Complexing capacity of soil fulvic acid for Cu2+, Cd2+, Mn2+, Ni2+, and Zn2+ measured by dialysis titration: a model based on soil fulvic acid aggregation

Abstract

The dialysis method of metal ion speciation is investigated as a technique to determine complexing capacities of soil fulvic acid (SFA) towards Cu²⁺, Cd²⁺, Mn²⁺, Ni²⁺, and Zn²⁺, between pH 5 and 7. The complexing capacity values for each metal ion usually increase as pH increases. At the same pH the values for Cd²⁺, Mn²⁺, Ni²⁺, and Zn²⁺, are similar, but Cu²⁺ values are significantly higher. The results are interpreted on the basis of a model involving the aggregation of SFA by metal ions, especially Cu²⁺.