Distribution of Heavy Metals in the Coal Mine Waste Dumps Based on Statistical Analysis

Abstract

At the UN Climate Change Conference in Glasgow in autumn 2021 (COP26), world leaders and participants decided to phase out coal energy and gradually replace fossil fuels. At COP26, Ukraine has committed to shutting down state-owned coal-fired power plants by 2035, reducing methane emissions by 30% by 2030 and halting deforestation. The waste dumps are also a detrimental factor in coal mining. The determination of the heavy metals content in the waste dumps of coal mines is a topical issue today, as the results of such studies are part of the monitoring of the environmental safety of mining regions. This scientific article considers the results of research on the heavy metals content in the waste dumps and their distribution in one of the largest coal mines in the Lviv-Volyn coal basin –‘Chervonohradska’ (Ukraine). 2.9 million m3 of rock have accumulated in the dump since 1971. Every year, 40,000 m3 of fresh rock is dumped. Samples were taken uniformly from all sides of the dump in places with no vegetation cover. Note that exceeding the maximum allowable concentrations of the studied heavy metals is observed in all areas except for Zn. Statistical analysis of the results of semi-quantitative spectral studies of waste dumps rockat the Chervonohradska mine site was performed using the Statistica 8 applied statistics package. According to the results of more than 50 samples taken at a depth of 0.3 m, the statistical distribution of heavy metals Mn, Pb, Ni, Cu, Zn and Co in the mine dumps was determined, and a correlation analysis was performed. It was found that the distributions of Cu and Zn in dumps are closest to normal. The nonparametric Spearman coefficient (rs) revealed the average level of correlation of the content of heavymetals in the pairs Mn and Ni (rs = 0.46), Mn and Zn (rs = 0.52), Ni and Zn (rs = 0.57), Cu and Zn (rs = 0.49). Chaotic and uneven discharge of rock onto the open area caused uneven substrate deposition of certain chemical elements in the profile of the dump.