Characterization of 15N-TNT residues after an anaerobic/aerobic treatment of soil/molasses mixtures by solid-state 15N NMR spectroscopy. 2. Systematic investigation of whole soil and different humic fractions

8 pages, 6 figures, 2 tables, 42 references.An anaerobic/aerobic composting experiment with 15N-2,4,6-trinitrotoluene (TNT) spiked soil was performed to investigate the fate of the explosive under the applied conditions. For a qualitative description of TNT-residues formed during the composting process, bulk soil and different soil fractions were subjected to solid-state 15N NMR spectroscopy. Major resonance signals could be detected in the chemical shift regions of five-ring heterocyclic nitrogen and in the area of aniline derivatives and primary amines. Distinct nitro peaks were found in the bulk samples and in the humic fractions obtained with a mild extraction procedure. This signal disappeared in the material extracted with a more drastic procedure. Quantitative investigations of the 15N distribution in the composted material revealed that 33% of the stable nitrogen isotope was incorporated into the humic- and fulvic acid, and 23% was present in the humin. Furthermore 38.8% of the 15N present in the composted material could be allotted to condensed TNT residues, whereas 1.9% are assigned to nitro functions and 15.2% to amino functions. In the investigation presented here a bioremediation method was simulated with 15N-TNT spiked soil. The nonradioactive label allowed a qualitative and quantitative characterization of residues of the explosive. Our results give strong evidence for a stable incorporation of the nitroaromatics into the humic material of soils. However, further investigations will be necessary to prove a long-time stability of bound TNT residues and to assess toxicological effects of the treated soil.This work was supported by the Federal Ministry of Education, Science, Research and Technology (BMBF), by the state Lower Saxony and the Industrieverwaltungsgesellschaft AG (IVG), Bonn, Germany.Peer reviewe