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Pyrolysis–Gas Chromatography/Mass Spectrometry Identification of Distinctive Structures Providing Humic Character to Organic Materials
Author(s) -
Fuentes Marta,
Baigorri Roberto,
GonzálezVila Francisco J.,
GonzálezGaitano Gustavo,
GarcíaMina José M.
Publication year - 2010
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2009.0180
Subject(s) - chemistry , alkylbenzenes , pyrolysis , pyrolysis–gas chromatography–mass spectrometry , magic angle spinning , mass spectrometry , humus , lignin , gas chromatography , fractionation , organic matter , environmental chemistry , chromatography , organic chemistry , nuclear magnetic resonance spectroscopy , soil water , environmental science , soil science , benzene
Flash pyrolysis–gas chromatography/mass spectrometry (Py‐GC/MS) was used to study the structural transformations of humic fractions formed as a result of composting processes of diverse organic materials (solid wastes of wineries, solid olive‐mill wastes, domestic wastes, ovine manures plus straw, and mixtures of animal manures). Sodium hydroxide–extracted total humic‐like extracts (THE; humic plus fulvic acids) from the composted and the initial noncomposted wastes and several reference humic and fulvic acids from soils were analyzed. These results were compared with results from previous studies using 13 C‐cross polarization magic angle spinning–nuclear magnetic resonance (NMR), UV‐visible, and fluorescence emission spectroscopies. Alkylbenzenes and alkylphenols predominate in the pyrograms of the soil humic acids, whereas the fulvic acids showed higher contents of phenolic and polysaccharide‐derived compounds. The pyrolysates of THE from the composted samples showed an increase in aromatic and nitrogenated structures and a decrease in polysaccharide‐derived compounds. The aromatic contents as determined by Py‐GC/MS and 13 C‐NMR were well correlated in the reference humic substances and THE from composted materials ( r = 0.99 and 0.94, respectively; P < 0.01) but not in the case of THE from noncomposted materials, probably due to an aliphatic enhancement in the pyrolysates of these samples and other secondary reactions. The content in alkylbenzenes was consistent with the variations found previously for several UV‐visible and fluorescence indexes as a function of the degree of humification, suggesting their involvement in structures that are a characteristic feature of the formation and evolution of humic substances.