Effect of the particle-size distribution on the adsorption of copper, lead, and zinc by Chernozemic soils of Rostov oblast

The parameters of adsorption of Cu²⁺, Pb²⁺, and Zn²⁺ cations by soils and their particle-size fractions were studied. The adsorption of metals by soils and the strength of their fixation on the surface of soil particles under both mono- and polyelement contamination decreased with the decreasing proportion of fine fractions in the soil. The adsorption capacity of the Lower Don chernozems for Cu²⁺, Pb²⁺, and Zn²⁺ depending on the particle-size distribution decreased in the following sequence: clay loamy ordinary chernozem ∼ clay loamy southern chernozem > loamy southern chernozem > loamy sandy southern chernozem. According to the parameters of the adsorption by the different particle-size fractions (C _max and k), the heavy metal cations form a sequence analogous to that obtained for the entire soils: Cu²⁺ ≥ Pb²⁺ > Zn²⁺. The parameters of the heavy metal adsorption by similar particle-size fractions separated from different soils decreased in the following order: clay loamy chernozem > loamy chernozem > loamy sandy chernozem. The analysis of the changes in the parameters of the Cu²⁺, Pb²⁺, and Zn²⁺ adsorption by soils and their particlesize fractions showed that the extensive adsorption characteristic, namely, the maximum adsorption (C _max), was a less sensitive parameter characterizing the soil than the intensive characteristic of the process—the adsorption equilibrium constant (k).