Steven C' McCutcheon, Ph'D', PE

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SELF-ENGINEERING IN PHYTOREMEDIATION A
Relationship With Ecological Engineering

• Steven C. McCutcheon, Ph.D., PE
• U.S. EPA National Exposure
• Research Laboratory
• Athens, Georgia
• June 11, 2004, Fayetteville, Arkansas
• 4th Annual Conference of the American Ecological
  Engineering Society

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Acknowledgements

• Co-editor and coauthors of the book
  Phytoremediation
• Although this work was reviewed by EPA and
  approved for presentation, it may not necessarily
  reflect official Agency policy.

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Overview

• Phytoremediation and self-engineering
• Examples of self-engineering at hazardous waste
  sites
• Roles of phytoremediation in ecological
  engineering

Courtesy Stefan Trapp
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Phytoremediation

• Use of green plants and other autotrophic
  organisms to clean up and manage hazardous and
  other wastes
• Includes bioremediation by heterotrophic bacteria
  when plants provide carbon, nutrients, or habitat
  rhizodegradation
• Phytoextraction accumulates metals in
  aboveground tissues for harvest
• Phytodegradation or transformation
• Phytocontainment and stabilization
• Phytovolatilization and other types

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Strengths and Limitations

• Solar driven, self engineering to ensure
  nutrients and water
• Aesthetically
• pleasing, eco-restoration
• Should be cost effective

• Shallow depths of soil or water (rooting depths)
• Plants mainly transform contaminants
• Long durations and large land areas

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Potential Savings if the Promise of
Phytoremediation is Proven

• 0.25 to 0.5 billion at ammunition sites
• 1 to 2 billion for solvent plumes

1 trillion
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History of Phytoremediation

• Raskin coined the term in a 1991 proposal funded
  by U.S. EPA Superfund Program on metals
  accumulation
• Cunningham and Berti (1993) first used the term
  in the open literature
• Schnoor et al. (1995) first expanded the term in
  the open literature to include transformation of
  organics
• Brooks (1998) definitive on hyperaccumulation
• Raskin and Ensley (2000) and Terry and Banuelos
  (2000) definitive on metals accumulation and
  other inorganics
• McCutcheon and Schnoor (2003) definitive on
  organics and inorganics, and unified fundamental
  knowledge with plant-based engineering

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Other Seminal Work

• Work of Chaney and ARS dates to 1983 on metals
  accumulation
• Land treatment of waste near Berlin started about
  300 year ago
• Plant based engineering is now the basis of
  phytoremediation
• Wetland design
• Riparian buffer design
• Tree, grass, and crop plantation

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The Basic Tools

• Grass and tree plantation
• Agricultural cultivation
• Riparian and engineered buffers
• Land farming
• Created treatment wetlands
• Unit processes
• Roof gardens and living walls

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Figure 3-1
Increased human and ecological risk
Increased genetic engineering
Transgenic plants
Cultivated plants
Maintained indigenous plants
Sustainable native or indigenous organisms
Sustainable native or indigenous organisms
Maintained indigenous plants
Cultivated plants
Transgenic plants
Increased maintenance, monitoring, and control
required
Increased residual disposal
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Most Likely Applications

• Soil cleanup of oil spills and cyanide
• Tree plantations and buffers to control and treat
  groundwater and surface water contaminants
• Wetlands to remove organics from waters
• Brownfield stabilization and cleanup
• Vegetative caps on landfills
• Removal of some metals from soil and water

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Metals and Elements
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Figure 3-2
Year 2020
Design and application Increased relevance
Metabolic engineering
Ecosystem succession
Root management
Agronomic, silvicultural, wetland design
Ad hoc plant selection
1995
Landfill disposal
Incineration and composting
Energy recovery
Artifactual products
Residual management Increased relevance
Mining
2020 Year
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Self-Design

• The reorganization, substitution and shifting of
  an ecosystem (dynamics and functional processes)
  whereby it adapts to the environment superimposed
  upon it.
• (Mitsch, Jorgensen)

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Defining Ecological Engineering

• Environmental manipulation by man using small
  amounts of supplementary energy to control
  systems in which the main energy drives are still
  coming from natural sources (Odum, H. et al.,
  1963)
• Later refined to read, the design of human
  society with its natural environment for the
  benefit of both

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Some Basic Principles of Ecological Engineering2

• Ecosystems are self-designing
• Ecosystem structure function are governed by
  forcing functions
• Elements are recycled in ecosystems
• Homeostasis requires accordance between
  biological function chemical composition
• 2Mitsch Jorgensen, Ecological Engineering

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Basic Principles - cont

• Ecosystem processes have characteristic time and
  space scales
• Chemical biological diversity contribute to the
  buffering capacity of an ecosystem
• Ecosystems are most vulnerable at their
  geographical edges
• Ecotones are formed at transition zones
• Ecosystems are coupled with other ecosystems

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Basic Principles - cont

• Ecosystems with pulsing patterns are often highly
  productive
• Everything is linked to everything else in the
  ecosystem
• Ecosystems have feedback mechanisms, resilience
  and buffer capacities in accordance with their
  preceding evolution

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Some Areas of Ecological Engineering

• Wetland Restoration and Creation
• Ecohydrology
• Wetland Wastewater Treatment
• Bioremediation
• Bioengineering
• Stream bank stabilization
• Slope stabilization
• Stream and River Corridor Restoration and
  Engineering
• Riparian buffer designation and design
• Wetland design to control runoff
• Floodplain/Hyporheic Zone Management
• Carrying Capacity Studies
• Green Space Engineering

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Parrot feather (Myriophyllum aquaticum)

• One of the 1st observations of self-engineering
  Alabama Army Ammunition Plant, Childersburg
• Widespread TNT contamination 1960s to 1980s
• Beaver dams led to parrot feather and clean water
  and sediment
• Pine and grasses encroached on sterile bare soils
  to reduce TNT concentrations

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Laboratory and Pilots

• Plants protect enzymes and rapidly transform TNT
  and other explosives
• Dead plants maintain activity for weeks to allow
  new plants to colonize
• Crude enzyme extracts rapidly deactivated by
  proteases and metals

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Populus spp.

• Release of sugars and other simple exudates
  controls redox
• Reducing conditions favors microbial
  dehalogenation
• Evapotranspiration can halt ground water plume
  migration and pull contaminated water into vadose
  zone
• Contaminants taken into the trees are mineralized

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Aberdeen Proving Ground, MD
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Conclusions

• Phytoremediation involves many forms of
  self-engineering
• Understanding the degree of self-engineering is
  vital the sustainable ecological engineering of
  hazardous waste sites
• Many of the same plant-based engineering is
  common to phytoremediation and ecological
  engineering
• Thus, it is sound to conclude that
  phytoremediation is an important element of
  ecological engineering