Pedosphere 11(1): 1--9, 2001
ISSN 1002-0160/CN 32-1315/P
©2001 Soil Science Society of China
Published by Elsevier B.V. and Science Press
15N NMR spectroscopic study on nitrogen forms in humic substances of soils
WEN Qi-Xiao, ZHUO Su-Neng and CHENG Li-Li
Institute of Soil Science, the Chinese Academy of Sciences, P.O. Box 821, Nanjing 210008 (China)
ABSTRACT
      Nitrogen forms of humic substances from a subalpine meadow soil, a lateritic red soil and a weathered coal and the effect of acid hydrolysis on N structures of soil humic substances were studied by using 15N cross-polarization magic angle spinning nuclear magnetic resonance (CPMAS NMR) spectroscopy. Of the detectable 15N-signal intensity in the spectra of soil humic substances 71%~79% may be attributed to amide groups, 10%~18% to aromatic/aliphatic amines and 6%~11% to indole- and pyrrole-like N. Whereas in the spectrum of the fulvic acid from weathered coal 46%, at least, of the total 15N-signal intensity might be assigned to pyrrole-like N, 14% to aromatic/aliphatic amines, and the remaining intensities could not be assigned with certainty. Data on nonhydrolyzable residue of protein-sugar mixture and a 15N-labelled soil fulvic acid confirm the formation of nonhydrolyzable heterocyclic N during acid hydrolysis.
Key Words:  forms of N, humic substances, mineral soils, 15N CPMAS NMR, weathered coal
Citation: Wen, Q. X., Zhuo, S. N. and Cheng, L. L. 2001. 15N NMR spectroscopic study on nitrogen forms in humic substances of soils. Pedosphere. 11(1): 1-9.
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