Phytoremediation: What Every Good Chemical Engineer Should Know

1. Phytoremediation: What Every Good Chemical Engineer Should Know Steven C. McCutcheon, Ph.D., P.E., D.WRE Past President American Ecological Engineering Society Director, Region 5, American Society of Civil Engineers Faculty of Engineering, University of Georgia

2. Acknowledgements • Co-editor and coauthors of the book • Mike Saunders and students at Georgia Tech

3. Overview • What is phytoremediation? • Ecological engineering? • Biochemistry has been very, very good to this field Courtesy Stefan Trapp

4. Phytoremediation • Use of green plants and other autotrophic organisms to clean up 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. 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

6. Solar driven, self engineering to ensure nutrients/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

7. Ecological Engineering: • Design of sustainable systems, consistent with self design and other ecological principles, which integrate human society with the natural environment for the benefit of both (Mitsch and Jorgensen, 1989; Mitsch, 1996; Bergen et al., 1997)

8. 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)

9. Some Areas of Ecological Engineering • Wetland Restoration and Creation • Ecohydrology • Wetland Wastewater Treatment • Bioremediation, Phytoremediation, and Mycoremediation • 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

10. Observation 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)

11. 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

12. 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

13. 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

14. Metals and Elements

15. Species Contaminant Populusspp. (poplar, cottonwood) Hydrocarbons, chlorinat. solvents, explosives, MTBE, HCN, wastewater, & pesticides Salix spp. (willow) Hydrocarbons, HCN wastewater, leachate Ecalyptus spp., Tamarix Hydraulic control, arsenic Acer rubrum (red maple) Landfill leachate Pinus radiata, (Monterey pine) Municipal wastewater Morus rubra (red mulberry) PAHs Thespesia populnea (milo) and Prosopis pallida (kiawe) Petroleum hydrocarbons

16. IA IIA IIIA IVA VA VIA VIIA O 1 H+ H 7.8 1.0079 Suitable for wetland treat-ment Suit-able for phyto-extrac-tion KEYS Figure 1-1 Periodic Table of Elements Suitable for Phytoremediation 2 He 4.0026 3 Li+ LI 6.941 4 BeOH+ Be 9.012 Atomic number Species in freshwaters Symbol pConc. in US Rivers (-log M) Atomic Mass 5 B 10.81 6 HCO3- C 2.7 12.011 7 NO N 4.5 14.007 8 O2 O 3.5 15.9994 9 F- F 5.3 18.9984 10 Ne 20.179 11 Na+ Na 3.1 22.990 12 Mg2+ Mg 3.3 24.31 IIIBIVBVB VIB VIIB VIIIBIB IIB 13 Al(OH)3 Al 6.0 26.98 14 H4SiO4 Si 4.5 28.09 15 HPO P 5.4 30.974 16 SO42- S 3.4 32.064 17 Cl- Cl 3.4 35.453 18 Ar 39.948 19 K+ K 4.1 39.102 20 Ca2+ Ca 3.0 40.08 21 Sc 44.96 22 Ti 47.90 24 Cr6+,3+ Cr 6.7 52.00 25 Mn4+,2+ Mn 6.4 54.94 26 Fe3+,2+ Fe 6.0 55.85 27 Co2+ Co 58.93 28 Ni2+ Ni 7.3 58.71 29 Cu2+,+ Cu 7.0 63.546 30 Zn2+ Zn 6.6 65.38 31 Ga 69.72 32 Ge 72.59 33 HAsO As 7.9 74.92 34 SeO Se 8.6 78.96 35 Br- Br 5.9 79.904 36 Kr 83.80 37 Rb 85.47 38 Sr2+ Sr 87.62 39 Y 88.91 40 Zr 91.22 41 Nb 92.91 42 Mo 95.94 43 Tc 98.91 44 Ru 101.07 45 Rh 102.91 46 Pd 106.4 47 Ag 107.868 48 Cd2+ Cd 8.1 112.4 49 In 114.82 50 Sn2+ Sn 118.69 51 Sb 121.75 52 Te 127.60 53 I-,IO I 126.90 54 Xe 131.30 55 Cs+ Cs 132.91 56 Ba2+ Ba 6.0 137.34 57 La 138.91 72 Hf 178.49 73 Ta 180.95 74 W 183.85 75 Re 186.2 76 Os 190.2 77 Ir 192.2 78 Pt 195.09 79 Au 196.97 80 Hg(OH)2,+ Hg 8.0 200.59 81 Tl 204.37 83 Bi 206.96 84 Po (209) 85 At (210) 86 Rn (222) 87 Fr (223) 88 Ra 226.0 89 Ac (227) 92 +3,4,6 U 238 23 V 50.94 82 Pb2+,Pb+ Pb 7.7 207.20 General Advances • “Green liver model” -- enzymology and proteomics more mammalian than microbial • Oxidation or hydroxylation • Conjugation • Segregation, binding or excretion • Xenobiotic chemicals usually treatable if there is an analog among the spectrum of natural biomolecules • Transgenic plants possible and necessary for any unique molecules created by humankind • Tip of the iceberg of activities of plant proteins • Tolerance—insights from medicine and mammalian biochemistry • Rooting at depth & exploration of soil to clean up • Stand level transpiration  trees as solar pumps using ground water models to design Transition Elements

17. Olson et al.

18. Better Living through biochemistry: TPH, PAH, PCB, et al. • Aseptic tissue cultures to screen for plant v. microbial metabolism • Ecology of plant-microbe interactions • Grass rooting and hydrocarbon degradation (proof of concept) • Seeking proof of principle at numerous sites worldwide

19. pentachlorophenol4-chloroaniline Harms et al.

20. Harms et al.

21. Explosives • Extensive axenic tissue cultures to map transformation of TNT • Kinetics of transformation for wetland design – state of the practice • IA Army Ammunition Plant, successful wetland application

22. Nitella spp. in TNT Solution

23. ELISA for Field Testing and Characterization Courtesy of George Bailey, ERD, NERL, ORD, US EPA

24. Schwitzgruebel and Vanek

25. Subramanian and Shanks

26. Transcriptional Profiling: Arabidopsis Thaliana Root Responses to Explosives SAGE—Serial Analysis of Gene Expression—30 000 tags Very different metabolism RDX (Hexahydro-1,3,5-trinitro-1,3,5-triazine) TNT (Trinitrotoluene) putative glutathione transferase NPR1-like protein MYB like protein DnaJ-like protein Detoxification reactions that follow the green liver model of Sandermann carbamoyl phosphate synthetase small subunit gamma-VPE (vacuolar processing enzyme) transporter-like protein putative transcription factor putative serine/threonine-protein kinase putative peroxidase monodehydroascorbate reductase - like protein putative 3-dehydroquinate synthase vacuolar H+-ATPase subunit H (VHA-H) NAM, no apical meristem, - like protein unknown function; similar to bacterial tolB proteins vacuolar H+-transporting ATPase 16K chain P2 putative transcription factor alpha-hydroxynitrile lyase-like protein cytochrome P450, putative (TCCCCTATTA) no matches in genome

27. Chlorinated solvents • Biochemistry of TCE phytodegradation in terrestrial and wetland plants • Fate of TCE in indigenous vegetation • Demo– Control/treatment of plume • 5-y pilot, TCE Plume treatment/control • Ground water modeling to design tree plantations to control and treat solvent plumes

28. Nzengung, et al. (2003)

29. Tip of Mother Nature’s Bio-Iceberg • Identified approximately 100 enzymes involved in xenobiotic metabolism • Yet vascular plants seem to have at least 25000 genes that produce one or more biomolecules • Genomes of each species are diverse: • Arabidopsisthaliana—25 000 genes • Pinus taeda—110 000 genes • Maize, wheat, rice—25 000 to 40 000 genes • Native Australian flora even more diverse: millions of years of isolated evolution under stressful climatic conditions • Very unique biomolecules—most dangerous poisons on the planet that must be metabolized by some organism or environmental process • Should be extensive overlap with pharmaceutical and nutraceutical investigations

30. 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

31. Need for Transgenic Plants • Humankind has been more inventive of xenobiotics than the natural metabolism is capable of handling • Both metabolic and genetic engineering will be necessary to sustainably handle all the man-made chemicals possible • Feasibility has been proven: • Hg and As volatilization by transgenic Arabidopsis thaliana but there are stability problems in trees • Transgenic tobacco with human genes for cytochrome P450 1E1 to better metabolize trichloroethylene • Transgenic plants for explosives and nitroaromatics

32. Better Living through Plant Biochemistry • Sustainable recycling of some organic contaminants • Some plant metabolism faster, but several years and large land areas required • Metals accumulation in plants helps restore ecosystems inexpensively but takes time and residuals are a problem • Solar driven, usually inexpensive, but lacks process control

33. Recommendations for the Engineer’s Bookshelf