Forms of binding of copper, lead, and cadmium in carbonate type soil studied by differential pulse anodic stripping voltammetry

A sequential extraction procedure was used for determination of the total and extractable forms of Cu, Pb, and Cd in soil by DPASV for determination of trace metal contents. Detection limits for these heavy metals were about tenth of mu g dm(-3). The total content of Cu, Pb, and Cd, soluble, exchangeable, sorbed, and organically bound forms was determined. Analysis of a loess-carbonate black soil sample was evaluated. The Cu content bound to humic matter was 47 %, 40 % of it bound to humic matter in originally free form and 7 % to humic matter in originally bound form. The occluded Cu forms represented 41 %, the residual bound Cu 12 %. Lead has a minor ability to form complexes with organic material compared to copper and this was confirmed by the determination of its distribution in the studied soil sample fractions. 35 % of Pb was bound to the humic matter. The occluded form represented 49 % and the residual form 14 % of the total Pb content in the soil. In spite of the very low initial Cd content in the soil sample it was determined that the major part of Cd was bound to the humic matter.