M.K. Banks and K. Reilley are in the Civil Engineering Dept. L.C. Davis is in the Biochemistry Dept. L.E. Erickson and N. Muralidharan are in the Chemical Engineering Dept. A.P. Schwab is in the Agronomy Dept.
Beneficial effects of vegetation have been reported in soils contaminated with metals as well as organic compounds. The application of vegetation to the stabilization, control, and remediation of soils contaminated with metals has been reviewed recently by Pierzynski et al. (28). The present review will be limited to organic compounds that may be transformed and inorganic compounds that may be beneficial to plants and microorganisms. The emphasis will be on recent developments that are not included in the reviews of Shimp et al. (30) and Anderson et al. (38).
Vegetation has been used beneficially in the in situ bioremediation of contaminated soil, as a biofilter to adsorb and biodegrade contaminants in air and water, and in buffer zones for control and treatment of leachate and surface waters (10, 12, 18, 22, 27, 30). Specific potential pollution prevention applications include the use of grasses and trees at the edges of fields along the banks of streams to capture and transform pesticides and fertilizers, grass waterways below animal feedlots to manage runoff associated with rainfall events, and vegetation at the edge of landfills to utilize and transform compounds in landfill leachate. Wetlands biofilter wastewater treatment systems have been developed to biodegrade organic compounds (30).
The results for phenol in Tables 2 and 4 indicate that most of the phenol disappeared; the amount in the effluent was very small. Phenol was not found in the gas phase. The experimental results which include measurements of carbon dioxide evolution suggest that most of the phenol was transformed and biodegraded. Anaerobic biodegradation of phenol in the saturated zone may have taken place, also. Under conditions where all of the influent water is evapotranspired, it appears that all of the contaminant can be transformed and remediated.
A carbon mass balance on the two chambers together showed that about 50 mmoles/day of the inlet carbon appeared to be biodegraded. The measured production of CO2 was about 70100 mmoles/day with plants and the contaminants and about 2/3 as much when the contaminants were not being fed. Thus, approximately 23-33 mmoles carbon/day appears to be associated with CO2 production due to biodegradation of contaminants. This leaves 17-27 mmoles carbon/day associated with biomass formation and the incorporation of carbon into the soil. In one year, the organic carbon content of the soil would increase by about 0.001 g/g of soil based on this level of carbon incorporation. Because of root exudates and variations of soil organic carbon content with depth from 0. 3 % at the bottom to 1. 8 % near the surface, the increase in soil organic carbon due to biodegradation of the contaminants was not determined independently.
The uptake of anthracene and pyrene by alfalfa and fescue plants has been investigated by Al-Assi (2). He concludes that these compounds do not accumulate in these plants.
Anderson (3) has reported that the rhizosphere of growing plants has a beneficial effect on the transformation of trichloroethylene (TCE). When growing plants were present, the microbial activity, biomass, and degradation of TCE in rhizosphere soils were found to be significantly greater than corresponding nonvegetated soils (3,5,35). The presence of vegetation had a positive effect on the transformation of TCE to carbon dioxide.
Ferro et al . (37) has reported that mineralization rates of pentachlorophenol are 3 . 5 times greater in vegetated soil where Hycrest crested wheatgrass (Agropyron desertorum) is growing compared to soil without vegetation. Pentachlorophenol was also found in the plant roots and shoots. At an initial concentration of 100 mg/kg dry weight of soil, the growth of the vegetation was affected by the pentachlorophenol.
Bedell (9) and Mueller et al. (20, 21), have investigated the late of explosive compounds such as di-and trinitrotoluenes (DNT and TNT) in the presence of plants. The results show that uptake and biotransformation of nitrated toluenes occurs when Jimson weed (Datura innoxia) and Lycopersicon peruvianum, a wild tomato species, are grown in soils containing DNT and TNT. Radiolabeled TNT was transformed to aminobenzyl alcohols, aminobenzaldehydes, and aminobenzoic acids. When plants were grown in soils containing 500, 750, and 1000 ppm of TNT, there was evidence of phytotoxic effects at 1000 ppm of TNT. The Lycopersicon peruvianum and the Datura quercofolia showed signs of stress which included yellowing and loss of leaves and flowers; however, the Datura innoxia looked quite healthy in soils with 1000 ppm of TNT (21) .
1. Air and Waste Management Association's 86th Annual Meeting and Exhibition, Air and Waste, 43, 593-704, 1993. 2. Al-Assi, A.A., Uptake of Polynuclear Aromatic Hydrocarbons by Alfalfa and Fescue, M.S. Thesis, Kansas State University, Manhattan, KS, 1993. 3. Anderson, T.A., Comparative Plant Uptake and Microbial Degradation of Trichloroethylene in the Rhizosphere of Five Plant Species, ORNL/TM-12017, Oak Ridge National Laboratory, Oak Ridge, TN, 1992. 4. Anderson, T.A., E.L. Kruger, and J.R. Coats, "Enhanced Microbial Degradation in the Rhizosphere of Plants from Contaminated Sites," Paper 93-WA-89.01, Proceedings of the 86th Annual Meeting and Exhibition, Air and Waste Management Association, Pittsburgh, PA, 1993. 5. Anderson, T.A. and B.T. Walton, "Fate of Trichloroethylene in Soil-Plant Systems" American Chemical Society Extended Abstract, Division of Environmental Chemistry, pp. 197200, August 25-30, 1991. 6. Aprill, W. and R.C. Sims, "Evaluation of the Use of Prairie Grasses for Stimulating Polycyclic Aromatic Hydrocarbon Treatment in Soil," Chemosphere 20, 253-265, 1990 . 7. Banks, M.K. and A.P. Schwab, "Microbial Degradation of Hazardous Organics in the Rhizosphere: A Review," Paper 93WA-89.05, Proceedings of the 86th Annual Meeting and Exhibition, Air and Waste Management Association, Pittsburgh, PA, 1993. 8. Banks, M.K. and A.P. Schwab, "Biologically Mediated Dissipation of Polyaromatic Hyrocarbons in the Root Zone," In Microbial Degradation of Organic Chemicals in the Rhizosphere: Implications for Bioremediation, T.A. Anderson and J.R. Coats, Editors, ACS Symposium Series, In Press, 1993. 9. Bedell, G.W., "Higher Plant Bioremediation," The World and I, pp. 260-267, December, 1992. 10. Davis, L.C. C. Chaffin, N. Muralidharan, V.P. Visser, W.G. Fateley, L.E. Erickson, and R.M. Hammaker, "Monitoring the Beneficial Effects of Plants in Bioremediation of Volatile Organic Compounds, " Proceedings of the Conference on Hazardous Waste Research, Kansas State University, Manhattan, KS, 236-249, 1993. 11. Davis, L.C., L.E. Erickson, E. Lee, J.F. Shimp, and J.C. Tracy, "Modeling the Effects of Plants on the Bioremediation of Contaminated Soil and Ground Water, " Environmental Progress, 12, 67-75, 1993. 12. Davis, L.C., N. Muralidharan, V.P. Visser, C. Chaffin, W.G. Fateley, L.E. Erickson, and R.M. Hammaker, "Alfalfa Plants and Associated Microorganisms Promote Biodegradation Rather than Volatilization of Organic Substances from Goundwater," In Microbial Degradation of Organic Chemicals in the Rhizosphere: Implications for Bioremediation, T.A. Anderson and J.R. Coats, Editors, ACS Symposium Series, In Press, 1993. 13. Final Program--ACS National Meeting in Chicago, Chemical and Engineering News, 71, No. 29, 51-122, July 19, 1993. 14. Heitholt, J.J., R.H. Hodgson, and T.J. Tworkoski, "Toxicity and Uptake of Nitroguanidine in Plants," Bull. Environ. Contam. and Toxicol., 44, 751-758, 1990. 15. Kingsley, M.T., F.B. Metting, Jr., J.K. Fredrickson, and R.J. Seidler, In Situ Stimulation vs. Bioaugmentation: Can Plant Inoculation Enhance Biodegradation of Organic Compounds, " Paper 93-WA-89.04, Proceedings of the 86th Annual Meeting and Exhibition, Air and Waste Management Association, Pittsburgh, PA, 1993. 16. Lee, E. and M.K. Banks, "Bioremediation of Petroleum Contaminated Soil Using Vegetation: A Microbial Study," Environ. Sci. and Eng. J. of Environ. Sci. and Health, 28, 2187-2198, 1993. 17. Lee, I. and J.S. Fletcher, Metabolism of Polychlorinated Biphenyls (PCBs) by Plant Tissue Cultures," Proceedings of the m International Congress on Plant Tissue and Cell Culture, pp. 656-660, 1990. 18. Licht, L. A . Poplar-Tree Buffer Strips Grown in Riparian Zones for Biomass Production and Non-Point Source Pollution Control, Ph.D. Dissertation, University of Iowa, Iowa City, IA, 1990. 19. Licht, L.A., "Ecolotree Cap - Densely Rooted Trees for Water Management on Landfill Covers, " Paper 93-WA-89.07, Proceedings of the 86th Annual Meeting and Exhibition, Air and Waste Management Association, Pittsburgh, PA, 1993. 20. Mueller, W.F., G.W. Bedell, and P.J. Jackson, "Bioremediation of High Explosive Wastes by Higher Plants," Paper 44c, AIChE Summer National Meeting, Minneapolis, MN, August, 1992. 21. Mueller, W.F., G.W. Bedell, B. Baker, S. Shojaee, and P.J. Jackson, "Bioremediation of TNT Wastes by Higher Plants, " Proceedings of the 3rd Annual Technology Development Conference, T.J. Ward, Editor, New Mexico State University, Las Cruces, NM, pp. 192-201, 1993. 22. Muralidharan, N, L.C. Davis, and L.E. Erickson, "Monitoring the Fate of Toluene and Phenol in the Rhizosphere," Proceedings of the 23rd Annual Biochemical Engineering Symposium, Roger Harrison, Editor, University of Oklahoma, Norrnan, OK, In Press, 1993. 23. Nair, D.R. and J.L. Schnoor, "Effect of Two Electron Acceptors on Atrazine Mineralization Rates in Soil," Environ. Science and Technol. 26, 2298-2300, 1992.. 24. Nair, D.R. and J.L. Schnoor, "Quantifying the Role of Different Soil Parameters on Atrazine Mineralization Kinetics," Water Research (IAWPRC), In Press, 1993. 25. Nair, D.L., J.L. Schnoor, and L.A. Licht, "Mineralization and Uptake of a Triazine Pesticide in Soil-Plant Systems," J. of Environ. Eng., ASCE, 119, 842-854, 1993. 26. Nair, D.R. J.L. Schnoor, L.E. Erickson, L.C. Davis, and J.C. Tracy, "Beneficial Effects of Vegetation on Biodegradation of Organic Compounds," Paper 41e, AIChE Summer Meeting, Minneapolis, MN, August, 1992. 27. Paterson, K.G. and J.L. Schnoor, "Fate of Alachlor and Atrazine in a Riparian Zone Field Site," Res. J. of the Water Pollut. Control Fed., 64, 274-283, 1992. 28. Pierzynski, G.M., J.L. Schnoor, M.K. Banks, J.C. Tracy, L.A. Licht, and L.E. Erickson, "Vegetative Remediation at Superfund Sites," In Mining and Its Environmental Impact, R. E. Hester and R.M. Harrison, Editors, Royal Society of Chemistry, Cambridge, UK, In Press, 1993. 29. Reilley, Kelly, Dissipation of Anthracene and Pyrene in the Rhizosphere, M.S. Thesis, Kansas State University, Manhattan, KS, 1993. 30. Shimp, J.F., J.C. Tracy, L.C. Davis, E. Lee, W. Huang, and L.E. Erickson, "Beneficial Effects of Plants in the Remediation of Soil and Groundwater Contaminated with Organic Materials," Crit. Rev. in Environmental Science and Technology, 23, 41-77, 1993. 31. Short, K.A., R.J. King, and R.J. Seidler, "Biodegradation of Phenoxyacetic Acid in Soil by Pseudomonas putida PP0301 (pR0103), A Constitutive Degrader of 2,4dichlorophenoxyacetate," Mol. Ecol., 1, 89-94, 1992. 32. Stomp, A.M., K.H. Han, S. Wilbert, M.P. Gordon, and S.D. Cunningham, "Genetic trategies for Enhancing Phytoremediation," In Recombinant DNA Technology II, Annals New York Academy of Sciences, Submitted, 1993. 33. Tracy, J.C., L.E. Erickson, and L.C. Davis, "Rate Limited Degradation of Hazardous Organic Compounds in the Root zone of a Soil," Paper 93-WA-89.02, Proceedings of the 86th Annual Meeting and Exhibition, Air and Waste Management Association, Pittsburgh, PA, 1993. 34. Tracy, J.C. L.E. Erickson, J.F. Shimp, and L.C. Davis, "Modeling the Beneficial Effects of Vegetation in the Management of Landfill Leachates," Paper 92-27.03, Proceedings of the 85th Annual Meeting and Exhibition, Air and Waste Management Association, Pittsburgh, PA, 1992. 35. Walton, B.T. and T.A. Anderson, "Plant-Microbe Treatment Systems for Toxic Waste," Current Opinion in Biotechnology 3, 267-270, 1992. 36. Reilley, K., M.K. Banks, and A.P. Schwab, "Dissipation of Polycyclic Aromatic Hydrocarbons in the Rhizosphere," Environ. Sci. Technol., Submitted, 1993. 37. Ferro, A.M., R.C. Sims, and B. Bugbee, "Hycrest Crested Wheatgrass Accelerates the Degradation of Pentachlorophenol in Soil," J. Environ. Qual., In Press, 1993. 38. Anderson, T.A., E.A. Guthrie, and B.T. Walton, "Bioremediation in the Rhizosphere," Environ. Sci. Technol. 27, 2630-2636, 1993. 39. Cunningham, S.D. and W.R Berti, "Remediation of Contaminated Soils with Green Plants: An Overview," In Vitro Cell Dev. Biol-Plant, 29P, 207-212, 1993. TABLE 1. Dimensionless Concentration of Toluene in the Saturated Zone at Five Axial Positions on Four Different Days. Average flow rate Dimensionless Concentration C* (liters/day) C* = concentration C/inlet concentration Inflow Outflow Port 1 Port 2 Port 3 Port 4 Port 5# 1.0 0.4 0.89 0.97 0.99 0.81 1.06 1.0 0.4 0.80 0.76 0.83 0.91 0.87 1.5 0.8 0.82 0.87 0.75 0.69 0.96 1.5 0.85 0.83 0.92 0.90 0.81 0.97 *Inlet flow was water saturated with toluene. The input concentration was about 515 mg/liter. From Muralidharan et al. (22). # Port 5 was connected to the outflow container. TABLE 2. Dimensionless Concentration of Phenol at Five Axial Positions on Four Different Days.* Average flow rate Dimensionless Concentration C* (liters/day) C* = concentration C/inlet concentration Inflow Outflow Port 1 Port 2 Port 3 Port 4 Port 5# 1.0 0.1 0.89 0.91 0.66 0.98 0.02 0.6 0.0 0.77 0.76 0.24 --- --- 0.6 0.0 0.85 0.79 0.25 --- --- 1.4 0.0 0.96 0.89 0.82 0.77 0.02+ 1.2 0.3 0.99 0.89 0.84 0.77 0.03 * Inlet flow was water with 0.5 ml/L of 93 % phenol. From Muralidharan et al. (22). + No measurable effluent flow. # Port 5 was connected to the outflow container. --- No sample was collected. All values for inflow = 0.6 liters/day were from the same day. TABLE 3. Fractions of Input Water and Toluene which do not Leave in the Effluent. | Average flow rate | C* Fraction of Fraction of (liters/day) toluene lost water lost Inflow Outflow Port 5 1.0 0.40 1.06 0.58 0.6 1.0 0.40 0.87 0.65 0.6 1.5 0.80 0.96 0.49 0.47 1.5 0.85 0.97 0.45 0.43 From Muralidharan et al. (22). TABLE 4. Fractions of Input Water and Phenol which do not Leave in the Effluent. Average flow rate C* Fraction of Fraction of (liters/day) phenol lost water lost Inflow Outflow Port 5 1.0 0.1 0.02 0.99 0.90 0.6 0.0 --- 1.00 1.00 0.6 0.0 --- 1.00 1.00 1.4 0.0 0.02 1.00 1.00 1.2 0.3 0.03 0.99 0.75 From Muralidharan et al. (22). Table 5. Concentration of Anthracene (mg/kg) in Contaminated Spiked Soil for 100 mg/kg of Added Anthracene.* Vegetation Time 4 weeks 24 weeks No Plants 1.704 (0.205) 1.145 (0.100) Alfalfa 0.883 (0.190) 0.587 (0.322) Fescue 1.371 (0.453) 0.753 (0.152) Switch Grass 1.040 (0.281) 0.788 (0.237) Sudan Grass 1.649 (0.155) 0.737 (0.145) * Values in parentheses are standard deviations from four replicates. The measured concentration of anthracene in the contaminated soil before spiking was 0.6 mg/kg. From Reilley (29). Table 6. Concentration of Pyrene (mg/kg) in Contaminated Spiked Soil for 100 mg/kg of Added Pyrene.* Vegetation Time 4 weeks 24 weeks No Plants 12.646 (0.237) 2.363 (0.245) Alfalfa 9.887 (0.164) 1.655 (0.187) Fescue 10.152 (0.436) 1.490 (0.597) Switch Grass 10.828 (0.464) 1.325 (0.318) Sudan Grass 10.685 (0.261) 1.484 (0.564) * Values in parentheses are standard deviations from four replicates. The measures concentration of pyrene in the contaminated soil before spiking was 1.4 mg/kg. From Reilley (29). Table 7. Comparison of Cumulative Amount of l4CO2 Evolved from Transformation of Pyrene for Organic Acid Enriched Rhizosphere Soil (RA), Rhizosphere Soil (RW), NonRhizosphere Soil (NW), and Autoclaved Soil (C)*. Time (days) RA (dpm) RW (dpm) NW (dpm) C (dpm) 5 5,803 5,143 5,081 336 10 9,908 8,197 7,976 1,051 30 14,194 10,844 10,932 2,403 50 16,875 12,209 12,673 3,271 From Reilley (29).