HUMIC AND FULVIC ACIDS IN SEDIMENTS AND SOILS OF AGRICULTURAL WATERSHEDS

Humic and fulvic acids were extracted from suspended and bottom sediments and soils of small agricultural watersheds of Southern Ontario and characterized by chemical and spectrophotometric methods and by chemical degradation. Soil humic and fulvic acids were found to be similar to sediment humic and fulvic acids, respectively, in elemental and functional group composition and in surface structural features. Metal-binding capacities of sediment and soil humic and fulvic acids were estimated from their CO2H and phenolic OH group contents. Because watershed soils contained per unit weight considerably more humic materials than did adjacent bottom sediments, the metal-binding capacity due to humic and fulvic acids in the watershed soils was considerably higher than that due to humic and fulvic acids in the sediments. Major products resulting from the alkaline KMnO4 oxidation of soil and sediment humic and fulvic acids were benzenecarboxylic and phenolic acids. The chemical, spectrophotometric and degradation data indicated that sediment and soil humic substances had similar chemical structures.