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| Resource Library > Technology Transfer > Programs and Initiatives > Phytoremediation |
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Phytoremediation
 Phytoremediation is the use of plants and trees to clean up contaminated soil and water. Growing, and, in some cases, harvesting plants on a contaminated site as a remediation method is a solar-energy driven passive technique that can be used along with, or in some cases in place of mechanical cleanup methods. Phytoremediation can be used to clean up metals, pesticides, solvents, explosives, crude oil, polyaromatic hydrocarbons, and landfill leachates.
Plants can serve as hydraulic pumps when their roots reach a depth where capillary action can draw moisture from the water table. For example, poplar trees can transpire between 50 to 300 gallons of water per day. This amount of water extraction can be an effective hydraulic control on the flow of subsurface water. Plants can also stabilize or remove metal contaminants from soil or groundwater by acting as bioaccumulators. Nickel, zinc, and copper are the best candidates for removal by phytoremediation because many different types of plants can extract these elements.
AFCEE is currently conducting several phytoremediation demonstrations:
- A "mature tree" study has been completed at Cape Canaveral Air Station. Live Oak, Saw-tooth Palmetto and Scrub Oak species in the midst of a TCE plume were evaluated for TCE transpiration and TCE transformation rates. Evapotranspiration rates were also measured. Mature trees were used in this study to obviate the waiting period for whips to grow into mature trees.
- An initial planting of 110 trees in 1998 was followed by 200 (early 2000) and 150 (spring 2000) additional trees at Travis AFB, CA. The plantings are being used as hydraulic control for a TCE plume. This is a long-term test of the ability of trees to control the movement of groundwater.
- A similar study is taking place at Altus AFB, OK. One hundred ten non seed-bearing hybrid cottonwood trees were planted in the fall of 1998. The plantings are being used as hydraulic control for a TCE plume. Soil moisture, groundwater levels, climatic conditions and sap flow rates are monitored remotely in this demonstration. A report on the results of the study will be released in the summer 2001.
- A new effort was launched in the summer 2000, with five large-scale plantings planned for Fairchild, Offutt, Hill and Whiteman AFBs. Plantings should be complete by early 2001.
References
The experience and results gained from the AFCEE phytoremediation efforts will be used to update the draft AFCEE Phytoremediation Protocol. Additional materials available for download include a fact sheet on basics of phytoremediation with additional information and points of contact. A draft protocol for Draft Protocol for Controlling Contaminated Groundwater by Phytostabilization is also available.
You can also access the bibliography of the work of the EPA Phytoremediation Handbook Team, collected in conjunction with the RTDF Phytoremediation Action Team. The bibliography is a combination of reference lists compiled by several individuals. It includes peer-reviewed journal articles, presentations and posters from conferences, book chapters, and articles from newspapers and magazines. The bibliography has 1,446 citations on phytoremediation or closely related subjects.
The Phytoremediation of Organics Action Team, established in 1997, is one of the six active Action Teams under the Remediation Technologies Development Forum (RTDF). The US EPA created the RTDF in 1992 to foster collaboration between the public and private sectors in developing innovative solutions to mutual hazardous waste problems. The Phytoremediation of Organics Action Team includes representatives from industry, government, and academia who share an interest in further developing and validating the of use of plants and trees to remediate organic hazardous wastes in soil and water.
Technical and Regulatory Guidelines Document for Constructed Treatment Wetlands (WTLND-1). This document was prepared by the Interstate Technology & Regulatory Council Wetlands Team. It describes the fundamental mechanisms of wetland contaminant removal and overall wetland functions and provides detailed descriptions of the various contaminant treatment objectives, treatment efficiencies, and goals of different constructed wetland applications. Detailed, site-specific predesign criteria and conceptual designs are outlined, followed by final design, post-construction activities, operation and maintenance, monitoring, and implementation costs. The document provides decision trees for each of the major constructed treatment wetland applications, designed to enable users to take basic information from a specific site and, through a flow chart,decide whether a particular wetland system is appropriate for the site.
Landfill covers. AFCEE offers a variety of information on landfill covers. Documents include technical details and other assistance for ET landfill cover selection, evaluation, design and use.
Perchlorate. Phytoremediation can be used to treat perchlorate in soils and groundwater.
Presentations and Materials at the AFCEE Technology Transfer Workshops. Various presentations and materials are available on this subject through the AFCEE Technology Transfer Workshop and its web page.
Final Addendum Report No. 3 to the Interim Technical Report for the Demonstration of Phytostabilization of Shallow Contaminated Groundwater Using Tree Plantings at Travis Air Force Base, California. The phytostabilization demonstration at Travis Air Force Base (AFB) was part of an initiative conducted by AFCEE. The multi-site program was to independently evaluate phytostabilization of contaminated groundwater. The purpose of this demonstration project was to test the ability of selected plants to remove groundwater through uptake and consumption in order to contain or control the migration of dissolved contaminants. Travis AFB was one of six Air Force bases that is taking part in this demonstration.
Phytoremediation Field Studies Database for Chlorinated Solvents, Pesticides, Explosives, and Metals. This document was prepared by two undergraduate students under internships with United States Environmental Protection Agency (EPA). Ana Hoffnagle was sponsored by the University of Arizona and Cynthia Green was sponsored by the Environmental Careers Organization. The paper briefly explains the concept of phytoremediation, details phytoremediation site considerations, and summarizes the successes and failures of field-scale sites where phytotechnologies have been applied or proposed (August 2004, 168 pages).
Use of Field-Scale Phytotechnology for Chlorinated Solvents, Metals, Explosives and Propellants, and Pesticides (US EPA, 2005)
This status report contains data about 79 phytoremediation projects in the US and Canada being addressed under state, local, or voluntary cleanup programs. The status report notes the types of contaminants treated, vegetation used, phytotechnology mechanisms, planting date, and project size, location, cost, and performance. EPA was unable to verify the available information for all projects and found gaps in the types of information available for many of the projects. Some of the projects were successful in remediating contamination, while others were not.
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