OXYGEN-CONTAINING FUNCTIONAL GROUPS IN ORGANIC SOILS AND THEIR RELATION TO THE DEGREE OF HUMIFICATION AS DETERMINED BY SOLUBILITY IN SODIUM PYROPHOSPHATE SOLUTION

Abstract

Carboxyls, phenolic and alcoholic hydroxyls, carbonyls, and methoxyls were determined in 20 organic soil samples that ranged from peats, mucky peats, peaty mucks to mucks. The absorbance of a sodium pyrophosphate extract of each sample served as basis for grouping the samples into three broad classes: (i) peat, (ii) mucky peat – peaty muck, and (iii) muck.A statistical analysis of the analytical data showed that (a) the determination of COOH and of OCH3 groups distinguished between the peat and muck classes, and (b) measurement of alcoholic OH groups differentiated between the peat class and the intermediate class and between the peat and muck classes. The experimental data indicated that increased humification was associated with increases in COOH, OCH3, and to a lesser extent of C==O groups, increased solubility in dilute sodium pyrophosphate solution, decreases in alcoholic OH groups but practically no changes in phenolic OH groups. It is suggested that functional group analysis could be used as a supplementary diagnostic tool for assessing the degree of humification of organic matter in organic soils and could thus serve as an aid in the classification of organic soils.