Submitted to: Environmental Bioremediation and Biodegradation Symposium
Publication Type: Proceedings
Publication Acceptance Date: 7/1/2001
Publication Date: 9/1/2001
Citation: Interpretive Summary: Phytoremediation is a new technology which uses plants to achieve environmental remediation goals. Because soils at military manufacturing and testing sites have often become contaminated with TNT, we tested the ability of forage and conservation crop species to hasten biodegradation of soil TNT. Two soils were amended with TNT at 100 mg/kg soil and equilibrated, then planted with grasses and legumes, or left unplanted. The crops were grown for 6 months, and then the soils samples were analyzed for remaining TNT. Plant species differed significantly in ability to aid the biodegradation of TNT, and planting caused more transformation than leaving the soil unplanted. Reed canary grass and switchgrass were the most effective in increasing TNT transformation among the species tested. Alfalfa and flatpea also performed well, but not as well as these two grasses. Transformation was much greater in the soil with lower organic matter, perhaps because soil adsorption of TNT by the organic matter could delay biodegradation. Thus the biodegradation of soil TNT was affected by the soil properties, by crop species, and also differ among locations so bench scale laboratory tests could be used to identify the best combinations for the specific contaminant and soil requiring remediation.
Technical Abstract: The objective of this study was evaluation of different forage and conservation crops for phytoremediation of trinitrotoluene (TNT) contaminated soils. Trinitrotoluene contamination levels were 100 mg/kg of soil. A crop species screening study was conducted in the greenhouse and growth chambers on two soil types with different organic matter contents. Under high soil organic matter conditions, adsorption or covalent binding to the soil organic matter appeared to be a dominant force of removal limiting TNT availability. However, in soils with lower organic matter content, all of the plant species treatments showed a significantly higher degree of TNT transformation compared to the unplanted control. Statistically significant differences in TNT transformation were also observed among the crop species in the study. Reed canarygrass (Phalaris arundinacea L.) and switchgrass (Panicum virgatum L.) were the most effective species in enhancing TNT transformation. Our data indicated that use of plants was effective for phytoremediation of TNT contaminated soils. Based on these observations, it could be concluded that plant-soil-contaminant interactions are very specific and this specificity determines the effectiveness of a phytoremediation scheme.