Measurements of Binding Site Concentrations in Humic Substances

摘要

The use of thermodynamic models to calculate the effects of humic substances on metal speciation requires that the complexation capacity (CC) of the humic substance be determined. If the CC of a humic substance is viewed as a compositional rather than a thermodynamic property, then the conventional approaches toward experimental measurements and calculations of complexation capacities need to be reexamined. It is proposed here that the CC of a humic substance is approximately equivalent to its total exchangeable acidity and that the extent to which this CC can be realized in experimental measurements is strongly a function of pH, ionic strength, nature of the metal being complexed, and the concentration of humic substances used in the measurements.