Comparison of the composition of humic and fulvic acids prepared by the IHSS method and NAGOYA method

Abstract

The composition of humic acids (HAs) and fulvic acids (FAs) prepared by the NAGOYA (Nagoya University) method and the IHSS (International Humic Substances Society) method was investigated using an an do soil and a brown forest soil. Extraction with a smaller volume of 0.1 N NaOH in the IHSS method yielded HAs containing larger amounts of 0, carboxyl groups, alcoholic hydroxyl groups, hexoses, and uronic acids than those prepared by the NAGOYA method. The contents of C, carbonyl groups, and amino acids were higher in the HAs obtained by the NAGOYA method. The relative content of aromatic C was higher in the HAs prepared by the NAGOYA method, especially in the ando soil.

The FAs prepared by the IHSS method contained smaller amounts of H, N, alcoholic hydroxyl groups, saccharides, and amino acids than the F As obtained by the N AGOY A method, mainly due to the XAD-8 treatment in the IHSS method. The saccharide and amino acid contents in the XAD-8-adsorbed fractions obtained from the FAs prepared by the NAGOYA method using a larger volume of resin, were higher than those in the FAs prepared by the IHSS method. It was concluded that humic substances combined with smaller amounts of non-humic substances were selectively obtained as FAs in the IHSS method.

Key Words:

• elementary composition
• fulvic acids
• functional groups
• humic acids
• XAD-S