Assessment of the Danger of Polymetallic Contamination of Mountain Meadow Soil from the Tailings Dump of the Urup Mining and Processing Plant

Urup Mining and Processing Plant is the largest enterprise in the South of Russia for the extraction and processing of copper pyrite, the waste of which contains high concentrations of heavy metals. As a result of their migration, the soil bordering the existing tailing dump is polluted. The work estimates the degree of contamination of the upper 10 cm layer of mountain meadow chernozem soil (Mollic Leptosol) with 48 potentially toxic elements (PTE) depending on the distance from the tailings dump and the impact of pollution on the biological properties of the soil. The priority pollutants with which the soil is most polluted have been identified: at a distance of 5 m from the tailings dump, the Ag content in the soil is 63 times higher than in the background soil; Sb - 25; Hg - 23; Cu - 19; Te - 19; Zn - 14; Cd - 14; As - in 13; Mo - in 12; Pb - in 6; Sn - in 3.7; Bi - in 3.6. At the same time, at 300-400 m from the tailings dump, soil pollution is no longer observed. The degree of decrease in biological indicators of soil condition (activity of catalase, dehydrogenase, invertase, urease, total number of bacteria, abundance of bacteria of the genus Azotobacter, germination, length of roots and shoots of radish seedlings, etc.) correlates with the content of PTE in it. As we move away from the tailing dump, the biological properties of the soil improve. The abundance of bacteria of the genus Azotobacter, the activity of dehydrogenases and invertase are the most sensitive to polymetallic contamination of mountain meadow soil from the Urupsky mining and Processing Complex, and the activity of dehydrogenases, catalase, and invertase is the most informative (correlating with the content of PTE in the soil).