Geochemical Effects of Reclamation at Disturbed and Polluted Mine Sites

The extraction of mineral resources results in a gigantic increase in the volume of overburden and host rocks mined and stored on the Earth's surface. Mine sites are constantly disturbed and polluted; the major changes are found in the soil cover, affecting the migration and accumulation of chemical elements; the cycles of nutrients, which are important for the development of biocenosis, are altered. The study on concentrations of pollutants in the Technosols revealed that they are determined to a greater extent by anthropogenic impact and subsequent possible remediation than by parent rocks. Soil sampling was conducted in the changing climatic zones of Russia where the impact is experienced both directly and indirectly by the water and air environments and, ultimately, this leads to economic losses and poses a danger to human health. The studies of the soil samples were performed using the equipment of the Common Use Centre of the Saint Petersburg Mining University. Reclamation of the studied mine sites was regulated by law to ensure environmental sustainability, that is, to preserve the possibility of land use for future generations, but its methods and ultimate goals varied significantly. Geological, geomorphological, hydrological, climatic, and soil characteristics of the site, as well as socio-economic conditions, determined the tasks of reclamation and the resulting new ecosystems. We analyzed that the most common uses of the restored landscapes include afforestation; if the soil cover complies with sanitary and hygienic standards, it is possible to start an agricultural business or create a reservoir for household or fishery purposes; land can be used for construction and recreation; in some situations, waste disposal is possible. Ecosystems that are restored or completely constructed differ greatly not only in their functions but also in geochemical conditions, on which the prospects for the return of disturbed and contaminated lands to an acceptable state largely depend. In this regard, the study goal was to identify general geochemical patterns inherent in reclaimed landscapes in different geographic zones, since the geochemical transformation of restored ecosystems depends on several natural and technogenic factors. The research outcomes indicate that the oxidation-reduction and alkaline-acid milieu, water and temperature regimes, sorption capacity, and other landscape-geochemical conditions are being ambiguously transformed in new ecosystems and can be derived from both natural conditions and the measures taken to eliminate damage. Concentrations of Pb, Zn, Ba, and Cu were found exceeding the average contents in the Earth's soils tens and even hundreds of times. We discussed the case within the framework of the Working Group on Land Reclamation, Environmental Protection, and Best Available Techniques (BAT) in Mining, and recommended reusing the studied mine sites with particular attention paid to phytoextraction, construction of geochemical barriers, and thermal desorption.