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 Cu(2+), Pb(2+), and Zn(2+) 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 Cu(2+), Pb(2+), and Zn(2+) depending on the particle-size distribution decreased in the following sequence: clay loamy ordinary chernozem similar to 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: Cu(2+) >= Pb(2+) > Zn(2+). 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 Cu(2+), Pb(2+), and Zn(2+) adsorption by soils and their particle-size 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).