SUMMARY OF THE REMEDIATION TECHNOLOGIES DEVELOPMENT FORUM
PHYTOREMEDIATION ACTION TEAM
CHLORINATED SOLVENTS SUBGROUP
CONFERENCE CALL

April 5, 2000
1:30 p.m.–3:00 p.m.

On April 5, 2000, the following members of the Remediation Technologies Development Forum’s (RTDF’s) Phytoremediation Action Team, Chlorinated Solvents Subgroup, met in a conference call:

Milton Gordon, University of Washington (Subgroup Co-chair)
Lee Newman, University of Washington (Subgroup Co-chair)
Keith Rose, U.S. Environmental Protection Agency (Subgroup Co-chair)
Bob Tossell, GeoSyntec Consultants (Subgroup Co-chair)

Also present was Christine Hartnett of Eastern Research Group, Inc. (ERG).

FACE-TO-FACE MEETING

Members of the RTDF Phytoremediation Action Team will meet on May 3, 2000, at the Omni-Parker hotel in Boston, Massachusetts. A preliminary meeting agenda has been prepared. It lists the following scheduled activities:

• Total Petroleum Hydrocarbon (TPH) in Soil Subgroup meeting. This group is currently scheduled to meet between 8:30 a.m. and 12:00 p.m.

• Alternative Cover Assessment Program (ACAP) Subgroup meeting. This group is currently scheduled to meet between 1:00 p.m. and 5:00 p.m.

Call participants asked whether a time slot could be reserved for the Chlorinated Solvents Subgroup. They expressed great interest in presenting the Subgroup’s goals and activities, and said that addressing these topics would only require 30 minutes. ERG agreed to look into changing the agenda. (ERG will recommend starting the meeting 30 minutes earlier so that the Chlorinated Solvents Subgroup meeting will not cut into time that has already been allotted to other Subgroups.) Bob Tossell agreed to prepare and deliver the Subgroup’s presentation. Subgroup members agreed to assist Tossell in this endeavor: (1) Lee Newman will send him slides; (2) Newman, Tossell, and Milton Gordon will meet via conference call to decide which topics to address; and (3) Subgroup members will comment on the presentation after receiving a draft from Tossell.

RTDF WEB SITE

Conference call participants said that the Subgroup’s Web site should be updated. They recommended:

• Changing the Subgroup’s name. The Web site lists the Subgroup as the "TCE in Ground Water Subgroup." Tossell said that this should be changed to "Chlorinated Solvents Subgroup."

• Posting conference call summaries. Seven Subgroup conference call summaries have been prepared over the last half year. Tossell recommended posting them on the Web site. ERG agreed to send Subgroup members summaries of the following calls: November 10, 1999; November 24, 1999; December 8, 1999; January 12, 2000; February 16, 2000; March 2, 2000; and March 15, 2000. Subgroup members agreed to review these and let ERG know which ones to post. (If no feedback is received by April 19, 2000, ERG will post all of the summaries.)

• Providing a contact name. Some RTDF Action Teams provide contact information for their Steering Committee members. Tossell asked whether the Chlorinated Solvents Subgroup should do the same. Call participants suggested posting one contact name, but they did not decide whose it should be.

THE SUBGROUP’S PROTOCOL

The Chlorinated Solvents Subgroup plans to establish a field study program. Over the last several weeks, they have been developing an outline for the program’s protocol. Tossell said that he distributed a revised draft outline, entitled A Guide for the Evaluation of Phytoremediation of Chlorinated Solvents in Soil and Ground Water, to all Subgroup members before the conference call. He said that this revised version incorporates the comments that Keith Rose provided in March 2000, but that it does not incorporate the comments that he recently received from Linda Fiedler, Newman, and Gordon.

Tossell provided a brief overview of the topics covered under the outline. Then call participants discussed the following topics:

• Using a mass-balance approach. Call participants agreed that the protocol should stress the benefit of using mass-balance approaches to assess phytoremediation’s potential at different sites. Tossell said that this approach could be used in pilot- or full-scale tests. If researchers can track contaminants and demonstrate mass conservation, he said, it will be easier to convince regulators and site owners that phytoremediation is a good technology.

• Determining whether there are toxicity issues. Newman said that the Subgroup’s protocol should stress the importance of evaluating potential toxicity issues. Investigators should understand their sites’ contaminant profiles thoroughly; that way, she said, they will know beforehand whether a site’s conditions are too toxic to support plant growth.

• Metabolites should be identified and their longevity should be assessed. Newman and Gordon said that the Subgroup’s protocol should stress the importance of identifying metabolites and evaluating their longevity. Tossell agreed, noting that contaminant breakdown products can accumulate and persist in plants for years, and that, in some cases, metabolites are even more toxic than parent compounds. Call participants noted two ways in which accumulated toxic metabolites can impact the environment: (1) the contaminant could be dispersed if a tree were cut down and turned into mulch, and (2) the contaminant could be ingested by insects that eat tree parts. Call participants agreed that this brings up complicated risk assessment issues, and they talked about ways to determine whether metabolites are accumulating. They agreed that plant tissue analysis could provide useful information, but Tossell warned that these analyses do not necessarily indicate how much metabolite accumulates as a byproduct of contaminant breakdown processes. For example, he said, chloroacetic acids form as a byproduct of trichloroethylene degradation, but also through several natural processes. Unless carbon-14 tracking technologies are used, Tossell said, it might not be possible to determine a metabolite’s origin. Newman said that Tossell had a good point; however, to determine whether metabolites had formed largely through contaminant degradation, researchers could compare metabolite concentrations in trees in uncontaminated areas with concentrations in trees that are established at contaminated sites.

• Potential applications for phytoremediation. Section 3 of the Subgroup’s protocol will address the potential applications of phytoremediation. In this section, Tossell said, the Subgroup will explain how phytoremediation can be used to (1) intercept plumes and achieve hydraulic control in shallow subsurfaces, (2) treat solvents in the vadose zone, and (3) manage water by preventing precipitation from migrating to underlying aquifers. This section will also describe innovative and potential new applications. For example, it will discuss deep ground-water control, an application that involves putting trees into wells. Tossell asked call participants to suggest other applications that would fit in the "innovative" category. Newman suggested including some of the approaches that the University of Washington is testing: (1) phytoremediation combined with underground drip irrigation, and (2) phytoremediation combined with barrier walls. She agreed to provide text on these approaches. Gordon suggested discussing approaches that involve hybrid trees.

• Determining whether greenhouse tests are required. Section 4 of the Subgroup’s protocol will explain how to determine whether phytoremediation is a viable treatment for a given site. The section is split into three subsections: 4.1 (Tier I—preliminary assessment), 4.2 (Tier II—full-scale assessment), and 4.3 (Tier III—research assessment). Rose noted that the outline recommends addressing the following topic under subsection 4.1: Are greenhouse tests required? He recommended moving this topic to subsection 4.2 and addressing it with topics that relate to laboratory testing. Tossell thought this was a good idea. If this change is made, Tossell and Rose agreed, subsection 4.1 will discuss only activities that involve conducting a simple paper-based evaluation of available materials.

• Steps taken when collecting additional data and refining site conceptual models. Rose noted that there are 10 steps listed under subsection 4.2 (Tier II—full-scale assessment). He said that the activities recommended under steps 1 and 2 are repetitive; he questioned whether this was intentional. Tossell agreed to look over these steps carefully.

Tossell, who is eager to move forward on the Subgroup’s protocol, recommended assigning the following people to write text for sections 1 and 2:

Call participants agreed to work on these topics and to forward text to Tossell before the next Subgroup conference call. They also agreed to notify him if they have additional comments on the protocol’s outline.

MISCELLANEOUS

Newman said that phytoremediation systems reduce contaminant concentrations through a variety of mechanisms: chemicals can be degraded by plant enzymes, broken down by microorganisms, or released into the air through volatilization. All three processes, Newman said, contribute to the success of phytoremediation, but they do not play equal roles at all sites or for all sets of chemicals. For example, she said, at one site, plants may be responsible for most degradation. At another site, however, microorganisms or volatilization may play the most important role.

ACTION ITEMS

• ERG agreed to talk to meeting planners about modifying the agenda for the RTDF Phytoremediation Action Team meeting that is scheduled to take place in Boston, Massachusetts, on May 3, 2000. (The Chlorinated Solvents Subgroup would like to give a 30-minute presentation at the meeting. ERG will suggest starting the meeting 30 minutes earlier so that the Subgroup can be accommodated without cutting into the presentations that have already been scheduled.)

• Tossell agreed to prepare a presentation for the RTDF meeting. This effort will require the following:

• ERG agreed to inform Environmental Management Support, Inc. that the Subgroup wants to have its Web page updated. Also, ERG will send Subgroup members the summaries that were prepared for the following calls: November 10, 1999; November 24, 1999; December 8, 1999; January 12, 2000; February 16, 2000; March 2, 2000; and March 15, 2000. Subgroup members will review these and let ERG know which should be posted. If no feedback is received by April 19, 2000, ERG will post all of the summaries.

• Newman will send Rose the comments that she and Gordon submitted for the Subgroup’s outline.

• Newman said that the Subgroup’s protocol should include information on using phytoremediation in combination with (1) underground drip irrigation and (2) barrier walls. She agreed to provide text on these approaches. Gordon suggested discussing approaches that involve hybrid trees.

• Rose noted that the Subgroup’s outline recommends addressing the following topic under subsection 4.1: are greenhouse tests required? He recommended moving this topic to subsection 4.2, and addressing it with topics that relate to laboratory testing.

• Rose noted that there are 10 steps listed under the Subgroup outline’s subsection 4.2. He said that the activities recommended under Steps 1 and 2 are repetitive; he asked whether this was intentional. Tossell agreed to look over these steps carefully.

• Call participants will notify Tossell if they have additional comments on the protocol’s outline.

• Call participants agreed to start writing text for the protocol. They agreed to work on sections 1 and 2, and to forward text to Tossell before the next conference call. Tossell recommended assigning the following people to the topics listed under sections 1 and 2:

• ERG will set up a conference call for April 19, 2000, between 1:30 and 3:00 Eastern Daylight Time.

• ERG will e-mail a Subgroup contact sheet to all Subgroup members.