Evaluation of stacking nanostructure in soil humic acids by analysis of the 002 band of their X-ray diffraction profiles

Naoya Katsumi, Koyo Yonebayashi, Masanori Okazaki

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Humic substances are ubiquitous in the environment. The development of models for their chemical structure can be expected to improve our understanding of their environmental behavior. In this study, we used X-ray diffraction (XRD) to develop models for the stacking nanostructure of 12 humic acids (HAs) extracted from Japanese Andisols, Inceptisols and Entisols. In the XRD profiles of the HAs, the γ band, which was attributed to aliphatic side chains, and the 002 band were separated by means of curve fitting with the Voigt function. The interlayer spacing of the carbon (C) planes (d002) and the mean thickness of the stacking nanostructure along the c axis (Lc) were calculated from the position of the peak for the 002 band and the full width at half maximum by means of Bragg’s and Scherrer’s equations, respectively. The average number of C planes in the stacking nanostructure (Nc) was estimated from d002 and Lc. The Lc and Nc values ranged from 1.04 to 1.84 nm and from 3.01 to 5.40, respectively. The mean Lc and Nc values of the Andisol HAs were larger than those of the Inceptisol and Entisol HAs (P 002 value of the HAs was approximately 0.34 nm, which was slightly larger than that of graphite (0.335 nm). The Lc value positively correlated with aromatic C content (r = 0.938, P 13C) nuclear magnetic resonance spectra. Furthermore, the degree of darkness of the HAs positively correlated with Lc (r = 0.961, P 

Original languageEnglish
Pages (from-to)603-612
Number of pages10
JournalSoil Science and Plant Nutrition
Volume61
Issue number4
DOIs
Publication statusPublished - 2015 Jul 4
Externally publishedYes

Keywords

  • <sup>13</sup>C NMR spectroscopy
  • 002 band
  • humic acid
  • stacking nanostructure
  • X-ray diffraction

ASJC Scopus subject areas

  • Soil Science
  • Plant Science

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