Phytoremediation of Organic Compounds -
Phytoremediation of organic compounds consists of three mechanisms: rhizosphere biodegradation, phytovolatilization, and phytodegradation.
Plant roots produce natural substances (sugars, amino acids, organic acids,plant growth promoters, etc.) that promote microbial growth, and stimulate the biodegradation of organic compounds in the rhizosphere, the area immediately surrounding the root. Root growth creates channels and preferential paths that facilitate soil aeration in the root zone.
By the process of phytovolatilization certain hydrophylic organic contaminants can be taken up by plant roots and subsequently released into the atmosphere through the plant leaves. During this process of transpiration, these contaminants can be released in their original state after having undergone a transformation.
Phytodegradation consists of the uptake and transformation or metabolization of organic compounds within plant tissues (ie. roots, leaves, shoots). Plant compounds secreted by the roots can also play a role in phytodegradation.
- 4.3 Phytoremediation - FRTR Remediation Technologies Screening Matrix and Reference Guide, Version 4.0
- Phytotechnologies Overview - Clu-In - US EPA
- Campos et al. 2008. Review. Phytoremediation of organic pollutants. Spanish Journal of Agricultural Research, 6(Special issue, pp. 38-47
Recommended Analyses for Detailed Characterization
- Contaminant concentrations Footnotes1
- Organic matter content
- Nutrient concentrations Footnotes2
- Metals concentrations
- Soil water content
- Soil granulometry
- Evaluation of biological conditions and ecological factors
Recommended Trials for Detailed Characterization
- Seed germination toxicity test
- Root elongation toxicity test
- Greenhouse trials
Other Information Recommended for Detailed Characterization
- Contaminant delineation (area and depth)
- Presence of environmental receptors Footnotes3
- Soil stratigraphy
- Characterization of the hydrogeological system Footnotes4
- Conceptual site model with hydrogeological and geochemical inputs
- Allows for the treatment of residual organic contamination in the unsaturated zone, but can also be applied to the saturated zone
- Applies to organic contamination
- Contamination must be located near soil surface (< 1.0 m), or within the growth zone of the plant root system
- Can be used over large areas
- In situ
- Ex situ
- Dissolved contamination
- Free Phase
- Residual contamination
State of Technology
| Aliphatic chlorinated hydrocarbons |
Monocyclic aromatic hydrocarbons
| Non metalic inorganic compounds |
Policyclic aromatic hydrocarbons
This technique does not apply to aliphatic chlorinated hydrocarbons that contain 4 to 5 chlorine atoms. It is easier for plants to absorb and transfer organic compounds when the log of the octanol-water partition coefficient (log Kow) is between 0.5 and 0.3.
- < 1 year
- 1 to 3 years
- 3 to 5 years
- > 5 years
Secondary By-products and/or Metabolites
Generally, phytoremediation of organic compounds does not generate deleterious secondary by-products or metabolites. However, some contaminants may be transformed by microorganism in the rhizosphere and may generate metabolites which are more toxic than the initial compound. For example, the bacterial transformation of dichloroethene may produce vinyl chloride.
Limitations of the Technology
- The depth of contamination must be very limited (less than 1 meter depth for soil and less than 3 m depth for groundwater)
- Treatment time extends over several years (more than 5 years)
- High contaminant concentrations can have a toxic effect on the plants
- The geographic situation (climate/season)
- Presence of buildings or underground structures
- Contamination can be transferred from one medium to another (ex: from soil to air)
- This technology can only be applied at sites with a low potential risk to human and environmental health, eg. extended remediation times are permissible and the bioconcentration of toxic contaminants in plants is not an important risk factor
Complementary Technologies that Improve Treatment Effectiveness
Fertilizers rich in nitrogen stimulate plant growth as well as microbial activity and the rate of degradation.
Required Secondary Treatments
A management program for plant residues must be implemented.
The phytoremediation of organic compounds is a technique that has demonstrated its effectiveness on several sites.
Application examples are available at these addresses:
- Evaluation of Phytoremediation for Management of Chlorinated Solvents - RTDF - US EPA pdf
- Phytoremediation of TCE in Groundwater using Populus - Clu-In - US EPA
- U.S. EPA. 2005. Evaluation of Phytoremediation for Management of Chlorinated Solvents in Soil and Groundwater.EPA 542-R-05-001
The time required for completion of phytoremediation treatment varies according to the type of contaminants, the selected plants, the rhizosphere population and activity (for rhizodegradation only) and the physical and chemical conditions of the contaminated site.
- Federal Remediation Technology Roundtable. 2002. Remediation Technologies Screening Matrix and Reference Guide, Version 4.0. U.S.A.
- U.S. Environmental Protection Agency (EPA). 1998. A Citizen's Guide to Phytoremediation. EPA-542-F-98-011
- Center for public environmental oversight. 2002. TechTree: Phytoremediation. U.S.A.
- Remediation Technologies Development Funds. 2006. Phytoremediation of Organics Action Team (website). U.S.A. EPA.
- Pivetz, BE. 2001. Phytoremediation of Contaminated Soil and Groundwater at Hazardous Waste Sites. Ground Water Issue. U.S.EPA
- Environmental Protection Agency, 2000. Introduction to Phytoremediation. EPA/600/R-99/107
- EPA. 1989. Seed germination and root elongation toxicity tests in hazardous waste site evaluation: Methods development and applications. EPA/600/D-89/109
National Research Council
Michel Labrecque, Phd.
Institut de recherche en biologie végétale
Latest update provided by:
Jennifer Holdner, M.Sc.
Public Works Government Services Canada
Return to footnote1 Contaminant concentrations: Identification and concentration of all contaminants (sorbed, dissolved, and free phase).
Return to footnote2 Nutrient concentrations includes: ammonia nitrogen, total Kjeldahl nitrogen, nitrates and nitrites.
Return to footnote3 Presence of potential environmental receptors, above and below ground infrastructure, and the risk of off-site migration.
Return to footnote4 Complete characterization of the hydrogeological system includes: the depth and thickness of the aquifer, the direction and speed of the groundwater flow, etc.
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