Design and Monitoring Considerations
Many site-specific features factor into the selection and performance of phytotechnologies, which must be designed, installed, and operated to accommodate the unique characteristics of the site. Factors such as climate, source water, contaminant levels, site conditions (e.g. depth to groundwater, soil properties) operation and maintenance, and site layout are key design considerations in phytoremediation. A few resources that cover phytoremediation design include Interstate Technology & Regulatory Council's Phytotechnology Technical and Regulatory Guidance and Decision Trees, Revised (2009) and the Remediation Technologies and Development Forum's Evaluation of Phytoremediation for Management of Chlorinated Solvents in Soil and Groundwater (2005).
Monitoring the performance of phytoremediation systems is an important component of successful treatment and will assist in generation of site-specific operation and maintenance protocols (e.g., harvesting and disposal cycles). Phytoforensic tools such as dendrochemistry (the analysis of deep core tree rings or roots) can provide valuable information in both phytoinvestigation and phytoforensic stages of system design and operation (Balouet et al., 2007; Balouet et al., 2009). Additional resources on methods of phytoforensic monitoring can be found Phytoremediation of Contaminated Soil and Ground Water at Hazardous Waste Sites (Pivetz, 2001).
There are several limitations to phytotechnologies that must be carefully considered during the remedial selection phase of the project. These include:
- Depth of Contamination: 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 to 10 inches of the soil horizon, although the roots of hybrid poplar trees, a species commonly used in phytoextraction and phytohydraulics, can grow to depths of about 15 feet. Further, a commercially available phytoremediation hybrid technology known as TreeWell® claims to extend treatment beyond these depths (10 to 50+ ft below ground surface) (Gestler et al., 2019).
- Growth Rate: The root zone must be in contact with contaminants to be treated; therefore, a dense root mass is preferred to increase this contact. The rate of root growth will affect the time required to treat a site, and winter months may render treatment ineffective while plants are dormant. In addition, the potential for bioconcentration of contaminants, particularly metals and radionuclides, up the food chain makes monitoring the fate of contaminants within the plants particularly important. The contaminated vegetation and root zone may impact plant-eating animals and soil organisms. To avoid bioconcentration, contaminated plants can be harvested for disposal, destruction, or the extraction of metals for reuse (U.S. EPA 2006).
- Seasonal Effects: Plant performance may be dependent on seasonal variations (e.g. extreme low and high temperature, drought conditions). Regional climate variations and soil type will also affect viable plant selection. Though to some extent, this limitation can be addressed with engineering approaches such as irrigation, soil additives, and planting techniques (Martino et al., 2019).
- Cross Media Contamination: Another limitation is the potential for unwanted cross-media transfer of contaminants, such as the uptake and transpiration of organic compounds from soil to the atmosphere. The potential advantages and disadvantages of the effects of phytovolatilization and phytosequestration must be assessed on a site-specific basis (Limmer and Burken 2016; U.S. EPA 2006).
- Operation and Maintenance: Phytotechnologies require some maintenance activities including harvesting, irrigation, pruning, and replanting. In addition, sites undergoing phytoremediation must be monitored to assess the fate of contaminants (U.S. EPA 2006).
If its limitations are appropriately considered, phytotechnologies selected for full-scale treatment of contaminated sites have the potential to be a low cost, sustainable, and effective alternative to more intrusive methods of site cleanup. In addition to its perception as a "green," low-tech, and energy efficient treatment alternative, phytotechnologies can have the added benefit of reducing or preventing erosion and fugitive dust emissions at some sites (Pivetz et al., 2001).
Balouet, J. C., et al., 2007. Applied Dendroecology and Environmental Forensics. Characterizing and Age Dating Environmental Releases: Fundamentals and Case Studies. Environmental Forensics 2007, 8, 1-17. (Abstract)
Balouet, J. C., et al., 2009. Use of Dendrochronology and Dendrochemistry in Environmental Forensics: Does It Meet the Daubert Criteria? Environmental Forensics 2009, 10, 268-276. (Abstract)
Gestler et al., 2019. Engineered Phytoremediation of Contaminated Aquifers — Adapting a Natural System to Meet Remedial Goals. Geosyntec Consultants. RemTech 2019.
Limmer and Burken, 2016. Phytovolatilization of Organic Contaminants. Environ. Sci. Technol. 2016, 50, 13, 6632â€“6643. (Abstract)
Martino et al., 2019., L. A Hybrid Phytoremediation System for Contaminants in Groundwater. Environ Earth Sci 78, 664, (Abstract).
Pivetz, B., 2001. Ground Water Issue: Phytoremediation of Contaminated Soil and Ground Water at Hazardous Waste Sites. EPA-542-S-01-500. U.S. EPA Office of Solid Waste and Emergency Response, February.
RTDF (Remediation Technologies and Development Forum). Evaluation of Phytoremediation for Management of Chlorinated Solvents in Soil and Groundwater. EPA 542-R-05-001. January 2005.
U.S. EPA. 2006. In Situ Treatment Technologies for Contaminated Soil: Engineering Forum Issue Paper. EPA 542-F-06-013.
U.S. EPA, 2004. Constructed Treatment Wetlands. EPA 843-F-03-013. August.
Engineered Phytoremediation of Contaminated Aquifers — Adapting a Natural System to Meet Remedial Goals.
Geosyntec Gestler, R. J. Linton, K. Berry-Spark, E. Gatliff, P. Thomas.
RemTech 2019. 24 slides
Use of Dendrochronology and Dendrochemistry in Environmental Forensics: Does It Meet the Daubert Criteria?
Balouet, J.C., K.T. Smith, D. Vroblesky, and G. Oudijk.
Environmental Forensics 2009, 10, 268-276. (Abstract)
Applied Dendroecology and Environmental Forensics. Characterizing and Age Dating Environmental Releases: Fundamentals and Case Studies.
Balouet, J.C., G. Oudijk, K. T. Smith, I. Petrisor, K. Grudd, B. Stocklassa.
Environmental Forensics 2007, 8, 1-17. (Abstract)
Ground Water Issue: Phytoremediation of Contaminated Soil and Ground Water at Hazardous Waste Sites.
EPA-542-S-01-500. U.S. EPA Office of Solid Waste and Emergency Response February
Suitability of Miscanthus Species for Managing Inorganic and Organic Contaminated Land and Restoring Ecosystem Services. A Review (Abstract)
Candidate Herbaceous Plants for Phytoremediation of Energetics on Ranges
Best, E.P., T. Smith, F.L. Hagen, J. Dawson, and A.J. Torrey.
ERDC TR-07-11, 47 pp, 2008
Mine Waste Technology Program: Acid/Heavy Metal Tolerant Plants
EPA 600-R-07-114, 61 pp, 2007
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
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)
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
Using Native Species at Superfund Sites: The Tonolli Metals Site Project
R.J. Nadeau, S.C. Fredericks, and J.L. Brown.
Land and Water 46(4):29-32(2002)
General and Technology Application Resources
Field Trials of Phytomining and Phytoremediation: A Critical Review of Influencing Factors and Effects of Additives (Abstract)
Wang, L., D. Hou, Z. Shen, J. Zhu, X. Jia, Y.S. Ok, F.M.G. Tack, and J. Rinklebe.
Critical Reviews in Environmental Science and Technology 50(24): 2724-2774(2020)
Best Practice Guidance for Practical Application of Gentle Remediation Options (GRO)
Puschenreiter, M. et al.
The GREENLAND Project, 18 pp + 61 pp appendices, 2014
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
Phytotechnologies for Site Cleanup
EPA 542-F-10-009, 2010
Phytotechnology Technical and Regulatory Guidance and Decision Trees, Revised
Interstate Technology & Regulatory Council (ITRC) Phytotechnologies Team. Report No. PHYTO-3, 187 pp, 2009
The Use of Soil Amendments for Remediation, Revitalization, and Reuse
Evaluation of Phytoremediation for Management of Chlorinated Solvents in Soil and Groundwater
EPA 542-R-05-001, 42 pp, 2005
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)
The Use of Vegetation in the Stabilization, Reclamation, and Remediation of Impacted INDOT Soils
M. McClain, M. Banks, and A. Schwab. Report No. FHWA/IN/JTRP-2004/17, 71 pp, 2004
Technical and Regulatory Guidance for Constructed Treatment Wetlands
Interstate Technology & Regulatory Council (ITRC), Report No. WTLND-1, 199 pp, 2003
Brownfields Technology Primer: Selecting and Using Phytoremediation for Site Cleanup
EPA 542-R-01-006, 2001
Guiding Principles for Constructed Treatment Wetlands: Providing Water Quality and Wildlife Habitat
EPA Office of Wetlands, Oceans and Watersheds, EPA 843-B-00-003, 25 pp, 2000
Draft 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, 1999
Free Water Surface Wetlands for Wastewater Treatment: A Technology Assessment
EPA Office of Wastewater Management and U.S. Bureau of Reclamation, 155 pp, 1999
Also see fact sheet
A Handbook of Constructed Wetlands: A Guide to Creating Wetlands for Agricultural Wastewater, Domestic Wastewater, Coal Mine Drainage, Stormwater
Prepared for the USDA Natural Resources Conservation Service and EPA Region 3, 53 pp 1995
Subsurface Flow Constructed Wetlands For Wastewater Treatment: A Technology Assessment
EPA Office of Water, 832-R-93-008, 87 pp, 1993