INCORPORATION OF C-14-LABELED 2,4,6-TRINITROTOLUENE METABOLITES INTO DIFFERENT SOIL FRACTIONS AFTER ANAEROBIC AND ANAEROBIC-AEROBIC TREATMENT OF SOIL MOLASSES MIXTURES/

Experiments were conducted to evaluate the level of incorporation of C -14-labeled 2,4,6-trinitrotoluene (TNT) and metabolites into the organ ic soil matrix of anaerobic and sequential anaerobic-aerobic treated s oil/molasses mixtures. After 9 weeks of anaerobic-aerobic incubation w ith an optimized experimental setup, we determined nearly 84% of the i nitially applied radioactivity immobilized in different soil fractions , whereas only 57% of the radioactivity was measured as immobilized in the soil organic matrix at the end of the anaerobic treatment (after 5 weeks). After alkaline hydrolyses of the solvent-extracted soil/mola sses mixtures, small amounts of radioactivity were found in the humic acid and fulvic acid fraction, whereas the major part of radiolabel wa s found to be strongly bound to the humin fraction. In agreement with these findings, the amount of extractable radioactivity (water, methan ol, and ethyl acetate extractions) decreased from 40% after the anaero bic phase to nearly 9% after the aerobic treatment phase. The transfor mation of TNT at the end of the experiments was above 95% and 97% afte r anaerobic and sequential anaerobic-aerobic treatment, respectively. We propose a two-step treatment process (anaerobic-aerobic bioremediat ion process) with some special procedures during the anaerobic and the aerobic treatment phases as the most promising method for effective, economic, and ecologically acceptable disposal of TNT from contaminate d soils by means of immobilization (for example, humification) of this xenobiotic.