Changes in the microbiological and biochemical properties of soil contaminated with zinc

Zinc is an essential element for all living organisms, but overexposure to this element can have strongly toxic effects. A pot experiment was carried out to evaluate the influence of different zinc concentrations (0, 100, 300, 600, 1200, 2400, 4800 mg Zn2+ kg-1 of soil) on the soil biological activity by analyzing changes in soil stability over time and by determining the resistance (RS) of microorganisms and soil enzyme activity. The influence of Zn2+ on the growth and development of oat and white mustard was evaluated. Overexposure to zinc inhibited the growth of soil microorganisms, the activity of soil enzymes, and the growth and development of plants. Excessive zinc doses cause lower microbial biodiversity and enzyme activity. Bacteria of the genus Azotobacter were most sensitive and spore-forming oligotrophic bacteria were least sensitive to excessive zinc doses. β-glucosidase was most resistant and arylsulfatase was least resistant to the analyzed element. The resistance of the tested microorganisms and enzymes decreased with an increase in zinc accumulation in the soil environment. White mustard was more sensitive to zinc contamination than oat and zinc doses of 2400 and 4800 mg Zn2+ kg-1 led to the death of white mustard plants. The results of this study indicate that soil contamination with zinc poses a threat for living organisms. In areas with a higher risk of zinc deposition, the content of this element in soils should be monitored more frequently than prescribed by environmental protection regulations.