Assessment of the hazard posed by meltwater to surface watercourses in the Norilsk industrial area

The snow cover of the Norilsk industrial area is a subject of monitoring. Given the subsequent inflow of melting water into water bodies used for economic and drinking water supply (the Norilsk River) and those with fishery significance (the Norilsk, Doldykan, Ambarna, and Yergalah rivers), the contained chemicals pose a danger to aquatic fauna and humans. The study focused on the chemical composition of the snow cover (44 sampling points, 4 of which are background) in the Norilsk industrial area outside the boundaries of industrial sites. The presence of cations (ammonium, potassium, sodium, strontium, lithium, barium, calcium, magnesium), anions (chlorides, nitrites, nitrates, sulfates, fluorides, phosphates, bicarbonates), and water-soluble forms of heavy metals (mercury, arsenic, lead, cadmium, copper, nickel, zinc) was established. A total of 22 substances were identified. The identification of the ionic composition was carried out in accordance with the current Federal list of methods. For each ion, the value of the actual concentration exceeding the MPC standards established for bodies of water of respective use was calculated. The assessment of snow cover pollution was conducted based on the calculated values of the water pollution index (WPI), the total chemical pollution indicator (TCP-10), and the maximum pollution coefficient (MPC). A multi-component chemical composition of the snow cover was established, revealing between 9 to 17 ions. According to the WPI value, melting waters are characterized as very clean (59% of samples) and clean (41% of samples) and are not dangerous when entering water bodies for both types of water use. According to the TCP-10 indicator, only 2 sampling points, localized in the impact zone of metallurgical facilities, can be classified as an ecological disaster zone (fishery water bodies). Based on the actual content of all identified substances, melting waters in more than half of the cases (59% of samples) could be potentially dangerous for fishery water bodies. Given that the identified concentrations of copper and nickel have the highest multiples exceeding the MPC, both elements form the basis of the natural geochemical background, emphasizing the need to improve the regulation of their content in water bodies of various uses. The results obtained can significantly supplement the regional environmental monitoring program and serve as a basis for developing measures for the disposal of contaminated snow cover with potentially hazardous characteristics.