Studies on the properties of organic matter in buried humic horizon derived from volcanic ash

Open Access
Publisher Website
Google Scholar
Abstract
Fulvic acids extracted from buried humic horizons with 0.1 n NaOH+0.1 m Na4P2O7 (1 : 1) were purified and desalted by ultrafiltration. The relationship between the chemical and optical properties of the fulvic acids and age was discussed. The fulvic acid otained by the purification method accounted for about 70% of all the original fulvic acid. The C and N percent of fulvic acids showed the tendency to become lower with age, but the H and O percent, C/N, H/C, and O/C ratios were higher. The total acidity and carboxyl, phenolic OH, and carbonyl contents of fulvic acids of older buried humic horizons were distinctly higher than those of the surface horizon and young buried humic horizons. The fulvic acid of the surface horizon showed the highest humification-degree represented by Δ log K and RF values, but that of buried humic horizons were low. In IR spectra, the absorption band of COOH groups of fulvic acids of buried humic horizons was more clear than that of the surface horizon.