SUMMARY OF THE REMEDIATION TECHNOLOGIES DEVELOPMENT FORUM
PHYTOREMEDIATION ACTION TEAM
TOTAL PETROLEUM HYDROCARBON IN SOIL SUBGROUP MEETING
Sheraton Hotel and Marina
San Diego, California
April 21, 1999
INTRODUCTORY COMMENTS
Lucinda Jackson, Chevron Corporation
Phil Sayre, U.S. Environmental Protection Agency (EPA)
Lucinda Jackson and Phil Sayre, the co-chairs of the Total Petroleum Hydrocarbon (TPH) in Soil Subgroup, opened the meeting by welcoming participants (see Attachment A for a participant list). Jackson explained that the TPH in Soil Subgroup is one of three Subgroups that have been established under the Remediation Technologies Development Forum (RTDF)'s Phytoremediation Action Team. (The other two Subgroups are the Trichloroethylene in Ground Water Subgroup and the Alternative Covers Subgroup.)
The TPH in Soil Subgroup's mission is to evaluate how effectively plants degrade aged petroleum
hydrocarbons across a range of geographical locations and climatic conditions. Over the past year, Jackson
said, Subgroup members have developed a field study program and protocol to ensure that comparable
study designs and analytical procedures are used across demonstration sites. (Jackson gave a brief
overview of the protocol, explaining that it requires researchers to set up three treatments: an unplanted
control; a standardized grass mixture that contains rye, legume, and fescue; and a local species of the
researcher's choosing. Jackson said that the protocol requires researchers to collect soil samples before
treatment plots are planted [T0] and after each growing season [T1, T2, and T3].) Sayre said that Subgroup
members communicate regularly via conference calls. This face-to-face meeting was held, he explained, so
that Subgroup participants could report on the status of their projects, learn more about available analytical
procedures, and get feedback on the Subgroup's protocol.
UPDATE ON FIELD TEST SITE PROGRESS
Jackson said that 10 sites have been identified as potential candidates for inclusion in the Subgroup's field program. Progress across the sites varies. While some site owners (or principal investigators) have gained regulatory approval, established research agreements with EPA, collected soil samples, and seeded their treatment plots, others are still working on these activities. Meeting participants provided the following site updates:
Site A
Jackson said that Chevron has initiated a phytoremediation project at Site A, a heavily weathered site with TPH concentrations of about 2 to 5 percent. Jackson said that Chevron has received state and local regulatory approval for their field test and that Chevon and EPA recently signed a Cooperative Research and Development Agreement (CRADA). She said that treatment plots were seeded in late 1998 and that strong plant growth has resulted. T0 samples have been collected, but results are not yet available. In April, Jackson said, Peter Kulakow will visit the site to collect plant biomass samples and to flag samples for the June 1999 T1 sampling event.
Site B
Jackson said that the state EPA has granted approval for a demonstration project at Site B. Chevron and EPA will conduct the field study together. (An agreement between the two was formalized recently in a CRADA.) Site characterization samples were collected in early April, Jackson said. The treatment plots have been planted and T0 samples have been collected.
Sites C, D, and E
Mike Reynolds said that his research team has initiated field studies at three sites. The climates and contamination history vary substantially between each:
Reynolds said that environmental agencies, Native American representatives, and consultants are involved with the demonstration projects. Funding is being provided primarily by the Department of Defense's Environmental Security Technology Certification Program (ESTCP). Reynolds said that the protocol used at the three sites has been designed to meet the research needs of the TPH in Soil Subgroup and ESTCP. As a result, it includes some extra field components and analyses that are not mandatory under the Subgroup's protocol. For example, Reynolds said, four treatments (unplanted/fertilized, unplanted/unfertilized, vegetated/fertilized, and vegetated/unfertilized) will be established rather than three, soil samples will be analyzed for microbes, and samples will be collected in three forms: composites (specified by the Subgroup protocol), grabs (specified by the state regulatory agency), and soil-socks samples.
Reynolds said that T0 samples have been collected at all three sites. The results indicate that (1) TPH and biomarkers (i.e., hopane) are present at all three sites, (2) contaminant concentrations are most variable at Site E, (3) microbial numbers are similar at Sites C and E, and (3) microbial numbers are substantially higher at Site D. Greg Douglas was surprised that hopane was detected at Site C because this biomarker is not usually present in jet fuel; he said that another waste may have spilled at the site and left this biomarker behind.
Reynolds said that seeds were planted in fall 1998 at Sites D and E. The treatment plots were established in areas with the least weathered soils. Reynolds said that delineating the plots was challenging because his research team had to work around several existing structures.
Site F
Steve Geiger said that a phytoremediation demonstration project is being initiated at Site F. Site characterization samples will be collected in late April, he said, and treatment plots will be established in late May or early June. Geiger said that this project will provide information on phytoremediation's impact on subsurface soils because his client plans to use willow trees (whose roots extend deeper than grass roots) in one treatment. Geiger said that the state has granted regulatory approval for the demonstration project. He said that the clients have reviewed and signed a CRADA and have forwarded it to EPA for finalization.
Site G
Kulakow said that Kansas State University (KSU) has received permission from a state agency to conduct a demonstration project at Site G. Kulakow said that KSU is at the early stages of project planning; no sampling activities have been conducted and a formalized agreement between KSU and EPA has not yet been established.
Sites H and I
David Tsao said that he hopes to finalize a CRADA with EPA before May 1, 1999. He said that he would like to conduct a demonstration project at Site H. The state agency associated with this site seems amenable to the idea, Tsao said, but has not yet granted regulatory approval. Tsao said that Site I might also serve as a good candidate for field study. The owners of this site have expressed strong interest in conducting a demonstration project and have talked to their state agency about using phytoremediation. Tsao said that project funding for Site I will not be available until next year, however.
Site J
Meeting participants said that Duane Wolf plans to conduct a demonstration project at Site J. One
participant said that Wolf has formalized an agreement with the site owner, but has not yet initiated
sampling or planting activities.
THE TPHCWG METHODOLOGY
Steve Geiger, ThermoRetec, Inc.
Geiger said that several states have instituted TPH cleanup standards, the values of which range by several orders of magnitude. He reminded participants that TPH is simply a measure of bulk hydrocarbon and provides no information about the specific compounds that are present. (Geiger said that crude oils can contain as many as 100,000 individual compounds.) Geiger said that hydrocarbons exhibit a wide range of toxicological effects: some are highly toxic, some are more benign, some pose carcinogenic risks, and others pose noncarcinogenic hazards. Because the chemical composition of TPH varies across sites, the risk posed by exposures can also vary dramatically across different sites. The TPHCWG has developed a methodology to calculate site-specific risk-based screening levels (RBSLs) for TPH. Concentrations that fall below these site-specific values, Geiger said, are not likely to pose a risk to human health. Geiger said that the values generated are site-specific because they take a TPH's specific chemical composition into account and incorporate site-specific exposure information. (Geiger said that RBSLs can be calculated for a number of different exposure pathways [e.g., inhalation, ingestion, and dermal contact] and receptors [e.g., residents, trespassers, and workers].)
Geiger said that the TPHCWG methodology assesses TPH toxicity by using a combination of two approaches:
Geiger said that using a combination of the above-listed approaches helps generate a more realistic site-specific RBSL. He noted that TPH mixtures can consist of thousands of compounds, but toxicity data is usually only available for about 40 or 50 of them. Relying solely on the indicator approach, therefore, would not give researchers a well-rounded picture of the toxicity of an entire TPH mixture.
Geiger said that RBSLs can be used within the American Society for Testing and Materials' Risk-Based Corrective Action (RBCA) framework, a guide that offers a tiered approach for making environmental cleanup decisions. Under RBCA, Geiger said, Tier 1 RBSLs are compared to site contaminant levels. (Geiger explained that Tier 1 RBSLs incorporate generic default values for exposure.) If site contaminants exceed the RBSL, Geiger said, site owners may initiate cleanup or conduct a more detailed Tier 2 Assessment. If the latter is chosen, Geiger said, RBSLs are recalculated as site-specific target levels (SSTLs) using site-specific exposure and transport values (e.g., ingestion rates and fractions of organic carbon). If the site contaminants still exceed the RBSL, site owners may initiate cleanup or perform a Tier III Assessment that uses more complicated statistical analyses (e.g., Monte Carlo) and/or fate and transport analyses.
Geiger said that the TPHCWG methodology is still in development, but is being used in several states. (Michigan has formally accepted the methodology as a valid technique for evaluating crude oils at exploration and production sites.) Geiger advised participants to read the methodology's Volume 5: Human Health Risk-Based Evaluation of Petroleum Release Sites: Implementing the Working Group Approach for additional information and case studies. He said that Subgroup members are not required to use the TPHCWG methodology, but he did ask all Subgroup members to ask for the Direct Analysis Approach when they send their samples to laboratories. (Arthur D. Little [ADL] and Battelle have agreed to charge no more for this procedure than they do for more conventional analytical methods.) Participants who do plan to use the TPHCWG risk-based approach, Geiger said, will also need to ask for benzene, toluene, ethylbenzene, and xylene (BTEX) data during T0 and T3 sampling events.
Geiger concluded his presentation by listing the benefits of using a site-specific TPH cleanup goal rather than a fixed standard. First, he said, investigators can be confident that human health is protected if contaminant concentrations are lowered to risk-based standards. Second, he said, using a site-specific RBSL can change the way remedial success is measured at a given site. (In cases where regulators agree to use a risk-based RBSL, he said, a remedial technology can be regarded as a success even if it does not reduce contaminants to state-wide cleanup levels.) Third, he said, site-specific RBSLs can strongly influence which remedial technologies are chosen at a given site. (In cases where regulators agree to use a risk-based RBSL, site owners [or principal investigators] may be able to convince the regulators that an inexpensive "polishing technology" will adequately protect human health even if this technology does not have the capability to lower contaminants to the state's cleanup level.)
Geiger's presentation spurred a discussion about how to measure the success of a phytoremediation project.
Several suggestions were offered. Geiger said that success could be determined based on whether the
technology achieved certain endpoints (i.e., RBSLs or state and federal standards). Another participant said
that success could be measured based on the percent of hydrocarbon reduction achieved during a short time
period. John Fletcher disagreed with this approach, noting that the benefits of phytoremediation may be
grossly underestimated if only short-term reductions are considered. He said that the technology must be
promoted as a sustainable technology that exerts benefits over the long-term.. He said that researchers may
find that contaminant concentrations decline steadily for decades. One participant questioned Fletcher's
claim and stated that degradation processes are likely to level off over time. Fletcher acknowledged that this
could happen, but said that plants will continue to restore their soil ecosystem over a number of years.
Fletcher warned participants against using contaminant reduction trends as the only measure of success. He
advised looking at the health of the overall community when trying to determine whether phytoremediation has been a success.
ANALYZING TPH AND HYDROCARBONS
Greg Douglas, Arthur D. Little (ADL)
Kevin McCarthy, Battelle
Douglas opened his presentation by reiterating the Subgroup's goal: to evaluate how effective plants are at degrading aged petroleum hydrocarbons. Douglas noted that all successful environmental research projects require a clear definition of a problem, a strong study design, a comprehensive analytical strategy, and a meaningful interpretation of the data. He said that laboratories can be used to help choose study designs (by using pan studies to determine the conditions needed to enhance a project) and to track changing conditions over time.
Douglas reminded participants that petroleum products consist of a complex mixture of hydrocarbon classes, including alkanes, parafins, isoparafins, aromatics, aliphatics, and olefin. He said that compounds degrade at different rates depending on their chemical structure. While some degrade very quickly, he said, others are highly refractory to degradation. The latter are referred to as biomarkers. Douglas said that dramatic contaminant reductions are unlikely to be seen at sites that have already been biodegrading for decades, but that ADL is equipped to detect subtle changes. (Douglas said that ADL's techniques have been approved and used by many organizations and agencies.) Douglas said that petroleum samples can be analyzed with:
Douglas said that contaminant reductions can be calculated by evaluating ratios. He said that biomarkers can be used to normalize data, and that this approach is particularly useful at sites that have a high degree of variability. He said that the total oil depletion over time equals (1 H0/H1) x 100; where H0 represents the biomarker analyte concentration in the source oil and H1 represents the biomarker analyte concentration in the degraded oil. (Douglas noted that all analyte data must be reported on an oil weight basis.) Douglas also noted that the amount of reduction for a given contaminant can be calculated as [1 - (C1/C0) x (H0/H1)] x 100; where C0 represents the target analyte concentration in the source oil and C1 represents the target analyte concentration in the degraded oil. Douglas said that several papers have been written on the importance of using biomarkers to normalize data and told participants to contact him if they want references. At one site, Douglas said, investigators failed to see reductions in benzo(a)pyrene when they evaluated their raw data, but a downward trend was discovered when the data were referenced to a biomarker. Douglas said that hopane is used as a biomarker at many sites. Other biomarker options are available, however, if hopane is not present. (He said that hopane is not usually detected at jet fuel or diesel fuel sites.)
Kevin McCarthy praised Douglas for his thorough presentation and said that he had little to add. He did
take the opportunity, however, to stress the importance of the site characterization and T0sampling events.
He said that biomarkers must be selected and measured at this time so that the H0 value is established. He
said that the preliminary analyses also play an important role in determining how to lay out treatment plots.
MICROBIAL ANALYSES
Andrew White, Microbial Insights, Inc.
David White, University of Tennessee's Center for Environmental Biotechnology
Andrew White and David White provided an overview of the analytical services that are offered by Microbial Insights, Inc., a company that uses molecular-based approaches to characterize microbial communities. White said that analyses are applied directly to environmental samples and do not involve any culturing. (He said that only 1 percent of microbial species are amenable to culturing techniques.) White described three of the analyses offered by the company:
White said that the above-listed techniques could be used to provide useful information to Subgroup members. He referred back to Geiger's presentation, and revisited the topic of how to measure the success of phytoremediation. White posited that phytoremediation can be regarded as successful if it causes microbial communities to return to the state they were in prior to being subjected to environmental stress. (White said that stressed communities are usually less diverse than healthy communities.) White said that a return to the nonstressed state would indicate that the microbes consider the environment to be "healthy" and that contaminants are no longer bioavailable. Several Subgroup members expressed interest in pursuing this idea further. Jackson asked how research teams would know what a healthy microbial community should look like. White recommended examining nearby uncontaminated areas that support similar vegetation. (Additional details on this topic can be found in an article published in the Journal of Microbiological Methods.)
Subgroup members were very interested in the type of data that Microbial Insights, Inc., offers. Reynolds
said that microbial analyses are not mandatory under the Subgroup's protocol, but he strongly encouraged
participants to include them in their test design. He said that it would be very valuable to see how microbial
data change as contaminant concentrations decrease. Meeting participants agreed, but said that cost may
prohibit widespread use of microbial analysis technologies. White said that Microbial Insights, Inc., is
eager to collaborate with the Subgroup and he agreed to send a cost and work proposal to ERG. Once ERG
receives the proposal, it will be distributed to the entire Subgroup. Subgroup participants asked White to
include information on the number of samples and replicates that should be evaluated to produce
meaningful results. They asked him to provide costs for the an ideal experimental design (many replicates
analyzed) and a bare-bones design.
PROTOCOL REVIEW
The most recent version of the Subgroup's protocol (dated April 1999) was distributed to meeting participants. Albert Venosa said that he reviewed the protocol carefully and identified several areas that require additional information or clarification:
Sayre and Jackson thanked Venosa for his comments. Kulakow agreed to modify the existing version of the protocol to address some of Venosa's questions.
MISCELLANEOUS TOPICS
Kulakow said that KSU is acting as a central coordinator for the Subgroup field program. He encouraged participants to contact him if they need KSU's support. Kulakow also asked participants to send him relevant site information by the end of November so that he can compile an annual report.
Meeting participants agreed that the Subgroup should try to develop cost estimates for phytoremediation technologies. They agreed to sort through cost-tracking spreadsheets and to distribute them to each other via fax. Once Subgroup members have some numbers in front of them, Sayre said, cost issues can be discussed in greater detail via conference calls.
Sayre said that the next Subgroup meeting will likely be held later in the year, after researchers have had an
opportunity to collect field data. He recommended meeting in Cincinnati, Ohio, in August or September 1999.
Attachment A
Attendee List
Total Petroleum
Hydrocarbons in Soils
Subgroup Meeting
Sheraton Hotel and Marina
San Diego, California
April 21, 1999
Attendee List
| Dawn Carroll Environmental Engineer Technology Innovation Office U.S. Environmental Protection Agency 401 M Street, SW (5102G) Washington, DC 20460 703-603-1234 Fax: 703-603-9135 E-mail: carroll.dawn@epamail.epa.gov Greg Douglas John Fletcher Steve Geiger Lucinda Jackson Peter Kulakow Kenneth Lee Kevin McCarthy Bud Prevatt Mike Reynolds |
Phil Sayre Stuart Strand David Tsao Albert Venosa Andrew White David White RTDF technical and Christine Hartnett Conference Manager/Technical Writer Eastern Research Group, Inc. Building A - Suite 101 8303 North MOPAC Expressway Austin, TX 78759 512-231-2260 Fax: 512-231-2261 E-mail: chartnett7@aol.com Carolyn Perroni Laurie Stamatatos |