Changes in the ecological and biological properties of ordinary chernozems polluted by heavy metals of the second hazard class (Mo,Co, Cr,and Ni)

The pollution of ordinary chernozems by heavy metals of the second hazard class (Mo, Co, Cr, and Ni) results in a decrease in the numbers of saprotrophic bacteria and fungi and bacteria of the Azotobacter genus; the catalase and invertase activities and the rates of the cellulose and urea decomposition also decrease. The soil phytotoxicity becomes higher. With respect to their ecological hazard, the studied heavy metals may be arranged into the following sequence: Cr > Co ≥ Ni > Mo.