Distribution of different forms of manganese in coal mining waste: A case study of the Vizeyska mine, Ukraine

Abstract This study assesses the ecological hazards posed by the Vizeyska mine in the Lviv-Volyn coal basin, focusing on manganese distribution in mine waste and its environmental impact. The spoil heap, formed from mining operations between 1960 and 2009, covers 225,000 m 2 and contains approximately 5.1 million m 3 of waste rock, with a heterogeneous composition of burnt and unburnt mudstones, siltstones, sandstones, and coal. Sampling and analyses were conducted to quantify manganese in bulk, acid-soluble, and bioavailable forms using standardized methods. The results revealed high variability in manganese concentrations, with bulk forms ranging from 119 mg/kg to 3850 mg/kg, highest in burnt siltstones and lowest in sandstones. Acid-soluble manganese concentrations were highest in unburnt coal (218 mg/kg) and lowest in burnt mudstones (10 mg/kg). Bioavailable manganese, extracted using ammonium acetate, displayed a different trend, being highest in burnt siltstones (95 mg/kg). Water-soluble manganese concentrations were minimal, reflecting its limited mobility in this environment. The combustion process significantly alters manganese distribution by increasing bulk concentrations through the burning of organic matter, while simultaneously reducing the presence of mobile forms. Soil samples showed manganese levels below regional thresholds, indicating minimal ecological risk. However, elevated manganese in water-soluble forms during specific processes highlights the potential for localized contamination. The study concludes that spoil heap materials can be used in construction with minimal environmental risk. Yet, the dynamic behavior of manganese in different forms necessitates ongoing monitoring and further research to mitigate potential long-term ecological impacts.