Comparative Assessment of the Resistance to Lead (Pb) Pollution of Forest, Forest-Steppe, Steppe, and Mountain-Meadow Soils of the Central Ciscaucasia and the Caucasus Regions

Lead (Pb) is one of the most hazardous heavy-metal pollutants in the environment. However, the resistance of different soils and ecosystems to Pb pollution varies greatly. In the present study, the comparative assessment of the resistance to Pb contamination in the forest, forest-steppe, steppe, and mountain-meadow soils of the Central Ciscaucasia and the Caucasus regions was conducted. There were 10 types and subtypes of objects from the forest, forest-steppe, steppe, and mountain-meadow soils which were selected for this study. The laboratory modeling of the effect of chemical soil contamination with lead (II) oxide (PbO) at different concentrations, 100, 1000, and 10,000 mg/kg, were introduced into the soil to check the microbiological, biochemical, and phytotoxic properties of the soil after 30 days of incubation. Soil resistance to Pb stress was assessed by the degree of the decrease in the most sensitive and informative biological indicators of the soil condition. It has been found that the forest-steppe and steppe soils showed a greater resistance than that of the forest and mountain-meadow soils. The regional maximum permissible concentration (rMPC) of Pb was developed for the first time, according to the degree of violation of the ecosystem functions of the soils. The forecast maps were developed for the deterioration of the soil condition during the Pb contamination at variable concentrations in the Central Ciscaucasia and the Caucasus regions.