Site-specific conditions—soil conditions, climate, availability of suitable plant species, associated rhizosphere microbes, and type and level of contaminant(s)—influence the selection and performance of phytotechnologies. Each project is unique and must be custom-designed, installed, and maintained (ITRC 2009).
ITRC (Interstate Technology & Regulatory Council). 2009. Phytotechnology
Technical and Regulatory Guidance and Decision Trees, Revised. Phyto-3
Jump to a SubsectionGeneral Guidance | Contaminant-Specific Guidance | Phytotechnology-Specific Guidance | Plant Selection | Review Articles
The resources in this section offer guidance on general considerations for design and implementation of many types of phytotechnologies for a wide range of contamination problems.
The limitations to the technology must be considered before it can be implemented at a site:
- The depth of the contamination requiring treatment must be within the range of depth of plant root growth; thus, treatment of contaminated soil typically focuses on the upper 8 to10 inches of the soil horizon, although the roots of hybrid poplar trees, a species commonly used in phytoremediation, can grow to depths of about 15 feet.
- Contaminants must be in contact with the root zone to be treated; therefore, a denser root mass is preferred to help contact more of the contamination. Because treatment depends on this contact with the root zone, phytoremediation is limited by the rate of root growth. Slower growth rates increase the time required to treat a site, and winter months may shut down the treatment system completely while plants are dormant.
- Bioconcentration of contaminants up the food chain must be considered, particularly with metals and radionuclide contamination. Several phytoremediation mechanisms work by incorporating the contaminant into the plant or holding it within the root zone. The contaminated vegetation and root zone may impact plant-eating animals and soil organisms. Given the potential for bioconcentration, monitoring the fate of contaminants within the plants is important. To avoid bioconcentration in the food chain, contaminated plants can be harvested for disposal, destruction, or the extraction of metals for reuse.
- It is important to ensure that unwanted transfer of contaminants from soil to other media, such as the volatilization of organic compounds to the atmosphere through plant uptake and transpiration, does not occur or that the transfer results in contaminant destruction. Sites undergoing phytoremediation must be monitored to assess the fate of contaminants (USEPA 2006).
- Phytotechnologies are not always well understood by regulators.
Evaluating the limitations of phytoremediation in its various applications, as well as assessing its potential effectiveness at contaminated sites, can be done in laboratory and field studies prior to implementation.
USEPA. 2006. In Situ Treatment Technologies for Contaminated Soil: Engineering Forum Issue Paper. EPA 542-F-06-013.
Brownfields Technology Primer: Selecting and Using Phytoremediation for Site Cleanup
EPA 542-R-01-006, 2001
This primer explains the phytoremediation process, discusses the potential advantages and considerations in selecting phytoremediation to clean up brownfields sites, and provides information on additional resources about phytoremediation.
Chelating Agents for Land Decontamination Technologies
Tsang, D.C.W., I.M.C. Lo Rao, and Y. Surampalli (eds.).
American Society of Civil Engineers, Reston, VA. ISBN: 978-0-7844-1218-3, 294 pp, 2012
Chelating agents (or chelants) refer to ligands that can occupy multiple positions in the inner coordination sphere of the central metal ion, leading to the formation of multidentate metal-chelant complexes (or chelates). Chelating agents are able to enhance metal extraction from contaminated soil or sediment and facilitate metal mobility in the subsurface. This book focuses on the engineering applications of chelating agents for soil washing, soil flushing, phytoremediation, and electrokinetic remediation.
Evaluation of Dredged Material for Phytoreclamation Suitability
R.A. Price and C.R. Lee.
DOER-C3, 16 pp, 1999
This technical note describes a phased approach to evaluating the phytoreclamation alternative for treatment of contaminated dredged material to achieve its beneficial reuse.
Phytotechnology Technical and Regulatory Guidance and Decision Trees, Revised
Interstate Technology & Regulatory Council (ITRC) Phytotechnologies Team.
PHYTO-3, 187 pp, 2009
This document is an update to Phytoremediation Decision Tree (PHYTO-1 1999) and Phytotechnology Technical and Regulatory Guidance Document (PHYTO-2 2001) and replaces the previous documents entirely. It merges the concepts of both previous documents and includes new and practical information on the process and protocol for selecting and applying various phytotechnologies as remedial alternatives. The technical descriptions of phytotechnologies in this document concentrate on the functioning mechanisms: phytosequestration, rhizodegradation, phytohydraulics, phytoextraction, phytodegradation, and phytovolatilization. Decision trees (Remedy Selection, Groundwater, Soil/Sediment, and Riparian Zone) help guide the user through the application of phytotechnologies to a remediation project.
The Use of Vegetation in the Stabilization, Reclamation, and Remediation of Impacted INDOT Soils
M. McClain, M. Banks, and A. Schwab.
FHWA/IN/JTRP-2004/17, 71 pp, 2004
The cover title attaches to a brief fact sheet that presents PhytoRemediate®: Phytoremediation Decision Guide for Transportation Engineers, which was prepared for the Indiana Department of Transportation. This guide contains a design checklist and flowchart/decision tree that identifies the decision-making processes necessary to evaluate alternative remediation technologies and to undertake successful remediation of contaminated sites using phytotechnologies.
The following resources focus on the phytotechnology approaches suited to particular types of contaminants.
Emerging Technologies for the Remediation of Metals in Soils: Phytoremediation
Interstate Technology and Regulatory Cooperation (ITRC) Working Group. MIS-5, 40 pp, 1997
Enhanced Filtration and Contaminant Degradation Opportunities Offered by Natural Drainage Systems
J.K. Africa: Overview prepared during an internship with U.S. EPA's Office of Superfund Remediation and Technology Innovation, 20 pp, 2008
This paper focuses on the treatment of high molecular weight PAHs and discusses the potential for bioswales and rain gardens to mitigate contamination from runoff in urban settings.
Evaluation of Phytoremediation for Management of Chlorinated Solvents in Soil and Groundwater
EPA 542-R-05-001, 42 pp, 2005
This document is intended to help readers understand the proper application of planted systems to remediate groundwater contaminated with halogenated solvents. It assumes a general familiarity with environmental and regulatory processes, but little knowledge of plant-based remediation technologies. The document is written as an aid to understanding the mechanisms of how plants detoxify certain compounds under certain conditions.
Phytoremediation of Hydrocarbon-Contaminated Soils: Principles and Applications
R. Kamath, J.A. Rentz, J.L. Schnoor, and P.J.J. Alvarez.
Petroleum Biotechnology. Elsevier, ISBN-10: 0-444-51699-9, 151:447-478(2004)
This paper provides a foundation for understanding phytoremediation of petroleum hydrocarbon contaminated sites from principles to practice, discussing phytoremediation mechanisms, field-scale considerations, and regulatory and emerging issues.
Phytoremediation of Petroleum Hydrocarbons in Soil: Field Study Protocol
Remediation Technologies Development Forum (RTDF) Phytoremediation Action Team.
Protocols for Applying Phytotechnologies in Metal-Contaminated Soils
Barbafieri, M., J. Japenga, P. Romkens, G. Petruzzelli, and F. Pedron.
Plant-Based Remediation Processes. Springer, New York. Soil Biology, Vol. 35, ISBN: 978-3-642-35563-9, Chapter 2:19-37, 2013
This chapter presents practical considerations for planning the application of phytoextraction and phytostabilization to heavy metals in soils following a brief review of the mechanistic and practical application aspects of phytotechnologies.
A Resource Guide: The Phytoremediation of Lead in Urban, Residential Soils
J.L. Fiegl, et al. Northwestern University Web site, 2000
This Web site serves as a source of information for those concerned with lead contamination in soil. Phytoremediation can reduce the level of lead in the soil as well as provide a protective barrier. The use of the decision tree model developed by Northwestern University can help in the selection of appropriate plants.
Guidance has been developed that focuses on contamination problems that respond to specific phytotechnology mechanisms of contaminant degradation, removal, or containment to effect the transformation of pollutants or control of groundwater hydraulics.
Constructed Wetlands Treatment of Municipal Wastewaters
EPA 625-R-99-010, 166 pp, 1999
This manual discusses the capabilities of constructed wetlands, a functional design approach, and the management requirements to achieve the designed purpose.
Protocol for Controlling Contaminated Groundwater by Phytostabilization
V.L. Hauser, M.D. Gill, D.M. Gimon, and J.D. Horin.
Air Force Center for Environmental Excellence, 176 pp, 2001
This protocol focuses on the use of plants to remove groundwater a rate sufficient to stabilize movement of near-surface groundwater. Each step leading to the design and installation of a plant-based system for hydraulic control of contaminated groundwater is discussed. The decisions required to determine whether the approach is feasible are presented as a screening tool to aid in the decision-making process.
Technical and Regulatory Guidance for Constructed Treatment Wetlands
ITRC, 199 pp, 2003
Constructed treatment wetlands are man-made wetlands built to remove various types of pollutants from water that flows through them. Wetlands possess a rich microbial community in the sediment to effect the biochemical transformation of pollutants. They also are biologically productive and self-sustaining. These factors make constructed treatment wetlands a very attractive option for water treatment compared to conventional systems, especially when lifetime operating costs are compared. Constructed treatment wetlands utilize many of the mechanisms of phytoremediation.
The plant screening process assumes that the existing species at the site have been characterized. Plant selection begins by examining the potential resources:
- Species identified in phytotechnology databases and currently growing at the site.
- Species identified in phytotechnology databases and suitable to the region but not currently growing on the site.
- Hybrids or species related to a species identified as a candidate in either #1 or #2.
- Species not found in the databases but currently growing at the site or in the region.
- Genetically modified species designed to provide a specific remedial function (ITRC 2009).
Species suitability is determined based on ability of a species to grow and survive the site conditions (soil, contamination, climate, USDA hardiness zone, altitude, water availability). Other factors—growth rate, habit (perennial, annual, biennial, deciduous, evergreen), form (grass, forb, shrub, tree), rooting depth, water usage, disease/pest resistances, and tolerances—must be considered as well. Care should be taken to prevent introducing non-native and/or aggressive species that might disrupt the local ecology (ITRC 2009).
Information on suitable plants can be gathered from local, state, or federal agencies and offices, or from universities. Internet resources also are available that provide this type of information, such as the Plants Database of the USDA Natural Resources Conservation Service. For particular types of contaminants, documents and databases have been compiled to identify plants capable of adapting to certain levels of toxicity and containing or mitigating contaminants.
Candidate Herbaceous Plants for Phytoremediation of Energetics on Ranges
E.P.H. Best, T. Smith, F.L. Hagen, J. Dawson, and A.J. Torrey.
ERDC TR-07-11, 47 pp, 2007
This report identifies 5 grasses and 5 forbs as rapidly colonizing and short-term tolerant of TNT and RDX contamination in soil.
A Literature Review of the Use of Native Northern Plants for the Re-Vegetation of Arctic Mine Tailings and Mine Waste
P.W. Adams and S. Lamoureux.
Northwest Territories Environment and Natural Resources, Canada. 67 pp, 2005
Starting with a review of the effects of metals toxicity on plants, the work progresses into the topics of phytoremediation and the unique properties required for a plant to survive on the extreme climatic and nutrient-deficient conditions of a former mine site. Specific plant literature is reviewed.
Mine Waste Technology Program: Acid/Heavy Metal Tolerant Plants
EPA 600-R-07-114, 61 pp, 2007
This project selected ecotypes from native, indigenous plant species that demonstrated superior growth characteristics and sustainability on acidic, heavy metal-contaminated soils occurring varying elevations in western Montana. A number of metal-tolerant plants were identified/developed under the project, some suitable for release to commercial growers.
Overview of Native Plant Species with Remediation Potential That Have Applicability to Land Rehabilitation Objectives
U.S. Army Corps of Engineers Public Works Technical Bulletin. PWTB 200-1-53, 40 pp, 2007
This bulletin presents an overview of native plant species that have been shown to provide some level of improvement in soil contaminant persistence and/or mobility. Appendix A provides an overview of heavy metal, explosive, and petroleum contaminants, including likely contaminated areas on military training lands. Appendices B through F provide specific information for native plant species with remediation capacity adapted to a particular geographic region (Pacific Coast, Western Mountain, Central Plains, Southeast, and Northeast). Appendix G provides an overview of growth requirements for all plant species presented in this bulletin.
PhytoPetę: A Database of Plants That Play a Role in the Phytoremediation of Petroleum Hydrocarbons
University of Saskatchewan Web site, 1998
The searchable PhytoPetę database provides easy access to a wide range of information and assists users in the selection of plants for cleaning oil-contaminated sites.
Phytorem: Potential Green Solutions for Metal Contaminated Sites
Environment Canada. ETAD-3CD, CD-ROM, 2003
Phytorem is a fully searchable database that includes extensive information on the ability of numerous plants to tolerate, accumulate, and hyperaccumulate 19 different metals most commonly found contaminated sites, listing 776 species of vascular plants from 39 countries with some level of extraction capacity. The database also offers some information on the remediation potential of some bryophytes, algal, fungal, and bacterial species. Ordering information.
Selecting and Utilizing Populus and Salix for Landfill Covers: Implications for Leachate Irrigation
R.S. Zalesny Jr. and E.O. Bauer.
International Journal of Phytoremediation 9:497-511(2007)
Project development, clone selection, tree establishment, and evaluation of success metrics in the context of their importance to utilizing trees for phytoremediation of landfill leachates are discussed. Phytoremediation success can be improved by attention to proper genotypic screening and selection.
From Vegetated Ditches to Rice Fields: Thinking Outside the Box for Pesticide Mitigation
Moore, M.T., R. Kroger, J.L. Farris, M.A. Locke, E.R. Bennett, D.L. Denton, and C.M. Cooper.
Pesticide Mitigation Strategies for Surface Water Quality. American Chemical Society, ACS Symposium Series 1075, 29-37, 2011
In agricultural areas, management practices incorporating vegetation and phytoremediation have demonstrated success in reducing pesticide loads to rivers, lakes, and streams. This chapter focuses on constructed wetlands, drainage ditches, and rice fields.
The Role of Aquatic Ecosystems in the Elimination of Pollutants
Moore, M.T., R. Kroeger, and C.R. Jackson.
Ecological Impacts of Toxic Chemicals. Bentham Science Publishers, Ltd. eISBN: 978-1-60805-121-2, Chapter 11:225-237, 2011
This chapter focuses on some of the primary literature describing phytoremediation of organic pollutants (e.g., hydrocarbons and pesticides) and inorganic pollutants (e.g., metals and nutrients) to remove contaminants from the water column.