GEOECOLOGICAL PROBLEMS OF THE KHOLBOLDZHINSKOE BROWN COAL DEPOSIT DEVELOPMENT

The object of research included surface- and groundwater in the area of the Kholloldzhniskoe brown coal deposit located in the strand of Lake Gusinoe, which is of great fishery and recreational importance for local population. The deposit was developed for 38 years and occurred in a mothballed state for 24 years. The purpose of study was to reveal the regularities in changing chemical composition of surface- and groundwater during the field development and long-term storage of mining waste. The tasks were to determine the water volume contained in mine workings and to find sources of its inflow into the quarries; to study the regularities of groundwater formation within overburden dumps; to describe the chemical composition of surface- and groundwater and to compare them with the maximum permissible values for fishery water. Field and laboratory studies were carried out to solve the tasks set. Observation wells were drilled at the foot of overburden dumps to monitor the groundwater table and its chemical composition. The trace element composition of water was studied using the inductively coupled plasma method (ICP MS) on the quadrupole Agilent 7500 ce mass spectrometer. It was found that the groundwater flow direction changed in the technogenically disturbed area to discharge into the mine workings. The total volume of quarry water reaches 2 million m³. In technogenic water bodies, water of several aquifers mixed. Concentrations of molybdenum, copper, zinc, and strontium were found to exceed significantly the MPC for fishery water. Mine development has increased rock permeability, and a significant portion of surface runoff has been turned into underground runoff. Precipitation falling in the mine working area infiltrates through overburden dumps, interacts actively with weathered coal and host rocks, and dissolves toxic components. The groundwater flow discharging into Lake Gusinoe shows high levels of chemical elements of the second, third and fourth hazard classes. Among them, molybdenum, lead, strontium, tungsten, copper, zinc, nickel, cobalt, manganese, iron, aluminum, phosphorus are detected. To prevent contamination of Lake Gusinoe with liquid waste from coal mining, it is necessary to rehabilitate overburden rocks and eliminate the threat of water outbursts from technogenic water bodies. To reduce environmental hazard in the area, it is necessary to pump technogenic water into the quarries with the surface level below Lake Gusinoe.