## 3 Results  
### Microbiological Indicators  
The total number of bacteria in the soil contaminated with silver oxide varied during the exposure period (Figure 2). At low concentrations (0.5-1 PPC), the number of bacteria decreased by 35, 29, and 20%. With an increase 3-30 PPC, the number of bacteria was inhibited by 44-53%. On the 30 th day, an increase in soil toxicity in the number of bacteria was found, with a recovery on the 90 th day by 5-11% compared to the 30 th day. Nitrate of silver, compared with oxide, had a more expressed toxic effect on the number of bacteria already at 0.5 PPC-24, 37, and 22% on the 10, 30, and 90 th days. With an increase in the concentration of nitrate of silver 1-30 PPC, the decrease of the number of bacteria was 19-73% of the pure soil. Bismuth oxide at 0.5 PPC on the 10 th day had no effect on the number of bacteria. At the same time, on the 30 and 90 th days, decrease at 0.5 PPC was 13 and 11%. Within 90 days, bismuth oxide 1-30 PPC inhibited the number of bacteria by 13-40%. Nitrate of bismuth at a concentration of 0.5 PPC was toxic by 30-36% of the pure soil. When the concentration was increased to 30 PPC, the toxicity increased by 44-71% of the pure soil. The toxicity of nitrates compared to oxides was 30-35%. Thallium oxide at 0.5 PPC on the 30 and 90 th days was toxic by 20 and 17%. Increasing the concentration 1-30 PPC increases the toxicity of thallium oxide by 24-69% relative to the pure soil. Nitrate of thallium at 0.5 PPC was very toxic on the 10 th and 30 th days by \begin{table}
\begin{tabular}{c c c} \hline \hline
**Biological Indicators** & **Materials and Conditions** & **Reference** \\ \hline Activity of catalase & gasometrical method & [56] \\ \hline Activity of dehydrogenases & PE 5800 VI spectrophotometer & [57] \\ \hline The total number of bacteria & Carl Zeiss Axio Lab A1 microscope & [59] \\ \hline _Azotobacter_ sp. abundance &bacterial air-box (BAVnp-01—“Laminar-S”). & [59] \\ \hline germination of winter wheat & & \\ (_Triticum aestivum_ L.) & Binder KBW-240 climate chamber & [60] \\ \hline root length of winter wheat & & \\ (_Triticum aestivum_ L.) & Binder KBW-240 climate chamber & [60] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Methods for assessing the ecological state of soils. 52 and 54% relative to the pure soil. On the 90 th day, the number of bacteria was restored by 22% compared to the 30 th day. Tellurium oxide at 0.5 PPC was toxic on the 10 th day of the experiment already--18% lower than the pure soil. At the same time, on the 30 th and 90 th days, the number of bacteria decreased by 20 and 33%. Increasing the concentration of tellurium oxide by 1-30 PPC inhibited the number of bacteria by 14-69% relative to the pure soil. Nitrate of tellurium, as well as thallium nitrate, inhibited the number of bacteria by 54-58% already at 0.5 PPC. With an increase in the concentration of tellurium up to 30 PPC, the decrease of the number reached up to 90%. The _Azotobacter_ sp. abundance at low concentrations (0.5-3 PPC) of both chemical forms of silver, bismuth, tellurium, and thallium did not differ from the pure soil (Figure 3). Differences in decrease were found at concentrations 10 and 30 PPC. Silver oxide at 10 PPC on the 10 and 30 th days inhibited the _Azotobacter_ sp. abundance by 17 and 8%. On the 90 th day, the _Azotobacter_ sp. abundance was restored to the level of pure soil. The concentration of 30 PPC also inhibited the value of the indicator only on the 10 and 30 th days, by 76 and 39% relative to the pure soil. Figure 3: _Azotobacter_ sp. abundance of soil after contamination of silver, bismuth, tellurium, and thallium, % of the pure soil. Figure 2: The total number of bacteria in soil after contamination of silver, bismuth, tellurium, and thallium, % of the pure soil. Nitrate of silver had a toxic effect on the _Azotobacter_ sp. abundance only by 30 PPC on the 10 and 30 th days of the experiment by reducing the indicator by 43 and 39% relative to the pure soil. On the 90 th day, the indicator recovered to the level of pure soil.