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Este trabajo constituye el Capítulo 20 del libro.-- El DOI del volumen 707 es: 10.1021/bk-1998-0707.NMR spectroscopy has been proven to be a valuable tool for the nondestructive examination of refractory geopolymers. Due to the low sensitivity of the 15N isotope for an NMR experiment, 15N NMR spectroscopy has been restricted to the examination of laboratory-derived 15N enriched material. Recent developments have made it possible to obtain solid-state 15N NMR spectra of natural soils at natural 15N abundance. The results of recent 15N NMR studies obtained from various soil and soil related systems are summarized. These studies indicate that amide functional groups represent the major nitrogen form in many soil systems. The formation of heterocyclic aromatic nitrogen, commonly proposed to be an important mechanism of nitrogen stabilization during humification, was not confirmed by 15N NMR spectroscopic investigation of natural soils.Peer reviewe

Soil Organic Nitrogen Formation Examined by Means of NMR Spectroscopy