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Organic Matter Extraction from Soils with Water at High Pressure and Temperatures
Author(s) -
Schnitzer M.,
Schuppli P.,
Schulten H.R.,
Angers D. A.
Publication year - 1991
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1991.03615995005500010018x
Subject(s) - chemistry , soil water , extraction (chemistry) , distilled water , organic matter , nmr spectra database , infrared spectroscopy , mass spectrometry , carbon 13 nmr , analytical chemistry (journal) , nuclear chemistry , chromatography , organic chemistry , spectral line , geology , soil science , physics , astronomy
The objective of this research was to develop a procedure for the more specific extraction of major organic matter (OM) components from soils. The method was tested on Ap horizons of a Haplaquoll, a Cryoboroll, and a Haploboroll, and on the Bh horizon of a Haplaquod. The four soils were extracted for 2 h with distilled water at a constant pressure of 17.2 MPa and at temperatures of 150, 200, and 250 °C. The OM extracts obtained were characterized by chemical methods, infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy, and pyrolysis‐field ionization mass spectrometry (Py‐FIMS). With one exception, relatively more of the soil N (18–53%) than soil C (17–40%) was extracted from the four soils at the three temperatures. Recoveries of N at 200 and 250 °C were superior to those reported for extractions by 0.1 M Na 4 P 2 O 7 solution from the same soils, while C recoveries were higher from the Bainsville and Regina soils. In general, extracts obtained at 200 °C were richest in carbohydrates and especially in N components. The 13 C‐NMR spectra showed that most of the C in the extracts was aliphatic, occurring in the form of noncarbohydrate carbons bonded to OH and O. The Py‐FI mass spectra indicated that the extracts contained polysaccharides, n ‐fatty acids, n ‐alkanes, n ‐alcohols, sterols, N compounds (pyrroles and pyridines), and mono‐ and dilignins, all typical OM components. Extracts obtained at 150 °C were enriched in n ‐alcohols and diols, whereas extracts at 250 °C were rich in fatty acids. For the extraction of carbohydrates and N components, we recommend an extraction temperature of 200 °C; for soils rich in clay minerals, extractions at 250 °C may be more efficient. For studies on paraffinic OM components, extraction at 150 °C may be appropriate.