Humic substances considered as a heterogeneous Donnan gel phase

Article Abstract:

The binding of organic pollutants to humic substances depend on pH and salt concentrations. To tests this hypothesis, a Donnan type model in combination with a site-binding model was used. It was shown that type of ions in solution determines the rate of protonation of various humic substances. The Donnan approach, however, was not physically realistic for fulvic acids. For humic acids, the approach suggested that the intrinsic binding properties of these substances are more dependent on ionic strength than on pH.

Pollutants, Structure-activity relationships (Biochemistry), Organic compounds

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Fluorescence characterization of IHSS humic substances: total luminescence spectra with absorbance correction

Article Abstract:

The total luminescence spectra of humic substances from the International Humic Substances Society were determined using a spectrofluorometer. Data indicated variations in the spectra between soil-derived and aquatic-derived IHSS humic substances and between soil- and aqueous-derived humic and fulvic acids. The changes in pH were found to have significant effects on the substances' fluorescence spectral characteristics. In contrast, ionic strength of the humic substances had no significant effect on their spectra.

Measurement, Humus, Luminescence

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Potentiometric titrations of humic substances: do ionic effects depend on the molecular weight?

Article Abstract:

The correlation between ionic strength effects and molecular weights for various fulvic acids is investigated using potentiometric titrations of humic substances. The results showed that there is an apparrent correlation between molecular weight distribution and ionic strength effects. However, humic substances with equal or similar molecular weights exhibited ionic strength effects which increased proportionally to the polydispersity of the molecule.

Molecular weights, Ionic solutions

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