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

January 11, 2001
1:30 p.m.-2:30 p.m.

On January 11, 2001, the following members of the Remediation Technologies Development Forum's (RTDF's) Phytoremediation Action Team, Chlorinated Solvents Subgroup, met in a conference call:

Bob Tossell, CH2M Hill, Inc.
Frank Beck, U.S. Environmental Protection Agency (EPA)
Keith Rose, EPA
Mike Witt, The Dow Chemical Company

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

WELCOMING A NEW SUBGROUP MEMBER

Bob Tossell opened the call by introducing a new Subgroup member, Mike Witt. This addition to the Subgroup, Tossell said, will be beneficial because Witt, who works for The Dow Chemical Company, will offer the industry sector's perspective, a viewpoint that has been lacking in the Subgroup so far. Tossell said that Witt has much experience in the area of phytoremediation, noting that Witt helped Jim Jordahl put together a document on phytoremediation.

For Witt's benefit, Tossell provided a brief overview of the Subgroup's history. He said that the Subgroup, originally called the TCE in Ground Water Subgroup, formed in 1996 under the RTDF Phytoremediation Action Team. For a couple of years, members of the Subgroup held conference calls to brainstorm about sites they were working on. After a while, however, the group became dormant. In late 1999, the Subgroup was revitalized and its name and mission were changed. Since that time, the Subgroup's main effort has been to develop a protocol. This document, which is targeted to site managers, will explain how to determine whether phytoremediation is appropriate to use at a site. This information is pertinent: once it is available, site managers will not be able to simply disregard phytoremediation by saying it is still too new and unknown. Tossell said that the protocol is not intended to be used as a standalone document; in fact, the text will clearly state that site managers should consult experts in the field rather than relying solely on the protocol.

Witt thanked the Subgroup for their warm reception and offered background information about himself. He said that he graduated from Michigan State University and wrote his dissertation on the biodegradation of carbon tetrachloride. For the last two years, Witt said, he has been working for The Dow Chemical Company in the company's Environmental Chemistry Research laboratory. This group serves as an expertise center that provides guidance on remediation technologies to Dow's remediation leaders. (Dow has about nine remediation leaders located around the world; each has a specified jurisdiction.) One of the Environmental Chemistry Research laboratory's main goals, Witt said, is to make sure remediation leaders are aware of emerging remediation technologies. Witt said that Dow has already started implementing phytoremediation at some sites and is considering using it at several others.

Tossell was excited to hear that Dow is pursuing phytoremediation. Generally speaking, he said, the technology has been embraced strongly by universities and academics but is not being embraced as fully at the industry level. Tossell said that he thinks the technology will gain popularity as time passes. When choosing a remedial technology, he said, many people evaluate technologies upon their merit as standalone treatments. Using such a measure may cause site managers to overlook phytoremediation, a technology that is likely to serve as a secondary, or helper, tool more commonly than as a standalone technology. (Tossell estimated that phytoremediation could serve as a standalone treatment at about 25% of the sites where it is used; at the remainder, he estimated, the technology would be used as part of a treatment train.)

THE SUBGROUP'S PROTOCOL

As noted above, the Subgroup is developing a protocol that explains how to evaluate phytoremediation.

The protocol will include five sections, Tossell said. Sections 1 and 2, he said, have mostly been written. Section 2.1 (a five-page literature review) has not been completed yet, but Milton Gordon and Lee Newman are working on it.

Tossell said that the Subgroup is currently working on Sections 3 and 4. The former will describe different applications for the technology; the latter will contain the "nuts and bolts" of the protocol and explain what must be done to determine whether phytoremediation is appropriate at a given site. Tossell said that Section 4.1, which describes a methodology for screening-level assessment, is nearly completed. Section 4.2, which provides a more detailed evaluation approach, is in progress.

Call participants talked briefly about the timeline for the protocol's completion. Tossell said that the draft is progressing nicely, and the Subgroup is getting close to the polishing phase. He thinks the report could be completed by the end of March 2001.

Tossell said that he has been working on two tables, noting that draft versions were forwarded to Subgroup members before the conference call. The call participants talked about the tables at length.

Table 2: Characteristics of Candidate Plant Species for Hydraulic Control or Water Interception Management

Table 2 provides a list of plant species that can be used for one category of phytoremediation application. Tossell said that tables could be prepared listing plant species that are applicable to use for other types of applications as well.

Tossell asked the call participants to comment on the table. They all agreed that the table was useful, but said that information should be added to indicate what climate the plant species grow in. Tossell agreed to add this information. Rather than add an extra column to the table, he said, he might create a series of one-page tables. Each would be dedicated to a specific climate. Frank Beck said that each state's agricultural extension service provides information about plants that grow in their state. He advised contacting the extension services to collect more information for Table 2.

Beck noted that Table 2 indicates that mulberry plants are only available in limited supply. He questioned the accuracy of this statement. In Nevada, he said, these trees are available in plentiful supply. He said that commercial availability might differ between states: if a state regards a specific plant as a nuisance, it might not supply it as readily as another state. Beck also noted that Table 2 indicates that poplars only have a low salinity tolerance. He questioned the accuracy of this as well, noting that there is a type of poplar grown in Nevada that is extremely tolerant. Tossell asked Beck to send him data on these poplars.

Table 3: Guidelines for Recommended Site, Laboratory, and Field Testing

Table 3 makes it clear that phytoremediation can be used in a variety of applications. As Tossell noted, the technology can be used to achieve ground-water hydraulic control or to minimize water infiltration. In addition, the technology has applications in the area of wetland treatment. Also, as demonstrated by the University of Washington, conventional ground-water extraction can be achieved using subsurface phytoremediation treatments.

Tossell said that Table 3 lists the different applications and describes the technical issues and evaluation requirements associated with each of them. For example, he said, the table describes common questions and technical aspects that must be addressed. The table also describes the type of evaluation and site characterization that must be performed to determine if a particular phytoremediation application is appropriate to use at a site. The table also describes the laboratory, greenhouse, and field-scale pilot studies associated with the different applications.

Tossell asked call participants to comment on the table. They all agreed that the table is useful. They did, however, suggest adding a footnote to make it clear that greenhouse, laboratory, and pilot studies might not be necessary at all sites. Beck noted that some researchers have found that it is more cost-effective to plant a full-scale plantation upfront rather than installing small plantations during a pilot phase and then following up with a larger planting effort. Tossell agreed to add the footnote to the table. He said that he will also make sure that the protocol's text clearly states that these studies might not be necessary in all cases. He will also make it clear that it may be more cost-effective to do all the planting upfront.

Discussion of this table prompted call participants to talk about wetland treatments, one of the phytoremediation applications listed in Table 3. Tossell said that there is a gradation in wetlands: at the surface, conditions are aerobic, but in the sediments, oxygen is lacking. Reductive dechlorination occurs in the anaerobic conditions, Tossell said, noting that this leads to the degradation of chlorinated solvents. Beck said that there might be additional mechanisms at work in the wetlands as well. He said that some research suggests that wetland plants are able to take up organic compounds, break them down, and emit them into the air. Tossell agreed that such results are exciting, but said that they must be repeated before anything conclusive can be said about the remedial mechanisms that are at work in wetlands.

ACTION ITEMS

• Tossell agreed to distribute Sections 4.1 and 4.2 to Subgroup members by February 1, 2001. He asked Subgroup members to review these sections carefully so that they will be prepared to offer comments during the next Subgroup conference call. If time permits, Tossell said, he may try to contact each Subgroup member before the call to obtain their input.
  
  
• Tossell agreed to send the following sections of the protocol to Witt: (1) the original outline, (2) the revised outline, and (3) all of the sections that have already been written.
  
  
• Tossell asked Subgroup members to review Table 2 (Characteristics of Candidate Plant Species for Hydraulic Control or Water Interception Management) and Table 3 (Guidelines for Recommended Site, Laboratory, and Field Testing) and e-mail comments to him.
  
  
• Beck agreed to send Tossell information about poplars that exhibit high salinity tolerance.
  
  
• ERG will make sure that Beck is added to the e-mail notification list.
  
  
• ERG agreed to set up the next conference call for Thursday, February 15, 2001, at 1:30 p.m. Eastern Standard Time.

• Subgroup members agreed to send their contact information to ERG (chartnet@erg.com). After receiving this information, ERG will create an updated contact list and forward it to Subgroup members.