Incorporation of ¹⁴C-Labeled 2,4,6-Trinitrotoluene Metabolites into Different Soil Fractions after Anaerobic and Anaerobic−Aerobic Treatment of Soil/Molasses Mixtures

Abstract

Experiments were conducted to evaluate the level of incorporation of 14 C-labeled 2,4,6-trinitrotoluene (TNT) and metabolites into the organic soil matrix of anaerobic and sequential anaerobic-aerobic treated soil/molasses mixtures. After 9 weeks of anaerobic-aerobic incubation with an optimized experimental setup, we determined nearly 84% of the initially 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 solventextracted soil/molasses mixtures, small amounts of radioactivity were found in the humic acid and fulvic acid fraction, whereas the major part of radiolabel was found to be strongly bound to the humin fraction. In agreement with these findings, the amount of extractable radioactivity (water, methanol, and ethyl acetate extractions) decreased from 40% after the anaerobic phase to nearly 9% after the aerobic treatment phase. The transformation of TNT at the end of the experiments was above 95% and 97% after anaerobic and sequential anaerobic-aerobic treatment, respectively. We propose a two-step treatment process (anaerobic-aerobic bioremediation 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 contaminated soils by means of immobilization (for example, humification) of this xenobiotic.

Immobilization of Energetics on Live Fire Ranges (CU-1229). Revision 1.0

“…Stimulation of explosives biodegradation in different environments with molasses has been reported previously by several investigators [14,15,[30][31][32][33][34], so its effectiveness in these studies was not surprising. Potato starch and corn starch also have been observed to stimulate significant RDX biodegradation in anaerobic soil-water slurries under anaerobic conditions [35].…”

“…Based on extensive research that has been done on the biodegradation and biotransformation of explosive compounds by bacteria (for review see refs (14, 18, 21)), fungi (5, 6, 12,32,36,40,46) and plants (8, 16,22,30,45), other approaches for remediating explosive compounds-contaminated soils have been developed.…”

Biological Degradation of 2,4,6-Trinitrotoluene

“…In cell suspension assays with clostridia, reduction of the nitro group could result in the production of TAT and other products, some of which remain unidentified. The question whether the pathways for TNT metabolism are inducible or associated with constitutively expressed metabolic functions in different Clostridium strains remains to be solved (61,64). Below we describe some in vivo and in vitro reactions of TNT by Clostridium spp.…”

“…Research thus far indicates that TNT can be removed from contaminated soils (35,42,61,62,124,167,253). In composting, the soil must be mixed with a bulk agent and additional organic substrates which are usually by-products of agricultural processes (straw, alfalfa, wood chips, sugarbeet stems, and leaves).…”

Microbial Transformations at Aqueous-Solid Phase Interfaces: A Bioremediation Approach

“…2,4,6-Trinitrotoluene (TNT) was the most widely produced and used explosive in both World Wars [215]. The remediation of soils and groundwater contaminated with TNT is of particular concern, since this compound and its reduced metabolites (i.e., aminodinitrotoluenes and diaminonitrotoluenes) are toxic to a variety of biota and show a broad spectrum of toxicological behavior ranging from mutagenic to carcinogenic activity [256,[411][412][413].…”