Effects of heating on composition, degree of darkness, and stacking nanostructure of soil humic acids

Naoya Katsumi*, Koyo Yonebayashi, Masanori Okazaki

*この研究の対応する著者

研究成果: Article査読

13 被引用数 (Scopus)

抄録

Wildfires and prescribed burning can affect both the quality and the quantity of organic matter in soils. In this study, we investigated qualitative and quantitative changes of soil humic substances in two different soils (an Entisol from a paddy field and an Inceptisol from a cedar forest) under several controlled heating conditions. Soil samples were heated in a muffle furnace at 200, 250, or 300°C for 1, 3, 5, or 12h. The humic acid and fulvic acid contents of the soil samples prior to and after heating were determined. The degree of darkness, elemental composition, carbon and nitrogen stable isotope ratios, 13C nuclear magnetic resonance spectra, and X-ray diffraction patterns of humic acids extracted from the soils before and after heating were measured. The proportion of humic acids in total carbon decreased with increasing heating time at high temperature (300°C), but increased with increasing heating time at ≤250°C. The degree of darkness of the humic acids increased with increasing heating time and temperature. During darkening, the H/C atomic ratios, the proportion of aromatic C, and the carbon and nitrogen stable isotope ratios increased, whereas the proportions of alkyl C and O-alkyl C decreased. X-ray diffraction analysis verified that a stacking nanostructure developed by heating. Changes in the chemical structure of the humic acids from the heated soils depended on the type of soil. The major structural components of the humic acids from the heated Entisol were aromatic C and carboxylic C, whereas aliphatic C, aromatic C, and carboxylic C structural components were found in the humic acids from the heated Inceptisol. These results suggest that the heat-induced changes in the chemical structure of the humic acids depended on the source plant.

本文言語English
ページ(範囲)23-32
ページ数10
ジャーナルScience of the Total Environment
541
DOI
出版ステータスPublished - 2016 1 15
外部発表はい

ASJC Scopus subject areas

  • 環境化学
  • 汚染
  • 廃棄物管理と処理
  • 環境工学

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