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

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Abstract
Hexose and neutral sugars in hydrolysates of fulvie acid fraction from buried humic horizons extracted successively with 0.1 n NaOH and 0.1 m Na4P2O7 were determined. Hexose and uronic acid in 75% ethanol precipitates from the fulvic acid were also determined. The proportion of mannose in hydrolysates of fulvic acid extracted with NaOH showed a tendency to increase with age, but the proportion of plactose decreased. The proportion of arabinose and xylose in hydrolysates of the fulvic acid extracted with Na4P2O7 decreased with increasing age. Most of the constituent neutral monosaccharides of the polysaccharides in fulvic acids of the two extracts were hexoses. The uronic acid to hexose ratios of the 75% ethanol precipitates of the (u1vic acid extracted with NaOH did not show large variation from 28,000 years B.P. to the present. However, the values of 75% ethanol precipitates of fulvic acid extracted with Na4P2O7 increased with increasing age.