Environmental Fate of 14C Radiolabeled 2,4-Dinitroanisole in Soil Microcosms

2,4-Dinitrosanisole (DNAN) is an insensitive munitions component replacing conventional explosives. While DNAN is known to biotransform in soils to aromatic amines and azo-dimers, it is seldom mineralized by indigenous soil bacteria. Incorporation of DNAN biotransformation products into soil as humus-bound material could serve as a plausible remediation strategy. The present work studied biotransformation of DNAN in soil and sludge microcosms supplemented with uniformly ring-labeled 14C-DNAN to quantify the distribution of label in soil, aqueous, and gaseous phases. Electron donor amendments, different redox conditions (anaerobic, aerobic, sequential anaerobic–aerobic), and the extracellular oxidoreductase enzyme horseradish peroxidase (HRP) were evaluated to maximize incorporation of DNAN biotransformation products into the nonextractable soil humus fraction, humin. Irreversible humin incorporation of 14C-DNAN occurred at higher rates in anaerobic conditions, with a moderate increase when pyruvate was added. Additionally, a single dose of HRP resulted in an instantaneous increased incorporation of 14C-DNAN into the humin fraction. 14C-DNAN incorporation to the humin fraction was strongly correlated (R2 = 0.93) by the soil organic carbon (OC) amount present (either intrinsic or amended). Globally, our results suggest that DNAN biotransformation products can be irreversibly bound to humin in soils as a remediation strategy, which can be enhanced by adding soil OC.