The V.S. Sobolev Institute of Geology and Mineralogy of the Russian Academy of Sciences (IGM SB RAS), Russia
Title: Geochemical modeling in solving some environmental problems: pollution of mining regions, radioactive wastes storage
Biography: Olga S Naymushina
This paper has two parts. The first briefly describes geochemical and geophysical investigations at the territory of gold tailings impoundment produced with cyanidation by the abandoned Komsomolsk Gold Extraction Plant, KGEP (Kemerovo region, Russia). The second part reflects on our recent studies in the area of the low-level waste repository of the Novosibirsk Plant of Chemical Concentrates, NPCC (Novosibirsk, Russia). The relatively low sulfide content in the Komsomolsk tailings result in a low acid producing potential (AP). The situation is complicated by the displaced Berikul tailings of the former Berikul GEP. In these tailings, the sulfide content is 25%, they have high AP and the formation of acidic surface ponds (pH ∼2) with high concentrations of metals and metalloids (as up to 4.1 g/L). Based on electrical resistivity tomography, the uncontrolled leakage of acidic and highly mineralized solutions through a natural geological fault into groundwater horizons was revealed. Uranium contamination of groundwater is prevalent worldwide because of uranium extraction for nuclear energy and weapons. An experimental modeling has been carried out to convert U(VI) to species with low solubility via metabolic process. The removal of nitrates, sulfates and U(VI) reduction due to the stimulated microbiological activity was proved. Within 13 days after the start of serum injections, reducing conditions was indicated and the sharp decrease in nitrate concentrations was observed. Sulfate reduction was established approximately 50 days later as indicated by the increase in sulfide concentrations. Model calculations by computer code “HCh” have approved precipitation of β-UO2.25(s) at Eh+115 mV and precipitation of UO2(s) after the fall of Eh to -397 mV. The developed model can be used as a starting point of assessment of the redox sensitive elements behavior in the process of bioremediation.