Urea-Catalyzed Extractability of 2,4,6-Trinitrotoluene from Contaminated Soils: Preliminary Results

Padmini Das, Konstantinos C. Makris, Rupali Datta, Dibyendu Sarkar, and Pravin A. Punamiya
Environmental Geochemistry Laboratory, University of Texas at San Antonio, San Antonio, TX

Our ultimate goal is to provide a cost effective, and environment-friendly remediation technology for 2,4,6-trinitrotoluene (TNT)-contaminated sites using a chemically-catalyzed phytoremediation system. Nitroaromatic compounds, such as TNT are characterized by relatively small aqueous solubilities that could limit plant uptake. Earlier hydroponic studies in our lab showed the effectiveness of urea used as a chaotropic agent to chemically catalyze plant TNT uptake. Urea is common agrochemical that belongs in the class of chaotropic agents, which are specific anions (thiocyanate or polar carbamide derivatives), modifying the water structure around aggregated proteins or sugars. The effectiveness of urea in increasing TNT extractability and uptake in plant-hydroponic systems has been already documented, but little is known about its performance in the highly-complex soil solution of TNT-contaminated soils. The objectives of this batch experiment (in the absence of plants) were to: i) evaluate the effectiveness of urea in increasing aqueous TNT concentrations and thus, extractability from an acidic (soil pH 5.8) and a basic (soil pH 8.1) contaminated soil; and ii) determine the effects of pH and reaction time on the effectiveness of urea in catalyzing TNT extractability from two contaminated soils. Results are expected to shed light on the conditions under which urea mobilizes soil-TNT by increasing its solubility at the solid/liquid interface. Implications related to designing an effective urea-based phytoremediation system in the greenhouse/field scale are also discussed.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas