Submitted to: International Humic Substances Society Conference
Publication Type: Abstract only
Publication Acceptance Date: 9/8/1996
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Recently XAD-8 and XAD-4 resin-in-tandem procedures used for the isolation of humic substances from water have been adapted for studies of soil humic substances. The method used for the isolation of the IHSS humic substances standards from soils is compared with a procedure that uses XAD resin technology. Humic substances were isolated in solvents of different pH values, using sodium pyrophosphate and sodium pyrophosphate/sodium hydroxide. Amino acid and neutral sugar analyses were carried out on the fractions. The sugar contents were greatest in the XAD-4 acids, and lowest in the fulvic acids (FAs). The contents of neutral sugars in the humic acids (HAs) and FAs isolated by the two methods were similar. The neutral sugars made up 4.2-7.5 percent of the HAs, 4.4-12.0 percent of the FAs, and 15-22 percent of the XAD-4 acids. Based on the ratios of Ga1+Man/Ara+Xyl, and Rha-Fuc/Ara+Xyl, it is suggested that the XAD-4 acids have significant inputs from microbial sources. In general, the concentrations of amino acids (AAs) in the isolates decreased in the order: HA > XAD-4 acids > FA. The AA contents of the HAs isolated by the IHSS and by the resin-in-tandem procedures are similar. The HAs contain 7.0-16.3 percent AAs. The soil FAs also contain significant quantities of AAs, 3-6 percent. The total acidic and neutral hydrophilic fractions comprise the bulk of the AAs in the FAs and HAs (about 80 percent).