Soil Monitoring Of Complex Salinization Under Potash Mining
Mitrakova, Natalya; Khayrulina, Elena
Perm State University, Russian Federation
Development of potash deposits leads to accumulation of large quantities of mining wastes that negatively impact on the environment. These wastes are mainly presented by the slurry storage facilities, salt tailings piles and brines. The clay-salt slurry typically contains 35–40% water-soluble salts and 60–65% insoluble clay materials. The brines have a Na–Cl composition and more than 300 g/L of total dissolved solids. The solid halite wastes are deposited as tailings piles, which consist of 95% NaC, 1.5–2.0% KCl, 0.1% MgCl, and 2.0% CaSO4. Water-soluble minerals are easily weathered and form drainage water that is characterized by Na–Cl composition. Salinization of groundwater and surface water are the most discussed issues, however, it is potash mining that causes surface subsidence and the increase of the water table level. The processes of waterlogging are developing. As a result of ground water salinization we have observed deep transformation of soils not only around potash mines but on larger areas around them.
Our studies were carried out on the territory of Verkhnekamskoe potash deposit in the Lyonva Valley. Activity of two potash mines with slurry storage facilities and salt tailings piles have led to groundwater salinization with Na–Cl composition and mineralization of 28 g/L.
In Lyonva Valley we firstly classified solonchak secondary (saline soil) on alluvial soil and alluvial humic gleyic Na-Mg-Cl solonchak-like soils instead of zonal alluvial humic gley soils. Top soil horizon (5-15 cm) has high ion concentrations (mg/kg): Cl- – 330.15; Ca2+–76.0; Na+– 39.1; Mg2+– 20.4; K+–7.8. But at a depth of 50 cm ion concentration is increasing and in the lower soil horizon at a depth of 70 cm contents of Cl- reaches up to 901.7 mg/kg, Ca2+– 272; Na+ – 108.1; Mg2+ – 79.2.
Under waterlogging processes saline secondary Na-Ca-SO4-Cl soils on alluvial clay-loam were formed. These soils are characterized by the highest concentrations of Cl- (14420.0 mg/kg), K+ (9500.4 mg/kg), SO42-(8107.2 mg/kg), Na+ (2500.1 mg/kg). The distribution of ion concentrations in the soil profile changes insignificantly.
The presence of dead trees in the Lyonva River indicated that this process has developed only recently and it could be either a result of rising of water tables or mining subsidence.
For the environmental assessment of potash mining, the soil researches have evidenced complex changes in ecological and geochemical characteristics that are related to the increase of ground water salinization area.