retain substantially more DNAPL than water-wet porous media. In addition, some remediation and characterization techniques are far less effective in intermediate-wet porous media. With S&T funding, a laboratory technique has been developed in FY2004 to measure wettability of porous materials. In FY 2005, the wettability of several Hanford materials will be determined.

2. A related hypothesis is that the wettability may have changed from water wet to intermediate wet due to surface active components in the disposed Hanford DNAPL (carbon tetrachloride mixture). In FY2005, the potential of wettability changes due to interfacial processes will be studied in laboratory experiments for a variety of Hanford materials and carbon tetrachloride mixtures..

3. Recent S&T research has demonstrated that considerable residual carbon tetrachloride may have been formed in the vadose zone. Research is needed to investigate removal of residual DNAPL due to natural volatilization as well as induced volatilization as a result of the soil vapor extraction remediation applied at the Hanford site. In FY 2005, volatilization processes of residual carbon tetrachloride mixtures will be studied in controlled laboratory column and flow cell experiments.

4. The Hanford DNAPL was co-disposed with large quantities of a very salty aqueous phase. The effects of aqueous phase co-disposal on DNAPL movement, residual saturation formation, dissolution and volatilization has received very limited attention. Through batch, column, and flow cell experiments, a theory will be developed that describes simultaneous flow and transport of both the salty aqueous phase and the Hanford DNAPL.

5. The extent of the current dissolved carbon tetrachloride plume in the groundwater is, to a large extent, governed by the sorption/desorption characteristics of the dissolved component. A focused research effort is initiated in FY2005 to determine equilibrium and kinetic partitioning behavior for carbon tetrachloride under various conditions and for pertinent Hanford materials.

6. The knowledge obtained in 1-5 will be implemented into the mulfifluid flow simulator STOMP (Subsurface Transport Over Multiple Phases).

7. Develop experimental data, process-level models, and up-scaling approaches to improve capabilities to model U(VI) transport in heterogeneous vadose zone and groundwater plumes

8. Time-resolved laser-induced fluorescence spectroscopy (TRLFS) and imaging spectromicroscopy (TRLFISM) to investigate the chemical speciation of uranyl in contaminated subsurface sediments and natural minerals

Project Details

Project type
Exploratory Research
Start Date
End Date


Principal Investigator

John Zachara
Pacific Northwest National Laboratory

Team Members

Thomas Wietsma
Environmental Molecular Sciences Laboratory

Nikolla Qafoku
Pacific Northwest National Laboratory

Zheming Wang
Pacific Northwest National Laboratory

Mart Oostrom
Pacific Northwest National Laboratory

Ravi Kukkadapu
Environmental Molecular Sciences Laboratory

Related Publications

Liu C, JM Zachara, N Qafoku, and Z Wang. 2008. "Scale-dependent desorption of uranium from contaminated subsurface sediments." Water Resources Research 44:W08413. doi:10.1029/2007WR006478
Oostrom M, JH Dane, and TW Wietsma. 2006. "A Review of Multidimensional, Multifluid Intermediate-scale Experiments: Nonaqueous Phase Liquid Dissolution and Enhanced Remediation." Vadose Zone Journal 5:570-598.