Impact Of Coal Mining Activities On The Surface Water Quality (Case Study Of Tugnui River Basin, Russia)
Efimov, Vasilii (1); Chalov, Sergey (1); Timofeev, Ivan (2); Kosheleva, Natalya (2)
1: Department of Hydrology, Lomonosov Moscow State University, Moscow, Russia, Russian Federation; 2: Department of Landscape Geochemistry and Soil Geography,Lomonosov Moscow State University, Moscow, Russia, Russian Federation
Coal mining leads to a significant change in water quality. This work aims at characterization of pollutant fluxes in surface water and assessment of major physico-chemical mechanisms, governing the attenuation and fate of pollutants below the coal mine. Tugnui river basin (Buryatia) with one of the largest in Russia coal mine was chosen as a study object.
The results are based on 29 representative stations, where 68 samples of water, suspended sediments and bottom deposits were collected during a low water period in august 2018. The major hydrological and hydrochemical properties (water discharges, turbidity and grain size distribution, pH, alkalinity, main ions, nutrients, fluorine and organic carbon content) were determined and also the bulk contents of heavy metals and metalloids (HMMs) were analyzed by ICP-MS.
Water of background areas belongs to hydrocarbonate-calcium type with mineralization 150–200 mg/l; pH 8–8.5. The relative content of sodium increases downstream the confluence with wastewater of the mine (mineralization 800–1000 mg/l; pH 8–9.1). High concentrations of SO4 (340 mg/l) and NO3 (> 500 mg/l), which are 30-50 times exceed background level, were found in mine water. They are leached from the coal deposits, and come due to explosion operations. Sewage has increased concentrations of P-PO4 (700-900 µg/l).
Lithogeochemical features of the Tugnui River basin cause increased background concentrations of HMMs in water (TDS) and in suspension (TSS). In comparison with the average TDS concentrations of HMMs in world rivers, the background waters are enriched in Zn, Sr, Mo, U. Within the development area Co (EFwater 500), Sb, Cd, Ni, Mo, Mn, Cu (8-1,5) come in river water with emissions during coal excavation and from motor vehicles. Concentrations of suspended V, Mn, Co, Ni, Cu, Zn, Mo, Cd, W, Pb are above background. The total pollution of waters is moderately dangerous (Zc 19-21). The main part of the HMMs (59-89%) migrates in clay fraction which is up to 59% of all suspended particles.
The river basin is subject to various anthropogenic impacts. The influence of coal mining can be traced for 24 km in the upper reaches of the river due to non-effective purification system. Sludge ponds retain up to 70% of suspended particles, only a small fraction spreads downstream. In the middle course, the influence of wastewater from agricultural fields and municipal sewage increases: the organic and nutrient inflow leads to water bodies eutrophication.