SELF-ENGINEERING IN PHYTOREMEDIATION: A Relationship With Ecological Engineering

1. 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 SELF-ENGINEERING IN PHYTOREMEDIATION: A Relationship With Ecological Engineering

2. 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.

3. Overview • Phytoremediation and self-engineering • Examples of self-engineering at hazardous waste sites • Roles of phytoremediation in ecological engineering Courtesy Stefan Trapp

4. 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

5. 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 Strengths and Limitations

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. Metals and Elements

13. 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

17. 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)

18. 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”

19. 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

20. 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

21. 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

22. 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

23. 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 Parrot feather (Myriophyllum aquaticum)

24. 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

25. 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

26. Aberdeen Proving Ground, MD

30. 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