Pedosphere 11(2): 151--157, 2001
ISSN 1002-0160/CN 32-1315/P
©2001 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Characterization of humic fractions in a 15N-labelled soil by solid-state 13C and 15N NMR |
| CHENG Li-Li, WEN Qi-Xiao and CHEN Bi-Yun |
| Institute of Soil Science, the Chinese Academy of Sciences, Nanjing 210008 (China) |
| ABSTRACT |
| Five humic fractions were obtained from a uniformly 15N-labelled soil by extraction with 0.1 mol L-1 Na4P2O7, 0.1 mol L-1 NaOH, and HF/HCl-0.1 mol L-1 NaOH, consecutively, and analyzed by 13C and 15N CPMAS NMR (cross polarization and magic angle spinning nuclear magnetic resonance). Compared with those of native soils humic fractions studied as a whole contained more alkyls, methoxyls and O-alkyls, being 27%~36%, 17%~21% and 36%~40%, respectively, but fewer aromatics and carboxyls (being 14%~20% and 13%~90%, respectively). Among those humic fractions, the humic acid (HA) and fulvic acid (FA) extracted by 0.1 mol L-1 Na4P2O7 contained slightly more carboxyls than corresponding humic fractions extracted by 0.1 mol L-1 NaOH, and the HA extracted by 0.1 mol L-1 NaOH after treatment with HF/HCl contained the least aromatics and carboxyls. The distribution of nitrogen functional groups of soil humic fractions studied was quite similar to each other and also quite similar to that of humic fraction from native soils. More than 75% of total N in each fraction was in amide form, with 9%~13% present as aromatic and/or aliphatic amines and the remainder as heterocyclic N. |
| Key Words: aromaticity, 13C CPMAS NMR, humic substances, 15N CPMAS NMR nitrogen forms |
| Citation: Cheng, L. L., Wen, Q. X. and Chen, B. Y. 2001. Characterization of humic fractions in a 15N-labelled soil by solid-state 13C and 15N NMR. Pedosphere. 11(2): 151-157. |
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