HP4 Biotransformation of Organics and Their Biological Effects
Room 16A/B, Level 4
2:10 PM - 5:30 PM, Thursday, 13 November 2003
Chair: Venables, Barney ,
(593) Sorption and Biodegradation of Sorbed Dinitrotoluene in Model Soil Systems: Implications to Remediation.
Law, Melissa1, Zheng, Gang2, Zhang, Chunlong2, 1 Baker Petrolite Corporation, Houston, Texas, USA2 University of Houston-Clear Lake, Houston, Texas, USA
ABSTRACT- 2,4-Dinitroluene (DNT) and its isomer 2,6-DNT, are intermediates used in the production of 2,4,6-trinitrotoluene (TNT), and as precursors for the production of toluene diisocyanate used to generate polyurethane foams. The improper handling of these DNT isomers has resulted in the extensive contamination of soil and groundwater near military sites, munitions and polyurethane foam facilities. The purposes of this study were to test the sorption behavior of DNT in various sorbents and the biodegradation of sorbed phase 2,4-DNT. Batch adsorption studies were performed using two uncontaminated soils (Prairie View and College Station, TX), two clays (kaolinite and montmorillonite), and an activated carbon as a sorbent. Desorption studies were performed using contaminated soil collected from two former army ammunition plants (Baraboo, WI; Chattanooga, TN). Adsorption for both DNT isomers in model test soils and clays was found to fit the linear isotherm model whereas in activated carbon the best model was the Langmuir. Although both isomers show low Kd values for all soils and clays tested, 2,4-DNT has a consistently stronger adsorption than its isomer. Desorption of 2,4-DNT was generally rapid and complete. Results also indicated that adsorption due to kaolinite clay had no effect on both the rate and extent of 2,4-DNT biodegradation. In contrast, montmorillonite clay and activated carbon significantly reduced or completely impeded the biodegradation of 2,4-DNT. This study implies that specific adsorption to clays is less likely to be a limiting factor for in sitnu DNT bioremediation where nonspecific hydrophobic adsorption to natural organic matter is low. The low Kd values and rapid desorption kinetics, however, imply a potential problem of DNT leaching from contaminated vadose zone soil into underlying groundwater.
Key words: Bioremediation, Biodegradation, Explosives, Dinitrotoluene