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The change in soil-forming processes and, as a result, in the ecosystem due to nearly 300-year long outflow of highly saline waters from ancient brine wells is considered for Perm Krai in Russia for the first time. The study area is located in the high floodplain of the Usolka River valley. Sodium-chloride ancient brine wells with mineralization of about 30 g/L flow in streams over the soil surface and enter the Usolka River. The paper considers three soil types at various distances from a saline stream. The main pedogenic processes are the sod-forming process and gleying in alluvial soils. Soils in Gleyic Fluvisols (background)—Gleyic Fluvisols (Sulfatic) (transition)—Solonchak (affected by sodium-chloride brines) series were studied in terms of occurring soil-forming processes. All studied soils are formed under hydromorphic conditions. It is evidenced by gleization. However, the morphological and physicochemical properties of the soils differ. The presence of water-soluble ions in the solonchak suggests that salinization is occurring. The sum of toxic salts was 0.94% which was several times higher than in the transition and background soils. The sodium adsorption ratio (SAR) ranged from 10.4 to 21.6, with a рН of 8.3–9.1. The saline soils were more alkaline (pH average 8.8 and 9.3) than the background soil (pH 8.1). SAR decreased significantly in the Solonchak—transition—background soil series from 16.9 to 0.7. The aforementioned observations, as well as physical properties of the saline soil, clearly show the entry of sodium into the solonchak adsorption complex, indicating the solonization process. The study area is characterized by the presence of salt-tolerant species of herbaceous plants and an obligate halophyte. Salicornia perennans Willd, a halophyte, was discovered in the wells’ discharge area at a distance of 0.2–1.5 m from saline streams. The analysis of the long-term impact of highly mineralized waters on the natural environment will aid in revealing and forecasting ecosystem changes caused by potash mining in Perm Krai for environmental risk assessment for new and existing potash enterprises.

The environmental impact of deposit development can be indirect and can cause combined geochemical processes in ecosystems. These must be taken into consideration under environmental forecasting and environmental risk assessment. Soil degradation in the Taiga Forest is considered, within the area of Verkhnekamskoye potash deposit (Russia), as an example of such environmental transformation. Here, the mechanism and characteristics of the anthropogenic salinisation of alluvial soils under potash deposit development are newly described. It was found that there is a strong anthropogenic impact of the potash industry on valley soils where the contaminated Na-Cl groundwater discharges or is close to the surface. The valley soils are characterised by high salinity, and the sum of toxic salts in soils has reached 26%. Alluvial gley humic clay chloride saline soil (Gleyic Fluvisols (Salic, Loamic, Technic)) and secondary solonchak on alluvial humic clay soil sulphate-chloride gypsum-containing surface-gleyed (Chloridic Gleyic Fluvic Solonchak (Hypersalic, Loamic, Technic)) were formed in hydromorphic conditions. Morphological, physicochemical and mineralogical analyses were carried out. Under hydromorphic conditions, Chloridic Gleyic Fluvic Solonchak (Hypersalic, Loamic) was described to show a hydrotroillite layer and reddish-yellow iron-rich precipitates on its surface. The top soil horizon has the highest content of iron minerals (up to 84.9%) and Fe-bearing plant residues (up to 20%). Additionally, the spongy and gel-like organic materials, as well as the siliceous remains of diatoms, are enriched in Ca, Fe, Cl, K, Na, S and P. The lower soil horizon consists of black gel-like phases and hydrogen sulphide settings with a high content of plant residues. The insoluble part of the samples contains up to 84% hydrogoethite. The sources of iron in soils and bottom sediments include the iron-enriched Sheshma sediments speckled rocks, slurry material, halite wastes and soil minerals of alluvial gley soils.