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Dive into the research topics where Tony R. Lee is active.

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Featured researches published by Tony R. Lee.


Science of The Total Environment | 2014

Fifteen-year assessment of a permeable reactive barrier for treatment of chromate and trichloroethylene in groundwater.

Richard T. Wilkin; Steven D. Acree; Randall R. Ross; Robert W. Puls; Tony R. Lee; Leilani L. Woods

The fifteen-year performance of a granular iron, permeable reactive barrier (PRB; Elizabeth City, North Carolina) is reviewed with respect to contaminant treatment (hexavalent chromium and trichloroethylene) and hydraulic performance. Due to in-situ treatment of the chromium source zone, reactive and hydraulic longevity of the PRB has outlived the mobile chromate plume. Chromium concentrations exceeding 3 μg/L have not been detected in regions located hydraulically down-gradient of the PRB. Trichloroethylene treatment has also been effective, although non-constant influent concentrations of trichloroethylene have at times resulted in incomplete dechlorination. Daughter products: cis-1,2-dichloroethylene, vinyl chloride, ethene, and ethane have been observed within and down-gradient of the PRB at levels <10% of the influent trichloroethylene. Analysis of potentiometric surfaces up-gradient and across the PRB suggests that the PRB may currently represent a zone of reduced hydraulic conductivity; however, measurements of the in-situ hydraulic conductivity provide values in excess of 200 m/d in some intervals and indicate no discernible loss of bulk hydraulic conductivity within the PRB. The results presented here are particularly significant because they provide the longest available record of performance of a PRB. The longevity of the Elizabeth City PRB is principally the result of favorable groundwater geochemistry and hydrologic properties of the site.


Journal of Contaminant Hydrology | 2010

Iron hydroxy carbonate formation in zerovalent iron permeable reactive barriers: Characterization and evaluation of phase stability

Tony R. Lee; Richard T. Wilkin

Predicting the long-term potential of permeable reactive barriers for treating contaminated groundwater relies on understanding the endpoints of biogeochemical reactions between influent groundwater and the reactive medium. Iron hydroxy carbonate (chukanovite) is frequently observed as a secondary mineral precipitate in granular iron PRBs. Mineralogical characterization was carried out using X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and X-ray absorption spectroscopy on materials collected from three field-based PRBs in the US (East Helena, MT; Elizabeth City, NC; Denver Federal Center, CO). These PRBs were installed to treat a range of contaminants, including chlorinated organics, hexavalent chromium, and arsenic. Results obtained indicate that chukanovite is a prevalent secondary precipitate in the PRBs. Laboratory experiments on high-purity chukanovite separates were carried out to constrain the room-temperature solubility for this mineral. An estimated Gibbs energy of formation (Delta(f)G degrees) for chukanovite is -1174.4 +/- 6 kJ/mol. A mineral stability diagram is consistent with observations from the field. Water chemistry from the three reactive barriers falls inside the predicted stability field for chukanovite, at inorganic carbon concentrations intermediate to the stability fields of siderite and ferrous hydroxide. These new data will aid in developing better predictive models of mineral accumulation in zerovalent iron PRBs.


Journal of Contaminant Hydrology | 2009

Performance of a zerovalent iron reactive barrier for the treatment of arsenic in groundwater: Part 1. Hydrogeochemical studies.

Richard T. Wilkin; Steven D. Acree; Randall R. Ross; Douglas G. Beak; Tony R. Lee

Developments and improvements of remedial technologies are needed to effectively manage arsenic contamination in groundwater at hazardous waste sites. In June 2005, a 9.1 m long, 14 m deep, and 1.8 to 2.4 m wide (in the direction of groundwater flow) pilot-scale permeable reactive barrier (PRB) was installed at a former lead smelting facility, located near Helena, Montana (USA). The reactive barrier was designed to treat groundwater contaminated with moderately high concentrations of both As(III) and As(V). The reactive barrier was installed over a 3-day period using bio-polymer slurry methods and modified excavating equipment for deep trenching. The reactive medium was composed entirely of granular iron which was selected based on long-term laboratory column experiments. A monitoring network of approximately 40 groundwater sampling points was installed in July 2005. Monitoring results indicate arsenic concentrations >25 mg L(-1) in wells located hydraulically upgradient of the PRB. Of 80 groundwater samples collected from the pilot-PRB, 11 samples exceeded 0.50 mg As L(-1); 62 samples had concentrations of arsenic at or below 0.50 mg L(-1); and, 24 samples were at or below the maximum contaminant level (MCL) for arsenic of 0.01 mg L(-1). After 2 years of operation, monitoring points located within 1 m of the downgradient edge of the PRB showed significant decreases in arsenic concentrations at depth intervals impacted by the emplaced zerovalent iron. This study indicates that zerovalent iron can be effectively used to treat groundwater contaminated with arsenic given appropriate groundwater geochemistry and hydrology. The study also further demonstrates the shortcomings of hanging-wall designs. Detailed subsurface characterization data that capture geochemical and hydrogeologic variability, including a flux-based analysis, are needed for successful applications of PRB technology for arsenic remediation.


Journal of Hazardous Materials | 2003

Enhanced removal of DNAPL trapped in porous media using simultaneous injection of cosolvent with air: influencing factors and removal mechanisms

Seung-Woo Jeong; A. Lynn Wood; Tony R. Lee

Factors influencing dense non-aqueous phase liquid (DNAPL) removal by concurrent injection of cosolvent and air were evaluated using micromodels and visualization techniques. Cosolvent (ethanol/water) was injected simultaneously with air into glass micromodels containing residual perchloroethylene (PCE). Impacts of the air flow rates and PCE solubility in the remedial fluid on PCE removal processes were examined. Although two major processes, immiscible displacement and dissolution, may contribute PCE removal from porous media during cosolvent-air (CA) flooding, PCE displacement occurred only in the initial flooding period and was independent of the air flow rate and ethanol content. However, faster airflow through the porous medium improved remedial fluid distribution and dynamics and resulted in enhanced dissolution of the DNAPL. Dissolution rates were directly related to PCE solubility in the remedial fluid. Enhanced contact between cosolvent and DNAPL during CA flooding was observed in a non-homogeneous micromodel with random flow paths.


Journal of Hazardous Materials | 2002

Effects of pure and dyed PCE on physical and interfacial properties of remedial solutions

Seung-Woo Jeong; A. Lynn Wood; Tony R. Lee

Hydrophobic dyes have been used to visually distinguish dense non-aqueous phase liquid (DNAPL) contaminants from background aqueous phases and soils. The objective of this study was to evaluate the effects of a dyed DNAPL, 0.5 g Oil-Red-O/l of PCE, on the physical properties of remedial solutions: water, co-solvents (50, 70, and 90% (v/v) ethanol), and surfactants (4% (w) sodium dihexyl sulfosuccinate). This study compared the densities, viscosities, and interfacial tensions (IFTs) of the remedial solutions in contact with both dyed and undyed PCE. The presence of the dye in PCE substantially alters the IFTs of water and ethanol solutions, while there is no apparent difference in IFTs of surfactant solutions. The remedial solutions saturated with PCE showed higher viscosities and densities than pure remedial solutions. Solutions with high ethanol content exhibited the largest increases in liquid density. Because physical properties affect the flow of the remedial solutions in porous media, experiments using dyed DNAPLs should assess the influence of dyes on fluid and interfacial properties prior to remediation process analysis.


Environmental Science & Technology | 2007

In Situ Chemical Reduction of Cr(VI) in Groundwater Using a Combination of Ferrous Sulfate and Sodium Dithionite: A Field Investigation

Ralph D. Ludwig; Chunming Su; Tony R. Lee; Richard T. Wilkin; Steven D. Acree; Randall R. Ross; Ann Keeley


Environmental Science & Technology | 2007

Iron optimization for fenton-driven oxidation of MTBE-spent granular activated carbon

Scott G. Huling; Patrick K. Jones; Tony R. Lee


Remediation Journal | 2004

Microbial Responses to In Situ Chemical Oxidation, Six-Phase Heating, and Steam Injection Remediation Technologies in Groundwater

Ann Azadpour-Keeley; Lynn Wood; Tony R. Lee; Susan C. Mravik


Environmental Science & Technology | 2002

Enhanced Contact of Cosolvent and DNAPL in Porous Media by Concurrent Injection of Cosolvent and Air

Seung-Woo Jeong; and A. Lynn Wood; Tony R. Lee


Journal of Environmental Engineering | 2008

In Situ Source Treatment of Cr(VI) Using a Fe(II) -Based Reductant Blend: Long-Term Monitoring and Evaluation

Ralph D. Ludwig; Chunming Su; Tony R. Lee; Richard T. Wilkin; Bruce M. Sass

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Richard T. Wilkin

United States Environmental Protection Agency

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Seung-Woo Jeong

Kunsan National University

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Randall R. Ross

United States Environmental Protection Agency

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Steven D. Acree

United States Environmental Protection Agency

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A. Lynn Wood

United States Environmental Protection Agency

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Ann Azadpour-Keeley

United States Environmental Protection Agency

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Chunming Su

United States Environmental Protection Agency

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Douglas G. Beak

United States Environmental Protection Agency

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Lynn Wood

United States Environmental Protection Agency

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Ralph D. Ludwig

United States Environmental Protection Agency

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