Characterization of N-15-TNT residues after an anaerobic/aerobic treatmentof soil/molasses mixtures by solid state N-15 NMR spectroscopy. 1. Determination and optimization of relevant NMR spectroscopic parameters
H. Knicker et al., Characterization of N-15-TNT residues after an anaerobic/aerobic treatmentof soil/molasses mixtures by solid state N-15 NMR spectroscopy. 1. Determination and optimization of relevant NMR spectroscopic parameters, ENV SCI TEC, 33(2), 1999, pp. 343-349
Citations number
24
Categorie Soggetti
Environment/Ecology,"Environmental Engineering & Energy
Solid-state N-15 NMR was applied to a humic acid, extracted from N-15-2,4,6
-trinitrotoluene (TNT) enriched soil treated in an anaerobic/aerobic compos
ting system to characterize the nitrogen functionality of the transformatio
n products bound to the soil organic material. Signals assignable to anilin
e derivatives and condensation products were identified, indicating that th
e anaerobic/aerobic treatment caused a reduction of nitro groups followed b
y condensation reactions with the soil organic material. Relevant parameter
s for routine application of the cross polarization magic angle spinning te
chnique were determined and optimized. The proton spin-lattice relaxation t
imes of all peaks in the N-15 NMR spectrum of the humic acid did not exceed
30 ms. Due to the fast relaxation, the application of N-15 NMR spectroscop
y to soils with lower enrichment of N-15-TNT is feasible. The influence of
spinning sidebands on the intensity distribution was shown to be minimal at
spinning speeds between 5.5 and 6.5 kHz. Contact times between 0.7 and 1 m
s resulted in spectra with representative intensity distribution of all vis
ible N-15-TNT transformation products. However an underestimation of unreac
ted TNT must be considered. The results imply that CPMAS N-15 NMR is a valu
able tool for the examination of bound residues of TNT in soils. (Figure 1)
.