In order to immobilize heavy metals, sorbents that meet the following three criteria can be used:
1) they are non-toxic
2) they cannot make the physicochemical properties of soil worse, and even improve them
3) they have an immobilizing and specific impact on heavy metals.
This study compares the influence of mineral and organic sorbents, as well as the presence of selenates (VI), on limiting lead toxicity in a soil. The investigations have also focused on evaluating the effects of these sorbents on select physicochemical and chemical properties of studied soil material collected during the twoyear strict pot experiment. Achieved results indicate greater affinity of lead to mineral rather than organic sorbents, although it has depended on zealot and humic acid rates, as well as on physicochemical properties such as soil acidity or soil sorption capacity. Sodium selenate (VI) affected the mobilization of Pb²⁺ ions in the pot experiment and the effect was probably associated with subsoil pH changes and excessive doses of the sorbent used in the experiments.
The study also has aimed at evaluating soil conditions, under which cadmium toxicity appears, as well as at presenting the possibilities of reducing their activities through the use of unconventional immobilizing agents such as zeolites, humic acids, and selenates (VI). The immobilization of Cd²⁺ ions has been affected both by zeolites and humic acids, but only when applied at lower rates. The influences of cadmium mobilization and immobilization on changes in Cd:Zn and Fe:Mn ratios in soil also have been indicated. Clinoptilolit has appeared to be a promising binding agent for immobilizing the cadmium ions. Applying the selenium compounds has given hope as well, because the element is more often considered as required for living. However, the selenium action mechanism is complicated and not uniform, which needs to be further examined.