## 3 Results
### Enzymatic Activity
The activity of dehydrogenases of soil when contaminated with silver oxide is shown in Figure 5. At low concentrations of silver oxide (0.5 and 1 PPC), dehydrogenases activity was stimulated on the 10 th and 30 th days by 7 and 13%. With an increase in silver oxide concentration 1-30 PPC, activity decrease was 7-42% relative to the pure soil. On the 30 th day, at a concentration of 3-30 PPC of silver oxide, decrease was 7-64% relative to the pure soil. On the 90 th day, activity decrease was established with a concentration of 1-30 PPC by 11-43% relative to the pure soil. Nitrate of silver at 0.5 PPC inhibited dehydrogenases activity by 13% after 10 days. After 30 and 90 days at the same concentration, enzyme activity stimulation was established by 5 and 10%. When the concentration  
Figure 5: Activity of dehydrogenases in soil after contamination of silver, bismuth, tellurium, and thallium, % of the pure soil. was increased 1-30 PPC after 10 days of the experiment, activity decrease was 18-32% relative to the pure soil. After 30 days, dehydrogenases activity decrease was established at 10 and 30 PPC of nitrate of silver by 11 and 25%. After 90 days, dehydrogenases activity decrease was established only at a maximum concentration of 30 PPC--10% lower than the pure soil. Bismuth oxide at 0.5 PPC inhibited enzyme activity by 10% after 10 days. After 30 and 90 days, there was no significant difference in enzyme activity from the pure soil. With an increase in the concentration of bismuth oxide 1-30 PPC, activity decrease by 17-26% was established. After 30 days from the moment of contamination, decrease was established at a maximum concentration of bismuth oxide (30 PPC) 10% below the pure soil. After 90 days, decrease of dehydrogenase activity was established at concentrations of 10 and 30 PPC of bismuth oxide by 10 and 12%. Nitrate of bismuth at 0.5 PPC inhibited dehydrogenase activity by 19% after 10 days. After 30 and 90 days, at 0.5 PPC of nitrate of bismuth, dehydrogenase activity did not significantly differ from the pure soil. After 10 days, with an increase in the concentration of nitrate of bismuth 1-30 PPC, enzyme activity decreases by 21-31% were established. After 30 days at any concentration of nitrate of bismuth, there were no significant differences from the pure soil. After 90 days, activity decrease was detected only at 30 PPC of nitrate of bismuth, 11% lower than the pure soil. Thallium oxide at 0.5 PPC inhibited dehydrogenase activity by 15% after 10 days of contamination. After 30 and 90 days, there was no significant difference in enzyme activity from the pure soil. After 10 days with an increase in the concentration of thallium oxide 1-30 PPC, the activity of dehydrogenases was inhibited by 23-39% relative to the pure soil. After 30 days from the moment of contamination with thallium oxide with concentrations of 1-30 PPC, dehydrogenases activity decrease after 90 days was established only at a concentration of 90 PPC by 9%. Nitrate of thallium at 0.5 PPC after 10 days of the experiment inhibited the activity of dehydrogenases by 22% relative to the pure soil value. After 30 and 90 days at 0.5 PPC of nitrate of thallium, there was no significant difference from the pure soil. With an increase in nitrate of thallium concentration 1-30 PPC, activity decrease was found by 28-65% relative to the pure soil. On the 30 th day, decrease was established in the range 3-30 PPC by 34-72% relative to the pure soil. On the 90 th day, decrease was established in the range 3-30 PPC by 33-69%, relative to the pure soil. Tellurium oxide at 0.5 PPC inhibited dehydrogenases activity only on the 10 th day: 9% lower than the pure soil; on the 30 th and 90 th days, there was no significant difference in dehydrogenase activity from the pure soil. After 10 days, activity decrease was established with an increase in tellurium oxide concentration 1-30 PPC by 15-29% relative to the pure soil. On the 30 th day, activity decrease was established only at concentrations of 10 and 30 PPC by 13 and 30%.