Phytoremediation of TPH-Contaminated Groundwater
Ari Ferro, ENSR/AECOM, Raleigh, NC

Assessment of Arsenic Phytoextraction Performance in the Spring Valley Area of Washington, DC Using High Intensity Composite Soil Sampling
Michael J. Blaylock, Edenspace Systems Corporation, Chantilly, VA

Does Metal Chelation Mobilize Aged PAHs in Vegetated and Non-Vegetated Contaminated Soils?
Samuel T. Gregory III, North Carolina State University, Raleigh, NC

Engineering Transgenic Plants for in situ Treatment of Explosives
Neil C Bruce, University of York, York, UK

Application of Endophytic Bacteria to Improve the Performances of Poplar for Phytoremediation and Biomass Production
Daniel van der Lelie, Brookhaven National Laboratory, Upton, NY

Seaweed Uptake, Concentration and Detoxification of Organic Pollutants in Marine Waters: TNT and PAHs
Donald Cheney, Northeastern University, Boston, MA

Phytoremediation of TPH-Contaminated Groundwater

Ari M. Ferro, Ph.D., National Dir. Phytoremediation Services, ENSR/AECOM, 7041 Old Wake Forest Road, Suite 103, Raleigh, NC 27616
Jennifer Cassada, B.S., Staff Specialist, ENSR/AECOM, 7041 Old Wake Forest Road, Suite 103 , Raleigh, NC 27616
Brett Berra, PE, Project Manager, Engineer, URS Corporation - North Carolina, 1600 Perimeter Park Dr., Morrisville, NC 27560, Tel: 919-461-1100
David Tsao, Ph.D., Team Leader, Environmental Technology, Atlantic Richfield, BP Business Center, Cantera I, 2nd Floor MC 2S, 28100 Torch Parkway 216A, Warrenville, IL 60555, Tel: 630-836-7169  

Groundwater phytoremediation systems were installed in 2003 near two adjacent retail outlets in Raleigh, North Carolina.  Groundwater at the site contains dissolved-phase petroleum hydrocarbons, and a contaminant plume is migrating toward a near-by creek.  The phytoremediation systems are comprised of poplar and willow trees planted in rows that are roughly perpendicular to the direction of groundwater flow, and the objective of the systems is to hydraulically control the rate of contaminant plume migration.  The tree stands are planted in two different areas of the site: Area A is more highly contaminated than Area B.  The water table is approximately 20 ft below ground surface, and therefore, special cultural practices were used to encourage the development of trees with very deep roots.  For example, at each planting location deep boreholes were drilled, the boreholes backfilled with a sand/compost mixture, and the trees planted in the backfill.  The young trees were irrigated using vertically installed subsurface drip lines, and the roots tend to follow the zone of moisture downward.  When the trees are sufficiently mature, the irrigation will be discontinued and the plants will use groundwater as a source of moisture.  An analysis of water balance parameters (e.g. groundwater flux, plant transpiration, precipitation) suggested that the mature stand will be effective for plume control.  As a method of assessing rooting depth during the period of stand development, soil moisture probes were installed in the backfill at various depths at the time of installation. During the 2005 growing season, individual trees within the stands in Areas A and B were monitored for rooting depth as well as for transpiration rates using thermal dissipation probes.  The main conclusion was that the cultural practices used to obtain deep rooted trees appeared to be effective in both Areas:  Roots had extended deeply in the backfill to within a few feet of the saturated zone; some trees appeared no longer to be dependent upon subsurface irrigation and apparently were able to use water from the saturated zone.  Rates of water use (seasonal averages) were higher in Area B (100 L/d) than in Area A (65 L/d), suggesting that the groundwater contaminants may be somewhat inhibitory.  During the 2006 growing season, studies will be carried out to further assess the extent of groundwater uptake.  Specifically, the ratio of stable isotopes of hydrogen will be analyzed in xylem sap, groundwater and vadose zone water.

Assessment of Arsenic Phytoextraction Performance in the Spring Valley Area of Washington, DC Using High Intensity Composite Soil Sampling

Michael J. Blaylock, Edenspace Systems Corporation, 15100 Enterprise Court, Suite 100, Chantilly, VA, 20151 Tel. 703-961-8700, Fax 703-961-8939, Email: blaylock@edenspace.com
Mark P. Elless, Edenspace Systems Corporation, 15100 Enterprise Court, Suite 100, Chantilly, VA, 20151 Tel. 703-961-8700, Fax 703-961-8939, Email: elless@edenspace.com

The residential area of Spring Valley encompasses approximately six hundred sixty-one (661) acres in the northwest section of Washington, D.C. During World War I, at the American University Experiment Station (AUES), the Department of Defense produced the arsenic-based chemical warfare agents, Lewisite and Adamsite. Chemists and engineers tested these agents in the areas surrounding the AUES, which is now known as the Spring Valley residential neighborhood. Investigative soil sampling indicated the presence of arsenic at levels above background and risk-based concentrations (RBCs).  In 2001, the Corps of Engineers initiated a removal action to address these areas of concern.  The main remediation technology to be applied at residences with elevated arsenic is excavation followed by backfilling with clean soil. This technology can be environmentally disruptive and expensive. Phytoremediation activities were initiated in 2004 as an alternative for specific areas to minimize destruction of existing trees and reduce restoration costs. An initial field verification study was conducted to evaluate the potential of phytoremediation to address the elevated arsenic soil concentrations. Based on these results, the field activities were expanded in 2005 to include additional sites and continued in 2006. Resuls obtained in 2005 demonstrated continued improvement in soil arsenic concentrations. However, variability in the measured soil arsenic concentrations hindered the ability to assess performance in some test plots. Therefore, an alternative soil sampling approach was developed to obtain samples more representative of the actual soil concentration. The approach utilizes a high number of individual soil cores collected from each sampling grid for compositing, homogenization and subsequent analysis. This paper will present the results obtained using this sampling approach and evaluate its ability adequately assess phytoremediation performance.

Does Metal Chelation Mobilize Aged PAHs in Vegetated and Non-Vegetated Contaminated Soils?

Student Presenter

Samuel T. Gregory III, North Carolina State University, 3136E Jordan Hall, CB 8008, 2800 Faucette Dr., Raleigh, NC 27695, Tel: 919-851-9286, Fax: 919-515-7559, Email: thornegregory@yahoo.com
Zachary K. Eyler, Withers & Ravenel, 111 MacKenan Drive, Cary, NC 27511, Tel: 704-517-7544, Fax: 919-515-7559, email: zkeyler@ncsu.edu
Thomas R. Crawford, North Carolina State University, CB 8008, 2800 Faucette Dr.  Raleigh, NC 27695, Tel: 919-233-0471, Fax: 919-515-7559, Email: trcrawfo@unity.ncsu.edu
EG Nichols, North Carolina State University, 3136G Jordan Hall, CB 8008, 2800 Faucette Dr. Raleigh, NC 27695, Tel: 919-513-4832, Fax: 919-515-7559, Email: elizabeth_nichols@ncsu.edu

The bioavailability of Polycyclic Aromatic Hydrocarbons (PAHs) in contaminated media is a major concern when assessing the impact of phytoremediation.  Evidence indicates that natural re-vegetation of sites with historical high levels of PAH contamination does attenuate these highly persistent contaminants.   There is great interest in the ability of vegetation to remove available PAHs from soil, but the processes of sequestration and rhizo-degradation by which this occurs are generally poorly understood.  Plant derived organic carbon moving into soils in the plant rhizosphere may enhance rhizo-degradation of PAHs by providing a ready source of labile carbon for microbial metabolism forcing PAH biodegradation, or plant derived organic matter can create an organic rich substrate for PAH sorption and sequestration.  Humin structures are a major recipient of this new plant derived organic carbon.  Disruption of humin complexes by chelation of polyvalent metal ions should release PAHs further sequestered by plant derived organic carbon, and thereby provide information about the extent of sequestration.

Engineering Transgenic Plants for in situ Treatment of Explosives

Neil C Bruce, CNAP, Department of Biology, University of York, York, YO10 5YW, UK

The contamination of the environment with toxic organic pollutants such as explosives presents a serious and widespread problem at sites across the world. Plants have a remarkable ability to extract compounds from the surrounding environment and have emerged as an affordable and effective clean-up strategy; however, the innate biodegradative abilities of plants are limited and often rates of uptake and metabolism can be slow. We asked whether plants could be engineered to yield an optimal system for in situ bioremediation of toxic explosives residues in soil. Progress has been made towards this goal and we have successfully combined the biodegradative capabilities of soil bacteria with the high biomass and stability inherent to plants. Explosives can be broadly classified into three groups: nitroaromatics (e.g. trinitrotoluene, TNT), nitramines (e.g. hexahydro-1,3,5-trinitro-1,3,5-triazine, RDX) and nitrate esters (e.g. nitroglyerin). We have isolated bacteria that degrade all the major classes of explosives. In order to achieve the removal of TNT and RDX from contaminated soil we have engineered plants expressing bacterial enzymes capable of TNT transformation and RDX degradation. Importantly, we have demonstrated that these transgenic plants are capable of restoring and maintaining the metabolic and genetic diversity of the rhizosphere soil.

References

French, C. E., Rosser, S. J., Davies, G. J., Nicklin, S. and Bruce, N. C. (1999). Biodegradation of explosives by transgenic plants expressing pentaerythritol tetranitrate reductase. Nature Biotechnology, 17: 491-494.
Hannink, N., Rosser, S. J., French, C. E., Basran, A., Nicklin, S., Murray, J. A. H. and Bruce, N. C. (2001). Phytodetoxification of 2,4,6-trinitroluene by transgenic plants expressing bacterial nitroreductase. Nature Biotechnology, 19: 2001, 1168-1172.
Rylott, E. L., Jackson, R., Edwards, J., Womack, G. L. Seth- Smith, H. M. B., Rathbone, D. A. Strand, S. E.  and Bruce, N. C. (2006). Identification of an explosive-degrading cytochrome P450 and its targeted application for the phytoremediation of RDX. Nature Biotechnology, 24: 216-219.

Application of Endophytic Bacteria to Improve the Performances of Poplar for Phytoremediation and Biomass Production

Safiyh Taghavi, Brookhaven National Laboratory (BNL), Biology Department, Building 463, Upton NY 11973, Tel: 631-344 5306, Fax: 631-344 3407, E-mail: taghavis@bnl.gov
Craig Garafola, Brookhaven National Laboratory (BNL), Biology Department, Building 463, Upton NY 11973, Tel: 631-344 4924, Fax: 631-344 3407, E-mail: cgarafol@bnl.gov
Bill Greenberg, Brookhaven National Laboratory (BNL), Biology Department, Building 463, Upton NY 11973, Tel: 631-344 4774, Fax: 631-344 3407, E-mail: billy@bnl.gov
Tanja Barac, Hasselt Universiteit Hasselt, Campus Diepenbeek, Environmental Biology, Agoralaan, building D, B-3590 Diepenbeek, Belgium, Tel.: + 32-11-268331, Fax: + 32 -11-268301, E-mail: Tanja.barac@uhasselt.be
Jaco Vangronsveld, Universiteit Hasselt, Campus Diepenbeek, Environmental Biology, Agoralaan, building D, B-3590 Diepenbeek, Belgium, Tel.: + 32-11-268331, Fax: + 32 -11-268301, E-mail: jaco.vangronsveld@uhasselt.be
Daniel van der Lelie, Brookhaven National Laboratory (BNL), Biology Department, Building 463, Upton NY 11973, Tel: 631-344 5349, Fax: 631-344 3407, E-mail: vdlelied@bnl.gov

Phytotechnologies are offering efficient tools and environmentally friendly solutions for cleanup of contaminated sites and water, improvement of food safety, carbon sequestration as a tool to reduce global warming, and the development of renewable energy sources, all of which are contributing to sustainable land use management. However, a profound knowledge is required of the complex interactions between plants and their associated microorganisms in order to exploit these interactions for the improvement of phytotechnologies for sustainable land use.

We demonstrated that endophytic bacteria can be efficiently used to improve phytoremediation of volatile organic contaminants: endophytic bacteria equipped with the appropriate degradation pathway significantly improved the in planta degradation of toluene and TCE in yellow lupine, resulting in its reduced phytotoxicity and release. We extended this concept to poplar, a plant species frequently used for the phytoremediation of groundwater contaminated with organic solvents.  Inoculation of poplar with the endophyte Burkholderia cepacia VM1468 (pTOM-Bu61), which is able to efficiently degrade toluene, resulted in reduced environmental release and phytotoxicity of toluene, thus confirming our earlier results obtained with the yellow lupine model system. A major difference between the yellow lupine and poplar experiments is the use of non-sterile plants for the inoculation of the poplar. Analysis of the microbial communities associated with non-inoculated control plants and poplar inoculated with VM1468 showed that the strain had failed to establish itself within the endogenous endophytic community. However, horizontal gene transfer of the toluene degradation plasmid pTOM-Bu61 had occurred to different species of poplar’s endogenous endophytic community.

During the course of this work we also noticed that certain endophytic bacteria affected the growth of their host plant, either in a positive or negative way. This observation is further exploited to improve the biomass production of poplar for carbon sequestration and biomass production.

Seaweed Uptake, Concentration and Detoxification of Organic Pollutants in Marine Waters: TNT and PAHs

Donald Cheney, Biology Dept., Northeastern University, Boston, MA, 02115; Tel: 617-373-2489, Fax: 617-373-3724; Email: d.cheney@neu.edu
Yen-Chun Liu, Biology Dept., Northeastern University, Boston, MA, 02115; Tel: 617-373-2489, Fax: 617-373-3724; Email: ycliu@ccs.neu.edu
Deana Aulisio, Dept. Chem. Engineering, University of New Hampshire, Durham, NH, Tel:  603-862-1445, Email: deana.aulisio@unh.edu
Kevin Gardner, Dept. Chem. Engineering, University of New Hampshire, Durham, NH, Tel: 603-862-4334, Email: kevin.gardner@unh.edu
Tavi Cruz-Uribe, Dept. Chem. Engineering, Oregon State University, Corvalis, OR, Tel: 541-737-3370, Email: cruzurib@yahoo.com
Gregory Rorrer, Dept. Chem. Engineering, Oregon State University, Corvalis, OR, Tel: 541- 737-3370, Email: rorrergl@engr.orst.edu.

According to a recent report by the EPA on the condition of our nation’s coastline, 27% of the Northeast’s estuaries have sediments contaminated with PCBs and PAHs. Currently, the most common method for eliminating PAHs and PCBs from contaminated marine waters and sediments is to excavate and dispose of the sediment. We are investigating the feasibility of a new approach for the removal of such compounds - growing “phycoremediating” seaweeds on contaminated sediments. In our initial work for the ONR, we were able to show that seaweeds are capable of quickly taking up and metabolizing the explosive compound 2,4,6-triitrotoluene (TNT). The most promising seaweed we examined was the one cell thick, sheet-like alga Porphyra yezoensis, which at a biomass density of 1.2 g/L and an initial TNT conc. of 10 mg/L, removed 100% of the TNT in just 72 hrs and produced the TNT byproducts 2-amino-4,6-dinitrotoluene (2-ADNT) and 4-amino-2,6-dinitrotoluene (4-ADNT). Currently, we are investigating the ability of seaweeds to take up and concentrate or metabolize PAHs, using the three-ringed phenanthrene as a model compound. As a first step, we are screening seaweed samples from polluted and unpolluted sites for their ability to metabolize 10 ppm phenanthrene. So far, the green seaweed Ulva (Enteromorpha) intestinalis looks most promising. At a density of 1g/30mL, Ulva plants removed over 90% of a 10 ppm phenanthene seawater solution in less than 24 hrs. Preliminary GC-MS analyses have detected one as yet unidentified possible breakdown product. This research was supported by grants from the Office of Naval Research Environmental Research Program and the USDA Aquaculture Program.

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