Characteristics of humic and fulvic acids in Arabian Sea sediments

Abstract

Humic and fulvic acids isolated from some of the shelf, slope and offshore sediments of the Arabian Sea were studied. The molecular weight, functional groups, elemental composition and infrared spectra were examined. Humic substances, dominated by humic acids contributed 22-53% of the sedimentary organic matter. The humic acids in turn are dominated by the high molecular weight fraction (>300000). A major portion of fulvic acids was mostly present as <10000 molecular weight fraction. The elemental composition ranges of HA and FA are C: 60.3-50.3%, H: 6.9-5.7% and N: 4.1-2.0% and C: 46.5-28.1%, H: 8.9-3.6% and N: 4.8-1.6% respectively. The C/N ratio points out to the dominance of terrigenous matter in the formation of humic substances. The infrared spectra of humic acids and fulvic acids although similar exhibited perceptible variations that could be interpreted in terms of changing phenolic, carboxylic and nitrogen contents.