Evaluating the Efficiency of Bioremediation of Mine Waste Heaps Soils in the Eastern Donetsk basin (Rostov Region)

Mine waste heaps in the Eastern Donetsk basin (Donbass) are long-term sources of heavy metal pollution of adjacent ecosystems. This study assessed the efficiency of induced bioremediation of Technosol (Spolic Technosol (Toxic)) using Elytrigia repens and Medicago sativa, citric acid as a chelating agent, and the arbuscular mycorrhizal fungus Glomus sp. in the waste heap impact zone in the Rostov region. In a model pot experiment with separate and combined application of the chelating agent and mycorrhiza, changes in the physicochemical properties of the soil, plant morphological traits, and the accumulation and distribution of heavy metals (Mn, Zn, Cd, Ni, Pb, Cu, Cr) in plant organs were assessed. The translocation factor and accumulation coefficient were used as biogeochemical indicators. The application of citric acid decreased pH, increased the measured organic carbon content (via dichromate oxidation) and the mobility of metals, while mycorrhization stimulated plant growth and root system development, which together produced a synergistic enhancement of phytoremediation. The greatest effect was observed with the combined use of amendments: the total removal of heavy metals reached 13.8 kg/ha for M. sativa and 3.7 kg/ha for E. repens. The heavy-metal accumulation coefficient in the roots of E. repens reached 15.8 for Cd and 3.7 for Pb, while the translocation factor did not exceed 0.9, indicating the predominant immobilization of pollutants in the root system. For M. sativa, on the contrary, the translocation factor increased to 3.5 (for Cu) and 2.5 (for Cd, Cr), indicating the more efficient transfer of these metals to the shoots. These results indicate the potential of E. repens as a phytostabilizer and M. sativa as a phytoextractor in combination with citric acid and mycorrhiza for restoring heavy-metal-contaminated soils on mine waste heaps.