Introduction to Phytoremediation - CLU-IN

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Figure 3-3. Phytodegradation. organic compounds with a log k ow between 0.5 and 3.0 can be subject to phytodegradation within the plant. Inorganic nutrients are also remediated through plant uptake and metabolism. Phytodegradation outside the plant does not depend on log k ow and plant uptake. 3.5.5.1 Organics • Chlorinated solvents - The plant-formed enzyme dehalogenase, which can dechlorinate chlorinated compounds, has been discovered in sediments (McCutcheon 1996). - TCE was metabolized to trichloroethanol, trichloroacetic acid, and dichloroacetic acid within hybrid poplar trees (Newman et al. 1997a). In a similar study, hybrid poplar trees were exposed to wa- 29 ter containing about 50 ppm TCE and metabolized the TCE within the tree (Newman et al. 1997a). - Minced horseradish roots successfully treated wastewater containing up to 850 ppm of 2,4-dichlorophenol (Dec and Bollag 1994). • Herbicides - Atrazine in soil was taken up by trees and then hydrolyzed and dealkylated within the roots, stems, and leaves. Metabolites were identified within the plant tissue, and a review of atrazine metabolite toxicity studies indicated that the metabolites were less toxic than atrazine (Burken and Schnoor 1997). - The plant-formed enzyme nitrilase, which can degrade herbicides, has been discovered in sediments (Carreira 1996).
- A qualitative study indicated that the herbicide bentazon was degraded within black willow trees, as indicated by bentazon loss during a nurs ery study and by identification of metabolites within the tree. Bentazon was phytotoxic to six tree species at concentrations of 1000 and 2000 mg/L. At 150 mg/kg, bentazon metabolites were detected within tree trunk and canopy tissue samples (Conger and Portier 1997). - Atrazine at 60.4 g/kg (equivalent to about 3 times field application rates) was used to study phytodegradation in hybrid poplars (Burken and Schnoor 1997). - The herbicide bentazon was phytotoxic at concentrations of 1,000 to 2,000 mg/L, but allowed growth at 150 mg/L (Conger and Portier 1997). • Insecticides - The isolation from plants of the enzyme phosphatase, which can degrade organophosphate insecticides,may have phyotodegradation applications (McCutcheon 1996). • Munitions - The plant-formed enzyme nitroreductase, which can degrade munitions, has been discovered in sediments; this enzyme, from parrot feather, degraded TNT (McCutcheon 1996). - Hybrid poplar trees metabolized TNT to 4-amino- 2,6-dinitrotoluene (4-ADNT), 2-amino-4,6dinitrotoluene (2-ADNT), and other unidentified compounds (Thompson et al. 1998). - TNT concentrations in flooded soil decreased from 128 to 10 ppm with parrot feather (Schnoor et al. 1995b). • Phenols - Chlorinated phenolic concentrations in wastewater decreased in the presence of oxidoreductase enzymes in minced horseradish roots (Dec and Bollag 1994). 3.5.5.2 Inorganics • Nutrients - Nitrate will be taken up by plants and transformed to proteins and nitrogen gas (Licht and Schnoor 1993). 3.5.6 Root Depth Phytodegradation is generally limited to the root zone, and possibly below the root zone if root exudates are soluble, nonsorbed, and transported below the root zone. The degree to which this occurs is uncertain. 30 3.5.7 Plants The aquatic plant parrot feather (Myriophyllum aquaticum) and the algae stonewort (Nitella) have been used for the degradation of TNT. The nitroreductase enzyme has also been identified in other algae, ferns, monocots, dicots, and trees (McCutcheon 1996). Degradation of TCE has been detected in hybrid poplars and in poplar cell cultures, resulting in production of metabolites and in complete mineralization of a small portion of the applied TCE (Gordon et al. 1997; Newman et al. 1997a). Atrazine degradation has also been confirmed in hybrid poplars (Populus deltoides x nigra DN34, Imperial Carolina) (Burken and Schnoor 1997). Poplars have also been used to remove nutrients from groundwater (Licht and Schnoor 1993). Black willow (Salix nigra), yellow poplar (Liriodendron tulipifera), bald cypress (Taxodium distichum), river birch (Betula nigra), cherry bark oak (Quercus falcata), and live oak (Quercus viginiana) were able to support some degradation of the herbicide bentazon (Conger and Portier 1997). 3.5.8 Site Considerations 3.5.8.1 Soil Conditions Phytodegradation is most appropriate for large areas of soil having shallow contamination. 3.5.8.2 Ground and Surface Water Groundwater that can be extracted by tree roots or that is pumped to the surface may be treated by this system. Phytodegradation can also occur in surface water, if the water is able to support the growth of appropriate plants. 3.5.8.3 Climatic Conditions Phytoremediation studies involving phytodegradation have been conducted under a wide variety of climatic conditions. 3.5.9 Current Status Research and pilot-scale studies have been conducted primarily at Army Ammunition Plants (AAPs). These demonstrations include field studies at the Iowa AAP, Volunteer AAP, and Milan AAP (McCutcheon 1996). 3.5.10 System Costs Cost information has not been reported. 3.5.11 Selected References Bell, R. M. 1992. Higher Plant Accumulation of Organic Pollutants from Soils. Risk Reduction Engineering Laboratory, Cincinnati, OH. EPA/600/R-92/138. This paper includes an extensive literature review of the behavior of organic contaminants in plant-soil systems and the uptake of contaminants by plant. A wide variety of plant species and contaminant types are covered in
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
Page 33 and 34: sion of metals and metal concentrat
Page 35 and 36: Figure 3-2. Rhizodegradation. • L
Page 37 and 38: - PCP at 400 to 4100 mg/kg (in soil
Page 39: This paper introduces the important
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
Page 51 and 52: trial habitats are greatly improved
Page 53 and 54: • Achieve objectives - Perform qu
Page 55 and 56: could be more effectively treated t
Page 57 and 58: Table 4-2. (continued) • Sterile/
Page 59 and 60: The following are examples of commo
Page 61 and 62: arrier to block other site activiti
Page 63 and 64: 5.1 Remedial Objectives Chapter 5 R
Page 65 and 66: tems should not be used to infer th
Page 67 and 68: in soil and binding to soil were al
Page 69 and 70: The six case studies presented in t
Page 71 and 72: mum concentration of 640 ppb of 112
Page 73 and 74: a comparison of the performance of
Page 75 and 76: 6.2.6 Contacts Greg Harvey US Air F
Page 77 and 78: Figure 6-4. Sampling Grid Edward Se
Page 79 and 80: gravel drainage layer, and compacte
Page 81 and 82: variety had only a 54% survival rat
Page 83 and 84: surements are being taken to produc
Page 85 and 86: Phytoaccumulation: The uptake and c
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Project Name/ Size Primary Media an
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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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