Environmental Regulation of the Content of Chemical Elements in Soils in the Impact Zone of an Aluminum Smelter in Siberia

Abstract— Detailed studies of snow and soil pollution in the impact zone of the Irkutsk Aluminum Smelter were conducted from 1996 to 2025. Chemical and analytical work was performed at the Sochava Institute of Geology, Siberian Branch of the Russian Academy of Sciences. The main air and soil pollutants (F, Al, Na, Ba, Pb, Cu, Ni, etc.), as well as their amounts and distribution areas were described. The study revealed that the maximal fluoride concentration in meltwater within an area to 1 km from the aluminum smelter reached 66 mg/dm3. The relationship between technogenic pollution of soil and snow cover was assessed, and its impact on certain soil parameters (forest litter thickness, cellulose destruction rate, biological activity, content of essential plant nutrients in soils, and phytotoxicity) was identified. Environmental standards for technogenic loads were established based on significant and sensitive soil parameters, taking into account regional conditions. The maximal level of technogenic load was recorded by determining critical points on the load–effect curve. The dose–effect ratio values may be used to determine (ecologically) maximal permissible concentrations (eMPC) and maximal unacceptable concentrations (eMUC) of potentially toxic elements in soil. The lower critical point is considered the maximal permissible concentration (eMPC) of a chemical element, at which changes in soil parameters are still reversible. Unacceptable concentrations (eMUC) of chemical elements are defined by the upper critical point, at which changes in soil parameters are no longer reversible. Fluoride, aluminum, and sodium total concentrations were 0.66 and 0.84 g/kg, 82 and 93 g/kg, and 22 and 34 g/kg, respectively, for the upper (eMPC) and lower (eMUC) limits. The maximal permissible and unacceptable concentrations in soil were 0.22 and 0.58 g/kg for acid-soluble F; 11 and 24 g/kg for Al; and 0.25 and 0.48 g/kg for Na. Taking into account the existing amount of emissions of the smelter, according to our calculations (based on the snow cover analysis) and to the established permissible loads on soils, the load for various elements should be reduced up to two times.