Final Report: Plant Assisted Remediation of Soil and Groundwater Contaminated by Hazardous Organic Substances: Experimental and Modeling Studies

EPA Grant Number: R825549C062
Subproject: this is subproject number 062 , established and managed by the Center Director under grant R825549
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: HSRC (1989) - Great Plains/Rocky Mountain HSRC
Center Director: Erickson, Larry E.
Title: Plant Assisted Remediation of Soil and Groundwater Contaminated by Hazardous Organic Substances: Experimental and Modeling Studies
Investigators: Davis, L. C. , Erickson, Larry E.
Institution: Kansas State University
EPA Project Officer: Hahn, Intaek
Project Period: May 18, 1995 through September 30, 2000
Project Amount: Refer to main center abstract for funding details.
RFA: Hazardous Substance Research Centers - HSRC (1989) RFA Text |  Recipients Lists
Research Category: Phytoremediation , Land and Waste Management


Specific objectives of the project as defined in 1994 include; 1) developing experimental systems to improve oxygen availability for enhanced aerobic biodegradation; 2) monitoring transfer and transformation of contaminants of interest through species of interest under steady state and transient conditions; 3) applying a mathematical model to describe the fate of water, contaminants, root exudates, microbes and oxygen in laboratory and field systems; 4) working with professionals elsewhere to try to apply this technology to one or more field sites. Progress was made in each of these four areas and is indicated below by objective number. Additional objectives, specific to the funding of project 94-27A, included understanding the way that plants can enhance degradation and dissipation of jet fuel, and the role that plants can play in degradation and removal of de-icer fluids including selected additives in those solutions.

Summary/Accomplishments (Outputs/Outcomes):

Much of the population in U.S. EPA Regions 7 and 8 relies on groundwater for its potable water, but many groundwater aquifers within this region have been contaminated with hazardous organic chemicals. Such chemicals may be by-products of agricultural and industrial production or may have leaked from fuel storage tanks or ruptured soil liners at disposal sites.

The soil contamination involved in these types of problems is often very dispersed so that conventional soil and groundwater remediation techniques would prove to be very expensive or in some cases impractical. Plants can play an important role in remediating soil and groundwater contaminated with organic substances. To put this new technology to effective use, we need to better understand and predict the effects that plants have on soil and groundwater remediation, so that effective planting and management plans can be developed.

Earlier this group reviewed the available literature related to the fate of organic substances in the plant's root zone. A prototype system has been built and used for study of bioremediation of groundwater assisted by plants. A model was developed to treat simple cases of a uniform gradient of root distribution, non-limiting oxygen supply, variable respirable substrate and biodegradation rates while including both infiltration and transpiration components of water flow.

Several publications have described the experimental and modeling studies. Extensive degradation of toluene and phenol was established. Significant breakdown of trichloroethylene has also been observed. Based on experience with the prototype system, a new system has been constructed with more (6) but shorter (1.15 m) path-length channels and a depth of 60 cm. It will permit introduction of controlled amounts of air into the soil, either above or below the water table, in two of the channels. By use of evolutionary operation design, the performance of the system will be optimized to minimize air input and maximize degradation of the target substances. Material balance measures will be used to determine the fate of target substances. Potential intermedia transfer will be monitored by FTIR measurements on the gas phase above the growing plants, while changes in contaminant concentration in the groundwater will be monitored by headspace gas chromatography or FT-IR of aqueous samples.

The groundwater flow and transport model, which was initially developed by John Tracy, has been used to give good fits to the flow behavior of a KBr tracer and toluene in the present prototype system. It will be used to model behavior of contaminants in the new system under several experimental conditions, including air supply near or below the water table. The model will be further refined, in collaboration with John Tracy, to improve the fit of predicted to observed behavior. It will then be applied to field situations where monitoring wells are in place, for instance near landfills.

1. PIant exposure. Our original prototype chamber planted with alfalfa was treated with TCE in groundwater for about 3 years, during which time the levels of contaminant escaping to the atmosphere via the soil surface diminished markedly. Loss may have occurred wither by degradation within the soil, or via transfer through plants. The rapid diffusive loss of contaminant from plants was confirmed.

A study with TCE fed to a cylinder from fall of 1998, showed transition to DCE release over several weeks after initial TCE release. Sunflowers planted in this cylinder during spring of 1999 had detectable levels of DCE in stem tissue. Concentrations rapidly decreased with distance above the soil surface.

A six-channel system was constructed in summer 1995. It uses # 304 stainless steel to form individual channels. Each of these is 110 cm long, 10 cm wide and 72 cm deep. Five of six channels were planted Nov 1, 1995 with field grown alfalfa from the site of initial soil collection. A bromide tracer experiment and two non-aqueous phase TCE treatment experiments were reported. More recently three cycles of experimentation with MTBE have been done, with plants and bacterial inoculants of potential MTBE degraders, +/- soil aeration. Previous modeling efforts had predicted that levels of TCE in water in the vadose zone diminish rapidly a short distance above the zone of capillary saturation, whereas for MTBE with a much smaller Henry constant the relative concentration in the water should remain high until quite close to the surface. Results from direct measurements on soil water indicate that this is indeed the case.

2a. Sorption to and transfer through plants. We have found that to accurately describe transient contaminant fluxes through plants it is necessary to consider the adsorption of contaminants within the plant. Modeling of flux of volatile, hydrophobic contaminants through stems can be reasonably approximated if the sorption is accounted for.

2b. Studies on JP-8. The jet fuel JP-8 is a complex mixture of hydrocarbons most relatively insoluble in water and only moderately volatile. It is defined on the basis of boiling point limits and is similar to kerosene. Our earlier work showed that JP-8 introduced in the unsaturated soil either in a two-channel system planted with alfalfa, or in cylinders unplanted or containing horseradish, was degraded almost completely within five months. Further studies were started using deeper placement of JP-8 into the water-saturated zone where oxygen supply would be very limited. Some cylinders were planted with alfalfa, while others remained unplanted. Later the alfalfa was replaced by grass. Two times of harvest have been completed. There is only modest loss of contaminant with or without plants, but with plants the upward movement and disappearance of contaminant is greater.

2b. Studies on de-icers. De-icers are of great interest in the vicinity of air fields because large amounts are used at some seasons of the year and they can penetrate to ground water. Although pure anti-freeze compounds such as ethylene or propylene glycol, are readily degraded, corrosion inhibitors and other additives are toxic to plants and microbes. For plants the main toxicity appears to be inhibition of root growth. This was studied with hydroponically grown sunflower plants. Tolerated levels of the corrosion inhibitors, benzotriazole (Bz) and methylbenzotriazole (MeBz), are about 0.05 g/L. This concentration would be present in a typical deicer stock diluted about 100-fold. Improving the analytical detection method for MeBz took significant effort because it is reactive with metals including the HPLC system being used for analysis. It was found that the system could be passivated by including a low concentration of MeBz in the HPLC eluant (70% MeOH), allowing for much higher resolution detection and elimination of tailing on the hydrophobic interaction column.

Studies have continued, using mainly sunflowers and fescue, to identify the mode of plant toxicity. Borate, which is important for lignin production does not appear to protect against the common corrosion inhibitor MeBz. Experiments have been done with varied supplementation of culture medium with trace elements including manganese, which is an essential constituent of the oxalate oxidase enzyme, which produces peroxide for lignin peroxidase. None of these supplements show marked improvement of plant tolerance to triazoles. Nutrient deficiency makes plants more susceptible.

An experiment was done to determine the level of glycols and de-icer that a stand of fescue can tolerate in the long term. Earlier studies had shown limits for the glycol and the MeBz independently. The deicer contains both, plus surfactants. Cylinders 15 cm in diameter and 45 cm deep are filled with a silty sand and planted with fescue. Continuous supply of 3 g/L of glycol is well tolerated for plants fed with Hoagland's nutrient solution. The triazole did not accumulate in the soil. Similar feeding of diluted deicer or antifreeze to alfalfa planted in two U-shaped channels by a drip irrigation system indicates that alfalfa also is able to tolerate 1% of standard strength deicer for several months with no noticeable decrease of growth rate.

3. Modeling. Two detailed papers by Muralidharan were published in Journal of Hazardous Substance Research, fully documenting our modeling efforts. These followed a number of papers describing the experimental system. Another paper, with N.K. Russell, compares an analytic solution to the finite element model for a one-dimensional vertical water transport case was published by the International Journal of Phytoremediation at the end of 1999. Our work on air dispersion of contaminants appeared in Environmental Progress at the end of 1999.

Zhang, in her Ph.D. dissertation, developed a relatively simple analytic model for loss of MTBE from alfalfa stems, using reasonable assumptions about the water content and flow to derive estimates of the radial diffusivity within the stem. Based on actual experimental measurements, we can provide a good fit, which predicts the extent of contaminant loss to the atmosphere via the plant. Papers describing her laboratory work and modeling studies are submitted.

We have worked with Riley County, Kansas engineering staff to assist them in developing plans for control of leaching at the recently closed Riley Co. landfill. On our advice, a large area downgradient of the landfill was planted to alfalfa. In the spring of 1997, some hybrid poplars and selected cultivars of cottonwoods were established in a nursery area. In 1998, 1999, and 2000, native cottonwood seedlings were planted. The trees are flourishing.

The results of this research are being communicated to interested parties through publications, presentations, and direct communication. We are working with Steve Rock at U.S. EPA to encourage communication among those who are conducting phytoremediation research and those who seek to implement phytoremediation at field sites. We have visited two field sited in the Kansas City area that are potential locations for phytoremediation. We have provided information to those responsible for these sited regarding the potential use of vegetation at each site and received some funding to support additional work at those sites. We have worked with a group of chemical engineering senior students on analysis and design of a phytoremediation solution to contaminated subsurface soil at one of the sites, a refinery site, which has been closed for a period of time. We participated in a planning meeting prior to planting trees at the site in the spring of 1998.
In 1998 and 1999, we worked with Peter Kulakow at KSU and Lucinda Jackson at Chevron to prepare materials for publication on phytoremediation. Chevron is interested in distributing information on phytoremediation, which will be useful to their employees and others. Chevron has provided some funding to help with this effort. A 12-page publication entitled "Plant System Technologies for Environmental Management in the Petroleum Industry" was prepared in 1999 and copies have been distributed by Chevron.

Journal Articles on this Report : 15 Displayed | Download in RIS Format

Other subproject views: All 112 publications 20 publications in selected types All 15 journal articles
Other center views: All 904 publications 230 publications in selected types All 182 journal articles
Type Citation Sub Project Document Sources
Journal Article Davis LC, Castro-Diaz S, Lupher D, Erickson LE. Interaction of benzotriazoles with upland plants. Environmental and Pipeline Engineering 2000:118-126 R825549C062 (Final)
not available
Journal Article Castro S, Davis LC, Erickson LE. Plant-enhanced remediation of glycol-based aircraft deicing fluids. Practice Periodical of Hazardous, Toxic and Radioactive Waste Management 2001;5(3):141-152. R825549C062 (Final)
not available
Journal Article Davis LC, Vanderhoof S, Dana J, Selk K, Smith K, Goplen B, Erickson LE. Movement of chlorinated solvents and other volatile organics through plants monitored by fourier transform infrared (FT-IR) spectrometry. Journal of Hazardous Substance Research 1998;1(4):1-26. R825549C062 (Final)
not available
Journal Article Erickson LE. An overview of research on the beneficial effects of vegetation in contaminated soil. Annals of the New York Academy of Sciences 1997;829:30-35. R825549C062 (Final)
not available
Journal Article Erickson LE, Zhang Q, Davis LC. Plant-based remediation of MTBE and other compounds in gasoline. Underground Tank Technology Update 2000;15(2):7-10. R825549C062 (Final)
not available
Journal Article Narayanan M, Davis LC, Erickson LE. Fate of volatile chlorinated organic compounds in a laboratory chamber with alfalfa plants. Environmental Science & Technology 1995;29(9):2437-2444. R825549C034 (Final)
R825549C062 (Final)
not available
Journal Article Narayanan M, Tracy JC, Davis LC, Erickson LE. Modeling the fate of toluene in a chamber with alfalfa plants. 1. Theory and modeling concepts. Journal of Hazardous Substance Research 1998;1(5):30. R825549C062 (Final)
not available
Journal Article Narayanan M, Davis LC, Tracy JC, Erickson LE. Modeling the fate of toluene in a chamber with alfalfa plants. 2. Numerical results and comparison study. Journal of Hazardous Substance Research 1998;1(5):28. R825549C062 (Final)
not available
Journal Article Narayanan M, Russell NK, Davis LC, Erickson LE. Fate and transport of trichloroethylene in a chamber with alfalfa plants. International Journal of Phytoremediation 1999;1(4):387-411. R825549C062 (Final)
not available
Journal Article Narayanan M, Erickson LE, Davis LC. Simple plant-based design strategies for volatile organic pollutants. Environmental Progress 1999;18(4):231-242. R825549C062 (Final)
not available
Journal Article Santharam SK, Erickson LE, Fan LT. Modeling the role of surfactant and biodegradation in the remediation of aquifers with non-aqueous phase contaminants. Journal of Hazardous Materials 1997;53(1-3):115-139. R825549C062 (Final)
not available
Journal Article Zhang Q, Davis LC, Erickson LE. An experimental study of phytoremediation of methyl-tert-butyl-ether (MTBE) in groundwater. Journal of Hazardous Substance Research 2000;2(4):19. R825549C062 (Final)
not available
Journal Article Zhang Q, Davis LC, Erickson LE. Plant uptake of methyl-tert-butyl-ether (MTBE) from groundwater. Practice Periodical of Hazardous, Toxic and Radioactive Waste Management 2001;5(3):136-140. R825549C062 (Final)
not available
Journal Article Zhang QZ, Davis LC, Erickson LE. Transport of methyl tert-butyl ether through alfalfa plants. Environmental Science & Technology 2001;35(4):725-731. R825549C062 (Final)
not available
Journal Article Zhang Q, Davis LC, Erickson LE. Effect of vegetation on transport of groundwater and nonaqueous phase liquid contaminants. Journal of Hazardous Substance Research 1998;1(8):20. R825549C062 (Final)
not available

Supplemental Keywords:

phytovolatilization, diffusion, mass transfer., Scientific Discipline, Toxics, Waste, Water, Ecosystem Protection/Environmental Exposure & Risk, Contaminated Sediments, Environmental Chemistry, Fate & Transport, Bioremediation, Ecology and Ecosystems, 33/50, fate and transport, microbiology, degradation, contaminant transport, microbial degradation, aerobic degradation, biodegradation, contaminated sediment, adsorption, chemical transport, hazardous waste, hazardous organic substances, contaminants in soil, geochemistry, bioremediation of soils, chemical kinetics, photodegradation, 1, 1, 1-Trichloroethane, groundwater contamination, phytoremediation, sorption experiments, bacterial degradation, contaminated soils, TCE

Relevant Websites: Exit

Progress and Final Reports:

Original Abstract
  • 1995
  • 1996
  • 1997
  • 1998
  • 1999

  • Main Center Abstract and Reports:

    R825549    HSRC (1989) - Great Plains/Rocky Mountain HSRC

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R825549C006 Fate of Trichloroethylene (TCE) in Plant/Soil Systems
    R825549C007 Experimental Study of Stabilization/Solidification of Hazardous Wastes
    R825549C008 Modeling Dissolved Oxygen, Nitrate and Pesticide Contamination in the Subsurface Environment
    R825549C009 Vadose Zone Decontamination by Air Venting
    R825549C010 Thermochemical Treatment of Hazardous Wastes
    R825549C011 Development, Characterization and Evaluation of Adsorbent Regeneration Processes for Treament of Hazardous Waste
    R825549C012 Computer Method to Estimate Safe Level Water Quality Concentrations for Organic Chemicals
    R825549C013 Removal of Nitrogenous Pesticides from Rural Well-Water Supplies by Enzymatic Ozonation Process
    R825549C014 The Characterization and Treatment of Hazardous Materials from Metal/Mineral Processing Wastes
    R825549C015 Adsorption of Hazardous Substances onto Soil Constituents
    R825549C016 Reclamation of Metal and Mining Contaminated Superfund Sites using Sewage Sludge/Fly Ash Amendment
    R825549C017 Metal Recovery and Reuse Using an Integrated Vermiculite Ion Exchange - Acid Recovery System
    R825549C018 Removal of Heavy Metals from Hazardous Wastes by Protein Complexation for their Ultimate Recovery and Reuse
    R825549C019 Development of In-situ Biodegradation Technology
    R825549C020 Migration and Biodegradation of Pentachlorophenol in Soil Environment
    R825549C021 Deep-Rooted Poplar Trees as an Innovative Treatment Technology for Pesticide and Toxic Organics Removal from Soil and Groundwater
    R825549C022 In-situ Soil and Aquifer Decontaminaiton using Hydrogen Peroxide and Fenton's Reagent
    R825549C023 Simulation of Three-Dimensional Transport of Hazardous Chemicals in Heterogeneous Soil Cores Using X-ray Computed Tomography
    R825549C024 The Response of Natural Groundwater Bacteria to Groundwater Contamination by Gasoline in a Karst Region
    R825549C025 An Electrochemical Method for Acid Mine Drainage Remediation and Metals Recovery
    R825549C026 Sulfide Size and Morphology Identificaiton for Remediation of Acid Producing Mine Wastes
    R825549C027 Heavy Metals Removal from Dilute Aqueous Solutions using Biopolymers
    R825549C028 Neutron Activation Analysis for Heavy Metal Contaminants in the Environment
    R825549C029 Reducing Heavy Metal Availability to Perennial Grasses and Row-Crops Grown on Contaminated Soils and Mine Spoils
    R825549C030 Alachlor and Atrazine Losses from Runoff and Erosion in the Blue River Basin
    R825549C031 Biodetoxification of Mixed Solid and Hazardous Wastes by Staged Anaerobic Fermentation Conducted at Separate Redox and pH Environments
    R825549C032 Time Dependent Movement of Dioxin and Related Compounds in Soil
    R825549C033 Impact of Soil Microflora on Revegetation Efforts in Southeast Kansas
    R825549C034 Modeling the use of Plants in Remediation of Soil and Groundwater Contaminated by Hazardous Organic Substances
    R825549C035 Development of Electrochemical Processes for Improved Treatment of Lead Wastes
    R825549C036 Innovative Treatment and Bank Stabilization of Metals-Contaminated Soils and Tailings along Whitewood Creek, South Dakota
    R825549C037 Formation and Transformation of Pesticide Degradation Products Under Various Electron Acceptor Conditions
    R825549C038 The Effect of Redox Conditions on Transformations of Carbon Tetrachloride
    R825549C039 Remediation of Soil Contaminated with an Organic Phase
    R825549C040 Intelligent Process Design and Control for the Minimization of Waste Production and Treatment of Hazardous Waste
    R825549C041 Heavy Metals Removal from Contaminated Water Solutions
    R825549C042 Metals Soil Pollution and Vegetative Remediation
    R825549C043 Fate and Transport of Munitions Residues in Contaminated Soil
    R825549C044 The Role of Metallic Iron in the Biotransformation of Chlorinated Xenobiotics
    R825549C045 Use of Vegetation to Enhance Bioremediation of Surface Soils Contaminated with Pesticide Wastes
    R825549C046 Fate and Transport of Heavy Metals and Radionuclides in Soil: The Impacts of Vegetation
    R825549C047 Vegetative Interceptor Zones for Containment of Heavy Metal Pollutants
    R825549C048 Acid-Producing Metalliferous Waste Reclamation by Material Reprocessing and Vegetative Stabilization
    R825549C049 Laboratory and Field Evaluation of Upward Mobilization and Photodegradation of Polychlorinated Dibenzo-P-Dioxins and Furans in Soil
    R825549C050 Evaluation of Biosparging Performance and Process Fundamentals for Site Remediation
    R825549C051 Field Scale Bioremediation: Relationship of Parent Compound Disappearance to Humification, Mineralization, Leaching, Volatilization of Transformaiton Intermediates
    R825549C052 Chelating Extraction of Heavy Metals from Contaminated Soils
    R825549C053 Application of Anaerobic and Multiple-Electron-Acceptor Bioremediation to Chlorinated Aliphatic Subsurface Contamination
    R825549C054 Application of PGNAA Remote Sensing Methods to Real-Time, Non-Intrusive Determination of Contaminant Profiles in Soils
    R825549C055 Design and Development of an Innovative Industrial Scale Process to Economically Treat Waste Zinc Residues
    R825549C056 Remediation of Soils Contaminated with Wood-Treatment Chemicals (PCP and Creosote)
    R825549C057 Effects of Surfactants on the Bioavailability and Biodegradation of Contaminants in Soils
    R825549C058 Contaminant Binding to the Humin Fraction of Soil Organic Matter
    R825549C059 Identifying Ground-Water Threats from Improperly Abandoned Boreholes
    R825549C060 Uptake of BTEX Compounds by Hybrid Poplar Trees in Hazardous Waste Remediation
    R825549C061 Biofilm Barriers for Waste Containment
    R825549C062 Plant Assisted Remediation of Soil and Groundwater Contaminated by Hazardous Organic Substances: Experimental and Modeling Studies
    R825549C063 Extension of Laboratory Validated Treatment and Remediation Technologies to Field Problems in Aquifer Soil and Water Contamination by Organic Waste Chemicals