15M NMR investigation of the reduction and binding of TNT in an aerobic bench scale reactor simulating windrow composting

(TNT)-N-15 was added to a soil of low organic carbon content and composted for 20 days in an aerobic bench scale reactor The finished whole compost and fulvic acid humic acid humin and lignocellulose fractions extracted from the compost were analyzed by solid state CP/MAS and DP/MAS N-15 NMR N-15 NMR spectra provided direct spectroscopic evidence for reduction of TNT followed by covalent binding of the reduced metabolites to organic matter of the composted soil with the majority of metabolite found in the lignocellulose fraction by mass also the major fraction of the compost In general the types of bonds formed between soil organic matter and reduced TNT amines in controlled laboratory reactions were observed in the spectra of the whole compost and fractions confirming that during composting TNT is reduced to amines that form covalent bonds with organic matter through aminohydro quinone aminoquinone heterocyclic and imine linkages among others Concentrations of imine nitrogens in the compost spectra suggest that covalent binding by the diammes 24DANT and 26DANT is a significant process in the transformation of TNT into bound residues Liquid phase N-15 NMR spectra of the fulvic acid and humin fractions provided possible evidence for involvement of phenoloxidase enzymes in covalent bond formation.