Enhanced Humification as an In-Situ Bioremediation Technique for 2,4,6-Trinitrotoluene (TNT) Contaminated Soils

The microbial remediation of 2,4,6-trinitrotoluene (TNT) contaminated soils is difficult because it is not possible to achieve mineralization of this substance. TNT can only be transformed via the sequence TNT → 4-aminodinitrotoluene (4-ADNT) → 2,4-diaminonitrotoluene (2,4-DANT) → 2,4,6-triaminotoluene (TAT). TAT is formed when redox potentials are below - 250 mV, otherwise 2,4-DANT is accumulated. If under in-situ conditions TNT or its metabolites are irreversibly incorporated into the humic matrix (humification) instead of being sorbed, the humification might be used as a remediation technology. Equilibrium dialysis showed that TNT, 4-ADNT and 2,4-DANT did not adsorb on humic substances. However, in TNT-degradation studies under nitrogen limitation, the more humic substances were added the less metabolites were recovered proposing an efficient microorganism-mediated incorporation (humification), probably based on stress-induced radical enzyme reactions. This assumption was supported by the observation t...