Mineralization of 2,4- and 2,6-dinitrotoluene in soil slurries

DNT-degrading bacteria can completely degrade mixtures of DNT in liquid cul tures without the production of aminonitrotoluenes. We determined whether s pecific DNT-degrading isolates could also degrade DNT from contaminated soi l in the presence of indigenous microbial communities. When 2,4-DNT- and 2, 6-DNT-degrading strains were added to a mixture of 2,4-DNT and 2,6-DNT in a soil slurry, disappearance of DNT was accompanied by (CO2)-C-14 release an d stoichiometric appearance of nitrite. When soil historically contaminated with mixed DNT isomers was used in slurries, the combination of DNT-degrad ing strains removed all of the DNT from the aqueous phase and over 99% of t he initial DNT. Traces of extractable DNT remained associated with the soil ; however, the toxicity of the treated soil was low. After an extended accl imation period, the 2,4-DNT, and, much later, the 2,6-DNT, was degraded in the uninoculated control. The results show that aged DNT contamination can be removed effectively from soil. The addition of specific DNT-mineralizing bacteria dramatically enhances the mineralization of DNT in soil slurries. Native bacteria do not convert DNT to aminonitrotoluenes during the short incubation times required for mineralization of DNT.