Valentine A. Nzengung
Associate Professor
Room 132, GGS Building
Department of Geology
The University of Georgia
Athens, GA 30602
Phone: 706-542-2699
e-mail: vnzengun@uga.edu
Education
Ph.D. Environmental Geochemistry, 1993, Georgia Institute of Technology, Atlanta, Georgia
M.S. Environmental Engineering, 1993, Georgia Institute of Technology, Atlanta, Georgia
B.Sc. Geology, Cum Laude, 1988, Georgia State University, Atlanta, Georgia
Research Interest
My research focuses on the development and evaluation of innovative technologies for the cleanup of water, sediment, and soils. Particular emphasis is placed on reaction kinetics, identification of transformation products, mass balance and pathway(s) analyses. Specifically, my ongoing research focuses on the following five technologies:
- Phytoremediation of chlorinated organics (such as hexachloroethane, perchloroethylene, trichloroethylene, carbon tetrachloride, DDT) and perchlorate (rocket fuel component).
- Monitored natural attenuation of contaminants.
- Abiotic transformation of organic contaminants using redox-manipulated aquifer materials.
- Preparation and characterization of organo-modified clays as more effective sorbents of organic contaminants.
- In-situ bioremediation process for perchlorate-contaminated soils and pilot testing at field sites. At the Longhorn Army Ammunition Plant in Karnack, Texas, we have successfully used biosolids for in-situ bioremediation of perchlorate-contaminated soils.
Phytoremediation is effective in treating livestock and poultry wastes, perchlorates, organic contaminants, and metal contaminated hazardous waste sites. Compared to other remediation approaches, phytoremediation is more acceptable to the public as the ecosystem is not destroyed during the cleanup process. I have screened many terrestrial and aquatic plants and identified suitable species for phytoremediation of the latter group of contaminants. The data generated from our laboratory studies, so far, has been valuable in the development of better environmental fate models by regulatory agencies, design, and field application of phytoremediation. We have coupled laboratory and field data from our analysis of plants used in a demonstration project at the Carswell Air Force base in Fort Worth, Texas, to provide a better understanding of phytoremediation processes and pathways for chlorinated organic solvents. Also, at a Naval Facility in Florida, we are coupling phyto-processes and natural attenuation to accelerate the cleanup of a shallow chlorinated solvent plume upwelling into a wetland and recreational lake.
My research also focuses on the sorption and degradation of organic pollutants. In sorption studies, I have determined the kinetic and equilibrium sorption of model petrochemicals and pesticides onto organo-modified clays. I have also studied the effects of organic cosolvents, solute properties and organoclay structure on the mechanism of sorption of hydrophobic organic chemicals (HOCs). Because organoclays are selective sorbents of HOCs, I am investigating the preparation of a nonselective organoclay.
The oxidation-reduction reactions of iron are important in natural settings because Fe(III) is the fourth most abundant element on earth and the most important electron acceptor following the onset of anoxic conditions in groundwater and sediments. My research group is investigating the enhanced degradation of oxidized organic contaminants (e.g., chlorinated aliphatics and aromatics) using redox-manipulated sediments. Aquifer material and soils are chemically treated with a bulk reductant (dithionite) to create reducing conditions. Specific interest is placed on the reaction kinetics, identification of degradation products and determination of mass balance. The advantages offered by this innovative approach are: (1) in-situ redox manipulation using dithionite enhances reductive dechlorination of chlorinated organics and immobilization of chromium, (2) the system can be easily optimized and regenerated, (3) no toxic end-products are generated, and (4) remediation costs are less than those of most conventional abiotic and biotic techniques.
Journal Publications
1. Nzengung, V. A. and Jeffers, P.M. 2001. Sequestration, phytoreduction, and phytooxidation of halogenated organic chemicals by aquatic and terrestrial plants. Special Issue International Journal of Phytoremediation, vol. 3, no. 1, pp. 13-40.
2. Nzengung, V. A., Castillo, R.M., Gates, W.P., Mills, G.L. 2001. Abiotic transformation of perchloroethylene in homogeneous dithionite solution and in suspensions of dithionite-treated clay minerals. Environmental Science & Technology, vol. 35, pp. 2244-2251.
3. Garrison, A. W., Nzengung, V. A., Avants, J. K., Ellington, J. J., Wolfe, N. Lee. 2000. Phytodegradation of p,p'-DDT and Enantiomers of o,p'-DDT. Environmental Science & Technology, vol. 34, pp. 1663-1670.
4. O'Niell, W., Nzengung, V. A., Noakes, J., Bender, J., Phillips, P. 2000. Biosorption and biodegradation of tetrachloroethylene and trichloroethylene using mixed-species microbial mats. Journal of Hazardous Substance Research. <http://www.engg.ksu.edu/HSRC/JHSR/vol2no2.pdf>
5. Nzengung, V. A., Wang, C., Harvey, G., 1999. Plant-mediated transformation of perchlorate into chloride, Environmental Science & Technology, vol. 33, pp. 1470-1478.
6. Nzengung, V. A., Wolfe, L.N., Rennels, D., McCutcheon, S.C. 1999. Use of aquatic plants and algae for decontamination of waters polluted with chlorinated alkanes, International Journal of Phytoremediation, vol. 1, no. 3, pp. 203-226.
7. Jeffers, P.M., Wolfe, N.L., Nzengung, V. A. 1998. Green Plants: A Terrestrial Sink for Atmospheric CH3Br, Geophysical Research Letters, vol. 25, no. 1, pp. 43-46.
8. Nzengung, V. A., Nkedi-Kizza, P., Voudrias, E. A. 1997. Organic cosolvent effects on sorption kinetics of hydrophobic organic chemicals by organoclays, Environmental Science & Technology, vol. 31, no. 5, pp. 1470-1475.
9. Nzengung, V. A., Voudrias, E.A., Nkedi-Kizza, P., Wampler, J.M., Weaver, C.E. 1996. Organic cosolvent effects on sorption equilibrium of hydrophobic organic chemicals by organoclays, Environmental Science & Technology, vol. 30, no. 1, pp. 89-96.
10. Voudrias, E.A, Nzengung, V. A., and Li, C. 1994. Removal of light nonaqueous phase liquids (LNAPLs) by flushing, Journal of Waste Management, vol. 14, no.2, pp. 115-126.
Invited Book Chapters and Conference Proceedings
1. Nzengung, V. A., O'Niell, W., Wolfe, N.L, Rennels, D.E., McCutcheon, S.C. 2000. Chapter 9: Removal of Halogenated Organic Compounds Dissolved in Water by Algae, Aquatic Plants and Microbial Mats. IN Phytoremediation: Scientific Advances to Manage Contamination by Organic Compounds. Editors: Steven C. McCutcheon and Jerald L. Schnoor (IN PREPARATION 2001.)
2. Susarla, S., and Nzengung, V. A. Chapter 25: Degradation of Perchlorate by Plants. IN Phytoremediation: Scientific Advances to Manage Contamination by Organic Compounds. Editors: Steven C. McCutcheon and Jerald L. Schnoor (SUBMITTED 2001.)
3. Nzengung, V. A., Wang C. 2000. Influences on Phytoremediation of Perchlorate Contaminated Water. American Chemical Society (ACS) Special Symposium Series: Perchlorate in the Environment. Editor: Urbansky. Kluwer Academic/Plenum Publishers, New York. Chapter 21, pp 219 - 229.
4. Nzengung, V. A., Wang C. and Stacey B. 2000. Phytotransformation Pathways and Mass balances for Chlorinated Alkanes and Alkenes. EPA's Phytoremediation State of the Science Conference. May 1-2, 2000, Boston, Massachusetts.
5. Nzengung, V. A., O'Niell, L.W., Adesida A. 2000. Treatment of Perchlorate Contaminated Water in Microbial Mat, Algae, and Ebb-and-Flow Hydroponic Bioreactors. Symposium Series: Case Studies in the Remediation of Chlorinated and Recalcitrant Compounds. Editors: Godage B. Wickramanayake, Arun R. Gavaskar, James T. Gibbs, and Jeffrey L. Means. Battelle Press, Columbus, Ohio. 2(7), Pp 101-106
6. O'Niell, W. and Nzengung, V. A. 2000. Treatment of Organic Contaminated water in Microbial Mat Bioreactors. Symposium Series: Bioremediation and Phytoremediation of Chlorinated and Recalcitrant Organics. Editors: Godage B. Wickramanayake, Arun R. Gavaskar, Bruce C. Alleman, and Victor S. Magar. Battelle Press, Columbus, Ohio. 2(4), Pp 347-252
7. Nzengung, V. A., Wang, C., Harvey, G., McCutcheon, S.C., and Wolfe, N.L. 1999. Phytoremediation of Perchlorate Contaminated Water: Laboratory Studies. Symposium Series: Fifth International Symposium on In Situ and On-Site Bioremediation: Phytoremediation. Editors; Leeson Andrea and B. C. Alleman. Battelle Press, pp 239-244.
8. Dhankher, O. P., Tucker, J., Nzengung, V. A., Wolfe, N.L. 1999. Isolation, Purification and Partial Characterization of Plant Dehalogenase-Like Activity from Waterweed (Elodea Canadensis). Symposium Series: Fifth International Symposium on In Situ and On-Site Bioremediation: Phytoremediation. Editors; Leeson Andrea and B. C. Alleman, Battelle Press, pp 145-150.
9. O'Niell, W., Nzengung, V. A., Noakes, J., Bender, J. and Phillips, P. 1998. Biodegradation of PCE and TCE Using Mixed-Species Microbial Mats. IN Bioremediation and Phytoremediation. Editors: G.B. Wickramanayake and Hinchee) Battelle Press, pp 233 - 237.
10. Arthur W. Garrison, Nzengung, V. A., Avants, J.K., Ellington, J., and Wolfe, N.L. 1997. Determining the Environmental Enantioselectivity of o,p'-DDT and o,p'-DDD. Proceedings of the 17th International Symposium on Chlorinated Dioxins and Related Compounds (Edited by Ronal Hites). Vol. 31, pp. 256 - 261.
11. Nzengung, V. A., Voudrias, E.A., Wampler, J.M. 1993. A Modified Clay as Adsorbent of an Organic Contaminant in Aqueous and Mixed-Solvent Systems, pp 387 - 391 IN Proceedings of the 48th Industrial Waste Conference, Purdue University, West Lafayette, Indiana (Ronald F. Wukasch, Editor), Lewis Publishers, Chelsea, Michigan, 876 P.
12. Nkedi-Kizza, P. and Nzengung, V. A., 1995. Use of the Cosolvency Model to Predict Sorption Kinetics and Equilibria of Diuron and Naphthalene on Organoclays. In Kearney Foundation of Soil Science International Conference Proceedings, Vadose Zone Hydrology: Cutting Across Disciplines pp. 107 - 108.
Invited Presentations of Research Papers
Nzengung, V. A., Wang, C. and Stacey Box. 2000. Phytotransformation Pathways and Mass balances for Chlorinated Alkanes and Alkenes. EPA's Phytoremediation State of the Science Conference. May 1-2, 2000, Boston, Massachusetts.
Nzengung, V. A., Heath, B., Mills, G. 1999. Enhanced degradation of perchloroethylene (PCE) and trichloroethylene (TCE) at the surfaces of dithionite-treated clay minerals and aquifer materials. USEPA-NERL, Athens, Georgia. March 18th, 1999
Nzengung, V. A. 1999. How clean is clean in hazardous waste sites remediation? Perimeter Adult Learning and Services (PALS), Dunwoody, Georgia. June 1st 1999.
Nzengung, V. A. 1998. Do plants have a role in the clean up of contaminated waste sites? August 10th, 1998. 20 Master Gardener Volunteers. Conyers, Georgia
Nzengung, V. A. 1998. Phytoremediation of perchlorate contaminated water. Briefing to Perchlorate Working Group at Wright Patterson Air Force Base, Dayton, OH. August 19th, 1998.
Nzengung, V. A. 1998. Phytoremediation of perchlorate contaminated water. Briefing to Perchlorate Working Group at Brooks Air Force Base, San Antonio, TX. December 16 -17th, 1998.
Nzengung, V. A., C. Wang, Harvey, G., McCutcheon, S.C., and Wolfe, N. L. 1998. Phytoremediation of perchlorate contaminated water. 4th Annual Strategic Environmental Research and Development Program (SERDP) Symposium, Washington, DC. December 1 - 3, 1998.
Harvey, G.J., Eberts, S., Vose, J., Nzengung, V. A., Lee, R., Jones, S. 1998. Phytoremediation of TCE in an Alluvial Aquifer: A Field Demonstration. 4th Annual Strategic Environmental Research and Development Program (SERDP) Symposium, Washington DC. December 1 - 3, 1998.
Nzengung V. A., Gates, W., Mills, G., Reyna, C. 1997. Enhanced degradation of tetrachloroethylene by redox-manipulated iron-bearing clays and aquifer material. 3rd Annual Strategic Environmental Research and Development Program (SERDP) Symposium, Washington DC. December 3 - 5, 1997.
Nzengung, V. A., McCutcheon, S.C., Wolfe, N. L. 1997. Remediation of a shallow ground water plume of PCE. TCE, DCE and VC at the Orlando Naval Training College, Orlando, FL. Annual USGS/DOD Environmental Conservation Hydrology Meeting in Charleston, SC.
Garrison, A. W, Nzengung, V.A., Avants, J. K., Ellington, J. J., and Wolfe, N. L. 1997. Determining the environmental enantioselectivity of o,p'-DDT and other pesticides. Environmental and analytical chemistry of chiral pollutants. Invited by Dr. Renee L. Falconer. SETAC 1997.
Nzengung, V. A., Wolfe, N. L., and Carreira, L. H. 1995. Plant-enzyme dechlorination of chlorinated organic compounds. EPA Symposium on Bioremediation of Hazardous Wastes: Research, Development, and Field Evaluations, The Rye Town Hilton, Rye Brook, NY. August 8 - 10, 1995.
Research Projects
1. Pilot scale in-situ bioremediation of perchlorate-contaminated soils at the Longhorn Army Ammunition Plant in Karnack, Texas. Funding by The United Sates Department of Defense - US Army Operations Support Command.
2. Phytoremediation of perchlorate contaminated soil and water. Funded by The United States Department of Defense - Wright Patterson Airforce Base, Dayton, Ohio.
3. Determination of nitroreductase activity in Elodea and nitroreductase isolation and purification. Funded by USEPA-NERL, Athens, Georgia.
4. Natural attenuation and phyto-based treatability studies for shallow groundwater plumes contaminated with chlorinated ethenes at the Naval Training Center, Orlando. Funded by US Navy Facilities Southern Engineering Command Division, Charleston, South Carolina.
5. Enhanced degradation of tetrachloroethylene (PCE) by dithionite-reduced clays and aquifer materials. Funded through DOE-SRS Soil Remediation Center Program.
6. Phytoremediation: Marine algae and plant mediated transformation of organic pollutants. Funded by DOE through a subcontract from Florida A & M University.
7. Phytoremediation at Carswell AFB, TX: Laboratory Characterization of Phyto-transformation Products of Tetrachloroethylene (PCE) and Trichloroethylene (TCE) and Perchlorate. Funded by The United States Department of Defense - Wright Patterson Airforce Base, Dayton, Ohio.
Student abstracts and presentations at national and international meetings
1. O'Niell, W. and Nzengung, V. A. 2000. Treatment of organic contaminated water in microbial mat bioreactors. Symposium Series. 2nd International Conference on Remediation of Chlorinated and Recalcitrant Compounds. Monterey, California, May 22-25, 2000.
2. Payne, D. and Nzengung, V.A. 1999. Chemically induced remediation of sediments contaminated with chlorinated aliphatics. 217th American Chemical Society National Meeting, Anaheim, California. March 21 - 25, 1999.
3. O'Niell, W., Nzengung, V.A., Noakes, J., Bender, J., Phillips, P. 1999. Sorption and transformation of tetrachloroethylene and trichloroethylene using mixed species microbial mats. Southeastern Geological Society of America Annual Meeting. Athens, Georgia March 25 - 27, 1999.
4. Heath, B., Nzengung, V.A., Mills, G. 1998. Transformation of perchloroethylene at the surface of dithionite-reduced clay minerals and iron oxides. 35th Annual Meeting of the Clay Minerals Society. Cleveland, Ohio. June 6 - 10, 1998.
5. O'Niell, W., Nzengung, V.A., Noakes, J., Bender, J., Phillips, P. 1998. Biodegradation of PCE and TCE using mixed-species microbial mats. First International Conference on Remediation of Chlorinated and Recalcitrant Compounds. Monterey, California, May 18 - 21, 1998.
6. O'Niell, W., Nzengung, V.A., Noakes, J., Bender, J., Phillips, P. 1997. Bioremediation of PCE and TCE using mixed-species microbial mats. In Emerging Technologies in Hazardous Waste Management VIII Special Symposium, Pittsburgh, Pennsylvania, American Chemical Society (D.W. Tedder, Editor).
7. Castillo, R., Nzengung, V.A., Gates, W., Mills, G. 1997. Enhanced degradation of tetrachloroethylene by redox-manipulated iron-bearing clays and aquifer material. 213th American Chemical Society National Meeting. San Francisco, California. April 13-17, 1997, 37, 1, 180.
Research Facilities
Gas Chromatograph (Schimadzu) -- with electron capture and flame ionization detectors and autosampler
Gas Chromatograph (Hewlett Packard) -- with flame ionization and thermal conductivity detectors and autosampler
Gas Chromatograph (Hewlett Packard) -- with flame ionization and electron capture detectors and autosampler
Capillary Gas Chromatograph - Mass Spectrometer (Schimadzu) -- computer controlled with automatic sampler and automated data acquisition
Ion Chromatograph (DX-100) with UV and conductivity detectors -- computer controlled with autosampler and data acquisition
High Performance Liquid Chromatograph (DX -500) with UV and conductivity detectors - computer controlled with autosampler and data acquisition
Liquid Scintillation Counter (Beckman LS 5800LL Series) -- Windows for 14C-isotope and tritium analysis
Reactors for laboratory characterization of phytoremediation of volatile organics
Hydroponic plant growth chambers with traps for volatilized metabolites
Anaerobic Liquid Exchanger
Teaching Experience
Aqueous Environmental Geochemistry
Organic Contaminant Hydrogeology
Hazardous Waste Site Remediation
Environmental Instrumental Analysis
Coastal Processes and Conservation
Earth Processes and Environments