Abstract
Physicochemical heterogeneity of a well characterized humic acid (HA) in its complexation with a trace metal lead in model solutions was investigated using pseudo-polarography at a stationary mercury drop electrode, and the differential equilibrium function (DEF) of Pb(ii)-HA complexes was determined. The complexation of Pb( ii) by HA was determined by taking into account the dependence of the strength of the binding on the metal (Pb) loading. Also investigated were the effects of competition of the trace metals copper, nickel, and zinc on the DEF of Pb(ii)-HA complexes in model solutions. The results showed that these trace metals competed with trace metal lead for binding by HA even when present at the same concentrations as that of lead.