Environmental hazard assessment of the Uluk-Bar gold deposit (Southern Urals)

Abstract

Relevance. Due to the maximum allowable concentrations of heavy metals and metalloids exceeding in the surface waters of the Avzyan gold region, possible sources of toxic elements are determined, which is important for combating pollution in ore areas. Aim. To assess the environmental hazard of the Ulyuk–Bar gold deposit based on the chemical and mineralogical composition of the enclosing rocks and the mobility of toxic elements in them. Materials and methods. The chemical composition of rocks was determined by X-ray fluorescence and atomic emission with inductive plasma methods, as well as using methods of classical analytical chemistry. The mineralogical composition of rocks is determined by X-ray phase analysis, the composition of minerals and the content of elements-impurities in them – by scanning electron microscopy. Preliminary assessment of the ecological condition of the deposit was carried out according to the indicator of the potential toxicity of elements and the indicator of the potential environmental hazard of minerals. The forecast of drainage water composition and mobility of elements was carried out using peroxide experiment and atomic absorption analysis data, final acid-alkali conditions – by calculating acid neutralizing and acid producing potentials. Results and discussion. High and very high indicators of potential toxicity and hazard were identified. The main potential hazard is arsenic, chromium, cobalt, nickel, copper, palladium, antimony and etc. The high mobility of magnesium, calcium, chromium, antimony, rubidium, barium, strontium, sulfur was established. Many of them represent a real environmental hazard. Silicon, aluminum, titanium, sodium, potassium, iron, manganese, phosphorus, copper, zinc, nickel, arsenic, lanthanum, cerium, yttrium, vanadium, cobalt, niobium, zirconium and molybdenum in rocks are immobile or lack of mobility. Sulfides are mainly involved in contamination with toxic elements. The rocks of the deposit are characterized by a high acid neutralizing potential. The drainage water conditions are defined as neutral-alkaline. Conclusion. The Ulyuk-Bar deposit has a high potential hazard, which is primarily due to the mineralogical and geochemical features of the ores and the enclosing rocks. Sulfides are the main threat due to the content of large amounts of toxic metals and metalloids in them. At the same time, the rocks of the deposit, unchanged by hypergenic processes, contain a significant amount of carbonate minerals, which causes high acid neutralizing and low acid producing properties of rocks that prevent the rapid dissolution of sulfide minerals. The conducted research combines information to identify environmental problems related to the geological and geochemical features of the deposit and facilitates the selection of a suitable combination of methods to minimize environmental risks and impacts.