CHEMICALLY-CATALYZED UPTAKE OF 2,4,6-TRINITROTOLUENE BY VETIVER GRASS VETIVERIA ZIZANIOIDES IN SOIL

2, 4, 6-trinitrotoluene (TNT) is a group C human carcinogen and a potential mutatoxin. The manufacturing, use and disposal of munitions in various military sites has resulted in widespread TNT contamination of terrestrial and aquatic ecosystem in the U.S. Currently several of these military sites are in the process of being transferred to non-military entities under the Base Realignment and Closure (BRAC) program, and would require major remediation efforts. Earlier studies in our laboratory have shown the effectiveness of Vetiver grass (Vetiveria zizanioides) in removing TNT under hydroponic conditions. In this study the ability of vetiver grass to uptake of TNT from soil was studied in the presence of a common agrochemical, urea. Since TNT has relatively low aqueous solubility (390 mg L-1 @ 24.5oC), urea was used as a chaotropic agent to facilitate TNT uptake by vetiver. Chaotropic agents are specific anions (e.g., SCN-) or polar carbamide derivatives (e.g. urea), which modify water structure around aggregated proteins or sugars by increasing the solubility of their hydrophobic regions in aqueous environments. The objectives of this study were to i) characterize the adsorption of TNT in soil, ii) determine the efficiency of Vetiver grass to remove TNT from soil and iii) evaluate the effect of urea in TNT removal by Vetiver grass. A soil aging study of TNT over a period of 48 days showed no significant (p = 0.475) change in the initial TNT load. Plants were allowed to grow in TNT contaminated soil for twelve days in a greenhouse setting. Immokalee, a sandy, acidic soil was contaminated with two concentrations of TNT (40 and 80 mg kg-1 of soil) along with 1000 mg kg-1 of urea. Soil samples were collected at three different time intervals (0h, 72 h and 288 h) to investigate the kinetics of removal of TNT by Vetiver grass from soil. The result shows that vetiver exhibited a high capacity to remove TNT from soil. Removal of TNT was further enhanced in the presence of urea.