Acidic sulphate water influence on terricon soil pollution in the Karabash ore district
Authors:   Saint-Petersburg State Agrarian  University, SHABANOV Mikhail , MARICHEV Maxim ,   St-Petersburg State Agrarian University, NEVIDOMSKAYA Dina ,   Southern Federal University, MINKINA Tatiana ,   Southern Federal University
Published: March 2024

Introduction. Technogenic mineral formations are one of the potential sources of pollutants, including heavy metals. On the territory of the Karabash ore district as a result of copper and cobalt ore mining, waste rock heaps are formed and stored. As a result, under the influence of acidic precipitation, oxidation of the surface part of the spoil heap occurs, and the formed products, among which there are heavy metals, are transported by water and aeolian streams to the adjacent landscapes. Methods and materials of research. In the course of work investigated the spoil heap formed by wastes of the mine «Tsentralnaya» in Karabash, Chelyabinsk region. Sampling from the surface of the spoil heap, as well as soil samples with distance from it. The mineralogical composition was determined in the rocks of the heap by X-ray diffraction with Cu-Kα-radiation and crystal mono chromator. Quantitative content of heavy metals was carried out by X-ray spectral method. The reaction of the medium and carbon content of organic matter, as well as the gross content of mobile and water-soluble forms of heavy metals were determined by inversion voltammetry method. According to the results of quantitative analysis of heavy metals in soils, the coefficient of total pollution - Zc was calculated. Research results and discussion. As a result of laboratory analyses, the lithological composition of the main rocks of the spoil heap was determined, which is represented by the main two types: 1) altered quartz-chlorite-sericite schist; 2) highly transformed rocks with no discernible primary mineral composition. The first type contains mainly quartz, feldspars, mica, chlorite and pyrite. The mineralogical composition of the second group is represented by silicates and alumina silicates with gypsum, hydro-arosite and calcium sulphate. Oxidation and limonitization of spoil heap rocks is going on everywhere. In the chemical composition of spoil heaps, predominant are macro-elements Fe, Ca, Mg, K, Na, P, their concentration ranges from 0.13 to 20.38 %, also present in high concentrations of S 0.27-12.31 %, As 0.007-0.11 % and Zn 0.026-0.087 %. All other elements are less than 0.01 %. As a result of rock oxidation such heavy metals as Zn, Cd, Pb, Cu migrate from dumps in the form of sulphates, which is promoted by lowering the pH of the environment. It is revealed that soils located in the depression, on the way of hydro-genic flows, are geochemical barriers for heavy metals. The gross content of heavy metals in soils varies within high limits. Maximum concentrations were recorded in 0-10 cm layer in organogenic and grey humus horizons:Zn - 2890 mg/kg; Cd - 32 mg/kg; Pb - 1270 mg/kg; Cu - 3060 mg/kg. In the vicinity of the spoil heap, relatively high content of mobile forms of heavy metals was recorded inside the soil profile, in the surface layers of soils, with distance from the spoil heap. With distance from the heap, the share of mobile forms decreases in 2 - 2.5 times. The content of water-soluble forms of heavy metals increases with depth in the most remote soils from the spoil heap. In the course of calculations of the total coefficient of soil pollution, it follows that the soils have excessively dangerous and hazardous level of pollution. Conclusion. Thus, in the course of studies of the spoil heap of the mine «Tsentralnaya» of the Karabash ore district, the direct influence of the dumping mass on the contamination of soils of the surrounding areas by migration of heavy metals from the surface of the spoil heap by hydro-genic runoff was established. As a result, rock heterogeneities, less soluble, partially restrain the oxidation rate, forming reducing conditions. The elemental composition of the rocks showed a high content of heavy metals, making this waste rock a source of heavy metals to the surrounding environment. Resume. The instability and heterogeneity of the ongoing geochemical processes in the waste rock mass of the slag heap has been revealed, which leads to leaching of the rock mass slowly over time. Spreading of products of destruction of mineral mass of the spoil heap can be traced in soils up to 800 metres away. As a result of hydro-genic flows from the spoil heap, the soils, have a dangerous and extremely dangerous degree of contamination. As suggestions for practical application and direction of future research, the importance of this work can be noted, which can serve as a foundation for the study of such technogenic mineral formations with a view to their secondary utilization, as well as for determining the most appropriate methods of remediation of contaminated soils.