Introduction to Phytoremediation - CLU-IN

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• Cattail (Typha latifolia) root microorganisms produced greater mineralization rates of LAS and LAE than did nonrhizosphere sediments (Federle and Schwab 1989). • Hybrid poplar tree (Populus deltoides X nigra DN-34, Imperial Carolina) rhizosphere soil contained significantly higher populations of total heterotrophs, denitrifiers, pseudomonads, BTX degraders, and atrazine degraders than did nonrhizosphere soil (Jordahl et al. 1997). 3.4.8 Site Considerations 3.4.8.1 Soil Conditions The physical and chemical soil conditions must allow for significant root penetration and growth. 3.4.8.2 Ground and Surface Water Although rhizodegradation is primarily soil-based, groundwater movement can be induced by the transpiration of plants bringing contaminants from the groundwater into the root zone. 3.4.8.3 Climatic Conditions Field studies that include rhizodegradation as a component have been conducted under in a wide variety of climates including the humid south, arid west, and the cold north. 3.4.9 Current Status The following list provides information on the status or application of rhizodegradation studies: • Rhizodegradation was first extensively studied in relation to the biodegradation of pesticides in agricultural soils. • Numerous laboratory and greenhouse studies and several field studies have been conducted, including a field study conducted at the McCormick & Baxter Superfund Site. • “Hot spots” of higher contaminant concentrations can be excavated and treated using other technologies, or landfilled. Rhizodegradation could be applied as a polishing or final step after active land treatment bioremediation has ended. • A TPH/PAH subgroup has been established as part of the RTDF Phytoremediation of Organics Action Team to examine rhizodegradation. The Petroleum Environmental Research Forum is also examining rhizodegradation in the phytoremediation of petroleum hydrocarbons. 3.4.10 System Cost Cost information for rhizodegradation is incomplete at this time. 3.4.11 Selected References Anderson, T. A., and J. R. Coats (eds.). 1994. Bioremediation Through Rhizosphere Technology, ACS Symposium Series, 27 Volume 563. American Chemical Society, Washington, DC. 249 pp. This is a collection of 17 articles examining rhizodegradation. The papers introduce the concepts involved in rhizodegradation; discuss interactions between microorganisms, plants, and chemicals; and provide examples of rhizodegradation of industrial chemicals and pesticides. Anderson, T. A., E. A. Guthrie, and B. T. Walton. 1993. Bioremediation in the Rhizosphere. Environ. Sci. Technol. 27:2630-2636. This literature review summarizes research work conducted on a variety of contaminants (pesticides, chlorinated solvents, petroleum products, and surfactants). Anderson, T. A., and B. T. Walton. 1995. Comparative Fate of [ 14 c]trichloroethylene in the Root Zone of Plants from a Former Solvent Disposal Site. Environ. Toxicol. Chem. 14:2041-2047. Exposure chambers within an environmental chamber were used with a variety of plant types and with radiolabeled TCE. Mineralization rates were greater in vegetated soils than in unvegetated soils. Aprill, W., and R. C. Sims. 1990. Evaluation of the Use of Prairie Grasses for Stimulating Polycyclic Aromatic Hydrocarbon Treatment in Soil. Chemosphere. 20:253-265. Eight prairie grasses were examined using chambers constructed of 25-cm-diameter PVC pipe. PAH-spiked soil at 10 mg PAH/kg soil was added to the chambers prior to seeding. Soil, leachate, and plant tissue samples were collected during the study. PAH disappearance was greater in planted chambers compared to unplanted chambers. Ferro, A. M., R. C. Sims, and B. Bugbee. 1994a. Hycrest Crested Wheatgrass Accelerates the Degradation of Pentachlorophenol in Soil. J. Environ. Qual. 23:272-279. A growth-chamber study conducted using radiolabeled pentachlorophenol indicated that mineralization was greater in planted systems than in unplanted systems. Fletcher, J. S., and R. S. Hegde. 1995. Release of Phenols by Perennial Plant Roots and their Potential Importance in Bioremediation. Chemosphere. 31:3009-3016. Greenhouse studies identified chemical and microbiological evidence for the occurrence of rhizodegradation. The potential for biodegradation within the root zone was determined to be dependent on the particular plant species and exudates produced by the plant. Schnoor, J. L., L. A. Licht, S. C. McCutcheon, N. L. Wolfe, and L. H. Carreira. 1995a. Phytoremediation of Organic and Nutrient Contaminants. Environ. Sci. Technol. 29:318A-323A.
This paper introduces the important concepts for rhizodegradation and phytodegradation, including the role of plant enzymes. Laboratory and field research for TNT, pesticides, and nutrient contaminants is summarized. Applications and limitations of phytoremediation are discussed, and field applications of phytoremediation are tabulated. Schwab, A. P. 1998. Phytoremediation of Soils Contaminated with PAHs and Other Petroleum Compounds. Presented at: Beneficial Effects of Vegetation in Contaminated Soils Workshop, Kansas State University, Manhattan, KS, January 7-9, 1998. Sponsored by Great Plains/Rocky Mountain Hazardous Substance Research Center. This presentation summarizes the methods and results of field test plots at a variety of geographic and climatic regions. Dissipation of TPH was greater in planted plots than in unplanted plots, and differences were seen in the growth and effectiveness of different plant species. 3.5 Phytodegradation 3.5.1 Definition/Mechanism Phytodegradation (also known as phytotransformation) is the breakdown of contaminants taken up by plants through metabolic processes within the plant, or the breakdown of contaminants external to the plant through the effect of compounds (such as enzymes) produced by the plants. As shown in Figure 3-3, the main mechanism is plant uptake and metabolism. Additionally, degradation may occur outside the plant, due to the release of compounds that cause transformation. Any degradation caused by microorganisms associated with or affected by the plant root is considered rhizodegradation. 3.5.1.1 Uptake For phytodegradation to occur within the plant, the compounds must be taken up by the plant. One study identified more than 70 organic chemicals representing many classes of compounds that were taken up and accumulated by 88 species of plants and trees (Paterson et al. 1990). A database has been established to review the classes of chemicals and types of plants that have been investigated in regard to their uptake of organic compounds (Nellessen and Fletcher 1993b). Uptake is dependent on hydrophobicity, solubility, and polarity. Moderately hydrophobic organic compounds (with log k ow between 0.5 and 3.0) are most readily taken up by and translocated within plants. Very soluble compounds (with low sorption) will not be sorbed onto roots or translocated within the plant (Schnoor et al. 1995a). Hydrophobic (lipophilic) compounds can be bound to root surfaces or partitioned into roots, but cannot be further translocated within the plant (Schnoor et al. 1995a; Cunningham et al. 1997). Nonpolar molecules with molecular weights
Page 1 and 2: Introduction to Phytoremediation Na
Page 3 and 4: Foreword The U.S. Environmental Pro
Page 5 and 6: Table of Contents Foreword ........
Page 7 and 8: Figures Figure 2-1. Mechanisms for
Page 9 and 10: Acronyms AAP Army Ammunition Plant
Page 11 and 12: Acknowledgements This Introduction
Page 13 and 14: • Chapter 3 provides a literature
Page 15 and 16: Figure 2-1. Mechanisms for phytorem
Page 17 and 18: Table 2-2. Root Depth for Selected
Page 19 and 20: Table 2-3. Phytoremediation at Supe
Page 21 and 22: egulated by the requirement. The Ma
Page 23 and 24: site. Plants and animals recolonize
Page 25 and 26: This chapter presents a literature
Page 27 and 28: Figure 3-1. Phytoextraction. The fo
Page 29 and 30: In this literature review of resear
Page 31 and 32: Rhizofiltration has not been evalua
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Page 35 and 36: Figure 3-2. Rhizodegradation. • L
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Page 41 and 42: - A qualitative study indicated tha
Page 43 and 44: Figure 3-4. Phytovolatilization. 3.
Page 45 and 46: Newman, L. A., C. Bod, N. Choe, R.
Page 47 and 48: 3.8 Vegetative Cover Systems 3.8.1
Page 49 and 50: also be used in the treatment of so
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Page 57 and 58: Table 4-2. (continued) • Sterile/
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Page 75 and 76: 6.2.6 Contacts Greg Harvey US Air F
Page 77 and 78: Figure 6-4. Sampling Grid Edward Se
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Project Name/ Size Primary Media an
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Adler, T. 1996. Botanical Cleanup C
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Ferro, A. M., L. Stacishin, W. J. D
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Newman, L. A., S. E. Strand, D. Dom
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Appendix D Common and Scientific Na
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Scientific Name Listed First Scient
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