A series of column experiments were performed to investigate the mechanisms of silicon （Si） and heavy metals （HM） interaction in the soil. The column experiments were conducted with Gray Forest Soil treated by various forms of active Si （diatomaceous earth, zeolite, amorphous silicon dioxide and concentrated monosilicic acid） in environment polluted conditions with soluble salts of Cd, Cu, Ni and Pb. All Si-rich substances used in the test were analyzed with electron scan microscope. The results of HM immobilization in soil by Si-rich materials showed that diatomaceous earth and concentrated monosilicic acid immobilized HM better than zeolite and amorphous silicon dioxide. The reductions in HM mobility were re- alized by the reaction between monosilicic acid and HM in soil solution and by adsorption of HM on Si-rich surface. The intensity of HM movement through soil depended on the type of HM. The maximum reduction of HM mobility with application of Si-rich substances was obtained for Cd and Ni and less effect was observed for Cu and Pb.
