Physico-chemical properties of some aquatic fulvic acids : Functional groups and stability

University dissertation from Linköping : Linköpings universitet

Abstract: Humic material constitutes a category of naturally produced organicmacrocompounds, widely spread in both terrestrial and aquatic systems and accounting for up to 70% of the total soil carbon and 50% of the dissolved organic carbon in surface waters. Humic material is formed as the result of complex chemical transformations of biomass. The humic substances play an important role for the speciation and distribution of trace components in the environment. The complex and diversified interactions between humic material and trace components are intimately related to the structure, fimctionality and stability of the various humic substances. The detalied mechanisms behind these processes are not sufficiently known.Studies of fimdamental properties and stability of some aquatic fulvicacids have been carried out in the present study. The total acidity has been estimated by aqueous and nonaqueous titrations on humic substances of different origin. A technique for derivatization and determination of the acidic fimctional groups has been developed. The redox properties of humic substances are discussed, and the reduction of particularly mercmy by a fulvic acid is demonstrated. The effects of radiation exposure (gamma as well as accelerated electrons) on the degradation of a fulvic acid sample has been studied, particularly with respect to changes in acidity and molecular weight distribution.In conclusion, the thesis presents some alternate approaches for thecharacterization of humic matter which could be used to complement other methods for the improvement and comprehensive understanding of the role of humic susbtances in the aquatic environment.

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