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United States Department of Agriculture

Agricultural Research Service

Title: Fractionation of Humic Substances on the Basis of Charge Density Differences

Authors
item Hayes, Thomas - UNIV OF BIRMINGHAM
item Hayes, Michael - UNIV OF BIRMINGHAM
item Clapp, Charles

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: October 29, 1995
Publication Date: N/A

Technical Abstract: Humic substances were isolated from two soils using solutions of pH 7, 10.6, and 12.6. One half of each extract was processed using the IHSS method, and the other half using the XAD-8 and XAD-4 resin (in tandem) procedure. CPMAS **13C-NMR data indicated higher aromaticity for fulvic acids (FA) and humic acids (HA) from the resins, and the resonances at 60- 90 ppm were greater for the extracts by the IHSS method. Carboxyl content decreased and aliphatic content increased as pH of the extractant increased. Materials in the 60-90 ppm resonance (NMR) were greatest for the pH 10.6 extract and least for that at pH 7. There were significant compositional differences between the HAs precipitated at pH 2.5 and those in solution at pH 2. The results indicate that it is important to develop better fractionation methods for humic substances in order to study aspects of their structure and interactions.

Last Modified: 10/25/2014
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