WORKSHOP ON PHYTOREMEDIATION OF ORGANIC CONTAMINANTS
Ramada Plaza Hotel
Fort Worth, Texas
December 18-19, 1996
WEDNESDAY, December 18, 1996
WELCOME AND BACKGROUND
Walter Kovalick, Jr., Director of the U.S. EPA's Technology Innovation Office (TIO), welcomed the participants and thanked them for attending. He explained that the goal of the meeting was to share information on current phytoremediation projects in the field and laboratory and to gauge attendees' interest in further joint activities in the future. Kovalick said that the first scheduled speaker, Jim Matthews, Deputy Assistant Administrator for OSWER, had become ill and would not be able to attend. Kovalick assured the participants that EPA is dedicated to public-private partnering, which he described as a viable option for structuring future joint activities.
Kovalick noted that TIO monitors the use of innovative technologies at Superfund sites, and presented preliminary data summarizing the types of source control technologies selected for Superfund remedial actions through FY95. Established technologies, such as incineration and solidification/stabilization have been selected for 390 (57 percent) remedial actions. Innovative technologies have been selected for 300 (43 percent) remedial actions. Selected innovative technologies include soil vapor extraction, thermal desorption, ex situ bioremediation, in situ bioremediation, in situ flushing, soil washing, solvent extraction, and dechlorination. The most commonly selected innovative technologies were soil vapor extraction (selected 20 percent of the time), thermal desorption (selected seven percent of the time) and ex situ bioremediation (selected six percent of the time).
Kovalick also presented data summarizing the types of technologies selected for groundwater remediation through FY95. Pump-and-treat remedies were selected for 562 (93 percent) remedies. Pump-and-treat combined with an in situ treatment technology (for example, air sparging, bioremediation, and passive treatment walls) were selected for 32 (five percent) remedies. In situ treatment technologies without pump- and-treat were selected for only nine remedies.
Kovalick announced a soon-to-be released publication from TIO entitled Recent Developments for In Situ Treatment of Metal Contaminated Soils. The publication will describe the use of electrokinetics, phytoremediation, soil flushing, and solidification/stabilization for remediating metals in soils. Kovalick invited participants to take copies of the TIO publications at the back of the room and to view demonstrations of TIO's Clean-Up Information (CLU-IN) World Wide Web site (http://clu-in.org), the Vendor Information System for Innovative Treatment Technologies (VISITT), and the Vendor Field Analytical and Characterization Technologies System (VendorFACTS).
Kovalick provided a brief history of the Remediation Technology Development Forum (RTDF). In 1992, Fortune 500 problem-site owners expressed an interest to EPA's Administrator in working with EPA and other federal agencies to identify solutions to complex remediation problems. Under the RTDF, groups with common interests and needs form "Action Teams." The mechanisms of the Action Teams are custom tailored to the members' needs with the objective of identifying mutual needs in order to reach a common goal as quickly as possible. Action Teams have been formed to address organics and metals contamination in soils and groundwater. Operating RTDF Action Teams include the LasagnaTM Consortium (dealing with a new in situ soils remediation process), Bioremediation of Chlorinated Solvents Consortium, Permeable Barriers Action Team, In-Place Inactivation and Natural Ecological Restoration (IINERT) Soil-Metals
Action Team, and Sediments Remediation Action Team. Kovalick emphasized that EPA's role in these Action Teams is simply to empower others to work together.
Kovalick expressed his hope that the conference would result in agreements among participants for working together—as an RTDF Action Team or in another form—in addition to exchanging information on phytoremediation research, development, and demonstrations.
CONFERENCE OBJECTIVES
Phil Sayre (EPA Technology Innovative Office) thanked participants for attending and noted that there was a good turnout for the previous day's site visit to a Carswell Air Force Base phytoremediation project. Sayre said the first day of the meeting would be dedicated to getting participants caught up on others' work and the state-of-the-art in phytoremediation through presentations by participants. The second day, he explained, would be dedicated to working in groups to try to answer questions about how to advance the use of phytoremediation: 1) what are the key questions that need to be answered before phytoremediation can be used broadly; 2) how should these questions be attacked, for example, through research or regulatory changes; 3) who are the parties that can best answer the questions; and 4) what are the best mechanisms for communication between users and developers of phytoremediation technologies (for example, RTDF Action Teams, annual meetings, teleconferences, WWW sites, or validation of field testing). Sayre said that a summary of the conference, including a list of attendees' addresses, phone numbers, and e-mail addresses, will be distributed to participants.
REMEDIATION TECHNOLOGY DEVELOPMENT FORUM
Bill Berti (DuPont) described the history and operation of the Remediation Technology Development Forum. Berti noted that he co-chairs the IINERT Soil-Metals Action Team along with Jim Ryan from EPA's Cincinnati laboratory. The RTDF began in 1992 with a discussion between Monsanto and EPA on how to foster collaboration between government and industry, discuss common problems, and develop innovative solutions to difficult contamination problems. The RTDF was created to advance the development of more permanent, cost-effective technologies for the remediation of hazardous wastes. Berti noted that RTDF members are free to form any type of alliance that brings members together to work on priority issues. Formal consortia can be formed where there is a need to protect proprietary information, workgroups can be formed to coordinate scientific programs and gain public acceptance for new technologies, and information sharing activities can be formed to periodically exchange information when interest is high.
Berti said that there are a number of advantages for businesses involved with the RTDF. The government shares costs, technologies, and expertise, and cooperates on addressing site-specific problems. Industry manages the projects, thereby providing "sweat equity." The RTDF can help shape national policy and develop better technologies through leveraging of national resources. EPA can help other government agencies, such as the Department of Energy, network with businesses.
An important lesson learned for RTDF participants is that there needs to be a sponsor—someone who has the problems to drive the program. There also needs to be substantial resources available. Technical and legal discussions should be conducted on parallel paths. It is a large leap from agreement in principle to final contractual language—no agreement is perfectly complete or protective. Working on public acceptance of new technologies is vital. If the right ingredients are in place, exceptional achievements are possible.
Berti then briefly described the IINERT technologies, which are intended to eliminate the hazards of metals in soils. IINERT technologies chemically and physically inactivate metals in soils by incorporating chemicals (phosphates, mineral fertilizers, limestone, and other materials) that change the molecular species of metals, thereby reducing their solubility and bioavailability. These changes may increase the fertility of soils, making plant cover an attractive option for stabilizing the soil. Before DuPont was willing to move forward with development of this technology, the company wanted to see a comparison of costs for various treatment technologies. Treating a 10-acre site with off-site solidification/stabilization would cost $12 million, treating with soil washing would cost $6 million, an asphalt cap would cost $650,000, a soil cap would cost $600,000, and IINERT would cost $250,000.
In response to a question about the role of the sponsor, Berti said a sponsor is needed to plan ahead and move the process along. Kovalick noted that Cooperative Research and Development Agreements (CRADAs) can be signed to allow federal laboratories to provide facilities and support. With government involvement in joint partnerships, businesses also avoid potential anti-trust issues from their joint meetings.
PHYTOREMEDIATION OF ORGANIC COMPOUNDS: MECHANISMS OF ACTION AND TARGET CONTAMINANTS
Steve Rock (EPA National Risk Management Research Laboratory in Cincinnati, Ohio) said that most of the people working on phytoremediation are present at the conference. Phytoremediation is defined as a set of processes that use plants to clean contamination in soil, groundwater, surface water, sediment, and air. The goals of phytoremediation research are to answer questions about the technology's ability to lower contaminant concentrations and its mechanisms of action. The questions to be addressed differ depending on the specific media and contaminants.
Mechanisms of phytoremediation include enhanced rhizosphere biodegradation, phytoextraction, phytodegradation, and volatilization. Enhanced rhizosphere biodegradation takes place in the soil surrounding plant roots. Natural substances released by plant roots supply nutrients to microorganisms, which enhances their ability to biodegrade hazardous materials. Plant roots also loosen the soil and then die, leaving paths for transport of water and aeration. This process tends to pull water to the surface zone and dry the lower saturated zones.
Phytoextraction is the uptake of contaminants by plant roots and the translocation of contaminants into plant shoots and leaves. Where contaminants are stored in plant shoots and leaves, the plants can be harvested and disposed of. Some plant species have demonstrated the ability to store metals in roots. Although roots generally cannot be harvested in a natural environment, a process called rhizofiltration can be used where plants are raised in greenhouses and transplanted to sites to filter metals from wastewaters. As the roots become saturated with metal contaminants, they then can be harvested and disposed of. Plants also have been used to concentrate radionuclides in the Ukraine and Ashtabula, Ohio.
Phytodegradation is the metabolism of contaminants within plant tissues. Plants produce enzymes, such as dehalogenase and oxygenase, that help catalyze degradation.
Physical effects include volatilization, which occurs as plants take up water containing organic contaminants and release the contaminants into the air through plant leaves. Researchers are not sure how much contamination is being transpired into the air. Data on transpiration is still at a preliminary stage. The Cincinnati laboratory is building chambers to monitor the amount of organic contaminants released into the air. Another physical effect of phytoremediation is the hydraulic control of contaminated plumes that can be exerted by trees. Poplars, cottonwoods, and willows, can use up to 200 gallons of water per day and prevent contaminated plumes from flowing past tree roots.
Phytoremediation can be used as a polishing step after the removal of contaminant hot spots for widespread, shallow to medium-depth contamination. The advantages of phytoremediation are: 1) it is in situ, 2) passive, and solar driven; 3) costs only 10 to 20 percent of mechanical treatments; 4) is faster than natural attenuation; and 5) has high public acceptance. Phytoremediation has been selected as part of the remediation process at at least one Superfund site and several private sites; however, most of the field work using phytoremediation is at the testing and demonstration stage. The EPA Cincinnati laboratory currently is compiling information on phytoremediation and intends to provide guidance in five years on how to use the technology.
In response to a question on whether transpiration of organic contaminants has been documented, Jerry Schnoor (University of Iowa) said that transpiration has been documented in the laboratory, but no one is sure to what degree this happens in the field.
PHYTOREMEDIATION OF ORGANIC COMPOUNDS: VALIDATION APPROACHES FOR FIELD TESTING AND RESEARCH NEEDS
Steve McCutcheon (National Exposure Research Laboratory in Athens, Georgia) presented an overview of the benefits and limitations of phytoremediation and described research and research gaps related to phytodegradation. McCutcheon described seven areas where phytoremediation is being investigated for environmental management: 1) phytoaccumulation of metals and organics; 2) rhizofiltration of metals and organics from streams and wastewaters; 3) phytodegradation of organics; 4) phytovolatilization of selenium, mercury, and volatile organics; 5) control of leaching from landfills; 6) microbial stimulation in the rhizosphere; and 7) removal of organics from the air. Some of the benefits of using plants are that they are aesthetically pleasing, control water balance, have highly evolved enzyme systems, can be self- sustaining in nutrients, can achieve complete breakdown of hazardous materials, and are relatively inexpensive.
McCutcheon noted that there are a number of limitations to phytoremediation:
McCutcheon said that EPA's Athens laboratory has developed monoclonal antibodies for at least one of the following three plant enzymes involved in phytoremediation: nitroreductases, dehalogenases, and nitrilase. These antibodies allow one to identify plants that produce these enzymes. Other research conducted by the laboratory includes investigating the pathways of compound degradation and comparing munitions degradation by vascular plants and microorganisms. Plant enzymes can degrade explosives, solvents, nitriles, pesticides, and phenols. Plant enzymes useful for engineering applications include nitroreductases for munitions remediation, dehalogenases for degradation of chlorinated compounds, nitrilase for herbicide treatments, phosphatases (which have not yet been isolated) for treatment of organophosphates, lactase for the oxidative step in munitions degradation, and peroxidase for the destruction of phenols. The Athens laboratory also has worked with the Army on field demonstrations of phytoremediation of munitions at the Iowa Army Ammunition Plant, Volunteer Army Ammunition Plant, and Milan Army Ammunition Plant.
In summary, McCutcheon said that using natural plant processes for phytoremediation is effective for some compounds. However, rigorous science and engineering are required to demonstrate the effectiveness of phytoremediation at particular sites. Mass balances and pathway analysis are the keys to proving the applicability of phytoremediation. In addition, the toxicity and bioavailability of specific compounds must be defined.
PANEL DISCUSSION ON THE USE OF PHYTOREMEDIATION TO CLEAN UP PETROLEUM HYDROCARBON SPILLS
Phil Sayre, the moderator for the Panel Discussion on the Use of Phytoremediation to Clean Up Petroleum Hydrocarbon Spills, introduced the panelists: Dr. Evelyn Drake, Exxon; Dr. Sheldon Nelson, Chevron; and Dr. Alonzo Lawrence, Gas Research Institute.
Phytoremediation of Petroleum Hydrocarbons
Evelyn Drake (Exxon) described her company's research on the bioremediation of aged hydrocarbons in surface soils. Bioremediation can be difficult because of complex soil matrices and the fact that hydrocarbon contaminants are partitioned into solid, water, and air phases of the soil. Despite this complexity, bioremediation works. Exxon is looking into the factors that effect the rate and extent of remediation, including the specific compounds, soil type, moisture level, microorganisms, oxygen availability, nutrient type and amount, temperature, and soil pH. They have found that inoculating soils with special microorganisms is more effective at degrading TPHs than stimulating naturally occurring microorganisms with nutrients.
Exxon has conducted laboratory studies of PAH biodegradability in aged refinery soil. Researchers have investigated the typical composition of aged refining hydrocarbons, and found that many of the more toxic compounds were soluble enough to be affected by plants, while the total petroleum hydrocarbon concentrations in soils may not be lowered beyond a certain point by phytoremediation. The removal of PAHs is strongly affected by the amount of nutrients added, although nutrient levels can be increased to the point of being toxic to microorganisms. More nutrients must be added in a bioremediation application, such as landfarming, as compared to a phytoremediation application.
Exxon is a member of the Petroleum Environmental Research Forum (PERF), a consortium of 10 companies that contributed $142,000 to conduct laboratory studies of phytoremediation of hydrocarbons. The laboratory study compared biodegradation of soils contaminated with aged crude oil and gas plant sludge using phytoremediation, surface tilling, and a control. This study is being completed, but the specific results cannot be disclosed at this point. In general, the addition of plants to a biodegradation system appears to increase degradation rates. Also, the cost of phytoremediation is about half that of microbial bioremediation.
Phytoremediation is a promising technology because of its low cost, low impact, visual attractiveness, ability to reduce contaminant levels to same levels achieved by bioremediation and tilling, and opportunities for plant breeding and genetic engineering. The limitations of phytoremediation are that contamination must be shallow, the site must be a large enough to apply agronomic techniques, there must be sufficient remedial time, and its effectiveness is affected by contaminant variability, weather variability, animal and insect damage, and the presence of toxic chemicals and salt. Drake emphasized that mechanisms of action need to be studied to differentiate between microbial and plant effects.
In response to a question from Steve McCutcheon, Drake said that the PERF consortium is a group of petroleum companies that have been meeting regularly since 1990. Walt Kovalick noted that the consortium was created under provisions of a 1986 statute, which allows companies to conduct joint research projects and avoid potential anti-trust issues. He then noted that research results, such as those for phytoremediation projects, are not readily made available to the public. However, Amoco has created a PERF Home Page (http://perf.vs.com) that describes its environmental research projects.
Use of Trees for Hydraulic Control of Groundwater Plumes
Sheldon Nelson (Chevron) described a field research project in Ogden, Utah, being conducted to study the ability of poplars to act as a hydraulic barrier to solute transport in groundwater. Soils at the site are of low permeability, and the weather is good for transpiration. Gasoline and diesel components are dissolved in the groundwater, which is eight feet below the surface. Three rows of poplars were planted six feet apart and perpendicular to the groundwater flow. A lot of effort was exerted to make sure the tree roots reached the groundwater. Monitoring wells were installed upgradient, within, and downgradient of the trees.
Even though the trees were very young, having been planted in 1995 and 1996, it appeared that the trees were lowering the water level by 1½ to 2 inches. Using simple geohydrological calculations and treating the trees like low-flow pumping wells, Nelson calculated that the trees were using 13 gallons of water per day per tree. He then calculated the pumping rate required to achieve hydraulic control of the groundwater at the site, and estimated a pumping rate of 25-30 gallons of water per day per tree. The conclusion is that it would theoretically be possible to use trees to contain groundwater at the Ogden site. Ari Ferro (Phytokinetics) said that a summer uptake rate of 40 gallons per day has been calculated for a five-year-old poplar.
Gas Research Institute Projects
Alonzo Lawrence (Gas Research Institute, Chicago) said that he was standing in for Tom Hayes, who manages GRI's waste program. Lawrence said that there are 260,000 gas wells in the contiguous United States; 40,000 of which have produced water pits from glycol dehydrations. There also are 700 gas processing plants in the country. GRI is interested in remediation techniques for BTEX, alkanes, amines, glycols, and other chemicals used to treat natural gas. They are investigating bioventing, land farming, and, more recently, phytoremediation. GRI will soon be starting an Environmentally Acceptable Endpoints Project to study the mobility of petroleum hydrocarbons in soils. Another project that soon will be starting is a Manufactured Gas Plant Remediation Project to investigate remedial technologies for phenols, PAHs, and cyanides that could be present at the country's 1,500-2,000 coal gasification plants. Lawrence noted that GRI also contributed money and helped manage the PERF consortium's research project.
PANEL DISCUSSION ON THE USE OF PHYTOREMEDIATION TO CLEAN UP PESTICIDES, WOOD PRESERVATIVES, CHLORINATED SOLVENTS, MUNITION WASTE, AND MIXED WASTE
Bob Olexsey (EPA National Risk Management Research Laboratory in Cincinnati, Ohio), the moderator for the Panel Discussion on the Use of Phytoremediation to Clean Up Pesticides, Wood Preservatives, Chlorinated Solvents, Munition Waste, and Mixed Waste, introduced the panelists: Dick Woodward, Sierra Environmental Services, Inc.; John Fletcher, University of Oklahoma; Joan Brackin, Monsanto; Tom Wong, Union Carbide Corporation; James Duffy, Occidental Chemical Corporation; Tom White, Ciba-Geigy; Greg Harvey, Air Force; and Terry McIntyre, Environment Canada.
Passive Gradient Control
Dick Woodward (Sierra Environmental Services, Inc.) said that he was standing in for Dick Sloan (Arco Chemical Co.). He discussed the use of plants to maintain passive gradient control for post-closure at the French Limited Superfund site in Florida. Objectives of the project were to use non-riparian phreatophytes to maintain an inward groundwater gradient toward the center of a former disposal lagoon area. Woodward explained that non-riparian phreatophytes are water loving plants that frequently have deep roots to absorb water from the capillary fringe zone of the phreatic surface (water table). This would avoid the migration of contaminants into surrounding aquifers and enhance natural flushing and intrinsic bioremediation.
Conditions that impact phreatophytes at the French Limited site include high temperature and humidity (which lower transpiration rates), brackish water, a water table 20-25 feet below the surface, and DNAPLs. Underground utilities, wells, and compact back fill divert tree roots and result in differential growth. There is a significant volume of low-level contaminated groundwater with low migration rates and low remediation rates. Run-off and run-on are controlled. Bioremediation is the selected remedy for the lagoon.
For the study, a number of phreatophytes were evaluated to identify species that would use 200-800 gallons of water per day and are suited to the conditions at the French Limited site. Alders, ash, aspen, river birch, and poplar all grow fast but have a low salt tolerance. Cottonwoods and willows have shallow roots. Mesquite and salt cedar tolerate salt but are difficult to control. Bald cypress prefers hot humid climates but its roots form knees. Eucalyptus grows very fast but has a low cold tolerance and is disease prone. Greasewood prefers cold or dry climates. Woodward emphasized that conducting a plant species evaluation early in a phytoremediation project is critical.
Phase 1 of the project included planting and watering bald cypress and river birch. Results were poor primarily because of salt impacts. Therefore, a second phase was implemented the following year using a wider variety of plants. A specific planting cycle was instituted and a drip irrigation system was installed to help establish the plants and encourage deeper root growth. Phase 2 efforts resulted in establishment of an inward gradient. Good control of the groundwater gradient was established during the growing season, but control was poor when the trees dropped their leaves.
The advantages of using phytoremediation were that hydraulic control was established, channeling could be avoided, clay soils were loosened, costs are low, and it is synergistic with the site closure plan. Woodward noted that a plant breeding program is needed to develop specific species. Desired characteristics include frost hardiness, fast growth, deep feeder roots, upright growth habit, salt tolerance, chemical tolerance, disease and insect resistance, and an ability to grow on poor alkaline soils. In addition, the plants should be native to a particular area, evergreen for winter control, and available from local vendors.
Walt Kovalick asked what would be done to maintain control after the growing season ends. Woodward said they are looking for broad leaf evergreens, such as water oak. Sheldon Nelson asked how the salt tolerance problem was addressed. Woodward replied that they initially used a deeper water source to get the plants established.
Summary of Screening Studies
John Fletcher (University of Oklahoma) summarized plant screening studies conducted by the University. The work was started with the perspective that there are bacteria that degrade PCBs using biphenyl as a cometabolite. They looked for naturally occurring substances produced by plants that could replace biphenyl as the cometabolite. Some flavonoid, coumarin, and other compounds were discovered that could serve as a substrate. They then looked for plant species that synthesize these compounds in large enough amounts to help degrade PCB. Seventeen perennial plant species grown throughout the country were evaluated. The three most promising species were crabapple, osage orange, and mulberry. The compounds are released at the end of the growing season, which is consistent with the time of death of some roots. Root death is an important factor because it provides channels in the soil and releases flavonoids, coumarins, and other compounds.
Fletcher noted that most of these species can benefit from the sugars and amino acids released by most plants. A single gram of soil contains 10,000 different bacterial species. The challenge is to develop plant species that release compounds that promote the PCB degraders over the other 10,000 bacterial species.
Fletcher said that computer imaging technology was developed to simulate root growth and death. In nature, 1-5 percent of the soil is roots; 30 percent of these are fine roots. One percent of the total soil volume is in contact with dying fine roots. If the rhizosphere is included, seven percent of the total soil volume is affected. In order to affect the total soil volume using phytoremediation, you would need a 15-20 year project. To study this process, a contaminated site with established vegetation could be examined. The rate of phytoremediation could be increased by using an electromagnetic field to move water containing contaminants back and forth through the same rhizosphere, and therefore expand the zone of influence of the rhizosphere.
Overview of Lasagna Technology
Joan Brackin (Monsanto) said that Monsanto is forming a new life science company that will look at phytoremediation. Monsanto has potential field sites and will investigate the feasibility of coupling phytoremediation with their LasagnaTM technology. The LasagnaTM process combines electroosmosis with treatment zones that are installed directly in contaminated soils to form an integrated in situ remedial process. Contaminants within pore waters are moved into the treatment zones with an electromagnetic field. The process can be used to move groundwater into plant root zones. By reversing polarity, groundwater can be moved back and forth through the root zone. In response to a question from Evelyn Drake, Brackin said that the range of water movement is about one centimeter per day. In response to another question, Brackin said that the process works best in saturated conditions, but water can be moved into the vadose zone to some extent.
The Living Cap
Tom Wong (Union Carbide Corporation) described a waste impoundment site that illustrates the concept of a "living cap," or use of plants to remediate a site and provide a closure pathway for the site. The one- acre facility includes four former impoundments, one of which (Basin 6) was drained of water 20 years ago exposing highly toxic sludge with the consistency of axle grease that contained PAHs and other mixed waste. Basin 6 now supports a diverse plant community, including grasses, shrubs, and a 65-75 percent tree cover, including mulberry and hackberry. Wong noted that mulberry is not a common plant in the area and that the closest mulberry tree is a half mile away from the site. In fact, he believes that plant to be the seed source for the mulberry trees growing on the site. The oldest of the mulberry trees germinated 18 years ago, only two years after the impoundment was drained. Wong noted that mulberries release flavonoids and coumarins that support PAH degrading bacteria.
A portion of Basin 6 was excavated to a depth of 40 inches. The upper two to three feet of sludge in Basin 6 looks like top soil and has no chemical odor. The vegetation has dewatered the upper zone and strengthened and stabilized the sludge to the point that it could support a drill rig. Roots penetrated to a depth of two to three feet. There is a strong demarcation between the upper layers and the deeper sludge, which was saturated with water. Analysis of samples down to three feet found high concentrations of PAHs (with concentrations increasing with depth), according to the EPA Appendix 9 procedures. However, TCLP analysis showed nondetectable levels of PAHs in the same soils. Gas chromatography showed a very low number of PAH peaks at shallow soil depths.
Advantages of the living cap concept are: sludge can be converted to soil; evapotranspiration minimizes water infiltration through sludge; vegetation minimizes exposure to contaminants; the plants are aesthetically pleasing and self sustaining; and the toxicity and mobility of contaminants are reduced. A living cap does as well or better than a clay cap in preventing infiltration of rainwater. In addition, run-off from a living cap does not have to be treated as you would have to with a clay cap. The cost of a living cap is often less than a conventional cap.
In response to a question from Evelyn Drake, Tom Wong said that nothing was planted at the site and no nutrients were added. In response to other questions, Wong said that they have not analyzed samples from the deeper sludge and the plants have not been analyzed to determine contaminant concentrations. Evelyn Drake said that Exxon has a similar site in New Jersey, where golden rod and phragmites are growing into a contaminated area from the edges. The plants have lowered contaminant concentrations at the edges by a factor of five to ten. Jerry Schnoor said that vegetation caps have been approved by RCRA in lieu of a RCRA cap because studies have shown that seepage through the vegetation is less than through a conventional cap. He noted one capped 13-acre site as an example.
Field Experiment Using Poplar Trees to Treat Trichloroethylene
James Duffy (Occidental Chemical Corporation) described a field experiment to investigate remediation of TCE contaminated groundwater by poplars. Phytoremediation is being considered primarily for non-active sites where the time for remediation is not critical. Early laboratory experimentation showed that poplars will take up TCE and can tolerate reasonable levels of the contaminant. Occidental received permission by the State of Washington to conduct field experiments using introduced TCE.
A two-year controlled field experiment to evaluate the uptake, metabolism, and transfer of TCE from groundwater by hybrid poplars was completed in November, 1996. Four meter by six meter cells were constructed to a depth of 1½ meters and lined with a double wall polyethylene liner. Sand and gravel were placed in the bottom of the cells, which were then filled with soils native to the site. Water was injected into the cells at a rate to maintain a residence time of one week. Once established, the plants were exposed to 15 ppm concentrations of TCE and extracted water was analyzed. Data from the second year shows that 65-70 percent of the introduced TCE was recovered from control cells that did not contain trees but very little TCE was recovered from the cells with trees. Bag and FTIR measurements of air samples found negligible transpiration of TCE in the second year of growth. Continuing activities include analyzing the trees, determining the fate of the TCE, and verifying laboratory experiments. Analysis of data from the field experiment will be completed in three to five months.
Steve McCutcheon noted that a laboratory mass balance study showed high transpiration of TCE by poplars. Duffy said that the field experiment could have been designed better to determine mass balances. In response to a question about evidence of chloroform and vinyl chloride production, Duffy said that small amounts of vinyl chloride were detected.
Phytoremediation of Contaminated Sites
Tom White (Ciba-Geigy) said that Ciba-Geigy may have an interest in applying phytoremediation to cleanup their sites; they are currently evaluating several candidate technologies for their utility. White then described three contaminated sites that could be candidates for phytoremediation. The first site, Tom's River, is contaminated with chlorinated and non-chlorinated solvents in the vadose and saturated zones. Specific contaminants include TCE, toluene, anthracene, and naphthalene. A pump-and-treat system is in place, with packed carbon treatment and discharge to surface waters. It is a CERCLA site with northern and southern groundwater plumes. Depth to groundwater is 10 feet. The subsurface is sandy with clay stringers that may contain perched groundwater and DNAPLs. Researchers are looking at 1-15 years of active in situ bioremediation, followed by semi-passive remediation, then intrinsic remediation.
The MacIntosh, Alabama, site is located in a flood plain that is contaminated with pesticides, including DDT. It is a 10-15 acre CERCLA site with surface contamination over a large area. Portions of the site are forested with bald cypress, but there are other portions that are flooded in the winter with no vegetation. Contaminant concentrations do not exceed 1,000 ppm, and the DDT is bioavailable.
Another site in Elkton, Maryland, is a RCRA site contaminated with pesticides. Pesticide formulation at the site resulted in contamination of the top 18 inches of soils with DDT, toxaphene, and lindane at levels of approximately 50 ppm. When the facility was in operation, the site was primarily clear fields. It is now covered with trees and shrubs and seems to be an ideal site for phytoremediation.
Problems with using phytoremediation at these sites include bioavailability of residuals that are not leachable, the ultimate fate of residues, limitations on VOC releases, cleanup levels, and where the point of compliance takes place. If the point of compliance is the source area rather than discharge to surface water, phytoremediation probably will not be feasible. White said that there are numerous opportunities for research, including bioavailability, semi-analytical models, and phytoremediation process development.
Demonstration of Remediation of Shallow TCE using Cottonwood Trees
Greg Harvey (U.S. Air Force) said that the Air Force is conducting a field study to demonstrate whether planted eastern cottonwood trees can help remediate shallow TCE-contaminated groundwater. Air Force Bases typically have an enormous extent of TCE contaminated groundwater plumes, and cottonwoods are found throughout the world. The best niche for phytoremediation is between bioventing and intrinsic bioremediation. The Air Force has established a Technical Advisory Committee to help direct phytoremediation demonstrations.
A phytoremediation demonstration is being conducted at the Naval Air Station in Fort Worth, Texas, where there are good conditions for plant growth. The Base is underlain by a shallow, thin aerobic aquifer, with a depth to groundwater of 6-10 feet. Impermeable bedrock is beneath the aquifer. Rows of cottonwood trees have been planted perpendicular to groundwater flow to intercept a TCE plume. Up- gradient controls and 20 monitoring wells up- and down-gradient have been installed. They are looking to see how fast the tree roots reach the water table. Phytoremediation could be cost effective if the roots grow fast. During a drought year, liberal irrigation was used to keep the trees alive. So far, the trees have grown very fast. The Air Force plans to analyze TCE, vinyl chloride, and haloacetic acids to see how concentrations change over time.
John Fletcher asked whether existing trees would be monitored, and Harvey said that they will be looking at enzymes and other factors in existing trees. In response to a question about the rate of natural attenuation at the site, Harvey said they have found some biodegradation by bacteria.
Canadian Experience with Phytoremediation
Terry McIntyre (Environment Canada) said that he is excited about the potential for phytoremediation as an innovative environmental solution for recalcitrant compounds, heavy metals, and radionuclides. The estimated cost for toxic metal reduction in Canada is $6 billion, and in the United States is $35 billion just for heavy metals. Environment Canada conducted a series of focus group meetings to gauge the awareness and support for phytoremediation by the public. Preliminary data show a public support rate of 82 percent. There probably is a similar level of support for phytoremediation in the United States—people understand plants. McIntyre cautioned that the public must be kept informed as work on phytoremediation moves forward.
The advantages of using trees for remediation are that they can create effective barriers, require low levels of maintenance, are inexpensive, and can be used at many sites simultaneously. Limitations of phytoremediation include a slower growth period, nutrient and water requirements, and a need for more research. Tree species being considered by Environment Canada include alder, hybrid poplar, black locus, sweetgum, loblolly pine, and juniper.
Environment Canada has developed a preliminary research strategy, and will convene a group of scientists from Environment Canada, other government agencies, and the private sector in February. Five major areas of research have been identified, including mechanisms of uptake, transport, and accumulation; genetic evaluation of hyperaccumulators; rhizosphere interactions; field validation and evaluation; and clarification of regulatory oversight. Other research needs are determining how selective plants are and what to do with mixed wastes. There is a lot of enthusiasm in Canada's government agencies and a lot of valuable information already is available.
PANEL DISCUSSION ON SUCCESSES AND BARRIERS TO COMMERCIALIZING PHYTOREMEDIATION
Steve Rock, the moderator for the Panel Discussion on Successes and Barriers to Commercializing Phytoremediation, introduced the panelists: Dr. Jerald Schnoor, University of Iowa; Dr. Kathy Banks, Kansas State University; Dr. Ari Ferro, Phytokinetics; and Dr. Paul Thomas, Thomas Consultants.
Research at the University of Iowa/Limitations to Phytoremediation
Jerry Schnoor (University of Iowa) began his presentation by posing questions that regulators ask most often before allowing phytoremediation to be used at a site:
Schnoor then noted that due to underbudgeting at voluntary cleanup sites, efficacy and mass balance have not been demonstrated very well in the field. He added that it is difficult in some cases to predict which contaminants will be taken up by plants. The rule of thumb is that those with a log Kow of one to three can be taken up. However, some chemicals with a log Kow of 0.2 are absorbed by plants.
Next, Schnoor discussed phytoremediation lab studies that have been conducted at the University of Iowa. The first study was a reproduction of a Brigg's (1982) plot where phytoremediation was used to address approximately 20 contaminants. Some of the contaminants—atrazine, alachlor, TCE, BTEX, chlorobenzene, benzo(a)pyrene, BEHP, chlordane, nitrobenzene, aniline, TNT, RDX, and 1,4- dioxane—were examined for uptake, volatilization, and soil mineralization. Analysis has shown that innocuous end-products have been found using 14C-compounds for atrazine and TCE in vegetables and poplars. Tests in the Midwest on atrazine showed that 138 ppm soil concentrations were decreased to 20 ppm atrazine after two growing seasons, with atrazine ring cleavage products detected within 80 days (results soon to be published in Environmental Science and Technology). In Iowa, an ammunition plant had soils contaminated with TNT. During phytoremediation of this site, some of the RDX was translocated into leaf tissue, while TNT was not translocated, but degraded in the root zone.
University of Iowa researchers have teamed up with consultants who have expertise in design, irrigation techniques, and tree planting to further their work in the area of phytoremediation. Both pilot- and full- scale demonstrations have been performed for pesticides, nutrients, TNT, and RDX (in process), BTEX, and TCE contaminated soils.
Schnoor next discussed the limitations of phytoremediation technology. He explained that phytoremediation is most applicable at shallow contaminated sites with moderately hydrophobic contaminants. He then noted that it is difficult to establish vigorously growing vegetation at many sites due to soil contamination, especially from metals. In addition, damage to vegetation from deer browsing, voles, beavers, damaging frosts, and disease, should be considered before choosing phytoremediation as part of a cleanup decision. Schnoor then noted that in order for phytoremediation to be successful as a commercial technology, fate studies need to be performed in the lab and greenhouse to understand entry into the environment of parent compounds and metabolites.
Schnoor then presented the group with a list of the research needs that should be identified before phytoremediation can be considered a successful technology:
Phytoremediation Work in Cooperation with EPA's Region 7/8 Hazardous Waste Substance Center (HSRC) and Two Industry Partners
Kathy Banks (Kansas State University) discussed phytoremediation work she has been conducting in cooperation with EPA's Region 7/8 Hazardous Substance Research Center (HSRC) and two industry partners. The first site she described was a Gulf Coast site that is contaminated with crude oil that has leaked into an agricultural area. Here, plots have been seeded and overseeded with rye and St. Augustine grasses, and sorghum. After 21 months, researchers were able to determine enhanced microbial activity on the vegetated plots, which appeared to result in TPH degradation. In addition, they found that the rye and St. Augustine grasses performed better than the sorghum and the unvegetated control plot. Banks noted that this may have occurred because rye and St. Augustine roots are more fibrous than sorghum roots and provide more surface area for microbial activity.
Banks next described her work at an old refinery site contaminated with petroleum hydrocarbons on the West Coast. Here, plots include an unvegetated control, a tall fescue plot, a native California fescue plot, and a grass and legume mixture plot. Preliminary results indicate that the mixed species plot at this site appears to be more effective at remediating the contamination than the single species plots.
A new research project began last summer at a naval facility in Norfolk, VA, where bioremediation cells are being used to implement phytoremediation. The species used at this site include Bermuda grass with annual rye, tall fescue, and white clover. Researchers are hopeful that phytoremediation will work at this site because of the significant growth they have already seen in the plants and observed TPH degradation. However, only time will tell the extent of the technology's effectiveness at this site.
Banks then presented the group with some conclusions she has been able to make from her research:
Phytokinetics, Inc./SITE Program Project
Ari Ferro (Phytokinetics, Inc.) discussed a phytoremediation project to remediate soils containing 75-400 ppm PCP and PAHs at an old wood preserving site in Portland, OR. This project was the first phytoremediation technology accepted into EPA's SITE Program.
The project was conducted in two phases—a greenhouse study (Phase I) and a small field-scale study (Phase II)—to compare the rates of contaminant removal in both planted and unplanted samples. For Phase I, soil samples, which were very acidic and only had the basic level of nutrients, were collected from the McCormick & Baxter Superfund site where significant PCP and PAH contamination exists. These samples were then put into four columns: two planted with perennial rye grass and two unplanted. Data shows that the nutrient status remained the same in the four treatments, but contaminant removal rates increased in the planted samples. Phase II was conducted at a small plot on the McCormick & Baxter Superfund site. Here, four plots—two unplanted and two planted with perennial rye grass—were developed in a 50 x 50 foot area where there was light PCP and PAH contamination. Ferro said data from both phases indicate that a full-scale phytoremediation field study may be successful to remediate the contamination at the site.
Phytoremediation and Commercialization
Paul Thomas (Thomas Consultants) discussed phytoremediation as it pertains to commercialization. He explained that detailed information is needed to determine the kinds of soil that should be used for field- scale phytoremediation projects. Water movement, reductive oxygen concentrations, root growth, and root structures all affect future growth of plants and should be considered when implementing phytoremediation.
Thomas then noted that the success of phytoremediation by trees is often determined by root growth and that it is difficult to determine the direction roots will grow in the field. One way to do this, however, is to influence root growth patterns by digging a trench around the existing roots, using a pressure washer to uncover the roots, and covering them up again. Thomas then said that it is important to know the source of any contamination before deciding to use phytoremediation. He added that a full site characterization is needed if vadose zone soils are contaminated.
Thomas said that most owners of contaminated sites don't want to fund research on their sites, but seem to be willing to fund phytoremediation. In addition, there seems to be no incentive for researchers who implement phytoremediation projects to return to these sites to collect data to determine if the technology is working. Thomas said that all phytoremediation projects should include a "pre-plan" to ensure that data will be collected at sites in the future.
Thomas then showed slides of a LUST site where phytoremediation is being used to remediate petroleum contamination. Two rows of hybrid poplars were planted on the site in trenches and a monitoring well was built three feet down gradient from the trees. Next spring, researchers plan to use Hydropunch™ sampling to see if the technology is working.
THURSDAY, December 19, 1996
PANEL DISCUSSION ON REGULATORS' PERSPECTIVES ON PHYTOREMEDIATION
Jim Cummings, the Panel Moderator, led the Panel Discussion. He explained that this session was being held to address the relationship between regulation and remediation. The three most important programs that have a remediation component are CERCLA, RCRA, and TSCA. CERCLA via the National Contingency Plan has a remediation (versus regulatory) thrust. The statute itself provides relief from permit requirements (section 121(e)). RCRA and TSCA have regulatory requirements which impose duties and potential sanctions on researchers, technology developers and remediation practitioners. Familiarity with appropriate provisions of RCRA (for RCRA hazardous wastes) and TSCA (for PCB wastes) is recommended before commencing treatment activities
Cummings noted that to date there have been few, if any situations where potential application of RCRA requirements to a phytoremediation project has arisen. Most projects to date appear to involve voluntary cleanup programs not involving wastes subject to RCRA. There are some unresolved policy issues regarding the extent to which phytoremediation may be subject to RCRA. The Technology Innovation Office has initiated discussion with the Office of General Counsel and the Office of Solid Waste.
Cummings noted that discussions with federal and state regulators indicated a general receptivity to phytoremediation, i.e., there did not appear to be any inherent bias against phytoremediation approaches.
Nevertheless, regulators tended to voice a recurring set of concerns. These concerns tended to be practical in nature (rather than narrow issues of regulatory requirements which regulators are sometimes accused of being hung up on), for example:
Cummings then introduced the panelists for this session: Lisa Marie Price, U.S. EPA–Region 6; Richard Clarke, Texas Natural Resource Conservation Commission (TNRCC); Harry Compton, U.S. EPA–ERTC, Edison, NJ; and Thomas Wilson, U.S. EPA–Region 10 who provided some perspectives based on their site-specific experiences and their general experience as regulators.
U.S. EPA–Region 6 Phytoremediation Projects
Lisa Marie Price (U.S. EPA-Region 6) presented the group with her experience at three sites where phytoremediation either has been considered or implemented. The first site is an old munitions site where phytoremediation was considered to remove TNT product. Price noted that researchers continue to monitor the phytoremediation/natural degradation that appears to be occurring with the standing pines on the site.
The next site is an old pesticide plant in East Texas where portions of the site have been closed by a state order. Residual contamination has been found in the neighborhoods adjoining the site. Price explained that phytoremediation was considered as a remedy for the arsenic at the site, but EPA didn't choose the technology because the site was being addressed as a time critical removal action in order to prevent recontamination of the neighborhood.
The third site, the Red River Army Depot, is a military vehicle refurbishing installation where phytoremediation is being considered as an option for treatment. Phytoremediation is being proposed by the Army to address chlorinated solvent contamination in ground water; however, because the installation is being realigned under the Base Realignment and Closure (BRAC) program, creating clean-up time constraints, and because there is an inadequate understanding of the extent of the problem, EPA is hesitant to fully endorse phytoremediation as an integral part of the site's remedy.
Phytoremediation and TNRCC
Richard Clarke (TNRCC) said that TNRCC has little experience with phytoremediation and is concerned about this technology's application at sites where time constraints and risk reduction rules are an issue. He noted that phytoremediation may be a partial option for treatment, but under state rules, TNRCC has to approve all rules and is unsure how to permit phytoremediation projects.
Phytoremediation at Aberdeen Proving Ground
Harry Compton (U.S. EPA–ERTC, New Jersey) discussed a phytoremediation project being implemented on a historic bombing range at Aberdeen Proving Ground (APG) in Maryland. The site has old toxic burning pits where munitions were burned, causing groundwater contamination with PCA, tetrachlorine, TCE, and chlorinated solvents eight feet under ground.
Compton noted that APG prefers the use of state policy to provide alternatives to cleanup and restore the aquifer. Compton added that researchers have considered a variety of technologies for cleanup, but most were ruled out because of the presence of UXO on the site. There are no clean-up time constraints for the site. Compton said the Army was willing to spend money to do phytoremediation, but wanted to refer to as a "revegetation study" until EPA and the Army can prove that the technology can work.
The site was planted with hybrid poplars and a trench was built to ensure that the trees would be taking up groundwater instead of rain water. Researchers were concerned about predator and frost problems, but the trees flourished and have already grown to 1-3 inches in diameter. Compton said that the Army has used three pairs of lysimeters, which were is nested at two different depths, to investigate vadose pore water and has monitored the leaves, stems, and roots of the plants on the site. In addition, the Army and EPA plan to perform bag studies to measure VOCs in the air. Investigations show that PCA has been taken up by the plant roots but may not be translocated in the plant.
The Army is hopeful that the technology will work, but no direct evidence data currently has been collected from the site to determine if phytoremediation is being effective. According to Compton, there are plans to examine whether VOCs are present in both woody and animal tissue. A short video has been developed for this project. For a copy, contact Compton at (908) 321-6751.
Phytoremediation and Regulation
Thomas Wilson (U.S. EPA-Region 10) explained that the regulatory community can make technology commercialization difficult. For example, while some regulators are willing to support field trials needed to advance a new technology, others prefer to wait until the technology is proven by someone else. And even after all studies are done, spreading the word among the many federal, state, and local regulators can present a daunting challenge.
Wilson then noted that some people may view phytoremediation as a ploy to give problem-site owners more time for cleaning their sites. Some (hopefully few) even argue that high cleanup costs are punishment for polluters, and that phytoremediation should thus not be used to lower those "punishment" costs.
Wilson then noted the absence of environmental groups at the meeting. He stressed their importance in achieving both public and regulatory acceptance of this new technology. Wilson then urged meeting attendees to actively seek opportunities to educate environmental and citizens' groups on phytoremediation.
OPEN DISCUSSION
Stuart Strand said regulators should be committed to ensuring that adequate data comes out of phytoremediation projects. John Fletcher noted that the only way to get phytoremediation commercialized is to obtain data from naturally occurring ecosystems where plants appear to have success in naturally remediating contamination that occurred in the past. He added that the success for phytoremediation is dependent on increased funding and that the government should be committed to providing funds to move the technology forward.
Steve McCutcheon noted that rigorous investigation is needed to determine the successful application of phytoremediation. He then expressed his concern that phytoremediation may end up being used at sites prematurely before scientists truly understand the state-of-the-science of this technology. Walt Kovalick said there should be a greater effort to gather data on phytoremediation, but didn't think this applied work would likely get done with research grants. Instead, it will probably need to be funded through partnerships and alliances.
Tom Wilson said EPA has not acknowledged phytoremediation as a technology that has applications beyond just cleanup. Terry McIntyre said considerations need to be made for source material and disposal of spent biomass when addressing phytoremediation.
Jerry Schnoor said regulators should be involved early in the technology selection process. He then noted that fate data should be collected for both laboratory and greenhouse studies. He added that geochronology of intrinsic bioremediation sites should be investigated.
Thomas Wilson said research in the area of phytoremediation is very fragmented and isolated data points won't give us the data we need to move forward. What we need are funding sources that can be accessed to integrate the data that has already been collected. John Fletcher said despite limited funding, available data from laboratory experiments can be used to determine what will happen in the field. He then noted that a holistic approach needs to be developed for risk analysis for toxics in ecosystems. Tom Wong agreed, but said that research should move forward at sites where phytoremediation makes sense.
Joseph Keflemarian (TNRCC) said that phytoremediation regulations, which include time constraints and require containment technology, should be in place before phytoremediation is used. This poses a dilemma, however, that would require support from the regulatory community and development of quick guidance on this issue by the states. Richard Clarke agreed, noting that once risk is contained, long-term solutions can be developed to determine if phytoremediation is working.
John Fletcher said enough is currently known to estimate evapotranspiration by plants and determine rainfall in certain areas. In addition, it is known that water run-off from sites needs to be collected for treatment by other methods. With this knowledge, there is no harm in initiating phytoremediation projects now. Stuart Strand responded that knowledge of seasonal variations and buffers for plume migration should be built into phytoremediation systems. He added that agronomic knowledge is very important to determine whether phytoremediation projects will be successful.
BREAKOUT GROUP REPORT-OUTS
After some discussion, the attendees decided to breakout into two groups: one to discuss chlorinated solvents and the other to discuss petroleum and pesticides. Each breakout group was charged to answer the following questions:
1) What are the important questions, which, if answered, will allow broad application of phytoremediation?
2) How shall these questions be addressed (e.g. laboratory, field, research and development, demonstrations)?
3) Who are the interested parties?
4) How shall we proceed (e.g., meeting summary, teleconferences, electronic means, form a group like and RTDF)?
Petroleum/Pesticides Breakout Group
Phil Sayre, TIO, presented the attendees with his breakout group's findings. The following list includes the issues (noted by underlining) that the group identified to answer the first Question above: What are the important questions, which, if answered, will allow broad application of phytoremediation? Text under each of the underlined items addresses the second Question noted above: How shall these questions be addressed (e.g. laboratory, field, research and development, demonstrations?
1) Develop Fate and Transport Models for certain contaminants within plants.
The group acknowledged that existing ground water models can be used to a limited extent in phytoremediation applications, but that more integration of plant effects on groundwater need to be added to these models such as transpiration rates and their effects on groundwater. Also, models need to be developed that integrate plant effects on contaminants and water availability in the unsaturated zone. As part of this integration of plants into existing groundwater and vadose zone models, further work needs to be done to model the fate of contaminants within the plant tissues: distributions of metabolites in different plant tissues (stem, root, leaf) are difficult to predict, as well as transpiration rates for water and contaminants such as volatile organics.
2) Establish toxicity-driven regulatory endpoints that would apply to phytoremediation.
The group discussed ways for determining whether phytoremediation residuals are toxic. They agreed that phytoremediation tests should include toxicity assays for the end-products of phytoremediation including tissue metabolites and remaining chemicals present in soils/sediments following phytoremediation. The findings of the toxicity tests should be incorporated into the fate and models so that the total time for remediation of a site could be made based on toxicity of relevant compounds, fate and transport models could focus on those plant metabolites which pose the greatest risk, etc. Efforts should be made by those interested in pursuing toxicity testing, as it relates to phytoremediation, to become active in the Petroleum Environmental Research Foundation/Gas Research Institute (PERF/GRI) efforts in the area of toxicity testing. Members of the group also thought that since a significant portion of the PERF/GRI effort is focussed on earthworm tests as an indicator of the toxicity of soils/sediments during the remediation process, fertilizer toxicity to earthworms should be examined.
3) Determine the bioavailability/mobility of phytoremediation residuals in soil
Linked with the issue of the toxicity of residual chemicals in soils following phytoremediation is the ability of these chemicals to become bioavailable to target organisms or move offsite. Some residuals, regardless of their toxicity, may be so tightly bound to soil that they cannot cause toxicity to organisms or move from the remediation site to other locations due to their inability to partition to the liquid phase. Further tests were recommended on remediation with grasses in which PAH and TPH concentrations are compared over time. After such long-term studies are done, is there binding of petroleum wastes to soils/sediments which decreases the mobility and/or toxicity of the wastes? Are there other plant species which should also be considered for such testing?
4) Identify federal funding vehicles for forensic studies of wastes.
The group discussed which agencies should be responsible for funding projects which would examine the decreased toxicity at sites which have become overgrown with plants as part of the natural ecological progression that occurs (so-called forensic studies of contaminated sites). As an example of such a site, see the presentation given by Mr. Tom Wong at this meeting. There is a need to identify which Federal Agency would fund such work and whether efforts should be focussed on lab or field studies. The group agreed that data would need to be obtained from existing industrial sites and that regulators would need to ease restraints on site owners to gather more data. The group also discussed the extent to which small pipeline spills need to be cleaned up and which plant species occur at these sites which could be planted in similar locations.
5) Develop screening models that can identify whether phytoremediation will work at a site, and which treatability tests need to be conducted.
Such a minimum data set would aid decisionmakers involved in assessing the utility of
phytoremediation at a site.
6) Determine the minimum data set that would be needed to show that phytoremediation has been efficacious at a site.
Such a minimum data set would also aid decisionmakers involved in assessing the utility of
phytoremediation at a site.
7) Development of a database that would indicate which plant species/cultivars are capable of assisting in the remediation of agricultural chemicals and petroleum hydrocarbons.
The group believed such a database could be begun by gathering existing data first from
the literature, and from some private companies which have begun this effort already.
Sayre next presented a list of the interested parties who should be involved in phytoremediation which was responsive to the third Question posed to the break out Group: Who are the interested parties?
· USDA
· NOAA
Finally, Sayre then described different avenues the group identified for continuing the discussion on phytoremediation, in response to the final Question posed: How shall we proceed (e.g., meeting summary, teleconferences, electronic means, form a group like and RTDF?
1) An electronic meeting place (i.e., WWW site or electronic bulletin board system) should be developed for at least two purposes: to provide a database of the results of phytoremediation tests which have been conducted, and to serve as a question-and-answer forum.
2) There should be a participant follow-up conversation on partnering in three-months.
3) The list of interested parties noted above should be prioritized in order to focus in on
those most likely to be of assistance.
4) A second meeting should be held to further discuss phytoremediation. This meeting could be held in conjunction with Batelle's "Fourth International Symposium on In Situ and On-Site Bioremediation," which is being held in April in New Orleans and will likely attract the most participants from the Ft. Worth meeting. Alternatively, a meeting could be arranged in conjunction with the IBC Phytoremediation Meeting, which is being held in Seattle this June.
5) A minimum data set should be developed by Industry and the U.S. and Canadian Federal Governments that would be provided by those who clean up a waste site that would provide convincing evidence that the site has been remediated.
6) The issues of phytoremediation should be tied into an existing RTDF since funding is already available for such an effort. (Walt Kovalick noted that an RTDF can be developed without funding commitments. He added that the initial success of an RTDF is not so much determined by funding as it is by the travel and time commitments each member is able to give.)
Chlorinated Solvents Breakout Group
Steve McCutcheon presented the Chlorinated Solvents Breakout Group's findings. The following list includes the issues the group identified to answer What are the important questions, which, if answered, will allow broad application of phytoremediation?
McCutcheon then noted that the group agreed that a solid research and development strategy is needed. This strategy could include the following:
McCutcheon then presented some consensus points developed by the group:
- Air Force, Army, Navy, and other components in the Department of Defense
· Funding could be provided by:
- EPA
· Technology developers who should be involved include:
- ASTM
· Other groups who should be involved in the phytoremediation discussion include:
- Regulators; the Interstate Technology and Regulatory Cooperation Workgroup (ITRC)
McCutcheon then noted that the group agreed that chlorinated solvents behave differently than petroleum hydrocarbons and should be covered by a separate partnering group. John Fletcher said he couldn't agree more, noting that a distinction between soluble versus insoluble compounds should be made when discussing implementation of phytoremediation because insoluble compounds involve different processes, including bacterial degradation.
CLOSING REMARKS
Walt Kovalick informed everyone that EPA will e-mail out the attendees list to all attendees early next week. He added that EPA will explore the idea of establishing a web site for phytoremediation that could include a "chat room" for sharing ideas on phytoremediation. EPA also will explore the idea of establishing an RTDF for phytoremediation. He then noted that TIO is willing to act as a clearinghouse of information on phytoremediation.
Kovalick said that EPA will consider planning a meeting on Phytoremediation, possibly in conjunction with the New Orleans or Seattle Phytoremediation meetings. Tom Wong noted that TNRCC plans to hold its large conference at the same time of the New Orleans meeting, which would exclude participation by any TNRCC employees if New Orleans was chosen as the meeting place. Kovalick then said that EPA would be willing to set up a series of teleconferences to discuss phytoremediation until a decision is made when to hold the meeting.
The meeting adjourned.