SUMMARY OF THE REMEDIATION TECHNOLOGIES DEVELOPMENT FORUM
PHYTOREMEDIATION OF ORGANICS ACTION TEAM
TCE IN GROUND WATER SUBGROUP
CONFERENCE CALL

July 30, 1997
1:00 p.m. to 2:00 p.m.

On July 30, 1997, members of the Phytoremediation of Organics Action Team, TCE in Ground Water Subgroup, held their first meeting via a conference call. The following members were present:

Greg Harvey, U.S. Air Force (Subgroup Co-chair), harvey@emsmtp.wpafb.af.mil
Cliff Casey, U.S. Navy, cccasey@efdsouth.navfac.navy.mil
Harry Compton, EPA, compton.harry@epamail.epa.gov
Jim Duffy, Occidental Chemical Corporation
Ed Gatliff, Applied Natural Sciences, Inc.
Charles Giammona, Texas A&M University, giammonac@aol.com
Milton Gordon, University of Washington, miltong@u.washington.edu
Garald Horst, University of Nebraska, ghorst@unlinfo.unl.edu
Ray Hinchman (sitting in for Christina Negri), Argonne National Laboratory, hinchman@anl.gov
Lee Newman, University of Washington, newmanla@u.washington.edu
Phil Sayre, EPA/TIO, sayre.phil@epamail.epa.gov
Mike Reynolds, U.S. Army, reynolds@hanover-crrel.army.mil
Sankar Venkatraman, McLaren Hart Environmental Engineering Corporation
Stuart Strand, University of Washington, sstrand@u.washington.edu
Bob Tossell, Beak International, Inc., btossell@beak.com

Also present was Rob Ditzion of Eastern Research Group, Inc. (ERG), rditzion@erg.com.

INTRODUCTION

Subgroup leader Greg Harvey opened the meeting by briefly summarizing the role of the RTDF, as described in a September 1996 EPA handout (EPA542-F-96-010). This role is to foster public-private partnerships in conducting laboratory and field research in order to develop, evaluate, and implement innovative remediation technology. A further role is to help understand and overcome institutional and regulatory barriers to using this technology.

TCE PILOT AND FIELD STUDY PROJECTS

Harvey quickly mentioned a number of sites where TCE pilot and field study projects are occurring:
the J Field site at Aberdeen Proving Ground in Maryland, the Edward Sears site in south New Jersey, the Carswell site, and a site in Utah.

Ed Gatliff then discussed two sites that he is working on, one in Louisiana and one in Michigan. The Michigan site has already produced good results, Gatland said. It has ground water 8 to 14 feet beneath the surface and, within 1 year of planting poplars, TCE levels in the tree area dropped from 1,300 parts per billion (ppb) to about 48 ppb. Although Gatland was not able to disclose his client, he said he would be happy to e-mail data to anyone who is interested.

Bob Tossell mentioned two sites, one in New Hampshire and one in Michigan. Neither site has produced data so far. At the New Hampshire site--a wetlands location--Tossell is evaluating the vegetation as well as the distribution of chemicals, both in the wetlands and upgradient from the site. Since the Michigan site is under aerobic conditions, he could not evaluate it for anaerobic information. Tossell said he hoped to explore the use of phytoremediation as an alternative for this site.

Harvey again brought up the Edward Sears site. Phil Sayre indicated that the site contains a mixture of different chemicals; Lee Newman confirmed that the site does not contain TCE. She stated that the site had been used for paint recycling and that many of the contaminants present had been used for paint thinning.

Harvey went on to discuss his own site in Fort Worth, Texas, which has a shallow, thin, major aerobic aquifer. Ground water is at a 6-foot depth, Harvey said; the bedrock confining layer is 12 to 15 feet deep. The TCE is from another source.

Tossell mentioned a Utah State University study of a site at Hill Air Force Base, which was discussed in Superfund Week Volume 11(29), July 25, 1997. Harvey pointed out that this study was only concerned with existing cottonwood growth and involved no actual planting. Newman clarified that the study involved taking tissue samples to see if existing trees were intercepting the plume and if they were interacting with any other compounds. Harvey briefly mentioned a study at Brooks Air Force Base.

Sankar Venkatraman mentioned that he is involved with a British Petroleum site near Cleveland that involves wetlands contaminated with chlorinated hydrocarbons, including TCE and degradation products. The client is interested in exploring phytoremediation technology.

Newman brought up two sites that she is involved in that have not yet produced any data. The first is in EPA Region 10 and involves a large TCE-only plume near Vancouver, Washington. The other site is on a Navy base.

Milton Gordon brought up a site that he has been working on with OxyChem, near Tacoma, Washington. Newman, who also participated at the site, clarified that the study involved three types of trees, and looked at TCE, carbon tetrachloride, and mixtures of the two.

REGULATORY CONCERNS

Gordon noted that Jim Duffy has done well by involving regulators before remediation and genuinely including them in the cleanup process.

Harry Compton commented that phytoremediation sites tend to have few acute human health and environmental threats, and therefore involve fewer "headaches" for regulators. He did state, however, that at his own J Field site, he has experienced difficulties with the regional Biological Technical Assessment Group, a nonregulatory group made up of groups such as the U.S. Fish and Wildlife Service and the National Oceanographic and Atmospheric Administration. This group is concerned about the possibility of releasing TCE from the water, where it has a fairly low impact, to the air. It is also concerned about bioaccumulation in the food chain.

Cliff Casey noted that at a site near Orlando, Florida, the State and EPA were concerned about the impact of introducing non-native vegetation into existing vegetation, habitats, and the environment. On a related note, Tossell mentioned that he was looking into planting single-sex groups of trees (poplar, eucalyptus, and tamarisk) to limit breeding in a non-TCE site in Palo Alto, California.

In response to Compton's earlier concerns, Harvey stated that TCE does not bioaccumulate in herbivores. Compton agreed, but noted that 2 years ago, before recent University of Washington studies, it was difficult to show this. Gordon noted that he is working with a Masters student who is studying the effects that TCE in terrestrial and aquatic detritus has on isopods. The student hopes to expand the study to small mammal nesting material. Gordon noted that leaves on the ground seem to have mostly metabolized their TCE, although he did not know if this was due to enzymatic activity or simply caused by extensive exposure to the sun. Gatliff noted that he has seen quick volatilization of TCE even after harvesting. Ray Hinchman noted that trichloroacetic acid does accumulate and is not volatile. Newman, who is working with the same Masters student, clarified that the study is looking at ways in which TCE and all metabolites affect insects.

Harvey then asked how well trees pump TCE, and how this varies by tree age. Gordon responded that trees tend to pump at a fairly low level. There does not, however, seem to be any general pattern for pumping. Newman mentioned that, as most TCE is metabolized by trees, one cannot look at transpiration rates to determine pumping levels.

Hinchman stated that he had seen an abstract by Stuart Strand suggesting that 70 percent of pumped TCE is transpired and 30 percent is metabolized. Strand clarified that this data had been very preliminary, and only involved small plants in limited lighting. Further field studies indicated that most pumped TCE is metabolized by trees. Newman stated that even less carbon tetrachloride is transpired than TCE. Harvey mentioned that he is studying the actual enzymes in this process. Gordon noted that while his studies of cells in culture had not identified an enzyme, the reaction is an oxidative p450 and not a dehalogenation.

Compton mentioned that he had seen data that disagreed with Strand's comments and indicated 75 percent transpiration. Gordon and Strand clarified that this data was similar to Strand's preliminary data in that it focused on small plants in an enclosed glass reactor with limited lighting. In the field, the results are the opposite. Gordon plans to field test when the weather gets warmer.

Harvey mentioned that he hopes to explore the potential use of phytoremediation in areas with thicker aquifers, but where the depth to ground water is still small. Compton said he has been working at a site with shallow ground water and a 30-foot thick aquifer. He noted that while phytoremediation was promising, it would not reach 100 percent of the plume and would work best in tandem with pumping, especially in the winter, when trees are not as active. Harvey raised the question of regulators' concerns over the often seasonal nature of phytoremediation. Tossell noted that this was a concern, although he did describe a site in Palo Alto, California, where transpiration occurred year-round.

Harvey summarized the discussion of regulatory issues. The regulatory priorities, he said, are the needs to address the remaining ecological toxicity issues, compile transpiration data over time in various parts of the country, and gain a better understanding of the enzymes involved in these processes.

PRACTICAL TREE CULTIVATION CONCERNS

Harvey noted that some trees are more adaptable to austere environments than had been imagined. He described an Eastern cottonwood tree that he and Charles Giammona had found growing in the cracks of a parking lot in Columbus, Ohio. The tree's roots grew straight down, extending for 6.5 feet, through the capillary fringe and into the water table.

Harvey then queried the group about concerns involving herbivores and what sort of products could be used to protect trees. Gatliff noted that he had trouble with jack rabbits in Nevada, but that available plastic wraps diminished this concern. Harvey mentioned that, at one of his sites, beavers had nearly destroyed 28 trees in one week, although the trees are growing back. Compton noted that in the fall he had problems with deer wrestling against and girdling trees during rutting season. Gordon commented that trees are especially sensitive in their first year to issues of shading and competition with weeds. Harvey stated that remediators should anticipate problems such as these, as well as concerns over weather.

MISCELLANEOUS ISSUES AND HOW TO PROCEED

Harvey noted that more TCE phytoremediation activity is occurring than he had anticipated, a fact which he hopes to share with the Department of Defense and regulators. Compton discussed the need to fill data gaps and Gatliff suggested that his site in Michigan would be "perfect" for further short-term studies on pumping capacity and TCE removal.

Duffy noted that he plans to have results from his analysis of the Texas samples available soon.

Mike Reynolds hoped that group members will produce an overview of their phytoremediation research, including topics, results, and methods. He also hoped to see a summary containing information on what methods did and did not work and why.

Hinchman noted that he is working on faster and easier methods for analyzing breakdown products in plant tissues. He has asked DOE to support continuation of this work. He hoped that measuring nonvolatile substances that remain in the plant tissue will prove to be an easy preliminary method of monitoring site contamination. He noted that this could prove to be far easier than soil sampling, for example. Harvey noted that work on TCE partitioning from the air into leaves had been done in Northern Europe.

WRAP UP

The group agreed to meet again in September and work towards preparing a product. Newman suggested meeting about every 2 months. While many agreed that it would be ideal to meet in person, in tandem with a major conference, there are so many upcoming conferences that it seemed unlikely that enough participants from the group would be at any single event. Future meetings could, however, be used to update participants on what has been discussed at these conferences. To this end, the next meeting will take place after "The Fourth International Petroleum Environmental Conference," scheduled for September 9 to 12, 1997, in San Antonio, Texas. Participants will be notified of the precise date and time by e-mail.