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2,4,6-TRINITROTOLUENE TRANSFORMATION IN PLANTED, SOIL COLUMNS
Citation:
Sealock, G. A. AND N L. Wolfe. 2,4,6-TRINITROTOLUENE TRANSFORMATION IN PLANTED, SOIL COLUMNS. Presented at 22nd Annual Society of Environmental Toxicology and Chemistry Meeting, Baltimore, MD, November 11-15, 2001.
Impact/Purpose:
Elucidate and model the underlying processes (physical, chemical, enzymatic, biological, and geochemical) that describe the species-specific transformation and transport of organic contaminants and nutrients in environmental and biological systems. Develop and integrate chemical behavior parameterization models (e.g., SPARC), chemical-process models, and ecosystem-characterization models into reactive-transport models.
Description:
2,4,6-Trinitrotoluene (TNT), has been used extensively by the United States military to manufacture explosive devices. Since the conclusion of World War 11, many of these military installations have also been involved in the disposal of surplus and outdated explosives. Both the commissioning and disposal of weapons at ammunition plants have led to soil, ground, and surface water contamination by munitions. It is estimated that munition contamination is found at approximately 50 military bases and explosives manufacturing facilities in the United States. In this study, the feasibility of using phytoremediation, the use of plants and the microbes associated with their rhizospheres to degrade contaminants, was examined. Two primary studies, a batch- scale kinetic study, and a vegetated, column study were conducted to determine the potential of various terrestrial plant species to transform TNT. For the kinetic study, plant tissue samples were submerged in a TNT solution and samples were extracted on a schedule of increasing time intervals for up to 30 hours. Sampling of the solutions occurred until non-detect levels were reached. All samples were characterized using liquid chromatography. Half- lives and degradation constants were calculated for first-order reactions with each plant species. In order to study TNT degradation in a plant-soil system, soil columns were constructed. A TNT sorption study was performed using,the column soil. The data was fit using the Freundlich equation. A continuous input of 10 mg/L TNT was applied to the columns for two months. When application of TNT was concluded soil and plant tissue samples were obtained for TNT extractions. Soil samples were obtained at three depths. Plant samples consisted of leaf, stem, root, and tuber tissue. Soil extractions were conducted following EPA Method 8330. All species readily absorbed TNT from the soil. Some TNT transformation occurred in the soil as well as in the plant tissues. This was determined by the presence of TNT metabolites. No TNT or metabolites were found in leachates exiting the columns. The results of the study suggest that irrigation of TNT contaminated water is a viable option for remediation.