The binding of trace amounts of lead(II), copper(II), cadmium(II), zinc(II) and calcium(II) to soil organic matter.

The binding by peat of Ca(II), Cd(II), Zn(II), Cu(II) and Pb(II) present at trace-level concentrations in 0.0010, 0.010 and 0.10M sodium chloride, has been studied as a function of the degree of neutralization of the soil organic acid. The theoretically-based method used to express the complexation equilibria requires values for the concentrations of the several mobile counter-ions in the peat phase [M (II), H (+) and N a(+)] and permits estimation of the nature of the complexed species formed in the peat as well as of reasonable values for the formation constants of the species formed. The values of the formation constants thus obtained are independent of the ionic strength of the equilibrating solution, as they should be. This result was unattainable with the earlier methods of computation used for studying these equilibria. The species formed are Ca(II)A(+).HA and M(II)A(+), where M(II) represents Cd(II), Zn(II), Cu(II) and Pb(II).