# Current State of the Gold Mining Waste from the Ores of the Ursk Deposit (Western Siberia, Russia)
## 5 Conclusions  
A comprehensive study of the Ursk mine tailings dumps and drainage system was carried out using the methods of electrical resistivity tomography, magnetic, thermal imaging, photogrammetry, and hydrochemical sampling.  
Three main zones were identified: oxidation, leaching, and mixing of drainage with the waters of the Ur River.  
The oxidation zone (Figure 12) is marked by low electrical resistivity (1-10 \(\Omega\cdot\)m), low values of the modulus of the magnetic induction vector (\(-\)10 nT), and heating by +5 \({}^{\circ}\)C compared to the solid matter in dump that is not actively exposed to water. The acid solution (pH 3.61) with high electrical conductivity (16,000 \(\upmu\)S/cm) and concentrations of sulfate anion (up to 4500 mg/L), metals, and metalloids of ore association (Fe, Cu, Zn, Cd, Pb, Ba, Ni, Co, Sb, As, Hg, and Be) is formed in this zone. A feature of the Ursk drainage is a high concentration of dissolved Fe (980 mg/L), As (1300 \(\upmu\)g/L), Hg (34 \(\upmu\)g/L), and Ba (83 \(\upmu\)g/L).  
The leaching zone (Figure 12) is characterized by negative anomaly of the magnetic induction vector (\(-\)20 nT) and low resistivities (5-10 \(\Omega\cdot\)m). A high-conductivity anomaly in this zone can be found at a depth of 15.5 m, which indicates the penetration of the acid drainage into the deep horizons. The acidic drainage stream destroys the root systems of trees, dissolves the mineral complexes of the soil, beaches, and carries out rock-forming elements (Ca, Mg, K, and Na). The primary geochemical barrier is formed in the middle part of this zone due to sorption of the elements on the soils. The conductivity of the drainage solution drops to 2500 \(\upmu\)S/cm, concentrations of SO\({}_{4}\)\({}^{2-}\) and Fe decrease to 1100 mg/L and 430 mg/L, and those of As, Hg, and Ba decrease to 50, 6, and 67 \(\upmu\)g/L, respectively.  
The second geochemical barrier Is formed in the mixing zone due to neutralization of acid mine drainage by Ur River waters. The electrical conductivity decreases to 450 \(\upmu\)S/cm, the concentration of SO\({}_{4}\)\({}^{2-}\) decreases to 20 mg/L, and concentrations of Fe, As, Hg, and Ba drop to 0.38 mg/L, 2.3, 1.3, and 73 \(\upmu\)g/L, respectively.  
The application of the proposed complex of methods at abandoned mine tailings sites will allow assessing thermal pollution, the area subject to acid weathering, and the range of chemical compounds migrating with drainage flows, as well as enable a forecast of the environmental hazards.  
**Author Contributions:** Conceptualization, N.Y., L.T., E.T. and P.O.; methodology, S.V., I.F., K.T. and T.K.; validation, N.Y. and L.T.; formal analysis, S.V.; investigation, N.Y. and L.T.; resources, N.Y.; data curation, N.Y., L.T. and P.O.; writing--original draft preparation, N.Y., L.T. and P.O.; writing--review and editing, N.Y.; visualization, N.Y., L.T. and P.O.; supervision, N.Y.; project administration, N.Y.; funding acquisition, N.Y. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by Ministry of Education and Science of Russian Federation, grant number FWZZ-2022-0029. The APC was funded by Russian Foundation for Basic Research, grants number 20-05-00336.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.  
**Data Availability Statement:** Data are available upon request to the corresponding author.  
**Conflicts of Interest:** The authors declare no conflict of interest.